CN113765589B

CN113765589B - Terahertz wireless optical fiber expansion device and real-time transmission system thereof

Info

Publication number: CN113765589B
Application number: CN202111035635.1A
Authority: CN
Inventors: 朱敏; 张教; 李沁茹; 邹昱聪; 华炳昌; 蔡沅成; 雷明政; 李爱杰; 黄永明; 尤肖虎
Original assignee: Network Communication and Security Zijinshan Laboratory
Current assignee: Network Communication and Security Zijinshan Laboratory
Priority date: 2021-09-03
Filing date: 2021-09-03
Publication date: 2022-07-01
Anticipated expiration: 2041-09-03
Also published as: CN113765589A

Abstract

The invention relates to a terahertz wireless optical fiber expansion device and a real-time transmission system thereof, which comprise a second semiconductor laser, an optical heterodyne terahertz signal generation module, a first polarization multiplexing optical signal, a second polarization multiplexing optical signal and a third polarization multiplexing optical signal, wherein the optical heterodyne terahertz signal generation module is used for receiving the first polarization multiplexing optical signal in an optical fiber in a transmitting link, respectively polarizing and splitting the first optical local vibration signal and the first polarization multiplexing optical signal into two paths of orthogonal polarization state signals, and generating two paths of terahertz signals for wireless transmission in an optical heterodyne mode; and the intermediate frequency signal modulation module is used for down-converting the two paths of terahertz signals subjected to wireless transmission into two paths of intermediate frequency signals in a receiving link, generating a second optical carrier signal, modulating the two paths of intermediate frequency signals to two orthogonal polarization state signals of the second optical carrier signal respectively, combining the two orthogonal polarization state signals, generating a second polarization multiplexing optical signal, and sending the second polarization multiplexing optical signal to an optical fiber for transmission. Seamless interconnection between the optical fiber link and the terahertz wireless link is realized, the use of a large-working-bandwidth electric mixer and a high-frequency local oscillation source is avoided, and the flexibility of generating carrier frequency is enhanced.

Description

Terahertz wireless optical fiber expansion device and real-time transmission system thereof

Technical Field

The invention relates to the technical field of photon terahertz wireless communication, in particular to a terahertz wireless optical fiber expansion device and a real-time transmission system thereof.

Background

With the rapid development of B5G/6G communication technology, the demand of communication networks for transmission rate, data capacity, etc. is increasing in the future. Not only the data transmission rate of the bits per second is taken as a target, but also the network architecture coverage is expanded and a plurality of application scenes are supported, which puts higher requirements on the development of the next generation access technology.

The traditional optical fiber communication is not the second choice for establishing a data transmission network with super-large capacity, super-long distance, super-high speed and super-wide coverage range by the characteristics of super-wide frequency spectrum bandwidth, low loss, small electromagnetic interference and the like. However, some rural areas and remote areas face the problems of severe environment, severe terrain and the like, so that the optical fiber deployment is difficult to implement, expensive in cost and often impossible to implement. In order to solve the problem, a fiber-optic wireless fusion technology is provided. The optical fiber wireless fusion technology integrates the advantages of convenience of wireless communication, large capacity and ultra-long distance of an optical fiber link and the like, the coverage range of an optical fiber communication network is expanded by connecting the wireless link with the optical fiber link, and the problem of difficulty in optical fiber deployment in partial areas can be effectively solved. Considering that the currently commonly used 60GHz low-frequency band resource is seriously insufficient and cannot meet the requirements of higher transmission rate and larger bandwidth, a wireless link matched with the transmission capability of an optical fiber link needs to be developed.

Terahertz wireless communication, namely wireless communication with a carrier frequency band of 0.1THz-10THz, is expected to have transmission capability comparable to that of an optical fiber by providing link throughput of hundreds of Gb/s and even Tb/s due to higher carrier frequency and larger bandwidth, provides possibility for realizing a transmission system in which the optical fiber is seamlessly connected with the terahertz wireless link, and has been deeply researched by academia at present. Recently, a series of experiments verify the feasibility of the seamless connection transmission system of the optical fiber and the terahertz wireless link. The method adopts high-order QAM modulation, various multidimensional multiplexing technologies and an advanced offline digital signal processing technology, and can maximally realize the transmission capacity larger than 1 Tb/s. However, according to reported experiments, on one hand, the existing fiber terahertz wireless fusion system basically adopts an offline signal processing scheme, and signal processing and transmission are not performed synchronously, so that the system is difficult to apply to an actual communication scene, and meanwhile, the transmission rate which can be achieved by a few real-time transmission schemes is greatly reduced compared with that of the offline scheme; on the other hand, most of the existing schemes realize the generation and reception of terahertz wireless signals based on a full-electric mode, wherein the terahertz carrier wave in a transmitting link is generally multiplied by a radio frequency local oscillator, so that the requirements on the working range of electronic devices such as a local oscillator source and a mixer are higher, and the upper limit and the flexibility of the carrier frequency of the generated terahertz carrier wave are also limited. Therefore, a new system architecture for seamless interconnection of the terahertz wireless technology and the optical fiber network is needed to be explored for the above problems.

Disclosure of Invention

Aiming at the problems, the invention provides a terahertz wireless optical fiber expansion device and a real-time transmission system thereof, and solves the problems that the upper limit and the flexibility of the generated terahertz carrier frequency are limited due to high requirements on the working range of devices in a full-electric mode, and a real-time transmission scheme is lacked in the existing optical fiber terahertz wireless transmission system.

The invention provides a terahertz wireless optical fiber expansion device, which comprises:

a second semiconductor laser for generating a first optical local oscillator signal and a second optical carrier signal;

the optical heterodyne terahertz signal generating module is used for receiving a first polarization multiplexing optical signal in an optical fiber in a transmitting link, respectively polarizing and splitting the first optical local vibration signal and the first polarization multiplexing optical signal into two orthogonal polarization state signals, and generating two terahertz signals for wireless transmission in an optical heterodyne mode;

and the intermediate frequency signal modulation module is used for down-converting the two paths of received terahertz signals subjected to wireless transmission into two paths of intermediate frequency signals in a receiving link, modulating the two paths of intermediate frequency signals to two orthogonal polarization state signals of the second optical carrier signal respectively, combining the two orthogonal polarization state signals, generating a second polarization multiplexing optical signal, and sending the second polarization multiplexing optical signal to an optical fiber for transmission.

Further, the optical heterodyne terahertz signal generating module includes:

the input end of the optical attenuator is connected with an optical fiber and is used for controlling the transmission optical power of the first polarization multiplexing optical signal in real time;

the input end of the first polarization maintaining beam splitter is connected with the output end of the optical attenuator and is used for polarization beam splitting of the first polarization multiplexing optical signal into two orthogonal polarization state signals;

the input end of the polarization controller is connected with the output end of the second semiconductor laser and is used for adjusting the polarization direction of the first light local oscillation signal;

the input end of the second polarization maintaining beam splitter is connected with the output end of the polarization controller and is used for polarization beam splitting of the first light local oscillation signal into two paths of orthogonal polarization state signals;

the first input end of the first optical coupler is connected with the first output end of the first polarization maintaining beam splitter, and the second input end of the first optical coupler is connected with the first output end of the second polarization maintaining beam splitter and is used for coupling the first polarization multiplexing optical signal and one polarization state signal of the first optical local oscillation signal;

a second optical coupler, wherein a first input end of the second optical coupler is connected with a second output end of the second polarization maintaining beam splitter, and a second input end of the second optical coupler is connected with a second output end of the first polarization maintaining beam splitter, and the second optical coupler is used for coupling the other polarization state signal of the first polarization multiplexing optical signal and the first optical local oscillation signal;

the input end of the first photodiode is connected with the output end of the first optical coupler and used for generating a first path of terahertz signal through optical heterodyne mode beat frequency;

and the input end of the second photodiode is connected with the output end of the second optical coupler and is used for generating a second path of terahertz signal in a beat frequency mode in an optical heterodyne mode.

