An adaptive nonlinear impairment compensation method based on low-cost optical performance monitoring

Abstract

The application discloses a kind of self-adapting nonlinear impairment compensation methods based on low-cost optical performance monitoring, and its technical scheme main points are as follows: in transmitting end, low-speed mark is modulated to the envelope of high-speed data signal on top signal;A section of zero-power gap is inserted into signal, after digital-analog conversion and electro-optical conversion are successively carried out to data, into optical fiber link;In receiving end, the signal received is successively carried out photoelectric conversion, analog-digital conversion, IQ orthogonalization, clock recovery;Combining the step number of FD-Volterra-CDE back propagation process in different optical transmission link state parameter range N span Nonlinear effect introduced by the calculation of nonlinear impairment causes optical signal-to-noise ratio penalty;The adaptive nonlinear impairment compensation method in the application solves the problem of too high calculation complexity in the traditional nonlinear impairment compensation process, and by establishing the LUT of the step number N step , filter number N k In the process of FD-Volterra-CDE back propagation in different optical transmission link state parameter range, the calculation complexity is effectively reduced while the compensation accuracy is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of optical fiber communication technology, and specifically to an adaptive nonlinear damage compensation method based on low-cost optical performance monitoring. Background Technology

[0002] To overcome the accumulated noise from multi-span amplification during long-distance transmission, high transmit power is required. However, high-power signals suffer severe Kerr nonlinear impairment after long-distance fiber optic transmission. Therefore, nonlinear impairment compensation of the received signal is crucial in long-distance fiber optic transmission scenarios.

[0003] Traditional nonlinear damage compensation techniques include the Digital Backpropagation (DBP) algorithm and the Volterra series equalization model, but they generally suffer from high computational complexity. To achieve high compensation accuracy, the DBP algorithm typically uses a very small step size, which means that a large number of time-frequency domain transformation operations are required during algorithm implementation, leading to high computational complexity. Similarly, the numerous nonlinear kernels in the Volterra series equalization model also contribute to its high computational complexity. In summary, the excessively high computational complexity of traditional nonlinear damage compensation algorithms limits their practical applications. To address these issues, we propose an adaptive nonlinear damage compensation method based on low-cost optical performance monitoring. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an adaptive nonlinear damage compensation method based on low-cost optical performance monitoring, thus solving the problems mentioned in the background technology.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0006] An adaptive nonlinear damage compensation method based on low-cost optical performance monitoring includes the following steps:

[0007] At the transmitting end, the low-speed marker modulation signal used for performance monitoring is modulated onto the envelope of the high-speed data signal;

[0008] A zero-power gap is inserted into the signal, and after the data undergoes digital-to-analog conversion and electro-optic conversion, it is transmitted to the fiber optic link.

[0009] At the receiving end, the received signal undergoes photoelectric conversion, analog-to-digital conversion, IQ orthogonalization, and clock recovery sequentially. Subsequently, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) during the transmission link process are monitored based on the marker-modulated signal. NLI );

[0010] Based on (OSNR) and (SNR) NLI) Calculate the optical signal-to-noise ratio penalty (OSNR) caused by nonlinear damage PENALTY_NLI );

[0011] Based on OSNR and OSNR PENALTY_NLI Optimize the backpropagation process of frequency domain Volterra-CDE (FD-Volterra-CDE);

[0012] After the received transmitted signal undergoes a reverse propagation process via FD-Volterra-CDE, channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate performance meets the standard.

[0013] Preferably, the expression for modulating the low-speed marker modulation signal used for performance monitoring onto the envelope of the high-speed data signal is:

[0014]

[0015] in, This represents the modulated power waveform. This represents the power waveform before modulation. The modulation index is used to adjust the top signal. The modulation frequency is used to adjust the top signal frequency.

[0016] Preferably, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) during the monitoring of the transmission link based on the marker-trimmed signal are... NLI The steps include:

[0017] The average power P of the marked modulation signal waveform at the receiving end is obtained by averaging through a sliding window method. PT ;

[0018] By marking the relationship between the modulation signal power and the data signal power, the effective transmitted data signal power P is obtained. sig ;

[0019] Based on the obtained effective transmitted data signal power P sig Calculate the total power P in the fiber optic link. tot This leads to the OSNR;

[0020] During transmission, the accumulation of nonlinear noise and ASE noise is calculated based on the dispersion effect, and the SNR is further calculated. NLI .

