CN110324089B

CN110324089B - Signal transmission method of passive optical network system and related equipment

Info

Publication number: CN110324089B
Application number: CN201810296529.0A
Authority: CN
Inventors: 姚殊畅; 方李明; 叶志成
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-03-30
Filing date: 2018-03-30
Publication date: 2021-03-30
Anticipated expiration: 2038-03-30
Also published as: CN110324089A; WO2019184819A1

Abstract

The embodiment of the application discloses a signal transmission method of a passive optical network system, which is used for solving the problem of difficult wavelength management and reducing the cost of devices. The method comprises the following steps: an Optical Line Terminal (OLT) generates a downlink frequency division multiplexing electrical signal corresponding to a plurality of downlink sub-bands, wherein each downlink sub-band in the plurality of downlink sub-bands is not overlapped on a frequency domain, and each downlink sub-band corresponds to a group of Optical Network Units (ONU); the OLT loads the downlink frequency division multiplexing electrical signal to the OLT to emit light to obtain a downlink frequency division multiplexing optical signal; and the OLT sends the downlink frequency division multiplexing optical signal, so that the ONU, the frequency of which is the first frequency, of the ONU intrinsic light obtains a downlink sub-band signal corresponding to the ONU from the downlink frequency division multiplexing optical signal, wherein the first frequency corresponds to one downlink sub-band in the plurality of downlink sub-bands.

Description

Signal transmission method of passive optical network system and related equipment

Technical Field

The present application relates to the field of communications technologies, and in particular, to a signal transmission method and related device for a passive optical network system.

Background

A Passive Optical Network (PON) system is a solution for the last kilometer of an optical fiber transmission network, and a large amount of optical fiber resources can be saved by sharing a trunk optical fiber, so that the PON system is suitable for an optical network system with a large number of end branches. In recent years, with the increase of bandwidth demand, PON systems are continuously updated. Currently, a large number of Gbit PON systems are deployed, 10Gbit PON systems are deployed at the beginning, and with the development of high bandwidth services such as 4k Television (TV), Virtual Reality (VR), etc., the next generation 100Gbit capacity PON system has also been listed as a discussion line of two major standards organizations of Institute of Electrical and Electronics Engineers (IEEE) and International Telecommunications Union (ITU).

Before the NGPON2 standard, capacity expansion of a PON system is realized by increasing a single-wavelength signal rate, and interconnection between an Optical Line Terminal (OLT) and a user side network unit (ONU) is realized by using a Time Division Multiplexing (TDM) method. Therefore, each time the PON system rate is increased, high requirements are imposed on the system power budget, the bandwidth of the optoelectronic device, and the cost.

In the prior art, a PON system generally adopts a Wavelength Division Multiplexing (WDM) mode, and realizes the intercommunication between an OLT and an ONU in an end-to-end (peer-to-peer) manner, as shown in fig. 1, a plurality of lasers are arranged on an OLT side, and perform signal modulation for each laser, so that each laser emits optical carrier signals with different wavelengths, and a transmitting end side combines the optical carrier signals together through the WDM and couples the optical carrier signals to the same optical fiber in an optical line for transmission; the optical carrier signals of each wavelength are separated at the receiving end through a branching module (demultiplexer), and then are received and analyzed by an ONU receiver.

In this method, the OLT needs to modulate carrier signals with different wavelengths for each ONU, and for a PON system with a large number of ONUs, a large number of lasers need to be provided to modulate a large number of carrier signals with different wavelengths, which is costly and difficult to manage the wavelengths.

Disclosure of Invention

The embodiment of the application provides a signal transmission method of a PON system and related equipment, which are used for reducing equipment cost.

In view of this, a first aspect of the present application provides a signal transmission method for a PON system, where the method includes: the optical line terminal generates downlink frequency division multiplexing electrical signals corresponding to a plurality of downlink sub-bands, loads the electrical signals onto optical line terminal emission light to obtain frequency division multiplexing signals on an optical domain, namely downlink frequency division multiplexing optical signals, and finally emits the downlink frequency division multiplexing optical signals, so that an optical network unit with an optical network unit intrinsic optical frequency being a first frequency can obtain the downlink sub-band signals corresponding to the optical network unit from the downlink frequency division multiplexing optical signals.

It should be noted that, in the multiple downlink sub-bands corresponding to the downlink frequency division multiplexing electrical signal in the present implementation, each downlink sub-band is not overlapped in the frequency domain, and each downlink sub-band corresponds to one group of ONUs. The optical network unit may obtain the corresponding downlink sub-band signal from the downlink frequency division multiplexing optical signal, where the intrinsic optical frequency of the optical network unit needs to correspond to one of the downlink sub-bands, that is, the first frequency corresponds to one of the downlink sub-bands in the plurality of downlink sub-bands.

In this implementation, the downlink frequency division multiplexing electrical signal is generated according to downlink signals on a plurality of downlink sub-bands that do not overlap in the frequency domain, and each downlink sub-band corresponds to one group of ONUs, that is, the frequency bands occupied by the downlink signals received by different groups of ONUs do not overlap, and there is no interference, so that the ONUs can accurately receive the downlink signals corresponding to themselves, and the communication quality of the user side is improved. In addition, the frequency division multiplexing signal is modulated in the electric domain, and the frequency division multiplexing signal is loaded into the emitted light and transmitted to the ONU, so that the OLT can modulate the sub-band signals corresponding to different ONUs by only one laser, does not need to be provided with a plurality of lasers, and does not need to emit a plurality of optical signals with different wavelengths, thereby solving the problem of difficult wavelength management and reducing the device cost.

With reference to the first aspect of the present application, in a first implementation manner of the first aspect of the present application, the optical line terminal may generate downlink frequency division multiplexing electrical signals corresponding to a plurality of sub-bands by: the optical line terminal generates baseband signals corresponding to each optical network unit, shapes the baseband signals through a low-pass filter to obtain target baseband signals corresponding to each optical line terminal, then performs frequency shift on the target baseband signals corresponding to the optical network units to obtain downlink sub-band signals corresponding to the optical network units, and finally combines the downlink sub-band signals corresponding to each optical network unit to obtain downlink frequency division multiplexing electrical signals.

In this implementation, the optical line terminal shapes the baseband signal through the low-pass filter, and removes unnecessary frequency band signals, so that multiple digital frequency bands corresponding to the downlink frequency division multiplexing electrical signal are not overlapped in the frequency domain, and interference between downlink sub-band signals corresponding to each ONU is avoided.

With reference to the first aspect of the present application or the first implementation manner of the first aspect, in a second implementation manner of the first aspect of the present application, before the optical line terminal generates the downlink frequency division multiplexing electrical signals corresponding to a plurality of downlink sub-bands, the downlink sub-bands may be allocated to the optical network unit, specifically by: the optical line terminal determines a target sub-band which is in an idle state or is not fully registered in a downlink sub-band corresponding to the PON system, then sends an inquiry message on the target sub-band, and suspends sending signals on sub-bands other than the target sub-band, so that the optical network unit can determine a first frequency according to the inquiry message on the target sub-band, where the target sub-band is the downlink sub-band allocated to the optical network unit by the optical line terminal, that is, the downlink sub-band of the optical network unit corresponds to the target sub-band.

The implementation mode provides a specific mode for distributing the downlink sub-band for the optical network unit to enable the optical network unit to determine the frequency of the intrinsic light, and the realizability of the scheme is improved.

With reference to the first aspect of the present application, in a third implementation manner of the first aspect of the present application, before generating a downlink frequency division multiplexing electrical signal corresponding to a plurality of downlink sub-bands, an optical line terminal may determine an uplink sub-band used for uplink transmission of a PON system and an uplink sub-band used for downlink transmission of the PON system, that is, divide the uplink sub-band and the downlink sub-band, and may specifically divide the uplink sub-band and the downlink sub-band by: the optical line terminal allocates the first sub-band as an uplink sub-band to an optical network unit in the PON system, and allocates the second sub-band as a downlink sub-band to the optical network unit in the PON system, where the first sub-band and the second sub-band are adjacent in a frequency domain, that is, for any two adjacent sub-bands in the frequency domain, the optical line terminal will use one of the two sub-bands as the uplink sub-band and the other as the uplink sub-band.

The implementation mode distributes the sub-frequency bands in a staggered manner, and can effectively avoid interference of the reflection signals of different sub-frequency bands on the sub-frequency band information of the uplink optical signal and the downlink optical signal.

With reference to the first aspect of the present application, and any one implementation manner of the first to third implementation manners of the first aspect, in a fourth implementation manner of the first aspect of the present application, the optical line terminal may further perform the following operations: the optical line terminal obtains each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through the optical line terminal intrinsic light of a second frequency, wherein the second frequency corresponds to the center frequency of the uplink frequency division multiplexing optical signal, and the uplink frequency division multiplexing optical signal is a signal obtained after the uplink sub-band optical signals are combined.

In this implementation manner, the optical line terminal may receive the uplink signal sent by the optical network unit in a coherent detection manner, that is, the optical line terminal may obtain the uplink signal sent by each optical network unit only by aligning the intrinsic light to the center frequency of the uplink frequency division multiplexing optical signal, and is simple to operate and low in cost.

With reference to the fourth implementation manner of the first aspect of the present application, in a fifth implementation manner of the first aspect of the present application, the optical line terminal emission light and the optical line terminal intrinsic light are light emitted by the same light source.

In the implementation mode, the receiver and the transmitter of the optical line terminal share one light source, so that the equipment cost is effectively reduced, and the effective alignment of the intrinsic optical frequency is ensured.

A second aspect of the present application provides another signal transmission method for a PON system, including: the optical network unit sets the frequency of the optical network unit intrinsic light to be a first frequency, the first frequency corresponds to a target sub-band, through the optical network unit intrinsic light of the first frequency, the optical network unit obtains a downlink sub-band signal corresponding to the optical network unit from a downlink frequency division multiplexing optical signal, the downlink frequency division multiplexing optical signal is obtained by loading a downlink frequency division multiplexing electrical signal corresponding to a plurality of downlink sub-bands onto the optical line terminal intrinsic light by an optical line terminal, each sub-band in the plurality of downlink sub-bands corresponding to the downlink frequency division multiplexing electrical signal is not overlapped on a frequency domain, and the target sub-band is one of the plurality of downlink sub-bands.

With reference to the second aspect of the present application, in a first implementation manner of the second aspect of the present application, before the optical network unit sets the frequency of the intrinsic light of the optical network unit to the first frequency, the optical network unit may determine the first frequency by: the optical network unit adjusts the frequency of the optical network unit intrinsic light, and for the optical network unit intrinsic light of each frequency, coherent detection is performed on the optical network unit intrinsic light and an inquiry message sent by the optical line terminal in a target sub-band, coherent detection output power corresponding to each frequency is determined, and then the frequency corresponding to the maximum value in the coherent detection output power is determined as the first frequency.

The implementation mode provides a specific mode for determining the frequency of the intrinsic light for the optical network unit, and the realizability of the scheme is improved.

With reference to the second aspect or the first implementation manner of the second aspect, in a second implementation manner of the second aspect of the present application, the optical network unit may further perform the following operations: the optical network unit performs frequency shift on the baseband signal to obtain an uplink sub-band electrical signal corresponding to the optical network unit, loads the uplink sub-band electrical signal onto the optical network unit to obtain an uplink sub-band optical signal, and then sends the uplink sub-band optical signal, so that the passive combiner in the PON system can combine the uplink sub-band optical signal with uplink sub-band optical signals sent by other optical network units in the PON system to obtain an uplink frequency division multiplexing optical signal, and the optical line terminal can obtain each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through the optical line terminal intrinsic light of the second frequency.

