Symbol-dependent nonlinear phase noise compensation method in optical communication system

Abstract

The invention relates to the technical field of optical signal processing, in particular to a symbol-related nonlinear phase noise compensation method in an optical communication system. According to the method, symbol-related phase noise is recorded by designing a lookup table, corresponding noise is read according to the lookup table of sent data in the data sending process, and phase noise pre-compensation is completed at a sending end; symbol-related nonlinear phase noise caused by SPM, bandwidth limitation, optical fiber dispersion and other factors is effectively eliminated, and then the power budget of the whole system is remarkably improved. The PD-NLPC is ingeniously deployed at the OLT sending end, sharing of multiple ONUs is achieved, and therefore the average cost is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of optical signal processing, and more specifically, to a method for compensating symbol-correlated nonlinear phase noise in an optical communication system. Background Art

[0002] 50G optical access based on intensity modulation and direct detection (IM / DD) has been standardized to meet the current high-bandwidth business needs. Looking to the future, the next generation of optical access is expected to reach a single wavelength transmission rate of 100Gbps or even higher. If the traditional IM / DD system is used to support optical access at this rate, it will face severe challenges in terms of high capacity and power budget. Compared with the traditional IM / DD system, the coherent detection system has higher capacity, power budget and rate scalability, and can better meet the needs of the next generation of high-speed short-distance optical access. In recent years, the application of coherent sinking in high-speed short-distance optical access scenarios has become a research hotspot.

[0003] In coherent optical access networks, the optical power input to the optical line terminal (OLT) is usually increased as much as possible to improve the system power budget. However, high optical power input often leads to severe self-phase modulation (SPM), which causes severe nonlinear phase noise. In the absence of bandwidth limitation and fiber dispersion, this nonlinear phase noise is usually only related to the signal power at the current moment. The nonlinear noise pre-compensation (NLPC) technology, which constructs phase noise using the current signal power and pre-compensates it in advance at the OLT transmitter, has been widely studied to reduce the nonlinear phase noise introduced by SPM in optical access networks. However, in actual systems, bandwidth limitation and fiber dispersion are always present in optical access network systems. The nonlinear phase noise caused by SPM will show symbol correlation under the combined effect of bandwidth limitation and fiber dispersion. If the nonlinear phase noise is constructed only based on the power of the signal at the current moment, it is difficult to eliminate this type of symbol-correlated nonlinear phase noise. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiency of the prior art that it is difficult to eliminate symbol-correlated nonlinear phase noise, and to provide a method for compensating symbol-correlated nonlinear phase noise in an optical communication system, which effectively eliminates symbol-correlated nonlinear phase noise and thus significantly improves the power budget of the overall system.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A method for pre-compensating symbol-correlated nonlinear phase noise in an optical communication system is provided, comprising the following steps:

[0007] S1. Generate a lookup table based on the transmitted symbol, whose table size is M 2L+1, where M represents the modulation order; the length of the transmission symbol Y(kL:k:k+L) is 2L+1, representing a symbol combination in the table; after the lookup table is generated, the phase error in the table is initialized to 0;

[0008] S2. After initializing the lookup table, the training sequence Y is converted into optical fiber and imported into the optical fiber for transmission. The receiving end uses digital signal processing to eliminate other channel damage and obtain the recovery sequence Y';

[0009] S3. Use the sliding window to select a length of 2L+1, calculate the combined position index in the lookup table, and calculate the corresponding phase noise e(k);

[0010] S4. As the sliding window moves forward, more and more data are stored in the lookup table. The parameter N(i) is used to record the number of data stored in the lookup table index i. The final data in each lookup table index i is the average of all phase noises e(k).

[0011] S5. Arrange the lookup table at the OLT transmitting end for pre-distortion of the transmitted data.

[0012] The present invention discloses a method for pre-compensating symbol-correlated nonlinear phase noise in an optical communication system. The method records the symbol-correlated phase noise by designing a lookup table, reads the corresponding noise according to the transmitted data in the table during the data transmission process, and completes the phase noise pre-compensation at the transmitting end. The method effectively eliminates the symbol-correlated nonlinear phase noise caused by factors such as SPM, bandwidth limitation, and fiber dispersion, thereby significantly improving the power budget of the overall system.

