A carrier-free auxiliary signal phase reconstruction method and system based on a time domain symmetry architecture

Abstract

The application relates to the technical field of optical fiber communication, and discloses a carrier-free auxiliary signal phase reconstruction method and system based on a time domain symmetric architecture, which comprises the following steps: constructing a symmetric dispersion compensation FIR filter based on a symmetric time domain impulse response function in a dispersion transfer function; obtaining time domain amplitudes of a to-be-detected optical signal and a dispersion optical signal; embedding the symmetric dispersion compensation FIR filter into a GS iteration algorithm to reconstruct a phase based on the time domain amplitudes of the to-be-detected optical signal and the dispersion optical signal, and obtaining a reconstruction result; wherein, in each iteration process, the time domain amplitude of the optical signal of the current iteration is dispersion compensated through the symmetric dispersion compensation FIR filter; the coefficients of the symmetric dispersion compensation FIR filter are subjected to fixed-point quantization processing in the calculation process of the dispersion compensation, and the same coefficient items in the coefficients are combined. Compared with the prior art, the application reduces the calculation complexity of phase reconstruction.

Description

Technical Field

[0001] This invention relates to the field of optical fiber communication technology, and in particular to a carrier-free signal phase reconstruction method and system based on a time-domain symmetric architecture. Background Technology

[0002] In short-range optical interconnect applications between data centers, phase-reconstruction optical receiving technology based on the Gerchberg-Saxton (GS) iterative algorithm has been proposed to meet the ever-increasing capacity demands. This technology aims to combine the advantages of coherent detection and direct detection. Its receiving architecture is functionally similar to a coherent optical interconnect system, capable of compensating for various channel impairments through signal optical field recovery and supporting high-order modulation formats for high-speed, high-capacity transmission. Simultaneously, structurally, it is closer to an intensity-modulated direct detection (IMDD) system, eliminating the need for expensive local oscillator lasers and avoiding the need for frequency offset and phase noise compensation at the receiver, thus simplifying the digital signal processing flow. This allows for the use of low-cost, large-linewidth uncooled lasers at the transmitter, making it a potential application in power- and cost-sensitive short-range interconnect scenarios.

[0003] Current phase reconstruction optical receivers based on the GS algorithm primarily rely on the received original signal strength information and the signal strength information after specific dispersion filtering. Using this strength information, the GS phase reconstruction algorithm iteratively solves the problem to ultimately obtain the phase information of the original signal. However, this phase reconstruction process is essentially a nonlinear optimization problem, typically requiring dozens or even more iterations to achieve the desired phase reconstruction accuracy. Furthermore, each iteration requires multiple dispersion compensation operations. These intensive dispersion compensation calculations constitute the main computational burden of the algorithm, significantly increasing the computational complexity of each iteration and limiting its practical application in short-distance optical interconnect systems with high real-time requirements or limited resources. Summary of the Invention

[0004] To overcome the high computational complexity of the prior art, this invention provides a carrier-free signal phase reconstruction method and system based on a time-domain symmetric architecture.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A carrier-free signal phase reconstruction method based on a time-domain symmetric architecture includes:

[0007] A symmetric dispersion-compensated FIR filter is constructed based on the symmetric time-domain impulse response function in the dispersion transfer function;

[0008] Obtain the time-domain amplitude of the optical signal under test; obtain the time-domain amplitude of the dispersed light signal after the optical signal under test has been processed by the dispersive element;

[0009] The symmetric dispersion-compensated FIR filter is embedded in the GS iterative algorithm to reconstruct the phase based on the time-domain amplitude of the optical signal under test and the time-domain amplitude of the dispersive optical signal, and the reconstruction result is obtained; wherein, in each iteration, the time-domain amplitude of the optical signal of the current iteration is dispersion-compensated by the symmetric dispersion-compensated FIR filter.

[0010] In the process of calculating the dispersion compensation, the coefficients of the symmetric dispersion compensation FIR filter are quantized at fixed points, and the same coefficient terms in the coefficients are merged.