It should be understood that, in this implementation, the uplink sub-band electrical signal corresponding to the optical network unit corresponds to the uplink sub-band allocated to the optical network unit by the optical line terminal, and the second frequency corresponds to the center frequency of the uplink frequency division multiplexing optical signal.

In this implementation, the central frequency of the uplink frequency division multiplexing optical signal is equal to the sum of the frequency of the laser of the optical network unit and the central frequency of the electrical domain radio frequency signal.

With reference to the second implementation manner of the second aspect of the present application, in a third implementation manner of the second aspect of the present application, the optical network unit may specifically perform radio frequency modulation in an electrical domain to compensate for instability of a laser, where the center frequency of the uplink sub-band electrical signal and the uplink sub-band allocated to the optical network unit by the optical line terminal correspond to specifically: center frequency f of up sub-band electric signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated by the olt to the onu, f₁And delta f is a frequency offset value calculated by a frequency offset estimation algorithm according to the downlink sub-band electric signal, wherein the frequency is the frequency of light emitted by the optical network unit.

This implementation provides a concrete way of compensating the laser frequency, has improved the realizability of scheme.

With reference to the second aspect of the present application, or any one implementation manner of the first to third implementation manners of the second aspect, in a fourth implementation manner of the second aspect of the present application, the optical network unit emission light and the optical network unit intrinsic light are lights emitted by the same unit in the optical network unit.

In the implementation mode, the receiver and the transmitter of the optical network unit share one light source, so that the equipment cost is effectively reduced, the effective alignment of the intrinsic light frequency is ensured, and the crosstalk between frequency bands is avoided.

The third aspect of the present application further provides a signal transmission method for a PON system, where the method includes: and the optical line terminal acquires each uplink sub-band electric signal corresponding to the uplink frequency division multiplexing optical signal through the optical line terminal intrinsic light with the second frequency.

It should be understood that, in this implementation, the second frequency corresponds to a center frequency of the uplink ofdm optical signal, and the uplink ofdm optical signal is a signal obtained by combining a plurality of uplink sub-band optical signals.

In this implementation manner, the optical line terminal can obtain the uplink signal sent by each optical network unit only by aligning the intrinsic light to the center frequency of the uplink frequency division multiplexing optical signal, and is simple to operate and low in cost.

With reference to the third aspect of the present application, in a first implementation manner of the third aspect of the present application, before acquiring each uplink sub-band electrical signal corresponding to an uplink frequency division multiplexing optical signal, an optical line terminal may determine an uplink sub-band used for uplink transmission of a PON system and an uplink sub-band used for downlink transmission of the PON system, that is, divide the uplink sub-band and the downlink sub-band, and may specifically divide the uplink sub-band and the downlink sub-band by: the optical line terminal allocates the first sub-band as an uplink sub-band to an optical network unit in the PON system, and allocates the second sub-band as a downlink sub-band to the optical network unit in the PON system, where the first sub-band and the second sub-band are adjacent in a frequency domain, that is, for any two adjacent sub-bands in the frequency domain, the optical line terminal will use one of the two sub-bands as the uplink sub-band and the other as the uplink sub-band.

With reference to the third aspect or the first implementation manner of the third aspect, in a second implementation manner of the third aspect, the optical line terminal may allocate a downlink sub-band to an optical network unit in the PON system by: the optical line terminal determines a target sub-band which is in an idle state or is not fully registered in a downstream sub-band (i.e. a first frequency band) corresponding to the PON system, then sends an inquiry message on the target sub-band, and suspends sending signals on sub-bands other than the target sub-band, so that the optical network unit can determine the first frequency according to the inquiry message on the target sub-band, and the target sub-band is the downstream sub-band allocated to the optical network unit by the optical line terminal, i.e. the downstream sub-band of the optical network unit corresponds to the target sub-band.

A fourth aspect of the present application provides a signal transmission method for a PON system, where the method includes: the optical network unit performs frequency shift on the baseband signal to obtain an uplink sub-band electrical signal corresponding to the optical network unit, loads the uplink sub-band electrical signal onto the optical network unit to obtain an uplink sub-band optical signal, and then sends the uplink sub-band optical signal, so that the passive combiner in the PON system can combine the uplink sub-band optical signal with uplink sub-band optical signals sent by other optical network units in the PON system to obtain an uplink frequency division multiplexing optical signal, and the optical line terminal can obtain each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through the optical line terminal intrinsic light of the second frequency.

With reference to the fourth aspect of the present application, in a first implementation manner of the fourth aspect, the optical network unit may specifically perform radio frequency modulation in an electrical domain to compensate for instability of a laser, where the center frequency of the uplink sub-band electrical signal and the uplink sub-band allocated to the optical network unit by the optical line terminal correspond to specifically refer to: center frequency f of up sub-band electric signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated by the olt to the onu, f₁And delta f is a frequency offset value calculated by a frequency offset estimation algorithm according to the downlink sub-band electric signal, wherein the frequency is the frequency of light emitted by the optical network unit.

With reference to the fourth aspect of the present application or the first implementation manner of the fourth aspect, in a second implementation manner of the fourth aspect of the present application, before the optical network unit performs frequency shift on the baseband signal to obtain the uplink sub-band electrical signal corresponding to the optical network unit, a downlink sub-band allocated to the optical network unit by the optical line terminal and a frequency of intrinsic light of the optical network unit may be determined, specifically, the following manners are adopted: the optical network unit adjusts the frequency of the optical network unit intrinsic light, and for the optical network unit intrinsic light of each frequency, coherent detection is performed on the optical network unit intrinsic light and an inquiry message sent by the optical line terminal in a target sub-band, coherent detection output power corresponding to each frequency is determined, and then the frequency corresponding to the maximum value in the coherent detection output power is determined as the first frequency.

A fifth aspect of the present application provides an optical line terminal, including:

the device comprises a generating module, a receiving module and a processing module, wherein the generating module is used for generating downlink frequency division multiplexing electric signals corresponding to a plurality of downlink sub-bands, each downlink sub-band in the plurality of downlink sub-bands is not overlapped on a frequency domain, and each downlink sub-band corresponds to a group of Optical Network Units (ONU);

the loading module is used for loading the downlink frequency division multiplexing electric signal to the OLT emitted light to obtain a downlink frequency division multiplexing optical signal;

and the sending module is used for sending the downlink frequency division multiplexing optical signal, so that the ONU with the frequency of the ONU intrinsic light as the first frequency obtains a downlink sub-band signal corresponding to the ONU from the downlink frequency division multiplexing optical signal, and the first frequency corresponds to one downlink sub-band in the plurality of downlink sub-bands.

With reference to the fifth aspect of the present application, in a first implementation manner of the fifth aspect of the present application, the generating module includes:

the generating submodule is used for generating baseband signals corresponding to the ONUs;

the shaping submodule is used for shaping the baseband signals through a low-pass filter to obtain target baseband signals corresponding to each ONU;

the frequency shift sub-module is used for carrying out frequency shift on a target baseband signal corresponding to each ONU so as to obtain a downlink sub-band signal corresponding to the ONU on a downlink sub-band corresponding to the ONU;

and the merging submodule is used for merging the downlink sub-band signals corresponding to the ONUs to obtain a downlink frequency division multiplexing electric signal.

With reference to the fifth aspect or the first implementation manner of the fifth aspect, in a second implementation manner of the fifth aspect of the present application, the optical line terminal further includes:

a determining module, configured to determine a target sub-band that is in an idle state or is not fully registered in a downlink sub-band corresponding to the PON system, where the downlink sub-band corresponding to the PON system is not overlapped in a frequency domain;

the sending module is further configured to send an inquiry message on the target sub-band, and suspend sending signals on other frequency bands except the target sub-band, so that the ONU determines the first frequency according to the inquiry message, and the target sub-band is a downstream sub-band corresponding to the ONU.

With reference to the fifth aspect of the present application, and any one implementation manner of the first and second implementation manners of the fifth aspect, in a third implementation manner of the third aspect of the present application, the optical line terminal further includes:

and the allocation module is used for allocating the first sub-band as an uplink sub-band to the ONUs in the PON system, and allocating the second sub-band as a downlink sub-band to the ONUs in the PON system, wherein the first sub-band and the second sub-band are adjacent to each other in the frequency domain.

With reference to the fifth aspect of the present application, and any one implementation manner of the first to third implementation manners of the fifth aspect, in a fourth implementation manner of the fifth aspect of the present application, the optical line terminal further includes:

and the obtaining module is configured to obtain each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, where the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal, and the uplink frequency division multiplexing optical signal is a signal obtained after combining multiple uplink sub-band optical signals.

With reference to the fourth implementation manner of the fifth aspect of the present application, in a fifth implementation manner of the fifth aspect of the present application, the optical line terminal emission light and the intrinsic light of the optical line terminal are light emitted by the same light source.

A sixth aspect of the present application provides an optical network unit, including:

the device comprises a setting module, a first frequency module and a second frequency module, wherein the setting module is used for setting the frequency of the ONU intrinsic light to be a first frequency, and the first frequency corresponds to a target sub-band;

the receiving module is configured to obtain a downlink sub-band signal corresponding to the ONU from a downlink frequency division multiplexing optical signal through the ONU intrinsic light of the first frequency, where the downlink frequency division multiplexing optical signal is obtained by the OLT loading a downlink frequency division multiplexing electrical signal corresponding to a plurality of sub-bands onto light emitted by the OLT, and each of the plurality of downlink sub-bands is not overlapped in a frequency domain, and includes a target sub-band.

With reference to the sixth aspect of the present application, in a first implementation manner of the sixth aspect of the present application, the optical network unit further includes:

the adjusting module is used for adjusting the frequency of the ONU intrinsic light, carrying out coherent detection on the ONU intrinsic light and an inquiry message sent by the OLT in a target sub-band aiming at the ONU intrinsic light of each frequency, and determining coherent detection output power corresponding to each frequency;

and the determining module is used for determining the frequency corresponding to the maximum value in the coherent detection output power as the first frequency.

With reference to the sixth aspect of the present application or the first implementation manner of the sixth aspect, in a second implementation manner of the sixth aspect of the present application, the optical network unit further includes:

the frequency shift module is used for carrying out frequency shift on the baseband signal to obtain an uplink sub-band electric signal corresponding to the ONU, and the central frequency of the uplink sub-band electric signal corresponds to an uplink sub-band allocated to the ONU by the OLT;

the loading module is used for loading the uplink sub-band electric signal to the ONU emitted light to obtain an uplink sub-band optical signal;

the transmitting module is configured to transmit an uplink sub-band optical signal corresponding to the ONU, so that the passive combiner combines the sub-band optical signal corresponding to the ONU with uplink sub-band optical signals transmitted by other ONUs in the PON system to obtain an uplink frequency division multiplexing optical signal, and the OLT acquires each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, where the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal.