[0021] Preferably, the calculation of OSNR and SNR NLI The formula is:

[0022]

[0023]

[0024] Where P sig To effectively transmit data signal power, P tot For total power, This refers to the power at the original zero-power gap at the receiving end.

[0025] Preferably, the method based on OSNR and SNR NLI Calculate the optical signal-to-noise ratio (OSNR) penalty caused by nonlinear damage. PENALTY_NLI The steps are as follows:

[0026] The optical signal-to-noise ratio (OSNR) and the nonlinear signal-to-noise ratio (SNR) are calculated using the power information of the tagged modulated signal acquired at the receiver. NLI );

[0027] By comparing these two, the optical signal-to-noise ratio (OSNR) penalty caused by nonlinear effects can be calculated. PENALTY_NLI This penalty value is used to characterize the negative impact of nonlinear impairment on signal quality, and is then used to optimize the compensation algorithm. The formula is as follows:

[0028]

[0029] in, The measured optical signal-to-noise ratio, The signal-to-noise ratio is the noise generated due to nonlinear effects.

[0030] Preferably, the OSNR-based OSNR PENALTY_NLI The specific steps to optimize the FD-Volterra-CDE backpropagation process are as follows:

[0031] Establish OSNR, OSNR PENALTY_NLI The number of steps N in the backpropagation process of FD-Volterra-CDE step Number of filters N k Lookup table (LUT);

[0032] After the received transmitted signal undergoes the FD-Volterra-CDE backpropagation process, channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate (BER) is below a threshold. If it is below the threshold, the signal is output; if it is above the threshold, it is fed back to the FD-Volterra-CDE backpropagation module to readjust the OSNR. PENALTY_NLI With the number of steps N step Number of filters N k The LUT is then repeated until the bit error rate is below the threshold.

[0033] Preferably, the OSNR-based OSNR PENALTY_NLI The steps to optimize the FD-Volterra-CDE backpropagation process include:

[0034] Establish OSNR, OSNR PENALTY_NLI The number of steps N in the backpropagation process of FD-Volterra-CDE step Number of filters N k Lookup table (LUT).

[0035] Preferably, the specific steps of the FD-Volterra-CDE backpropagation process are as follows:

[0036] The input signal is transformed using Fast Fourier Transform (FFT). Convert to the frequency domain to obtain ;

[0037] Will With first-order inverse linear kernel Multiplication achieves CDE;

[0038] The input signal is subjected to an overlapping addition method, uniform sampling, and angular frequency. As shown in the following formula:

[0039]

[0040] in, Sampling rate, Defined as an angular frequency grid.

[0041] Preferably, after the optimized signal from the FD-Volterra-CDE backpropagation process is further processed through channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate is lower than a set threshold. If it is lower than the threshold, the signal is output; otherwise, the backpropagation process is adjusted and the OSNR and OSNR are recalculated. PENALTY_NLI Parameters such as these.

[0042] In summary, the present invention has the following main beneficial effects:

[0043] 1. This invention addresses the problem of excessive computational complexity in traditional nonlinear damage compensation methods by introducing a low-cost optical performance monitoring method, which significantly reduces the computational resources and hardware requirements required in the nonlinear damage compensation process. During transmission, this invention achieves dynamic monitoring of optical performance in a simple and effective way by modulating a low-speed marker modulation signal onto the envelope of a high-speed data signal, avoiding the use of complex and expensive monitoring hardware, while ensuring real-time perception of link state parameters, providing accurate data support for subsequent compensation optimization.

[0044] 2. This invention achieves low-cost optical performance monitoring while establishing the number of steps N in the back propagation process of FD-Volterra-CDE under different optical transmission link state parameter ranges. stepNumber of filters N k The LUT effectively reduces computational complexity while ensuring compensation accuracy. Attached Figure Description

[0045] Figure 1 A schematic diagram of an adaptive nonlinear damage compensation method based on low-cost optical performance monitoring provided in an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the power waveform of the marker modulation signal modulated on a high-speed data signal according to an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the power waveform of a high-speed data signal modulated by a zero-power marker modulation signal provided in an embodiment of the present invention;

[0048] Figure 4 This is a schematic diagram illustrating the compensation for signal impairment during the backpropagation process of FD-Volterra-CDE, provided in an embodiment of the present invention. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0051] Example 1

[0052] An adaptive nonlinear damage compensation method based on low-cost optical performance monitoring includes the following steps:

[0053] At the transmitting end, the low-speed marker modulation signal used for performance monitoring is modulated onto the envelope of the high-speed data signal;

[0054] A zero-power gap is inserted into the signal, and after the data undergoes digital-to-analog conversion and electro-optic conversion, it is transmitted to the fiber optic link.

