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

Abstract

The present invention discloses a method, system, device, and storage medium for estimating timing errors in coherent optical communications, comprising: obtaining a first discrete digital signal and a second discrete digital signal of 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; performing dispersion scanning on the first signal spectrum and the second signal spectrum, estimating channel dispersion parameters based on maximum clock modulation, and performing dispersion effect compensation on the first signal spectrum and the second signal spectrum based on the channel dispersion parameters to obtain a first polarization signal and a second polarization signal; calculating a target CAF matrix of high-order cyclic statistics based on the first polarization signal and the second polarization signal, and determining timing error information based on the target CAF matrix. The present invention reduces the complexity of timing error estimation in coherent optical communications, improves the robustness and adaptability of optical communication systems to different channel conditions, and can be applied to the field of optical communication technology.

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. In particular, in high-speed coherent optical communication systems, ultra-high-speed data transmission can be achieved through the use of advanced modulation formats and digital signal processing technologies. Coherent detection technology in coherent optical communication systems can provide higher signal detection sensitivity and 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 crucial 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 the face of these complex channel effects, which significantly impact the performance of timing error estimation algorithms. These effects can reduce the spectral correlation of signals, thereby affecting the accurate estimation of timing error. To achieve high performance in practically deployed optical communication systems, timing error estimation algorithms must be highly robust and adaptable to various channel conditions and non-ideal factors.

[0004] In high-speed coherent optical communication systems, accurate clock recovery is crucial to ensuring the reliability of data transmission. In the existing technology, 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 searching 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), they typically rely on static electronic dispersion compensation (EDC) or polarization mode dispersion (PMD) compensators to mitigate the impact of channel impairments on TED performance. This means that in systems with high dispersion, these algorithms may not be directly applicable and require pre-processing of channel impairments.

[0006] Another class of methods involves joint algorithms for Nyquist systems, which add an adaptive equalization and polarization demultiplexing (AEPD) module before clock recovery. These algorithms can effectively compensate for differential group delay (DGD) and intersymbol interference (ISI) in the channel, thereby improving overall system performance. However, these algorithms typically rely on training sequences or pilot symbols, and the TED algorithm itself is not sufficiently robust against DGD impairments. For example, robust clock recovery algorithms for digital multiband systems based on OQAM, while performing well in multiband systems, may require further improvement in single-band systems.

[0007] In summary, although 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 still need to be improved in terms of robustness, adaptability and algorithm complexity.

[0008] Explanation of terms:

[0009] Coherent Optical Communication: Coherent optical communication is an advanced optical communication technology that utilizes lasers as light sources and uses coherent detection techniques to improve signal reception sensitivity and transmission quality. In a coherent optical communication system, the transmitting signal modulates the laser's optical carrier, while the receiving end uses a local laser synchronized with the transmitting end to perform coherent mixing to detect the amplitude and phase information of the transmitted signal. This technology significantly increases signal transmission distance and system capacity.

[0010] Chromatic Dispersion (CD): Chromatic dispersion refers to the phenomenon of pulse broadening caused by the different speeds of light at different wavelengths in optical signals transmitted through optical fibers. Dispersion distorts the signal's time domain waveform, affecting signal integrity and thus degrading communication system performance. Chromatic dispersion, which includes both material dispersion and waveguide dispersion, is a key impairment factor that requires consideration and compensation in long-haul optical fiber communication systems.

[0011] Nyquist System: A Nyquist system is a signal sampling system that satisfies the Nyquist sampling theorem. According to the Nyquist sampling theorem, to avoid aliasing, the sampling frequency of a signal should be at least twice the highest frequency of the signal. In fiber-optic communications, a Nyquist system typically refers to a digital signal processing system that meets this condition and can accurately reconstruct the original analog signal from the sampled data.

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

[0013] DSP (Digital Signal Processing Technology): DSP technology refers to the use of digital circuits or computers to process signals. In fiber-optic communication systems, DSP technology is widely used in key aspects such as signal modulation, demodulation, equalization, dispersion compensation, and timing recovery. DSP technology enables efficient signal processing, optimizes system performance, and improves transmission quality.