With reference to the second implementation manner of the sixth aspect of the present application, in a third implementation manner of the sixth aspect of the present application, the corresponding of the center frequency of the uplink sub-band electrical signal and the uplink sub-band allocated to the ONU by the OLT includes: center frequency f of up sub-band electric signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated by the OLT to the ONU, f₁For the frequency of the light emitted by the ONU, Δ f is a frequency offset value calculated by a frequency offset estimation algorithm according to the downlink sub-band electrical signal.

With reference to the second or third implementation manner of the sixth aspect of the present application, in a fourth implementation manner of the sixth aspect of the present application, the ONU-emitted light and the ONU-intrinsic light are light emitted by a same light source in the ONU.

A seventh aspect of the present application provides an optical line terminal, including:

and the acquisition module is used for acquiring each uplink sub-band electric signal corresponding to the uplink frequency division multiplexing optical signal through the optical line terminal intrinsic light of the second frequency.

With reference to the seventh aspect of the present application, in a first implementation manner of the seventh aspect of the present application, the optical line terminal further includes:

the allocation module is configured to allocate the first sub-band as an uplink sub-band to an optical network unit in the PON system, and allocate the second sub-band as a downlink sub-band to the optical network unit in the PON system, where the first sub-band and the second sub-band are adjacent in a frequency domain, that is, for any two adjacent sub-bands in the frequency domain, the optical line terminal will use one of the two sub-bands as the uplink sub-band and use the other as the uplink sub-band.

With reference to the seventh aspect or the first implementation manner of the seventh aspect of the present application, in a second implementation manner of the seventh aspect of the present application, the allocating module includes:

a determining submodule, configured to determine a target sub-band in an idle state or not fully registered in a downlink sub-band (i.e., a first frequency band) corresponding to the PON system;

and the sending sub-module is used for sending the inquiry message on the target sub-band and suspending sending signals on other sub-bands except the target sub-band, so that the optical network unit can determine the first frequency according to the inquiry message on the target sub-band, and the target sub-band is a downlink sub-band which is allocated to the optical network unit by the optical line terminal, namely the downlink sub-band of the optical network unit corresponds to the target sub-band.

An eighth aspect of the present application provides an optical network unit, including:

the frequency shift module is used for carrying out frequency shift on the baseband signal to obtain an uplink sub-band electric signal corresponding to the optical network unit;

the loading module is used for loading the uplink sub-band electric signal to the optical network unit to obtain an uplink sub-band optical signal;

a sending module, configured to send the uplink sub-band optical signal, so that a passive combiner in the PON system can combine the uplink sub-band optical signal with uplink sub-band optical signals sent by other optical network units in the PON system to obtain an uplink frequency division multiplexing optical signal, and the optical line terminal can obtain each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through the optical line terminal intrinsic light of the second frequency.

With reference to the eighth aspect of the present application, in a first implementation manner of the eighth aspect, the correspondence between the center frequency of the uplink sub-band electrical signal and the uplink sub-band allocated by the optical line terminal to the optical network unit specifically means: center frequency f of up sub-band electric signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated by the olt to the onu, f₁And delta f is a frequency offset value calculated by a frequency offset estimation algorithm according to the downlink sub-band electric signal, wherein the frequency is the frequency of light emitted by the optical network unit.

With reference to the eighth aspect or the first implementation manner of the eighth aspect of the present application, in a second implementation manner of the eighth aspect of the present application, the optical network unit further includes:

the adjusting module is used for adjusting the frequency of the intrinsic light of the optical network unit;

and the determining module is used for carrying out coherent detection on the optical network unit intrinsic light and the inquiry message sent by the optical line terminal in the target sub-band aiming at the optical network unit intrinsic light of each frequency, determining coherent detection output power corresponding to each frequency, and determining the frequency corresponding to the maximum value in the coherent detection output power as the first frequency.

A ninth aspect of the present application provides an optical line terminal, including: a processor, a memory, a laser; wherein the laser is configured to emit an optical signal, the memory is configured to store a program, and the processor is configured to execute the program so that the OLT performs at least the following steps: and finally, the downlink frequency division multiplexing optical signal is transmitted out, so that the optical network unit with the optical network unit intrinsic optical frequency being the first frequency can obtain the downlink sub-band signal corresponding to the optical network unit from the downlink frequency division multiplexing optical signal.

With reference to the ninth aspect of the present application, in a first implementation manner of the ninth aspect of the present application, in the step of generating the downlink frequency division multiplexing electrical signals corresponding to a plurality of downlink sub-bands, the processor executes the program to make the OLT perform at least the following steps: generating baseband signals corresponding to each optical network unit, shaping the baseband signals respectively through a low-pass filter to obtain target baseband signals corresponding to each optical line terminal, then carrying out frequency shift on the target baseband signals corresponding to the optical network units to obtain downlink sub-band signals corresponding to the optical network units, and finally combining the downlink sub-band signals corresponding to the optical network units to obtain downlink frequency division multiplexing electrical signals.

With reference to the ninth aspect or the first implementation manner of the ninth aspect of the present application, in a second implementation manner of the ninth aspect of the present application, the processor executes the program to cause the OLT to further perform the following steps: determining a target sub-band which is in an idle state or is not fully registered in a downlink sub-band corresponding to the PON system, then sending an inquiry message on the target sub-band, and suspending sending signals on sub-bands other than the target sub-band, so that the optical network unit can determine the first frequency according to the inquiry message on the target sub-band, where the target sub-band is the downlink sub-band allocated to the optical network unit by the optical line terminal, that is, the downlink sub-band of the optical network unit corresponds to the target sub-band.

With reference to the ninth aspect of the present application, or any one of the first to second implementation manners of the ninth aspect, in a third implementation manner of the ninth aspect of the present application, the processor executes the program to make the OLT further perform the following steps: and allocating the first sub-band as an uplink sub-band to an optical network unit in the PON system, and allocating the second sub-band as a downlink sub-band to the optical network unit in the PON system, where the first sub-band and the second sub-band are adjacent in a frequency domain, that is, for any two adjacent sub-bands in the frequency domain, the optical line terminal will use one of the two sub-bands as the uplink sub-band and the other as the uplink sub-band.

With reference to the ninth aspect of the present application, or any one of the first to third implementation manners of the ninth aspect, in a fourth implementation manner of the ninth aspect of the present application, the processor executes the program to make the OLT further perform the following steps: and acquiring each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through the optical line terminal intrinsic light of a second frequency, wherein the second frequency corresponds to the center frequency of the uplink frequency division multiplexing optical signal, and the uplink frequency division multiplexing optical signal is a signal obtained by combining a plurality of uplink sub-band optical signals.

With reference to the fourth implementation manner of the ninth aspect of the present application, in a fifth implementation manner of the ninth aspect of the present application, the optical line terminal emission light and the optical line terminal intrinsic light are light emitted by the same light source.

A tenth aspect of the present application provides an optical network unit, including: a processor, a memory, a laser; wherein, the laser is used for sending out optical signal, and the memory is used for storing the procedure, and the treater is used for carrying out the procedure so that ONU carries out the following step at least: the method comprises the steps of setting the frequency of optical network unit intrinsic light as a first frequency, wherein the first frequency corresponds to a target sub-band, obtaining a downlink sub-band signal corresponding to an optical network unit from a downlink frequency division multiplexing optical signal through the optical network unit intrinsic light of the first frequency, wherein the downlink frequency division multiplexing optical signal is obtained by loading downlink frequency division multiplexing electrical signals corresponding to a plurality of downlink sub-bands onto the optical line terminal intrinsic light by an optical line terminal, each sub-band in the plurality of downlink sub-bands corresponding to the downlink frequency division multiplexing electrical signals is not overlapped on a frequency domain, and the target sub-band is one of the plurality of downlink sub-bands.

With reference to the tenth aspect of the present application, in a first implementation manner of the tenth aspect of the present application, the processor is configured to execute the program to cause the ONU to further perform the following steps: adjusting the frequency of the optical network unit intrinsic light, performing coherent detection on the optical network unit intrinsic light and an inquiry message sent by an optical line terminal in a target sub-band aiming at the optical network unit intrinsic light of each frequency, determining coherent detection output power corresponding to each frequency, and then determining the frequency corresponding to the maximum value in the coherent detection output power as the first frequency.

With reference to the tenth aspect or the first implementation manner of the tenth aspect, in a second implementation manner of the tenth aspect, the processor is configured to execute the program to cause the ONU to further perform the following steps: the method includes the steps of performing frequency shift on a baseband signal to obtain an uplink sub-band electrical signal corresponding to an optical network unit, loading the uplink sub-band electrical signal to optical transmission light of the optical network unit to obtain an uplink sub-band optical signal, and transmitting the uplink sub-band optical signal, so that a passive combiner in the PON system can combine the uplink sub-band optical signal with uplink sub-band optical signals sent by other optical network units in the PON system to obtain an uplink frequency division multiplexing optical signal, and an optical line terminal can obtain each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through optical line terminal intrinsic light of a second frequency.

With reference to the second implementation manner of the tenth aspect of the present application, in a third implementation manner of the tenth aspect of the present application, the correspondence between the center frequency of the uplink sub-band electrical signal and the uplink sub-band allocated by the optical line terminal to the optical network unit specifically means: center frequency f of up sub-band electric signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated by the olt to the onu, f₁And delta f is a frequency offset value calculated by a frequency offset estimation algorithm according to the downlink sub-band electric signal, wherein the frequency is the frequency of light emitted by the optical network unit.

With reference to the tenth aspect of the present application, or any one of the first to third implementation manners of the tenth aspect, in a fourth implementation manner of the tenth aspect of the present application, the optical network unit emission light and the optical network unit intrinsic light are lights emitted by the same unit in the optical network unit.

An eleventh aspect of the present application provides an optical line terminal comprising: a processor, a memory, a laser; wherein the laser is configured to emit an optical signal, the memory is configured to store a program, and the processor is configured to execute the program so that the OLT performs at least the following steps: obtaining each uplink sub-band electric signal corresponding to the uplink frequency division multiplexing optical signal through the optical line terminal intrinsic light of the second frequency

With reference to the eleventh aspect of the present application, in a first implementation manner of the eleventh aspect of the present application, the processor is configured to execute the program so that the OLT further performs the following steps: and allocating the first sub-band as an uplink sub-band to an optical network unit in the PON system, and allocating the second sub-band as a downlink sub-band to the optical network unit in the PON system, where the first sub-band and the second sub-band are adjacent in a frequency domain, that is, for any two adjacent sub-bands in the frequency domain, the optical line terminal will use one of the two sub-bands as the uplink sub-band and the other as the uplink sub-band.

In combination with the eleventh aspect of the present application or the first implementation manner of the eleventh aspect of the present application, in a second implementation manner of the eleventh aspect of the present application, the processor is configured to execute the program to cause the OLT to further perform the following steps: determining a target sub-band which is in an idle state or is not fully registered in a downstream sub-band (i.e. a first frequency band) corresponding to the PON system, then sending an inquiry message on the target sub-band, and suspending sending signals on sub-bands other than the target sub-band, so that the optical network unit can determine the first frequency according to the inquiry message on the target sub-band, where the target sub-band is the downstream sub-band allocated to the optical network unit by the optical line terminal, i.e. the downstream sub-band of the optical network unit corresponds to the target sub-band.

