CN110267127B

CN110267127B - Method, apparatus and computer readable medium for low cost passive optical network

Info

Publication number: CN110267127B
Application number: CN201810200567.1A
Authority: CN
Inventors: 叶晨晖; 张东旭; 胡小锋; 张凯宾
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2018-03-12
Filing date: 2018-03-12
Publication date: 2021-09-24
Anticipated expiration: 2038-03-12
Also published as: CN110267127A

Abstract

Embodiments of the present disclosure provide a method at an optical line terminal. The method comprises the following steps: and determining an equalization parameter used by the optical line terminal for performing signal equalization on the received signal based on the reference sequence and a receiving sequence received from the optical network unit, wherein the receiving sequence is generated after the optical network unit transmits the reference sequence transmitted by using the transmitting parameter through the optical fiber. The method further comprises the following steps: the level of the transceiving performance after the signal equalization is determined based on the equalization parameter and the transmission parameter. The method further comprises the following steps: in response to the transceiver performance level being below the threshold level, a message is sent to the optical network unit instructing the optical network unit to adjust the transmission parameters. Embodiments of the present disclosure also provide a corresponding optical line terminal, a method implemented at an optical network unit and a corresponding optical network unit, and a computer readable medium. Embodiments of the present disclosure improve signal transmission quality and support high-speed passive optical networks using cost-effective and low-bandwidth devices.

Description

Method, apparatus and computer readable medium for low cost passive optical network

Technical Field

Embodiments of the present disclosure relate generally to the field of optical communications, and more particularly, to a method, apparatus, and computer-readable medium in a passive optical network.

Background

In a Passive Optical Network (PON), it would be advantageous in cost savings for an Optical Network Unit (ONU) to use a low-cost Direct Modulation Laser (DML). However, the use of DML lasers in optical network units will inherently produce chirp (chirp) effects compared to the more costly electro-absorption modulated (EAM) lasers and Externally Modulated Lasers (EML). The chirp effect is a change in the frequency of a signal over time.

Further, in the case of using multi-level pulse amplitude modulation (for example, PAM4/8 or the like), the magnitude of the chirp effect is not uniform for different symbol patterns of the input signal, that is, the degree of chirp effect depends on the input signal itself. This non-uniform chirp is confounded by the bandwidth limitations and non-linear effects of the devices and fibre channels, resulting in that a signal with multiple distortion sources will be received at the receiving side (e.g. the optical line termination OLT). This presents a serious challenge for the receiving side to correctly recover the signal transmitted by the transmitting side (e.g., optical network unit).

Disclosure of Invention

Embodiments of the present disclosure relate to a method at an optical line terminal, a method at an optical network unit, an optical line terminal, an optical network unit, and a computer readable medium.

In a first aspect of the disclosure, a method at an optical line terminal is provided. The method comprises the following steps: and determining an equalization parameter used by the optical line terminal for performing signal equalization on the received signal based on the reference sequence and a receiving sequence received from the optical network unit, wherein the receiving sequence is generated after the optical network unit transmits the reference sequence transmitted by using the transmitting parameter through the optical fiber. The method further comprises the following steps: the level of the transceiving performance after the signal equalization is determined based on the equalization parameter and the transmission parameter. The method further comprises the following steps: in response to the transceiver performance level being below the threshold level, a message is sent to the optical network unit instructing the optical network unit to adjust the transmission parameters.

In a second aspect of the disclosure, there is provided a method at an optical network unit, the method comprising: and transmitting the reference sequence to the optical line terminal through the optical fiber by using the transmission parameter. The method further comprises the following steps: a message is received from the optical line terminal instructing the optical network unit to adjust the transmission parameters. The method further comprises the following steps: the transmission parameters are adjusted based on the message.

In a third aspect of the disclosure, an optical line terminal is provided. The optical line terminal comprises at least one processor and at least one memory including computer program instructions. The at least one memory and the computer program instructions are configured, with the at least one processor, to cause the optical line terminal to perform a method according to the first aspect.

In a fourth aspect of the present disclosure, an optical network unit is provided. The optical network unit includes at least one processor and at least one memory including computer program instructions. The at least one memory and the computer program instructions are configured to, with the at least one processor, cause the optical network unit to perform the method according to the second aspect.

In a fifth aspect of the disclosure, a computer-readable medium is provided. The computer readable medium comprises machine executable instructions which, when executed, cause a machine to perform a method according to the first aspect.

In a sixth aspect of the disclosure, a computer-readable medium is provided. The computer readable medium comprises machine executable instructions which, when executed, cause a machine to perform a method according to the second aspect.

Drawings

The above and other objects, features and advantages of the embodiments of the present disclosure will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

fig. 1 illustrates a schematic diagram of a communication system in which embodiments of the present disclosure may be implemented.

Figure 2 shows a schematic diagram of a global performance optimization procedure between an optical line terminal and an optical network unit according to an embodiment of the present disclosure.