Further, the intermediate frequency signal modulation module includes:

the radio frequency local oscillation source is used for generating a first radio frequency local oscillation signal;

the input end of the frequency multiplier is connected with the output end of the radio frequency local oscillation source and is used for multiplying the frequency of the first radio frequency local oscillation signal to a terahertz frequency band;

the input end I of the first mixer is used for acquiring a first path of terahertz signals, and the input end II of the first mixer is connected with the output end of the frequency multiplier and is used for down-converting the acquired first path of terahertz signals to a first path of intermediate frequency signals;

the input end I of the second mixer is used for acquiring a second path of terahertz signals, and the input end II of the second mixer is connected with the output end of the frequency multiplier and is used for down-converting the acquired second path of terahertz signals to a second path of intermediate frequency signals;

the input end of the first low-noise amplifier is connected with the output end of the first mixer and used for realizing the amplification of the first path of intermediate frequency signal;

the input end of the second low-noise amplifier is connected with the output end of the second mixer and used for realizing the amplification of a second path of intermediate frequency signals;

the input end of the third polarization maintaining beam splitter is connected with the output end of the second semiconductor laser and is used for polarization beam splitting of the second optical carrier signal into two paths of orthogonal polarization state signals;

a driving signal input end of the first modulator is connected with an output end of the first low noise amplifier, and an optical signal input end of the first modulator is connected with a first output end of the third polarization maintaining beam splitter and is used for modulating a first path of intermediate frequency signal to a first path of polarization state signal of the second optical carrier signal to obtain an optical modulation signal in a first polarization direction;

a driving signal input end of the second modulator is connected with an output end of the second low-noise amplifier, and an optical signal input end of the second modulator is connected with a second output end of the third polarization maintaining beam splitter and is used for modulating a second path of intermediate frequency signal to a second path of polarization state signal of the second optical carrier signal to obtain an optical modulation signal in a second polarization direction;

a polarization maintaining optical coupler, a first input end of the polarization maintaining optical coupler being connected to an output end of the first modulator, and a second input end of the polarization maintaining optical coupler being connected to an output end of the second modulator, for coupling the first and second polarization direction optical modulation signals to generate the second polarization multiplexing optical signal;

the input end of the second optical fiber amplifier is connected with the output end of the polarization-maintaining optical coupler and is used for amplifying the second polarization multiplexing optical signal;

and the input end of the tunable optical filter is connected with the output end of the second optical fiber amplifier and is used for filtering part of sidebands and optical carriers of the second polarization multiplexing optical signal.

A real-time transmission system based on any one of the terahertz wireless optical fiber expansion devices comprises: at least one group of real-time coherent light receiving and transmitting modules, the terahertz wireless optical fiber expansion device and the wireless receiving and transmitting modules are sequentially connected; the real-time coherent light transceiver module is arranged at a user side, and the terahertz wireless optical fiber expansion device and the wireless transceiver module are arranged at a bridge joint of optical fibers and wireless;

the real-time coherent optical transceiver module is used for receiving a data stream from a user side and generating a first optical carrier signal in a transmitting link, modulating the data stream onto the first optical carrier signal in a coherent modulation mode in real time and realizing polarization multiplexing to generate a first polarization multiplexing optical signal, and transmitting the first polarization multiplexing optical signal to the terahertz wireless optical fiber expansion device through an optical fiber; in a receiving link, the receiving link is used for receiving a second polarization multiplexing optical signal from the terahertz wireless optical fiber expansion device through an optical fiber and generating a second optical local oscillation signal, and the second polarization multiplexing optical signal is subjected to coherent detection in real time through the second optical local oscillation signal to recover a user side data stream;

the wireless transceiving module is used for wirelessly transmitting two paths of terahertz signals from the terahertz wireless optical fiber expansion device in a transmitting link; and the receiving link is used for receiving two paths of terahertz signals in a wireless mode and sending the terahertz signals to the terahertz wireless optical fiber expansion device.

Further, the real-time coherent optical transceiver module includes: a coherent optical modem and a first fiber amplifier;

the data interface of the coherent optical modem is connected with a user side, and the optical signal input end is connected with the optical signal output end of the terahertz wireless optical fiber expansion device through an optical fiber; in a transmitting link, the receiving unit is configured to receive a data stream from a user side and generate a first optical carrier, and perform coherent modulation and polarization multiplexing on the first optical carrier in real time to obtain a first polarization multiplexing optical signal; in the receiving link, the receiving link is configured to generate a second optical local oscillation signal, perform coherent detection on the second polarization multiplexing optical signal in real time, and recover a data stream of the user side;

the input end of the first optical fiber amplifier is connected with the optical signal output end of the coherent optical modem and is used for amplifying the first polarization multiplexing optical signal in a transmitting link.

Further, the coherent optical modem comprises:

a first semiconductor laser for generating the first optical carrier signal and the second optical local oscillator signal;

the optical signal polarization multiplexing coherent modulation module is used for receiving a data stream of a user side, processing the data stream into a baseband electric signal, modulating the processed baseband electric signal to the first optical carrier in a coherent modulation mode in real time, realizing polarization multiplexing and generating a first polarization multiplexing optical signal;

the polarization multiplexing optical signal coherent demodulation module is configured to implement coherent detection and signal processing on the second polarization multiplexing optical signal and the second optical local oscillation signal in real time, and recover a data stream of the user side;

the first semiconductor laser is respectively connected with the optical signal polarization multiplexing coherent modulation module and the polarization multiplexing optical signal coherent demodulation module.

Further, the optical signal polarization multiplexing coherent modulation module includes:

the transmitter digital signal processing module is used for receiving a data stream from a user side and carrying out digital signal processing to obtain a baseband digital signal;

the input ends of the digital-to-analog converters are connected with the output end of the transmitter digital signal processing module and are used for respectively performing digital-to-analog conversion on the baseband digital signals to obtain baseband electric signals;

the input ends of the four first electric amplifiers are respectively connected with the output ends of the four digital-to-analog converters and are used for amplifying the baseband electric signals;

and the polarization multiplexing I/Q modulator is driven by four paths of amplified baseband electric signals, and an optical signal input end is connected with the output end of the first semiconductor laser and used for modulating the baseband electric signals onto the first optical carrier in a coherent modulation mode and realizing polarization multiplexing to obtain the first polarization multiplexing optical signal.

Further, the coherent demodulation module for polarization-multiplexed optical signals includes:

an optical signal input end of the polarization multiplexing coherent receiver is connected with an output end of the first semiconductor laser, and is used for realizing coherent demodulation and depolarization multiplexing of a second polarization multiplexing optical signal and recovering four-path baseband electric signals of the same-direction component and the orthogonal component corresponding to two polarization components of the second polarization multiplexing optical signal;

the input ends of the second electrical amplifiers are connected with the output end of the polarization multiplexing coherent receiver and are used for amplifying the baseband electric signals output by the polarization multiplexing coherent receiver;

the input ends of the four analog-to-digital converters are connected with the output end of the second electrical amplifier and are used for performing analog-to-digital conversion on the baseband electrical signal so as to recover a baseband digital signal;

and the receiver digital signal processing module is connected with the output ends of the four analog-to-digital converters and is used for carrying out digital signal processing on the baseband digital signals so as to recover the user side data stream.

Further, the wireless transceiver module includes:

the first transmitting antenna is used for radiating the first path of terahertz signal output by the terahertz wireless optical fiber expansion device to a free space;

the second transmitting antenna is used for radiating the second path of terahertz signals output by the terahertz wireless optical fiber expansion device to a free space;

the first receiving antenna is used for receiving a first path of wireless terahertz signal transmitted in a wireless mode;

and the second receiving antenna is used for receiving the second path of wireless terahertz signal transmitted in a wireless mode.

Furthermore, when only one group of real-time coherent light transceiving module, the terahertz wireless optical fiber expansion device and the wireless transceiving module are provided, two paths of terahertz signals transmitted by the wireless transceiving module are reflected back to the wireless transceiving module through the intelligent reflecting surface.

The invention has the technical effects that:

the terahertz wireless optical fiber expansion device realizes seamless interconnection of the optical fiber link and the terahertz wireless link, and allows the terahertz wireless optical fiber expansion device to bypass areas where optical fibers are difficult or expensive to deploy when a transmission system is built, so that the coverage range of the traditional optical fiber transmission system is expanded, and the terahertz wireless optical fiber expansion device is expected to be widely applied to front and back return links among 5G base stations;

the terahertz wireless optical fiber expansion device generates a first optical local oscillation signal, polarizes and splits the first optical local oscillation signal and the first polarization multiplexing optical signal into two orthogonal polarization state signals respectively, and generates a terahertz signal in an optical heterodyne mode.

The invention discloses a real-time transmission system based on a terahertz wireless optical fiber expansion device, which comprises: the terahertz wireless optical fiber expanding device comprises at least one group of real-time coherent light transceiving modules, a terahertz wireless optical fiber expanding device and a wireless transceiving module; the real-time coherent light receiving and transmitting modules are arranged at the user side, and the terahertz wireless optical fiber expansion device and the wireless receiving and transmitting modules are arranged at the bridging position of the optical fiber and the wireless optical fiber;

the real-time coherent optical transceiver module receives a data stream from a user terminal in a transmitting link and generates a first optical carrier signal, modulates the data stream onto the first optical carrier signal in a coherent modulation mode in real time and realizes polarization multiplexing, generates a first polarization multiplexing optical signal, can realize real-time processing of a transmission signal, can be directly applied to an actual transmission scene, and supports a transmission rate of hundreds of Gb/s; moreover, a coherent modulation mode is adopted, so that the method can adapt to modulation signals of various formats, avoids the limitation of incoherent modulation caused by a bandwidth-limited device, and has better noise filtering capability;

the real-time transmission system can realize full-duplex communication and self-sending and self-receiving, effectively enlarges the capacity of the optical fiber transmission system, can obviously reduce the transmission cost and enables the system to be more economic and efficient.

