Coherent optical communication timing error estimation method, system and device and storage medium

Abstract

The invention discloses a coherent light communication timing error estimation method, system and device and a storage medium, and the method comprises the steps: obtaining a first discrete digital signal and a second discrete digital signal which are subjected to cross polarization, carrying out the matched filtering and resampling of the first discrete digital signal and the second discrete digital signal, and obtaining a first signal frequency spectrum and a second signal frequency spectrum; performing dispersion scanning on the first signal spectrum and the second signal spectrum, estimating a channel dispersion parameter according to the maximum clock, and performing dispersion effect compensation on the first signal spectrum and the second signal spectrum according to the channel dispersion parameter to obtain a first polarization signal and a second polarization signal; and calculating a target CAF matrix of high-order cyclic statistics according to the first polarization signal and the second polarization signal, and determining timing error information according to the target CAF matrix. According to the method, the complexity of coherent optical communication timing error estimation is reduced, the robustness of an optical communication system and the adaptability to different channel conditions are improved, and the method can be applied to the technical field of optical communication.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a method, system, device and storage medium for estimating timing errors in coherent optical communications. Background Art

[0002] With the explosive growth of the demand for the Internet and data communications, optical communication systems have become the backbone of modern communication networks due to their advantages such as high bandwidth, low loss and resistance to electromagnetic interference. Especially in high-speed coherent optical communication systems, ultra-high-speed data transmission can be achieved by using advanced modulation formats and digital signal processing technologies. Coherent detection technology in coherent optical communication systems can provide higher signal detection sensitivity and can accurately measure the amplitude and phase of optical signals, which is crucial for achieving high-speed transmission and improving signal quality. DSP technology plays a core role in coherent optical communication systems. It can perform necessary processing on the received optical signals, including symbol rate estimation, carrier frequency offset correction, dispersion compensation and adaptive equalization of signals.

[0003] In optical communication systems, timing error estimation is critical for accurate signal demodulation and system performance. However, due to non-ideal factors such as chromatic dispersion (CD), polarization mode dispersion (PMD), and random rotation of polarization (RSOP) in optical fiber channels, traditional timing error estimation algorithms are limited in performance when facing these complex channel effects, which have a significant impact on the performance of timing error estimation algorithms. These effects will cause the spectral correlation of the signal to decrease, thus affecting the accurate estimation of timing error. In order to achieve high performance in actually deployed optical communication systems, timing error estimation algorithms need to be highly robust and able to adapt to various channel conditions and non-ideal factors.

[0004] In high-speed coherent optical communication systems, accurate clock recovery is crucial to ensure the reliability of data transmission. In the prior art, Lee-power Timing Phase Error Detector (TPED), square-Gardner and 4PPD algorithms are several widely studied clock recovery methods. These algorithms process the power of the input sample sequence and use additional square operations to enhance the clock component, thereby improving the system's tolerance to low roll-off factors (ROF). Specifically, the Lee-power TPED algorithm proposes a low-complexity clock recovery method for non-integer oversampled Nyquist signals, which is particularly suitable for signals with small roll-off factors. The square-Gardner algorithm is a digital clock recovery algorithm designed specifically for Nyquist signals. The 4PPD algorithm achieves clock recovery by looking for specific peaks in the power spectrum of the signal.

[0005] However, these algorithms have limitations in terms of dispersion tolerance. Before performing clock error detection (TED), it is usually necessary to rely on static electronic dispersion compensation (EDC) or polarization mode dispersion (PMD) compensators to reduce the impact of channel impairments on TED performance. This means that in systems with large dispersion, these algorithms may not be directly applied and channel impairment preprocessing is required first.

[0006] Another class of methods is joint algorithms for Nyquist systems, which add an adaptive equalization and polarization demultiplexing (AEPD) module before clock recovery. These algorithms can effectively compensate for the differential group delay (DGD) and inter-symbol interference (ISI) in the channel, thereby improving the overall performance of the system. However, these algorithms usually rely on training sequences or pilot symbols, and the TED algorithm itself is not robust enough to resist DGD damage. For example, the robust clock recovery algorithm for digital multi-band systems based on OQAM performs well in multi-band systems, but may need further improvement in single-band systems.

[0007] In summary, although the existing coherent optical communication timing error estimation methods have made some progress in processing low roll-off factor signals and resisting channel damage, they cannot effectively tolerate dispersion and polarization rotation effects, and there is still room for improvement in robustness, adaptability and algorithm complexity.

[0008] Terminology explanation:

[0009] Coherent Optical Communication: Coherent optical communication is an advanced optical communication technology that uses lasers as light sources and uses coherent detection technology to improve signal reception sensitivity and transmission quality. In a coherent optical communication system, the signal at the transmitter modulates the optical carrier of the laser, while the receiver uses a local laser synchronized with the transmitter for coherent mixing to detect the amplitude and phase information of the transmitted signal. This technology significantly improves the signal transmission distance and system capacity.

[0010] Chromatic Dispersion (CD): Chromatic Dispersion refers to the phenomenon that the optical signal transmitted in the optical fiber is pulse-broadened due to the different light speeds of different wavelengths. Dispersion will distort the time domain waveform of the signal, affect the integrity of the signal, and thus reduce the performance of the communication system. The dispersion effect includes material dispersion and waveguide dispersion, and is one of the damage factors that need to be considered and compensated in long-distance optical fiber communication systems.

