Dual-polarization signal phase reconstruction method and system based on full-blind polarization rotation matrix estimation

Abstract

The present invention relates to the technical field of optical fiber communications. Disclosed is a dual-polarization signal phase reconstruction method and system based on full-blind polarization rotation matrix estimation. The method comprises the following specific steps: acquiring a dual-polarization signal to be measured; presetting a polarization rotation matrix parameter α, so as to construct an initial signal; pre-processing the initial signal; performing an amplitude constraint operation on the pre-processed signal; implementing a dispersion compensation algorithm on the amplitude-constrained signal to obtain phase information of a compensated phase signal; calculating an amplitude error between a signal without added dispersion and the initial signal; on the basis of the strength of the dual-polarization signal to be measured and the phase information of the phase signal, obtaining a phase reconstruction signal; iteratively optimizing the phase reconstruction signal to obtain a final phase reconstruction signal; and calculating a bit error rate to approximately obtain the value of α. The present invention solves the problem in the prior art of low phase reconstruction accuracy caused by polarization rotation, and has the characteristic of effectively avoiding polarization fading.

Description

A method and system for phase reconstruction of dual-polarization signals based on fully blind polarization rotation matrix estimation Technical Field

[0001] This invention relates to the field of optical fiber communication technology, and more specifically, to a method and system for phase reconstruction of dual-polarization signals based on fully blind polarization rotation matrix estimation. Background Technology

[0002] With the rapid development of the Internet of Things, cloud computing, and artificial intelligence, data traffic is experiencing explosive growth. The enormous demands of these emerging technologies on bandwidth and computing resources have driven the construction and technological upgrades of numerous large-scale data centers. To meet these ever-increasing demands, developing high-speed, high-capacity optical interconnect technologies for data centers has become a top priority.

[0003] For 400 Gbit / s data center optical interconnects, Intensity Modulation Direct Detection (IMDD) technology has been widely adopted due to its simplicity and cost-effectiveness. However, facing the demand for further increases in communication speed, IMDD technology suffers from insufficient spectral efficiency, power selective fading caused by dispersion, and limitations in optical signal-to-noise ratio. These issues restrict its application in coarse wavelength division multiplexing (WDM) systems for 800 Gbit / s or even 1.6 Tbit / s optical interconnects within a range of 0 to 80 kilometers. Coherent optical communication systems, by employing higher-order modulation formats and polarization multiplexing techniques, can significantly improve transmission capacity and meet the aforementioned speed requirements. However, such systems are complex in structure, consume more power, and are more expensive, greatly limiting their application in cost-sensitive data center optical interconnects.

[0004] In summary, how to invent a signal phase reconstruction method that can solve the problem of low phase reconstruction accuracy caused by polarization rotation in existing technologies is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the problem of low phase reconstruction accuracy caused by polarization rotation in existing technologies, this invention provides a dual-polarization signal phase reconstruction method and system based on fully blind polarization rotation matrix estimation, which effectively avoids polarization fading.

[0006] To achieve the above-mentioned objective of this invention, the technical solution adopted is as follows: A phase reconstruction method for dual-polarized signals based on fully blind polarization rotation matrix estimation, comprising the following specific steps: S1. Acquire the dual-polarized signal to be measured, wherein the dual-polarized signal includes a signal with added dispersion and a signal without added dispersion; construct an initial signal by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion; S2. Preprocess the initial signal; S3. Perform amplitude constraint operation on the preprocessed signal using the amplitude information of the signal with added dispersion; S4. Implement a dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal; S5. Calculate the amplitude error between the signal without added dispersion and the initial signal; combine the intensity of the dual-polarized signal to be measured and the phase information of the phase signal to obtain the phase reconstruction signal; S6. Iteratively optimize the phase reconstruction signal to obtain the final phase reconstruction signal.

