Electro-optical joint compensation method, device, equipment and storage medium

Abstract

The invention discloses an electro-optical joint compensation method, an electro-optical joint compensation device, electro-optical joint compensation equipment and a storage medium, and relates to the technical field of optical communication. Acquiring an initial receiving signal output after the transmitting end processes the digital subcarrier modulation signal into which the frequency domain pilot frequency is inserted; determining a crosstalk estimation matrix based on the initial received signal; based on the crosstalk estimation matrix, determining a cost function and optimization algorithm parameters for optimizing the Mach-Zehnder interferometer, and performing phase optimization on the Mach-Zehnder interferometer to completely eliminate mode coupling of the few-mode fiber; and acquiring frequency domain pilot frequency information of a target receiving signal output by the transmitting end after the mode coupling of the few-mode optical fiber is completely eliminated, and performing frequency offset compensation and phase noise compensation on the target receiving signal. Through the mode, the mode coupling dynamic state can be tracked in real time, and the actual performance of the optical domain multi-input multi-output equalizer in a dynamic channel environment is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical communication, and in particular to an electrical-optical joint compensation method and device, equipment and a storage medium. BACKGROUND

[0002] Due to the fact that the spatial channels of the mode multiplexer-demultiplexer of the current space division multiplexing connector cannot be well isolated, the intermodal crosstalk is usually relatively high (more than -20 dB), and with the increase of the transmission distance, the number of mode multiplexer-demultiplexers used by the link will also increase, resulting in further increase of the intermodal crosstalk. At the same time, the use of strongly coupled space division multiplexing optical fibers, as well as the imperfection of optical fiber design, disturbances caused by environmental or human factors, will also introduce intermodal crosstalk. Therefore, when the number of modes is large, a digital signal processing (DSP) of a multiple input multiple output (MIMO) is usually used to realize the de-crosstalk between modes, but the calculation complexity will increase by several orders of magnitude, which poses a challenge to large-scale digital signal processing integration. The optical domain MIMO equalizer can significantly alleviate the DSP resources, power consumption and delay in the electrical domain by decoupling the mode coupling in the optical domain. However, the existing mode decoupling system based on the optical domain MIMO equalizer mainly relies on an offline training strategy, which assumes that the mode coupling characteristics in the few-mode fibers (FMF) remain quasi-static, and under this assumption, the matrix parameters of the optical processor are trained to approximate the inverse matrix of the mode coupling matrix. These training methods are usually run in a non-signal transmission mode, and the input excitation port is switched by an optical switch, and power detection is performed at the output end of the processor to optimize the matrix parameters. However, time-varying factors such as random disturbance and temperature drift can cause dynamic changes in mode coupling characteristics within milliseconds, and the training period of the existing system is too long to track such rapid changes in real time, which greatly hinders the practical performance of the optical domain MIMO equalizer processor in a dynamic channel environment.

[0003] The above content is only used to assist in understanding the technical solutions of the present application and does not represent the acknowledgement of the above content as prior art. SUMMARY

[0004] The main purpose of the present application is to provide an electrical-optical joint compensation method, device, equipment and storage medium, which aims to solve the technical problem that the existing technology cannot track the dynamic changes of channel mode coupling characteristics in real time, affecting the practical performance of the optical domain MIMO equalizer in a dynamic channel environment.

[0005] To achieve the above object, the application provides an electro-optical joint compensation method applied to a receiving end of a space division coherent optical communication system, wherein the receiving end of the space division coherent optical communication system is provided with an optical domain multiple-input multiple-output equalizer, the optical domain multiple-input multiple-output equalizer at least comprises a Mach-Zehnder interferometer, a few-mode fiber is arranged in a transmission link between the receiving end and a transmitting end of the space division coherent optical communication system, the few-mode fiber is used for signal transmission, and the optical domain multiple-input multiple-output equalizer is used for mode decoupling. The electro-optical joint compensation method comprises the following steps. When the mode coupling of the few-mode fiber is not completely eliminated by the optical domain multiple-input multiple-output equalizer, an initial receiving signal output by the transmitting end after processing a digital sub-carrier modulation signal with an inserted frequency domain pilot is acquired. Based on the initial receiving signal, a crosstalk estimation matrix is determined. Based on the crosstalk estimation matrix, a cost function for optimizing the Mach-Zehnder interferometer and an optimization algorithm parameter are determined. Based on the cost function and the optimization algorithm parameter, phase optimization is performed on the Mach-Zehnder interferometer to completely eliminate the mode coupling of the few-mode fiber. After the mode coupling of the few-mode fiber is completely eliminated, a target receiving signal output by the transmitting end is acquired, and frequency offset compensation and phase noise compensation are performed on the target receiving signal.

[0006] In an embodiment, the step of determining the crosstalk estimation matrix based on the initial receiving signal comprises the following steps. Phase noise and frequency offset are acquired. A first correspondence relationship between the phase noise, the frequency offset, the initial receiving signal and matrix element values is acquired. Based on the phase noise, the frequency offset, the initial receiving signal and the first correspondence relationship, matrix element values at each position in the crosstalk estimation matrix are determined. Based on the matrix element values at each position in the crosstalk estimation matrix, the crosstalk estimation matrix is generated.

[0007] In an embodiment, the step of determining the cost function for optimizing the Mach-Zehnder interferometer and the optimization algorithm parameter based on the crosstalk estimation matrix comprises the following steps. Based on the crosstalk estimation matrix, a cost function is determined. Based on the target cost, an optimization algorithm parameter for optimizing the Mach-Zehnder interferometer is determined. Based on the structural features of the Mach-Zehnder interferometer, a plurality of phase optimization stages are set, and optimization objects of each phase optimization stage are determined in the Mach-Zehnder interferometer. updating the phases of the Mach-Zehnder interferometer based on the cost function to obtain the phase corresponding to the target cost of each phase optimization stage.

[0008] In an embodiment, the step of updating the phases of the Mach-Zehnder interferometer based on the cost function to obtain the phase corresponding to the target cost of each phase optimization stage comprises: determining a current phase optimization stage based on the stage index value; adjusting the cost function based on the optimization object of the current phase optimization stage to obtain a target cost function of the current phase optimization stage; applying a positive phase perturbation and a negative phase perturbation to the optimization object of the current phase optimization stage in sequence to determine a gradient of the current phase optimization stage; updating the optimization algorithm parameters based on the gradient of the current phase optimization stage to obtain the optimization algorithm parameters of the current phase optimization stage; updating the phase of the optimization object of the current phase optimization stage based on the optimization algorithm parameters of the current phase optimization stage to obtain an optimized phase of the optimization object of the current phase optimization stage; determining a current cost of the current phase optimization stage based on the optimized phase of the optimization object of the current phase optimization stage and the target cost function; when the current cost of the current phase optimization stage is less than or equal to a preset cost threshold, taking the optimized phase of the optimization object of the current phase optimization stage as the phase corresponding to the target cost, updating the stage index value, and returning to the step of determining a current phase optimization stage based on the stage index value.

[0009] In an embodiment, the step of applying a positive phase perturbation and a negative phase perturbation to the optimization object of the current phase optimization stage in sequence to determine a gradient of the current phase optimization stage comprises: applying a positive phase perturbation to the optimization object of the current phase optimization stage to obtain a positive cost of the current phase optimization stage; applying a negative phase perturbation to the optimization object of the current phase optimization stage to obtain a negative cost of the current phase optimization stage; determining the gradient of the current phase optimization stage based on the positive cost and the negative cost of the current phase optimization stage.