[0011] Nyquist System: Nyquist system refers to a signal sampling system that satisfies the Nyquist sampling theorem. According to the Nyquist sampling theorem, in order to avoid aliasing, the sampling frequency of the signal should be at least twice the highest frequency of the signal. In optical fiber communications, Nyquist systems usually refer to digital signal processing systems that can meet this condition and can accurately reconstruct the original analog signal from the sampled data.

[0012] Timing Error Estimation: Timing error estimation refers to the process of estimating the deviation between the sampling clock of the received signal and the actual clock of the signal in a digital communication system. Accurate timing error estimation is crucial for synchronous demodulation of the signal. It can ensure that the signal is sampled at the optimal time, thereby improving the accuracy of signal demodulation and the overall performance of the system.

[0013] DSP technology (Digital Signal Processing Technology): DSP technology refers to the technology of using digital circuits or computers to process signals. In optical fiber communication systems, DSP technology is widely used in key links such as signal modulation, demodulation, equalization, dispersion compensation, and timing recovery. Through DSP technology, efficient signal processing can be achieved, system performance can be optimized, and transmission quality can be improved.

[0014] Roll-off Factor (ROF): The roll-off factor is a parameter that describes the rate at which the signal spectrum decays. It is used to filter the signal in a digital communication system to limit its bandwidth. A signal with a smaller roll-off factor has a slower decay edge, which means that the signal occupies a wider spectrum; while a signal with a larger roll-off factor has a faster decay edge and a narrower spectrum. The choice of roll-off factor affects the transmission efficiency and anti-interference ability of the system.

[0015] Polarization Division Multiplexing (PDM): Polarization multiplexing is a technology that improves the capacity of optical fiber communication systems. It uses the polarization characteristics of optical signals to achieve double the data transmission rate by simultaneously transmitting two orthogonal polarization state signals in the same optical fiber. Each polarization state can carry information independently, which is equivalent to two independent communication channels. Polarization multiplexing technology can be combined with other multiplexing technologies (such as wavelength division multiplexing WDM) to further improve the system's spectrum efficiency and transmission capacity.

[0016] Polarization rotation (RSOP): Polarization rotation describes the change of polarization state of optical signals during transmission in optical fiber. Due to the imperfection of optical fiber and external environmental factors (such as temperature, stress, etc.), the polarization state of optical signals may rotate randomly during transmission. This rotation will affect the signal quality and the performance of coherent detection. Therefore, when designing optical fiber communication systems, it is necessary to consider the impact of polarization rotation and take corresponding compensation measures.

[0017] Differential Group Delay (DGD): Differential group delay refers to the difference in arrival time caused by different path lengths of two orthogonal polarization states of optical signals transmitted in optical fiber due to birefringence in polarization multiplexing systems. DGD is a manifestation of polarization mode dispersion (PMD), which is an indicator of the difference in transmission speed of optical fiber for signals with different polarization states. DGD will cause signal pulse broadening, affecting signal integrity and system bit error rate performance. In high-speed optical fiber communication systems, compensation of DGD is one of the key technologies to ensure signal quality. Summary of the invention

[0018] The purpose of the present invention is to solve one of the technical problems existing in the prior art to at least a certain extent.

[0019] To this end, an object of an embodiment of the present invention is to provide a method for estimating timing errors in coherent optical communications, which can effectively tolerate dispersion and polarization rotation effects, while reducing the complexity of timing error estimation in coherent optical communications and improving the robustness of optical communication systems and their adaptability to different channel conditions.

[0020] Another object of an embodiment of the present invention is to provide a coherent optical communication timing error estimation system.

[0021] In order to achieve the above technical objectives, the technical solutions adopted by the embodiments of the present invention include:

[0022] In a first aspect, an embodiment of the present invention provides a method for estimating timing error in coherent optical communication, comprising the following steps:

[0023] Acquire a first discrete digital signal and a second discrete digital signal with orthogonal polarizations, and perform matched filtering and resampling on the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum;

[0024] Performing dispersion scanning on the first signal spectrum and the second signal spectrum, estimating channel dispersion parameters according to the maximum clock modulation, and performing dispersion effect compensation on the first signal spectrum and the second signal spectrum according to the channel dispersion parameters to obtain a first polarization signal and a second polarization signal;

[0025] A target CAF matrix of high-order cyclic statistics is calculated according to the first polarization signal and the second polarization signal, and timing error information is determined according to the target CAF matrix.

[0026] Further, in one embodiment of the present invention, performing matched filtering and resampling on the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum specifically includes:

[0027] Performing matched filtering and resampling on the first discrete digital signal to obtain a third discrete digital signal, and then intercepting the third discrete digital signal according to a preset time length to obtain the first signal spectrum;

[0028] The second discrete digital signal is subjected to matched filtering and resampling to obtain a fourth discrete digital signal, and the fourth discrete digital signal is further intercepted according to the time length to obtain the second signal spectrum.