[0013] Preferably, in step S3, e(k) is obtained by calculating the phase difference between the symbol combination center symbol Y(k) and the corresponding restored symbol Y'(k):

[0014]

[0015] As the sliding window moves forward, more and more data are stored in the lookup table. The parameter N(i) is used to record the number of data stored in the lookup table index i. The final data in each lookup table index i is the average of all phase noises e(k).

[0016] Preferably, in step S4, the average of all phase noises e(k) is calculated by the following formula:

[0017] LUT(i)=LUT(i)+e(k)

[0018] N(i)=N(i)+1

[0019] LUT(i)_e(k)=LUT(i) / N(i)

[0020] Where LUT(i)_e(k) is the final phase noise in each lookup table index i. Once the lookup table based on various possible modes is established, it can be deployed to the OLT transmitter for pre-distortion of transmitted data.

[0021] Preferably, in step S5, the pre-distortion process includes:

[0022] X'(k)=X(k)×exp(j×LUT_e).

[0023] In a dual-polarization system, the phase noise in the current polarization signal is not only related to the current polarization signal, but also affected by the power of the other polarization signal. Applying the lookup table technology to the dual-polarization system to simultaneously compensate for the phase noise introduced by the current polarization and the other polarization will significantly increase the size of the lookup table, which is not conducive to actual commercial deployment. To solve this problem, the lookup table is only used to compensate for the nonlinear phase noise caused by the current polarization signal SPM, bandwidth limitation, and fiber dispersion. The nonlinear phase noise introduced by other polarization signals is compensated by traditional NLPC.

[0024] Preferably, for a dual polarization system, firstly, each polarization state is independently operated using method steps S1 to S4 to compensate for the sign-correlated nonlinear phase noise in each polarization state; then, the noise pre-compensation method NLPC is used to compensate for the nonlinear phase noise introduced by the other polarization state.

[0025] Preferably, for a dual polarization system, the symbol combination in the X and Y polarization states is the same, and in the process of storing symbols, a storage mechanism that conforms to combination sharing is adopted. In order to further reduce the size of the lookup table in the dual polarization system, the present invention proposes a table sharing mechanism. Since the symbol combination in the X and Y polarization states is the same, the symbol combination can be shared, thereby effectively reducing the storage space of the symbol combination. It is worth noting that this PD-NLPC (symbol-dependent nonlinear noise precompensation) is cleverly deployed at the OLT transmitter, realizing the sharing of multiple ONUs, thereby effectively reducing the average cost.

[0026] The present invention also provides a method for compensating symbol-correlated nonlinear phase noise in an optical communication system, comprising:

[0027] Transmitter digital signal processing DSP:

[0028] First, bit-to-QAM mapping is performed to generate a 16QAM signal; then, the noise pre-compensation method described in any one of claims 1 to 4 is applied to perform symbol-related nonlinear phase noise pre-compensation; the generated signal is then digitally up-sampled and pulse-shaped using a raised cosine filter; after pulse shaping, NLPC is applied to compensate for nonlinear phase noise introduced by other polarizations; then, a 32Gbaud 16QAM signal is generated by an arbitrary waveform generator;

[0029] Receiver digital signal processing DSP:

[0030] First, the orthogonalization process and dispersion compensation are carried out; then, a raised cosine filter with the same roll-off factor as the DSP at the transmitting end is used for matched filtering; then, the cascaded multi-mode algorithm CMMA is used for signal equalization to reduce the influence of the system band limitation; then, the frequency offset estimation FOE and the carrier phase estimation CPE are used for phase noise compensation; then, the multiple-input multiple-output algorithm MIMO is applied to solve the IQ imbalance problem at the transmitter end; finally, the recovered signal is demodulated by QAM and the bit error rate is calculated.

