A blind carrier phase recovery method and system for optical fiber communication

Abstract

The application provides a blind carrier phase recovery method and system for optical fiber communication. At the sending end, first, the QAM symbol stream is grouped, and a reference pilot with a specific fixed amplitude is inserted according to the quadrant in which the first symbol of each symbol group is located. At the receiving end, after the preliminary blind carrier phase estimation is completed, the original quadrant corresponding to the reference pilot is identified by using the minimum Euclidean distance detection mechanism, and then the actual quadrant position of the pilot in the received signal is compared, so as to analyze the phase ambiguity offset with 90 degrees as the base, and accordingly, the phase correction is implemented on the corresponding symbol group. The application effectively breaks through the four-fold rotational symmetry limitation of the traditional constellation diagram by means of amplitude modulation coding, and can accurately identify and correct the fixed-angle phase deviation occurring in the blind phase recovery process. The method can significantly suppress the error code diffusion caused by the phase ambiguity, improve the transmission performance of the system in terms of the bit error rate and the generalized mutual information, and has good algorithm compatibility and engineering implementation convenience, and the system overhead is effectively controlled.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a blind carrier phase recovery method and system for optical fiber communication. Background Technology

[0002] Coherent optical communication technology is used to improve the carrying capacity, transmission range, and transmission distance of optical communication systems. However, a significant factor limiting the performance of coherent optical communication systems is the phase noise generated by the linewidth of the transmitter laser and the receiver local oscillator laser. This phase noise causes random rotation of the signal constellation points, preventing the receiver from correctly identifying the constellation diagram. This severely impacts signal quality, leading to a significant decrease in performance metrics such as Bit Error Rate (BER) and General Mutual Information (GMI). Currently, blind phase recovery algorithms for carrier phase recovery / estimation (CPR / CPE) are relatively mature, including Blind Phase Search (BPS) and Principal Component-based Phase Estimation (PCPE) algorithms. However, these blind phase recovery algorithms all suffer from phase ambiguity issues. Because coherent optical communication systems typically employ high-order quadrature amplitude modulation (QAM) technology, their constellation diagrams exhibit 90-degree symmetry. However, carrier phase retrieval algorithms cannot accurately identify the phase ambiguity caused by this 90-degree symmetry, leading to problems such as error propagation. To address these issues, a blind carrier phase retrieval method for coherent optical fiber communication systems is urgently needed to eliminate phase ambiguity, significantly reducing error propagation and phase ambiguity, and effectively improving the performance of coherent optical communication systems. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a blind carrier phase recovery method and system for optical fiber communication, so as to eliminate or improve one or more defects existing in the prior art and solve the phase ambiguity problem caused by the 90-degree symmetry of the constellation diagram during the blind phase recovery process.

[0004] One aspect of the present invention provides a blind carrier phase recovery method for a coherent optical fiber communication system to eliminate phase ambiguity, the method being performed at a receiving end, the method comprising: The receiver receives a QAM symbol sequence modulated by the transmitter. The QAM symbol sequence is divided into symbol subsequences according to a set length by the transmitter. A phase pilot is added according to the quadrant to which the first symbol in each symbol subsequence belongs. The phase pilot is matched with each of the four quadrants by mutually distinguishable fixed amplitudes. Based on a preset algorithm, carrier phase recovery is performed on the QAM symbol sequence, and the corresponding phase pilot is extracted from the symbol subsequence according to the set length. The minimum Euclidean distance criterion is used to determine the amplitude and determine the original quadrant of the first symbol in each symbol subsequence. Obtain the current quadrant of the phase pilot corresponding to each symbol subsequence in the QAM symbol sequence, compare the current quadrant of each phase pilot with the original quadrant to obtain the phase ambiguity value, and take a value between 90 degrees or an integer multiple thereof that is closest to the phase ambiguity value as the final phase ambiguity value; Phase compensation is performed on each symbol subsequence according to the corresponding final phase ambiguity value.

[0005] In some embodiments, the preset algorithm is a blind phase search algorithm.

[0006] In some embodiments, the set length for dividing the symbol subsequence is set based on the linewidth tolerance of the blind phase search algorithm, and is calculated as follows: ; in, This indicates the set length. floor Indicates rounding down to the nearest integer. This represents the sum of the linewidths of the lasers at the receiving and transmitting ends. Indicates the symbol period.

[0007] In some embodiments, the fixed amplitude of the phase pilot is an arithmetic sequence proportional to the quadrant number, and the fixed amplitude is greater than the maximum amplitude value in the QAM symbol.