Figure 3 shows a schematic diagram of another global performance optimization procedure between an optical line terminal and an optical network unit according to an embodiment of the present disclosure.

FIG. 4 shows a schematic diagram of global parameter optimization according to an embodiment of the present disclosure.

Figure 5 shows a flow diagram of a method implemented at an optical line terminal according to an embodiment of the present disclosure.

Figure 6 illustrates a flow diagram of a method implemented at an optical network unit according to an embodiment of the present disclosure.

Fig. 7A, 7B, and 7C show schematic diagrams of exemplary experimental results obtained using embodiments according to the present disclosure.

Fig. 8 illustrates a simplified block diagram of a device suitable for implementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals are used to designate the same or similar components.

Detailed Description

The principles and spirit of the present disclosure will be described with reference to a number of exemplary embodiments shown in the drawings. It is understood that these specific embodiments are described merely to enable those skilled in the art to better understand and implement the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

As used herein, the terms "comprises," comprising, "and the like are to be construed as open-ended inclusions, i.e.," including, but not limited to. The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first," "second," and the like may refer to different or the same object. Other explicit and implicit definitions are also possible below. As used herein, the term "determining" encompasses a wide variety of actions. For example, "determining" can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Further, "determining" can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Further, "determining" may include resolving, selecting, choosing, establishing, and the like.

The term "passive optical network" or "PON" as used herein means that the Optical Distribution Network (ODN) it comprises consists of passive devices such as optical splitters and optical fibers, without the need for any active devices. The term "optical communication device" as used herein refers to any suitable device or entity in an optical communication network that is capable of optical communication with an Optical Network Unit (ONU). For ease of discussion, in some embodiments, an Optical Line Terminal (OLT) is used as an example of an optical communication device.

The term "optical line terminal" or "OLT" as used herein refers to a device in a PON that serves end users as a service providing node. The OLT may, for example, provide an electrical-to-optical conversion function to send data out through an optical fiber in the ODN. The term "optical network unit" or "ONU" as used herein refers to a client node connected to an OLT by an optical fiber to receive user data from the OLT.

The term "circuitry" as used herein refers to one or more of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry); and (b) a combination of hardware circuitry and software, such as (if applicable): (i) a combination of analog and/or digital hardware circuitry and software/firmware, and (ii) any portion of a hardware processor and software (including a digital signal processor, software, and memory that work together to cause an apparatus, such as an OLT or other computing device, to perform various functions); and (c) hardware circuitry and/or a processor, such as a microprocessor or a portion of a microprocessor, that requires software (e.g., firmware) for operation, but may be software-free when software is not required for operation.

The definition of circuit applies to all usage scenarios of this term in this application, including any claims. As another example, the term "circuitry" as used herein also covers an implementation of merely a hardware circuit or processor (or multiple processors), or a portion of a hardware circuit or processor, or software or firmware accompanying it. For example, the term "circuitry" would also cover a baseband integrated circuit or processor integrated circuit or a similar integrated circuit in an OLT or other computing device, as applicable to the particular claim element.

Fig. 1 illustrates a schematic diagram of a communication system 100 in which embodiments of the present disclosure may be implemented. As shown in fig. 1, the communication system 100 may be part of a passive optical network that includes an optical line terminal 110 and an optical network unit 120. Communication may be performed between the optical line terminal 110 and the optical network unit 120. For example, the optical line terminal 110 may send signals to the optical network units 120 over the downlink 130, while the optical network units 120 may send signals to the optical line terminal 110 over the uplink 140.

In case the optical network unit 120 sends a signal to the optical line terminal 110 over the uplink 140, the optical network unit 120 will send the signal using the sending parameters. The transmission parameter may be a set consisting of a plurality of transmission parameters. For example, the transmission parameters of the optical network unit 120 may include the driving amplitude of the used laser, the bias current, the modulation depth, and the transmission power, etc. The signals transmitted by the optical network unit 120 are received by the optical line terminal 110 after being transmitted through the optical fiber link.

In this transmission, the optical line terminal 110 will receive a distorted signal due to the non-ideal bandwidth limitation and non-linear effects of the devices and the optical fiber. In order to recover the original signal transmitted by the optical network unit 120 from the distorted signal, as shown in fig. 1, the optical line terminal 110 includes a signal equalizing module 115. Generally, the signal equalization module 115 performs signal equalization on the distorted signal by using the equalization parameter, so as to recover the signal transmitted by the optical network unit 120. The equalization parameter may be a set comprising a plurality of equalization parameters.

It should be understood that the signal equalization module 115 may be implemented by hardware, software, or a combination of both hardware and software. Further, it will be understood that although only one optical network unit 120 is shown in fig. 1, in the communication system 100, the optical line terminal 110 may correspond to a plurality of optical network units including the optical network unit 120. The plurality of optical network units may respectively transmit signals, such as optical bursts (bursts), to the optical line terminal 110 in time slots allocated thereto. It will be noted that the optical line terminal 110 may use different equalization parameters for different optical network units, since different optical network units have different devices and optical fiber links.