[0055] At the receiving end, the received signal undergoes photoelectric conversion, analog-to-digital conversion, IQ orthogonalization, and clock recovery sequentially. Subsequently, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) during the transmission link process are monitored based on the marker-modulated signal. NLI );

[0056] Based on (OSNR) and (SNR) NLI ) Calculate the optical signal-to-noise ratio penalty (OSNR) caused by nonlinear damage PENALTY_NLI );

[0057] Based on OSNR and OSNR PENALTY_NLI Optimize the backpropagation process of frequency domain Volterra-CDE (FD-Volterra-CDE);

[0058] After the received transmitted signal undergoes a reverse propagation process via FD-Volterra-CDE, channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate performance meets the standard.

[0059] like Figure 1 As shown, the adaptive nonlinear damage compensation method based on low-cost optical performance monitoring includes three parts: the transmitter, the link side, and the receiver.

[0060] At the transmitting end, the low-speed marker modulation signal used for performance monitoring is modulated onto the envelope of the high-speed data signal, such as... Figure 2 and Figure 3 As shown;

[0061] A zero-power gap is inserted into the signal, and after the data undergoes digital-to-analog conversion and electro-optic conversion, it is transmitted to the fiber optic link.

[0062] At the receiving end, the received signal undergoes photoelectric conversion, analog-to-digital conversion, IQ orthogonalization, and clock recovery sequentially. Subsequently, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) during the transmission link process are monitored based on the marker-modulated signal. NLI );

[0063] Based on OSNR and SNR NLI Calculate the optical signal-to-noise ratio penalty (OSNR) caused by nonlinear damage. PENALTY_NLI );

[0064] Based on OSNR and OSNR PENALTY_NLI Optimize the FD-Volterra-CDE backpropagation process;

[0065] After the received transmitted signal undergoes a reverse propagation process via FD-Volterra-CDE, channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate performance meets the standard.

[0066] The expression for modulating the low-speed marker modulation signal used for performance monitoring onto the envelope of the high-speed data signal is as follows:

[0067]

[0068] in, This represents the modulated power waveform. This represents the power waveform before modulation. The modulation index is used to adjust the top signal. The modulation frequency is used to adjust the top signal frequency;

[0069] The OSNR and SNR during the monitoring of the transmission link based on the marker tuning signal NLI The specific steps are as follows:

[0070] The average power P of the marked modulation signal waveform at the receiving end is obtained by averaging through a sliding window method. PT Then, by marking the relationship between the modulation signal power and the data signal power, the effective transmitted data signal power P is obtained. sig The expression is:

[0071]

[0072] The sum of the data signal power and the amplifier spontaneous emission (ASE) noise power in the fiber optic link, P, is obtained based on the mean square method. tot This leads to the OSNR, expressed as:

[0073]

[0074] During transmission, due to the dispersion effect of the signal in the optical fiber, some power of the symbol near the zero-power gap at the transmitting end spills out to the original zero-power gap, causing nonlinear noise and ASE noise to accumulate at the gap, which can then be used to calculate the SNR. NLI The expression is:

[0075]

[0076] Among them, P NLI This refers to the power at the original zero-power gap at the receiving end;

[0077] The basis of OSNR and SNR NLI Calculate the optical signal-to-noise ratio (OSNR) penalty caused by nonlinear damage. PENALTY_NLI Specifically:

[0078]

[0079] The OSNR-based and OSNR PENALTY_NLIThe specific steps to optimize the FD-Volterra-CDE backpropagation process are as follows:

[0080] Establish OSNR, OSNR PENALTY_NLI The number of steps N in the backpropagation process of FD-Volterra-CDE step Number of filters N k Lookup table (LUT);

[0081] The FD-Volterra-CDE backpropagation process is as follows:

[0082] Assuming the transmission system is a dual-polarization system, and analyzing the X / Y polarization signal, without loss of generality, for the dispersion equalization (CDE) part, the input signal is transformed using Fast Fourier Transform (FFT). Convert to the frequency domain to obtain By With first-order inverse linear kernel Multiplication achieves CDE, where, Angular frequency, The transmission distance within a single step. For a single span of fiber optic cable, The fiber attenuation coefficient, denoted as the fiber group velocity dispersion coefficient.