[0011] This invention also proposes a carrier-free signal phase reconstruction system based on a time-domain symmetric architecture, the system comprising:

[0012] Signal construction module: acquires the time-domain amplitude of the optical signal under test; acquires the time-domain amplitude of the dispersed light signal after the optical signal under test has been processed by the dispersive element;

[0013] GS algorithm iteration module: used to reconstruct the phase from the time-domain amplitude of the optical signal under test and the time-domain amplitude of the dispersive light signal, and obtain the reconstruction result;

[0014] Simplified dispersion compensation module: It is equipped with a symmetrical dispersion compensation FIR filter, which is used to perform dispersion compensation on the time domain amplitude of the dispersed light signal during the iteration of the GS iterative algorithm.

[0015] The present invention also proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a carrier-free signal phase reconstruction method based on a time-domain symmetric architecture as described in the present invention.

[0016] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0017] This invention designs a simplified dispersion compensation scheme with a time-domain symmetric structure. By using a symmetric dispersion-compensated FIR filter, it effectively reduces the computational resource consumption in each phase reconstruction iteration, solving the problem of excessive computational resource consumption in traditional signal phase reconstruction algorithms. While ensuring phase reconstruction accuracy, it minimizes computational complexity. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the carrier-free signal phase reconstruction method based on a time-domain symmetric architecture in Example 1.

[0019] Figure 2This is a diagram of the symmetric dispersion-compensating FIR filter architecture of Example 1;

[0020] Figure 3 This is a schematic diagram of the carrierless auxiliary signal phase reconstruction process in Example 1;

[0021] Figure 4 This is a schematic diagram of the carrierless signal phase reconstruction system architecture based on a time-domain symmetric architecture in Example 2;

[0022] Figure 5 This is a scatter plot of the IQ constellation of the optical signal without phase reconstruction in Example 3;

[0023] Figure 6 This is the 16QAM constellation diagram of the optical signal after phase reconstruction in Example 3. Detailed Implementation

[0024] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0025] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions.

[0026] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Example 1

[0029] This embodiment proposes a carrier-free signal phase reconstruction method based on a time-domain symmetric architecture, such as... Figure 1 The diagram shown is a schematic flowchart of a carrier-free signal phase reconstruction method based on a time-domain symmetric architecture according to this embodiment.

[0030] A carrier-free signal phase reconstruction method based on a time-domain symmetric architecture includes:

[0031] S1: Construct a symmetric dispersion-compensated FIR filter based on the symmetric time-domain impulse response function in the dispersion transfer function;

[0032] S2: Obtain the time-domain amplitude of the optical signal under test; Obtain the time-domain amplitude of the dispersed light signal after the optical signal under test has been processed by the dispersive element;

[0033] S3: The symmetrical dispersion-compensating FIR filter is embedded in the GS iterative algorithm to reconstruct the phase based on the time-domain amplitude of the optical signal under test and the time-domain amplitude of the dispersive optical signal, and the reconstruction result is obtained; wherein, in each iteration, the time-domain amplitude of the optical signal of the current iteration is dispersion-compensated by the symmetrical dispersion-compensating FIR filter.

[0034] S4: During the calculation of the dispersion compensation, the coefficients of the symmetric dispersion compensation FIR filter are quantized at fixed points, and the same coefficient terms in the coefficients are merged.

[0035] Traditional frequency domain dispersion compensation methods require using Fast Fourier Transform (FFT) to convert the data from the time domain to the frequency domain, then multiplying it with the dispersion compensation transfer function for frequency domain equalization, and finally converting it back to the time domain using Inverse Fast Fourier Transform (IFFT). In carrier-free signal phase reconstruction systems, frequency domain dispersion equalization-based methods require continuous FFT / IFFT operations, resulting in excessive complexity.

[0036] In this embodiment, the dispersion compensation processing based on the symmetric dispersion compensation FIR filter effectively solves the problem of excessively high tap number of the time-domain equalization filter, and eliminates the need for repeated FFT / IFFT operations, significantly reducing the computational complexity during the algorithm iteration process.