[0008] In some embodiments, taking a value between 90 degrees or an integer multiple thereof that is closest to the phase blur value as the final phase blur value includes: calculating the quotient of the phase blur value divided by 90 degrees, rounding the quotient to the nearest integer, and then multiplying the resulting integer by 90 degrees, and using the calculation result as the final phase blur value.

[0009] In some embodiments, before receiving the QAM symbol sequence modulated by the transmitter, the method further includes receiving the set length published by the transmitter.

[0010] On the other hand, the present invention also provides a receiving device for eliminating phase ambiguity, the receiving device including a receiving module, a phase recovery and decoding module, an ambiguity value calculation module and a compensation module; The receiving module is used to receive a QAM symbol sequence modulated by the transmitting end. The QAM symbol sequence is divided into symbol groups by the transmitting end according to a set length, and a phase pilot is added according to the quadrant to which the first symbol in each symbol group belongs. The phase pilot is matched with the four quadrants respectively by mutually distinguishable fixed amplitudes. The phase recovery and decoding module is used to perform carrier phase recovery on the QAM symbol sequence based on a preset blind carrier phase recovery algorithm, extract the corresponding phase pilot of the symbol group according to the set length, and use the minimum Euclidean distance criterion to determine the amplitude to determine the original quadrant of the first symbol in each symbol group. The ambiguity value calculation module is used to obtain the current quadrant of the phase pilot corresponding to each symbol group in the QAM symbol sequence, compare the current quadrant of each phase pilot with the original quadrant to obtain the phase ambiguity value, and take a value between 90 degrees or an integer multiple thereof that is closest to the phase ambiguity value as the final phase ambiguity value. The compensation module is used to perform phase compensation on each symbol group according to the corresponding final phase ambiguity value.

[0011] On the other hand, the present invention also provides an optical fiber communication system for eliminating phase ambiguity, the system comprising: The transmitting device is used to divide the QAM symbol sequence to be transmitted into symbol groups according to a set length, determine the quadrant to which the first symbol in each symbol group belongs, generate a phase pilot with a corresponding fixed amplitude according to the quadrant, and insert the phase pilot before the corresponding symbol group for transmission; And the aforementioned receiver equipment for eliminating phase ambiguity.

[0012] On the other hand, the present invention also provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a processor, implement the steps of the above-described method.

[0013] On the other hand, the present invention also provides a computer program product, including a computer program or instructions that, when executed by a processor, implement the steps of the above-described method.

[0014] The blind carrier phase recovery method and system for optical fiber communication described in this invention involves the transmitter dividing a QAM symbol sequence into symbol subsequences and adding a phase pilot with a specific fixed amplitude based on the quadrant of the first symbol in each subsequence. After completing blind carrier phase recovery, the receiver determines the original quadrant of the phase pilot using the minimum Euclidean distance criterion, compares it with the current quadrant, calculates the final phase ambiguity value in the form of 90 degrees or integer multiples thereof, and compensates the corresponding symbol subsequence. This invention cleverly breaks the 90-degree rotational symmetry of the constellation diagram through amplitude coding, effectively identifying and correcting the inherent fourfold phase ambiguity in the blind phase recovery algorithm. This scheme significantly reduces error propagation caused by phase ambiguity, improves the system's bit error rate and generalized mutual information performance, and also has the advantages of strong compatibility, simple implementation, and low system overhead.

[0015] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and will also become apparent in part to those skilled in the art upon studying the text, or may be learned by practice of the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures specifically pointed out in the description and drawings.

[0016] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, are not intended to limit the scope of the invention. In the drawings: Figure 1 This is a flowchart illustrating a blind carrier phase recovery method for eliminating phase ambiguity in a coherent optical fiber communication system according to an embodiment of the present invention.

[0018] Figure 2 The following is a logic diagram of introducing a phase pilot at the transmitting end in the blind carrier phase recovery method for eliminating phase ambiguity in a coherent optical fiber communication system according to another embodiment of the present invention.

[0019] Figure 3 This is a logic diagram of the receiver compensating for phase ambiguity values ​​in a blind carrier phase recovery method for eliminating phase ambiguity in a coherent optical fiber communication system according to another embodiment of the present invention.

[0020] Figure 4 This is a comparison of the transmission performance between the traditional principal component phase estimation algorithm (PCPE) and the blind carrier phase recovery method for coherent optical fiber communication systems described in this invention.

