A method and system for reconstructing the phase of a dual-polarized signal based on a full-blind polarization rotation matrix estimation

Abstract

The application relates to the technical field of optical fiber communication, and discloses a double-polarization signal phase reconstruction method and system based on full-blind polarization rotation matrix estimation, which comprises the following specific steps: obtaining a double-polarization signal to be measured; presetting a polarization rotation matrix parameter, and constructing an initial signal; preprocessing the initial signal; performing an amplitude constraint operation on the preprocessed signal; implementing a dispersion compensation algorithm on the amplitude-constrained signal to obtain phase information of the compensated phase signal; calculating an amplitude error between the signal without added dispersion and the initial signal; combining the intensity of the double-polarization signal to be measured and the phase information of the phase signal to obtain a phase reconstruction signal; iteratively optimizing the phase reconstruction signal to obtain a final phase reconstruction signal; and performing bit error rate calculation to approximately obtain a value. The application solves the problem of low phase reconstruction precision caused by polarization rotation in the prior art, and has the characteristics of being capable of effectively avoiding polarization fading.

Description

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 (CWDM) 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 objectives of this invention, the technical solution adopted is as follows:

[0007] A phase reconstruction method for dual-polarization signals based on fully blind polarization rotation matrix estimation includes the following specific steps:

[0008] S1. Obtain the dual-polarized signal to be tested, wherein the dual-polarized signal includes a signal with added dispersion and a signal without added dispersion; by presetting a polarization rotation matrix parameter. An initial phase value is set for the signal without added dispersion to construct the initial signal;

[0009] S2. Preprocess the initial signal;

[0010] S3. Using the amplitude information of the signal with added dispersion, perform amplitude constraint operation on the preprocessed signal;

[0011] S4. Apply a dispersion compensation algorithm to the amplitude-constrained signal to obtain the phase information of the compensated phase signal;

[0012] 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;

[0013] S6. Iteratively optimize the phase reconstruction signal to obtain the final phase reconstruction signal.

[0014] Preferably, in step S1, a polarization rotation matrix parameter is preset. An initial phase value is set for the signal without added dispersion to construct the initial signal. The specific steps are as follows:

[0015] Preset a polarization rotation matrix parameter Used for polarization multiplexing and polarization demultiplexing; parameters Set to:

[0016]

[0017] in, Polarization rotation matrix parameters The total number of values ​​that can be taken, if The larger the value of , the more accurate the estimation of the polarization rotation matrix;

[0018] Calculate the root mean square values ​​of the undispersed signals in both polarization states to obtain the initial signal amplitude. , And perform the same root mean square calculation 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;

[0019] 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:

[0020]

[0021]

[0022] in , As the initial signal, , The initial phase is randomly selected. The imaginary unit is used; simultaneously, the current iteration counter is set to... .

[0023] Furthermore, in step S2, the initial signal is preprocessed, specifically through the following steps:

[0024] The dispersion effect accumulated during the transmission of the initial signal in the optical fiber is compensated; the amount of compensation dispersion is denoted as φ, which matches the total amount of dispersion introduced by the optical fiber; the time-domain expression of the compensation process is as follows:

[0025]

[0026] in, This indicates the transmission distance when dispersion compensation is implemented in the optical fiber link; Indicates the time it takes for the signal to propagate; It represents the dispersion coefficient, which quantifies the degree of pulse broadening in an optical fiber; The wavelength of the signal is related to the propagation characteristics of light in a medium; Represents the speed of light;

[0027] For the initial signal , The process of performing dispersion compensation is represented as follows:

[0028]

[0029]

[0030] 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;

[0031] According to the preset polarization rotation matrix parameters The polarization demultiplexing of the dispersion-compensated signal yields the estimated polarization rotation matrix as follows:

[0032]

[0033] The depolarization multiplexing is implemented as the inverse matrix function of the polarization rotation matrix estimated by signal convolution; the current parameter takes values ​​a number of times. The dual-polarization signals before polarization demultiplexing are represented as follows: , Then the demultiplexed signal , Specifically:

[0034]

[0035]

[0036] The signal is processed in the frequency domain through a root-raised cosine filter to achieve spectral constraint;

[0037] 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.

[0038] The pilot-constrained signal is then processed again by a root-raised cosine filter for spectral constraint.