[0029] Further, in one embodiment of the present invention, the dispersion scanning of the first signal spectrum and the second signal spectrum, estimating the channel dispersion parameter according to the maximum clock modulation, and compensating the dispersion effect of the first signal spectrum and the second signal spectrum according to the channel dispersion parameter to obtain the first polarization signal and the second polarization signal specifically includes:

[0030] Introducing a plurality of preset dispersion effects of different vector positions in the frequency domain of the first signal spectrum and the second signal spectrum to obtain corresponding third polarization signals and fourth polarization signals;

[0031] Determine a first CAF matrix according to the third polarization signal and the fourth polarization signal;

[0032] Calculating first clock modulations corresponding to a plurality of dispersion effects of different degrees according to the first CAF matrix, and then selecting a maximum value of the first clock modulations as the maximum clock modulation;

[0033] The channel dispersion parameter is obtained by estimating the vector position corresponding to the maximum clock modulation;

[0034] The first signal spectrum is compensated for dispersion effect according to the channel dispersion parameter to obtain the first polarization signal, and the second signal spectrum is compensated for dispersion effect according to the channel dispersion parameter to obtain the second polarization signal.

[0035] Further, in one embodiment of the present invention, determining a first CAF matrix according to the third polarization signal and the fourth polarization signal specifically includes:

[0036] Calculating four corresponding first cyclic periodogram functions according to the third polarization signal and the fourth polarization signal, and estimating four corresponding first SCF functions according to the first cyclic periodogram functions;

[0037] Performing an inverse Fourier transform on the first SCF function to obtain corresponding four first CAF functions, and then generating the first CAF matrix according to the first CAF function.

[0038] Further, in one embodiment of the present invention, the target CAF matrix of calculating the high-order cyclic statistics according to the first polarization signal and the second polarization signal specifically includes:

[0039] Calculating a sum of squares of a modulus of the first polarization signal and a modulus of the second polarization signal to obtain a first target signal;

[0040] Calculating a mean value of the first target signal, and determining a second target signal according to a difference between the first target signal and the mean value;

[0041] Determine four target cyclic periodogram functions of the second target signal within a sampling frequency range, and estimate corresponding four target SCF functions according to the target cyclic periodogram functions;

[0042] The target SCF function is subjected to inverse Fourier transform to obtain four corresponding target CAF functions, and then the target CAF matrix is ​​generated according to the target CAF function.

[0043] Further, in one embodiment of the present invention, the determining determines the timing error information according to the target CAF matrix, which is specifically:

[0044] The timing error information is determined according to the imaginary part of the inverse of the first element of the target CAF matrix.

[0045] In a second aspect, an embodiment of the present invention provides a coherent optical communication timing error estimation system, including:

[0046] A signal processing module, used for acquiring a first discrete digital signal and a second discrete digital signal with orthogonal polarizations, performing matched filtering and resampling on the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum;

[0047] a dispersion scanning module, configured to perform dispersion scanning on the first signal spectrum and the second signal spectrum, estimate a channel dispersion parameter according to a maximum clock modulation, and perform dispersion effect compensation on the first signal spectrum and the second signal spectrum according to the channel dispersion parameter to obtain a first polarization signal and a second polarization signal;

[0048] A timing error determination module is used to calculate a target CAF matrix of high-order cyclic statistics according to the first polarization signal and the second polarization signal, and determine timing error information according to the target CAF matrix.

[0049] Further, in one embodiment of the present invention, the dispersion scanning module includes:

[0050] A dispersion effect introduction unit, used to introduce dispersion effects of a plurality of preset different vector positions in the frequency domain of the first signal spectrum and the second signal spectrum to obtain corresponding third polarization signals and fourth polarization signals;

[0051] A CAF matrix calculation unit, configured to determine a first CAF matrix according to the third polarization signal and the fourth polarization signal;

[0052] a maximum clock modulation determining unit, configured to calculate first clock modulations corresponding to a plurality of dispersion effects of different degrees according to the first CAF matrix, and then select a maximum value of the first clock modulations as the maximum clock modulation;

[0053] a dispersion parameter determining unit, configured to determine and obtain the channel dispersion parameter according to the vector position estimation corresponding to the maximum clock modulation;

[0054] The dispersion effect compensation unit is used to compensate the dispersion effect of the first signal spectrum according to the channel dispersion parameter to obtain the first polarization signal, and to compensate the dispersion effect of the second signal spectrum according to the channel dispersion parameter to obtain the second polarization signal.

[0055] In a third aspect, an embodiment of the present invention provides a coherent optical communication timing error estimation device, including:

[0056] at least one processor;

[0057] at least one memory for storing at least one program;

[0058] When the at least one program is executed by the at least one processor, the at least one processor implements the above-mentioned coherent optical communication timing error estimation method.

[0059] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, which stores a program executable by a processor, and the program executable by the processor is used to execute the above-mentioned method for estimating timing errors in coherent optical communications when executed by the processor.