[0021] Figure 5This is a comparison chart of the transmission performance between the traditional blind phase search algorithm (BPS) and the blind carrier phase recovery method for coherent optical fiber communication systems introduced in this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0023] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0024] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0025] In existing coherent optical communication systems, blind carrier phase retrieval algorithms (such as the blind phase search (BPS) algorithm) are commonly used to compensate for laser phase noise. However, due to the inherent 90-degree rotational symmetry of high-order QAM modulation constellation diagrams, these algorithms suffer from a quadruple phase ambiguity problem. This can cause the receiver to lock the constellation diagram into an incorrect rotational state, leading to systematic error propagation and severely deteriorating key performance indicators such as bit error rate and generalized mutual information. The core technical problem that this invention aims to solve is how to effectively eliminate the phase ambiguity caused by constellation diagram symmetry during blind carrier phase retrieval, thereby avoiding error propagation and improving the reliability of the communication system.

[0026] Optical communication refers to the process of information transmission and exchange between a source and a destination via optical communication. The architecture of an optical communication system can be simplified to three parts: an optical transmitter, an optical fiber / space optical channel, and an optical receiver. The optical transmitter encodes, modulates, performs transmit-end digital signal processing, and performs electro-optical conversion on the source signal, converting the local signal into an optical signal for transmission to the channel. The channel transmits the optical signal generated by the optical transmitter to the optical receiver, enabling the receiver to receive the optical signal from the optical transmitter and perform receive-end optical-to-electrical conversion, receive-end digital signal processing, demodulation, and decoding to recover the source information. Receiver-end digital signal processing techniques for coherent optical communication systems include: DC blocking, filtering, signal quadrature compensation, dispersion compensation, frequency offset recovery, and carrier phase recovery. The innovation of this invention lies in the optimization of carrier phase recovery. Carrier phase recovery is necessary because high-order modulated QAM signals exhibit phase noise due to the certain linewidth of the transmitter and receiver (the laser spectrum has a certain width and is not an ideal impulse signal), causing the QAM signal to rotate, which in turn prevents the receiver from accurately recovering the information from the transmitter.

[0027] Specifically, this invention provides a method for blind carrier phase recovery in a coherent optical fiber communication system to eliminate phase ambiguity, such as... Figure 1 As shown, the method is executed at the receiving end, and the method includes steps S101 to S104: Step S101: Receive the QAM symbol sequence modulated by the transmitter. The QAM symbol sequence is divided into symbol subsequences by the transmitter according to a set length. A phase pilot is added according to the quadrant to which the first symbol in each symbol subsequence belongs. The phase pilot is matched with the four quadrants respectively by mutually distinguishable fixed amplitudes.

[0028] Step S102: Perform carrier phase recovery on the QAM symbol sequence based on the preset algorithm, extract the corresponding phase pilot of the symbol subsequence according to the set length, and use the minimum Euclidean distance criterion to determine the original quadrant to which the first symbol in each symbol subsequence belongs.

[0029] Step S103: Obtain the current quadrant of the phase pilot corresponding to each symbol subsequence in the QAM symbol sequence. Compare the current quadrant of each phase pilot with the original quadrant to obtain the phase ambiguity value. Take the value that is closest to the phase ambiguity value by 90 degrees or an integer multiple thereof as the final phase ambiguity value.

[0030] Step S104: Perform phase compensation on each symbol subsequence according to the corresponding final phase ambiguity value.

[0031] In step S101, the transmitter needs to generate and insert the phase pilot. The transmitter will divide the continuous QAM symbol sequence into shorter symbol blocks or symbol subsequences. This is done because the phase noise of the laser changes slowly over time, and within a short time period, it can be assumed that all symbols in a subsequence have undergone approximately the same phase rotation.

[0032] In some embodiments, the set length for dividing the symbol subsequence is set based on the linewidth tolerance of a preset blind carrier phase recovery algorithm, and the calculation formula is: ; in, Indicates the set length. floor Indicates rounding down to the nearest integer. This represents the sum of the linewidths of the lasers at the receiving and transmitting ends. Indicates the symbol period.

[0033] like Figure 2 As shown, for each symbol subsequence, the transmitter checks the quadrant (first, second, third, or fourth quadrant) of its first symbol (the first symbol) on the constellation diagram. Subsequently, based on this quadrant information, a special phase pilot symbol is generated. The key point is that this pilot symbol does not use conventional QAM constellation points, but instead uses a unique, fixed amplitude value to encode the quadrant information. In some embodiments, the fixed amplitude of the phase pilot is an arithmetic progression proportional to the quadrant number, and the fixed amplitude is greater than the largest amplitude value in the QAM symbol. For example, the four quadrants can each correspond to an amplitude value... , , and These amplitude values ​​form an arithmetic sequence with sufficient differences between them to allow the receiver to distinguish them even in the presence of noise. Finally, this phase pilot symbol containing quadrant information is placed before its corresponding symbol subsequence and transmitted together.