[0037] In an optional embodiment, the coefficients within the symmetric dispersion-compensated FIR filter are obtained based on sampling of a symmetric time-domain impulse response function, the expression of which is as follows:

[0038]

[0039]

[0040]

[0041] in These are the signals before and after dispersion compensation, respectively; N represents the number of FIR filter taps, and must be an odd number. The coefficients are represented by the time-domain impulse response function. Obtained by sampling; This is the dispersion compensation transfer function.

[0042] In this embodiment, the time-domain impulse response function It is symmetrical about the origin, while the FIR filter coefficients Yes The coefficients are obtained through discrete sampling. It is also symmetrical about the origin, and the coefficients on the axis of symmetry do not need to be calculated repeatedly, thus reducing complex number multiplication operations by 50%.

[0043] like Figure 2 The diagram shown is an architecture diagram of a symmetric dispersion-compensated FIR filter.

[0044] In an optional embodiment, the step of performing fixed-point quantization on the coefficients includes: normalizing all coefficients based on the largest absolute value between the real and imaginary parts of the coefficients, and rounding the processed coefficients, as shown in the following expression:

[0045]

[0046] in, Represents the coefficient. for The discrete value after quantization; the quantization parameter Δ is a positive integer that is a power of 2, and its value ranges from 2^b, where b is the number of quantization bits; and They are The real and imaginary parts, Indicates rounding down;

[0047] The expression for the dispersion-compensated FIR filter after quantization is:

[0048]

[0049] in It is the dispersion-compensated signal obtained using quantization coefficients. This represents the symmetrical summation of the input signal.

[0050] In this embodiment, the quantization level is 2Δ+1, and Δ determines the quantization coefficient. and Possible values ​​of 2Δ+1 This embodiment employs a specific form of quantization parameter Δ (a power of 2) to perform a specific fixed-point quantization process on the dispersion compensation filter coefficients, significantly reducing the computational complexity of the phase reconstruction optical receiver based on the GS algorithm. This can be simplified to low-resource-consumption integer operations or shift operations.

[0051] In an optional embodiment, the steps of the GS iterative algorithm include:

[0052] The time-domain amplitude of the light signal under test and the time-domain amplitude of the dispersive light signal are used as dual amplitude constraints. The loading and compensation of dispersion are simulated iteratively by the GS algorithm. The time-domain amplitude of the dispersive light signal is compensated based on the symmetric dispersion compensation FIR filter until a preset number of iterations is reached or the amplitude difference between the time-domain amplitude of the light signal under test and the time-domain amplitude of the reconstructed signal in the current iteration is less than a preset threshold.

[0053] More specifically, the time-domain amplitude of the photoelectric signal to be measured Time-domain amplitude of the dispersive light signal The amplitude signal is obtained by performing a root mean square (RMS) operation, i.e.:

[0054]

[0055]

[0056] in This represents the initial signal amplitude before it passes through the dispersive element. This represents the initial signal amplitude after passing through the dispersive element. Within the GS iterative algorithm, the signal phase is reconstructed iteratively by adding dispersion and dispersion compensation, utilizing the mapping relationship between intensity and phase. In the first iteration, the signal phase is first... Set a random initial phase To construct a complete initial signal The dispersion introduced by the SSMF link is then compensated by a symmetrical dispersion-compensating FIR filter. The signal is then subjected to a root raised cosine (RRC) filter for spectral constraint, and pilot constraints are achieved by inserting pilot signals at specific locations. The pilot-constrained signal is then subjected to another RRC filter for spectral constraint. Next, the dispersion introduced by the SSMF link and the dispersive element D is applied to the signal. The amplitude component of the signal obtained after passing through the dispersive element is then measured using amplitude... Replacement, forming a new signal For the new The signal is obtained after the dispersion of the dispersive element D is compensated. Then use amplitude replace The amplitude constitutes a new signal The phase of the signal is updated after each iteration until the preset maximum number of iterations is reached, or the iteration is terminated by calculating whether the amplitude error between the time domain amplitudes of the signal under test and the optical signal under test is less than a decision threshold.