Drawings

FIG. 1 is a schematic block diagram of a terahertz wireless optical fiber expansion apparatus according to an embodiment of the present invention;

fig. 2 is a block diagram of a real-time transmission system according to an embodiment of the invention;

FIG. 3 is a schematic block diagram of a real-time transmission system according to an embodiment of the invention;

fig. 4 is a block diagram of a real-time transmission system according to an embodiment of the present invention;

FIG. 5 is a block diagram of a coherent optical modem according to an embodiment of the present invention;

fig. 6 is a block diagram of a real-time transmission system according to an embodiment of the present invention;

fig. 7 is a block diagram of a specific structure of an uplink and a downlink of a real-time transmission system in the embodiment of the present invention;

the reference numbers illustrate: real-time coherent light transceiver modules 1 and 6; coherent optical modems 11 and 61; fiber amplifiers 12, 62, 2b11, 5a 11; terahertz wireless optical fiber expansion devices 2 and 5; optical heterodyne terahertz signal generation modules 2a and 5 b; optical attenuators 2a1, 5b 1; polarization maintaining beam splitters 2a2, 2a3, 2b7, 5b2, 5b3, 5a 7; semiconductor lasers 2a4, 5b 4; optical couplers 2a6, 2a7, 5b6, 5b 7; photodiodes 2a8, 2a9, 5b8, 5b 9; wireless transceiver modules 3, 4; the transmitting antennas 31, 32, 43, 44; receiving antennas 33, 34, 41, 42; radio frequency local oscillation sources 2b1, 5a 1; frequency multipliers 2b2, 5a 2; mixers 2b3, 2b4, 5a3, 5a 4; low noise amplifiers 2b5, 2b6, 5a5, 5a 6; phase modulators 2b8, 2b9, 5a8, 5a 9; polarization maintaining optical couplers 2b10, 5a 10; tunable optical filters 2b12, 5a 12; and an intelligent reflecting surface 7.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In describing positional relationships, unless otherwise specified, when an element such as a layer, film or substrate is referred to as being "on" another layer, it can be directly on the other layer or intervening layers may also be present. Further, when a layer is referred to as being "under" another layer, it can be directly under, or one or more intervening layers may also be present. It will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

Where the terms "comprising," "having," and "including" are used herein, another element may be added unless an explicit limitation is used, such as "only," "consisting of … …," etc. Unless mentioned to the contrary, singular terms may include the plural and are not to be construed as being one in number.

As shown in fig. 1, in an embodiment of the present application, there is provided a terahertz wireless optical fiber extension apparatus, including:

the optical heterodyne terahertz signal generating module is used for receiving a first polarization multiplexing optical signal in an optical fiber in a transmitting link, respectively polarizing and splitting the first optical local vibration signal and the first polarization multiplexing optical signal into two orthogonal polarization state signals, and generating two terahertz signals for wireless transmission in an optical heterodyne manner;

and the intermediate frequency signal modulation module is used for down-converting the two paths of received terahertz signals subjected to wireless transmission into two paths of intermediate frequency signals in a receiving link, generating a second optical carrier signal, modulating the two paths of intermediate frequency signals to two orthogonal polarization state signals of the second optical carrier signal respectively, combining the two orthogonal polarization state signals, generating a second polarization multiplexing optical signal, and sending the second polarization multiplexing optical signal to an optical fiber for transmission.

As shown in fig. 4, in one embodiment, the optical heterodyne terahertz signal generating module includes: a light attenuator (VOA), a polarization maintaining beam splitter 1 (PBS, i.e., a first polarization maintaining beam splitter), a Polarization Controller (PC), a polarization maintaining beam splitter 2 (i.e., a second polarization maintaining beam splitter), an optical coupler 1 (OC, i.e., a first optical coupler), an optical coupler 2 (i.e., a second optical coupler), a photodiode 1 (UTC-PD, i.e., a first photodiode), and a photodiode 2 (i.e., a second photodiode).

The input end of the optical attenuator is connected with an optical fiber, and is connected with the output end of an optical fiber amplifier 1 in the real-time coherent light transceiving module through the optical fiber, and the optical attenuator is used for controlling the transmission optical power of the first polarization multiplexing optical signal in real time; the input end of the polarization maintaining beam splitter 1 is connected with the output end of the optical attenuator and is used for polarization beam splitting of the first polarization multiplexing optical signal into two paths of orthogonal X and Y polarization state signals; the input end of the polarization controller is connected with the output end of the second semiconductor laser and is used for adjusting the polarization direction of the first light local oscillation signal to match with the subsequent polarization beam splitting; the input end of the polarization maintaining beam splitter 2 is connected with the output end of the polarization controller and is used for polarization beam splitting of the first light local oscillation signal into two paths of orthogonal X and Y polarization state signals; the first input end of the optical coupler 1 is connected with the first output end of the polarization maintaining beam splitter 1, and the second input end of the optical coupler 1 is connected with the first output end of the polarization maintaining beam splitter 2 and is used for coupling the first polarization multiplexing optical signal and the X polarization state signal of the first optical local oscillation signal; the first input end of the optical coupler 2 is connected with the second output end of the polarization maintaining beam splitter 2, and the second input end of the optical coupler 2 is connected with the second output end of the polarization maintaining beam splitter 1 and is used for coupling the first polarization multiplexing optical signal and the Y polarization state signal of the first optical local polarization signal; the input end of the photodiode 1 is connected with the output end of the optical coupler 1 and used for generating a terahertz signal in the X polarization direction in a light heterodyne mode; the input end of the photodiode 2 is connected with the output end of the optical coupler 2 and is used for generating a terahertz signal in the Y polarization direction in a light heterodyne mode;

for a transmitting link, after the first polarization multiplexing optical signal is transmitted by an optical fiber, real-time power control is performed through the optical attenuator, and the first polarization multiplexing optical signal is decomposed into orthogonal X and Y polarization state signals by the polarization maintaining beam splitter 1 and is respectively coupled with the first optical local oscillation signal. Wherein the first optical local oscillation signal is generated by the second semiconductor laser at a wavelength of

And the continuous light wave and the first polarization multiplexing optical signal have a frequency difference of terahertz, wherein the frequency difference can be 280GHz, 320GHz and 340GHz, and the polarization direction of the continuous light wave and the first polarization multiplexing optical signal is controlled by the polarization controller. In order to realize the subsequent simultaneous beat frequency in two polarization directions, after the polarization states of the first optical local oscillation signal are separated, the optical coupler 1 and the optical coupler 2 are respectively coupled with two orthogonal polarization states of the first polarization multiplexing optical signal. And then, the beat frequency of the photodiode 1 and the photodiode 2 is converted into two paths of terahertz signals, and the two paths of terahertz signals are sent to the wireless transceiving module to realize wireless transmission.

As shown in fig. 4, in one embodiment, the intermediate frequency signal modulation module includes: the device comprises a radio frequency local oscillator, a frequency multiplier, a mixer 1 (namely a first mixer), a mixer 2 (namely a second mixer), a low noise amplifier 1 (namely a first low noise amplifier), a low noise amplifier 2 (namely a second low noise amplifier), a polarization maintaining beam splitter 3 (namely a third polarization maintaining beam splitter), a modulator 1 (first modulator), a modulator 2 (second modulator), a polarization maintaining optical coupler, an optical fiber amplifier 2 (namely a second optical fiber amplifier) and a tunable optical filter.