[0039] The polarization rotation matrix is ​​convolved with the pilot-constrained signal to perform polarization multiplexing:

[0040]

[0041]

[0042] Additional dispersion is applied to the signal after the second spectral constraint; the total dispersion is ,in This refers to the dispersion introduced into the signal during transmission through the optical fiber link. This refers to the additional dispersion amount; the temporal impulse response of the dispersion addition operation is specifically as follows:

[0043]

[0044] in, This indicates the transmission distance when dispersion addition is implemented in an optical fiber link;

[0045] Obtain the preprocessed signal:

[0046]

[0047]

[0048] in, , This indicates a pre-processed signal. , This indicates the amplitude of the preprocessed signal. , This indicates the phase of the preprocessed signal.

[0049] 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. The specific steps are as follows:

[0050] 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:

[0051]

[0052] .

[0053] 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. The specific steps are as follows:

[0054] For amplitude-constrained signals By implementing a dispersion compensation algorithm, the phase information of the compensated phase signal is obtained:

[0055]

[0056]

[0057] in , It is a phase signal. , The amplitude of the phase signal after dispersion compensation. , This refers to the phase of the signal at this time;

[0058] By extracting the compensated signal , The phase angle is used to obtain the phase information of the signal:

[0059]

[0060] .

[0061] Furthermore, in step S5, the amplitude error between the signal without added dispersion and the initial signal is calculated; 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 specific steps are as follows:

[0062] The amplitude difference between the tested dual-polarization signal and phase signal is quantitatively analyzed to assess the magnitude of the error between them.

[0063]

[0064] The dual-polarized signal to be measured is without added additional dispersion. This represents the calculated amplitude error, which is within a set time window. The measurements were taken inside;

[0065] Based on the amplitude of the test signal and the phase information of the phase signal, the phase reconstructed signal is obtained:

[0066]

[0067]

[0068] in, , The obtained phase reconstruction signal.

[0069] Furthermore, in step S6, the final signal is iteratively optimized to obtain the final phase reconstruction signal. The specific steps are as follows:

[0070] Check the current iteration number Has the preset maximum number of iterations been reached? If the current iteration number equal Once all iterations are complete, the algorithm will output the final phase reconstruction signal. ;

[0071] If not equal to This indicates that the algorithm has not yet completed all the predetermined iterations, so magnitude error is calculated. Compared with the preset decision threshold Comparison between them; if the amplitude error Less than or equal to the decision threshold ,Right now If the amplitude error is reached, the algorithm terminates and outputs the final signal; if the amplitude error is reached... Greater than the decision threshold ,Right now Then, the phase of the initial signal is updated to the phase of the phase reconstructed signal, and the iteration counter is incremented. The value is then returned to step S2 for iteration.

[0072] Furthermore, after obtaining the final phase reconstructed signal, the bit error rate (BER) is calculated on the final phase reconstructed signal, and an approximation is obtained based on the BER. The specific steps for determining the value and confirming the accurate phase reconstruction signal are as follows:

[0073] Determine the parameters of the polarization rotation matrix The current number of times ,like If the current value is taken repeatedly, then the number of times the value is taken will increase. If the current value is incremented, return to step S1 until... Finally, it was concluded that The bit error rate value; find The minimum value in the BER dataset is used as the value in the polarization rotation matrix. Value, based on The value confirms the accurate phase reconstruction signal.

[0074] A phase reconstruction system for dual-polarization 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.

[0075] 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;

[0076] The signal construction module is used to preset a polarization rotation matrix parameter. An initial phase value is set for the signal without added dispersion to construct the initial signal;

[0077] The preprocessing module is used to preprocess the initial signal;

[0078] 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.

[0079] 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;

[0080] 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.

[0081] The iterative optimization module is used to iteratively optimize the phase reconstruction signal to obtain the final phase reconstruction signal.

[0082] 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 dispersive element, a photodetector, and an analog-to-digital converter; the transmitter and receiver are connected via an optical fiber transmission link.

[0083] 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.

[0084] 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.

[0085] The beneficial effects of this invention are as follows:

[0086] This invention employs phase reconstruction and polarization multiplexing techniques based on signal intensity information. By utilizing the amplitude information of the signal with added dispersion, it performs amplitude constraint operations on the preprocessed signal, applies a dispersion compensation algorithm to the amplitude-constrained signal, and calculates the amplitude error between the undispersioned signal and the initial signal. This is combined with the intensity of the dual-polarized signal under test 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 effectively avoids polarization fading. Attached Figure Description

[0087] Figure 1 This is a flowchart illustrating a dual-polarization signal phase reconstruction method based on fully blind polarization rotation matrix estimation according to the present invention.