[0031] Preferably, the roll-off factor used is 1 / 8; at the transmitting end DSP, a 32Gbaud 16QAM signal is generated by a 64GSa / s 8-bit arbitrary waveform generator AWG; at the receiving end DSP, a 25-tap cascaded multi-mode algorithm CMMA is used; and a 3-tap 4x4 real multiple-input multiple-output algorithm MIMO is applied.

[0032] The present invention also provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above-described method when executing the computer program.

[0033] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the above method are implemented.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The symbol-correlated nonlinear phase noise compensation method in the optical communication system of the present invention records the symbol-correlated phase noise by designing a lookup table, and reads the corresponding noise according to the sent data in the data transmission process, and completes the phase noise pre-compensation at the transmitting end; effectively eliminates the symbol-correlated nonlinear phase noise caused by factors such as SPM, bandwidth limitation, and fiber dispersion, thereby significantly improving the power budget of the overall system. This PD-NLPC is cleverly deployed at the OLT transmitting end, realizing the sharing of multiple ONUs, thereby effectively reducing the average cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the PD-NLPC principle in the single polarization system of the present invention.

[0037] Figure 2 This is a schematic diagram of the PD-NLPC principle in the dual-polarization system of the present invention.

[0038] Figure 3 It is a schematic diagram of the principle of the lookup table sharing mechanism in the dual polarization system of the present invention.

[0039] Figure 4 The following is a schematic diagram of the experimental device and digital signal processing of the second embodiment of the present invention, wherein DSP: digital signal processing; QAM: quadrature amplitude modulation; CMMA: cascaded multi-mode algorithm; MIMO: multiple input multiple output; LO: local oscillator.

[0040] Figure 5 Schematic diagram of simulation results, where (a) the relationship between BER and ROP when the optical power input to the fiber is 12dBm and (b) 13dBm. (c) The relationship between the optical power budget and the optical power input to the fiber. NLPC: nonlinear noise precompensation; PD-NLPC: symbol-dependent nonlinear noise precompensation.

[0041] Figure 6 Schematic diagram of experimental results, including (a) the relationship between BER and ROP when the optical power input to the fiber is 12dBm and (b) 13dBm. (c) The relationship between the optical power budget and the optical power input to the fiber. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0043] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] Embodiment 1

[0045] This embodiment is the first embodiment of a method for pre-compensating symbol-correlated nonlinear phase noise in an optical communication system. The pre-compensation technology based on a lookup table is widely used in IM / DD systems and coherent systems to compensate for symbol-correlated amplitude nonlinear distortion due to its simple characteristics. In this embodiment, the modification and extension of the pre-compensation technology is applied to compensate for symbol-correlated phase nonlinear distortion in an optical access network for the first time, and the pre-compensation technology is called PD-NLPC. The principle is as follows: Figure 1 As shown. The length of the transmission symbol Y(kL:k:k+L) is 2L+1, representing a symbol combination in the table. In subsequent experiments, L is set to 1. First, a lookup table is generated based on the transmission symbol, and its table size is M 2L+1 , where M represents the modulation order. After the lookup table is generated, the phase error in the table is initialized to 0. After the lookup table is initialized, the training sequence is converted to optical fiber and imported into the optical fiber transmission. The receiving end uses digital signal processing to eliminate other channel damage and obtain the recovery sequence Y'. Then, a sliding window is used to select a length of 2L+1, and the combination position index in the lookup table is calculated, and the corresponding phase noise e(k) is calculated. Where e(k) is obtained by calculating the phase difference between the symbol combination center symbol Y(k) and the corresponding recovery symbol Y'(k), that is:

[0046]

[0047] As the sliding window moves forward, more and more data are stored in the lookup table. The parameter N(i) is used to record the number of data stored in the lookup table index i. The final data in each lookup table index i is the average of all phase noise e(k). The specific calculation process is:

[0048] LUT(i)=LUT(i)+e(k)(2)

[0049] N(i)=N(i)+1(3)

[0050] LUT(i)_e(k)=LUT(i) / N(i)(4)