The radio frequency local oscillation source is used for generating a first radio frequency local oscillation signal; the input end of the frequency multiplier is connected with the output end of the radio frequency local oscillation source and is used for multiplying the frequency of the first radio frequency local oscillation signal to a terahertz frequency band to obtain a terahertz signal; the first input end of the frequency mixer 1 is connected with the output end of a first receiving antenna of the wireless transceiving module and used for acquiring a first path of terahertz signal, and the second input end of the frequency mixer is connected with the output end of the frequency multiplier and used for down-converting the terahertz signal in the X polarization direction (namely the acquired first path of terahertz signal) to a first path of intermediate frequency signal; the input end I of the frequency mixer 2 is connected with the output end of a second receiving antenna of the wireless transceiving module and is used for acquiring a second path of terahertz signal, and the input end II of the frequency mixer is connected with the output end of the frequency multiplier and is used for down-converting the terahertz signal in the Y polarization direction (namely the acquired second path of terahertz signal) to an intermediate frequency signal; the input end of the low noise amplifier 1 is connected with the output end of the mixer 1 and is used for amplifying the intermediate frequency signal in the X polarization direction; the input end of the low noise amplifier 2 is connected with the output end of the mixer 2 and is used for amplifying the intermediate frequency signal in the Y polarization direction; the input end of the polarization maintaining beam splitter 3 is connected with the output end of the second semiconductor laser and is used for polarization beam splitting of the second optical carrier signal into two orthogonal polarization state signals (namely, X and Y polarization state signals); a driving signal input end of the modulator 1 is connected to an output end of the low noise amplifier 1, and an optical signal input end is connected to the first output end of the polarization maintaining beam splitter 3, and is configured to modulate the intermediate frequency signal in the X polarization direction onto the X polarization state signal of the second optical carrier signal, so as to obtain an optical modulation signal in the X polarization direction (i.e., an optical modulation signal in the first polarization direction); a driving signal input end of the modulator 2 is connected with an output end of the low noise amplifier 2, and an optical signal input end is connected with a second output end of the polarization maintaining beam splitter 3, and is configured to modulate the intermediate frequency signal in the Y polarization direction onto the Y polarization state signal of the second optical carrier signal, so as to obtain an optical modulation signal in the Y polarization direction (i.e., an optical modulation signal in the second polarization direction); the input end I of the polarization-maintaining optical coupler is connected with the output end of the modulator 1, and the input end II of the polarization-maintaining optical coupler is connected with the output end of the modulator 2, and is used for coupling the optical modulation signals in the X and Y polarization directions to generate a second polarization multiplexing optical signal; the input end of the optical fiber amplifier 2 is connected with the output end of the polarization-maintaining optical coupler and is used for amplifying the second polarization multiplexing optical signal so as to compensate modulation loss and insertion loss; the input end of the tunable optical filter is connected with the output end of the optical fiber amplifier 2, and is used for filtering out higher sideband, optical carrier and spontaneous radiation noise of the second polarization multiplexing optical signal, and for subsequent coherent signal detection.

Aiming at a receiving link, X and Y terahertz signals from a wireless transceiving module are respectively mixed with terahertz local oscillation signals through the frequency mixer 1 and the frequency mixer 2 and are down-converted to intermediate frequency. In order to generate a required terahertz local oscillation signal, the radio frequency local oscillation source provides a radio frequency local oscillation signal, and the terahertz local oscillation signal is obtained after frequency multiplication on the frequency multiplier. The frequency multiplier may be selected arbitrarily according to the frequency of the radio frequency local oscillation source, and for example, when the frequency of the radio frequency local oscillation source is 30GHz, a frequency multiplier 10 may be used, and when the frequency of the radio frequency local oscillation source is 10GHz, a frequency multiplier 36 may be used. Meanwhile, the power amplification is carried out on the intermediate frequency signals of the X path and the Y path so as to compensate the space transmission loss. Subsequently, the modulator 1 and the modulator 2 modulate the two paths of intermediate frequency signals onto two paths of polarization states of the second optical carrier, respectively, to form optical carrier intermediate frequency signals in X and Y polarization states. Wherein the second optical carrier is generated by the second semiconductor laser with a wavelength of

The continuous light wave is split by the polarization maintaining beam splitter 3 and sent to the modulator 1 and the modulator 2. Two paths of optical carrier intermediate frequency signals are combined into one path of optical carrier by the polarization-maintaining optical couplerAn intermediate frequency signal, i.e. said second polarization multiplexed optical signal. And after the second polarization multiplexing optical signal is amplified and filtered by the optical fiber amplifier 2 and the tunable optical filter, a higher signal sideband, an optical carrier and spontaneous emission noise are suppressed and are transmitted to a standard single-mode optical fiber for transmission.

As shown in fig. 2 and fig. 3, in an embodiment of the present application, there is provided a real-time transmission system based on the terahertz wireless optical fiber extension apparatus described in any one of the above embodiments, including: at least one group of real-time coherent light receiving and transmitting modules, the terahertz wireless optical fiber expansion device and the wireless receiving and transmitting modules are sequentially connected; the real-time coherent light transceiver module is arranged at a user side, and the terahertz wireless optical fiber expansion device and the wireless transceiver module are arranged at a bridge joint of optical fibers and wireless;

the real-time coherent optical transceiver module is used for receiving a data stream from a user side and generating a first optical carrier signal in a transmitting link, modulating the data stream onto the first optical carrier signal in a coherent modulation mode in real time and realizing polarization multiplexing to generate a first polarization multiplexing optical signal, and transmitting the first polarization multiplexing optical signal to the terahertz wireless optical fiber expansion device through an optical fiber; in the receiving link, the terahertz wireless optical fiber expansion device is used for receiving a second polarization multiplexing optical signal from the terahertz wireless optical fiber expansion device through an optical fiber and generating a second optical local oscillation signal, and the second polarization multiplexing optical signal is subjected to coherent detection in real time through the second optical local oscillation signal to recover the user side data stream;

the wireless transceiving module is used for wirelessly transmitting two paths of terahertz signals from the terahertz wireless optical fiber expansion device in a transmitting link; and the receiving link is used for receiving the two paths of terahertz signals in a wireless mode and sending the terahertz signals to the terahertz wireless optical fiber expansion device.

In the real-time transmission system based on the terahertz wireless optical fiber extension device provided by the embodiment of the invention, the first optical carrier is generated by the real-time coherent optical transceiver module, the data stream of the user side is modulated onto the first optical carrier in a coherent manner, meanwhile, polarization multiplexing is carried out to realize that the transmission capacity is doubled (the polarization state of light is two, each polarization state can independently modulate data, and the transmission capacity of the two polarization states can be doubled), and the first polarization multiplexing optical signal is generated in real time. And finally, in order to compensate for modulation loss and insertion loss, the first polarization multiplexing optical signal is amplified and then sent to a Standard Single Mode Fiber (SSMF) for transmission. The invention can realize the real-time processing of the transmission signals, can be directly applied to the actual transmission scene and supports the transmission rate of hundreds of Gb/s; moreover, a coherent modulation mode is adopted, so that the method can adapt to modulation signals of various formats, avoids the limitation of incoherent modulation caused by a bandwidth-limited device, and has better noise filtering capability;

the first polarization multiplexing optical signal is transmitted to the terahertz wireless extension device through an optical fiber, is decomposed into two orthogonal polarization state signals (namely, the polarization beam is split into an X polarization component and a Y polarization component) after power is attenuated, and is respectively subjected to beat frequency with the two orthogonal polarization state signals of the first polarization local oscillation signal after the same polarization beam is split (namely, two terahertz signals are generated in an optical heterodyne manner), wherein the frequency difference between the first polarization local oscillation signal and the first polarization multiplexing optical signal is terahertz. And finally, generating two paths of terahertz signals after beat frequency, and sending the two paths of terahertz signals to the wireless transceiving module to realize wireless transmission.

And the two paths of wireless terahertz signals after wireless transmission are received by the wireless transceiving modules in the same group or other groups and are sent back to the terahertz wireless optical fiber expansion devices in the corresponding groups. The two terahertz signals are respectively mixed with a first radio frequency local oscillator signal which is generated by the terahertz wireless optical fiber expansion device and subjected to frequency multiplication through the terahertz wireless optical fiber expansion device, the frequency is converted into two intermediate frequency signals through down conversion, and meanwhile power amplification is carried out to compensate atmospheric loss caused by wireless transmission. Then, the two paths of intermediate frequency signals are respectively modulated onto two paths of orthogonal polarization states (i.e., X and Y polarization states) of the second optical carrier signal, and are combined into one path of optical carrier intermediate frequency signal, i.e., the second polarization multiplexing optical signal. And after the second polarization multiplexing optical signal is amplified and filtered, part of sideband and optical carrier of the signal are suppressed, and then the signal is sent into a standard single-mode optical fiber to be transmitted back to the real-time coherent light transceiver module.

And the second polarization multiplexing optical signal realizes real-time coherent demodulation and depolarization multiplexing through the real-time coherent optical transceiver modules in the corresponding groups, and recovers the data stream of the user side.

As shown in fig. 2, when there is only one set of real-time coherent light transceiver module, the terahertz wireless optical fiber extension device and the wireless transceiver module, self-sending and self-receiving can be realized; the two paths of terahertz signals transmitted by the wireless transceiver module are reflected by the intelligent reflecting surface, and then the two paths of wireless terahertz signals transmitted in the same group are received by the wireless transceiver module.

As shown in fig. 3, when two sets of real-time coherent optical transceiver modules, the terahertz wireless optical fiber extension device and the wireless transceiver module are provided, full-duplex transmission of signals between two user sides can be realized.