[0010] In an embodiment, the step of determining the gradient of the current phase optimization stage based on the positive cost and the negative cost of the current phase optimization stage comprises: obtaining a phase perturbation amount; obtaining a second correspondence relationship between the forward cost, the backward cost, the phase perturbation amount and the gradient; determining the gradient of the current phase optimization stage based on the forward cost and the backward cost of the current phase optimization stage, the phase perturbation amount and the second correspondence relationship.

[0011] In an embodiment, the optimization algorithm parameters at least include a momentum coefficient, and the step of updating the optimization algorithm parameters based on the gradient of the current phase optimization stage to obtain the optimization algorithm parameters of the current phase optimization stage includes: obtaining a momentum factor and a learning rate; obtaining a third correspondence relationship between the momentum factor, the gradient, the learning rate and the momentum coefficient; determining the momentum coefficient of the current phase optimization stage based on the momentum factor, the gradient of the current phase optimization stage, the learning rate and the third correspondence relationship.

[0012] In addition, to achieve the above object, the application further provides an electro-optical joint compensation device applied to a receiving end of a space division coherent optical communication system, wherein the receiving end of the space division coherent optical communication system is provided with an optical domain multiple-input multiple-output equalizer, the optical domain multiple-input multiple-output equalizer at least includes a Mach-Zehnder interferometer, a few-mode fiber is arranged in a transmission link between the receiving end and a transmitting end of the space division coherent optical communication system, the few-mode fiber is used for signal transmission, and the optical domain multiple-input multiple-output equalizer is used for mode decoupling. The electro-optical joint compensation device includes: A crosstalk estimation module is configured to obtain an initial receiving signal output by the transmitting end after processing a digital sub-carrier modulation signal with an inserted frequency domain pilot when the optical domain multiple-input multiple-output equalizer does not completely eliminate mode coupling of the few-mode fiber. The crosstalk estimation module is further configured to determine a crosstalk estimation matrix based on the initial receiving signal. A phase optimization module is configured to determine a cost function for optimizing the Mach-Zehnder interferometer and an optimization algorithm parameter. The phase optimization module is further configured to perform phase optimization on the Mach-Zehnder interferometer based on the cost function and the optimization algorithm parameter, so as to completely eliminate the mode coupling of the few-mode fiber. A joint compensation module is configured to obtain frequency domain pilot information of a target receiving signal output by the transmitting end after completely eliminating the mode coupling of the few-mode fiber, and perform frequency offset compensation and phase noise compensation on the target receiving signal.

[0013] In addition, to achieve the above object, the present application also provides an electro-optical joint compensation device, which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, and the computer program is configured to implement the steps of the electro-optical joint compensation method as described above.

[0014] In addition, to achieve the above object, the present application also provides a storage medium, which is a computer readable storage medium, and the storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the electro-optical joint compensation method as described above.

[0015] In addition, to achieve the above object, the present application also provides a computer program product, which comprises a computer program, and the computer program is executed by a processor to implement the steps of the electro-optical joint compensation method as described above.

[0016] The application provides an electro-optical joint compensation method, when mode coupling of a few-mode fiber is not completely eliminated by an optical domain multiple-input multiple-output equalizer, obtaining an initial receiving signal output by a transmitting end after processing a digital subcarrier modulation signal with an inserted frequency domain pilot; determining a crosstalk estimation matrix based on the initial receiving signal; determining a cost function of an optimized Mach-Zehnder interferometer and an optimization algorithm parameter based on the crosstalk estimation matrix; performing phase optimization on the Mach-Zehnder interferometer based on the cost function and the optimization algorithm parameter, so as to completely eliminate the mode coupling of the few-mode fiber; and obtaining frequency domain pilot information of a target receiving signal output by the transmitting end after the mode coupling of the few-mode fiber is completely eliminated, and performing frequency offset compensation and phase noise compensation on the target receiving signal. In the application, a frequency domain pilot is embedded in a digital subcarrier modulation (DSCM) signal to transmit channel transmission matrix information to a receiving end, digital signal processing of the receiving end obtains joint impairment data containing spatial channel crosstalk, frequency offset (FO) and phase noise (PN) by extracting the frequency domain pilot information, and a joint compensation mechanism in the optical domain and the electrical domain is adopted to realize spatial channel decoupling of space-division multiplexing (SDM) by using an optical domain multiple-input multiple-output equalizer based on Mach-Zehnder interferometers (MZI), and the frequency offset and the phase noise are compensated by digital signal processing in the electrical domain. Meanwhile, for a cascaded structure of the optical domain multiple-input multiple-output equalizer, a staged optimization strategy is introduced to accelerate the optimization process, significantly improve the training efficiency and convergence speed of the optical domain multiple-input multiple-output equalizer, and track the dynamic mode coupling in real time, improve the actual performance of the optical domain MIMO in a dynamic channel environment, and solve the technical problem that the dynamic change of the channel mode coupling characteristics cannot be tracked in real time, and the actual performance of the optical domain multiple-input multiple-output equalizer in the dynamic channel environment is affected. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings incorporated in and forming a part of the specification illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without creative labor.

[0019] Figure 1 Flowchart of the electro-optical joint compensation method embodiment one of the present application; Figure 2 The overall architecture schematic diagram of the electro-optical joint compensation method provided for Embodiment Two of the present application is shown in the figure below. Figure 3 The flowchart of the electro-optical joint compensation method of Embodiment Two of the present application is shown in the figure below. Figure 4 The optimization algorithm schematic diagram of the electro-optical joint compensation method provided for Embodiment Two of the present application is shown in the figure below. Figure 5 The module structure schematic diagram of the electro-optical joint compensation device of the present application is shown in the figure below. Figure 6 The device structure schematic diagram of the hardware running environment involved in the electro-optical joint compensation method of the present application is shown in the figure below.

[0020] The implementation, functional features and advantages of the present application will be further explained with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0021] It should be understood that the specific embodiments described herein are merely intended to explain the technical solutions of the present application, and are not intended to limit the present application.

[0022] In order to better understand the technical solutions of the present application, the following will be described in detail in conjunction with the accompanying drawings and specific embodiments.

[0023] The main solution of the present application is: when the mode coupling of the few-mode fiber is not completely eliminated by the optical domain multiple-input multiple-output equalizer, the initial receiving signal output by the transmitting end after processing the digital sub-carrier modulation signal with the inserted frequency domain pilot is obtained; based on the initial receiving signal, the crosstalk estimation matrix is determined; based on the crosstalk estimation matrix, the cost function of the optimized Mach-Zehnder interferometer and the optimization algorithm parameters are determined; based on the cost function and the optimization algorithm parameters, the phase of the Mach-Zehnder interferometer is optimized to completely eliminate the mode coupling of the few-mode fiber; the frequency domain pilot information of the target receiving signal output by the transmitting end after completely eliminating the mode coupling of the few-mode fiber is obtained, and the frequency offset compensation and the phase noise compensation are performed on the target receiving signal.