[0051] LUT(i)_e(k) is the final phase noise in each lookup table index i. Once the lookup table based on various possible modes is established, it can be deployed to the OLT transmitter for pre-distortion of transmitted data. The specific pre-distortion process is as follows:

[0052] X'(k)=X(k)×exp(j×LUT_e)(5)

[0053] In a dual-polarization system, the phase noise present in the current polarization signal is not only related to the current polarization signal, but also affected by the power of the other polarization signal. Applying the lookup table technology to the dual-polarization system to simultaneously compensate for the phase noise introduced by the current polarization and the other polarization will significantly increase the size of the lookup table, which is not conducive to actual commercial deployment. To solve this problem, the lookup table is only used to compensate for the nonlinear phase noise caused by the current polarization signal SPM, bandwidth limitation, and fiber dispersion. The nonlinear phase noise introduced by other polarization signals is compensated by traditional NLPC. Therefore, the process of PD-NLPC in a dual-polarization system is as follows: Figure 2As shown. First, the lookup table technology is used to operate each polarization state independently to compensate for the sign-correlated nonlinear phase noise in each polarization state. Then, NLPC is applied to deal with the nonlinear phase noise introduced by the other polarization state. In order to further reduce the size of the lookup table in the dual-polarization system, this patent proposes a table sharing mechanism, the principle of which is as follows Figure 3 As shown in the figure. Since the symbol combinations in the X and Y polarization states are the same, the symbol combinations can be shared, thereby effectively reducing the storage space of the symbol combinations. It is worth noting that this PD-NLPC is cleverly deployed at the OLT transmitter, realizing the sharing of multiple ONUs, thereby effectively reducing the average cost.

[0054] This embodiment makes innovative improvements on the basis of traditional NLPC and proposes a PD-NLPC scheme, which aims to eliminate symbol-related nonlinear phase noise caused by factors such as SPM, bandwidth limitation, and fiber dispersion, thereby significantly improving the power budget of the overall system. In this embodiment, a low-cost lookup table is used to record symbol-related nonlinear phase noise, and in the data transmission stage, the corresponding noise is found and compensated by constructing a symbol combination. This PD-NLPC is cleverly deployed at the OLT transmitting end, realizing the sharing of multiple ONUs, thereby effectively reducing the average cost.

[0055] Embodiment 2

[0056] In this embodiment, a method for compensating symbol-correlated nonlinear phase noise in an optical communication system is provided. The digital signal processing flow is as follows: Figure 4 shown.

[0057] Transmitter digital signal processing DSP:

[0058] First, bit-to-QAM mapping is performed to generate a 16QAM signal; then, the noise pre-compensation method described in Example 1 is applied to perform symbol-related nonlinear phase noise pre-compensation; the generated signal is then digitally up-sampled and pulse-shaped using a raised cosine filter with a roll-off factor of 1 / 8; after pulse shaping, NLPC is applied to compensate for nonlinear phase noise introduced by other polarizations; and then, a 32Gbaud 16QAM signal is generated by a 64GSa / s 8-bit arbitrary waveform generator (AWG).

[0059] Receiver digital signal processing DSP:

[0060] The DSP at the receiving end includes Gram-Schmidt orthogonalization process (GSOP) and chromatic dispersion (CD) compensation to reduce the damage caused by receiver IQ imbalance and fiber CD. A raised cosine filter with the same roll-off factor as the transmitting DSP is used for matched filtering; then, a 25-tap cascaded multi-mode algorithm CMMA is used for signal equalization to reduce the influence of system band limitation; then, frequency offset estimation FOE and carrier phase estimation CPE are used for phase noise compensation; then, a 3-tap 4x4 real multiple input multiple output algorithm MIMO is applied to solve the IQ imbalance problem at the transmitter end; finally, the recovered signal is demodulated by QAM and the bit error rate is calculated.

[0061] In order to verify the effectiveness of the solution proposed in this patent, a comparative experiment was carried out. Figure 4 The digital signal processing (DSP) flow chart and experimental device diagram of this experiment are given.