As mentioned above, in some passive optical networks, especially those using low cost DML lasers, there will be a chirp effect. A chirp is a signal whose frequency increases (up-chirp) or decreases (down-chirp) with time. After phase-to-amplitude modulation (PM-AM) conversion in fiber transmission, the chirp effect will eventually limit data transmission in passive optical networks. This is the first level of understanding of chirp, which is sufficient for data formats that use only two levels (e.g., 0 and 1).

However, with further investigation of chirp, it will be found that when the data format evolves from binary to multilevel data formats (e.g., PMA4/8 or duobinary, duobinary PAM4, DMT/OFDM, etc.), the magnitude of chirp effects will be non-uniform for different symbol patterns of the input signal, where non-uniform means that the chirp effect (or degree) depends on the input signal itself. Furthermore, the chirp effect cannot be handled separately during signal transmission. In contrast, in a practical non-ideal fibre channel, linear impairments of the signal (e.g. intersymbol interference, chirp) and non-linear distortions (e.g. amplifier saturation) interact with each other and add together.

For example, a signal with a symbol pattern (combination of several symbols) of "010" is input to the DML laser that will produce a "wavelength/frequency" shift by an amount that is different from the amount of shift produced by a signal with a signal sequence of "030". The disparity in chirp will result in a non-uniform dispersion of the signal sequence, which makes conventional statistics-based post-equalization (e.g., LMS algorithms) useless in the presence of dynamic flowing symbol combinations. Thus, the chirp inconsistency, imperfect channel conditions (e.g., non-linearity and bandwidth limitations) of multi-level input signals present problems of symbol overlap and distortion, which are problematic for existing signal recovery schemes.

Some solutions have been proposed to mitigate chirp or dispersion in a low cost manner, but they all suffer from their own drawbacks. In one known approach, a DML laser is replaced with an electro-absorption modulated laser (EAM) or External Modulation (EML) without chirp effects, but they are costly. In another known approach, the use of Dispersion Shifted Fibers (DSFs) may be helpful, but different lengths of DSFs need to be used for different distances of the optical network units and are costly. In yet another known scheme, zero dispersion wavelengths are used, but they may already be occupied. In other known schemes, the modulation depth of the laser (e.g., DML) is reduced, but this sacrifices modulation efficiency and power budget in the passive optical network. In still other known schemes, a non-linear equalization method (e.g., a Volterra filter) is used, but it will take a lot of Digital Signal Processor (DSP) resources when considering the high order harmonics.

In addition, the methods listed above are all for binary (0, 1) format, i.e. the inputs are consistent, and thus the chirp is also consistent. However, for multi-level signals such as PAM4 with amplitude levels of 0, 1, 2, 3, the chirp effect will be non-uniform as described above. Furthermore, considering inter-symbol interference (ISI) due to bandwidth limitations and non-linear effects, more amplitude levels will be combined. For example, for a duobinary PAM4 signal, 7 amplitude levels need to be determined at the receiving side, where one amplitude level may be combined from the other amplitude levels due to various distortions. Thus, the diversity of chirp/dispersion presents a more complex problem than in conventional passive optical networks with only 0 and 1.

In view of the above analysis and study by the inventors, embodiments of the present disclosure provide a method at an optical line terminal, a method at an optical network unit, an optical line terminal, an optical network unit, and a computer-readable medium to solve the above technical problems and other problems. By the embodiment of the disclosure, adaptive signal equalization can be performed on the receiving side in a manner that an optical line terminal and an optical network unit are coordinated in a passive optical network, thereby realizing globally optimized transmitting and receiving performance levels for both transmitting and receiving parties. In some embodiments, the adaptive signal equalization may be based on an Artificial Neural Network (ANN). Example embodiments of the present disclosure will be described in detail below with reference to fig. 2 to 4.

Figure 2 shows a schematic diagram of a global performance optimization process 200 between an optical line terminal 110 and an optical network unit 120 according to an embodiment of the present disclosure. In some embodiments, the global performance optimization process 200 may obtain the optimized parameter settings of the transmitter and the receiver through the learning of the artificial neural network, so that the receiver can recover the signal sent by the sender, especially in the presence of the inconsistent chirp phenomenon.

As shown in fig. 2, the optical network unit 120 sends 205 the reference sequence to the optical line terminal 110 via the optical fiber using the sending parameters. The reference sequence is known in advance by both the optical line terminal 110 and the optical network unit 120, so that the optical line terminal 110 as the receiving side can obtain the equalization parameter for the signal equalization by the signal equalization module 115 based on the known reference sequence and the received distortion sequence. In practice, since the optical line terminal 110 may correspond to a plurality of optical network units and respectively uses different equalization parameters, the optical line terminal 110 may also first identify a specific optical network unit 120, so that the specific value of the equalization parameter used for the optical network unit 120 before can be directly used as the initial equalization parameter value for optimization.