[0024] The application provides a solution, in which a pilot is embedded in a digital sub-carrier modulation signal at a transmitting end to transmit channel transmission matrix information to a receiving end, digital signal processing at the receiving end extracts joint impairment data containing spatial channel crosstalk, frequency offset and phase noise by extracting frequency domain pilot information, and a joint optical domain and electrical domain compensation mechanism is used to realize spatial channel decoupling of space division multiplexing by using an optical domain multiple-input multiple-output equalizer based on a Mach-Zehnder interferometer, and the frequency offset and phase noise are compensated by electrical domain digital signal processing. Meanwhile, for a cascaded structure of the optical domain multiple-input multiple-output equalizer, a staged optimization strategy is introduced to accelerate the optimization process, significantly improving the training efficiency and convergence speed of the optical domain multiple-input multiple-output equalizer, and real-time tracking of mode coupling dynamics is realized, improving the actual performance of the optical domain multiple-input multiple-output equalizer in a dynamic channel environment, and solving the technical problem that the actual performance of the optical domain multiple-input multiple-output equalizer in a dynamic channel environment is affected by the inability to real-time track the dynamic changes of channel mode coupling characteristics.

[0025] It should be noted that the execution subject of the embodiment can be a computing service device with data processing, network communication and program running functions, such as a tablet computer, a personal computer, a mobile phone, etc., or an electronic device capable of realizing the above functions, an electro-optical joint compensation device, etc., and the embodiment does not make specific limitation thereon. In the following, the electro-optical joint compensation device is taken as an example to describe the embodiment and each of the following embodiments, and the electro-optical joint compensation device is arranged at a receiving end of a space division coherent optical communication system.

[0026] The embodiment of the application provides an electro-optical joint compensation method, which is described with reference to Figure 1 , Figure 1 which is a flowchart of the first embodiment of the electro-optical joint compensation method of the application.

[0027] In the embodiment, the electro-optical joint compensation method includes steps S10-S50: Step S10, when the mode coupling of the few-mode fiber is not completely eliminated by the optical domain multiple-input multiple-output equalizer, an initial receiving signal output by the digital sub-carrier modulation signal with the inserted frequency domain pilot processed at the transmitting end is acquired; It should be noted that the embodiment is applied to a receiving end of a space division coherent optical communication system, and the receiving end is provided with an optical domain multiple-input multiple-output equalizer including a Mach-Zehnder interferometer, and the space division coherent optical communication system further includes a transmitting end, and at least a few-mode fiber is arranged in a transmission link between the transmitting end and the receiving end, the few-mode fiber is used for signal transmission, and the optical domain multiple-input multiple-output equalizer is used for mode decoupling.

[0028] In addition, it should be noted that the electro-optical joint compensation device is taken as an example to describe the embodiment and each of the following embodiments, and the electro-optical joint compensation device is arranged at a receiving end of a space division coherent optical communication system. Figure 2The receiving end is provided with a digital signal processor, a mode demultiplexer and an optical domain multiple-input and multiple-output equalizer, the transmitting end is provided with a digital-to-analog converter (DAC), a modulator and a mode multiplexer, the transmission link comprises a few-mode fiber, the digital-to-analog converter is used for converting the digital subcarrier multiplexing signal with the pilot into radio frequency signals (RFs1~RFsN) and inputting the radio frequency signals into the modulator, the modulator is used for modulating the radio frequency signals to obtain modulated light signals and inputting the modulated light signals into the mode multiplexer, the few-mode fiber is used for transmitting the mode division multiplexing optical signals to the mode demultiplexer, the mode demultiplexer is used for demultiplexing the modulated light signals to obtain demultiplexed light signals and inputting the demultiplexed light signals into the optical multiple-input and multiple-output equalizer for mode crosstalk decoupling to obtain corresponding decoupled signals, after being received by an integrated coherent receiver (ICR) and converted by an analog-to-digital converter (ADC), corresponding receiving end signals are obtained, crosstalk matrix estimation is performed in the receiving end digital signal processor to determine whether the mode coupling is completely eliminated, an optimization algorithm is used to update the phase of the Mach-Zehnder interferometer, the calculated phase value or corresponding voltage value is used to drive the Mach-Zehnder interferometer through a multi-channel voltage source or a field programmable gate array (FPGA), until the mode coupling is completely eliminated, and then frequency offset and phase noise are compensated by using frequency domain pilot information. In addition, the transmitting end is also provided with a laser and an optical beam splitter, and the receiving end is also provided with a local laser.

[0029] It can be understood that the pilot is inserted in the digital subcarrier modulation signal, and the signal is transmitted to the receiving end after being processed by the transmitting end. If the mode coupling of the few-mode fiber is not completely eliminated by the optical domain multiple-input and multiple-output equalizer, the receiving end digital signal processor performs crosstalk matrix estimation and updates the phase of the Mach-Zehnder interferometer by using an optimization algorithm, at this time, the signal obtained from the transmitting end is the initial receiving signal.

[0030] In step S20, a crosstalk estimation matrix is determined based on the initial receiving signal. It should be noted that the crosstalk estimation matrix is the estimated crosstalk matrix, denoted as The crosstalk estimation matrix represents the crosstalk information of the optical signals of multiple modes in the few-mode fiber, and the crosstalk information represents the mutual interference of the optical signals of multiple modes in the few-mode fiber.

[0031] It can be understood that the embodiment based on the frequency domain pilot determines the crosstalk estimation matrix, can estimate the channel crosstalk, frequency offset and phase noise at the same time, is not only helpful to realize the optical domain multiple-input multiple-output equalizer configuration, but also can effectively compensate the frequency offset and phase noise.

[0032] In a feasible implementation, the step S20 can include: acquiring the phase noise and the frequency offset; acquiring a first correspondence relationship between the phase noise, the frequency offset, the initial received signal and the matrix element value; determining the matrix element value of each position in the crosstalk estimation matrix based on the phase noise, the frequency offset, the initial received signal and the first correspondence relationship; and generating the crosstalk estimation matrix based on the matrix element value of each position in the crosstalk estimation matrix.

[0033] It should be noted that, assuming that the embodiment uses four modes for transmission, each digital subcarrier signal contains four subcarriers, and one frequency domain pilot is inserted in each digital subcarrier signal, the structure of the four digital subcarrier signals is as follows:

[0034] Among them, , and respectively represent the transmitted signal, the digital subcarrier signal carrying data and the pilot signal, the pilot power is determined by the pilot-to-signal power ratio, and the calculation relationship is as follows:

[0035] In the formula, PSPR (Pilot-to-signal Power Ratio) represents the pilot signal power ratio, represents the signal power, represents the amplitude of the pilot signal. After modulation, few-mode fiber transmission, optical multiple-input multiple-output equalizer processing and demodulation, the initial received signal can be represented as:

[0036] Among them, represents the frequency offset, represents the phase noise, and are the center frequency of the transmitter laser and the center frequency of the local oscillator (LO) of the receiver, respectively, and are the phase noise of the transmitter laser and the phase noise of the local oscillator, respectively.