A twelfth aspect of the present application provides an optical network unit, including: a processor, a memory, a laser; wherein, the laser is used for sending out optical signal, and the memory is used for storing the procedure, and the treater is used for carrying out the procedure so that ONU carries out the following step at least: the method includes the steps of performing frequency shift on a baseband signal to obtain an uplink sub-band electrical signal corresponding to an optical network unit, loading the uplink sub-band electrical signal to optical transmission light of the optical network unit to obtain an uplink sub-band optical signal, and transmitting the uplink sub-band optical signal, so that a passive combiner in the PON system can combine the uplink sub-band optical signal with uplink sub-band optical signals sent by other optical network units in the PON system to obtain an uplink frequency division multiplexing optical signal, and an optical line terminal can obtain each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through optical line terminal intrinsic light of a second frequency.

With reference to the twelfth aspect of the present application, in a first implementation manner of the twelfth aspect, the correspondence between the center frequency of the uplink sub-band electrical signal and the uplink sub-band allocated by the optical line terminal to the optical network unit specifically means: center frequency f of up sub-band electric signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated by the olt to the onu, f₁And delta f is a frequency offset value calculated by a frequency offset estimation algorithm according to the downlink sub-band electric signal, wherein the frequency is the frequency of light emitted by the optical network unit.

With reference to the twelfth aspect of the present application or the first implementation manner of the twelfth aspect of the present application, in a second implementation manner of the twelfth aspect of the present application, the processor is configured to execute the program to cause the ONU to further perform the following steps: adjusting the frequency of the optical network unit intrinsic light, performing coherent detection on the optical network unit intrinsic light and an inquiry message sent by an optical line terminal in a target sub-band aiming at the optical network unit intrinsic light of each frequency, determining coherent detection output power corresponding to each frequency, and then determining the frequency corresponding to the maximum value in the coherent detection output power as the first frequency.

A thirteenth aspect of the present application provides a PON system comprising an optical line terminal according to any one of the implementation manners of the fifth aspect and an optical network unit according to any one of the implementation manners of the sixth aspect.

A fourteenth aspect of the present application provides a PON system, which includes the optical line terminal in any one of the implementations of the seventh aspect and the optical network unit in any one of the implementations of the eighth aspect.

A fifteenth aspect of the present application provides a computer storage medium having instructions stored thereon, which, when run on a computer, cause the computer to perform the method of any one of the implementations of the first aspect described above, or perform the method of any one of the implementations of the second aspect, or perform the method of any one of the implementations of the third aspect described above, or perform the method of any one of the implementations of the fourth aspect.

A sixteenth aspect of the present application provides a computer program product comprising instructions which, when run on a computer, causes the computer to perform the method of any one of the implementations of the first aspect described above, or perform the method of any one of the implementations of the second aspect, or perform the method of any one of the implementations of the third aspect described above, or perform the method of any one of the implementations of the fourth aspect.

According to the technical scheme, the embodiment of the application has the following advantages:

in this embodiment of the present application, the OLT may generate a plurality of downlink frequency division multiplexing electrical signals corresponding to downlink frequencies, load the downlink frequency division multiplexing electrical signals onto the OLT emitting light to obtain downlink frequency division multiplexing optical signals, and send the downlink frequency division multiplexing optical signals, and the ONU may obtain, by using the ONU intrinsic light of a first frequency through the coherent receiver, a downlink sub-band signal corresponding to the ONU from the downlink frequency division multiplexing optical signals, where the first frequency corresponds to one downlink sub-band in the plurality of downlink frequency bands. In the embodiment of the application, the downlink frequency division multiplexing electrical signal is generated according to downlink signals on a plurality of downlink sub-frequency bands which are not overlapped in a frequency domain, each downlink sub-frequency band corresponds to one group of ONUs, namely, frequency bands occupied by the downlink signals received by the ONUs in different groups are not overlapped, interference does not exist, and therefore the ONUs can accurately receive the downlink signals corresponding to the ONUs and the communication quality of a user side is improved. In addition, the frequency division multiplexing signal is modulated in the electric domain, and the frequency division multiplexing signal is loaded into the emitted light and transmitted to the ONU, so that the OLT can modulate the sub-band signals corresponding to different ONUs only by one laser, does not need to be provided with a plurality of lasers, and does not need to emit a plurality of optical signals with different wavelengths, thereby solving the problem of difficult wavelength management and reducing the device cost.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings used in the description of the embodiments will be briefly introduced below, and it is apparent that the drawings in the following description are only some embodiments of the present application.

Fig. 1 is a schematic diagram of a PON system using wavelength division multiplexing transmission in the prior art;

fig. 2 is a schematic diagram of a PON system in an embodiment of the present application;

fig. 3 is a schematic diagram of an embodiment of a signal transmission method of a PON system according to an embodiment of the present application;

fig. 4A is a schematic diagram of uplink and downlink frequency bands divided by an OLT in the embodiment of the present application;

fig. 4B is a schematic diagram of another embodiment of a signal transmission method of a PON system according to the embodiment of the present application;

fig. 4C is a schematic structural diagram of an OLT transmitter in an embodiment of the present application;

FIG. 4D is a diagram illustrating a structure of a coherent receiver according to an embodiment of the present application;

fig. 5 is a schematic diagram of another embodiment of a signal transmission method of a PON system according to an embodiment of the present application;

fig. 6A is a schematic structural diagram of an ONU transmitter in the embodiment of the present application;

fig. 6B is a schematic frequency spectrum diagram corresponding to the uplink frequency division multiplexing optical signal after being moved to the electrical domain baseband in the embodiment of the present application;

fig. 6C is a schematic diagram illustrating that an ONU obtains each uplink sub-band electrical signal corresponding to an uplink frequency division multiplexing optical signal in the embodiment of the present application;

fig. 7 is a schematic diagram of an embodiment of an OLT in an embodiment of the present application;

fig. 8 is a schematic diagram of another embodiment of an OLT in an embodiment of the present application;

fig. 9 is a schematic diagram of an embodiment of an ONU in the embodiment of the present application;

fig. 10 is a schematic diagram of an embodiment of an ONU in the embodiment of the present application;

fig. 11 is a schematic diagram of an embodiment of an OLT in an embodiment of the present application;

fig. 12 is a schematic diagram of an embodiment of a PON system in an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments.

The terms "first," "second," "third," "fourth," and the like in the description and in the claims of the present application and in the above-described drawings (if any) are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

It should be understood that the technical solution of the embodiment of the present application is applied to a communication system including a PON, for example: a global system for mobile communication (GSM) system, a Code Division Multiple Access (CDMA) system, a Wideband Code Division Multiple Access (WCDMA) system, a General Packet Radio Service (GPRS), a long term evolution (long term evolution, LTE) system, a Frequency Division Duplex (FDD) system, a Time Division Duplex (TDD) system, a universal mobile telecommunications system (universal mobile telecommunications system, UMTS), a Worldwide Interoperability for Microwave Access (WiMAX) communication system, or a fifth-generation mobile telecommunications technology (5-generation, 5G), and so on, which are specific examples of the embodiments and are not limited in this application.

For easy understanding of the embodiments of the present application, the PON system is briefly described below.

The PON refers to an optical fiber network (ODN) that does not include any electronic device or electronic power supply, and the ODN is composed of all passive devices such as an optical Splitter (Splitter), and does not require expensive active electronic devices. A PON comprises an OLT, which is mounted at a central control station, and a set of associated ONUs, which are mounted at customer sites. The ODN between the OLT and the ONU) contains an optical fiber and a passive optical splitter or coupler, as shown in fig. 2.

The PON system structure mainly includes an OLT of a central office, an ODN including a passive optical device, an Optical Network Unit (ONU)/Optical Network Terminal (ONT) of a user side, where the difference is that the ONT is directly located at the user side, and there are other networks, such as an ethernet, between the ONU and the user, and an Element Management System (EMS), and generally adopts a point-to-multipoint tree topology structure. The embodiment of the present application will be described by taking an ONU as an example, and it should be understood that the functions performed by the ONU in the present application may also be performed by the ONT.

To facilitate understanding of the embodiments of the present application, the background to which the present application relates is described below.

Frequency Division Multiplexing (FDM) is the division of the total bandwidth used for a transmission channel into several sub-bands (or sub-channels), each of which transmits 1 channel of signals. The total frequency width of frequency division multiplexing is required to be larger than the sum of the frequencies of all the sub-channels, and meanwhile, in order to ensure that signals transmitted in all the sub-channels do not interfere with each other, an isolation band is required to be arranged among all the sub-channels, so that all the paths of signals are ensured not to interfere with each other (one of conditions). The frequency division multiplexing technology is characterized in that signals transmitted by all sub-channels work in a parallel mode, and transmission time delay can be not considered when each path of signals are transmitted.

Coherent detection: the carrier wave of the modulation signal is multiplied by the received modulation signal, and then the detection mode of the modulation signal is obtained through low-pass filtering.

A coherent receiver: a continuous light source with the wavelength close to that of the signal light source is arranged in the receiver, mixed with the signal light and detected, and the continuous light source with the wavelength close to that of the light source is called intrinsic light, namely the continuous light source for coherent reception is called intrinsic light.

Referring to fig. 3, a signal transmission method of a PON system in an embodiment of the present application is described, where an embodiment of the signal transmission method of the PON system in the present application includes:

301. the ONU sets the frequency of the ONU intrinsic light to a first frequency.

The OLT divides the total bandwidth of the PON system into a plurality of sub-bands, and allocates the sub-bands of the uplink and downlink signals, that is, the OLT determines an uplink sub-band for uplink transmission of the PON system and a downlink sub-band for downlink transmission of the PON system among the plurality of sub-bands.

Specifically, there is a band gap between the downlink sub-bands determined by the OLT for downlink transmission, i.e., each downlink sub-band does not overlap in the frequency domain. In this embodiment, as an alternative, the OLT may number several sub-bands in sequence, as shown in fig. 4A, all odd numbered subbands are used as downlink subbands, all even numbered subbands are used as uplink subbands, or all odd numbered sub-bands are used as uplink sub-bands, all even numbered sub-bands are used as uplink sub-bands, that is, a plurality of sub-bands corresponding to the PON system are divided in an up-down interval manner (up-down, up-down … …), that is, for any two adjacent sub-bands (the first sub-band and the second sub-band) in the frequency domain, the OLT allocates one of the sub-bands (the first sub-band) as an uplink sub-band to the ONU in the PON system, and allocates the other sub-band (the second sub-band) as a downlink sub-band to the ONU in the PON system.

After the OLT determines the downlink sub-bands used for transmitting the downlink signals in the PON system, the OLT allocates the downlink sub-bands to the ONUs in the PON system, and after the ONUs determine the sub-bands corresponding to the ONUs, the ONU intrinsic light in the coherent receiver is set to be a first frequency, wherein the first frequency corresponds to the sub-bands corresponding to the ONUs. It should be understood that, in this embodiment, the fact that the first frequency corresponds to the sub-band corresponding to the ONU means that the first frequency is a frequency on the sub-band, specifically, the first frequency is equal to a center frequency of the sub-band, or a difference between the first frequency and the center frequency of the sub-band is within an error range.