[0014] Roll-off Factor (ROF): The roll-off factor describes the rate at which a signal's spectrum decays. It is used in digital communication systems to filter signals and limit their bandwidth. Signals with smaller roll-off factors have slower decay edges, meaning they occupy a wider spectrum. Signals with larger roll-off factors have faster decay edges and a narrower spectrum. The choice of roll-off factor affects the system's transmission efficiency and anti-interference capabilities.

[0015] Polarization Division Multiplexing (PDM): Polarization division multiplexing (PDM) is a technology that increases the capacity of fiber-optic communication systems. It leverages the polarization properties of optical signals to double the data rate by simultaneously transmitting signals in two orthogonal polarization states through the same optical fiber. Each polarization state can independently carry information, effectively acting as two independent communication channels. Polarization division multiplexing can be combined with other multiplexing technologies, such as wavelength division multiplexing (WDM), to further improve the system's spectral efficiency and transmission capacity.

[0016] Polarization rotation (RSOP) describes the change in the polarization state of an optical signal during optical fiber transmission. Due to fiber imperfections and external environmental factors (such as temperature and stress), the polarization state of an optical signal may randomly rotate during transmission. This rotation can affect signal quality and coherent detection performance. Therefore, the effects of polarization rotation must be considered and compensated for in the design of optical fiber communication systems.

[0017] Differential Group Delay (DGD): In polarization-multiplexing systems, DGD refers to the difference in arrival time caused by the different path lengths of two optical signals with orthogonal polarization states transmitted through an optical fiber due to birefringence. DGD is a manifestation of polarization mode dispersion (PMD), a measure of the difference in transmission speed of optical fibers for signals with different polarization states. DGD causes signal pulse broadening, affecting signal integrity and the system's bit error rate performance. In high-speed optical fiber communication systems, DGD compensation is a key technology for ensuring 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 and adaptability of optical communication systems 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 errors in coherent optical communication, comprising the following steps:

[0023] 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 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 a channel dispersion parameter according to a maximum clock modulation, 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;

[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] Furthermore, 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] Matched filtering and resampling are performed on the second discrete digital signal to obtain a fourth discrete digital signal, and then the fourth discrete digital signal is intercepted according to the time length to obtain the second signal spectrum.

[0029] Furthermore, in one embodiment of the present invention, performing dispersion scanning on the first signal spectrum and the second signal spectrum, estimating channel dispersion parameters based on maximum clock modulation, and compensating for dispersion effects on the first signal spectrum and the second signal spectrum based on the channel dispersion parameters to obtain the first polarization signal and the second polarization signal specifically includes:

[0030] Introducing a plurality of preset dispersion effects at 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, according to the first CAF matrix, a plurality of first clock tones corresponding to dispersion effects of different degrees, and then selecting a maximum value of the first clock tones as the maximum clock tone;

[0033] Obtaining the channel dispersion parameter according to the vector position estimation corresponding to the maximum clock modulation;

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

[0035] Furthermore, 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] An inverse Fourier transform is performed on the first SCF function to obtain corresponding four first CAF functions, and then the first CAF matrix is ​​generated according to the first CAF functions.

[0038] Furthermore, in one embodiment of the present invention, calculating a target CAF matrix of a high-order cyclic statistic 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 of the first target signal, and determining a second target signal according to a difference between the first target signal and the mean;

[0041] Determining four target cyclic periodogram functions of the second target signal within a sampling frequency range, and estimating four corresponding target SCF functions based on the target cyclic periodogram functions;

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

[0043] Furthermore, in one embodiment of the present invention, the determining of the timing error information according to the target CAF matrix 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, configured to obtain 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;

[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 compensate for dispersion effects 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 configured to calculate a target CAF matrix of high-order cyclic statistics based on the first polarization signal and the second polarization signal, and determine timing error information based on the target CAF matrix.

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

[0050] a dispersion effect introducing unit, configured to introduce dispersion effects of a plurality of preset different vector positions into 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, based on the first CAF matrix, a plurality of first clock modulations corresponding to dispersion effects of different degrees, and then select a maximum value of the first clock modulations as the maximum clock modulation;

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

[0054] The dispersion effect compensation unit is used to compensate the first signal spectrum for dispersion effects according to the channel dispersion parameter to obtain the first polarization signal, and to compensate the second signal spectrum for dispersion effects 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 is enabled to implement the above-mentioned method for estimating timing errors in coherent optical communication.