[0088] Figure 2 This 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

[0089] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0090] Example 1

[0091] like Figure 1 As shown, a phase reconstruction method for dual-polarization signals based on fully blind polarization rotation matrix estimation includes the following specific steps:

[0092] S1. Obtain the dual-polarized signal to be tested, wherein the dual-polarized signal includes a signal with added dispersion and a signal without added dispersion; by presetting a polarization rotation matrix parameter. An initial phase value is set for the signal without added dispersion to construct the initial signal; at the same time, the control parameters of the iteration process are initialized, including the current iteration counter, the error decision threshold, and the preset maximum number of iterations.

[0093] S2. Preprocess the initial signal;

[0094] S3. Using the amplitude information of the signal with added dispersion, perform amplitude constraint operation on the preprocessed signal;

[0095] S4. Apply a dispersion compensation algorithm to the amplitude-constrained signal to obtain the phase information of the compensated phase signal;

[0096] 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;

[0097] S6. Iteratively optimize the phase reconstruction signal to obtain the final phase reconstruction signal.

[0098] Example 2

[0099] More specifically, in one embodiment, in step S1, a polarization rotation matrix parameter is preset. An initial phase value is set for the signal without added dispersion to construct the initial signal. The specific steps are as follows:

[0100] Preset a polarization rotation matrix parameter Used for polarization multiplexing and polarization demultiplexing; parameters Set to:

[0101]

[0102] in, Polarization rotation matrix parameters The total number of values ​​that can be taken, if The larger the value of , the more accurate the estimation of the polarization rotation matrix;

[0103] Calculate the root mean square values ​​of the undispersed signals in both polarization states to obtain the initial signal amplitude. , And perform the same root mean square calculation 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;

[0104] 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:

[0105]

[0106]

[0107] in , As the initial signal, , The initial phase is randomly selected. The imaginary unit is used; simultaneously, the current iteration counter is set to... .

[0108] In one specific embodiment, step S2 involves preprocessing the initial signal, specifically as follows:

[0109] The dispersion effect accumulated during the transmission of the initial signal in the optical fiber is compensated; the amount of compensation dispersion is denoted as φ, which matches the total amount of dispersion introduced by the optical fiber; the time-domain expression of the compensation process is as follows:

[0110]

[0111] in, This indicates the transmission distance when dispersion compensation is implemented in the optical fiber link; Indicates the time it takes for the signal to propagate; It represents the dispersion coefficient, which quantifies the degree of pulse broadening in an optical fiber; The wavelength of the signal is related to the propagation characteristics of light in a medium; Represents the speed of light;

[0112] For the initial signal , The process of performing dispersion compensation is represented as follows:

[0113]

[0114]

[0115] 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;

[0116] According to the preset polarization rotation matrix parameters The polarization demultiplexing of the dispersion-compensated signal yields the estimated polarization rotation matrix as follows:

[0117]

[0118] The depolarization multiplexing is implemented as the inverse matrix function of the polarization rotation matrix estimated by signal convolution; the current parameter takes values ​​a number of times. The dual-polarization signals before polarization demultiplexing are represented as follows: , Then the demultiplexed signal , Specifically:

[0119]

[0120]

[0121] The signal is processed in the frequency domain through a root-raised cosine filter to achieve spectral constraint;

[0122] 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.

[0123] The pilot-constrained signal is then processed again by a root-raised cosine filter for spectral constraint.

[0124] The polarization rotation matrix is ​​convolved with the pilot-constrained signal to perform polarization multiplexing:

[0125]

[0126]

[0127] Additional dispersion is applied to the signal after the second spectral constraint; the total dispersion is ,in This refers to the dispersion introduced into the signal during transmission through the optical fiber link. This refers to the additional dispersion amount; the temporal impulse response of the dispersion addition operation is specifically as follows:

[0128]

[0129] in, This indicates the transmission distance when dispersion addition is implemented in an optical fiber link;

[0130] Obtain the preprocessed signal:

[0131]

[0132]

[0133] in, , This indicates a pre-processed signal. , This indicates the amplitude of the preprocessed signal. , This indicates the phase of the preprocessed signal.

[0134] 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. The specific steps are as follows:

[0135] 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:

[0136]

[0137] .

[0138] In one specific embodiment, step S4 involves performing a dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal. The specific steps are as follows:

[0139] For amplitude-constrained signals By implementing a dispersion compensation algorithm, the phase information of the compensated phase signal is obtained:

[0140]

[0141]

[0142] in , It is a phase signal. , The amplitude of the phase signal after dispersion compensation. , This refers to the phase of the signal at this time;

[0143] By extracting the compensated signal , The phase angle is used to obtain the phase information of the signal:

[0144]

[0145] .