[0060] The advantages and beneficial effects of the present invention will be partly given in the following description, partly become apparent from the following description, or be understood through the practice of the present invention:

[0061] The embodiment of the present invention obtains a first discrete digital signal and a second discrete digital signal of orthogonal polarization, performs matched filtering and resampling on the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum, performs dispersion scanning on the first signal spectrum and the second signal spectrum, estimates channel dispersion parameters according to the maximum clock modulation, and compensates for dispersion effects on the first signal spectrum and the second signal spectrum according to the channel dispersion parameters to obtain a first polarization signal and a second polarization signal, calculates a target CAF matrix of high-order cyclic statistics according to the first polarization signal and the second polarization signal, and determines timing error information according to the target CAF matrix. The embodiment of the present invention can effectively tolerate dispersion and polarization rotation effects, while reducing the complexity of timing error estimation in coherent optical communications, and improving the robustness and adaptability of optical communication systems to different channel conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solution in the embodiments of the present invention, the following introduction is made to the drawings required for use in the embodiments of the present invention. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solution of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0063] Figure 1 A flowchart of the steps of a timing error estimation method for coherent optical communication provided by an embodiment of the present invention;

[0064] Figure 2 A block diagram of a coherent optical communication simulation platform provided by an embodiment of the present invention;

[0065] Figure 3 An S-curve jitter diagram of the timing error estimation method for coherent optical communication provided by an embodiment of the present invention at different roll-off factors;

[0066] Figure 4An S-curve jitter diagram of the coherent optical communication timing error estimation method provided by an embodiment of the present invention at different optical fiber lengths;

[0067] Figure 5 A structural block diagram of a coherent optical communication timing error estimation system provided by an embodiment of the present invention;

[0068] Figure 6 A structural block diagram of a coherent optical communication timing error estimation device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0069] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0070] In the description of the present invention, the meaning of "a plurality" is two or more than two. If there is a description of "a first" or "a second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features. In addition, unless otherwise defined, all technical and scientific terms used in this document have the same meaning as those commonly understood by those skilled in the art.

[0071] The timing error estimation algorithm proposed in the present invention can effectively tolerate the dispersion and polarization effects in the system, can be adapted to Nyquist systems and non-Nyquist coherent optical fiber communication scenarios, and provides a timing synchronization solution for optical communication systems in actual complex channel environments.

[0072] Existing algorithms, such as 4PPD, have insufficient tolerance when processing Nyquist signals with low roll-off factors, which limits their application in practical optical communication systems because practical systems may have lower roll-off factors due to various factors (such as device characteristics, transmission distance, pursuit of higher spectral efficiency, etc.).

[0073] The present invention designs a timing error estimation algorithm by utilizing high-order cyclic statistics, thereby improving the tolerance to low roll-off factor signals, so that the algorithm can run stably under a wider range of system parameters.

[0074] Traditional timing error estimation methods are sensitive to dispersion and polarization rotation effects in optical fiber channels, which may cause algorithm performance degradation in the presence of these effects.

[0075] The present invention enhances the tolerance of the algorithm to the effects of dispersion and polarization rotation by applying high-order cyclic statistics, thereby providing accurate timing error estimation even under complex channel conditions.

[0076] Reference Figure 1 The embodiment of the present invention provides a method for estimating timing error in coherent optical communication, which specifically includes the following steps:

[0077] S101 , obtaining a first discrete digital signal and a second discrete digital signal with orthogonal polarizations, performing matched filtering and resampling on the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum.

[0078] As an optional implementation, matching filtering and resampling are performed on the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum, which specifically includes:

[0079] S1011, performing matched filtering and resampling on the first discrete digital signal to obtain a third discrete digital signal, and then intercepting the third discrete digital signal according to a preset time length to obtain a first signal spectrum;

[0080] S1012, performing matched filtering and resampling on the second discrete digital signal to obtain a fourth discrete digital signal, and then intercepting the fourth discrete digital signal according to a time length to obtain a second signal spectrum.

[0081] Specifically, after the coherent receiver obtains the orthogonally polarized discrete digital signals x and y, matched filtering and resampling are first performed, and then the x and y data with a time length of W are intercepted to obtain the first signal spectrum and the second signal spectrum.

[0082] S102, performing dispersion scanning on the first signal spectrum and the second signal spectrum, estimating channel dispersion parameters according to the maximum clock modulation, and performing dispersion effect compensation on the first signal spectrum and the second signal spectrum according to the channel dispersion parameters to obtain a first polarization signal and a second polarization signal.

[0083] Specifically, the presence of dispersion will affect the size of the CAF matrix clock adjustment. Before extracting the timing error, a fine scan of the dispersion can be performed to obtain the point of maximum clock adjustment, and then the timing error can be extracted. Using this method, the timing error estimation algorithm can tolerate the influence of dispersion and polarization random rotation effects even in a Nyquist system with a roll-off factor close to zero.

[0084] Further as an optional implementation, dispersion scanning is performed on the first signal spectrum and the second signal spectrum, channel dispersion parameters are estimated according to the maximum clock modulation, and dispersion effects are compensated for the first signal spectrum and the second signal spectrum according to the channel dispersion parameters to obtain the first polarization signal and the second polarization signal, which specifically includes:

[0085] S1021, introducing a plurality of preset dispersion effects of different vector positions in the frequency domain of the first signal spectrum and the second signal spectrum to obtain corresponding third polarization signals and fourth polarization signals;

[0086] S1022, determining a first CAF matrix according to the third polarization signal and the fourth polarization signal;

[0087] S1023, calculating a plurality of first clock modulations corresponding to dispersion effects of different degrees according to the first CAF matrix, and then selecting a maximum value of the first clock modulations as a maximum clock modulation;

[0088] S1024, estimating a channel dispersion parameter according to a vector position corresponding to the maximum clock modulation;

[0089] S1025. Compensate for dispersion effects on the first signal spectrum according to the channel dispersion parameter to obtain a first polarization signal, and compensate for dispersion effects on the second signal spectrum according to the channel dispersion parameter to obtain a second polarization signal.

