Self-adaptive nonlinear damage compensation method based on low-cost optical performance monitoring

Abstract

The invention discloses a self-adaptive nonlinear damage compensation method based on low-cost optical performance monitoring, and the method is characterized in that the method comprises the following steps: modulating a low-speed mark top-adjusting signal to a high-speed data signal envelope at a transmitting end; inserting a section of zero-power gap into a signal, sequentially performing digital-to-analog conversion and electro-optical conversion on data, and transmitting the data into an optical fiber link; at a receiving end, photoelectric conversion, analog-to-digital conversion, IQ orthogonalization and clock recovery are carried out on the received signal in sequence; calculating optical signal-to-noise ratio penalty caused by non-linear damage by combining a non-linear effect introduced by Nspan in a link; according to the self-adaptive nonlinear damage compensation method, the problem that the calculation complexity of a traditional nonlinear damage compensation process is too high is solved, meanwhile, the LUT with the step number Nstep and the filter number Nk in the FD-Volterra-CDE back propagation process under different optical transmission link state parameter ranges is established, the compensation precision is guaranteed, and meanwhile the calculation complexity is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber communication, and in particular to an adaptive nonlinear damage compensation method based on low-cost optical performance monitoring. Background Art

[0002] In order to overcome the accumulated noise of multi-span amplification during long-distance transmission, a higher transmission power is required. However, high-power signals will suffer serious Kerr nonlinear damage after long-distance optical fiber transmission. Therefore, in the long-distance optical fiber transmission scenario, it is very important to compensate for the nonlinear damage of the received signal.

[0003] Traditional nonlinear damage compensation techniques include digital back propagation (DBP) algorithm, Volterra series equalization model, etc., but the common problem is that the computational complexity is too high. In order to seek high compensation accuracy, the step size of the DBP algorithm is usually very small, which means that a large number of time-frequency domain conversion operations are required during the algorithm implementation, resulting in high computational complexity; for the Volterra series equalization model, a large number of nonlinear kernels also lead to high computational complexity. In general, the high computational complexity of traditional nonlinear damage compensation algorithms limits their practical applications. To solve the above problems, we propose an adaptive nonlinear damage compensation method based on low-cost optical performance monitoring. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides an adaptive nonlinear damage compensation method based on low-cost optical performance monitoring to solve the problems raised in the background technology.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

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

[0007] At the transmitting end, a low-speed mark-to-top signal for performance monitoring is modulated onto the high-speed data signal envelope;

[0008] A zero-power gap is inserted into the signal, and after the data is converted from digital to analog and from electro-optical to optical, it is transmitted to the optical fiber link. The optical fiber link contains N span A fiber amplifier section, each of which is used to compensate for the loss of optical signals during transmission;

[0009] At the receiving end, the received signal is subjected to optical-to-electrical conversion, analog-to-digital conversion, IQ orthogonalization, and clock recovery. Then, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) of the transmission link are monitored based on the marker modulation signal. NLI );

[0010] Combined with link N span The nonlinear effect introduced is based on OSNR and SNR NLI Calculate the optical signal-to-noise ratio penalty (OSNR) caused by nonlinear impairments PENALTY_NLI );

[0011] Based on OSNR and OSNR PENALTY_NLI , optimize the frequency-domain Volterra-dispersion equalization (FD-Volterra-CDE) back-propagation process;

[0012] The received transmission signal is further passed through the FD-Volterra-CDE reverse propagation process, channel equalization, frequency offset estimation, and phase recovery to determine whether the bit error performance meets the standard.

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

[0014]

[0015] in, represents the modulated power waveform, represents the power waveform before modulation, is the modulation index of the top modulation signal, The modulation frequency of the top modulation signal.

[0016] Preferably, the optical signal-to-noise ratio OSNR and the nonlinear signal-to-noise ratio SNR in the transmission link process are monitored based on the marker top modulation signal. NLI The steps include:

[0017] The power waveform of the receiving end mark modulation signal is obtained by averaging the sliding window, and its average power P is calculated. PT ;

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

[0019] Based on the obtained effective transmission data signal power P sig , calculate the total power P in the optical fiber link tot , and then get OSNR;

[0020] During the transmission process, 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 is the total power, is the power at the original zero power gap at the receiving end.

[0025] Preferably, the OSNR and SNR NLI Calculate the optical signal-to-noise ratio penalty OSNR caused by nonlinear damage PENALTY_NLI The steps are:

[0026] The optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) are calculated by obtaining the power information of the top-modulated signal at the receiving end. NLI );

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

[0028]

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

[0030] Preferably, the OSNR and OSNR PENALTY_NLI The specific steps to optimize the FD-Volterra-CDE back-propagation process are:

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

[0032] After the received transmission signal passes through the FD-Volterra-CDE back propagation process, channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate is lower than the threshold. If it is lower than the threshold, the signal is output. If it is higher than the threshold, it is fed back to the FD-Volterra-CDE back propagation module to readjust the OSNR and OSNR PENALTY_NLI With the number of steps N step 、Number of filters k The LUT is then repeated until the bit error rate falls below the threshold.