[0059] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium storing a program executable by a processor, wherein 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 benefits of the present invention will be described in part in the following description and will become apparent from the following description or learned through 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 polarizations, 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 the channel dispersion parameters according to the maximum clock modulation, and compensates for the dispersion effects of 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 a high-order cyclic statistic 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 the effects of dispersion and polarization rotation, 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 solutions 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 solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any 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 S-curve jitter diagrams of the coherent optical communication timing error estimation method provided by an embodiment of the present invention at different roll-off factors;

[0066] Figure 4S-curve jitter diagram of the timing error estimation method for coherent optical communication 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 This is a structural block diagram of a timing error estimation device for coherent optical communication provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0069] The embodiments of the present invention are described in detail below, examples of which 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 limiting the present invention. The step numbers in the following embodiments are provided for ease of explanation only and do not limit the order of the steps. The order of execution of the steps in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0070] In the description of the present invention, "a plurality" means two or more. The terms "first" and "second" are used solely to distinguish technical features and are not to be construed as indicating or implying relative importance, or as implicitly indicating the number of the indicated technical features, or as implicitly indicating the order of the indicated technical features. Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as 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 adapt 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, as practical systems may have lower roll-off factors due to various factors (such as device characteristics, transmission distance, and the pursuit of higher spectral efficiency).

[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 and enabling the algorithm to operate 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 lead to algorithm performance degradation in the presence of these effects.

[0075] The present invention enhances the tolerance of the algorithm to dispersion and polarization rotation effects 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 : Acquire a first discrete digital signal and a second discrete digital signal with orthogonal polarizations, perform matched filtering and resample the first discrete digital signal and the second discrete digital signal to obtain a first signal spectrum and a second signal spectrum.

[0078] As a further optional implementation, matching filtering and resampling are performed on the first discrete digital signal and the second discrete digital signal to obtain the first signal spectrum and the 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 . Perform matched filtering and resampling on the second discrete digital signal to obtain a fourth discrete digital signal, and then intercept the fourth discrete digital signal according to a time length to obtain a second signal spectrum.

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

[0082] S102 : Perform dispersion scanning on the first signal spectrum and the second signal spectrum, estimate channel dispersion parameters according to the maximum clock modulation, and compensate 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.

[0083] Specifically, the presence of chromatic dispersion affects the magnitude of the CAF matrix clock adjustment. Before extracting the timing error, a fine sweep of the chromatic dispersion can be performed to obtain the point of maximum clock adjustment, and then the timing error can be extracted. This approach allows the timing error estimation algorithm to tolerate the effects of chromatic dispersion and random polarization rotation, even in Nyquist systems with a roll-off factor close to zero.

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

[0085] S1021. Introduce a plurality of preset dispersion effects at 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. Determine a first CAF matrix according to the third polarization signal and the fourth polarization signal;

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

[0088] S1024. Obtain channel dispersion parameters based on the estimated 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 polarized signal, and compensate for dispersion effects on the second signal spectrum according to the channel dispersion parameter to obtain a second polarized signal.

[0090] As an optional implementation, 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 functions;

[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 based on the first CAF functions.

[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 cyclic 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 corresponding to the dispersion effect H = exp(jKf2) on the 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 a CAF sequence. In one embodiment of the present invention, the CAF sequence is obtained by performing an inverse Fourier transform on the SCF function, which is estimated using a cyclic periodogram function. Alternatively, the CAF sequence can be calculated directly in the time domain based on the definition of CAF. After the CAF sequence is generated, the delay module determines the delay n based on the peak position of a specific formula. The first value of the delayed CAF sequence is then used to construct the CAF matrix.

[0098] Based on the determined first CAF matrix, the clock modulation under different dispersion conditions can be calculated. 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 adjustment to determine the corresponding vector position m.

[0102] The channel dispersion parameter DL is estimated based on m. 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 as to obtain the first polarization signal and the second polarization signal.