[0007] Preferably, in step S1, an initial signal is constructed by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion. Specifically, the steps are as follows: Presetting a polarization rotation matrix parameter α for polarization multiplexing and demultiplexing; parameter α is set as follows:

[0008] Where n represents the total number of values ​​for the polarization rotation matrix parameter α; the larger the value of n, the more accurate the estimation of the polarization rotation matrix. The root mean square values ​​of the undispersed signals in the two polarization states are calculated respectively to obtain the initial signal amplitude. The same root mean square calculation is performed on the signal with added dispersion to obtain the amplitude. in, This will be used to set the strength of the initial signal, while This reserves signal amplitude constraints for subsequent steps; A randomly selected initial phase is assigned to each of the two polarization states of the undispersed dual-polarization signal under test, serving as the starting point for signal processing:

[0009]

[0010] in As the initial signal, The initial phase is randomly selected, and j is the imaginary unit; at the same time, the current iteration counter is set to i = 0.

[0011] Furthermore, in step S2, the initial signal is preprocessed, specifically by: compensating for the dispersion effect accumulated during the transmission of the initial signal through the optical fiber; the amount of dispersion compensated is denoted as , which matches the total dispersion introduced by the optical fiber; the time-domain expression of the compensation process is as follows:

[0012] Among them, Z CD The initial signal represents the transmission distance when dispersion compensation is implemented in the optical fiber link; t represents the signal propagation time; D represents the dispersion coefficient, which quantifies the degree of optical pulse broadening in the optical fiber; λ represents the wavelength of the signal, which relates to the propagation characteristics of light in the medium; c represents the speed of light; for the initial signal... The process of performing dispersion compensation is represented as follows:

[0013]

[0014] Among them, the compensated signal Due to its amplitude and phase Composition, in which This represents the signal amplitude after fiber dispersion compensation, while Represents the corresponding signal phase; The dispersion-compensated signal is polarization demultiplexed according to the preset polarization rotation matrix parameter α, and the estimated polarization rotation matrix is ​​as follows:

[0015] The depolarization multiplexing is implemented as the inverse matrix function of the polarization rotation matrix estimated by signal convolution; the current parameter takes values ​​k times, and the dual-polarization signals before depolarization are represented as follows: Then the demultiplexed signal S′ x (t), S′ y (t) Specifically:

[0016]

[0017] The signal is processed in the frequency domain using a root-raised cosine filter to achieve spectral constraint. Using a signal generated from mapping independent data sequences, pilot replacement is performed on the signal at specific positions according to a predetermined proportion of pilot symbols, thereby achieving pilot constraint in the time domain. The pilot-constrained signal is then processed again using a root-raised cosine filter for spectral constraint. Finally, the polarization rotation matrix is ​​convolved with the pilot-constrained signal for polarization multiplexing.

[0018]

[0019] Additional dispersion is applied to the signal after the second spectral constraint; the total dispersion is CD + CD. add Where CD is the dispersion introduced into the signal during transmission through the optical fiber link, and CD add This refers to the additional dispersion amount; the temporal impulse response of the dispersion addition operation is specifically as follows:

[0020] in, This represents the transmission distance when dispersion addition is applied in the fiber optic link; The preprocessed signal is obtained:

[0021]

[0022] in, This indicates a pre-processed signal. This indicates the amplitude of the preprocessed signal. This indicates the phase of the preprocessed signal.

[0023] Furthermore, in step S3, the amplitude information of the signal with added dispersion is used to perform an amplitude constraint operation on the preprocessed signal. Specifically, the steps are as follows: Based on the amplitude information of the signal with added dispersion, amplitude constraints are performed on the preprocessed signal, and the constrained signal is then used... express:

[0024]

[0025] Furthermore, in step S4, a dispersion compensation algorithm is applied to the amplitude-constrained signal to obtain the phase information of the compensated phase signal. Specifically, the steps are as follows: A dispersion compensation algorithm is applied to the amplitude-constrained signal R′0(t) to obtain the phase information of the compensated phase signal.

[0026]

[0027] Where R x (t), R y (t) is the phase signal. The amplitude of the phase signal after dispersion compensation. This is the phase of the signal at this point; by extracting the compensated signal R... x (t), R y The phase angle of (t) is used to obtain the phase information of the signal:

[0028]

[0029] Furthermore, in step S5, the amplitude error between the undispersed signal and the initial signal is calculated; combining the intensity of the dual-polarized signal to be measured and the phase information of the phase signal, a phase reconstruction signal is obtained. Specifically, the amplitude difference between the dual-polarized signal to be measured and the phase signal is quantified to evaluate the magnitude of the error between them.