[0090] Further as an optional implementation manner, determining a first CAF matrix according to the third polarization signal and the fourth polarization signal specifically includes:

[0091] S10221. Calculate four corresponding first cyclic periodogram functions according to the third polarization signal and the fourth polarization signal, and obtain four corresponding first SCF functions according to the first cyclic periodogram function estimation;

[0092] S10222. Perform an inverse Fourier transform on the first SCF function to obtain corresponding four first CAF functions, and then generate a first CAF matrix according to the first CAF function.

[0093] Specifically, a plurality of preset dispersion effects of different degrees are introduced into the frequency domain of the first signal spectrum and the second signal spectrum to obtain the corresponding third polarization signal X and fourth polarization signal Y, and then the corresponding four first cycle periodogram functions are calculated as follows:

[0094]

[0095]

[0096] The cyclic periodogram function can be regarded as an estimation of the spectral correlation function SCF. Therefore, the cyclic correlation function CAF can be estimated by performing an inverse Fourier transform on it. Then the four CAF functions are written in matrix form, and the influence of the spectral response H=exp(jKf2) corresponding to the dispersion effect on a single SCF and CAF is studied; and the CAF matrix of the two-polarization multiplexed signal is constructed, which contains four variables {CAFxx, CAFxy, CAFyx, CAFyy}, to study the influence of polarization effect on SCF and CAF.

[0097] There are two feasible methods for calculating the CAF sequence. In the embodiment of the present invention, the SCF function obtained by estimating the cyclic periodogram function is inversely transformed to obtain the CAF sequence. In addition, the CAF sequence can be directly calculated in the time domain according to the definition of CAF. After the CAF sequence is generated, the delay module is used to determine the delay amount n according to the peak position of the specific formula, and then the first value of the delayed CAF sequence is used to form a CAF matrix.

[0098] The clock modulation under different dispersion conditions can be calculated based on the determined first CAF matrix. The relevant formula is as follows:

[0099]

[0100] in, Indicates clock modulation, abs is the modulus operator, mean is the mean operator, CAF(1) is the first value of the CAF sequence, and CAF(end) is the last value of the CAF sequence.

[0101] Calculate the clock modulation corresponding to different first CAF matrices Then, select the largest The value is used as the maximum clock modulation to determine the corresponding vector position m.

[0102] The channel dispersion parameter DL is estimated based on m, and the relevant formula is as follows:

[0103] DL=17E-6*0.5*(m-1)*1E3

[0104] After the channel dispersion parameter is calculated, the dispersion effect of the first signal spectrum and the second signal spectrum is compensated according to the channel dispersion parameter, so that the first polarization signal and the second polarization signal can be obtained.

[0105] S103 : Calculate a target CAF matrix of high-order cyclic statistics according to the first polarization signal and the second polarization signal, and determine timing error information according to the target CAF matrix.

[0106] Further as an optional implementation, a target CAF matrix of a high-order cyclic statistic is calculated according to the first polarization signal and the second polarization signal, which specifically includes:

[0107] S1031, calculating the sum of the squares of the modulus of the first polarization signal and the modulus of the second polarization signal to obtain a first target signal;

[0108] S1032, calculating the mean of the first target signal, and determining the second target signal according to the difference between the first target signal and the mean;

[0109] S1033, determining four target cyclic periodogram functions of the second target signal within the sampling frequency range, and estimating four corresponding target SCF functions according to the target cyclic periodogram functions;

[0110] S1034, performing inverse Fourier transform on the target SCF function to obtain corresponding four target CAF functions, and then generating a target CAF matrix according to the target CAF function.

[0111] Specifically, the linear modulation signal is calculated The cumulative amount of high-order cycles and its multispectral form (Using the fourth-order statistics E{x(t+τ1)x * (t+τ2)x(t+τ3)x * (t)} as an example):

[0112]

[0113] Among them C a,4 is the fourth-order accumulant of the signal symbol set It is easy to prove that the second-order cyclic quantity (i.e., the aforementioned CAF and SCF functions) of a severely band-limited signal in a Nyquist system is zero, but the fourth-order statistical characteristics are not zero, so the high-order statistics of the signal are and It can be used as the theoretical basis for the timing error detection algorithm in this scenario.

[0114] In the embodiment of the present invention, the square sum of the modulus of the first polarization signal and the modulus of the second polarization signal is calculated to obtain the first target signal, and then the mean of the first target signal is calculated, and the second target signal is determined according to the difference between the first target signal and the mean. The relevant formula is as follows:

[0115] z1[n]=x[n]·x[n] * +y[n]·y[n] *

[0116] z2[n]=z1[n]-mean(z1[n])

[0117] Wherein, z1[n] represents the first target signal, z2[n] represents the second target signal, x[n] represents the first polarization signal, and y[n] represents the second polarization signal.

[0118] Determine the four target cyclic periodogram functions of the second target signal within the sampling frequency range, and estimate the corresponding four target SCF functions based on the target cyclic periodogram functions. Perform an inverse Fourier transform on the target SCF functions to obtain the corresponding four target CAF functions. Then, generate the target CAF matrix based on the target CAF functions. The relevant formula is as follows:

[0119]

[0120] Where CAF[n] represents the target CAF matrix, SCF[n] represents the target SCF function, ifft represents the inverse Fourier transform, and length represents the length of the calculated sequence.