As an optional manner, the OLT may allocate the downstream sub-bands to the ONUs in the PON system in the following manner, that is, the ONUs may determine their corresponding sub-bands in the following manner:

(1) the OLT determines a target sub-band which is idle or unregistered with the target sub-band in a downlink sub-band corresponding to the PON system;

(2) the OLT transmits an inquiry message on the target sub-band and suspends transmitting signals on other frequency bands except the target sub-band;

(3) the ONU adjusts the frequency of the ONU intrinsic light, and performs coherent detection on the intrinsic light and an inquiry message sent by the OLT aiming at the ONU intrinsic light of each frequency to determine coherent detection output power corresponding to each frequency;

the ONU to be online controls the frequency of the ONU coherent receiver by adjusting a semiconductor cooler (TEC), full bandwidth polling is carried out by taking the spectrum width occupied by the sub-band as a step length, namely, the ONU adjusts the frequency of the ONU intrinsic light by taking a preset value as the step length through the TEC, and the coherent detection output power of the intrinsic light emitted by the coherent receiver and the inquiry message under the frequency is calculated when one frequency is set until the intrinsic light of all the frequencies is detected.

(4) And the ONU determines the frequency corresponding to the maximum value in the coherent detection output power corresponding to each frequency as a first frequency.

It should be appreciated that when the coherent detection output signal power is highest, the frequency representing the intrinsic light is closest to the target sub-band. After the ONU finishes the full-bandwidth polling, determining that the frequency corresponding to the maximum value in the coherent detection output powers corresponding to the frequencies is the first frequency, and the sub-band where the first frequency is located is the sub-band corresponding to the ONU.

After the ONU determines the first frequency in the above way, the frequency of the ONU intrinsic light is set as the first frequency, that is, the temperature of the TEC is set as the temperature value when the coherent detection output power is maximum.

As an optional mode, after the ONU sets the frequency of the intrinsic light to the first frequency, the ONU performs frequency offset estimation according to a downlink signal (inquiry message) received by the intrinsic light of the first frequency to obtain a frequency offset value, modulates an uplink sub-band signal according to the frequency offset value, and reports registration information to the OLT through the uplink sub-band signal, where the registration information is used to request registration of a sub-band where the first frequency is located, and the registration information includes a Media Access Control (MAC) address of the ONU. Specifically, the ONU may modulate the upstream subband signal by: and the ONU processes the baseband signal corresponding to the registration information through a low-pass filter, then carries out frequency shift on the processed signal to a signal on a target frequency, and loads the signal on the target frequency into the ONU emitted light to finish the sending of the registration information. Wherein the value of the target frequency is equal to the first frequency minus the frequency offset value.

And after receiving the registration information sent by the ONU, the OLT determines that the sub-band requested to be registered by the OLT corresponds to the target sub-band, records the MAC address of the ONU, sends authorization information to the ONU on the target sub-band according to the MAC address, and resumes sending other sub-band signals.

And after receiving the authorization information sent by the ONU through the ONU intrinsic light of the first frequency, the ONU processes and synchronizes the message and then sends a confirmation message to the OLT. Optionally, the authorization information sent by the ONU may include an uplink dynamic bandwidth allocation message, which is used to indicate an uplink sub-band used by the ONU to transmit an uplink signal, and the ONU may frequency-shift a baseband signal carrying the acknowledgement message to the indicated uplink sub-band, and load the frequency-shifted signal into the ONU-emitted light to transmit to the ONU. The authorization information sent by the ONU may not include the uplink dynamic bandwidth allocation message, and the ONU may send the confirmation message in a manner similar to the above sending the inquiry message, which is not described herein again.

After receiving the acknowledgement message sent by the ONU, the OLT completes handshake, that is, completes allocation of the downstream sub-band of the ONU, and the ONU successfully comes on line, and thereafter, the OLT and the ONU start normal communication, and the OLT can send downstream data containing an upstream dynamic bandwidth allocation message on a target sub-band, and the ONU modulates and sends an upstream sub-band signal according to the upstream bandwidth allocation message. As shown in fig. 4B, a flowchart for the OLT to allocate the downstream sub-band for the ONU is shown.

In this embodiment, ONUs that register the same downlink sub-band (the ONU-specific light is the same) are regarded as one ONU group, that is, one downlink sub-band corresponds to one group of ONUs, and the ONU-specific light of the same group of ONUs is the same, and the corresponding downlink sub-bands are the same. However, there is a gap between the downlink sub-bands divided by the OLT, so the downlink sub-bands corresponding to different groups of ONUs do not overlap between frequency domains.

302. The OLT generates a downlink frequency division multiplexing electrical signal corresponding to a plurality of downlink sub-bands.

The OLT allocates uplink sub-bands to each of the on-line ONUs, and after establishing communication connection with the ONUs, when downlink signals need to be sent to different groups of ONUs, the OLT determines a plurality of downlink sub-bands corresponding to the ONUs and generates downlink frequency division multiplexing signals corresponding to the plurality of downlink sub-bands. It should be understood that each of the plurality of downlink sub-bands does not overlap in the frequency domain based on the sub-band division principle described in 301 above.

Specifically, the OLT may generate the downlink sub-band electrical signal by: the OLT generates baseband signals corresponding to each ONU, then shapes the baseband signals through a low-pass filter to obtain target baseband signals corresponding to each ONU, then shifts the target baseband signals corresponding to each ONU to obtain downlink sub-band signals corresponding to each ONU on a downlink sub-band corresponding to each ONU, and finally combines the downlink sub-band signals corresponding to each ONU to obtain downlink frequency division multiplexing electrical signals.

303. And the OLT loads the downlink frequency division multiplexing electric signal to the OLT transmitting light to obtain a downlink frequency division multiplexing optical signal.

After the OLT generates the downlink frequency division multiplexing electrical signals corresponding to the plurality of downlink sub-bands, the downlink frequency division multiplexing electrical signals are loaded onto the optical signals through the optical modulator to obtain the downlink frequency division multiplexing optical signals.

Specifically, in this embodiment, step 302 and step 304 may be performed by a transmitter of the OLT, as shown in fig. 4C, which is a schematic diagram of the transmitter of the OLT, and the transmitter of the OLT includes: digital Signal Processors (DSPs), digital-to-analog converters (ADCs), drivers, optical modulators, and lasers. The OLT generates baseband signals corresponding to the ONUs in a digital domain, the baseband signals filter out-of-band signals through a filter to obtain target baseband signals, and then the target baseband signals are multiplied by exp (j × 2 pi × f) in the digital domain_t) Implementing frequency shift, moving the frequency of each target baseband signal to the corresponding sub-band to obtain the corresponding downlink signal (f)_tThe central frequency of the sub-band corresponding to the ONU), adding the downlink signals, and performing ADC conversion to obtain a frequency division multiplexing signal in the electrical domain, that is, the downlink frequency division multiplexing electrical signal. After being amplified by a driver, the downlink frequency division multiplexing electrical signal is loaded on OLT emission light emitted by a laser through an optical modulator to form a frequency division multiplexing signal on an optical domain, namely the downlink frequency division multiplexing optical signal.

304. The OLT transmits a downlink frequency division multiplexing optical signal.

After the OLT generates the downlink frequency division multiplexing optical signal, the downlink frequency division multiplexing optical signal is sent to each ONU through the ODN.

305. The ONU obtains a downlink sub-band electrical signal corresponding to the ONU from the downlink frequency division multiplexing optical signal through the ONU intrinsic light of the first frequency.

After the ONU sets the frequency of the ONU intrinsic light to be the first frequency, when the OLT sends the downlink frequency division multiplexing optical signal, the ONU performs coherent reception through the ONU intrinsic light and acquires a corresponding downlink sub-band signal from the downlink frequency division multiplexing optical signal.

Specifically, the step 305 may be performed by a coherent receiver in the ONU, as shown in fig. 4D, which is a schematic structural diagram of the coherent receiver. The method comprises the steps that a downlink frequency division multiplexing optical signal and ONU intrinsic light are mixed, the mixed signal is detected by a balance detector and then converted into an electric signal, the electric signal takes a first frequency as a center, the downlink frequency division multiplexing optical signal is moved to an electric domain baseband, a plurality of sub-frequency bands corresponding to the downlink frequency division multiplexing optical signal are distributed on corresponding positions of a positive frequency band and a negative frequency band, the received electric signal is converted into a digital domain by adopting an ADC, and the downlink sub-frequency band electric signal corresponding to the ONU is obtained through band-pass filtering processing.

In this embodiment of the application, the OLT may generate a downlink frequency division multiplexing electrical signal corresponding to a plurality of downlink sub-bands, load the downlink frequency division multiplexing electrical signal onto the OLT to emit light to obtain a downlink frequency division multiplexing optical signal, and send the downlink frequency division multiplexing optical signal, and the ONU may obtain a downlink sub-band signal corresponding to the ONU from the downlink frequency division multiplexing optical signal by using the ONU intrinsic light of a first frequency through the coherent receiver, where the first frequency corresponds to one downlink sub-band in the plurality of downlink frequency bands. In the embodiment of the application, the downlink frequency division multiplexing electrical signal is generated according to downlink signals on a plurality of downlink sub-frequency bands which are not overlapped in a frequency domain, each downlink sub-frequency band corresponds to one group of ONUs, namely, frequency bands occupied by the downlink signals received by the ONUs in different groups are not overlapped, interference does not exist, and therefore the ONUs can accurately receive the downlink signals corresponding to the ONUs and the communication quality of a user side is improved. In addition, the frequency division multiplexing signal is modulated in the electric domain, and the frequency division multiplexing signal is loaded into the emitted light and transmitted to the ONU, so that the OLT can modulate the sub-band signals corresponding to different ONUs only by one laser, does not need to be provided with a plurality of lasers, and does not need to emit a plurality of optical signals with different wavelengths, thereby solving the problem of difficult wavelength management and reducing the device cost.

Secondly, in the embodiment of the present application, the OLT may stagger and allocate the sub-bands, so as to effectively avoid interference of the reflected signals of different sub-bands on the sub-band information of the uplink and downlink optical signals.

In the above, a signal transmission method of the PON system in the present application is described from a downstream transmission perspective, and in the following, a signal transmission method of the PON system in the present application is described from an upstream transmission perspective, referring to fig. 5, an embodiment of the signal transmission method in the embodiment of the present application includes:

501. and the ONU carries out frequency shift on the baseband signal to obtain an uplink sub-band electric signal corresponding to the ONU.

After the ONU successfully comes online, normal communication with the OLT can be started, the OLT sends downlink data including an uplink dynamic bandwidth allocation message on an uplink sub-band registered by the ONU (the uplink sub-band allocated to the ONU by the OLT), and the ONU can determine the uplink sub-band allocated to the ONU by the OLT according to the uplink bandwidth allocation message. After the uplink sub-band is determined, the ONU may use radio frequency modulation in the electrical domain, that is, generate a baseband signal corresponding to the ONU, filter an out-of-band signal in the baseband signal through a filter, and frequency shift the baseband signal from which the out-of-band signal is filtered according to the allocated uplink sub-band to obtain a corresponding uplink sub-band electrical signal, that is, the uplink sub-band electrical signal obtained through frequency shift corresponds to the uplink sub-band allocated to the ONU.

502. And the ONU loads the uplink sub-band electric signal to the ONU emitted light to obtain the uplink sub-band optical signal.

And after the ONU modulates the uplink sub-band electric signal, the ONU loads the uplink sub-band electric signal to the ONU emitted light to obtain an uplink sub-band optical signal.