In some embodiments, the transmission parameters used by the optical network unit 120 to transmit the reference sequence may include the driving amplitude, bias current, modulation depth, and transmit power of a laser used by the optical network unit 120, and so on. As discussed above, since the degree of the chirp phenomenon is not consistent for different input signals, and the influence of various nonlinear effects on different input signals is also nonlinear, in the global performance optimization process 200 between the optical line terminal 110 and the optical network unit 120, in addition to the equalization parameters for signal equalization by the optical line terminal 110, the transmission parameters of the optical network unit 120 need to be adjusted, so as to obtain the desired transceiving performance level.

With continued reference to figure 2, the optical line terminal 110 determines 210 an equalization parameter used by the optical line terminal 110 to signal equalize the received signal based on the reference sequence and the received sequence received from the optical network unit 120. Here, the receiving sequence is generated after the reference sequence transmitted by the optical network unit 120 using the transmission parameter is transmitted through the optical fiber. That is, the received sequence is the above-mentioned distorted sequence.

It will be appreciated that the signal equalization module 115 of the optical line terminal 110 may use a variety of optimization algorithms or optimization models to determine the equalization parameters. These optimization algorithms or optimization models include, but are not limited to: artificial Neural Networks (ANN), least mean square algorithms, maximum likelihood estimation, exhaustive methods, genetic algorithms, ant colony algorithms, tabu search algorithms, simulated annealing algorithms, greedy-based hill climbing algorithms, and the like. An artificial neural network-based algorithm will be described below as an example, but embodiments of the present disclosure are not limited thereto.

As used herein, the term "artificial neural network" refers to a model that is capable of learning the association between the corresponding input and output from a reference sequence as a training sequence, such that after training is completed, a given input signal is signal equalized based on a trained set of parameters to generate a recovered signal. In this document, "artificial neural network" may also sometimes be referred to as a "learning network," "learning model," "network," or "model," these terms being used interchangeably from top to bottom.

In embodiments using an artificial neural network, the signal equalization module 115 of the optical line terminal 110 may use a multi-layer artificial neural network, each layer may have a plurality of neurons, and each neuron may have a corresponding weight and offset. To determine the equalization parameters used to equalize the received signal, the optical line terminal 110 may determine weights, offsets, or both, or other parameters of the neurons of the artificial neural network. For example, the optical line terminal 110 may use a back propagation algorithm to optimize the parameters (e.g., weights and biases) of the neurons so that they converge to a particular value. The use of artificial neural network based equalization algorithms is less complex than conventional algorithms (e.g., least mean square algorithms, etc.). In addition, compared with a general linear equalization algorithm, the equalization algorithm based on the artificial neural network can realize a significantly improved channel compensation effect.

In some embodiments, since the properties of the optical fiber may vary, for example, may vary with temperature, in determining the equalization parameters, the optical line terminal 110 may also make fine adjustments to the equalization parameters to accommodate fluctuations in the transmission parameters of the optical fiber with temperature (or other factors).

With continued reference to figure 2, the optical line terminal 110 determines 215 a level of transceiving performance after signal equalization based on the equalization parameter and the transmission parameter. In some embodiments, to comprehensively exhibit the performance of both the sender and the receiver, the optical line terminal 110 may first perform signal equalization on the received sequence using the equalization parameter to obtain an equalized sequence, and determine a quality parameter, such as a bit error rate, of the equalized sequence. Since the transmission parameter may represent the performance level of the transmitting side and the quality parameter of the equalization sequence may represent the performance level of the receiving side, the optical line terminal 110 may derive the transceiving performance level based on the transmission parameter of the optical network unit 120 and the quality parameter of the resulting equalization sequence. In this way, the level of transceiving performance can be quantified.

Specifically, in order to derive the quantized transmission/reception performance level, the optical line terminal 110 may set a weight ratio of the transmission parameter to the quality parameter in the transmission/reception performance level. For example, the weight ratio may be represented by a percentage. As an example, in case the performance of the sender is more important, a higher weight ratio, e.g. 80%, may be set for the sending parameters. Conversely, if the performance level of the receiver is important, a higher weighting ratio, e.g., 80%, may be set for the quality parameter. After setting the weight ratio of the transmission parameter to the quality parameter, the optical line terminal 110 may calculate a level of transmission/reception performance, such as a quantized value, based on the value of the transmission parameter, the value of the quality parameter, and the weight ratio. In this way, the transceiving performance level can be determined to be a specific value, so that the transceiving performance level can be intuitively and digitally judged.