[0121] Further as an optional implementation manner, determining the timing error information according to the target CAF matrix is ​​specifically as follows:

[0122] S1035. Determine timing error information according to the imaginary part of the opposite number of the first element of the target CAF matrix.

[0123] Specifically, for the random polarization rotation of the optical fiber channel, the relationship between the input and output signals is considered.

[0124]

[0125] Since |ax-b * y| 2 +|bx+a * y| 2 Equivalent to |x| 2 +|y| 2 It is independent of the polarization rotation matrix, so |ax-b * y| 2 +|bx+a * y| 2 To cope with the polarization rotation effect. Therefore, the formula for timing error estimation based on high-order cyclic statistics that can tolerate polarization rotation can be expressed as:

[0126]

[0127] Where z = xx * +yy * , Z=fft(z), fft represents Fourier transform.

[0128] After obtaining the target CAF matrix, the timing error information is estimated according to the following formula:

[0129] tmp=-imag{-CAF(1)}

[0130] Wherein, tmp represents the timing error information, and -imag{} is the imaginary part of the complex number.

[0131] Use Matlab simulation platform to simulate a series of devices and channel effects such as optical pulse shaping, optical signal modulation, fiber channel dispersion, polarization mode dispersion, polarization-dependent loss, random polarization rotation, fiber channel amplifier noise and fiber nonlinear damage, and simulate optical coherent reception, digital signal sampling and digital signal processing at the receiving end. Figure 2 The figure shows a block diagram of a coherent optical communication simulation platform provided by an embodiment of the present invention. By comparing the performance of different timing synchronization algorithms under different system parameter combinations, the algorithm theory and applicable scenarios of the embodiment of the present invention are verified.

[0132] like Figure 3 The S-curve jitter diagram of the coherent optical communication timing error estimation method provided by the embodiment of the present invention under different roll-off factors is as follows: Figure 4 The figure shows the S-curve jitter diagram of the timing error estimation method for coherent optical communication provided by an embodiment of the present invention at different fiber lengths. The S-curve is a commonly used tool for demonstrating the performance of a timing error estimation algorithm. It reveals the relationship between the estimated sampling error value and the true value. This curve intuitively reflects the accuracy and reliability of the timing sampling error estimation algorithm. The most important and widely used performance indicator of the timing error detection algorithm is the timing jitter, which is defined as the variance of the zero-crossing position of the so-called S-curve, which represents the variation between the estimated timing error and the actual timing error.

[0133] Figure 3 and Figure 4 The S-curve simulation results of the timing error estimation algorithm of the embodiment of the present invention in a severely band-limited Nyquist system are shown, wherein: Figure 3 The S curve of the timing error estimation algorithm based on high-order cyclic quantity proposed by the present invention is shown. Figure 4 The S curves of the classic 4PPD algorithm timing error estimation algorithm and the timing error estimation algorithm of the embodiment of the present invention are shown. Random polarization rotation is introduced into the system. The simulation results show that the high-order timing error estimation algorithm proposed in the embodiment of the present invention can effectively tolerate the polarization rotation effect. In order to further verify the performance of the proposed algorithm, Figure 3 The S curve of the high-order algorithm under different system roll-off coefficients is shown. The results show that the algorithm proposed in the present invention is not only applicable to severely band-limited Nyquist systems, but also to Nyquist systems with larger roll-off coefficients. Figure 4The S-curve jitter of the high-order timing error estimation algorithm proposed in the embodiment of the present invention and the classic 4PPD algorithm timing error estimation algorithm at different optical fiber distances is demonstrated. It can be observed that under various optical fiber length conditions, the S-curve jitter of the algorithm provided by the embodiment of the present invention is very small. This result further confirms the algorithm's tolerance to dispersion effects.

[0134] The above is a detailed description of the step flow of the embodiment of the present invention. It can be understood that the embodiment of the present invention can effectively tolerate the dispersion and polarization rotation effects, while reducing the complexity of coherent optical communication timing error estimation, and improving the robustness of the optical communication system and the adaptability to different channel conditions.

[0135] Compared with the prior art, the embodiments of the present invention also have the following advantages:

[0136] 1) Improved robustness: The timing error estimation algorithm based on high-order cyclic statistics proposed in the present invention is specially designed to deal with the timing error estimation problem in severely band-limited Nyquist systems. Compared with the 4PPD algorithm, the algorithm of the present invention can more effectively handle the bandwidth-limited situation of the signal because it uses the high-order statistical characteristics of the signal to extract the timing error information. This means that even when the spectral information of the signal is limited, the algorithm of the present invention can still maintain high performance and accuracy.

[0137] 2) Tolerance to dispersion and polarization effects: In optical communication systems, dispersion and polarization effects are the main factors affecting signal integrity. The algorithm of the present invention takes these channel effects into consideration when designing, and uses high-order cyclic statistics to reduce the negative impact of error estimation during dispersion and polarization rotation. This may not be fully addressed in the 4PPD algorithm because 4PPD mainly targets the second-order statistical characteristics of the signal.

[0138] 3) System performance: Since the algorithm of the present invention can estimate the timing error more accurately, it can significantly improve the synchronization performance and transmission quality of the signal in the actual optical communication system, which is crucial to improving the performance and reliability of the overall system.