[0030] a x (t) represents the dual-polarized signal to be measured without added additional dispersion, A error This represents the calculated amplitude error, which is within a set time window T. error Measurements are performed internally; based on the amplitude of the test signal and the phase information of the phase signal, a phase reconstruction signal is obtained:

[0031]

[0032] in, The obtained phase reconstruction signal.

[0033] Furthermore, in step S6, the final signal is iteratively optimized to obtain the final phase reconstruction signal. Specifically, this involves checking whether the current iteration number i has reached the preset maximum iteration number I. max If the current iteration number i equals I max Once all iterations are complete, the algorithm will output the final phase reconstruction signal S. output (t); if not equal to I max This indicates that the algorithm has not yet completed all the predetermined iterations, so the magnitude error A is calculated. error With the preset decision threshold ε TH Comparison between them; if the amplitude error A error Less than or equal to the decision threshold ε TH A error ≤ε TH If the amplitude error A is not reached, the algorithm terminates and outputs the final signal; if the amplitude error A is not reached, the algorithm terminates and outputs the final signal. error Greater than the decision threshold ε TH A error >ε TH If the phase of the initial signal is updated to the phase of the phase reconstructed signal, the value of the iteration counter i is incremented, and the iteration returns to step S2 for further iteration.

[0034] Furthermore, after obtaining the final phase reconstruction signal, the bit error rate (BER) is calculated on the final phase reconstruction signal. Based on the BER, the value of α is approximated, and the accurate phase reconstruction signal is confirmed. The specific steps are as follows: Determine the current number of times k of the polarization rotation matrix parameter α is taken. If k < n, the current number of times the current value is incremented. If k < n, the current number of times the current value is incremented, and the process returns to step S1 until k = n. Finally, n BER values ​​are obtained. Find the minimum value among the n sets of BER data and use it as the α value in the polarization rotation matrix. Based on the α value, the accurate phase reconstruction signal is confirmed.

[0035] A phase reconstruction system for dual-polarized signals based on fully blind polarization rotation matrix estimation includes a signal generation module, a signal construction module, a preprocessing module, an amplitude constraint module, a dispersion compensation module, an error decision module, an iterative optimization module, and a bit error rate calculation module. The signal generation module acquires the dual-polarized signal to be measured, which includes a signal with added dispersion and a signal without added dispersion. The signal construction module constructs an initial signal by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion. The preprocessing module preprocesses the initial signal. The amplitude constraint module performs amplitude constraint operations on the preprocessed signal using the amplitude information of the signal with added dispersion. The dispersion compensation module performs a dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal. The error decision module calculates the amplitude error between the signal without added dispersion and the initial signal; combining the intensity of the dual-polarized signal to be measured and the phase information of the phase signal, a phase reconstruction signal is obtained. The iterative optimization module iteratively optimizes the phase reconstruction signal to obtain the final phase reconstruction signal.

[0036] Preferably, the signal generation module includes a transmitter and a receiver; the transmitter includes a laser, an I / Q modulator, and a digital-to-analog converter; the receiver includes a polarization beam splitter, an optical splitter, a dispersion element, a photodetector, and an analog-to-digital converter; the transmitter and receiver are connected via an optical fiber transmission link; the laser is used to generate an optical signal; the I / Q modulator is used to perform electro-optical conversion; the digital-to-analog converter is used to convert the digital signal into an analog signal; the polarization beam splitter is used to separate the received optical signal into two output beams with orthogonal polarization states; the photodetector is used to convert the optical signal into an electrical signal; the dispersion element is used to introduce additional dispersion into one of the signals; and the analog-to-digital converter is used to convert the analog electrical signal into a digital signal.

[0037] The beneficial effects of this invention are as follows: This invention employs phase reconstruction technology and polarization multiplexing technology based on signal strength information. By utilizing the amplitude information of the signal with added dispersion, amplitude constraint operation is performed on the preprocessed signal, a dispersion compensation algorithm is applied to the amplitude-constrained signal, and the amplitude error between the undispersioned signal and the initial signal is calculated; this is combined with the intensity of the dual-polarized signal to be measured and the phase information of the phase signal. Therefore, this invention solves the problem of low phase reconstruction accuracy caused by polarization rotation in existing technologies and has the characteristic of effectively avoiding polarization fading. Attached Figure Description

[0038] Figure 1 is a flowchart illustrating a dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to the present invention.