[0037] It is understandable that the initial received signal is composed of the digital subcarrier signal and the pilot signal, and both are subject to the same system impairments. Therefore, the transmitted signal can be effectively recovered by referring to the pilot information. Due to the frequency shift, the pilot signal undergoes a frequency shift, and its position can be determined by finding the maximum spectral peak within a predefined frequency range (usually corresponding to the sub-band spacing of the digital subcarrier). Subsequently, a low-pass filter is used to extract the pilot signal. Each row of the matrix is ​​obtained by performing the above processing on the components of the initial received signal. The matrix element values ​​are the values ​​of each element in the crosstalk estimation matrix. The first correspondence between phase noise, frequency shift, the initial received signal, and the matrix element values ​​is the calculation formula for each element value in the crosstalk estimation matrix, as shown below:

[0038] In the formula, Indicates frequency offset. Indicates phase noise, This indicates low-pass filter operation. Indicates noise. The first received signal represents the... One portion, This indicates that the position in the crosstalk estimation matrix is The element value at that position, This represents the amplitude of the pilot signal. For example, the crosstalk estimation matrix... Each row corresponds to the components of the initial received signal according to the first correspondence mentioned above. After processing, we can obtain the matrix element values ​​in the first row:

[0039]

[0040]

[0041]

[0042] It should be understood that after completing the optical domain MIMO configuration, channel crosstalk is eliminated, and the crosstalk estimation matrix... It becomes:

[0043] In the formula, Indicates frequency offset. Indicates phase noise, This represents a fixed amount of phase rotation. This represents noise. These rotations are not corrected for in subsequent optimization processes because the loss function converges only in magnitude, without considering phase alignment. However, due to the crosstalk estimation matrix... These fixed phase components are inherently contained in the FO and PN, so they can be compensated together with FO and PN.

[0044] In step S30, a cost function of the optimized Mach-Zehnder interferometer and an optimization algorithm parameter are determined based on the crosstalk estimation matrix. It should be noted that the phase corresponding to the target cost is the phase of the Mach-Zehnder interferometer finally optimized. Since the mode coupling of the few-mode fiber is not completely eliminated by the optical domain MIMO equalizer at this time, the phase of the Mach-Zehnder interferometer corresponding to each mode of the few-mode fiber needs to be optimized.

[0045] In step S40, the phase of the Mach-Zehnder interferometer is optimized based on the cost function and the optimization algorithm parameter, so as to completely eliminate the mode coupling of the few-mode fiber. It can be understood that the driving voltage determined according to the optimization algorithm parameter can completely eliminate the mode coupling by driving the Mach-Zehnder interferometer through a multi-channel voltage source or a field programmable gate array. It should be noted that the optimization algorithm parameter at least includes a momentum coefficient.

[0046] In step S50, the frequency domain pilot information of the target received signal output by the transmitting end after completely eliminating the mode coupling of the few-mode fiber is obtained, and the target received signal is compensated for frequency offset and phase noise.

[0047] It should be noted that after completely eliminating the mode coupling of the few-mode fiber, the signal output by the transmitting end is reacquired, that is, the target received signal.

[0048] It should be noted that the target frequency offset, that is, the compensation amount of the frequency offset, is calculated according to the difference between the pilot frequency inserted by the digital subcarrier of the transmitting end and the pilot frequency inserted by the digital subcarrier of the receiving end. According to the pilot information filtered by the low-pass filter, the phase noise introduced by the transmitting end laser and the local oscillator can be estimated, that is, the compensation amount of the phase noise. The target received signal is compensated for frequency offset according to the estimated frequency offset, and is compensated for phase noise according to the estimated phase noise.

[0049] In addition, it should be noted that in the process of successfully realizing the optical channel decoupling of the optical domain MIMO equalizer, the receiving end digital signal processing additionally increases the optimization algorithm based on gradient descent, and the remaining part is consistent with the traditional pilot-based digital subcarrier receiving end digital signal processor flow, that is, the frequency domain pilot information is used to compensate for the frequency offset and the phase noise. According to the time-varying characteristics of the optical channel, the additional gradient optimization algorithm converges can be periodically run, rather than continuously run, to save power consumption.

[0050] It can be understood that the embodiment decouples the spatial channel in the optical domain, estimates the frequency offset and phase noise in the electrical domain through the frequency domain pilot, and compensates. The optical domain MIMO equalizer can be implemented based on the PIC chip of silicon light, so it can be integrated with the receiver chip and device, reducing power consumption and size. The use of the optical domain MIMO equalizer facilitates the reduction of system power consumption and cost, and reserves enough flexibility for the system to upgrade to more spatial channels (such as the number of modes) through the optical domain MIMO equalizer to reserve additional optical ports and optical equalization units.

[0051] It should be understood that the embodiment has the following advantages: ultra-large bandwidth and transparency, supporting transmission signals of any rate and any modulation format, while supporting multi-band signal processing through optimized design of the optical domain MIMO equalizer chip; fast response, high-speed channel damage estimation based on pilot and phased optimization strategy make the optical domain MIMO parameter configuration quickly converge, while having the ability to track the time-varying channel in real time; compatible with digital subcarrier system receiver digital signal processing, optical domain MIMO equalizer parameter configuration optimization and channel tracking algorithm can be completely embedded into the existing digital subcarrier coherent receiver digital signal processing architecture, without affecting the normal operation of the receiver digital signal processing flow; high integration of the optical domain MIMO equalizer, which can be well integrated with the integrated coherent receiver; good scalability, the system is easy to expand to higher channel number, for example, based on the optical domain MIMO equalizer of Mach-Zehnder interferometer, by reserving additional Mach-Zehnder interferometer units, when the number of spatial channels of the spatial division multiplexing system increases, the reserved Mach-Zehnder interferometer units can be activated.

[0052] The embodiment provides an electro-optical joint compensation method, when mode coupling of a few-mode fiber is not completely eliminated by an optical domain multiple-in multiple-out equalizer, obtaining an initial receiving signal output by a transmitting end after processing of a digital subcarrier modulation signal with an inserted pilot; determining a crosstalk estimation matrix based on the initial receiving signal; determining a cost function of an optimized Mach-Zehnder interferometer and an optimization algorithm parameter based on the crosstalk estimation matrix; performing phase optimization on the Mach-Zehnder interferometer based on the cost function and the optimization algorithm parameter, so as to completely eliminate the mode coupling of the few-mode fiber; and obtaining frequency domain pilot information of a target receiving signal output by the transmitting end after the mode coupling of the few-mode fiber is completely eliminated, and performing frequency offset compensation and phase noise compensation on the target receiving signal. The transmitting end transmits channel transmission matrix information to a receiving end by embedding a pilot in a digital subcarrier modulation signal, the digital signal processing of the receiving end obtains joint impairment data containing spatial channel crosstalk, frequency offset and phase noise by extracting frequency domain pilots, and adopts a joint optical domain and electrical domain compensation mechanism, uses the Mach-Zehnder interferometer optical domain multiple-in multiple-out equalizer to realize spatial channel decoupling of space division multiplexing, and compensates the frequency offset and the phase noise through the electrical domain digital signal processing, so that the mode coupling dynamic can be tracked in real time, and the actual performance of the optical domain multiple-in multiple-out equalizer in a dynamic channel environment is improved.

[0053] Based on the first embodiment of the application, the same or similar contents as the above-mentioned embodiment one can be referred to the above introduction, and will not be described in detail. On this basis, please refer to Figure 3 , and the step S30 can include steps S301-S304: In step S301, the cost function is determined based on the crosstalk estimation matrix. It should be noted that the phase of the Mach-Zehnder interferometer is updated by the optimization algorithm in the embodiment, so that the crosstalk estimation matrix Tends to be a unit diagonal matrix, thereby realizing channel crosstalk-free transmission. The cost function is defined in the embodiment, which is used for optimization based on the gradient descent algorithm. Taking four transmission modes as an example, the corresponding cost function can be expressed as:

[0054] In the formula, the cost function is represented as , the crosstalk estimation matrix is represented as , and the element value of the crosstalk estimation matrix at the position .