With continued reference to figure 2, the optical line terminal 110 determines 220 whether the level of transceiving performance is below a threshold level. It will be appreciated that the threshold level may be preset according to specific technical environments and technical requirements, and represents a predetermined minimum level of transceiving performance that is expected to be achieved, and if the determined level of transceiving performance of the optical line terminal 110 is lower than the threshold level, it indicates that the transmission parameters used by the optical network unit 120 for transmission and the equalization parameters used by the optical line terminal 110 for signal equalization need to be further adjusted and optimized.

As shown in figure 2, in response to the level of transceiving performance being below the threshold level, the optical line terminal 110 sends 225 a message to the optical network unit 120 instructing the optical network unit 120 to adjust the transmission parameters. Accordingly, the optical network unit 120 receives the message from the optical line terminal 110, so that the optical network unit 120 can know that the transmission parameters need to be adjusted and how to adjust. In some embodiments, the message may indicate a direction and magnitude of adjustment of the transmission parameters, or may also indicate an adjustment of the transmission parameters to a particular value. In this way, the optical network unit 120 may be prevented from blindly adjusting its transmission parameters (such blind adjustment may cause a reduction in the level of the transceiving performance), so as to determine the optimal transceiving performance level more efficiently. It will be understood that other manners of indication may also be used, and that embodiments of the present disclosure are not limited in this respect. Further, the indication message may be transmitted via the downlink 130 depicted in fig. 1.

With continued reference to figure 2, the optical network unit 120 adjusts 230 the transmission parameters based on the message and re-sends 235 the reference sequence to the optical line terminal 110 via the optical fiber using the adjusted transmission parameters. Accordingly, the optical line terminal 110 may repeatedly perform the above-described

actions

210, 215, 220 to perform the determination and optimization of the equalization parameters again, and determine the transceiving performance level again. In this way, the optical line terminal 110 and the optical network unit 120 may iteratively perform acts 205 to 235 until the level of transceiving performance is higher than or equal to the threshold level.

Figure 3 shows a schematic diagram of another communication process between an optical line terminal and an optical network unit according to an embodiment of the present disclosure. In the process described in fig. 3, act 205 through act 220 are the same as or similar to those in fig. 2, and are not described again here. Acts 204 through 250 will be described with emphasis herein.

As shown in figure 3, in response to the determined level of transceiving performance at 220 being greater than or equal to the threshold level, the optical line terminal 110 sends 240 a message to the optical network unit 120 instructing the optical network unit 120 to send the data signal using the transmission parameters used to send the reference sequence. For example, the transmission parameter may be a transmission parameter that has been adjusted and optimized several times.

In response to receiving the indication message, the optical network unit 120 sends 235 a data signal to the optical line terminal via the optical fiber using the sending parameter. In this case, the optical line terminal 110 performs signal equalization on the data signal received from the optical network unit 120 using the determined equalization parameter accordingly, thereby recovering the data signal transmitted by the optical network unit 120.

FIG. 4 shows a schematic diagram of global parameter optimization according to an embodiment of the present disclosure. As shown, the values of the reception quality parameters implemented at the optical line terminal 110 are depicted in a contour line fashion. In addition, the transmission parameters of the optical network unit 120 are represented in fig. 4 using the transmission parameter 1 and the transmission parameter 2 of the optical network unit 120 as an example. For example, the transmission parameter 1 may be a driving amplitude of a laser of the optical network unit 120, and the transmission parameter 2 may be a bias current of the laser of the optical network unit 120.

The contour lines 410 to 440 represent the values of different reception quality parameters, respectively, wherein the values of the reception quality parameters increase in sequence from the contour line 410 to the contour line 440. That is, the area surrounded by the contour 440 corresponds to the area of the best reception quality. Therefore, when the optical network unit 120 sets the transmission parameter 1 and the transmission parameter 2 in the area corresponding to the contour line 440, the optimal reception quality can be achieved at the optical line terminal 110. In such an intuitive manner as depicted in fig. 4, when determining the transceiving performance level, the optical line terminal 110 may reasonably determine the value of the transceiving performance level according to the contour diagram depicted in accordance with the weight ratio of the transmission parameter and the quality parameter.

Figure 5 shows a flow diagram of a method 500 implemented at an optical line terminal according to an embodiment of the present disclosure. It will be appreciated that the method 500 may be implemented, for example, at the optical line terminal 110 as shown in figures 1 to 3. For ease of description, the method 500 is described below in conjunction with fig. 1-3.

At 505, the optical line terminal 110 determines an equalization parameter used by the optical line terminal 110 to perform signal equalization on the received signal based on the reference sequence and the received sequence received from the optical network unit 120. The receiving sequence is generated after the reference sequence transmitted by the optical network unit 120 using the transmitting parameter is transmitted through the optical fiber. In some embodiments, the transmission parameters may include at least one of: the driving amplitude, bias current, modulation depth, and transmit power of the lasers used by the optical network unit 120.