[0057] like Figure 3 The diagram shown is a schematic of the phase reconstruction process for a carrier-free assisted signal.

[0058] In an optional embodiment, the step of merging identical coefficient terms in the coefficients includes:

[0059] To combine input signals with the same coefficient, first calculate the sum of the input signals with the same coefficient; the expression is as follows:

[0060]

[0061]

[0062]

[0063] in, This represents the real part of the signal after filter dispersion compensation; This represents the imaginary part of the signal after dispersion compensation by the filter. for, For the quantized values ​​of the coefficients; The real part of the input signal is respectively and the virtual part The summation result.

[0064] In this embodiment, the quantization coefficient may take the following values: exist and With It appeared multiple times. and The number of possible values ​​decreases as Δ decreases, thus increasing repeatability. Since the quantized filter coefficients are repeatable, the distributive law of multiplication relative to addition is further utilized to reduce the number of multiplication operations between the input sample and the quantized coefficients. Considering that each FIR coefficient consists of a real and an imaginary part, and that the repeatability of complex coefficients is often much smaller than the repeatability of each real and imaginary part, the real and imaginary parts of the complex coefficients can be processed independently.

[0065] In an optional embodiment, during the GS algorithm iteration process, after preprocessing SSMF link distortion based on the symmetric dispersion compensation FIR filter, frequency-time domain joint constraints are constructed through a two-stage RRC filter and pilot anchor injection. The steps are as follows:

[0066] The signal of the current iteration is spectrally constrained by an RRC filter. A known pilot is inserted at a preset position of the filtered signal, and the signal constrained by the pilot is then spectrally constrained by an RRC filter.

[0067] In this embodiment, by introducing a dual-stage RRC filter and pilot joint constraint mechanism in the phase reconstruction iteration, the convergence speed and anti-interference capability of the algorithm are significantly improved. RRC filters are deployed at both the front and back ends of the iterative signal processing link for spectral constraint, effectively suppressing out-of-band noise and constraining the spectral spread range, ensuring that signal energy is always concentrated within the effective bandwidth of the channel. Secondly, the insertion of known pilots at preset positions provides a stable phase reference point for the phase reconstruction process. By forcibly aligning the phase information of the pilot points, the phase accumulation error during the iteration process is corrected.

[0068] In an optional embodiment, the dispersion-compensating FIR filter removes [certain substances] before performing dispersion compensation. The coefficients in the quantized values ​​that are below a preset threshold.

[0069] In this embodiment, to further reduce computational complexity, the following can be done: Perform pruning. Remove branches based on a preset pruning threshold p. and Coefficient terms with amplitudes below a preset threshold, for example... And in as well as The expression does not need to consider sets Because they correspond to the zero coefficient in the quantization process. Ultimately, the decision is based on the repeatability of the quantization coefficients and the distributive law properties.

[0070] Example 2

[0071] This embodiment proposes a carrier-free signal phase reconstruction system based on a time-domain symmetric architecture, applying a carrier-free signal phase reconstruction method based on a time-domain symmetric architecture proposed in Embodiment 1. For example... Figure 4 The diagram shown is an architecture diagram of a carrier-free signal phase reconstruction system based on a time-domain symmetric architecture according to this embodiment.

[0072] This embodiment proposes a carrier-free signal phase reconstruction system based on a time-domain symmetric architecture, including:

[0073] A carrier-free signal phase reconstruction system based on a time-domain symmetric architecture, applying the aforementioned carrier-free signal phase reconstruction method based on a time-domain symmetric architecture, includes:

[0074] Signal construction module: acquires the time-domain amplitude of the optical signal under test; acquires the time-domain amplitude of the dispersed light signal after the optical signal under test has been processed by the dispersive element;

[0075] GS algorithm iteration module: used to reconstruct the phase from the time-domain amplitude of the optical signal under test and the time-domain amplitude of the dispersive light signal, and obtain the reconstruction result;

[0076] Simplified dispersion compensation module: It is equipped with a symmetrical dispersion compensation FIR filter, which is used to perform dispersion compensation on the time domain amplitude of the dispersed light signal during the iteration of the GS iterative algorithm.