[0034] The core purpose of this step is to attach an absolute phase reference to each data segment (symbol subsequence). Since the amplitude of the pilot is bound to the phase information of the data symbol, and its amplitude value is pre-agreed upon by the transmitter and receiver, this lays the foundation for breaking the 90-degree symmetry of the constellation diagram later.

[0035] In some embodiments, before step S101, i.e. before receiving the QAM symbol sequence modulated by the transmitter, the method further includes receiving a set length published by the transmitter.

[0036] In step S102, as Figure 3As shown, the receiver first uses blind carrier phase recovery algorithms, such as blind phase search algorithms, to perform preliminary phase recovery on the entire received QAM symbol sequence (including pilots and data). This step aims to compensate for the random phase rotation caused by laser phase noise and frequency offset, thereby improving the clustering of constellation points.

[0037] After initial phase recovery, the receiver extracts the phase pilot symbols from the sequence according to the same preset length as the transmitter. Next, the minimum Euclidean distance criterion is used to determine the pilot amplitude: the amplitude value R of the received pilot symbol is measured. The Euclidean distance between R and each of the four preset ideal pilot amplitudes A1, A2, A3, and A4 at the transmitter is calculated; in a one-dimensional amplitude comparison, this is the absolute difference. Choose the ideal amplitude A with the smallest distance. k The corresponding quadrant is then determined to be the original quadrant to which the first symbol of the subsequence belongs. By measuring the rotation-invariant characteristic of the pilot amplitude, the receiver can eliminate the influence of phase rotation introduced by the channel and accurately determine the correct quadrant position of the first symbol of each subsequence when it was initially transmitted by the transmitter.

[0038] In some embodiments, taking a value between 90 degrees or an integer multiple thereof that is closest to the phase blur value as the final phase blur value includes: calculating the quotient of the phase blur value divided by 90 degrees, rounding the quotient to the nearest integer, and then multiplying the resulting integer by 90 degrees, and using the calculation result as the final phase blur value.

[0039] In step S103, the receiving end needs to determine which quadrant the currently received phase pilot symbol falls into on the constellation diagram after blind phase recovery. This quadrant is called the current quadrant.

[0040] The current quadrant of the pilot signal is compared with the original quadrant decoded in step S102 to calculate an initial phase ambiguity value. Due to the 90-degree rotational symmetry of the square QAM constellation diagram, the blind phase retrieval algorithm cannot distinguish the state after the constellation diagram has rotated by 0°, 90°, 180°, or 270°; this is the so-called quadruple phase ambiguity. Therefore, the calculated initial phase ambiguity value needs to be quantized to the nearest integer multiple of 90 degrees, i.e., 0°, 90°, 180°, or 270°. This quantized result is the final phase ambiguity value. By comparing the expected and actual positions of the pilot signals, the systematic, large-scale phase jumps experienced by the entire symbol subsequence are directly diagnosed and accurately identified.

[0041] In step S104, the receiver uses the final phase ambiguity value obtained in step S103 as a phase compensation amount and applies it to the entire symbol subsequence corresponding to the phase pilot. Through this operation, constellation points that have been incorrectly rotated by 90°, 180°, or 270° due to constellation diagram symmetry can be corrected back to the only correct orientation, thereby completely eliminating the systemic bit error risk caused by phase ambiguity.

[0042] This invention successfully solves the inherent quadruple phase ambiguity problem in blind carrier phase recovery by cleverly inserting a phase pilot with amplitude encoding at the transmitting end and using its amplitude information as an absolute reference at the receiving end. This method combines the advantages of high spectral efficiency of blind algorithms and accurate pilot-assisted phase reference, providing strong support for the reliable application of high-order QAM in coherent optical communication.

[0043] On the other hand, the present invention also provides a receiving device for eliminating phase ambiguity, the receiving device including a receiving module, a phase recovery and decoding module, an ambiguity value calculation module and a compensation module.

[0044] The receiving module is used to receive the QAM symbol sequence modulated by the transmitting end. The QAM symbol sequence is divided into symbol groups by the transmitting end according to a set length, and a phase pilot is added according to the quadrant to which the first symbol in each symbol group belongs. The phase pilot is matched with the four quadrants respectively by mutually distinguishable fixed amplitudes.