As shown in fig. 4, in one embodiment, the real-time coherent optical transceiver module includes: a coherent optical modem and a fiber amplifier 1 (i.e., a first fiber amplifier);

the data interface of the coherent optical modem is connected with a user side, and the optical signal input end is connected with the optical signal output end of the terahertz wireless optical fiber expansion device through an optical fiber; in a transmitting link, the receiving unit is configured to receive a data stream from a user side and generate a first optical carrier signal, and perform coherent modulation and polarization multiplexing on the first optical carrier signal in real time to obtain a first polarization multiplexing optical signal; in a receiving link, the receiving link is configured to generate a second optical local oscillation signal, perform coherent detection on the second polarization multiplexing optical signal in real time, and recover a data stream of the user end;

the input end of the first optical fiber amplifier is connected with the optical signal output end of the coherent optical modem and is used for amplifying the first polarization multiplexing optical signal in a transmitting link so as to compensate modulation loss and insertion loss; the output end of the optical fiber amplifier 1 is connected with the optical signal input end of the terahertz wireless optical fiber expansion device through an optical fiber;

in particular, in one embodiment, as shown in fig. 5, the coherent optical modem comprises: the device comprises a first semiconductor laser (EA), an optical signal polarization multiplexing coherent modulation module and a polarization multiplexing optical signal coherent demodulation module.

The first semiconductor laser is used for generating the first optical carrier and the second optical local oscillation signal; the first semiconductor laser is respectively connected with the optical signal polarization multiplexing coherent modulation module and the polarization multiplexing optical signal coherent demodulation module;

the optical signal polarization multiplexing coherent modulation module is used for receiving a data stream of a user end, processing a digital signal into a baseband electric signal, modulating the processed baseband electric signal to the first optical carrier in a coherent modulation mode in real time, realizing polarization multiplexing and generating the first polarization multiplexing optical signal in real time;

the polarization multiplexing optical signal coherent demodulation module is configured to implement coherent detection and digital signal processing of the second polarization multiplexing optical signal and the second optical local oscillation signal, and recover a data stream of the user end in real time;

the first semiconductor laser can be shared by the optical signal polarization multiplexing coherent modulation module and the polarization multiplexing optical signal coherent demodulation module.

Specifically, the optical signal polarization multiplexing coherent modulation module includes: a transmitter Digital Signal Processing (DSP) module, four digital-to-analog converters (DACs), four first electrical amplifiers, and a polarization-multiplexed I/Q modulator (DP-IQMm). The digital signal processing module of the transmitter is used for receiving the data stream from the user interface and carrying out digital signal processing to obtain four paths of baseband digital signals; the input ends of the four digital-to-analog converters are connected with the output end of the transmitter digital signal processing module and are used for respectively performing digital-to-analog conversion on the four paths of baseband digital signals to obtain four paths of baseband electric signals corresponding to the same-direction and orthogonal components (I/Q) of two polarization components (X/Y) of the first polarization multiplexing optical signal; the input ends of the four first electrical amplifiers are respectively connected with the output ends of the four digital-to-analog converters and are used for amplifying the four baseband electrical signals; the input end of the polarization multiplexing I/Q modulator is connected with the output ends of the four amplifiers, the polarization multiplexing I/Q modulator is driven by the four paths of amplified baseband electric signals, the optical signal input end of the polarization multiplexing I/Q modulator is connected with the output end of the first semiconductor laser, and the polarization multiplexing I/Q modulator is used for modulating the four paths of amplified baseband electric signals onto the first optical carrier signal in a coherent modulation mode and realizing polarization multiplexing so as to obtain the first polarization multiplexing optical signal.

Specifically, the polarization-multiplexed optical signal coherent demodulation module includes: the system comprises a polarization multiplexing coherent receiver (DP-CoRx), four second electrical amplifiers, four analog-to-digital converters (ADCs) and a receiver digital signal processing module. An optical signal input end of the polarization multiplexing coherent receiver is connected with an output end of the first semiconductor laser and is used for realizing coherent demodulation and depolarization multiplexing of the second polarization multiplexing optical signal and recovering four-path baseband electric signals of a homodromous component (I/Q) and an orthogonal component (I/Q) corresponding to two polarization components (X/Y) of the second polarization multiplexing optical signal; the input ends of the four second electrical amplifiers are connected with the output end of the polarization multiplexing coherent receiver and are used for amplifying the four baseband electrical signals and compensating insertion loss; the input ends of the four analog-to-digital converters are respectively connected with the output ends of the four second electrical amplifiers and are used for performing analog-to-digital conversion on the four baseband electric signals so as to recover four baseband digital signals; and the receiver digital signal processing module is connected with the output ends of the four analog-to-digital converters and is used for carrying out digital signal processing on the four paths of baseband digital signals so as to recover the data stream of the user side.

For a transmission link, the first semiconductor laser generates a wavelength of

The continuous lightwave as the first optical carrier signal, after the data stream from the user side is processed by the optical signal polarization multiplexing coherent modulation module, four baseband electrical signals are generated, which respectively correspond to the in-phase and quadrature (I/Q) components of the two polarization components of the first polarization multiplexing optical signal. The four baseband electric signals are sent to a polarization multiplexing I/Q modulator to be simultaneously modulated on the first light in a coherent modeAnd generating the first polarization multiplexing optical signal in real time on two polarization states of the carrier signal. Specifically, the first polarization-multiplexed optical signal adopts a Quadrature Amplitude Modulation (QAM) format, and the modulation order may be 4QAM, 16QAM, 32QAM, or the like. In order to compensate modulation loss, insertion loss and energy loss existing in subsequent optical fiber transmission, the first polarization multiplexing optical signal is amplified by the optical fiber amplifier 1 and then emitted into a standard single-mode optical fiber for transmission, and the length of the optical fiber is changed from 1 m to 103 km.

For the receiving chain, the first semiconductor laser generates a wavelength of

The continuous light wave is used as the second optical local oscillation signal, and the second optical local oscillation signal and the second polarization multiplexing optical signal realize coherent demodulation in the polarization multiplexing coherent receiver, so that four paths of baseband electric signals are recovered in real time, and then are amplified by an electric amplifier, subjected to analog-to-digital conversion and subjected to digital signal processing, and are restored into a data stream of a user side.

As shown in fig. 4, in one embodiment, the wireless transceiver module includes: the antenna comprises a first transmitting antenna, a second transmitting antenna, a first receiving antenna and a second receiving antenna. The input end of the first transmitting antenna is connected with the output end of the photodiode 1, and is used for radiating the terahertz signal in the X polarization direction to a free space (that is, for radiating the first path of terahertz signal output by the terahertz wireless optical fiber extension device to the free space); the input end of the second transmitting antenna is connected with the output end of the photodiode 2, and is used for radiating the terahertz signal in the Y polarization direction to a free space (that is, for radiating a second path of terahertz signal output by the terahertz wireless optical fiber extension device to the free space); the first receiving antenna is used for receiving the wireless terahertz signal in the X polarization direction (namely the first path) transmitted by the first transmitting antenna; the second receiving antenna is used for receiving the wireless terahertz signal in the Y polarization direction (namely the second path) transmitted by the first transmitting antenna.

And sending the terahertz signal in the X polarization direction into the first transmitting antenna, and sending the terahertz signal in the Y polarization direction into the second transmitting antenna so as to realize infinite transmission in a free space. And the wireless terahertz signals in the X and Y polarization directions are received by the first receiving antenna and the second receiving antenna respectively and are transmitted to the terahertz wireless optical fiber expansion device.

In particular, in one embodiment, the

fiber amplifiers

1 and 2 are polarization maintaining Erbium Doped Fiber Amplifiers (EDFAs).

In particular, in one embodiment, the polarizations of the first and second transmitting antennas and the first and second receiving antennas are both horizontal polarizations or vertical polarizations.

In particular, in one embodiment, the modulator 1 and the modulator 2 are both Phase Modulators (PM) or mach-zehnder modulators (MZM).

When only one group of time coherent light transceiving module, the terahertz wireless optical fiber expansion device and the wireless transceiving module is provided, the first receiving antenna and the second receiving antenna respectively receive the first path of wireless terahertz signal and the second path of wireless terahertz signal transmitted in the same group through the intelligent reflecting surface. The wireless signal can be transmitted back by the intelligent reflecting surface, and the complete process of self-transmitting and self-receiving of the signal is realized under the condition of only using a single set of system.

Fig. 6 is a block diagram illustrating a real-time transmission system based on a terahertz wireless optical fiber extension apparatus according to another embodiment of the present application.

The embodiment provides a real-time transmission system based on a terahertz wireless optical fiber expansion device, which comprises: the system comprises a real-time coherent light transceiver module 1, a terahertz wireless optical fiber expansion device 2, a wireless transceiver module 3 and an intelligent reflecting surface 7 (RIS).