[0033] Preferably, the OSNR and OSNR PENALTY_NLI The steps to optimize the FD-Volterra-CDE back-propagation process include:

[0034] Establish OSNR, OSNR PENALTY_NLI The number of steps N during the backpropagation process with FD-Volterra-CDE step 、Number of filters k A look-up table (LUT) is provided.

[0035] Preferably, the specific steps of the FD-Volterra-CDE back propagation process are:

[0036] The input signal is transformed by fast Fourier transform (FFT) Converted to frequency domain, we get ;

[0037] Will With the first-order inverse linear kernel Multiply to achieve CDE;

[0038] Overlap and add the input signal, uniform sampling, angular frequency As shown below:

[0039]

[0040] in, is the sampling rate, Defined as an angular frequency grid.

[0041] Preferably, the signal optimized by the FD-Volterra-CDE back propagation process continues to pass through channel equalization, frequency offset estimation, and phase recovery to determine whether the bit error rate is lower than a set threshold. If it is lower than the threshold, the signal is output; otherwise, feedback is used to adjust the back propagation process and recalculate OSNR and OSNR. PENALTY_NLI And other parameters.

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

[0043] 1. The present invention aims at solving the problem of high computational complexity of traditional nonlinear damage compensation methods. By introducing low-cost optical performance monitoring means, the computing resources and hardware requirements required in the nonlinear damage compensation process are significantly reduced. During the transmission process, the present invention modulates the low-speed mark-to-top signal onto the high-speed data signal envelope to achieve dynamic monitoring of optical performance in a simple and effective manner, avoiding the use of complex and expensive monitoring hardware, while ensuring real-time perception of link status parameters, providing accurate data support for subsequent compensation optimization.

[0044] 2. The present invention realizes optical performance monitoring at low cost, and at the same time, establishes the number of steps N in the reverse propagation process of FD-Volterra-CDE under different optical transmission link state parameter ranges. step 、Number of filters k The LUT effectively reduces the calculation complexity while ensuring the compensation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0046] Figure 2 A schematic diagram of a power waveform of a high-speed data signal modulated by a mark top modulation signal provided in an embodiment of the present invention;

[0047] Figure 3 A schematic diagram of a power waveform of a high-speed data signal modulated by a zero-power mark-top signal provided by an embodiment of the present invention;

[0048] Figure 4 A schematic diagram of compensating for signal damage during the FD-Volterra-CDE back-propagation process provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0050] The following examples are used to illustrate the present invention, but they cannot be used to limit the scope of protection of the present invention. The conditions in the examples can be further adjusted according to specific conditions. Simple improvements to the method of the present invention under the premise of the concept of the present invention belong to the scope of protection claimed in 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, a low-speed mark-to-top signal for performance monitoring is modulated onto the high-speed data signal envelope;

[0054] A zero-power gap is inserted into the signal, and after the data is converted from digital to analog and from electro-optical to optical, it is transmitted to the optical fiber link. The optical fiber link contains N spanA fiber amplifier section, each of which is used to compensate for the loss of optical signals during transmission;

[0055] At the receiving end, the received signal is subjected to optical-to-electrical conversion, analog-to-digital conversion, IQ orthogonalization, and clock recovery. Then, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) of the transmission link are monitored based on the marker modulation signal. NLI );

[0056] Combined with link N span The nonlinear effect introduced is based on OSNR and SNR NLI Calculate the optical signal-to-noise ratio penalty (OSNR) caused by nonlinear impairments PENALTY_NLI );

[0057] Based on OSNR and OSNR PENALTY_NLI , optimize the frequency-domain Volterra-dispersion equalization (FD-Volterra-CDE) back-propagation process;

[0058] The received transmission signal is further passed through the FD-Volterra-CDE reverse propagation process, channel equalization, frequency offset estimation, and phase recovery to determine whether the bit error 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: a transmitter, a link side, and a receiver;

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

[0061] A zero-power gap is inserted into the signal, and after the data is converted from digital to analog and from electrical to optical, it is transmitted to the optical fiber link.

[0062] At the receiving end, the received signal is subjected to optical-to-electrical conversion, analog-to-digital conversion, IQ orthogonalization, and clock recovery. Then, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) of the transmission link are monitored based on the marker modulation signal. NLI );

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

[0064] Based on OSNR and OSNR PENALTY_NLI , optimize the FD-Volterra-CDE back-propagation process;

[0065] The received transmission signal is further passed through the FD-Volterra-CDE reverse propagation process, channel equalization, frequency offset estimation, and phase recovery to determine whether the bit error performance meets the standard.