[0146] 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-polarization signal to be measured and the phase information of the phase signal to obtain the phase reconstruction signal. The specific steps are as follows:

[0147] The amplitude difference between the tested dual-polarization signal and phase signal is quantitatively analyzed to assess the magnitude of the error between them.

[0148]

[0149] The dual-polarized signal to be measured is without added additional dispersion. This represents the calculated amplitude error, which is within a set time window. The measurements were taken inside;

[0150] Based on the amplitude of the test signal and the phase information of the phase signal, the phase reconstructed signal is obtained:

[0151]

[0152]

[0153] in, , The obtained phase reconstruction signal.

[0154] In one specific embodiment, step S6 involves iteratively optimizing the final signal to obtain the final phase reconstruction signal. The specific steps are as follows:

[0155] Check the current iteration number Has the preset maximum number of iterations been reached? If the current iteration number equal Once all iterations are complete, the algorithm will output the final phase reconstruction signal. ;

[0156] If not equal to This indicates that the algorithm has not yet completed all the predetermined iterations, so magnitude error is calculated. Compared with the preset decision threshold Comparison between them; if the amplitude error Less than or equal to the decision threshold ,Right now If the amplitude error is reached, the algorithm terminates and outputs the final signal; if the amplitude error is reached... Greater than the decision threshold ,Right now Then, the phase of the initial signal is updated to the phase of the phase reconstructed signal, and the iteration counter is incremented. The value is then returned to step S2 for iteration.

[0157] In one specific embodiment, after obtaining the final phase reconstructed signal, the bit error rate (BER) is calculated on the final phase reconstructed signal, and an approximation of the BER is obtained. The specific steps for determining the value and confirming the accurate phase reconstruction signal are as follows:

[0158] Determine the parameters of the polarization rotation matrix The current number of times ,like If the current value is taken repeatedly, then the number of times the value is taken will increase. If the current value is incremented, return to step S1 until... Finally, it was concluded that The bit error rate value; find The minimum value in the BER dataset is used as the value in the polarization rotation matrix. Value, based on The value confirms the accurate phase reconstruction signal.

[0159] Example 3

[0160] A phase reconstruction system for dual-polarization 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.

[0161] 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;

[0162] The signal construction module is used to preset a polarization rotation matrix parameter. An initial phase value is set for the signal without added dispersion to construct the initial signal;

[0163] The preprocessing module is used to preprocess the initial signal;

[0164] 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.

[0165] 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;

[0166] 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.

[0167] The iterative optimization module is used to iteratively optimize the phase reconstruction signal to obtain the final phase reconstruction signal.

[0168] like Figure 2 As shown, 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 by an optical fiber transmission link.

[0169] The laser is used to generate a stable optical signal; the I / Q modulator is used to perform electro-optic conversion on the optical signal to achieve signal modulation; the digital-to-analog converter is used to convert the digital signal into the analog signal required for modulation in this process.

[0170] In this embodiment, the I / Q modulator is specifically a dual-polarization I / Q modulator; the digital-to-analog converter is a 4-channel digital-to-analog converter (DAC).

[0171] 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 and capture the intensity information of the two signals; the dispersive element is used to introduce additional dispersion into one of the signals to facilitate phase reconstruction of the signal; the analog-to-digital converter is used to convert the analog electrical signal into a digital signal to provide data for subsequent digital signal processing.

[0172] In this embodiment, a polarization beam splitter separates the received optical signal into two output signal beams with orthogonal polarization states. , Then, the output signal beam is further... , The signal is divided into two beams. One beam is dispersive and output as a dispersive signal through an analog-to-digital converter, while the other beam is undispersive and output as an undispersive signal through the same converter. The phase of the two polarization states of the signal beams is then reconstructed.

[0173] 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.

[0174] In this embodiment, the present invention employs phase reconstruction technology and vibration multiplexing (PDM) technology based on signal strength information.

[0175] 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.

[0176] 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 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.