[0039] Figure 2 is a schematic diagram of the signal generation module of a dual-polarization signal phase reconstruction system based on fully blind polarization rotation matrix estimation according to the present invention. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0041] Example 1 As shown in Figure 1, a phase reconstruction method for dual-polarized signals based on fully blind polarization rotation matrix estimation includes the following specific steps: S1. Obtain the dual-polarized signal to be measured, which includes a signal with added dispersion and a signal without added dispersion; construct an initial signal by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion; simultaneously, initialize the control parameters of the iteration process, including the current iteration counter, the error decision threshold, and the preset maximum number of iterations; S2. Preprocess the initial signal; S3. Perform amplitude constraint operation on the preprocessed signal using the amplitude information of the signal with added dispersion; S4. Implement a dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal; S5. Calculate the amplitude error between the signal without added dispersion and the initial signal; combine the intensity of the dual-polarized signal to be measured and the phase information of the phase signal to obtain the phase reconstruction signal; S6. Iteratively optimize the phase reconstruction signal to obtain the final phase reconstruction signal.

[0042] Example 2 More specifically, in one embodiment, in step S1, an initial signal is constructed by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion. The specific steps are as follows: Presetting a polarization rotation matrix parameter α for polarization multiplexing and polarization demultiplexing; parameter α is set as follows:

[0043] Where n represents the total number of values ​​for the polarization rotation matrix parameter α; the larger the value of n, the more accurate the estimation of the polarization rotation matrix. The root mean square values ​​of the undispersed signals in the two polarization states are calculated respectively to obtain the initial signal amplitude. The same root mean square calculation is performed on the signal with added dispersion to obtain the amplitude. in, This will be used to set the strength of the initial signal, while This reserves signal amplitude constraints for subsequent steps; A randomly selected initial phase is assigned to each of the two polarization states of the undispersed dual-polarization signal under test, serving as the starting point for signal processing:

[0044]

[0045] in As the initial signal, The initial phase is randomly selected, and j is the imaginary unit; at the same time, the current iteration counter is set to i = 0.

[0046] In one specific embodiment, step S2 involves preprocessing the initial signal, specifically by compensating for the dispersion effect accumulated during the transmission of the initial signal through the optical fiber; the amount of dispersion compensated is denoted as , which matches the total amount of dispersion introduced by the optical fiber; the time-domain expression of the compensation process is as follows:

[0047] Among them, Z CD The initial signal represents the transmission distance when dispersion compensation is implemented in the optical fiber link; t represents the signal propagation time; D represents the dispersion coefficient, which quantifies the degree of optical pulse broadening in the optical fiber; λ represents the wavelength of the signal, which relates to the propagation characteristics of light in the medium; c represents the speed of light; for the initial signal... The process of performing dispersion compensation is represented as follows:

[0048]

[0049] Among them, the compensated signal Due to its amplitude and phase Composition, in which This represents the signal amplitude after fiber dispersion compensation, while Represents the corresponding signal phase; The dispersion-compensated signal is polarization demultiplexed according to the preset polarization rotation matrix parameter α, and the estimated polarization rotation matrix is ​​as follows:

[0050] The depolarization multiplexing is implemented as the inverse matrix function of the polarization rotation matrix estimated by signal convolution; the current parameter takes values ​​k times, and the dual-polarization signals before depolarization are represented as follows: Then the demultiplexed signal S′ x (t), S′ y (t) Specifically:

[0051]

[0052] The signal is processed in the frequency domain using a root-raised cosine filter to achieve spectral constraint. Using a signal generated from mapping independent data sequences, pilot replacement is performed on the signal at specific positions according to a predetermined proportion of pilot symbols, thereby achieving pilot constraint in the time domain. The pilot-constrained signal is then processed again using a root-raised cosine filter for spectral constraint. Finally, the polarization rotation matrix is ​​convolved with the pilot-constrained signal for polarization multiplexing.