[0139] In summary, the algorithm of the present invention shows better performance than the prior art when dealing with the timing error estimation problem under complex channel conditions, especially in terms of robustness, tolerance to dispersion and polarization effects, versatility and adaptability, and computational efficiency. These advantages make the algorithm of the present invention have significant advantages in practical applications and can provide a more reliable and efficient timing synchronization solution for high-speed optical fiber communication systems.

[0140] Reference Figure 5 , an embodiment of the present invention provides a coherent optical communication timing error estimation system, comprising:

[0141] A signal processing module, used for acquiring a first discrete digital signal and a second discrete digital signal with orthogonal polarizations, performing matched filtering and resampling on the first discrete digital signal and the second discrete digital signal, to obtain a first signal spectrum and a second signal spectrum;

[0142] A dispersion scanning module, used for performing dispersion scanning on the first signal spectrum and the second signal spectrum to determine the first polarization signal and the second polarization signal corresponding to the maximum clock modulation;

[0143] A high-order cyclic statistics calculation module, used to determine a target signal according to the first polarization signal and the second polarization signal, and calculate a high-order cyclic statistics of the target signal;

[0144] The timing error information determination module is used to determine a target CAF matrix of a high-order cyclic statistic and determine the timing error information according to the target CAF matrix.

[0145] Further as an optional implementation, the dispersion scanning module includes:

[0146] A dispersion effect introduction unit, used to introduce dispersion effects of a plurality of preset different vector positions in the frequency domain of the first signal spectrum and the second signal spectrum to obtain corresponding third polarization signals and fourth polarization signals;

[0147] A CAF matrix calculation unit, used for determining a first CAF matrix according to the third polarization signal and the fourth polarization signal;

[0148] a maximum clock modulation determining unit, configured to calculate first clock modulations corresponding to a plurality of dispersion effects of different degrees according to a first CAF matrix, and then select a maximum value of the first clock modulations as the maximum clock modulation;

[0149] A dispersion parameter determination unit, used to estimate the channel dispersion parameter according to the vector position corresponding to the maximum clock modulation;

[0150] The dispersion effect compensation unit is used to compensate the dispersion effect of the first signal spectrum according to the channel dispersion parameter to obtain a first polarization signal, and to compensate the dispersion effect of the second signal spectrum according to the channel dispersion parameter to obtain a second polarization signal.

[0151] The contents of the above method embodiments are all applicable to the present system embodiments. The functions specifically implemented by the present system embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0152] Reference Figure 6 , an embodiment of the present invention provides a coherent optical communication timing error estimation device, comprising:

[0153] at least one processor;

[0154] at least one memory for storing at least one program;

[0155] When the at least one program is executed by the at least one processor, the at least one processor implements the coherent optical communication timing error estimation method.

[0156] The contents of the above method embodiments are all applicable to the present device embodiments. The functions specifically implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0157] An embodiment of the present invention further provides a computer-readable storage medium, in which a program executable by a processor is stored. When the program executable by the processor is executed by the processor, it is used to execute the above-mentioned coherent optical communication timing error estimation method.

[0158] A computer-readable storage medium according to an embodiment of the present invention can execute a coherent optical communication timing error estimation method provided by a method embodiment of the present invention, can execute any combination of implementation steps of the method embodiment, and has the corresponding functions and beneficial effects of the method.

[0159] The embodiment of the present invention also discloses a computer program product or a computer program, wherein the computer program product or the computer program includes computer instructions, and the computer instructions are stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes Figure 1 The method shown.

[0160] In some selectable embodiments, the function / operation mentioned in the block diagram may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the above-mentioned boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the present invention is provided by way of example, for the purpose of providing a more comprehensive understanding of technology. The disclosed method is not limited to the operation and logic flow presented herein. Selectable embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part for which is described as a larger operation is performed independently.

[0161] In addition, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise specified to the contrary, one or more of the above-mentioned functions and / or features can be integrated into a single physical device and / or software module, or one or more functions and / or features can be implemented in a separate physical device or software module. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the present invention. More specifically, in view of the properties, functions and internal relationships of the various functional modules in the device disclosed herein, the actual implementation of the module will be understood within the conventional skills of the engineer. Therefore, those skilled in the art can implement the present invention set forth in the claims without excessive experimentation using ordinary techniques. It is also understood that the specific concepts disclosed are merely illustrative and are not intended to limit the scope of the present invention, which is determined by the full scope of the appended claims and their equivalents.

[0162] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the above methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0163] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0164] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and editable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the above-mentioned program is printed, since the above-mentioned program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or processing in other suitable ways as necessary, and then stored in a computer memory.

[0165] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0166] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0167] 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 claims and their equivalents.

[0168] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A timing error estimation method for coherent optical communication, It is characterized in that The following steps are involved: Acquire a first discrete digital signal and a second discrete digital signal with orthogonal polarizations, perform matched filtering and resampling on the first discrete digital signal and the second discrete digital signal, and obtain a first signal spectrum and a second signal spectrum; Performing dispersion scanning on the first signal spectrum and the second signal spectrum, estimating channel dispersion parameters according to the maximum clock modulation, and performing dispersion effect compensation on the first signal spectrum and the second signal spectrum according to the channel dispersion parameters to obtain a first polarization signal and a second polarization signal; A target CAF matrix of high-order cyclic statistics is calculated according to the first polarization signal and the second polarization signal, and timing error information is determined according to the target CAF matrix.