In some embodiments, in determining the equalization parameters, the optical line terminal 110 may determine at least one of weights and biases for neurons of an artificial neural network used for signal equalization. In some embodiments, the optical line terminal 110 may further perform fine adjustment of the equalization parameters to accommodate fluctuations in the transmission parameters of the optical fiber with temperature.

At 510, the optical line terminal 110 determines a level of transceiving performance after performing signal equalization based on the equalization parameter and the transmission parameter. In some embodiments, in determining the transceiving performance level, the optical line terminal 110 may perform signal equalization on the reception sequence using the equalization parameter to obtain an equalized sequence, and derive the transceiving performance level based on the transmission parameter and a quality parameter of the equalized sequence.

In some embodiments, in order to derive the transceiving performance level, the optical line terminal 110 may set a weight ratio of the transmission parameter to the quality parameter in the transceiving performance level, and calculate the transceiving performance level based on the value of the transmission parameter, the value of the quality parameter, and the weight ratio.

At 515, the optical line terminal 110 determines whether the level of transceiving performance is below a threshold level. At 520, in response to determining at 515 that the level of transceiving performance is below the threshold level, the optical line terminal 110 sends a message to the optical network unit 120 instructing the optical network unit 120 to adjust the transmission parameters.

In some embodiments, the message may indicate a direction of adjustment and a magnitude of adjustment of the transmission parameter. In other embodiments, the message may also indicate that the transmission parameters are to be adjusted to a particular value.

In some embodiments, in response to determining at 515 that the level of transceiving performance is greater than or equal to the threshold level, the optical line terminal 110 may signal equalize the data signal received from the optical network unit 120 using the equalization parameters.

In some embodiments, an apparatus capable of performing the method 500 (e.g., the optical line terminal 110) may include respective means for performing the steps of the method 500. These components may be implemented in any suitable manner. For example, it may be implemented by a circuit or a software module.

In some embodiments, an apparatus comprises: means for determining an equalization parameter used by the apparatus to perform signal equalization on the received signal based on a reference sequence and a received sequence received from the optical network unit, the received sequence being generated after the optical network unit transmits the reference sequence transmitted using the transmission parameter through the optical fiber; means for determining a level of transceiving performance after performing signal equalization based on the equalization parameter and the transmission parameter; and means for sending a message to the optical network unit to instruct the optical network unit to adjust the transmission parameter in response to the transceiver performance level being below the threshold level.

In some embodiments, the means for determining the equalization parameter comprises: means for determining at least one of weights and biases for neurons of an artificial neural network used for signal equalization.

In some embodiments, the means for determining a level of transceiving performance comprises: means for performing signal equalization on the received sequence using the equalization parameters to obtain an equalized sequence; and means for deriving a level of transceiving performance based on the transmission parameter and a quality parameter of the equalization sequence.

In some embodiments, the means for deriving a level of transceiving performance comprises: means for setting a weight ratio of the transmission parameter to the quality parameter in the transceiving performance level; and means for calculating a level of transceiving performance based on the value of the transmission parameter, the value of the quality parameter, and the weight ratio.

In some embodiments, instructing the optical network unit to adjust the transmission parameter comprises at least one of: indicating the adjustment direction and the adjustment amplitude of the transmission parameters; and instructing to adjust the transmission parameter to a specific value.

In some embodiments, the apparatus further comprises: means for signal equalizing a data signal received from the optical network unit using an equalization parameter in response to the transceiver performance level being greater than or equal to a threshold level.

In some embodiments, the apparatus further comprises: means for fine tuning the equalization parameters to accommodate fluctuations in the transmission parameters of the fiber with temperature.

In some embodiments, the transmission parameters include at least one of: the driving amplitude, bias current, modulation depth, and transmit power of the lasers used by the optical network units.

Figure 6 illustrates a flow diagram of a method 600 implemented at an optical network unit according to an embodiment of the present disclosure. It will be understood that the method 600 may be implemented, for example, at an optical network unit 120 as shown in fig. 1-3. For ease of description, the method 500 is described below in conjunction with fig. 1-3.

At 605, the optical network unit 120 transmits the reference sequence to the optical line terminal 110 via the optical fiber using the transmission parameter. In some embodiments, the transmission parameters may include at least one of: the driving amplitude, bias current, modulation depth, and transmit power of the lasers used by the optical network unit 120.

At 610, the optical network unit 120 receives a message from the optical line terminal 110 instructing the optical network unit 120 to adjust the transmission parameters. In some embodiments, the message may indicate a direction of adjustment and a magnitude of adjustment of the transmission parameter. In other embodiments, the message may also indicate that the transmission parameters are to be adjusted to a particular value.

At 615, the optical network unit 120 adjusts the transmission parameters based on the message. In some embodiments, the optical network unit 120 may transmit the data signal to the optical line terminal 110 via the optical fiber using the adjusted transmission parameters.