[0053]

[0054] Additional dispersion is applied to the signal after the second spectral constraint; the total dispersion is CD + CD. add Where CD is the dispersion introduced into the signal during transmission through the optical fiber link, and CD add This refers to the additional dispersion amount; the temporal impulse response of the dispersion addition operation is specifically as follows:

[0055] in, This represents the transmission distance when dispersion addition is applied in the fiber optic link; The preprocessed signal is obtained:

[0056]

[0057] in, This indicates a pre-processed signal. This indicates the amplitude of the preprocessed signal. This indicates the phase of the preprocessed signal.

[0058] In one specific embodiment, step S3 involves using the amplitude information of the signal with added dispersion to perform an amplitude constraint operation on the preprocessed signal. Specifically, this involves: performing amplitude constraints on the preprocessed signal based on the amplitude information of the signal with added dispersion, and then using the constrained signal... express:

[0059]

[0060] In one specific embodiment, step S4 involves implementing a dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal. Specifically, the steps are as follows: Implementing a dispersion compensation algorithm on the amplitude-constrained signal R′0(t) to obtain the phase information of the compensated phase signal.

[0061]

[0062] Where R x (t), R y (t) is the phase signal. The amplitude of the phase signal after dispersion compensation. This is the phase of the signal at this point; by extracting the compensated signal R... x (t), R y The phase angle of (t) is used to obtain the phase information of the signal:

[0063]

[0064] In one specific embodiment, step S5 involves calculating the amplitude error between the undispersed signal and the initial signal; combining the intensity of the dual-polarized signal to be measured and the phase information of the phase signal to obtain the phase reconstructed signal. Specifically, this involves quantifying the amplitude difference between the dual-polarized signal to be measured and the phase signal to evaluate the magnitude of the error between them.

[0065] a x (t) represents the dual-polarized signal to be measured without added additional dispersion, A error This represents the calculated amplitude error, which is within a set time window T. error Measurements are performed internally; based on the amplitude of the test signal and the phase information of the phase signal, a phase reconstruction signal is obtained:

[0066]

[0067] in, The obtained phase reconstruction signal.

[0068] In one specific embodiment, step S6 involves iteratively optimizing the final signal to obtain the final phase reconstruction signal. The specific steps are: checking whether the current iteration number i has reached the preset maximum iteration number I. max If the current iteration number i equals I max Once all iterations are complete, the algorithm will output the final phase reconstruction signal S.output (t); if not equal to I max This indicates that the algorithm has not yet completed all the predetermined iterations, so the magnitude error A is calculated. error With the preset decision threshold ε TH Comparison between them; if the amplitude error A error Less than or equal to the decision threshold ε TH A error ≤ε TH If the amplitude error A is not reached, the algorithm terminates and outputs the final signal; if the amplitude error A is not reached, the algorithm terminates and outputs the final signal. error Greater than the decision threshold ε TH A error >ε TH If the phase of the initial signal is updated to the phase of the phase reconstructed signal, the value of the iteration counter i is incremented, and the iteration returns to step S2 for further iteration.

[0069] In one specific embodiment, after obtaining the final phase reconstruction signal, the bit error rate (BER) of the final phase reconstruction signal is calculated. Based on the BER, the value of α is approximated, and the accurate phase reconstruction signal is confirmed. The specific steps are as follows: Determine the current number of times k of the polarization rotation matrix parameter α is taken. If k < n, the current number of times the value is taken is incremented. If k < n, the current number of times the value is incremented, and the process returns to step S1 until k = n. Finally, n BER values ​​are obtained. Find the minimum value among the n sets of BER data and use it as the α value in the polarization rotation matrix. Based on the α value, the accurate phase reconstruction signal is confirmed.

[0070] Example 3: A phase reconstruction system for dual-polarization signals based on fully blind polarization rotation matrix estimation, comprising a signal generation module, a signal construction module, a preprocessing module, an amplitude constraint module, a dispersion compensation module, an error decision module, an iterative optimization module, and a bit error rate calculation module. The signal generation module acquires the dual-polarization signal to be measured, which includes a signal with added dispersion and a signal without added dispersion. The signal construction module constructs an initial signal by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion. The preprocessing module preprocesses the initial signal. The amplitude constraint module performs amplitude constraint operations on the preprocessed signal using the amplitude information of the signal with added dispersion. The dispersion compensation module performs a dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal. The error decision module calculates the amplitude error between the signal without added dispersion and the initial signal; combining the intensity of the dual-polarization signal to be measured and the phase information of the phase signal, a phase reconstruction signal is obtained. The iterative optimization module iteratively optimizes the phase reconstruction signal to obtain the final phase reconstruction signal.