[0055] In step S302, the optimization algorithm parameter of the optimized Mach-Zehnder interferometer is determined based on the target cost. ​It should be noted that according to the cost function, the Mach-Zehnder interferometer is optimized using the Newton accelerated gradient (NAG) algorithm. It should be noted that in the actual scene, the optimization of the Mach-Zehnder interferometer is to update the phase by updating the applied voltage, and for the convenience of description, the embodiment is described by uniformly using "updating the phase". First, initialize the learning rate , momentum coefficient , momentum factor , phase disturbance , phase of the Mach-Zehnder interferometer , convergence threshold According to the characteristics of the Newton accelerated gradient algorithm, all the phases of the Mach-Zehnder interferometer need to be pre-updated, as follows:

[0056] In the formula, represents the pre-updated Mach-Zehnder interferometer phase, i.e. the initial phase, represents the Mach-Zehnder interferometer phase before updating, represents the momentum coefficient, represents the adjustment coefficient.

[0057] Step S303, based on the structural characteristics of the Mach-Zehnder interferometer, a plurality of phase optimization stages are set, and the optimization objects of each phase optimization stage in the Mach-Zehnder interferometer are determined; It can be understood that if all the Mach-Zehnder interferometers are optimized, the algorithm is easy to fall into a local optimal solution due to too many optimization parameters, therefore, according to the cascade structure characteristics (structural characteristics) of the optical multi-input and multi-output equalizer, the embodiment uses a staged optimization scheme to reduce the number of Mach-Zehnder interferometers optimized in each stage. Generally, a plurality of phase optimization stages can be set according to the number of Mach-Zehnder interferometers, and at least one Mach-Zehnder interferometer is set as an optimization object in each phase optimization stage.

[0058] Step S304, updating the phase of the Mach-Zehnder interferometer based on the target cost to obtain the phase corresponding to the target cost of each phase optimization stage.

[0059] In one possible implementation, step S304 can include steps A11-A17: Step A11, determining the current phase optimization stage based on the stage index value; It should be noted that the stage index value, i.e. the index value of the phase optimization stage, is used to determine the current optimization stage, i.e. the current phase optimization stage.

[0060] Step A12, based on the optimization object of the current phase optimization stage, adjust the cost function to obtain the target cost function of the current phase optimization stage; For example, the output of the output port 1 is only determined by 、 and The three Mach-Zehnder interferometers, during the optimization process, the three Mach-Zehnder interferometers can be optimized first to ensure that the output port 1 has only one mode output without other mode crosstalk. At this time, the cost function can be adjusted accordingly, and the target cost function of the current phase optimization stage is as follows:

[0061] Step A13, sequentially apply positive phase perturbation and negative phase perturbation to the optimization object of the current phase optimization stage to determine the gradient of the current phase optimization stage; It should be noted that the optimization object of the current phase optimization stage is sequentially subjected to positive perturbation and negative perturbation (for example, positive perturbation and negative perturbation are applied to 、 and ), and the gradient change corresponding to the phase of the Mach-Zehnder interferometer is calculated, and the gradient corresponding to the phase of each Mach-Zehnder interferometer is calculated according to the gradient change.

[0062] In a possible implementation, step A13 can include: applying positive phase perturbation to the optimization object of the current phase optimization stage to obtain the positive cost of the current phase optimization stage; applying negative phase perturbation to the optimization object of the current phase optimization stage to obtain the negative cost of the current phase optimization stage; based on the positive cost and the negative cost of the current phase optimization stage, determining the gradient of the current phase optimization stage.

[0063] It can be understood that, with reference to Figure 4 , the positive cost is calculated by applying positive phase perturbation to the optimization object of the current phase optimization stage, the negative cost is calculated by applying negative phase perturbation to the optimization object of the current phase optimization stage, and the gradient is calculated according to the positive cost and the negative cost .

[0064] In a possible implementation, based on the positive cost and the negative cost of the current phase optimization stage, the step of determining the gradient of the current phase optimization stage can include: obtaining the phase perturbation amount; obtaining a second correspondence relationship between the positive cost, the negative cost, the phase perturbation amount and the target gradient; based on the positive cost and the negative cost of the current phase optimization stage, the phase perturbation amount and the second correspondence relationship, determining the gradient of the current phase optimization stage.

[0065] It should be noted that the second correspondence relationship between the positive cost, the negative cost, the phase disturbance amount and the gradient, i.e., the calculation relationship of the target gradient, is as follows:

[0066] In the formula, denotes the gradient corresponding to each optimization object, denotes the positive cost, denotes the negative cost, denotes the phase disturbance amount. Wherein, the cost change corresponding to the phase of the Mach-Zehnder interferometer is .

[0067] Step A14, updating the optimization algorithm parameters based on the gradient of the current phase optimization stage, to obtain the optimization algorithm parameters of the current phase optimization stage; In a possible implementation, step A14 can include: obtaining a momentum factor and a learning rate; obtaining a third correspondence relationship between the momentum factor, the gradient, the learning rate and a momentum coefficient; determining the momentum coefficient of the current phase optimization stage based on the momentum factor, the target gradient of the current phase optimization stage, the learning rate and the third correspondence relationship.

[0068] It should be noted that the third correspondence relationship between the momentum factor, the gradient, the learning rate and the momentum coefficient, i.e., the calculation relationship used for updating the momentum coefficient, is as follows:

[0069] In the formula, denotes the target gradient, denotes the momentum coefficient of the last iteration, denotes the momentum coefficient of the current iteration, i.e., the updated momentum coefficient, denotes the learning rate.

[0070] Step A15, updating the phase of the optimization object of the current phase optimization stage based on the optimization algorithm parameters of the current phase optimization stage, to obtain the optimized phase of the optimization object of the current phase optimization stage; It can be understood that the current phase of the optimization object of the current phase optimization stage is updated according to the updated momentum coefficient, to obtain the optimized Mach-Zehnder interferometer phase, i.e., the optimized phase.

[0071] Step A16, determining the current cost of the current phase optimization stage based on the optimized phase of the optimization object of the current phase optimization stage and the target cost function; It can be understood that the current cost is calculated according to the optimization phase of the optimization object in the current phase optimization stage and the target cost function, and the current cost is compared with the set threshold (preset cost threshold).

[0072] In step A17, when the current cost of the current phase optimization stage is less than or equal to the preset cost threshold, the optimization phase of the optimization object in the current phase optimization stage is taken as the phase corresponding to the target cost, and the stage index value is updated, and the step of determining the current phase optimization stage based on the stage index value is returned.

[0073] It can be understood that if the current cost of the current phase optimization stage is less than or equal to the preset cost threshold, it means that the current phase optimization stage has been optimized, that is, the Newton accelerated gradient algorithm converges, and the optimization phase of the optimization object in the current phase optimization stage is the final phase. Then update the stage index value, return to step A11, and continue to optimize the phase of the Mach-Zehnder interferometer in the next phase optimization stage.