In some embodiments, a device capable of performing method 600 (e.g., optical network unit 120) may include corresponding means for performing the various steps of method 600. These components may be implemented in any suitable manner. For example, it may be implemented by a circuit or a software module.

In some embodiments, an apparatus comprises: means for transmitting the reference sequence to the optical line terminal via the optical fiber using the transmission parameter; means for receiving a message from the optical line terminal, the message instructing the apparatus to adjust the transmission parameter; and means for adjusting the transmission parameters based on the message.

In some embodiments, the apparatus further comprises: means for transmitting the data signal to the optical line terminal via the optical fiber using the adjusted transmission parameter.

In some embodiments, instructing the apparatus to adjust the transmission parameter comprises at least one of: indicating the adjustment direction and the adjustment amplitude of the transmission parameters; and instructing to adjust the transmission parameter to a specific value.

In some embodiments, the transmission parameters include at least one of: the drive amplitude, bias current, modulation depth, and launch power of the laser used by the device.

Fig. 7A, 7B, and 7C show schematic diagrams of exemplary experimental results obtained using embodiments according to the present disclosure. In this experiment, a 2.5G DML laser (3dB bandwidth 2.7GHz, 10dB bandwidth 3.6GHz) was used to accommodate a 10G baud rate PAM4 service, i.e., 20 Gb/s. In addition, the experiment used a Standard Single Mode Fiber (SSMF) of 20 km and a 1:64 splitter.

Specifically, fig. 7A shows an eye pattern directly received without any equalization processing, fig. 7B shows an eye pattern recovered after linear equalization based on a conventional least mean square algorithm, and fig. 7C shows a recovered eye pattern according to an embodiment of the present disclosure. As shown, the unrecovered eye pattern is completely closed, whereas the eye pattern restored by conventional methods has improved over the eye pattern received directly. Preferably, the recovered eye pattern according to the embodiment of the present disclosure recovers very well, showing an eye pattern of 7 th order level (duo-binary PAM4), with a significant improvement over the conventional recovery approach. This shows that embodiments of the present disclosure can effectively compensate for signal impairments in the fiber link due to multiple distortion sources.

Furthermore, the results of this experiment also indicate that embodiments of the present disclosure may achieve the following advantages over conventional approaches. First, the bit error rate is greatly reduced, for example, from a level of 1E-2 to a level of 1E-3, thereby satisfying the requirement of Forward Error Correction (FEC). Secondly, the bias current of the DML laser can be reduced significantly, for example from 160mA to 80mA, thereby achieving a 50% reduction in power consumption.

In summary, embodiments of the present disclosure significantly improve signal transmission quality (e.g., reduce bit error rate of received signals) compared to conventional schemes, support high-speed passive optical networks using cost-effective and low-bandwidth devices, enable multi-level signal formats, save power consumption of lasers, are adaptive to various optical network terminals and their lasers (e.g., DML), and can be used in different passive optical networks.

Fig. 8 illustrates a simplified block diagram of a device 800 suitable for implementing embodiments of the present disclosure. In some embodiments, the apparatus 800 may be used to implement an optical line terminal, such as the optical line terminal 110 shown in figures 1-3. In some embodiments, the device 800 may be used to implement an optical network unit, such as the optical network unit 120 shown in fig. 1-3.

As shown in fig. 8, the device 800 includes a controller 810. The controller 810 controls the operation and functions of the device 800. For example, in certain embodiments, the controller 810 may perform various operations by way of instructions 830 stored in a memory 820 coupled thereto.

The memory 820 may be of any suitable type suitable to the local technical environment and may be implemented using any suitable data storage technology, including but not limited to semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems. It is to be appreciated that although only a single memory 820 is illustrated in FIG. 8, many physically distinct memory units may be present in the device 800.

The controller 810 may be of any suitable type suitable to the local technical environment and may include, but is not limited to, one or more of general purpose computers, special purpose computers, microcontrollers, digital signal controllers (DSPs), and controller-based multi-core controller architectures. The device 800 may also include a plurality of controllers 810. Controller 810 is coupled to transceiver 840, which transceiver 840 may enable the reception and transmission of information by way of one or more antennas 850 and/or other components.

When the device 800 is acting as the optical line terminal 110, the controller 810, the memory 820, the instructions 830, and the transceiver 840 may operate in cooperation to implement the method 500 described above with reference to figure 5. When device 800 is acting as optical network unit 120, controller 810, memory 820, instructions 830, and transceiver 840 may cooperate to implement method 600 described above with reference to fig. 6. All of the features described above with reference to fig. 2-6 apply to the apparatus 800 and are not described in detail here.

It should be noted that the embodiments of the present disclosure can be realized by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or specially designed hardware. Those skilled in the art will appreciate that the apparatus and methods described above may be implemented using computer executable instructions and/or embodied in processor control code, such code being provided, for example, in programmable memory or on a data carrier such as an optical or electronic signal carrier.