[0066] The expression for modulating the low-speed mark modulation signal for performance monitoring onto the high-speed data signal envelope is:

[0067]

[0068] in, represents the modulated power waveform, represents the power waveform before modulation, is the modulation index of the top modulation signal, The modulation frequency of the top modulation signal is;

[0069] The OSNR and SNR in the process of monitoring the transmission link based on the marker top signal NLI The specific steps are:

[0070] The power waveform of the receiving end mark modulation signal is obtained by averaging the sliding window, and its average power P is calculated. PT Then, by marking the relationship between the top modulation signal power and the data signal power, the effective transmission data signal power P is obtained. sig , the expression is:

[0071]

[0072] Based on the average method, the sum of the data signal power and the amplifier spontaneous emission (ASE) noise power in the optical fiber link is obtained. tot , and then get OSNR, the expression is:

[0073]

[0074] During the transmission process, due to the dispersion effect of the signal in the optical fiber, the symbol near the zero power gap at the transmitting end will partially overflow to the original zero power gap, causing nonlinear noise and ASE noise to accumulate at the gap, and then the SNR can be calculated. NLI , the expression is:

[0075]

[0076] Among them, P NLI is the power at the original zero power gap at the receiving end;

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

[0078]

[0079] The OSNR and OSNR PENALTY_NLI The specific steps to optimize the FD-Volterra-CDE back-propagation process are:

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

[0081] The FD-Volterra-CDE back propagation process is specifically as follows:

[0082] Assuming that the transmission system is a dual-polarization system, we take the X / Y polarization signal for analysis. Without loss of generality, for the chromatic dispersion equalization (CDE) part, we transform the input signal into Converted to frequency domain, we get , by With the first-order inverse linear kernel Multiply them together to achieve CDE, where is the angular frequency, is the transmission distance within a single step, is the length of a single span fiber, is the optical fiber attenuation coefficient, is the fiber group velocity dispersion coefficient.

[0083] Example 2

[0084] For the FD-VSNE part, the input samples are processed in blocks. is divided into N blocks of samples, which are converted to the frequency domain by FFT, using the overlap-add method, uniform sampling, and the angular frequency As shown below:

[0085]

[0086] in, is the sampling rate, Defined as an angular frequency grid;

[0087] Will After performing FFT,

[0088]

[0089] in, Represents the nth discrete angular frequency of the signal; is a one-dimensional frequency-dependent nonlinear term, where is the optimization parameter controlling the nonlinear compensation, is the nonlinear coefficient; is the inverse third-order nonlinear kernel, and is the three-dimensional frequency-related term, as shown in the following formula:

[0090]

[0091] in, ;

[0092] Characterize the inter-polarization crosstalk as shown in the following equation:

[0093]

[0094] in, ;

[0095] Generally speaking, the following substitutions can be made:

[0096]

[0097] Substituting formula (10) into formula (7), we can obtain the nonlinear balanced optical field for compensating the nonlinear damage in the channel:

[0098]

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

[0100] like Figure 3 As shown in Figure 1, the FFT signal is simultaneously input into the CDE and symVSNE modules for parallel processing. In the symVSNE module, the complex calculation of the Volterra series kernel is simplified to the parallel processing of a series of one-dimensional filters, where the number of filters is N. k After accumulating the results of the CDE module and the symVSNE module, continue to iterate, the number of iterations is N step ;

[0101] After the iteration is completed, the signal continues to pass through channel equalization, frequency offset estimation, and phase recovery to determine whether the bit error rate is lower than the threshold. If it is lower than the threshold, the signal is output. If it is higher than the threshold, it is fed back to the FD-Volterra-CDE back propagation module to readjust the OSNR and OSNR. PENALTY_NLI With the number of steps Nstep 、Number of filters k The LUT is then repeated until the bit error rate falls below the threshold.

[0102] Working principle: Please refer to Figure 1-Figure 4 As shown, the common problem of the present invention compared with traditional nonlinear damage compensation technologies such as the DBP algorithm and the Volterra series equalization model is that the computational complexity is too high. In order to seek high compensation accuracy, the step size of the DBP algorithm is usually very small, which means that a large number of time-frequency domain conversion operations are required during the algorithm implementation, resulting in a high computational complexity; for the Volterra series equalization model, a large number of nonlinear kernels also lead to its high computational complexity. The adaptive nonlinear damage compensation method in the present invention solves the problem of high computational complexity in the traditional nonlinear damage compensation process. While realizing optical performance monitoring at a low cost, it establishes the number of steps N in the FD-Volterra-CDE reverse propagation process under different optical transmission link state parameter ranges. step 、Number of filters k The LUT can effectively reduce the computational complexity while ensuring the compensation accuracy. The FD-Volterra-CDE back propagation 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 the signal transmission quality.