[0077] Further optionally, the GS algorithm iteration module in the system further includes a spectrum constraint module, a pilot constraint module, and an amplitude constraint module; the spectrum constraint module is used to perform RRC spectrum filtering operation on the current iteration signal; the pilot constraint module is used to insert pilot signals into the current iteration signal at preset positions.

[0078] It is understood that the system in this embodiment corresponds to the method in Embodiment 1 above, and the options in Embodiment 1 above are also applicable to this embodiment, so they will not be described again here.

[0079] Example 3

[0080] This embodiment provides a specific implementation of the carrierless assisted signal phase reconstruction method based on a time-domain symmetric architecture proposed in Embodiment 1.

[0081] A 16QAM signal with a baud rate of 56 Gbaud is generated at the transmitting end. The roll-off factor of the root-raised cosine (RRC) filter is 0.1, the transmitter laser linewidth is 105 Hz, and the inserted pilot overhead accounts for 20% of the total number of symbols. The transmission link is a standard single-mode fiber with a transmission distance of 80 km. The fiber's dispersion coefficient is 17 ps / nm / km, and its loss coefficient is 0.2 dB / km. The optical signal-to-noise ratio (OSNR) of the transmission system is set to 27 dB. After transmission through the fiber, the signal is split into two paths by an optical beamsplitter. One path is directly detected and recorded by a photodetector (PD), while the other path first passes through a dispersive element before being detected and recorded by the PD. By adding dispersion, the phase change of the symbol is converted into intensity fluctuations, and combined with a low-complexity signal phase reconstruction algorithm, the signal phase is finally recovered.

[0082] like Figure 5 The image shows a scatter plot of the IQ constellation of the optical signal without phase reconstruction; as shown... Figure 6 The diagram shown is a 16QAM constellation diagram of the optical signal after phase reconstruction.

[0083] Figure 5 The middle part is almost a "clump" that is severely contaminated by phase noise or amplitude-phase coupling. Figure 6 The typical 16-QAM (4×4) constellation point array can be clearly identified, and the symbol interval and cluster center are basically recovered. The phase reconstruction method of this application plays an effective phase correction role.

[0084] Example 4

[0085] This embodiment proposes a computer device, including a memory and a processor. The memory stores computer-readable instructions, wherein when the computer-readable instructions are executed by the processor, the processor performs the steps of the carrier-free assisted signal phase reconstruction method based on a time-domain symmetric architecture proposed in Embodiment 1.

[0086] The same or similar labels correspond to the same or similar parts;

[0087] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0088] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A carrier-free signal phase reconstruction method based on a time-domain symmetric architecture, characterized in that, Includes the following steps: A symmetric dispersion-compensated FIR filter is constructed based on the symmetric time-domain impulse response function in the dispersion transfer function; Obtain the time-domain amplitude of the optical signal under test; obtain the time-domain amplitude of the dispersed light signal after the optical signal under test has been processed by the dispersive element; The symmetric dispersion-compensated FIR filter is embedded in the GS iterative algorithm to reconstruct the phase based on the time-domain amplitude of the optical signal under test and the time-domain amplitude of the dispersive optical signal, and the reconstruction result is obtained; wherein, in each iteration, the time-domain amplitude of the optical signal of the current iteration is dispersion-compensated by the symmetric dispersion-compensated FIR filter. In the process of calculating the dispersion compensation, the coefficients of the symmetric dispersion compensation FIR filter are quantized at fixed points, and the same coefficient terms in the coefficients are merged.

2. The carrierless signal phase reconstruction method based on a time-domain symmetric architecture according to claim 1, characterized in that, The coefficients in the symmetric dispersion-compensated FIR filter are obtained by sampling based on the symmetric time-domain impulse response function, and its expression is as follows: in These are the signals before and after dispersion compensation, respectively; N represents the number of FIR filter taps, and must be an odd number. The coefficients are represented by the time-domain impulse response function. Obtained by sampling; This is the dispersion compensation transfer function.