As an alternative, the ONU emits light from a laser in the ONU, and the laser adjusts the frequency through the TEC, and controlling the frequency of the laser through the TEC may cause a certain error, that is, the set frequency is not accurate, which may cause crosstalk between uplink optical signals modulated by the ONUsEqual to the frequency of the laser plus the center frequency of the electrical domain radio frequency signal, i.e. the center frequency of the upstream sub-band optical signal is equal to the frequency of the laser plus the center frequency of the upstream sub-band electrical signal. Therefore, in this embodiment, the frequency of the laser may be compensated by the center frequency of the modulated point signal of the uplink sub-band, specifically, the ONU performs frequency shift on the baseband signal to obtain the uplink sub-band electrical signal corresponding to the ONU, and the center frequency f of the frequency-shifted uplink sub-band electrical signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated to the ONU by the OLT, f₁The frequency of light emitted by the ONU is delta f, the frequency error of the laser is obtained by the ONU through calculation of a frequency offset estimation algorithm according to a downlink sub-band electrical signal sent to the ONU by the OLT.

Specifically, the step 502 is executed by a receiver of an ONU, as shown in fig. 6A, which is a schematic structural diagram of the ONU receiver, and the ONU receiver includes: DSP, ADC, driver, light modulator and laser. The ONU generates a corresponding baseband signal in a digital domain, filters out an out-of-band signal in the baseband signal through a filter, and multiplies the out-of-band signal by exp (j × 2 pi × f) in the digital domain₂) The frequency shift is realized, then the sub-band signal on the electrical domain, namely the uplink sub-band electrical signal, is obtained after the conversion by the ADC, and the uplink sub-band electrical signal is amplified by the driver and then loaded on the ONU emitted light emitted by the laser through the optical modulator, so that the sub-band signal on the optical domain, namely the uplink sub-band optical signal, is formed.

503. And the ONU sends the uplink sub-band optical signal corresponding to the ONU.

After the ONU obtains an upstream sub-band optical signal through optical domain modulation, the upstream sub-band optical signal is sent to the OLT through the ODN. The wave combiner combines the uplink sub-band optical signals corresponding to different uplink sub-bands sent by the plurality of ONUs to obtain the uplink frequency division multiplexing optical signal. It should be understood that the different uplink sub-bands described in this embodiment do not overlap in the frequency domain.

504. And the OLT acquires each uplink sub-band electric signal corresponding to the uplink frequency division multiplexing optical signal through the OLT intrinsic light with the second frequency.

In this implementation, the second frequency is set according to a standard, and the OLT allocates an upstream sub-band for upstream transmission to the plurality of ONUs with the second frequency as a center, that is, the second frequency is aligned with a center frequency of the upstream frequency division multiplexing optical signal corresponding to the plurality of ONUs. After the OLT allocates the uplink sub-band for each ONU through the uplink dynamic bandwidth allocation message, each ONU modulates and sends a corresponding uplink sub-band electric signal according to the allocated uplink sub-band, and each uplink sub-band electric signal is combined by a combiner to obtain an uplink frequency division multiplexing optical signal. And the OLT acquires each uplink sub-band electric signal corresponding to the uplink frequency division multiplexing optical signal through the OLT intrinsic light with the second frequency.

Specifically, the above step 504 may be performed by a coherent receiver in the OLT (the structure of the coherent receiver may be see fig. 4D). Mixing the uplink frequency division multiplexing optical signal with the OLT intrinsic light, detecting by a balance detector, and converting into an electrical signal, wherein the electrical signal takes the second frequency as the center, moving the uplink frequency division multiplexing optical signal to an electrical domain baseband, at the moment, a plurality of uplink sub-bands corresponding to the uplink frequency division multiplexing optical signal are distributed on corresponding positions of a positive frequency band and a negative frequency band, as shown in fig. 6B, adopting an ADC to convert the uplink sub-band electrical signals corresponding to the plurality of uplink sub-bands into a digital domain, and then multiplying the uplink sub-band electrical signals by exp (j 2 pi f) in the digital domain for each uplink sub-band electrical signal_t) Effecting a frequency shift (f)_tCorresponding to the central frequency of the uplink sub-band for each ONU), and filtering the uplink sub-band electrical signal by using a low-pass digital filter, so as to obtain an uplink sub-band electrical signal without crosstalk, as shown in fig. 6C.

As an optional manner, in the method embodiment corresponding to fig. 5, the ONU may further perform steps 301 and 305 in the embodiment corresponding to fig. 3, and the OLT may further perform steps 302 to 304 in the embodiment corresponding to fig. 3, that is, the OLT may further allocate a downlink sub-band to each ONU, generate a plurality of ONU-corresponding downlink frequency-division multiplexing electrical signals, load the downlink frequency-division multiplexing electrical signals onto the OLT emitting light to obtain downlink frequency-division multiplexing optical signals, and send the downlink frequency-division multiplexing optical signals, and the ONU may set the frequency of the ONU intrinsic light to the first frequency according to the downlink sub-band allocated by the OLT, and then obtain the ONU-corresponding downlink sub-band electrical signals from the downlink frequency-division multiplexing optical signals sent by the OLT through the ONU intrinsic light of the first frequency. That is, in this embodiment, the OLT and the ONU in the PON system may perform downlink transmission through the method flow in the embodiment corresponding to fig. 3, and perform uplink transmission through the method flow in the embodiment corresponding to fig. 5.

As an optional manner, when the OLT in the PON system sends the downstream frequency division multiplexing optical signal in the manner corresponding to steps 302 to 305 in the embodiment corresponding to fig. 3, and acquires the upstream sub-band electrical signal sent by each ONU in the manner corresponding to step 504 in the embodiment corresponding to fig. 5, the emitted light used by the OLT for sending the downstream frequency division multiplexing optical signal (i.e., the OLT emitted light) and the intrinsic light used by the OLT for receiving the upstream sub-band electrical signal (i.e., the OLT intrinsic light) may be sent by the same light source, that is, the frequencies of the OLT emitted light and the OLT intrinsic light are equal, that is, the transmitter and the receiver of the OLT share one light source.

Similarly, when the ONU in the PON system transmits the upstream sub-band electrical signal in the manner corresponding to steps 501 to 503 in the corresponding embodiment of fig. 5 and receives the downstream sub-band electrical signal in the manner corresponding to steps 301 and 305 in the corresponding embodiment of fig. 3, the emitted light used by the ONU for transmitting the downstream sub-band electrical signal (i.e., ONU emitted light) and the intrinsic light used by the ONU for receiving the upstream sub-band electrical signal (i.e., ONU intrinsic light) may be emitted by the same light source, i.e., the frequencies of the ONU emitted light and the ONU intrinsic light are equal, i.e., the transmitter and the receiver of the ONU share one light source.

In this embodiment, the ONU may perform radio frequency modulation in the electrical domain to compensate for instability of the laser frequency, so that the optical network unit sends a stable optical signal, thereby avoiding crosstalk between uplink signals sent by different optical network units.

Secondly, the OLT may receive the uplink signal sent by the optical network unit in a coherent detection manner, that is, the optical line terminal may obtain the uplink signal sent by each optical network unit only by aligning the intrinsic light to the center frequency of the uplink frequency division multiplexing optical signal, and the operation is simple and the cost is low.

With reference to fig. 7, an embodiment of the OLT in the present application includes:

a generating module 701, configured to generate a downlink frequency division multiplexing electrical signal corresponding to a plurality of downlink sub-bands, where each downlink sub-band in the plurality of downlink sub-bands is not overlapped in a frequency domain, and each downlink sub-band corresponds to a group of optical network units ONU;

a loading module 702, configured to load the downlink frequency division multiplexing electrical signal onto the OLT to obtain a downlink frequency division multiplexing optical signal;

a first sending module 703, configured to send the downlink frequency division multiplexing optical signal, so that an ONU with a frequency of the ONU intrinsic light being a first frequency obtains a downlink sub-band signal corresponding to the ONU from the downlink frequency division multiplexing optical signal, where the first frequency corresponds to one downlink sub-band in the multiple downlink sub-bands.

Optionally, in this embodiment, the generating module 701 includes:

a generating submodule 7011, configured to generate a baseband signal corresponding to each ONU;

the shaping submodule 7012 is configured to shape the baseband signal through a low-pass filter to obtain a target baseband signal corresponding to each ONU;

a frequency shift sub-module 7013, configured to, for each ONU, frequency shift the target baseband signal corresponding to the ONU to obtain a downlink sub-band signal corresponding to the ONU on the downlink sub-band corresponding to the ONU;

and the merging submodule 7014 is configured to merge the downlink sub-band signals corresponding to each ONU to obtain a downlink frequency division multiplexing electrical signal.

Optionally, in this embodiment, the OLT further includes:

Optionally, in this embodiment, the OLT may further include:

a determining module 704, configured to determine a target sub-band in an idle state or an unregistered full target sub-band in a downlink sub-band corresponding to a PON system, where the downlink sub-band corresponding to the PON system is not overlapped in a frequency domain;

the second sending module 705 is further configured to send the inquiry message on the target sub-band, and suspend sending signals on other frequency bands except the target sub-band, so that the ONU determines the first frequency according to the inquiry message, and the target sub-band is a downstream sub-band corresponding to the ONU.

Optionally, in this embodiment, the OLT further includes:

an obtaining module 706, configured to obtain each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, where the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal, and the uplink frequency division multiplexing optical signal is a signal obtained after combining multiple uplink sub-band optical signals. The OLT intrinsic light and the OLT emitted light are light emitted by a unified light source.

It should be understood that, in the embodiment corresponding to fig. 7, the flow executed between the modules of the OLT is the same as the flow type in the method embodiment corresponding to fig. 3 and fig. 5, and details are not repeated here.

In this embodiment of the application, the generating module 701 may generate a plurality of downlink frequency division multiplexing electrical signals corresponding to downlink frequencies, the loading module 702 loads the downlink frequency division multiplexing electrical signals onto the OLT to emit light to obtain downlink frequency division multiplexing optical signals, the first sending module 703 sends the downlink frequency division multiplexing optical signals, and the ONU may obtain, by using the ONU intrinsic light of a first frequency through the coherent receiver, a downlink sub-band signal corresponding to the ONU from the downlink frequency division multiplexing optical signals, where the first frequency corresponds to one downlink sub-band in the plurality of downlink frequency bands. In the embodiment of the application, the downlink frequency division multiplexing electrical signal is generated according to downlink signals on a plurality of downlink sub-frequency bands which are not overlapped in a frequency domain, each downlink sub-frequency band corresponds to one group of ONUs, namely, frequency bands occupied by the downlink signals received by the ONUs in different groups are not overlapped, interference does not exist, and therefore the ONUs can accurately receive the downlink signals corresponding to the ONUs and the communication quality of a user side is improved. In addition, the frequency division multiplexing signal is modulated in the electric domain, and the frequency division multiplexing signal is loaded into the emitted light and transmitted to the ONU, so that the OLT can modulate the sub-band signals corresponding to different ONUs only by one laser, does not need to be provided with a plurality of lasers, and does not need to emit a plurality of optical signals with different wavelengths, thereby solving the problem of difficult wavelength management and reducing the device cost.

Secondly, in the embodiment of the present application, the allocation module may stagger and allocate the sub-bands, so as to effectively avoid interference of the reflection signals of different sub-bands on the sub-band information of the uplink and downlink optical signals.