[0071] As shown in Figure 2, the signal generation module includes a transmitter and a receiver. The transmitter includes a laser, an I / Q modulator, and a digital-to-analog converter (DAC). The receiver includes a polarization beamsplitter, an optical splitter, a dispersion element, a photodetector, and an analog-to-digital converter (ADC). The transmitter and receiver are connected via an optical fiber transmission link. The laser generates a stable optical signal. The I / Q modulator performs electro-optical conversion on the optical signal to achieve signal modulation. The DAC converts the digital signal into the analog signal required for modulation during this process. In this embodiment, the I / Q modulator is specifically a dual-polarization I / Q modulator. The DAC is a 4-channel DAC. The polarization beamsplitter separates the received optical signal into two orthogonally polarized output beams. The photodetector converts the optical signal into an electrical signal, capturing the intensity information of the two signals. The dispersion element introduces additional dispersion into one of the signals to facilitate phase reconstruction. The DAC converts the analog electrical signal into a digital signal, providing data for subsequent digital signal processing.

[0072] In this embodiment, the received optical signal is separated into two output signal beams S with orthogonal polarization states by a polarization beam splitter. x (t), S y (t) after which the output signal beam S is further... x (t), S y (t) is divided into two beams. One of the signals is dispersive and output as a dispersive signal through an analog-to-digital converter. The other signal is undispersive and output as an undispersive signal through an analog-to-digital converter. The phase of the two polarization states of the signal beams is reconstructed respectively.

[0073] In this embodiment, the signal is transmitted through an 80-kilometer standard single-mode fiber in the optical fiber transmission link, passing through an erbium-doped fiber amplifier along the way. The function of this amplifier is to compensate for energy loss during signal transmission in the optical fiber, ensuring that the signal maintains sufficient strength after long-distance transmission.

[0074] In this embodiment, the present invention employs phase reconstruction technology and vibration multiplexing (PDM) technology based on signal strength information.

[0075] Among them, phase reconstruction technology transmits quadrature amplitude modulation (QAM) signals at the transmitting end and performs direct detection at the receiving end, providing a potential solution for high-speed optical interconnects.

[0076] Polarization multiplexing (PDM) technology can double the transmission capacity of a single-polarization optical transmission system. In carrier-assisted direct probe phase reconstruction receivers, the optical carrier undergoes random polarization rotation due to the transmission characteristics of the fiber optic link. When the polarization beam splitter (PBS) at the receiver processes these rotated optical carriers, it may lose one of the orthogonal polarization states, thus failing to recover the polarization state signal information from the signal. This phenomenon is called polarization fading. In contrast, dual-polarization carrierless phase reconstruction receivers obtain the intensity information of the two signals through two photodetectors and an additional dispersive element, and then use the GS iterative algorithm to reconstruct the phase of the signal, ultimately recovering the orthogonal amplitude modulated signal. Since it is not necessary to generate an optical carrier at the transmitter, this method can theoretically effectively avoid the problem of polarization fading.

[0077] 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. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for phase reconstruction of dual-polarization signals based on fully blind polarization rotation matrix estimation, characterized in that: The specific steps include the following: S1. Obtain the dual-polarization signal to be tested, which includes a signal with added dispersion and a signal without added dispersion; construct an initial signal by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion. S2, Preprocess the initial signal; S3. Using the amplitude information of the signal with added dispersion, perform amplitude constraint operation on the preprocessed signal; S4. Apply a dispersion compensation algorithm to the amplitude-constrained signal to obtain the phase information of the compensated phase signal; S5. Calculate the amplitude error between the undispersed signal and the initial signal; combine the intensity of the dual-polarized signal to be measured and the phase information of the phase signal to obtain the phase reconstructed signal; S6. Iteratively optimize the phase reconstruction signal to obtain the final phase reconstruction signal.