By way of example, embodiments of the disclosure may be described in the context of machine-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or divided between program modules as described. Machine-executable instructions for program modules may be executed within local or distributed devices. In a distributed facility, program modules may be located in both local and remote memory storage media.

Computer program code for implementing the methods of the present disclosure may be written in one or more programming languages. These computer program codes may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the computer or other programmable data processing apparatus, cause the functions/acts specified in the flowchart and/or block diagram block or blocks to be performed. The program code may execute entirely on the computer, partly on the computer, as a stand-alone software package, partly on the computer and partly on a remote computer or entirely on the remote computer or server.

In the context of the present disclosure, computer program code or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations described above. Examples of a carrier include a signal, computer readable medium, and the like. Examples of signals may include electrical, optical, radio, acoustic, or other forms of propagated signals, such as carrier waves, infrared signals, and the like.

The computer readable medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof. More detailed examples of a computer-readable storage medium include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical storage device, a magnetic storage device, or any suitable combination thereof.

Further, while the operations of the methods of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that these operations must be performed in this particular order, or that all of the illustrated operations must be performed, to achieve desirable results. Rather, the steps depicted in the flowcharts may change the order of execution. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions. It should also be noted that the features and functions of two or more devices according to the present disclosure may be embodied in one device. Conversely, the features and functions of one apparatus described above may be further divided into embodiments by a plurality of apparatuses.

While the present disclosure has been described with reference to several particular embodiments, it is to be understood that the disclosure is not limited to the particular embodiments disclosed. The disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method at an optical line terminal, comprising:

determining an equalization parameter used by the optical line terminal to perform signal equalization on a received signal based on a reference sequence and a receiving sequence received from an optical network unit, wherein the receiving sequence is generated after the reference sequence sent by the optical network unit by using a sending parameter is transmitted through an optical fiber;

determining a transceiving performance level after the signal equalization based on the equalization parameter and the transmission parameter, the transceiving performance level embodying performance of both the optical network unit and the optical line terminal; and

in response to the level of transceiving performance being below a threshold level, sending a message to the optical network unit to instruct the optical network unit to adjust the transmission parameter.

2. The method of claim 1, wherein determining the equalization parameter comprises:

at least one of a weight and a bias of a neuron of an artificial neural network for signal equalization is determined.

3. The method of claim 1, wherein determining the level of transceiving performance comprises:

performing signal equalization on the received sequence by using the equalization parameter to obtain an equalized sequence; and

deriving the transceiving performance level based on the transmission parameter and a quality parameter of the equalization sequence.

4. The method of claim 3, wherein deriving the level of transceiving performance comprises:

setting a weight ratio of the transmission parameter to the quality parameter in the transceiving performance level; and

calculating the transceiving performance level based on the value of the transmission parameter, the value of the quality parameter, and the weight ratio.

5. The method of claim 1, wherein instructing the optical network unit to adjust the transmission parameters comprises at least one of:

indicating the adjustment direction and the adjustment amplitude of the sending parameters; and

instructing to adjust the transmission parameter to a particular value.

6. The method of claim 1, further comprising:

performing signal equalization on the data signal received from the optical network unit using the equalization parameter in response to the transceiver performance level being greater than or equal to the threshold level.

7. The method of claim 6, further comprising:

and finely adjusting the equalization parameters to adapt to the fluctuation of the transmission parameters of the optical fiber along with the temperature.

8. The method of claim 1, wherein the transmission parameters comprise at least one of: the optical network unit uses the driving amplitude, bias current, modulation depth and transmitting power of the laser.

9. A method at an optical network unit, comprising:

transmitting the reference sequence to the optical line terminal via the optical fiber using the transmission parameter;

receiving a message from the optical line terminal, the message instructing the optical network unit to adjust the transmission parameter; and

adjusting the transmission parameters based on the message.

10. The method of claim 9, further comprising:

and sending a data signal to the optical line terminal through the optical fiber by using the adjusted sending parameter.

11. The method of claim 9, wherein instructing the optical network unit to adjust the transmission parameters comprises at least one of:

instructing to adjust the transmission parameter to a particular value.

12. The method of claim 9, wherein the transmission parameters comprise at least one of: the optical network unit uses the driving amplitude, bias current, modulation depth and transmitting power of the laser.

13. An optical line terminal comprising:

at least one processor; and

at least one memory including computer program instructions, the at least one memory and the computer program instructions configured to, with the at least one processor, cause the optical line terminal to perform the method of any of claims 1-8.

14. An optical network unit comprising:

at least one processor; and

at least one memory including computer program instructions, the at least one memory and the computer program instructions configured to, with the at least one processor, cause the optical network unit to perform the method of any of claims 9-12.

15. A computer readable medium comprising machine executable instructions that when executed cause a machine to perform the method of any one of claims 1-8.

16. A computer readable medium comprising machine executable instructions which, when executed, cause a machine to perform the method of any one of claims 9-12.