[0062] Experimental setup: A dual-polarization IQ modulator is used to achieve electro-optical conversion, where the input 1550nm light source is provided by an external cavity laser (ECL) with a linewidth of 100kHz. Before the optical signal is introduced into the optical fiber, the EDFA is used to control the optical power of the signal to maximize the power budget of the signal. At the receiving end, a variable optical attenuator (VOA) is used to adjust the receiving optical power (ROP) of the signal, and then the coherent receiver chip (ICR) performs signal detection. The received signal is captured by an 80GSa / s analog-to-digital converter (ADC).

[0063] Result analysis:

[0064] First, a joint simulation was performed using MATLAB and VPI to simulate the transmission of a 256Gbps 16QAM signal over a 40km single-mode fiber. In the simulation, the linewidth of the transmitter laser was set to 100kHz, with a frequency offset of 1GHz from the far-end LO. The DSP was consistent with the program used in the experimental setup. The simulation results are shown in Figure 2. Figure 5 shown. Figure 5 (a) shows the simulation results of 256Gbps 16QAM signal with an input optical power of 12dBm and 40km single-mode fiber transmission. -2 ,NLPC improves the ROP performance by about 1.5 dB. In addition, the proposed PD-NLPC provides an additional enhancement of about 0.8 dB. Figure 5 (b) shows the result when the input optical power is 13 dBm. Without nonlinear phase noise pre-compensation, the BER performance is poor and cannot reach 1×10 -2 After implementing NLPC, significant improvement was observed. The signal processed by PD-NLPC was-2 An additional 1.5dB ROP improvement was achieved. Figure 5 (c) in Figure 1 shows the simulation results of the optical power budget of a 256Gbps 16QAM signal under different schemes as the input optical power changes. In the cases without precompensation, using NLPC, and using PD-NLPC, the optimal input optical power is 11dBm, 12dBm, and 12dBm, respectively, and the optical power budget is 44.6dB, 45.6dB, and 46.4dB, respectively. Therefore, compared with the configuration without precompensation and using NLPC, the total optical power budget when using PD-NLPC is increased by 1.8dB and 0.8dB, respectively, at a transmission distance of 40km.

[0065] The experimental results are as follows Figure 6 shown. Figure 6 (a) shows the result of 256Gbps 16QAM signal transmission through 40km single-mode fiber with an input optical power of 12dBm. -2 The NLPC scheme achieves an ROP improvement of about 1 dB compared to the uncompensated scheme. In addition, the proposed PD-NLPC scheme can improve the ROP by about 1 dB more. Figure 6 (b) shows the experimental results when the optical power of the fiber is 13 dBm. Obviously, except for the curve using PD-NLPC, the other curves do not reach the bit error rate threshold of 1×10 -2 . Figure 6 (c) in Figure 1 shows the relationship between the power budget of a 256Gbps 16QAM signal and the input optical power. From the experimental results, it can be observed that when the input optical power is 10dBm, 11dBm and 12dBm, the non-precompensation scheme, NLPC scheme and PD-NLPC scheme can obtain the maximum power budget, which are 36.7dB, 37.2dB and 37.8dB respectively. The PD-NLPC scheme demonstrated in this patent can achieve a 1.1dB power budget improvement compared to the non-precompensation scheme; compared to the NLPC scheme, it can achieve a 0.6dB power budget improvement.

[0066] Embodiment 3

[0067] This embodiment provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method described in Embodiment 1 or Embodiment 2 when executing the computer program.

[0068] Embodiment 4

[0069] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described in Embodiment 1 or Embodiment 2 are implemented.