2. The dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to claim 1, characterized in that: In step S1, an initial signal is constructed by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion. The specific steps are as follows: A polarization rotation matrix parameter α is preset for polarization multiplexing and polarization demultiplexing; parameter α is set as follows: Where n is the total number of values ​​of the polarization rotation matrix parameter α. The larger the value of n, the more accurate the estimation of the polarization rotation matrix. Calculate the root mean square values ​​of the undispersed signals in both polarization states to obtain the initial signal amplitude. The same root mean square calculation is performed on the signal with added dispersion to obtain the amplitude. in, This will be used to set the strength of the initial signal, while This reserves the signal amplitude constraint for subsequent steps; A randomly selected initial phase is assigned to each of the two polarization states of the undispersed dual-polarization signal under test, and this serves as the starting point for signal processing: in As the initial signal, The initial phase is randomly selected, and j is the imaginary unit; at the same time, the current iteration counter is set to i = 0.

3. The dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to claim 2, characterized in that: In step S2, the initial signal is preprocessed, and the specific steps are as follows: The dispersion effect accumulated during the transmission of the initial signal in the optical fiber is compensated; the amount of dispersion compensated is denoted as , which matches the total amount of dispersion introduced by the optical fiber; the time-domain expression of the compensation process is as follows: Among them, Z CD λ represents the transmission distance when dispersion compensation is implemented in the optical fiber link; t represents the signal propagation time; D represents the dispersion coefficient, which quantifies the degree of optical pulse broadening in the optical fiber; λ represents the wavelength of the signal, which is related to the propagation characteristics of light in the medium; and c represents the speed of light. For the initial signal The process of performing dispersion compensation is represented as follows: Among them, the compensated signal Due to its amplitude and phase Composition, in which This represents the signal amplitude after fiber dispersion compensation, while Represents the corresponding signal phase; The polarization demultiplexing is performed on the dispersion-compensated signal based on the preset polarization rotation matrix parameter α. The estimated polarization rotation matrix is ​​as follows: The depolarization multiplexing is implemented as the inverse matrix function of the polarization rotation matrix estimated by signal convolution; the current parameter takes values ​​k times, and the dual-polarization signals before depolarization are represented as follows: Then the demultiplexed signal S′ x (t), S′ y (t) Specifically: The signal is processed in the frequency domain through a root-raised cosine filter to achieve spectral constraint; By using signals generated from independent data sequence mappings, pilot replacement is performed on signals at specific locations according to a predetermined proportion of pilot symbols, thereby constraining the signals in the time domain. The pilot-constrained signal is then processed again by a root-raised cosine filter for spectral constraint. The polarization rotation matrix is ​​convolved with the pilot-constrained signal to perform polarization multiplexing: Additional dispersion is applied to the signal after the second spectral constraint; the total dispersion is CD + CD. add Where CD is the dispersion introduced into the signal during transmission through the optical fiber link, and CD add This refers to the additional dispersion amount; the temporal impulse response of the dispersion addition operation is specifically as follows: in, This indicates the transmission distance when dispersion addition is implemented in an optical fiber link; Obtain the preprocessed signal: in, This indicates a pre-processed signal. This indicates the amplitude of the preprocessed signal. This indicates the phase of the preprocessed signal.

4. The dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to claim 3, characterized in that: In step S3, the amplitude information of the signal with added dispersion is used to perform an amplitude constraint operation on the preprocessed signal. The specific steps are as follows: Based on the amplitude information of the signal with added dispersion, amplitude constraints are applied to the preprocessed signal, and the constrained signal is then used... express:

5. The dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to claim 4, characterized in that: In step S4, a dispersion compensation algorithm is applied to the amplitude-constrained signal to obtain the phase information of the compensated phase signal. The specific steps are as follows: A dispersion compensation algorithm is applied to the amplitude-constrained signal R′0(t) to obtain the phase information of the compensated phase signal: Where R x (t), R y (t) is the phase signal. The amplitude of the phase signal after dispersion compensation. This refers to the phase of the signal at this time; By extracting the compensated signal R x (t), R y The phase angle of (t) is used to obtain the phase information of the signal:

6. The dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to claim 4, characterized in that: In step S5, the amplitude error between the undispersed signal and the initial signal is calculated; by combining the intensity of the dual-polarized signal to be measured and the phase information of the phase signal, the phase reconstruction signal is obtained. The specific steps are as follows: The amplitude difference between the tested dual-polarization signal and phase signal is quantitatively analyzed to assess the magnitude of the error between them. a x (t) represents the dual-polarized signal to be measured without added additional dispersion, A error This represents the calculated amplitude error, which is within a set time window T. error The measurements were taken inside; Based on the amplitude of the test signal and the phase information of the phase signal, the phase reconstructed signal is obtained: in, The obtained phase reconstruction signal.

7. The dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to claim 6, characterized in that: In step S6, the final signal is iteratively optimized to obtain the final phase reconstruction signal. The specific steps are as follows: Check if the current iteration number i has reached the preset maximum iteration number I. max If the current iteration number i equals I max Once all iterations are complete, the algorithm will output the final phase reconstruction signal S. output (t); If not equal to I max This indicates that the algorithm has not yet completed all the predetermined iterations, so the magnitude error A is calculated. error With the preset decision threshold ε TH Comparison between them; if the amplitude error A error Less than or equal to the decision threshold ε TH A error ≤ε TH If the amplitude error A is not reached, the algorithm terminates and outputs the final signal; if the amplitude error A is not reached, the algorithm terminates and outputs the final signal. error Greater than the decision threshold ε TH A error >ε TH If the phase of the initial signal is updated to the phase of the phase reconstructed signal, the value of the iteration counter i is incremented, and the iteration returns to step S2 for further iteration.

8. The dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to claim 7, characterized in that: After obtaining the final phase reconstructed signal, the bit error rate (BER) is calculated. Based on the BER, the value of α is approximated, and the accurate phase reconstructed signal is confirmed. The specific steps are as follows: Determine the current number of times the polarization rotation matrix parameter α is taken, k. If k < n, the current number of times is incremented. If k < n, the current number of times is incremented and the process returns to step S1 until k = n. Finally, n bit error rate values ​​are obtained. Find the minimum value among the n sets of BER data and use it as the α value in the polarization rotation matrix. Based on the α value, confirm the accurate phase reconstruction signal.

9. A phase reconstruction system for dual-polarization signals based on fully blind polarization rotation matrix estimation, characterized in that: It includes a signal generation module, a signal construction module, a preprocessing module, an amplitude constraint module, a dispersion compensation module, an error decision module, an iterative optimization module, and a bit error rate calculation module; The signal generation module is used to acquire the dual-polarized signal to be tested, which includes a signal with added dispersion and a signal without added dispersion; The signal construction module is used to construct an initial signal by presetting a polarization rotation matrix parameter α and setting an initial phase value for the signal without added dispersion; The preprocessing module is used to preprocess the initial signal; The amplitude constraint module is used to perform amplitude constraint operations on the preprocessed signal using the amplitude information of the signal with added dispersion. The dispersion compensation module is used to perform a dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal; The error decision module is used to calculate the amplitude error between the undispersed signal and the initial signal; and to obtain the phase reconstructed signal by combining the intensity of the dual-polarized signal to be measured and the phase information of the phase signal. The iterative optimization module is used to iteratively optimize the phase reconstruction signal to obtain the final phase reconstruction signal.

10. The dual-polarization signal phase reconstruction system based on fully blind polarization rotation matrix estimation according to claim 9, characterized in that: The signal generation module includes a transmitter and a receiver; the transmitter includes a laser, an I / Q modulator, and a digital-to-analog converter; the receiver includes a polarization beam splitter, an optical splitter, a dispersive element, a photodetector, and an analog-to-digital converter. The transmitter and receiver are connected via an optical fiber transmission link; The laser is used to generate optical signals; the I / Q modulator is used to perform electro-optic conversion; and the digital-to-analog converter is used to convert digital signals into analog signals. The polarization beam splitter is used to separate the received optical signal into two output beams with orthogonal polarization states; the photodetector is used to convert the optical signal into an electrical signal; the dispersive element is used to introduce additional dispersion into one of the signals; and the analog-to-digital converter is used to convert the analog electrical signal into a digital signal.

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