Specifically, in one embodiment, the real-time coherent optical transceiver module 1 includes: a coherent optical modem 11 and an optical fiber amplifier 12 (EDFA). The data interface of the coherent optical modem 11 is connected with a user side, and the optical signal input end is connected with the optical signal output end of the terahertz wireless optical fiber expansion device 2 through an optical fiber; the input end of the optical fiber amplifier 12 is connected to the optical signal output end of the coherent optical modem 11.

In a specific embodiment, the terahertz wireless optical fiber extension device 2 includes: an optical heterodyne terahertz signal generating module 2a, an intermediate frequency signal modulating module 2b, and a semiconductor laser 2a4 (ECL).

The semiconductor laser 2a4 is used for generating a first optical local oscillation signal and a second optical carrier signal;

specifically, in one embodiment, the optical heterodyne terahertz signal generating module 2a includes: a light attenuator 2a1 (VOA), a first polarization maintaining beam splitter 2a2, a second polarization maintaining beam splitter 2a3, a polarization controller 2a5 (PC), a first optical coupler 2a6, a second optical coupler 2a7, a first photodiode 2a8 (UTC-PD), and a second photodiode 2a 9. The input end of the optical attenuator 2a1 is connected with the output end of the optical fiber amplifier 12 through an optical fiber; the input end of the first polarization maintaining beam splitter 2a2 is connected with the output end of the optical attenuator 2a 1; the input end of the polarization controller 2a5 is connected with the output end of the semiconductor laser 2a 4; the input end of the second polarization maintaining beam splitter 2a3 is connected with the output end of the polarization controller 2a 5; the first input end of the first optical coupler 2a6 is connected to the first output end of the first polarization maintaining beam splitter 2a2, and the second input end is connected to the first output end of the second polarization maintaining beam splitter 2a 3; the first input end of the second optical coupler 2a7 is connected to the second output end of the second polarization maintaining beam splitter 2a3, and the second input end is connected to the second output end of the first polarization maintaining beam splitter 2a 2; an input terminal of the first photodiode 2a8 is connected to an output terminal of the first photo-coupler 2a 6; an input terminal of the second photodiode 2a9 is connected to an output terminal of the second photo-coupler 2a 7;

specifically, in one embodiment, the intermediate frequency signal modulation module 2b includes: a radio frequency local oscillator 2b1 (LO), a frequency multiplier 2b2, a first mixer 2b3, a second mixer 2b4, a first low noise amplifier 2b5 (LNA), a second low noise amplifier 2b6, a polarization maintaining beam splitter 2b7, a first modulator 2b8 (PM), a second modulator 2b9, a polarization maintaining optical coupler 2b10 (PM-OC), an optical fiber amplifier 2b11 (EDFA), and a tunable optical filter 2b12 (TOF). The radio frequency local oscillation source 2b1 is configured to generate a first radio frequency local oscillation signal; the input end of the frequency multiplier 2b2 is connected with the output end of the radio frequency local oscillation source 2b 1; the first input end of the first mixer 2b3 is connected with the output end of the first receiving antenna 33, and the second input end is connected with the output end of the frequency multiplier 2b 2; the first input end of the second mixer 2b4 is connected to the output end of the second receiving antenna 34, and the second input end is connected to the output end of the frequency multiplier 2b 2; the input terminal of the first low noise amplifier 2b5 is connected to the output terminal of the first mixer 2b 3; the input terminal of the second low noise amplifier 2b6 is connected to the output terminal of the second mixer 2b 4; the input end of the polarization maintaining beam splitter 2b7 is connected with the output end of the semiconductor laser 2a 4; a drive signal input terminal of the first modulator 2b8 is connected to an output terminal of the first low noise amplifier 2b5, and an optical signal input terminal is connected to a first output terminal of the polarization maintaining beam splitter 2b 7; a driving signal input end of the second modulator 2b9 is connected with an output end of the second low noise amplifier 2b6, and an optical signal input end is connected with a second output end of the polarization maintaining beam splitter 2b 7; the first input end of the polarization-maintaining optical coupler 2b10 is connected with the output end of the first modulator 2b8, and the second input end is connected with the output end of the second modulator 2b 9; the input end of the optical fiber amplifier 2b11 is connected with the output end of the polarization-maintaining optical coupler 2b 10; the input end of the tunable optical filter 2b12 is connected with the output end of the optical fiber amplifier 2b 11.

In a specific embodiment, the wireless transceiver module 3 includes: a first transmitting antenna 31, a second transmitting antenna 32, a first receiving antenna 33 and a second receiving antenna 34. The input end of the first transmitting antenna 31 is connected with the output end of the first photodiode 2a 8; the input end of the second transmitting antenna 32 is connected with the output end of the second photodiode 2a 9; the first receiving antenna 33 is used for receiving a wireless terahertz signal in the X polarization direction; the second receiving antenna 34 is used for receiving the wireless terahertz signal in the Y polarization direction.

In a specific embodiment, the intelligent reflecting surface is a plane composed of a large number of low-cost passive reflecting elements, and since each element can independently change the phase (or/and) amplitude or even frequency of an incident signal, a user can better receive a signal transmitted by a base station. The intelligent reflecting surface can effectively construct a system transmission link under the following conditions: when the receiving antenna is positioned in a dead angle, the intelligent reflecting surface is properly used, and a reflecting path can be manufactured, so that the receiving antenna can still receive signals; when long-distance signals and energy are transmitted, the intelligent reflecting surface can enhance the transmission effect.

In a specific embodiment, a specific transmission process of the real-time transmission system based on the terahertz wireless optical fiber extension device provided by the application is as follows:

in the real-time optical coherent transceiver module 1, the coherent optical modem 11 receives a data stream from a user side and generates a first optical carrier signal to generate a first polarization multiplexing optical signal in real time, and the first polarization multiplexing optical signal is amplified by the optical fiber amplifier 12 and then transmitted to the terahertz wireless optical fiber expansion device 2 through an optical fiber.

The first optical carrier is a continuous wave optical wave with the wavelength of 1550nm and the frequency of 193.55 THz; the rate of the data stream of the user side is 32 Gbaud; the first polarization multiplexing optical signal is a 32QAM signal in a polarization state; the length of the optical fiber is 60 km.

After the first polarization multiplexing optical signal is transmitted through an optical fiber, real-time power control is performed in the optical heterodyne terahertz signal generating module 2a of the terahertz wireless optical fiber extension apparatus 2 through the optical attenuator 2a1, and the first polarization beam splitter 2a2 splits the first polarization multiplexing optical signal into orthogonal X and Y polarization state signals, which are respectively coupled with the first optical local oscillation signal. To realize the simultaneous beat frequency in the two subsequent polarization directions, the polarization state of the first optical local polarization signal is separated and then coupled to the two orthogonal polarization states of the first polarization-multiplexed optical signal by the first optical coupler 2a6 and the second optical coupler 2a7, respectively. Then, beat frequency is obtained through the first photodiode 2a8 and the second photodiode 2a9, and converted into X and Y terahertz signals which are sent to the wireless transceiver module 3 for transmission.

The first optical local oscillation signal is a continuous wave light wave with the wavelength of 1552.7nm and the frequency of 193.21THz, the frequency difference between the first optical local oscillation signal and the first polarization multiplexing optical signal is 340GHz, and the polarization direction of the first optical local oscillation signal is controlled by the polarization controller; the frequency of the generated two paths of terahertz signals is 340 GHz.

In the wireless transceiver module 3, the X-path terahertz signal is sent to the first transmitting antenna 31, and the Y-path terahertz signal is sent to the second transmitting antenna 32, so as to realize infinite transmission in free space.

The X and Y path wireless terahertz signals are reflected back to the wireless transceiver module 3 through the intelligent reflecting surface 7, are received by the first receiving antenna 33 and the second receiving antenna 34 respectively, and are sent back to the terahertz wireless optical fiber expansion device 2.

In particular, in one embodiment, the polarizations of the first and second transmit antennas 31/32 and the first and second receive antennas 33/34 are horizontally polarized.

In the intermediate frequency signal modulation module 2b of the terahertz wireless optical fiber extension device 2, the X and Y terahertz signals from the wireless transceiver module are mixed with the terahertz local oscillator by the first mixer 2b3 and the second mixer 2b4, respectively, and are down-converted to an intermediate frequency. Meanwhile, after the power amplification is performed on the X and Y paths of intermediate frequency signals, the first modulator 2b8 and the second modulator 2b9 respectively modulate the two paths of intermediate frequency signals onto two paths of polarization states of the second optical carrier, so as to form optical carrier intermediate frequency signals in the X and Y paths of polarization states. The two paths of optical carrier intermediate frequency signals are combined into one path of optical carrier intermediate frequency signal, i.e., the second polarization multiplexing optical signal, by the polarization maintaining optical coupler 2b 10. The second polarization multiplexed optical signal is amplified and filtered by the optical fiber amplifier 2b11 and the tunable optical filter 2b12, and then a higher signal sideband, an optical carrier and a signal spontaneous noise are suppressed, and finally the second polarization multiplexed optical signal is sent to a standard single-mode optical fiber to be transmitted back to the real-time coherent optical transceiver module 1.