[0177] 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 full-blind polarization rotation matrix estimation, characterized in that: The method comprises the following specific steps: S1, obtaining a double polarization signal to be measured, the double polarization signal including a signal with added dispersion and a signal without added dispersion; a preset polarization rotation matrix parameter is used , and an initial phase value is set for the signal without added dispersion to construct an initial signal; The preset 1 polarization rotation matrix parameter And set an initial phase value for the signal without adding dispersion, construct an initial signal, the specific steps are: A polarization rotation matrix parameter is preset for polarization multiplexing and polarization demultiplexing is set as wherein, is a polarization rotation matrix parameter the total number of values of the greater the value of the more accurate the estimation of the polarization rotation matrix. The root mean square values of the signals without added dispersion are calculated for both polarization states to obtain initial signal amplitudes , The same root mean square calculations are performed for the signals with added dispersion to obtain amplitudes , ; where , The initial signal strengths are used to set the initial signal amplitudes, while , The signal amplitude constraints for the subsequent steps are reserved. An initial phase is given to the to-be-detected dual-polarization signal without additional dispersion for two polarization states, which is used as the starting signal for processing; wherein , is an initial signal, , is a randomly selected initial phase, is the imaginary unit; and setting the current iteration counter to ; S2, preprocessing the initial signal; S3, performing amplitude constraint operation on the preprocessed signal by using the amplitude information of the signal with added dispersion; S4, performing dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal; S5, calculating the amplitude error between the signal without added dispersion and the initial signal; combining the intensity of the to-be-detected dual-polarization signal and the phase information of the phase signal to obtain a phase reconstruction signal; S6, iteratively optimizing the phase reconstruction signal to obtain a final phase reconstruction signal.

2. The method of claim 1, wherein the method is based on the estimation of the full-blind polarization rotation matrix. In the step S2, the initial signal is preprocessed, and the specific steps are as follows: The dispersion effect accumulated in the process of optical fiber transmission of the initial signal is compensated; the compensated dispersion amount is denoted as CD, which matches the total dispersion introduced by the optical fiber; the time-domain expression of the compensation process is specifically as follows: wherein, denotes the transmission distance when implementing dispersion compensation in the fiber link; denotes the time of signal propagation; denotes the dispersion coefficient, which quantifies the degree of optical pulse broadening in the fiber; denotes the wavelength of the signal, which is related to the propagation characteristics of light in the medium; denotes the speed of light; The initial signal , The process of dispersion compensation is represented by: wherein the compensated signal , is composed of its amplitude , and phase , wherein , denotes the amplitude of the signal compensated for fiber dispersion, and , represents the corresponding signal phase; According to the preset polarization rotation matrix parameter The polarization demultiplexing is performed on the dispersion-compensated signal, and the estimated polarization rotation matrix is specifically: The implementation of polarization demultiplexing is signal convolution with an inverse matrix function of a polarization rotation matrix estimated; the current parameter value number is , the dual polarization signals before polarization demultiplexing are respectively represented as 、 , and the signals after demultiplexing are 、 Specifically: The signal is processed by a root-raised cosine filter in the frequency domain to realize spectrum constraint; The signal generated by mapping independent data sequences is used to replace the signal at specific positions according to the predetermined proportion of pilot symbols, so as to perform pilot constraint on the signal in the time domain; The pilot-constrained signal is processed by a root-raised cosine filter again to perform spectrum constraint; The pilot-constrained signal is convolved with a polarization rotation matrix to perform polarization multiplexing: applying an additional chromatic dispersion to the signal subjected to the second spectral constraint; the total amount of chromatic dispersion being wherein Df is the amount of chromatic dispersion introduced to the signal during the transmission over the fiber link, and Dadd is the additional amount of chromatic dispersion added; the time-domain impulse response of the chromatic dispersion addition operation being specifically: wherein denotes the transmission distance when the dispersion addition is implemented in the fiber link; The preprocessed signal is obtained: wherein , denotes the pre-processed signal, , denotes the amplitude of the pre-processed signal, , denotes the phase of the pre-processed signal.