[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 manner, calculating a target CAF matrix of a high-order cyclic statistic according to the first polarization signal and the second polarization signal specifically includes:

[0107] S1031. Calculate 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. Calculate the mean of the first target signal, and determine the second target signal based on the difference between the first target signal and the mean;

[0109] S1033. Determine four target cyclic periodogram functions of the second target signal within the sampling frequency range, and estimate four corresponding target SCF functions based on the target cyclic periodogram functions;

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

[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 accumulator 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 higher-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 this 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 a first target signal. Then, the mean of the first target signal is calculated, and the second target signal is determined based on 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 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 is the inverse Fourier transform, and length is the length of the calculated sequence.

[0121] As an optional implementation, the timing error information is determined based on the target CAF matrix, specifically:

[0122] S1035 : Determine timing error information according to the imaginary part of the inverse 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 following figure shows an S-curve jitter plot of the timing error estimation method for coherent optical communications at different fiber lengths, as provided by an embodiment of the present invention. 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 and the true value, and this curve intuitively reflects the accuracy and reliability of the timing sampling error estimation algorithm. The most important and widely used performance metric for timing error detection algorithms is timing jitter, which is defined as the variance of the zero-crossing positions 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 are shown in a severely band-limited Nyquist system, where: 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-curves of the high-order algorithm under different system roll-off factors are shown. The results show that the algorithm proposed in this paper is not only applicable to severely band-limited Nyquist systems, but also to Nyquist systems with larger roll-off factors. 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 fiber distances is demonstrated. It can be observed that under various 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 describes in detail the steps of the embodiment of the present invention. It can be understood that the embodiment of the present invention can effectively tolerate the effects of dispersion and polarization rotation, while reducing the complexity of timing error estimation in coherent optical communications, and improving the robustness of the optical communication system and its 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 proposed in this paper, based on high-order cyclic statistics, is specifically designed to address the timing error estimation problem in severely band-limited Nyquist systems. Compared to the 4PPD algorithm, this algorithm is more effective in bandwidth-limited signal conditions because it leverages the signal's high-order statistical properties to extract timing error information. This means that even when the signal's spectral information is limited, the algorithm maintains high performance and accuracy.

[0137] 2) Tolerance to dispersion and polarization effects: In optical communication systems, dispersion and polarization effects are major factors affecting signal integrity. The algorithm of this invention takes these channel effects into account in its design, using high-order cyclic statistics to mitigate the negative impact of dispersion and polarization rotation error estimation. This issue may not be fully addressed in the 4PPD algorithm, as 4PPD primarily targets the second-order statistical properties of the signal.

[0138] 3) System Performance: Because the algorithm of the present invention can more accurately estimate timing errors, it can significantly improve signal synchronization and transmission quality in actual optical communication systems. This is crucial for improving overall system performance and reliability.

[0139] In summary, the algorithm of the present invention demonstrates superior performance compared to existing technologies when addressing timing error estimation in complex channel conditions, particularly 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 significantly advantageous in practical applications, enabling it to provide a more reliable and efficient timing synchronization solution for high-speed fiber-optic 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, configured to obtain 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;

[0142] A dispersion scanning module, configured to perform 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, configured to determine a target signal based on 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] As an optional implementation, the dispersion scanning module includes:

[0146] a dispersion effect introducing unit, configured to introduce dispersion effects of a plurality of preset different vector positions into the frequency domains 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, configured to determine 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, based on the first CAF matrix, a plurality of first clock modulations corresponding to dispersion effects of different degrees, and then select a maximum value of the first clock modulations as the maximum clock modulation;

[0149] a dispersion parameter determination unit, configured to estimate the channel dispersion parameter based on the vector position corresponding to the maximum clock modulation;

[0150] The dispersion effect compensation unit is used to compensate the first signal spectrum for dispersion effects according to the channel dispersion parameter to obtain a first polarization signal, and to compensate the second signal spectrum for dispersion effects 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 aforementioned method for estimating timing errors in coherent optical communications.

[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 storing a program executable by a processor. When the program is executed by the processor, it is used to execute the above-mentioned method for estimating timing errors in coherent optical communications.

[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 an embodiment of the method of the present invention, can execute any combination of implementation steps of the embodiment of the method, 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 computer program, which includes computer instructions 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 performs Figure 1 The method shown.

[0160] In some optional 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 in an exemplary manner for the purpose of providing a more comprehensive understanding of the technology. The disclosed method is not limited to the operation and logic flow presented herein. Optional embodiments are contemplated in which the order of the various operations is changed and the sub-operations described as a part of a larger operation are performed independently.