[0074] For example, three phase optimization stages are divided, if the current is the first phase optimization stage, only , and are optimized, and when the optimization is completed, the crosstalk estimation matrix will become the following form:

[0075] At this time, the output port 1 only has mode 1 output, and mode 1 has no output at other ports. Then continue to the second phase optimization stage, the second phase optimization stage only optimizes and , while keeping , and unchanged, to ensure that the output port 2 only has mode 2 output, and when the Newton accelerated gradient algorithm converges, the crosstalk estimation matrix further becomes:

[0076] Finally, the third phase optimization stage is performed to ensure that modes 3 and 4 are output from output ports 3 and 4, and the crosstalk estimation matrix will become a standard diagonal unit matrix:

[0077] At this point, the optical domain multi-input and multi-output equalizer completes the decoupling of the mode coupling in the few-mode fiber.

[0078] It can be understood that, under the condition of system optical signal-to-noise ratio (OSNR) OSNR=25dB, the traditional scheme (all Mach-Zehnder interferometers are optimized at the same time) has the disadvantage of slow convergence speed, and it converges when the iteration number reaches nearly 100 times, while the staged optimization scheme of the embodiment only needs a few iterations to converge, and the convergence speed is obviously improved.

[0079] It should be understood that the receiving end digital signal processing quickly estimates the channel comprehensive damage by reading the pilot information, including the optical channel spatial channel coupling matrix, the frequency offset and the phase noise, and the difference between the estimated coupling matrix and the target unit matrix will guide the adjustment of the driving voltage / current of the optical domain MIMO equalizer, thereby forming a stable feedback loop, that is, the pilot information is extracted and the channel coupling matrix is estimated, the cost function is calculated to guide the driving adjustment of the optical MIMO equalizer processor, and the optical domain MIMO equalizer parameter is updated, which can ensure that the system converges from the startup state and adaptively tracks the optical channel changes in real time. For the cascade structure of the optical domain MIMO equalizer, a staged optimization strategy is further introduced to speed up the convergence, significantly improve the training efficiency and convergence speed of the optical domain MIMO equalizer, and be able to track the mode coupling dynamics in real time.

[0080] The embodiment provides an electro-optical joint compensation method, determines a cost function based on a crosstalk estimation matrix, determines an optimization algorithm parameter of an optimized Mach-Zehnder interferometer based on a target cost, sets a plurality of phase optimization stages based on the structural characteristics of the Mach-Zehnder interferometer, and determines the optimization objects of each phase optimization stage in the Mach-Zehnder interferometer, and updates the current phase of the Mach-Zehnder interferometer based on the target cost to obtain the final phase corresponding to the optimization objects of each phase optimization stage. The transmitting end embeds a pilot in a digital subcarrier modulation signal to transmit channel transmission matrix information to the receiving end, the digital signal processing of the receiving end extracts the pilot to obtain joint damage data containing spatial channel crosstalk, frequency offset and phase noise, and adopts a joint compensation mechanism in the optical domain and the electrical domain, uses an optical domain MIMO equalizer based on the Mach-Zehnder interferometer to realize spatial channel decoupling of space division multiplexing, and compensates the frequency offset and the phase noise through the digital signal processing in the electrical domain. Meanwhile, for the cascade structure of the optical domain MIMO equalizer, a staged optimization strategy is introduced to speed up the convergence, significantly improve the training efficiency and convergence speed of the optical domain MIMO equalizer, and be able to track the mode coupling dynamics in real time, and improve the actual performance of the optical domain MIMO equalizer in the dynamic channel environment.

[0081] It should be noted that the above examples are only used for understanding the present application and do not constitute a limitation on the electro-optical joint compensation method of the present application, and more forms of simple transformation based on this technical concept are within the protection scope of the present application.

[0082] The application also provides an electro-optical joint compensation device, which is applied to a receiving end of a space division coherent optical communication system. Figure 5 The receiving end of the space division coherent optical communication system is provided with an optical domain multiple-input multiple-output equalizer, the optical domain multiple-input multiple-output equalizer at least comprises a Mach-Zehnder interferometer, and a few-mode fiber is arranged in a transmission link between the receiving end and a transmitting end of the space division coherent optical communication system, the few-mode fiber is used for signal transmission, and the optical domain multiple-input multiple-output equalizer is used for mode decoupling. The electro-optical joint compensation device comprises: A crosstalk estimation module 10 is configured to acquire an initial receiving signal output by the transmitting end after processing a digital sub-carrier modulated signal with an inserted frequency domain pilot when the optical domain multiple-input multiple-output equalizer does not completely eliminate mode coupling of the few-mode fiber. The crosstalk estimation module 10 is further configured to determine a crosstalk estimation matrix based on the initial receiving signal. A phase optimization module 20 is configured to determine a cost function for optimizing the Mach-Zehnder interferometer and an optimization algorithm parameter based on the crosstalk estimation matrix. The phase optimization module 20 is further configured to perform phase optimization on the Mach-Zehnder interferometer based on the cost function and the optimization algorithm parameter, so as to completely eliminate the mode coupling of the few-mode fiber. A joint compensation module 30 is configured to acquire frequency domain pilot information of a target receiving signal output by the transmitting end after completely eliminating the mode coupling of the few-mode fiber, and perform frequency offset compensation and phase noise compensation on the target receiving signal.

[0083] In a feasible implementation, the crosstalk estimation module 10 is further configured to acquire phase noise and frequency offset. A first correspondence relationship among the phase noise, the frequency offset, the initial receiving signal and matrix element values is acquired. Based on the phase noise, the frequency offset, the initial receiving signal and the first correspondence relationship, matrix element values at each position in the crosstalk estimation matrix are determined. Based on the matrix element values at each position in the crosstalk estimation matrix, the crosstalk estimation matrix is generated.

[0084] In a feasible implementation, the phase optimization module 20 is further configured to determine a cost function based on the crosstalk estimation matrix. Based on the target cost, an optimization algorithm parameter for optimizing the Mach-Zehnder interferometer is determined. Based on the structural features of the Mach-Zehnder interferometer, multiple phase optimization stages are set, and an optimization object of each phase optimization stage is determined in the Mach-Zehnder interferometer; Based on the cost function, the phase of the Mach-Zehnder interferometer is updated to obtain the phase corresponding to the target cost of each phase optimization stage.

[0085] In a feasible implementation, the phase optimization module 20 is further configured to determine a current phase optimization stage based on a stage index value; Based on the optimization object of the current phase optimization stage, the cost function is adjusted to obtain a target cost function of the current phase optimization stage; The optimization object of the current phase optimization stage is sequentially subjected to a positive phase disturbance and a negative phase disturbance to determine a gradient of the current phase optimization stage; Based on the gradient of the current phase optimization stage, the optimization algorithm parameter is updated to obtain an optimization algorithm parameter of the current phase optimization stage; Based on the optimization algorithm parameter of the current phase optimization stage, the phase of the optimization object of the current phase optimization stage is updated to obtain an optimized phase of the optimization object of the current phase optimization stage; Based on the optimized phase of the optimization object of the current phase optimization stage and the target cost function, a current cost of the current phase optimization stage is determined. When the current cost of the current phase optimization stage is less than or equal to a preset cost threshold, the optimized phase of the optimization object of the current phase optimization stage is taken as the phase corresponding to the target cost, and the stage index value is updated, and the step of determining the current phase optimization stage based on the stage index value is returned.