[0103] Although the embodiments of the present invention have been shown and described, it is understood by those skilled in the art that, unless otherwise defined, the technical terms or scientific terms used in the present invention should have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs, and the words "include" or "comprise" and the like used in the present invention mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents.

[0104] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention 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: The following steps are involved: At the transmitting end, a low-speed mark-to-top signal for performance monitoring is modulated onto the high-speed data signal envelope; A zero-power gap is inserted into the signal, and after the data is converted from digital to analog and from electro-optical to optical, it is transmitted to the optical fiber link. The optical fiber link contains N span A fiber amplifier section, each of which is used to compensate for the loss of optical signals during transmission; At the receiving end, the received signal is subjected to optical-to-electrical conversion, analog-to-digital conversion, IQ orthogonalization, and clock recovery. Then, the optical signal-to-noise ratio (OSNR) and nonlinear signal-to-noise ratio (SNR) in the transmission link are monitored based on the marker modulation signal. NLI ; Combined with the link N span The nonlinear effect introduced is based on OSNR and SNR NLI Calculate the optical signal-to-noise ratio penalty OSNR caused by nonlinear damage PENALTY_NLI ; Based on OSNR and OSNR PENALTY_NLI , optimize the frequency domain Volterra-dispersion equalization FD-Volterra-CDE back propagation process; The received transmission signal is further passed through the FD-Volterra-CDE reverse propagation process, channel equalization, frequency offset estimation, and phase recovery to determine whether the bit error performance meets the standard.

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

3. The method for adaptive nonlinear damage compensation based on low-cost optical performance monitoring according to claim 1, characterized in that: The optical signal-to-noise ratio OSNR and the nonlinear signal-to-noise ratio SNR in the transmission link process are monitored based on the marker top modulation signal. NLI The steps include: The power waveform of the receiving end mark modulation signal is obtained by averaging the sliding window, and its average power P is calculated. PT ; By marking the relationship between the top modulation signal power and the data signal power, the effective transmission data signal power P is obtained. sig ; Based on the obtained effective transmission data signal power P sig , calculate the total power P in the optical fiber link tot , and then get OSNR; During the transmission process, the accumulation of nonlinear noise and ASE noise is calculated based on the dispersion effect, and the SNR is further calculated. NLI .

4. The method for adaptive nonlinear damage compensation 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 is the total power, is the power at the original zero power gap at the receiving end.

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

6. The method for adaptive nonlinear damage compensation based on low-cost optical performance monitoring according to claim 1, characterized in that: The OSNR and OSNR PENALTY_NLI The specific steps to optimize the FD-Volterra-CDE back-propagation process are: Establish OSNR, OSNR PENALTY_NLI The number of steps N during the backpropagation process with FD-Volterra-CDE step 、Number of filters k Lookup table LUT; After the received transmission signal passes through the FD-Volterra-CDE back propagation process, channel equalization, frequency offset estimation, and phase recovery, it is determined whether the bit error rate is lower than the threshold. If it is lower than the threshold, the signal is output. If it is higher than the threshold, it is fed back to the FD-Volterra-CDE back propagation module to readjust the OSNR and OSNR PENALTY_NLI With the number of steps N step 、Number of filters k The LUT is then repeated until the bit error rate falls below the threshold.

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

8. The method for adaptive nonlinear damage compensation based on low-cost optical performance monitoring according to claim 1, characterized in that: The specific steps of the FD-Volterra-CDE back propagation process are: The input signal is transformed by fast Fourier transform (FFT). Converted to frequency domain, we get ; Will With the first-order inverse linear kernel Multiply to achieve CDE; Overlap and add the input signal, uniform sampling, angular frequency As shown below: in, is the sampling rate, Defined as an angular frequency grid.

9. The method for adaptive nonlinear damage compensation based on low-cost optical performance monitoring according to claim 1, characterized in that: The nonlinear equalization process in the FD-Volterra-CDE back propagation process is calculated by the following formula: in, is the number of filters, is the frequency-dependent nonlinear term.

10. The method for adaptive nonlinear damage compensation based on low-cost optical performance monitoring according to claim 1, characterized in that: The signal optimized by the FD-Volterra-CDE back propagation process continues to pass through channel equalization, frequency offset estimation, and phase recovery to determine whether the bit error rate is lower than a set threshold. If it is lower than the threshold, the signal is output; otherwise, feedback is used to adjust the back propagation process and recalculate the parameters.

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