3. The carrierless signal phase reconstruction method based on a time-domain symmetric architecture according to claim 1, characterized in that, The steps for fixed-point quantization of the coefficients include: normalizing all coefficients based on the largest absolute value between the real and imaginary parts of the coefficients, and rounding the processed coefficients to the nearest integer, as shown in the following expression: in, Represents the coefficient. for The discrete value after quantization; the quantization parameter Δ is a positive integer that is a power of 2, and its value ranges from 2^b, where b is the number of quantization bits; and They are The real and imaginary parts, Indicates rounding down; The expression for the dispersion-compensated FIR filter after quantization is: in It is the dispersion-compensated signal obtained using quantization coefficients. This represents the symmetrical summation of the input signal.

4. The carrierless signal phase reconstruction method based on a time-domain symmetric architecture according to claim 1, characterized in that, The steps of the GS iterative algorithm include: The time-domain amplitude of the light signal under test and the time-domain amplitude of the dispersive light signal are used as dual amplitude constraints. The loading and compensation of dispersion are simulated iteratively by the GS algorithm. The time-domain amplitude of the dispersive light signal is compensated based on the symmetric dispersion compensation FIR filter until a preset number of iterations is reached or the amplitude difference between the time-domain amplitude of the light signal under test and the time-domain amplitude of the reconstructed signal in the current iteration is less than a preset threshold.

5. The carrierless signal phase reconstruction method based on a time-domain symmetric architecture according to claim 3, characterized in that, The steps for merging identical coefficient terms in the coefficients include: To combine input signals with the same coefficient, first calculate the sum of the input signals with the same coefficient; the expression is as follows: in, This represents the real part of the signal after dispersion compensation by the filter. This represents the imaginary part of the signal after dispersion compensation by the filter. For the quantized values ​​of the coefficients; The real part of the input signal is respectively and the virtual part The summation result.

6. The carrierless signal phase reconstruction method based on a time-domain symmetric architecture according to claim 4, characterized in that, In the iterative process of the GS algorithm, after preprocessing the SSMF link distortion based on the symmetric dispersion compensation FIR filter, a frequency-time domain joint constraint is constructed through a two-stage RRC filter and pilot anchor injection. The steps are as follows: The signal of the current iteration is spectrally constrained by an RRC filter. A known pilot is inserted at a preset position of the filtered signal, and the signal constrained by the pilot is then spectrally constrained by an RRC filter.

7. The carrierless signal phase reconstruction method based on a time-domain symmetric architecture according to claim 5, characterized in that, The dispersion compensation FIR filter removes coefficients whose quantization values ​​are below a preset threshold before performing dispersion compensation.

8. A carrier-free signal phase reconstruction system based on a time-domain symmetric architecture, employing the carrier-free signal phase reconstruction method based on a time-domain symmetric architecture as described in any one of claims 1 to 7, characterized in that, include: Signal construction module: acquires the time-domain amplitude of the optical signal under test; acquires the time-domain amplitude of the dispersed light signal after the optical signal under test has been processed by the dispersive element; GS algorithm iteration module: used to reconstruct the phase from the time-domain amplitude of the optical signal under test and the time-domain amplitude of the dispersive light signal, and obtain the reconstruction result; Simplified dispersion compensation module: It is equipped with a symmetrical dispersion compensation FIR filter, which is used to perform dispersion compensation on the time domain amplitude of the dispersed light signal during the iteration of the GS iterative algorithm.

9. The carrierless signal phase reconstruction system based on a time-domain symmetric architecture according to claim 8, characterized in that, The GS algorithm iteration module in the system also includes a spectrum constraint module, a pilot constraint module, and an amplitude constraint module; the spectrum constraint module is used to perform RRC spectrum filtering operation on the current iteration signal; the pilot constraint module is used to insert pilots into the current iteration signal at preset positions.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the carrier-free signal phase reconstruction method based on a time-domain symmetric architecture as described in any one of claims 1 to 7.

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