[0161] In addition, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise stated, 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 separate physical devices or software modules. It is also understood that a detailed discussion of the actual implementation of each module is not necessary for understanding the present invention. More specifically, given the properties, functions, and internal relationships of the various functional modules in the devices disclosed herein, the actual implementation of the module will be understood within the routine skills of an engineer. Therefore, a person skilled in the art can implement the present invention set forth in the claims using ordinary skills without undue experimentation. 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 and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute 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 code.

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

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

[0165] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof can be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application-specific 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, reference to the terms "one embodiment / example," "another embodiment / example," or "certain embodiments / examples" 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 suitable manner in any one or more embodiments or examples.

[0167] While 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 invention, and that the scope of the 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 can 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 method for estimating timing error in coherent optical communication, 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 to obtain a first signal spectrum and a second signal spectrum; Performing dispersion scanning on the first signal spectrum and the second signal spectrum, estimating a channel dispersion parameter according to a maximum clock modulation, 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; 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; The performing dispersion scanning on the first signal spectrum and the second signal spectrum, estimating a channel dispersion parameter according to a maximum clock modulation, 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 specifically includes: Introducing a plurality of preset dispersion effects at 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, according to the first CAF matrix, a plurality of first clock tones corresponding to dispersion effects of different degrees, and then selecting a maximum value of the first clock tones as the maximum clock tone; Obtaining the channel dispersion parameter according to the vector position estimation corresponding to the maximum clock modulation; The first signal spectrum is compensated for dispersion effects according to the channel dispersion parameter to obtain the first polarization signal, and the second signal spectrum is compensated for dispersion effects according to the channel dispersion parameter to obtain the second polarization signal.

2. A coherent optical communication timing error estimation method according to claim 1, characterized in that: The 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: 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; Matched filtering and resampling are performed on the second discrete digital signal to obtain a fourth discrete digital signal, and then the fourth discrete digital signal is intercepted according to the time length to obtain the second signal spectrum.

3. A coherent optical communication timing error estimation method according to claim 1, characterized in that: The determining a 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; An inverse Fourier transform is performed on the first SCF function to obtain corresponding four first CAF functions, and then the first CAF matrix is ​​generated according to the first CAF functions.

4. A coherent optical communication timing error estimation method according to claim 1, 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 of the first target signal, and determining a second target signal according to a difference between the first target signal and the mean; Determining four target cyclic periodogram functions of the second target signal within a sampling frequency range, and estimating four corresponding target SCF functions based on the target cyclic periodogram functions; An inverse Fourier transform is performed on the target SCF function to obtain four corresponding target CAF functions, and then the target CAF matrix is ​​generated according to the target CAF functions.

5. A method for estimating timing error in coherent optical communication according to any one of claims 1 to 4, characterized in that: The determining of the timing error information according to the target CAF matrix 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.

6. A coherent optical communication timing error estimation system, characterized in that: include: a signal processing module, configured to obtain 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; 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 compensate for dispersion effects 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, configured to calculate a target CAF matrix of high-order cyclic statistics based on the first polarization signal and the second polarization signal, and determine timing error information based on the target CAF matrix; The dispersion scanning module includes: a dispersion effect introducing unit, configured to introduce dispersion effects of a plurality of preset different vector positions into 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, based on the first CAF matrix, a plurality of first clock modulations corresponding to dispersion effects of different degrees, and then select a maximum value of the first clock modulations as the maximum clock modulation; a dispersion parameter determining unit, configured to estimate and obtain the channel dispersion parameter according to the vector position corresponding to the maximum clock modulation; The dispersion effect compensation unit is used to compensate the first signal spectrum for dispersion effects according to the channel dispersion parameter to obtain the first polarization signal, and to compensate the second signal spectrum for dispersion effects according to the channel dispersion parameter to obtain the second polarization signal.

7. A coherent optical communication timing error estimation device, 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 the coherent optical communication timing error estimation method according to any one of claims 1 to 5.

8. A computer-readable storage medium storing a program executable by a processor, characterized in that: The program executable by the processor is used to perform a coherent optical communication timing error estimation method according to any one of claims 1 to 5 when executed by the processor.

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