In this embodiment, the obtaining module 706 may receive the uplink signal sent by the optical network unit in a coherent detection manner, that is, the optical line terminal only needs to align the intrinsic light to the center frequency of the uplink frequency division multiplexing optical signal to obtain the uplink signal sent by each optical network unit, and the operation is simple and the cost is low.

Referring to fig. 8, another embodiment of the OLT in the present application includes:

an obtaining module 801, configured to obtain each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, where the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal, and the uplink frequency division multiplexing optical signal is a signal obtained after combining multiple uplink sub-band optical signals. The OLT intrinsic light and the OLT emitted light are light emitted by a unified light source.

Optionally, in this embodiment, the OLT may further include:

an allocating module 802, configured to allocate a first sub-band as an uplink sub-band to an optical network unit in the PON system, and allocate a second sub-band as a downlink sub-band to the optical network unit in the PON system, where the first sub-band and the second sub-band are adjacent in a frequency domain, that is, for any two adjacent sub-bands in the frequency domain, an optical line terminal will use one of the two sub-bands as the uplink sub-band, and use the other as the uplink sub-band.

Further, the allocating module 802 may further include:

a determining submodule 8021, configured to determine a target frequency sub-band in an idle state or not fully registered in a downlink frequency sub-band (i.e., a first frequency band) corresponding to the PON system;

the transmitting sub-module 8022 is configured to transmit the query message on the target sub-band, and suspend transmitting signals on sub-bands other than the target sub-band, so that the optical network unit may determine the first frequency according to the query message on the target sub-band, where the target sub-band is a downlink sub-band allocated to the optical network unit by the optical line terminal, that is, the downlink sub-band of the optical network unit corresponds to the target sub-band.

In the embodiment of the application, the optical line terminal can obtain the uplink signals sent by each optical network unit only by aligning the intrinsic light to the central frequency of the uplink frequency division multiplexing optical signal, and the operation is simple and the cost is low.

Secondly, the allocation module 802 allocates the sub-bands in a staggered manner, so that interference of the reflection signals of different sub-bands on the sub-band information of the uplink and downlink optical signals can be effectively avoided.

Referring to fig. 9, an embodiment of an ONU in the present application includes:

a setting module 901, configured to set a frequency of the ONU intrinsic light to a first frequency, where the first frequency corresponds to a target sub-band;

a receiving module 902, configured to obtain, from a downlink frequency division multiplexing optical signal, a downlink sub-band signal corresponding to an ONU through ONU intrinsic light of a first frequency, where the downlink frequency division multiplexing optical signal is obtained by loading, by an OLT, a downlink frequency division multiplexing electrical signal corresponding to multiple sub-bands onto light emitted by the OLT, where each of the multiple downlink sub-bands is not overlapped in a frequency domain, and the multiple downlink sub-bands include a target sub-band.

Optionally, in this embodiment, the ONU may further include:

an adjusting module 903, configured to adjust frequencies of the ONU intrinsic light, perform coherent detection on the ONU intrinsic light and an inquiry message sent by the OLT in a target sub-band for each frequency of the ONU intrinsic light, and determine coherent detection output power corresponding to each frequency;

a determining module 904, configured to determine a frequency corresponding to a maximum value in the coherent detection output power as the first frequency.

Optionally, in this embodiment, the ONU may further include:

a frequency shift module 905, configured to perform frequency shift on the baseband signal to obtain an uplink sub-band electrical signal corresponding to the ONU, where a center frequency of the uplink sub-band electrical signal corresponds to an uplink sub-band allocated to the ONU by the OLT;

a loading module 906, configured to load the uplink sub-band electrical signal onto an ONU-emitting light to obtain an uplink sub-band optical signal;

the sending module 907 is configured to send an uplink sub-band optical signal corresponding to the ONU, so that the passive combiner combines the sub-band optical signal corresponding to the ONU with uplink sub-band optical signals sent by other ONUs in the PON system to obtain an uplink frequency division multiplexing optical signal, and the OLT obtains each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, where the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal.

Specifically, the step of enabling the center frequency of the upstream sub-band electrical signal to correspond to the upstream sub-band allocated to the ONU by the OLT includes: center frequency f of up sub-band electric signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated by the OLT to the ONU, f₁For the frequency of the light emitted by the ONU, Δ f is a frequency offset value calculated by a frequency offset estimation algorithm according to the downlink sub-band electrical signal. The ONU emitted light and the ONU intrinsic light are light emitted by the same light source in the ONU.

It should be understood that, in the embodiment corresponding to fig. 9, the flow executed between the modules of the ONU is the same as the flow type in the method embodiment corresponding to fig. 3 and fig. 5, and details are not repeated here.

In the embodiment of the application, the downlink frequency division multiplexing electrical signal is generated according to downlink signals on a plurality of downlink sub-frequency bands which are not overlapped in a frequency domain, each downlink sub-frequency band corresponds to one group of ONUs, namely, frequency bands occupied by the downlink signals received by the ONUs in different groups are not overlapped, interference does not exist, and therefore the ONUs can accurately receive the downlink signals corresponding to the ONUs and the communication quality of a user side is improved. In addition, the frequency division multiplexing signal is modulated in the electric domain, and the frequency division multiplexing signal is loaded into the emitted light and transmitted to the ONU, so that the OLT can modulate the sub-band signals corresponding to different ONUs by only one laser, does not need to be provided with a plurality of lasers, and does not need to emit a plurality of optical signals with different wavelengths, thereby solving the problem of difficult wavelength management and reducing the device cost.

And secondly, the ONU can perform radio frequency modulation in an electrical domain to compensate the instability of the laser frequency, so that the optical network unit sends out stable optical signals, and the crosstalk between uplink signals sent by different optical network units can be avoided.

Referring to fig. 10, another embodiment of an ONU in the present application further includes:

a frequency shift module 1001, configured to perform frequency shift on a baseband signal to obtain an uplink sub-band electrical signal corresponding to an ONU, where a center frequency of the uplink sub-band electrical signal corresponds to an uplink sub-band allocated to the ONU by the OLT;

the loading module 1002 is configured to load the uplink sub-band electrical signal to an ONU to obtain an uplink sub-band optical signal;

the sending module 1003 is configured to send an uplink sub-band optical signal corresponding to the ONU, so that the passive combiner combines the sub-band optical signal corresponding to the ONU with uplink sub-band optical signals sent by other ONUs in the PON system to obtain an uplink frequency division multiplexing optical signal, and the OLT obtains each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, where the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal.

Optionally, in this embodiment, the correspondence between the center frequency of the uplink sub-band electrical signal and the uplink sub-band allocated to the ONU by the OLT specifically means the center frequency f of the uplink sub-band electrical signal₂＝f-f₁- Δ f, where f is the center frequency of the upstream sub-band allocated by the olt to the onu, f₁For the frequency of the light emitted by the optical network unit, Δ f is calculated by frequency offset estimation based on the electrical signal of the downstream sub-bandAnd calculating the obtained frequency offset value.

Optionally, in this embodiment, the ONU may further include:

the adjusting module 1004 is used for adjusting the frequency of the intrinsic light of the optical network unit;

a determining module 1005, configured to perform coherent detection on the onu intrinsic light and the query message sent by the optical line terminal in the target sub-band for each frequency of the onu intrinsic light, determine coherent detection output powers corresponding to the respective frequencies, and determine a frequency corresponding to a maximum value in the coherent detection output powers as a first frequency.

In the embodiment of the application, the ONU can perform radio frequency modulation in the electrical domain to compensate for instability of the laser frequency, so that the optical network unit sends a stable optical signal, and crosstalk between uplink signals sent by different optical network units can be avoided.

The OLT and the ONU in the present application are introduced from the perspective of the functional module above, and the OLT and the ONU in the present application are introduced from the perspective of the physical hardware below, and fig. 11 is a schematic structural diagram of the OLT or the ONU in the embodiment of the present invention. Olt (onu)110 may comprise a receiver 1110, a transmitter 1120, a processor 1130, and a memory 1140. Memory 1140 may include both read-only memory and random access memory and provides instructions and data to processor 1130. A portion of Memory 1140 may also include Non-Volatile Random Access Memory (NVRAM).

Memory 1140 stores the following elements, executable modules or data structures, or a subset thereof, or an expanded set thereof:

and (3) operating instructions: including various operational instructions for performing various operations.

Operating the system: including various system programs for implementing various basic services and for handling hardware-based tasks.

The processor 1130 in the embodiment of the present invention is configured to execute the operation instructions in the memory 1140, so that the OLT or the ONU performs the steps in the embodiment of the method corresponding to fig. 3 or fig. 5 as described above.

An embodiment of the present application further provides a PON system, where the PON system includes an OLT in the embodiment corresponding to fig. 7 and a plurality of ONUs in the embodiment corresponding to fig. 11.

An embodiment of the present application further provides a PON system, where the PON system includes an OLT in the embodiment corresponding to fig. 9 and a plurality of ONUs in the embodiment corresponding to fig. 10.

To facilitate understanding of the present application, a specific scenario example is described below, and referring to fig. 12, a PON system in an embodiment of the present application includes: OLT transmitter, ONU coherent receiver, ONU transmitter and OLT coherent receiver.

The OLT transmitter is full-bandwidth frequency division multiplexing modulation, adopts a single laser light source, and realizes frequency division multiplexing optical signal modulation by loading a frequency division multiplexing electrical modulation signal on an external modulator. Each sub-band signal of the frequency division multiplexing optical signal is distributed to a specific array of ONU through the OLT, and each group of ONU occupies the sub-rate peak bandwidth. Certain frequency intervals can be reserved among the sub-frequency bands to ensure that no crosstalk exists among the sub-frequency bands, or electric domain filtering shaping can be adopted to completely filter signals outside the sub-frequency bands, so that crosstalk among the sub-frequency bands is effectively avoided.

The ONU coherent receiver uses an intrinsic laser to select the sub-band signal. The frequency of the output light of the intrinsic laser is controlled by adjusting the temperature by utilizing the correlation between the frequency of the intrinsic laser and the temperature. The frequency of the intrinsic laser is aligned to the frequency sub-band corresponding to each ONU, the required sub-band information can be selected, and the sub-band information is moved to the electrical domain fundamental frequency to carry out DSP processing judgment. Due to the reduction of the peak rate, the bandwidth of the device of the sub-rate coherent receiver is reduced to the bandwidth of the sub-band, and invalid information outside the required sub-band frequency is effectively filtered.

The ONU subrate transmitter adopts the subband modulation, and effectively reduces the bandwidth requirement of the transmitter by loading the subband radio-frequency signal on the external modulator. And the sub-band signals of each ONU are combined into a multi-band frequency division multiplexing signal after uplink transmission through a passive combiner. The ONU terminal rate transmitter and the coherent receiver intrinsically share the same light source, so that on one hand, the cost is effectively reduced, on the other hand, the intrinsic light source is aligned to the wavelength of the downlink sub-band, the accurate alignment of the position of the uplink sub-rate modulation frequency is effectively ensured, and the inter-band crosstalk generated after wave combination is avoided.

The OLT detects the uplink combined multiband ofdm signal (i.e., uplink ofdm optical signal) using a full-rate coherent receiver. The intrinsic of the OLT-end full-rate coherent receiver and the OLT transmitter share the same light source, so that the cost is effectively reduced, and meanwhile, the intrinsic light source frequency is ensured to be effectively aligned with the central frequency of the uplink multi-band frequency division multiplexing signal, and the full-band signal is detected.