[0070] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for precompensating symbol-correlated nonlinear phase noise in an optical communication system, characterized in that: Follow these steps: S1. Generate a lookup table based on the transmitted symbol, whose table size is M 2L+1 , where M represents the modulation order; the length of the transmission symbol Y(kL:k:k+L) is 2L+1, representing a symbol combination in the table; after the lookup table is generated, the phase error in the table is initialized to 0; S2. After initializing the lookup table, the training sequence Y is converted into optical fiber and imported into the optical fiber for transmission. The receiving end uses digital signal processing to eliminate other channel damage and obtain the recovery sequence Y'; S3. Use the sliding window to select a length of 2L+1, calculate the combined position index in the lookup table, and calculate the corresponding phase noise e(k); S4. As the sliding window moves forward, more and more data are stored in the lookup table. The parameter N(i) is used to record the number of data stored in the lookup table index i. The final data in each lookup table index i is the average of all phase noises e(k). S5. Arrange the lookup table at the OLT transmitting end for pre-distortion of the transmitted data.

2. The method for pre-compensating symbol-correlated nonlinear phase noise in an optical communication system according to claim 1, characterized in that: In step S3, e(k) is obtained by calculating the phase difference between the symbol combination center symbol Y(k) and the corresponding restored symbol Y'(k):

3. The method for pre-compensating symbol-correlated nonlinear phase noise in an optical communication system according to claim 2, characterized in that: In step S4, the average of all phase noises e(k) is calculated by the following formula: LUT(i)=LUT(i)+e(k) N(i)=N(i)+1 LUT(i)_e(k)=LUT(i) / N(i) Where LUT(i)_e(k) is the final phase noise in each lookup table index i.

4. The method for pre-compensating symbol-correlated nonlinear phase noise in an optical communication system according to claim 3, characterized in that: In step S5, the pre-distortion process includes: X'(k)=X(k)×exp(j×LUT_e).

5. The method for pre-compensating symbol-correlated nonlinear phase noise in an optical communication system according to any one of claims 1 to 4, characterized in that: For a dual polarization system, firstly, each polarization state is independently operated using method steps S1 to S4 to compensate for the sign-correlated nonlinear phase noise in each polarization state; then, the noise pre-compensation method NLPC is used to compensate for the nonlinear phase noise introduced by the other polarization state.

6. The method for pre-compensating symbol-correlated nonlinear phase noise in an optical communication system according to claim 5, characterized in that: For a dual polarization system, the symbol combination in the X and Y polarization states is the same, and in the process of storing the symbols, a storage mechanism that complies with the combination sharing is adopted.

7. A method for compensating symbol-correlated nonlinear phase noise in an optical communication system, characterized in that: include: Transmitter digital signal processing DSP: First, bit-to-QAM mapping is performed to generate a 16QAM signal; Then, the noise pre-compensation method described in any one of claims 1 to 4 is applied to perform symbol-related nonlinear phase noise pre-compensation; the generated signal is then digitally up-sampled and pulse-shaped by a raised cosine filter; after pulse shaping, NLPC is applied to compensate for nonlinear phase noise introduced by other polarizations; and then, a 32Gbaud 16QAM signal is generated by an arbitrary waveform generator; Receiver digital signal processing DSP: First, the orthogonalization process and dispersion compensation are carried out; then, a raised cosine filter with the same roll-off factor as the DSP at the transmitting end is used for matched filtering; then, the cascaded multi-mode algorithm CMMA is used for signal equalization to reduce the influence of the system band limitation; then, the frequency offset estimation FOE and carrier phase estimation CPE are used for phase noise compensation; then, the multiple input multiple output algorithm MIMO is applied to solve the IQ imbalance problem at the transmitter end; Finally, the recovered signal is subjected to QAM demodulation and bit error rate calculation.

8. The method for compensating symbol-correlated nonlinear phase noise in an optical communication system according to claim 7, characterized in that: The roll-off factor used is 1 / 8. At the transmitting end DSP, a 32Gbaud 16QAM signal is generated by a 64GSa / s 8-bit arbitrary waveform generator AWG. At the receiving end DSP, a 25-tap cascaded multi-mode algorithm CMMA is used. A 3-tap 4x4 real multiple-input multiple-output algorithm MIMO is applied.

9. A computer device comprising a memory and a processor, characterized in that: The memory stores a computer program, and the processor implements the steps of the method described in any one of claims 1 to 8 when executing the computer program.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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