3. The method of claim 2, wherein the method is based on the estimation of the full-blind polarization rotation matrix. In the step S3, the amplitude information of the signal with added dispersion is used to perform amplitude constraint operation on the preprocessed signal, and the specific steps are as follows: Based on the amplitude information of the added dispersion signal, the amplitude constraint is performed on the preprocessed signal, and the corresponding constrained signal is represented as , denotes: 。 4. The method of claim 3, wherein the method is based on the estimation of the full-blind polarization rotation matrix. In the step S4, the dispersion compensation algorithm is performed on the amplitude-constrained signal to obtain the phase information of the compensated phase signal, and the specific steps are as follows: Signal subjected to amplitude constraint implementing a dispersion compensation algorithm to obtain phase information of the compensated phase signal wherein , is a phase signal, , is the amplitude of the phase signal after dispersion compensation, , is the phase of the signal at this time; by extracting the phase angle of the compensated signal , to obtain the phase information of the signal 。 5. The method of claim 3, wherein the method is based on the estimation of the full-blind polarization rotation matrix. In the step S5, the amplitude error between the signal without added dispersion and the initial signal is calculated; the intensity of the to-be-detected dual-polarization signal and the phase information of the phase signal are combined to obtain a phase reconstruction signal, and the specific steps are as follows: The amplitude difference between the to-be-detected dual-polarization signal and the phase signal is quantitatively analyzed to evaluate the error size therebetween: for the double polarization signal to be measured without additional dispersion added, denotes the calculated amplitude error, which is measured within a set time window ; The phase reconstruction signal is obtained according to the amplitude of the test signal and the phase information of the phase signal: wherein , is the resulting phase reconstruction signal.

6. The method of claim 5, wherein the method is based on the estimation of the full-blind polarization rotation matrix. In the step S6, the final signal is iteratively optimized to obtain a final phase reconstruction signal, and the specific steps are as follows: Check if the current iteration number has reached the preset maximum iteration number ; if the current iteration number is equal to , i.e. all iterations are completed, the algorithm will output the final phase reconstruction signal ; If not equal to , it indicates that the algorithm has not completed all scheduled iterations, then the amplitude error is compared with a preset decision threshold ; if the amplitude error is less than or equal to the decision threshold , that is , the algorithm is terminated and the finally obtained signal is output; if the amplitude error is greater than the decision threshold , that is , the phase of the initial signal is updated to the phase of the phase reconstruction signal, and the value of the iteration counter is incremented, and the iteration is returned to step S2.

7. The method of claim 6, wherein the method is based on the estimation of the full-blind polarization rotation matrix. After the final phase reconstruction signal is obtained, the final phase reconstruction signal is also subjected to bit error rate calculation, and an approximate bit error rate is obtained based on the bit error rate value, and an accurate phase reconstruction signal is confirmed, and the specific steps are as follows: Judging current value times of polarization rotation matrix parameters If , the current value times is incremented, if , the current value times is incremented, return to step S1 until , finally the value of error rate is obtained; find the minimum value in group of BER data, which is taken as the value of in the polarization rotation matrix, and the accurate phase reconstruction signal is confirmed based on the value of .​ 8.A dual-polarization signal phase reconstruction system based on full-blind polarization rotation matrix estimation, characterized in that: The method for realizing the method according to any one of claims 1-7 comprises 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 obtain a to-be-detected dual-polarization signal, and the dual-polarization signal comprises a signal with added dispersion and a signal without added dispersion; The signal construction module is used for constructing an initial signal by setting an initial phase value for the signal without adding dispersion through a preset 1 polarization rotation matrix parameter , and setting an initial phase value for the signal without adding dispersion, and constructing an initial signal. The preprocessing module is used to preprocess an initial signal; The amplitude constraint module is used to perform amplitude constraint operation on the preprocessed signal by using the amplitude information of the signal with added dispersion; The dispersion compensation module is used to perform dispersion compensation algorithm on the amplitude-constrained signal to obtain the phase information of the compensated phase signal; The error decision module is used for calculating the amplitude error between the signal without added dispersion and the initial signal; and combining the intensity of the measured dual-polarization signal and the phase information of the phase signal, a phase reconstruction signal is obtained. The iterative optimization module is used for iteratively optimizing the phase reconstruction signal to obtain a final phase reconstruction signal.

9. The dual-polarized signal phase reconstruction system based on full-blind polarization rotation matrix estimation of claim 8, wherein: The signal generation module comprises a transmitter and a receiver; the transmitter comprises a laser, an I / Q modulator and a digital-to-analog converter; the receiver comprises a polarization beam splitter, an optical splitter, a dispersion element, a photodetector and an analog-to-digital converter; The transmitter and the receiver are connected through an optical fiber transmission link; The laser is used for generating an optical signal; the I / Q modulator is used for performing electro-optical conversion; and the digital-to-analog converter is used for converting a digital signal into an analog signal; The polarization beam splitter is used for separating the received optical signal into two output beams of orthogonal polarization states; the photodetector is used for converting the optical signal into an electrical signal; the dispersion element is used for introducing additional dispersion to one of the signals; and the analog-to-digital converter is used for converting the analog electrical signal into a digital signal.

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