The PON system effectively reduces the bandwidth requirement of ONU side devices in the single-wave high-speed PON system through frequency division multiplexing modulation and sub-rate coherent reception, greatly improves the receiving sensitivity of the single-wave high-speed PON system, has the advantages of low cost and high power budget, and can be effectively applied to the next-generation high-capacity high-speed PON system.

Furthermore, in the PON system, sub-bands of uplink and downlink signals are allocated so that the sub-bands of the uplink and downlink signal light occupy odd/even number of frequency bands, and interference of reflected signals of different frequency bands on sub-band information on the uplink and downlink signal light is effectively avoided by using a frequency selective characteristic of coherent reception.

And in the low-cost coherent ONU with the sub-rate, the downlink sub-rate signal is received, and the selection of the sub-band signal is carried out by adjusting the frequency of the intrinsic light source. And the modulation of the uplink subrate signal adopts high-frequency radio frequency modulation, and the subband signal is loaded to the corresponding subband.

Furthermore, in the PON system, the uplink transmission light is aligned with the downlink receiving sub-band, and considering that a certain error (1.25GHz) exists in the TEC-controlled laser frequency, in order to ensure that each sub-band modulated by the ONU is accurately aligned and avoid aliasing of each sub-band frequency band after combination to cause crosstalk, the uplink sub-band center frequency is accurately aligned by innovative frequency adjustment based on radio frequency modulation. The ONU downstream coherent received intrinsic light is shared as upstream transmitted light, due to TEC control error, frequency deviation of delta f exists between the intrinsic light (transmitted light) and the required sub-band, and delta f passes through a coherent receiver at the downstream sub-band signalAfter detection, the frequency offset can be obtained by calculation through a frequency offset estimation algorithm of the DSP. In order to avoid aliasing of sub-band signals of different ONUs caused by frequency deviation of uplink sub-band modulation, radio frequency signal modulation is carried out on an electric domain modulation signal during uplink sub-band modulation, and delta f needs to be subtracted from the original radio frequency modulation frequency to compensate the influence of laser frequency deviation. I.e. the frequency f of the modulation₂＝f-f₁Δ f, f is the center frequency of the uplink sub-band, f₁Is the frequency at which light is emitted (intrinsic light).

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product.

The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website site, computer, server, or data center to another website site, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that a computer can store or a data storage device, such as a server, a data center, etc., that is integrated with one or more available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims

1. A signal transmission method of a passive optical network PON system, the method comprising:

an Optical Line Terminal (OLT) generates a downlink frequency division multiplexing electrical signal corresponding to a plurality of downlink sub-bands, wherein each downlink sub-band in the plurality of downlink sub-bands is not overlapped on a frequency domain, and each downlink sub-band corresponds to a group of Optical Network Units (ONU);

the OLT loads the downlink frequency division multiplexing electrical signal to the OLT to emit light to obtain a downlink frequency division multiplexing optical signal;

and the OLT sends the downlink frequency division multiplexing optical signal, so that the ONU, the frequency of which is the first frequency, of the ONU intrinsic light obtains a downlink sub-band signal corresponding to the ONU from the downlink frequency division multiplexing optical signal, wherein the first frequency corresponds to one downlink sub-band in the plurality of downlink sub-bands.

2. The method of claim 1, wherein generating, by the OLT, a downlink frequency-division multiplexed electrical signal corresponding to a plurality of downlink sub-bands comprises:

the OLT generates baseband signals corresponding to each ONU;

the OLT shapes the baseband signals through a low-pass filter to obtain target baseband signals corresponding to each ONU;

for each ONU, the OLT shifts the frequency of a target baseband signal corresponding to the ONU to obtain a downlink sub-band signal corresponding to the ONU on a downlink sub-band corresponding to the ONU;

and the OLT combines the downlink sub-band signals corresponding to the ONUs to obtain a downlink frequency division multiplexing electrical signal.

3. The method of claim 1, wherein generating the downlink frequency-division multiplexed electrical signal corresponding to the plurality of downlink sub-bands by the OLT comprises:

the OLT determines a target sub-band which is in an idle state or is not fully registered in a downlink sub-band corresponding to a Passive Optical Network (PON) system, wherein the downlink sub-band corresponding to the PON system is not overlapped on a frequency domain;

and the OLT transmits an inquiry message on the target sub-band and stops transmitting signals on other frequency bands except the target sub-band, so that the ONU determines the first frequency according to the inquiry message, and the target sub-band is a downlink sub-band corresponding to the ONU.

4. The method of claim 1, wherein generating the downlink frequency-division multiplexed electrical signal corresponding to the plurality of downlink sub-bands by the OLT comprises:

the OLT allocates a first sub-band as an uplink sub-band to the ONUs in the PON system and allocates a second sub-band as a downlink sub-band to the ONUs in the PON system, wherein the first sub-band and the second sub-band are adjacent in a frequency domain.

5. The method according to any one of claims 1 to 4, further comprising:

the OLT acquires each uplink sub-band electrical signal corresponding to an uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal, and the uplink frequency division multiplexing optical signal is a signal obtained by combining a plurality of uplink sub-band optical signals.

6. The method of claim 5, wherein the OLT emitted light and the OLT intrinsic light are light emitted by a same light source in the OLT.

7. A signal transmission method of a passive optical network PON system, the method comprising:

the ONU sets the frequency of the ONU intrinsic light to be a first frequency, and the first frequency corresponds to a target sub-frequency band;

the ONU obtains a downlink sub-band signal corresponding to the ONU from a downlink frequency division multiplexing optical signal through the ONU intrinsic light of the first frequency, where the downlink frequency division multiplexing optical signal is obtained by the OLT loading a downlink frequency division multiplexing electrical signal corresponding to a plurality of sub-bands onto the OLT emitting light, each of the plurality of downlink sub-bands is not overlapped in a frequency domain, and the plurality of downlink sub-bands include the target sub-band.

8. The method of claim 7, wherein before the ONU setting the frequency of the ONU intrinsic light to the first frequency, the method comprises:

the ONU adjusts the frequency of the ONU intrinsic light, and performs coherent detection on the ONU intrinsic light and an inquiry message sent by the OLT in a target sub-band aiming at the ONU intrinsic light of each frequency to determine coherent detection output power corresponding to each frequency;

and the ONU determines that the frequency corresponding to the maximum value in the coherent detection output power is the first frequency.

9. The method according to claim 7 or 8, characterized in that the method further comprises:

the ONU carries out frequency shift on a baseband signal to obtain an uplink sub-band electric signal corresponding to the ONU, and the central frequency of the uplink sub-band electric signal corresponds to an uplink sub-band distributed to the ONU by the OLT;

the ONU loads the uplink sub-band electrical signal to ONU emission light to obtain an uplink sub-band optical signal;

the ONU sends the uplink sub-band optical signals corresponding to the ONU so that the passive combiner combines the sub-band optical signals corresponding to the ONU with the uplink sub-band optical signals sent by other ONUs in the PON system to obtain uplink frequency division multiplexing optical signals, the OLT obtains each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signals through OLT intrinsic light of a second frequency, and the second frequency corresponds to the central frequency of the uplink frequency division multiplexing optical signals.

10. The method of claim 9, wherein the center frequency of the upstream sub-band electrical signal corresponding to the upstream sub-band allocated to the ONU by the OLT comprises:

center frequency f of the uplink sub-band electric signal₂＝f-f₁- Δ f, wherein f is the center frequency of the upstream sub-band allocated to the ONU by the OLT, and f₁And the delta f is a frequency offset value calculated by a frequency offset estimation algorithm according to the downlink sub-band electric signal.

11. The method of claim 9, wherein the ONU-emitting light and the ONU-intrinsic light are light emitted from a same light source in the ONU.

12. An optical line terminal, OLT, comprising:

the device comprises a generating module, a receiving module and a processing module, wherein the generating module is used for generating downlink frequency division multiplexing electric signals corresponding to a plurality of downlink sub-bands, each downlink sub-band in the plurality of downlink sub-bands is not overlapped on a frequency domain, and each downlink sub-band corresponds to a group of ONU;

the loading module is used for loading the downlink frequency division multiplexing electric signal to OLT emitting light to obtain a downlink frequency division multiplexing optical signal;

a sending module, configured to send the downlink frequency division multiplexing optical signal, so that an ONU with a frequency of ONU intrinsic light being a first frequency obtains a downlink sub-band signal corresponding to the ONU from the downlink frequency division multiplexing optical signal, where the first frequency corresponds to one of the plurality of downlink sub-bands.

13. The OLT of claim 12, wherein the generation module comprises:

14. The OLT of claim 12 or 13, wherein the OLT further comprises:

the receiving module is configured to obtain each uplink sub-band electrical signal corresponding to an uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, where the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal, and the uplink frequency division multiplexing optical signal is a signal obtained by combining a plurality of uplink sub-band optical signals.

15. The OLT of claim 14, wherein the OLT emission light and the OLT intrinsic light are light emitted from a same light source in the OLT.

16. An optical network unit, ONU, comprising:

the device comprises a setting module, a first frequency control module and a second frequency control module, wherein the setting module is used for setting the frequency of the ONU intrinsic light to be a first frequency, and the first frequency corresponds to a target sub-band;

a receiving module, configured to obtain, from a downlink frequency division multiplexing optical signal, a downlink sub-band signal corresponding to the ONU through the ONU intrinsic light at the first frequency, where the downlink frequency division multiplexing optical signal is obtained by the OLT loading, to the OLT, a downlink frequency division multiplexing electrical signal corresponding to a plurality of sub-bands, where each of the plurality of downlink sub-bands is not overlapped in a frequency domain, and the plurality of downlink sub-bands include the target sub-band.

17. The ONU of claim 16, wherein the ONU further comprises:

a frequency shift module, configured to perform frequency shift on a baseband signal to obtain an uplink sub-band electrical signal corresponding to the ONU, where a center frequency of the uplink sub-band electrical signal corresponds to an uplink sub-band allocated to the ONU by the OLT;

the loading module is used for loading the uplink sub-band electric signal to ONU emitted light to obtain an uplink sub-band optical signal;

a sending module, configured to send an uplink sub-band optical signal corresponding to the ONU, so that a passive combiner combines the sub-band optical signal corresponding to the ONU with uplink sub-band optical signals sent by other ONUs in the PON system to obtain an uplink frequency division multiplexing optical signal, where the OLT obtains each uplink sub-band electrical signal corresponding to the uplink frequency division multiplexing optical signal through OLT intrinsic light of a second frequency, and the second frequency corresponds to a center frequency of the uplink frequency division multiplexing optical signal.

18. The ONU of claim 17, wherein the center frequency of the upstream sub-band electrical signal corresponding to the upstream sub-band allocated to the ONU by the OLT comprises:

center frequency f of the uplink sub-band electric signal₂＝f-f₁- Δ f, wherein f is the center frequency of the upstream sub-band allocated to the ONU by the OLT, and f₁The frequency of light emitted for the ONU, Δ f is the electrical signal pass according to the downlink sub-bandAnd calculating the obtained frequency offset value by using an over-frequency offset estimation algorithm.

19. The ONU of claim 17, wherein the ONU-emitting light and the ONU-intrinsic light are light emitted from the same light source in the ONU.

20. A PON system comprising an OLT according to any of claims 12 to 15 and an ONU according to any of claims 16 to 19.