[0086] In a feasible implementation, the phase optimization module 20 is further configured to apply a positive phase disturbance to the optimization object of the current phase optimization stage to obtain a positive cost of the current phase optimization stage. A negative phase disturbance is applied to the optimization object of the current phase optimization stage to obtain a negative cost of the current phase optimization stage. Based on the positive cost and the negative cost of the current phase optimization stage, a gradient of the current phase optimization stage is determined.

[0087] In a feasible implementation, the phase optimization module 20 is further configured to obtain a phase disturbance amount; A second correspondence relationship between the positive cost, the negative cost, the phase disturbance amount, and the gradient is obtained; Based on the positive cost and the negative cost of the current phase optimization stage, the phase perturbation amount, and the second correspondence relationship, a gradient of the current phase optimization stage is determined.

[0088] In a feasible implementation, the phase optimization module 20 is further configured to obtain a momentum factor and a learning rate. A third correspondence relationship among the momentum factor, a target gradient, the learning rate, and a momentum coefficient is obtained. Based on the momentum factor, the gradient of the current phase optimization stage, the learning rate, and the third correspondence relationship, a momentum coefficient of the current phase optimization stage is determined.

[0089] The electro-optical joint compensation device provided in the application adopts the electro-optical joint compensation method in the above embodiments, and can solve the technical problem that the dynamic change of the channel mode coupling characteristic cannot be tracked in real time, and the actual performance of the optical domain multiple-input and multiple-output equalizer in a dynamic channel environment is affected. Compared with the prior art, the electro-optical joint compensation device provided in the application has the same beneficial effects as the electro-optical joint compensation method provided in the above embodiments, and other technical features in the electro-optical joint compensation device are the same as the features disclosed in the above embodiments, and thus will not be described here.

[0090] The application provides an electro-optical joint compensation device, which comprises at least one processor and a memory connected with the at least one processor in communication; the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the electro-optical joint compensation method in the above embodiment one.

[0091] Reference will be made to the following description Figure 6 which shows a structural schematic diagram of an electro-optical joint compensation device suitable for implementing the embodiments of the application. The electro-optical joint compensation device in the embodiments of the application can include, but is not limited to, mobile terminals such as mobile phones, notebook computers, digital broadcast receivers, PDAs (Personal Digital Assistant), PADs (Portable Application Description), PMPs (Portable Media Player), vehicle-mounted terminals (such as vehicle-mounted navigation terminals), and the like, and fixed terminals such as digital TVs, desktop computers, and the like. Figure 6 The electro-optical joint compensation device shown is only an example, and should not impose any limitation on the functions and use range of the embodiments of the application.

[0092] As Figure 6As shown, the electro-optical joint compensation device can include a processing device 1001 (e.g., a central processing unit, a graphics processing unit, etc.) that can perform various appropriate actions and processes according to programs stored in a ROM (Read Only Memory) 1002 or programs loaded from a storage device 1003 into a RAM (Random Access Memory) 1004. Various programs and data required for operation of the electro-optical joint compensation device are also stored in the RAM 1004. The processing device 1001, the ROM 1002, and the RAM 1004 are connected to each other through a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Generally, the following systems can be connected to the I / O interface 1006: input devices 1007 including, for example, a touch screen, a touch pad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; the storage device 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 1009. The communication device 1009 can allow the electro-optical joint compensation device to communicate wirelessly or by wire with other devices to exchange data. Although the electro-optical joint compensation device with various systems is shown in the figure, it should be understood that all the shown systems are not required to be implemented or possessed. More or fewer systems can be alternatively implemented or possessed.

[0093] In particular, according to embodiments of the present disclosure, the processes described above with reference to the flowcharts can be implemented as a computer software program. For example, embodiments of the present disclosure include a computer program product comprising a computer program carried on a computer readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network by a communication device, or installed from the storage device 1003, or installed from the ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the methods of embodiments of the present disclosure are performed.

[0094] The electro-optical joint compensation device provided by the present application adopts the electro-optical joint compensation method in the above-mentioned embodiments, and can solve the technical problem that the dynamic change of the channel mode coupling characteristic cannot be tracked in real time, affecting the actual performance of the optical domain multiple-input multiple-output equalizer in a dynamic channel environment. Compared with the prior art, the electro-optical joint compensation device provided by the present application has the same beneficial effects as the electro-optical joint compensation method provided by the above-mentioned embodiments, and other technical features in the electro-optical joint compensation device are the same as the features disclosed in the previous embodiment method, which will not be repeated here.

[0095] It should be understood that various aspects of the disclosure can be implemented in hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any appropriate manner in any one or more embodiments or examples.

[0096] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0097] The present application provides a computer readable storage medium having computer readable program instructions (i.e. computer programs) stored thereon, the computer readable program instructions being used to execute the electro-optical joint compensation method in the above embodiments.

[0098] The computer readable storage medium provided by the present application may, for example, be a U disk, but is not limited to an electric, magnetic, optical, electromagnetic, infrared, or semiconductor system, system or device, or any combination of the above. More specific examples of the computer readable storage medium can include, but are not limited to: an electric connection with one or more conductive wires, a portable computer disk, a hard disk, a random access memory (RAM: Random Access Memory), a read-only memory (ROM: Read Only Memory), an erasable programmable read-only memory (EPROM: Erasable Programmable Read Only Memory or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM: CD-Read Only Memory), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present embodiment, the computer readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, system or device. The program code contained on the computer readable storage medium can be transmitted by any appropriate medium, including but not limited to: electric wires, optical cables, RF (Radio Frequency: Radio Frequency), etc., or any suitable combination of the above.

[0099] The above computer readable storage medium can be contained in the electro-optical joint compensation device; or can exist separately without being assembled into the electro-optical joint compensation device.

[0100] The computer readable storage medium described above carries one or more programs, when the one or more programs are executed by the electro-optical joint compensation device, the electro-optical joint compensation device: obtains an initial received signal output by a transmitting end after processing a digital subcarrier modulation signal in which a frequency domain pilot is inserted, when a mode coupling of a few-mode fiber is not completely eliminated by an optical domain multiple-input multiple-output equalizer; determines a crosstalk estimation matrix based on the initial received signal; determines a cost function of an optimized Mach-Zehnder interferometer and an optimization algorithm parameter based on the crosstalk estimation matrix; performs phase optimization on the Mach-Zehnder interferometer based on the cost function and the optimization algorithm parameter, so as to completely eliminate the mode coupling of the few-mode fiber; and obtains frequency domain pilot information of a target received signal output by the transmitting end after the mode coupling of the few-mode fiber is completely eliminated, and performs frequency offset compensation and phase noise compensation on the target received signal.

[0101] Computer program code for carrying out operations of the present application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0102] The flow diagrams and the block diagrams in the drawings are illustrations of architectures, functionalities, and operations of possible implementations of systems, methods, and computer program products according to various embodiments of present application. In this regard, each block in the flow diagrams or block diagrams can represent a module, a segment, or a portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks can occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently or the blocks may

[0103] The modules described in the embodiments of the present application can be implemented in the form of software or in the form of hardware. In some cases, the name of the module does not constitute a limitation on the module itself.

[0104] The readable storage medium provided by the present application is a computer readable storage medium, which stores computer readable program instructions (i.e., a computer program) for executing the above-mentioned electro-optical joint compensation method, and can solve the technical problem that the dynamic change of the channel mode coupling characteristics cannot be tracked in real time, and the actual performance of the optical domain MIMO in the dynamic channel environment is affected. Compared with the prior art, the computer readable storage medium provided by the present application has the same beneficial effects as the electro-optical joint compensation method provided by the above-mentioned embodiments, which will not be repeated here.