2. A method for estimating timing error in coherent optical communication according to claim 1, It is characterized in that The matching filtering and resampling of the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum specifically includes: Performing matched filtering and resampling on the first discrete digital signal to obtain a third discrete digital signal, and then intercepting the third discrete digital signal according to a preset time length to obtain the first signal spectrum; The second discrete digital signal is subjected to matched filtering and resampling to obtain a fourth discrete digital signal, and the fourth discrete digital signal is further intercepted according to the time length to obtain the second signal spectrum.

3. A method for estimating timing error in coherent optical communication according to claim 2, It is characterized in that The dispersion scanning of the first signal spectrum and the second signal spectrum, estimating the channel dispersion parameter according to the maximum clock modulation, and compensating the dispersion effect of the first signal spectrum and the second signal spectrum according to the channel dispersion parameter to obtain the first polarization signal and the second polarization signal specifically includes: Introducing a plurality of preset dispersion effects of different vector positions in the frequency domain of the first signal spectrum and the second signal spectrum to obtain corresponding third polarization signals and fourth polarization signals; Determine a first CAF matrix according to the third polarization signal and the fourth polarization signal; Calculating first clock modulations corresponding to a plurality of dispersion effects of different degrees according to the first CAF matrix, and then selecting a maximum value of the first clock modulations as the maximum clock modulation; The channel dispersion parameter is obtained by estimating the vector position corresponding to the maximum clock modulation; The first signal spectrum is compensated for dispersion effect according to the channel dispersion parameter to obtain the first polarization signal, and the second signal spectrum is compensated for dispersion effect according to the channel dispersion parameter to obtain the second polarization signal.

4. A method for estimating timing error in coherent optical communication according to claim 2, It is characterized in that The determining of the first CAF matrix according to the third polarization signal and the fourth polarization signal specifically includes: Calculating four corresponding first cyclic periodogram functions according to the third polarization signal and the fourth polarization signal, and estimating four corresponding first SCF functions according to the first cyclic periodogram functions; Performing an inverse Fourier transform on the first SCF function to obtain corresponding four first CAF functions, and then generating the first CAF matrix according to the first CAF function.

5. A method for estimating timing error in coherent optical communication according to claim 1, It is characterized in that The step of calculating a target CAF matrix of a high-order cyclic statistic according to the first polarization signal and the second polarization signal specifically includes: Calculating a sum of squares of a modulus of the first polarization signal and a modulus of the second polarization signal to obtain a first target signal; Calculating a mean value of the first target signal, and determining a second target signal according to a difference between the first target signal and the mean value; Determine four target cyclic periodogram functions of the second target signal within a sampling frequency range, and estimate corresponding four target SCF functions according to the target cyclic periodogram functions; The target SCF function is subjected to inverse Fourier transform to obtain four corresponding target CAF functions, and then the target CAF matrix is ​​generated according to the target CAF function.

6. A method for estimating timing error in coherent optical communication according to any one of claims 1 to 5, It is characterized in that The determining determines the timing error information according to the target CAF matrix, which is specifically: The timing error information is determined according to the imaginary part of the inverse of the first element of the target CAF matrix.

7. A coherent optical communication timing error estimation system, It is characterized in that include: A signal processing module, used for acquiring a first discrete digital signal and a second discrete digital signal with orthogonal polarizations, performing matched filtering and resampling on the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum; a dispersion scanning module, configured to perform dispersion scanning on the first signal spectrum and the second signal spectrum, estimate a channel dispersion parameter according to a maximum clock modulation, and perform dispersion effect compensation on the first signal spectrum and the second signal spectrum according to the channel dispersion parameter to obtain a first polarization signal and a second polarization signal; A timing error determination module is used to calculate a target CAF matrix of high-order cyclic statistics according to the first polarization signal and the second polarization signal, and determine timing error information according to the target CAF matrix.

8. A coherent optical communication timing error estimation system according to claim 7, It is characterized in that The dispersion scanning module comprises: A dispersion effect introduction unit, used to introduce dispersion effects of a plurality of preset different vector positions in the frequency domain of the first signal spectrum and the second signal spectrum to obtain corresponding third polarization signals and fourth polarization signals; A CAF matrix calculation unit, configured to determine a first CAF matrix according to the third polarization signal and the fourth polarization signal; a maximum clock modulation determining unit, configured to calculate first clock modulations corresponding to a plurality of dispersion effects of different degrees according to the first CAF matrix, and then select a maximum value of the first clock modulations as the maximum clock modulation; a dispersion parameter determining unit, configured to determine and obtain the channel dispersion parameter according to the vector position estimation corresponding to the maximum clock modulation; The dispersion effect compensation unit is used to compensate the dispersion effect of the first signal spectrum according to the channel dispersion parameter to obtain the first polarization signal, and to compensate the dispersion effect of the second signal spectrum according to the channel dispersion parameter to obtain the second polarization signal.

9. A timing error estimation device for coherent optical communication, It is characterized in that include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements a coherent optical communication timing error estimation method according to any one of claims 1 to 6.

10. A computer-readable storage medium having a program executable by a processor stored therein, It is characterized in that The program executable by the processor is used to execute a coherent optical communication timing error estimation method according to any one of claims 1 to 6 when executed by the processor.

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