[0083] Example 2

[0084] For the FD-VSNE part, the input samples are processed in blocks, and the input signal... The sample is divided into N sample blocks, converted to the frequency domain by FFT, and uniformly sampled using an overlapping addition method. The angular frequency is... As shown in the following formula:

[0085]

[0086] in, Sampling rate, Defined as an angular frequency grid;

[0087] Will After performing FFT,

[0088]

[0089] in, This represents the nth discrete angular frequency of the signal; It is a one-dimensional frequency-dependent nonlinear term, where These are the optimization parameters for controlling nonlinear compensation. These are nonlinear coefficients; For the inverse third-order nonlinear kernel, and for the three-dimensional frequency correlation term, as shown in the following equation:

[0090]

[0091] in, ;

[0092] The polarization crosstalk is characterized by the following equation:

[0093]

[0094] in, ;

[0095] Generally, the following substitutions can be performed:

[0096]

[0097] Substituting equation (10) into equation (7), we obtain the nonlinear equilibrium optical field for compensating for nonlinear impairments within the channel:

[0098]

[0099] in, , ,in, It is the first in the signal Index of frequency components It is the index of the symmetric Volterra series nonlinear equalization (symVSNE) filter. The maximum value is , .

[0100] like Figure 3 As shown, the FFT-processed signal is simultaneously input into the CDE and symVSNE modules for parallel processing. In the symVSNE module, the complex calculations of the Volterra series kernel are simplified into the parallel processing of a series of one-dimensional filters, where the number of filters is N. k The results from the CDE module and the symVSNE module are summed, and the iteration continues for N iterations. step ;

[0101] After iteration, the signal continues to pass through channel equalization, frequency offset estimation, and phase recovery. It is then determined whether the bit error rate (BER) is below a threshold. If it is below the threshold, the signal is output; if it is above the threshold, it is fed back to the FD-Volterra-CDE backpropagation module to readjust the OSNR. PENALTY_NLI With the number of steps N step Number of filters N k The LUT is then repeated until the bit error rate is below the threshold.

[0102] Working principle: Please refer to Figures 1-4 As shown, the present invention addresses the common problem of high computational complexity in traditional nonlinear damage compensation techniques such as the DBP algorithm and Volterra series equalization model. To achieve high compensation accuracy, the DBP algorithm typically uses a very small step size, which means that a large number of time-frequency domain transformation operations are required during algorithm implementation, resulting in high computational complexity. Similarly, the Volterra series equalization model suffers from high computational complexity due to its numerous nonlinear kernels. The adaptive nonlinear damage compensation method in this invention solves the problem of high computational complexity in traditional nonlinear damage compensation processes. While achieving optical performance monitoring at low cost, it establishes the number of steps N in the FD-Volterra-CDE backpropagation process under different optical transmission link state parameter ranges. step Number of filters N k The LUT effectively reduces computational complexity while ensuring compensation accuracy. The FD-Volterra-CDE backpropagation process based on low-cost optical performance monitoring provided in the embodiment can effectively reduce the complexity of the nonlinear damage compensation process while ensuring signal transmission quality.

[0103] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that, unless otherwise defined, the technical or scientific terms used in this invention should be understood in the ordinary sense by those skilled in the art to which this invention pertains, and the terms "comprising" or "including" or similar terms used in this invention mean that the element or object preceding the word covers the element or object listed after the word and its equivalents.

[0104] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An adaptive nonlinear damage compensation method based on low-cost optical performance monitoring, characterized in that, Includes the following steps: At the transmitting end, the low-speed marker modulation signal used for performance monitoring is modulated onto the envelope of the high-speed data signal; A zero-power gap is inserted into the signal. After the data undergoes digital-to-analog conversion and electro-optical conversion, it is transmitted to the fiber optic link. The fiber optic link contains N... span Each fiber optic amplification segment is used to compensate for optical signal loss during transmission. At the receiving end, the received signal undergoes photoelectric conversion, analog-to-digital conversion, IQ orthogonalization, and clock recovery. Subsequently, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) during the transmission link process are monitored based on the marker-modulated signal. NLI ; Combined with N in the link span The introduced nonlinear effects are based on OSNR and SNR NLI Calculate the optical signal-to-noise ratio (OSNR) penalty caused by nonlinear damage. PENALTY_NLI ; Based on OSNR and OSNR PENALTY_NLI Optimize the backpropagation process of frequency domain Volterra-dispersion equalization (FD-Volterra-CDE); After the received transmitted signal undergoes a reverse propagation process via FD-Volterra-CDE, channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate performance meets the standard.