[0105] The present application also provides a computer program product, which includes a computer program, and the computer program is executed by a processor to implement the steps of the above-mentioned electro-optical joint compensation method.

[0106] The computer program product provided by the present application can solve the technical problem that the dynamic change of the channel mode coupling characteristics cannot be tracked in real time, and the actual performance of the optical domain MIMO in the dynamic channel environment is affected. Compared with the prior art, the computer program product provided by the present application has the same beneficial effects as the electro-optical joint compensation method provided by the above-mentioned embodiments, which will not be repeated here.

[0107] The above is only some embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation made by using the content of the present application specification and drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A method for electro-optical joint compensation, characterized in that, The electro-optical joint compensation method is applied to the receiver of a space-division coherent optical communication system. The receiver of the space-division coherent optical communication system is equipped with an optical domain MIMO equalizer. The optical domain MIMO equalizer includes at least a Mach-Zehnder interferometer. The transmission link between the receiver and the transmitter of the space-division coherent optical communication system is equipped with a few-mode fiber. The few-mode fiber is used for signal transmission, and the optical domain MIMO equalizer is used for mode decoupling. The electro-optical joint compensation method includes: When the optical domain multiple-input multiple-output equalizer does not completely eliminate the mode coupling of the few-mode fiber, the initial received signal output by the transmitter after processing the digital subcarrier modulation signal of the inserted frequency domain pilot is obtained. Based on the initial received signal, determine the crosstalk estimation matrix; Based on the crosstalk estimation matrix, the cost function and optimization algorithm parameters for optimizing the Mach-Zehnder interferometer are determined. Based on the cost function and the optimization algorithm parameters, the Mach-Zehnder interferometer is phase optimized to completely eliminate mode coupling in the few-mode fiber; The frequency domain pilot information of the target received signal output by the transmitter after completely eliminating mode coupling in the few-mode fiber is obtained, and frequency offset compensation and phase noise compensation are performed on the target received signal.

2. The method as described in claim 1, characterized in that, The step of determining the crosstalk estimation matrix based on the initial received signal includes: Obtain phase noise and frequency shift; Obtain the first correspondence between phase noise, frequency offset, initial received signal and matrix element values; Based on the phase noise, the frequency offset, the initial received signal, and the first correspondence, the matrix element values ​​at each position in the crosstalk estimation matrix are determined; A crosstalk estimation matrix is ​​generated based on the matrix element values ​​at each position in the crosstalk estimation matrix.

3. The method as described in claim 1, characterized in that, The step of determining the cost function and optimization algorithm parameters for optimizing the Mach-Zehnder interferometer based on the crosstalk estimation matrix includes: Based on the crosstalk estimation matrix, determine the cost function; Based on the target cost, the optimization algorithm parameters for optimizing the Mach-Zehnder interferometer are determined; Based on the structural features of the Mach-Zehnder interferometer, multiple phase optimization stages are set up, and the optimization objects of each phase optimization stage are determined in the Mach-Zehnder interferometer. Based on the cost function, the phase of the Mach-Zehnder interferometer is updated to obtain the phase corresponding to the target cost of each phase optimization stage.

4. The method as described in claim 3, characterized in that, The step of updating the phase of the Mach-Zehnder interferometer based on the cost function to obtain the phase corresponding to the target cost of each phase optimization stage includes: The current phase optimization stage is determined based on the stage index value; Based on the optimization object of the current phase optimization stage, the cost function is adjusted to obtain the target cost function of the current phase optimization stage; Positive and negative phase perturbations are applied sequentially to the optimization object in the current phase optimization stage to determine the gradient of the current phase optimization stage. Based on the gradient of the current phase optimization stage, the optimization algorithm parameters are updated to obtain the optimization algorithm parameters of the current phase optimization stage. Based on the optimization algorithm parameters of the current phase optimization stage, the phase of the optimization object in the current phase optimization stage is updated to obtain the optimized phase of the optimization object in the current phase optimization stage. Based on the optimized phase and target cost function of the optimization object in the current phase optimization stage, the current cost of the current phase optimization stage is determined. When the current cost of the current phase optimization stage is less than or equal to a preset cost threshold, the optimized phase of the optimization object in the current phase optimization stage is taken as the phase corresponding to the target cost, the stage index value is updated, and the process returns to the step of determining the current phase optimization stage based on the stage index value.

5. The method as described in claim 4, characterized in that, The step of sequentially applying positive and negative phase perturbations to the optimization object in the current phase optimization stage and determining the gradient of the current phase optimization stage includes: Apply a positive phase perturbation to the optimization object in the current phase optimization stage to obtain the positive cost of the current phase optimization stage; A negative phase perturbation is applied to the optimization object in the current phase optimization stage to obtain the negative cost of the current phase optimization stage; The gradient of the current phase optimization stage is determined based on the positive and negative costs of the current phase optimization stage.

6. The method as described in claim 5, characterized in that, The step of determining the gradient of the current phase optimization stage based on the positive and negative costs of the current phase optimization stage includes: Obtain the phase perturbation amount; Obtain the second correspondence between positive cost, negative cost, phase perturbation amount and gradient; The gradient of the current phase optimization stage is determined based on the positive and negative costs of the current phase optimization stage, the phase perturbation amount, and the second correspondence.

7. The method as described in claim 4, characterized in that, The optimization algorithm parameters include at least a momentum coefficient. The step of updating the optimization algorithm parameters based on the gradient of the current phase optimization stage to obtain the optimization algorithm parameters for the current phase optimization stage includes: Obtain the momentum factor and learning rate; Obtain the third correspondence between momentum factor, gradient, learning rate and momentum coefficient; Based on the momentum factor, the gradient of the current phase optimization stage, the learning rate, and the third correspondence, the momentum coefficient of the current phase optimization stage is determined.

8. An electro-optical combined compensation device, characterized in that, The electro-optical joint compensation device performs the electro-optical joint compensation method as described in any one of claims 1 to 7, and the electro-optical joint compensation device comprises: The crosstalk estimation module is used to obtain the initial received signal output by the transmitter after processing the digital subcarrier modulation signal of the inserted frequency domain pilot when the optical domain MIMO equalizer has not completely eliminated the mode coupling of the few-mode fiber. The crosstalk estimation module is further configured to determine a crosstalk estimation matrix based on the initial received signal; The phase optimization module is used to determine the cost function and optimization algorithm parameters for optimizing the Mach-Zehnder interferometer in the optical domain multi-input multi-output equalizer. The phase optimization module is further configured to perform phase optimization on the Mach-Zehnder interferometer based on the cost function and the optimization algorithm parameters, so as to completely eliminate mode coupling of the few-mode fiber. The joint compensation module is used to obtain the frequency domain pilot information of the target received signal output by the transmitter after completely eliminating the mode coupling of the few-mode fiber, and to perform frequency offset compensation and phase noise compensation on the target received signal.

9. An electro-optical combined compensation device, characterized in that, The device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the electro-optical joint compensation method as described in any one of claims 1 to 7.

10. A storage medium, characterized in that, The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, it implements the steps of the electro-optical joint compensation method as described in any one of claims 1 to 7.

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