The second optical carrier is the same as the first optical local oscillation signal, and is a continuous wave optical wave with the wavelength of 1552.7nm and the frequency of 193.21 THz.

The radio frequency local oscillation source 2b1 provides a10 GHz radio frequency signal as the radio frequency local oscillation signal, and the frequency multiplier adopts a 10-frequency multiplier; the frequency of the generated two paths of optical carrier intermediate frequency signals is 40 GHz.

In the real-time coherent optical transceiver module 1, the coherent optical modem 11 generates the second optical local oscillation signal, and implements coherent demodulation and depolarization multiplexing of the second polarization multiplexed optical signal of the single sideband, and finally recovers a data stream of a user side.

The second optical local oscillation signal is the same as the first optical carrier signal, and is a continuous wave optical wave with the wavelength of 1550nm and the frequency of 193.55 THz.

In particular, in a particular embodiment, the first fiber amplifier 12 and the second fiber amplifier 2b11 are polarization maintaining Erbium Doped Fiber Amplifiers (EDFAs).

In particular, in a particular embodiment, the first modulator 2b8 and the second modulator 2b9 are Phase Modulators (PM).

Therefore, in a specific embodiment, the real-time transmission system based on the terahertz wireless optical fiber extension device finally achieves data self-sending and self-receiving transmission with the net rate of 200 Gbit/s.

In a specific embodiment, besides the single system is adopted to realize self-sending and self-receiving transmission of signals, the real-time transmission system based on the terahertz wireless optical fiber expansion device provided by the application can also realize full-duplex real-time transmission based on two completely same systems.

Fig. 7 is a block diagram of a detailed structure of an uplink and a downlink of a full-duplex real-time transmission system based on a terahertz wireless optical fiber extension apparatus according to still another embodiment of the present application.

In a specific embodiment, the application provides a full-duplex real-time transmission system based on a terahertz wireless optical fiber expansion device, which comprises two groups of real-time coherent light transceiving modules, a terahertz wireless optical fiber expansion device and a wireless transceiving module; the method comprises the following steps that a real-time coherent light transceiving module is distributed on two user sides, and a terahertz wireless optical fiber expansion device and a wireless transceiving module are distributed at the bridging position of two optical fibers and wireless;

specifically, the uplink includes: the terahertz wireless optical fiber expanding device comprises a real-time coherent light transceiving module 1, an optical heterodyne terahertz signal generating module 2a in the terahertz wireless optical fiber expanding device 2, a wireless transceiving module 3, a wireless transceiving module 4, an intermediate frequency signal modulating module 5a in the terahertz wireless optical fiber expanding device 5 and a real-time coherent light transceiving module 6;

the downlink includes: the terahertz wireless optical fiber expanding device comprises a real-time coherent light transceiving module 6, an optical heterodyne terahertz signal generating module 5b in the terahertz wireless optical fiber expanding device 5, a wireless transceiving module 4, a wireless transceiving module 3, an intermediate frequency signal modulating module 2b in the terahertz wireless optical fiber expanding device 2 and a real-time coherent light transceiving module 1.

The connection relationship of the downlink of the full-duplex real-time transmission system based on the terahertz wireless optical fiber extension device is basically the same as that of the real-time transmission system based on the terahertz wireless optical fiber extension device in the previous embodiment, and meanwhile, the connection relationship of the uplink of the full-duplex real-time transmission system based on the terahertz wireless optical fiber extension device is completely the same as that of the downlink and is symmetrically distributed.

In a specific embodiment, the transmission process of the full-duplex real-time transmission system based on the terahertz wireless optical fiber extension device is as follows:

for the uplink, in the real-time optical coherent transceiver module 1, the coherent optical modem 11 receives an uplink data stream from a user terminal and generates an uplink first optical carrier signal, so as to generate an uplink first polarization multiplexing optical signal in real time, and after being amplified by the optical fiber amplifier 12, the uplink first polarization multiplexing optical signal is transmitted to the terahertz wireless optical fiber expansion apparatus 2 by an optical fiber.

The uplink first optical carrier is a continuous wave optical wave with the wavelength of 1550nm and the frequency of 193.55 THz; the rate of the uplink data stream is 32 Gbaud; the uplink first polarization multiplexing optical signal is a 16QAM signal in a polarization state; the length of the optical fiber is 60 km.

After the uplink first polarization multiplexing optical signal is transmitted through an optical fiber, real-time power control is performed in the optical heterodyne terahertz signal generating module 2a of the terahertz wireless optical fiber extension apparatus 2 through the optical attenuator 2a1, and the optical heterodyne terahertz signal generating module is decomposed into orthogonal X and Y polarization state signals by the first polarization beam splitter 2a2 and is respectively coupled with the uplink first optical local oscillation signal. To realize the simultaneous beat frequency in the two subsequent polarization directions, the polarization state of the uplink first optical local polarization signal is separated and then coupled to the two orthogonal polarization states of the uplink first polarization multiplexed optical signal by the first optical coupler 2a6 and the second optical coupler 2a 7. Then, the signals are beaten by the photodiode 2a8 and the photodiode 2a9, converted into uplink terahertz signals on X and Y paths and sent to the wireless transceiving module for transmission 3.

The uplink first optical local oscillation signal is a continuous wave optical wave with the wavelength of 1552.7nm and the frequency of 193.21THz, the frequency difference between the uplink first optical local oscillation signal and the uplink first polarization multiplexing optical signal is 340GHz, and the polarization direction of the uplink first polarization multiplexing optical signal is controlled by the polarization controller; the frequency of the generated two paths of terahertz signals is 340 GHz.

In the wireless transceiver module 3, the uplink terahertz signal on the X path is sent to the first transmitting antenna 31, and the uplink terahertz signal on the Y path is sent to the second transmitting antenna 32, so as to realize infinite transmission in free space.

The terahertz signals of the uplink on the X and Y paths are wirelessly transmitted to the wireless transceiving module 4 through free space, are respectively received by the first receiving antenna 41 and the second receiving antenna 42, and are sent to the terahertz wireless optical fiber expansion device 5.

In the intermediate frequency signal modulation module 5a of the terahertz wireless optical fiber extension device 5, uplink terahertz signals on the X and Y channels from the wireless transceiver module are respectively mixed with an uplink terahertz local oscillator by the first mixer 5a3 and the second mixer 5a4, and are down-converted to an intermediate frequency. Meanwhile, after the power amplification is performed on the uplink intermediate frequency signals on the X and Y paths, the first modulator 5a8 and the second modulator 5a9 respectively modulate the uplink intermediate frequency signals on two paths of polarization states of the second optical carrier on the uplink, so as to form optical carrier intermediate frequency signals in the polarization states of the X and Y paths. The two uplink optical carrier if signals are combined into one optical carrier if signal by the polarization maintaining optical coupler 5a10, i.e. the uplink second polarization multiplexed optical signal. The uplink second polarization multiplexing optical signal is amplified and filtered by the optical fiber amplifier 5a11 and the tunable optical filter 5a12, and then a higher signal sideband, an optical carrier and a signal spontaneous noise are suppressed, and finally the uplink second polarization multiplexing optical signal is sent to a standard single-mode optical fiber to be transmitted back to the real-time coherent optical transceiver module 6.

The uplink second optical carrier is a continuous wave optical wave with a wavelength of 1552.7nm and a frequency of 193.21THz, and is the same as the uplink first optical local oscillation signal.

The radio frequency local oscillation source 5a1 provides a10 GHz radio frequency signal as an uplink radio frequency local oscillation signal, and the frequency multiplier adopts a 10-frequency multiplier; the frequency of the generated two paths of intermediate frequency signals is 40 GHz.

In the real-time coherent optical transceiver module 6, the coherent optical modem 61 generates the uplink second optical local oscillation signal, and implements coherent demodulation and depolarization multiplexing of the single-sideband uplink second polarization-multiplexed optical signal, and finally recovers the uplink data stream.

The uplink second optical local oscillator signal is the same as the uplink first optical carrier signal, and is a continuous wave optical wave with a wavelength of 1550nm and a frequency of 193.55 THz.

In particular, in the exemplary embodiment, the polarization of the first and second transmit antennas 31/32 and the first and second receive antennas 41/42 is horizontal.

In particular, in a particular embodiment, the first fiber amplifier 12 and the second fiber amplifier 5a11 are polarization maintaining Erbium Doped Fiber Amplifiers (EDFAs).

In particular, in one embodiment, the first modulator 5a8 and the second modulator 5a9 are Phase Modulators (PM).