2. The adaptive nonlinear damage compensation method based on low-cost optical performance monitoring according to claim 1, characterized in that, The expression for modulating the low-speed marker modulation signal used for performance monitoring onto the envelope of the high-speed data signal is as follows: in, This represents the modulated power waveform. This represents the power waveform before modulation. The modulation index is used to adjust the top signal. The modulation frequency is used to adjust the top signal.

3. The adaptive nonlinear damage compensation method based on low-cost optical performance monitoring according to claim 1, characterized in that, The optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) in the transmission link monitoring process based on the marker-trimmed signal are described. NLI The steps include: The average power P of the marked modulation signal waveform at the receiving end is obtained by averaging through a sliding window method. PT ; By marking the relationship between the modulation signal power and the data signal power, the effective transmitted data signal power P is obtained. sig ; Based on the obtained effective transmitted data signal power P sig Calculate the total power P in the fiber optic link. tot This leads to the OSNR; During transmission, the accumulation of nonlinear noise and ASE noise is calculated based on the dispersion effect, and the SNR is further calculated. NLI .

4. The adaptive nonlinear damage compensation method based on low-cost optical performance monitoring according to claim 3, characterized in that, The calculation of OSNR and SNR NLI The formula is: Where P sig To effectively transmit data signal power, P tot For total power, This refers to the power at the original zero-power gap at the receiving end.

5. The adaptive nonlinear damage compensation method based on low-cost optical performance monitoring according to claim 1, characterized in that, The basis of OSNR and SNR NLI Calculate the optical signal-to-noise ratio (OSNR) penalty caused by nonlinear damage. PENALTY_NLI The steps are as follows: The optical signal-to-noise ratio (OSNR) and the nonlinear signal-to-noise ratio (SNR) are calculated using the power information of the tagged modulated signal acquired at the receiver. NLI ; By comparing these two, the optical signal-to-noise ratio (OSNR) penalty caused by nonlinear effects can be calculated. PENALTY_NLI This penalty value is used to characterize the negative impact of nonlinear impairment on signal quality, and is then used to optimize the compensation algorithm. The formula is as follows: in, For the measured optical signal-to-noise ratio, The signal-to-noise ratio is the noise generated due to nonlinear effects.

6. The adaptive nonlinear damage compensation method based on low-cost optical performance monitoring according to claim 1, characterized in that, The OSNR-based and OSNR PENALTY_NLI The specific steps to optimize the FD-Volterra-CDE backpropagation process are as follows: Establish OSNR, OSNR PENALTY_NLI The number of steps N in the backpropagation process of FD-Volterra-CDE step Number of filters N k LUT lookup table; After the received transmitted signal undergoes the FD-Volterra-CDE backpropagation process, channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate (BER) is below a threshold. If it is below the threshold, the signal is output; if it is above the threshold, it is fed back to the FD-Volterra-CDE backpropagation module to readjust the OSNR. PENALTY_NLI With the number of steps N step Number of filters N k The LUT is then repeated until the bit error rate is below the threshold.

7. The adaptive nonlinear damage compensation method based on low-cost optical performance monitoring according to claim 1, characterized in that, The OSNR-based and OSNR PENALTY_NLI The steps to optimize the FD-Volterra-CDE backpropagation process include: Establish OSNR, OSNR PENALTY_NLI The number of steps N in the backpropagation process of FD-Volterra-CDE step Number of filters N k The lookup table LUT.

8. The adaptive nonlinear damage compensation method based on low-cost optical performance monitoring according to claim 1, characterized in that, The specific steps of the FD-Volterra-CDE backpropagation process are as follows: The input signal is processed using Fast Fourier Transform (FFT). Convert to the frequency domain to obtain ; Will With first-order inverse linear kernel Multiplication achieves CDE, where, The fiber attenuation coefficient, The group velocity dispersion coefficient of the optical fiber. The length of a single fiber optic cable. Angular frequency, This refers to the single-step propagation distance during the reverse propagation process; The input signal is subjected to an overlapping addition method, uniform sampling, and angular frequency. As shown in the following formula: in, For frequency index, The number of sampling points. Sampling rate, It is an angular frequency grid.

9. The adaptive nonlinear damage compensation method based on low-cost optical performance monitoring according to claim 1, characterized in that, After the optimized signal from the FD-Volterra-CDE backpropagation process is further processed through channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate is lower than the set threshold. If it is lower than the threshold, the signal is output; otherwise, the backpropagation process is adjusted and the parameters are recalculated.

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