For the downlink, in the real-time optical coherent transceiver module 6, the coherent optical modem 61 receives a downlink data stream from a user terminal and generates a downlink first optical carrier signal, so as to generate a downlink first polarization-division multiplexing optical signal in real time, and after being amplified by the optical fiber amplifier 62, the downlink first polarization-division multiplexing optical signal is transmitted to the terahertz wireless optical fiber extension apparatus 5 by an optical fiber.

Wherein, the coherent optical modem 61 adopts a commercial 200G coherent optical module;

the first optical carrier of the downlink is a continuous wave optical wave with the wavelength of 1550nm and the frequency of 193.55 THz; the rate of the downlink data stream is 32 Gbaud; the downlink first polarization multiplexing optical signal is a 16QAM signal in a polarization state; the length of the optical fiber is 60 km.

After the downlink first polarization multiplexing optical signal is transmitted through an optical fiber, real-time power control is performed in the optical heterodyne terahertz signal generating module 5b of the terahertz wireless optical fiber extension apparatus 5 through the optical attenuator 5b1, and the downlink first polarization multiplexing optical signal is decomposed into orthogonal X and Y polarization state signals by the first polarization beam splitter 5b2 and is respectively coupled with a downlink first optical local oscillation signal. To realize the simultaneous beat frequency in the two subsequent polarization directions, the polarization state of the downlink first polarization multiplexed optical signal is separated and coupled to the two orthogonal polarization states of the downlink first polarization multiplexed optical signal by the first optical coupler 5b6 and the second optical coupler 5b 7. Then, the signals are beaten by the photodiode 5b8 and the photodiode 5b9, converted into X and Y downlink terahertz signals and sent to the wireless transceiving module for transmission 4.

The downlink first optical local oscillation signal is a continuous wave optical wave with the wavelength of 1552.7nm and the frequency of 193.21THz, the frequency difference with the downlink first polarization multiplexing optical signal is 340GHz, and the polarization direction of the downlink first optical local oscillation signal is controlled by the polarization controller; the frequency of the generated two paths of terahertz signals is 340 GHz.

In the wireless transceiver module 4, the X downlink terahertz signal is sent to the first transmitting antenna 43, and the Y downlink terahertz signal is sent to the second transmitting antenna 44, so as to realize infinite transmission in free space.

The X-path downlink wireless terahertz signals and the Y-path downlink wireless terahertz signals are wirelessly transmitted to the wireless transceiving module 3 through free space, are respectively received by the first receiving antenna 33 and the second receiving antenna 34, and are sent to the terahertz wireless optical fiber expansion device 2.

In the intermediate frequency signal modulation module 2b of the terahertz wireless optical fiber extension device 2, the X and Y downlink terahertz signals from the wireless transceiver module are mixed with the downlink terahertz local oscillator by the first mixer 2b3 and the second mixer 2b4, respectively, and are down-converted to an intermediate frequency. Meanwhile, after the power amplification is performed on the X and Y downlink intermediate frequency signals, the first modulator 2b8 and the second modulator 2b9 respectively modulate the two downlink intermediate frequency signals to the two polarization states of the downlink second optical carrier, so as to form optical carrier intermediate frequency signals in the X and Y polarization states. The two downlink optical carrier intermediate frequency signals are combined into one downlink optical carrier intermediate frequency signal by the polarization maintaining optical coupler 2b10, that is, the downlink second polarization multiplexed optical signal. The downlink second polarization multiplexing optical signal is amplified and filtered by the optical fiber amplifier 2b11 and the tunable optical filter 2b12, and then a higher signal sideband, an optical carrier and spontaneous emission noise are suppressed, and finally the downlink second polarization multiplexing optical signal is sent to a standard single-mode optical fiber to be transmitted back to the real-time coherent optical transceiver module 1.

Wherein the downlink second optical carrier is a continuous wave optical wave with a wavelength of 1552.7nm and a frequency of 193.21THz, which is the same as the downlink first optical local oscillator signal.

The radio frequency local oscillation source 2b1 provides a10 GHz radio frequency signal as a downlink radio frequency local oscillation signal, and the frequency multiplier adopts a 10-frequency multiplier; the frequency of the generated two paths of intermediate frequency signals is 40 GHz.

In the real-time coherent optical transceiver module 1, the coherent optical modem 11 generates a downlink second optical local oscillation signal, and implements coherent demodulation and depolarization multiplexing of the downlink second polarization multiplexed optical signal, and finally recovers a downlink user-side data stream.

The downlink second optical local oscillator signal is the same as the downlink first optical carrier signal, and is a continuous wave optical wave with a wavelength of 1550nm and a frequency of 193.55 THz.

In particular, in a specific embodiment, the polarization of the first and second transmitting antennas 43/44 and the polarization of the first and second receiving antennas 33/34 are horizontal polarization.

In particular, in a particular embodiment, the first fiber amplifier 62 and the second fiber amplifier 2b11 are polarization maintaining Erbium Doped Fiber Amplifiers (EDFAs).

Therefore, in a specific embodiment, the full-duplex real-time transmission system based on the terahertz wireless optical fiber expansion device can finally realize simultaneous bidirectional real-time transmission of data with a net rate of 200Gbit/s between two transmitting ends, effectively enlarges the transmission capacity of the optical fiber transmission system, remarkably reduces the transmission cost, and enables the system to be more economic and efficient.

All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A terahertz wireless optical fiber expansion device is characterized by comprising:

2. The terahertz wireless optical fiber extension device according to claim 1, wherein the optical heterodyne terahertz signal generation module comprises:

the input end of the first polarization beam splitter is connected with the output end of the optical attenuator and is used for polarization beam splitting of the first polarization multiplexing optical signal into two paths of orthogonal polarization state signals;

the input end of the polarization controller is connected with the output end of the second semiconductor laser and is used for adjusting the polarization direction of the first light natural vibration signal;

the input end of the first photodiode is connected with the output end of the first optical coupler and used for generating a first path of terahertz signal in a beat frequency mode in an optical heterodyne mode;

3. The terahertz wireless optical fiber extension device according to claim 1, wherein the intermediate frequency signal modulation module comprises:

the input end of the second low-noise amplifier is connected with the output end of the second mixer and used for amplifying a second path of intermediate frequency signals;

and the input end of the tunable optical filter is connected with the output end of the second optical fiber amplifier and is used for filtering partial sidebands and optical carriers of the second polarization multiplexing optical signal.

4. A real-time transmission system based on the terahertz wireless optical fiber extension device as claimed in any one of claims 1 to 3, comprising: at least one group of real-time coherent light receiving and transmitting modules, the terahertz wireless optical fiber expansion device and the wireless receiving and transmitting modules are sequentially connected; the real-time coherent light transceiver module is arranged at a user side, and the terahertz wireless optical fiber expansion device and the wireless transceiver module are arranged at a bridge joint of optical fibers and wireless;

5. The real-time transmission system based on the terahertz wireless optical fiber extension device as claimed in claim 4, wherein the real-time coherent optical transceiver module comprises: a coherent optical modem and a first fiber amplifier;

6. The real-time transmission system based on the terahertz wireless optical fiber extension device as claimed in claim 5, wherein the coherent optical modem comprises:

7. The real-time transmission system based on the terahertz wireless optical fiber extension device according to claim 6, wherein the optical signal polarization multiplexing coherent modulation module comprises:

the input ends of the four first electrical amplifiers are respectively connected with the output ends of the four digital-to-analog converters and are used for amplifying the baseband electric signals;

the polarization multiplexing I/Q modulator is driven by four paths of amplified baseband electric signals, and an optical signal input end is connected with an output end of the first semiconductor laser and used for modulating the baseband electric signals onto the first optical carrier in a coherent modulation mode and realizing polarization multiplexing to obtain a first polarization multiplexing optical signal.

8. The real-time transmission system based on the terahertz wireless optical fiber extension device as claimed in claim 6, wherein the polarization multiplexing optical signal coherent demodulation module comprises:

an optical signal input end of the polarization multiplexing coherent receiver is connected with an output end of the first semiconductor laser, and is used for realizing coherent demodulation and depolarization multiplexing of a second polarization multiplexing optical signal and recovering four paths of baseband electric signals of the same direction and orthogonal components corresponding to two polarization components of the second polarization multiplexing optical signal;

9. The real-time transmission system based on the terahertz wireless optical fiber extension device as claimed in claim 4, wherein the wireless transceiver module comprises:

the first transmitting antenna is used for radiating the first path of terahertz signals output by the terahertz wireless optical fiber expansion device to a free space;

10. The real-time transmission system based on the terahertz wireless optical fiber extension device as claimed in any one of claims 4 to 9, wherein when there is only one set of the real-time coherent light transceiver module, the terahertz wireless optical fiber extension device and the wireless transceiver module, two terahertz signals emitted by the wireless transceiver module are reflected back to the wireless transceiver module through an intelligent reflecting surface.