[0045] The phase recovery and decoding module is used to perform carrier phase recovery on QAM symbol sequences based on a preset blind carrier phase recovery algorithm, extract the corresponding phase pilots for symbol groups according to a set length, and use the minimum Euclidean distance criterion to determine the amplitude and the original quadrant to which the first symbol in each symbol group belongs.

[0046] The ambiguity value calculation module is used to obtain the current quadrant of the phase pilot corresponding to each symbol group in the QAM symbol sequence. It compares the current quadrant of each phase pilot with the original quadrant to obtain the phase ambiguity value, and takes the value that is closest to the phase ambiguity value by 90 degrees or an integer multiple thereof as the final phase ambiguity value.

[0047] The compensation module is used to perform phase compensation on each symbol group according to the corresponding final phase ambiguity value.

[0048] On the other hand, the present invention also provides an optical fiber communication system for eliminating phase ambiguity, the system comprising: a transmitting end device and the aforementioned receiving end device for eliminating phase ambiguity.

[0049] The transmitting device is used to divide the QAM symbol sequence to be transmitted into symbol groups according to a set length, determine the quadrant to which the first symbol in each symbol group belongs, generate a phase pilot with a corresponding fixed amplitude according to the quadrant, and insert the phase pilot before the corresponding symbol group for transmission; the receiving device executes the above steps S101~S104.

[0050] On the other hand, the present invention also provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a processor, implement the steps of the above-described method.

[0051] On the other hand, the present invention also provides a computer program product, including a computer program or instructions that, when executed by a processor, implement the steps of the above-described method.

[0052] The present invention will now be described with reference to a specific embodiment: This embodiment provides a blind carrier phase recovery method for coherent optical fiber communication systems to eliminate phase ambiguity. It is compatible with various blind carrier phase recovery algorithms, significantly reduces the probability of phase ambiguity, and improves communication quality. The specific steps of the method include: At the sending end, the QAM symbol sequence is obtained. The QAM symbol sequence can be represented as: ; (1) Where TX represents the QAM symbol sequence at the transmitting end, n is the length of the sequence, and A n B represents the real part of the QAM symbol sequence. n denoted by , where j is the imaginary unit of the QAM symbol sequence.

[0053] like Figure 2 As shown, the QAM symbol sequence is grouped. Specifically, assuming the length of the QAM symbol sequence TX at the transmitting end is n, if the group length is m (the length of each group after adding the pilot symbols is m+1), then every m QAM symbols are grouped together. TXSUB represents the QAM symbol subsequence at the transmitting end, with a quantity of n / m. The group length is optional, and the grouping format is as follows: ; (2) The quadrant position of the first symbol in each symbol subsequence is determined. Specifically, after grouping the TX sequence, if both the real and imaginary parts of the first symbol in each group are positive, it belongs to the first quadrant; if the real part is negative and the imaginary part is positive, it belongs to the second quadrant; if both the real and imaginary parts are negative, it belongs to the third quadrant; and if the real part is positive and the imaginary part is negative, it belongs to the fourth quadrant. Amplitude encoding is used to generate the phase pilot, and the amplitude of the phase pilot is proportional to the quadrant value. For example, if the first symbol in the symbol subsequence is in the first quadrant, the phase pilot amplitude is set to... The pilot amplitude corresponding to the second quadrant is set to The pilot amplitude corresponding to the third quadrant is set to The pilot amplitude corresponding to the fourth quadrant is set to .

[0054] After all phase pilots are set, they are placed before each symbol subsequence and transmitted with the symbol subsequence; At the receiving end, such as Figure 3 As shown, the QAM symbol sequence at the receiving end is obtained, and the carrier phase recovery is achieved using an optional blind carrier phase recovery algorithm. Specifically, if the BPS algorithm is used, the group length is equal to the subsequence length above. The BPS algorithm will perform phase recovery on each group of signals. However, since the BPS algorithm only performs phase recovery on the current symbol subsequence, there may be phase ambiguity between different symbol subsequences, i.e., phase discontinuity. To eliminate the effects of phase ambiguity, the phase pilot of each symbol subsequence is extracted. The receiver knows the sequence length of the transmitter to ensure signal synchronization.

[0055] The minimum Euclidean distance criterion is used for amplitude determination. For example, if the received phase pilot amplitude is C... i , is represented as: ; (3) If C i The amplitude is 1.4, which is closer to the initial phase pilot amplitude setting. If the first symbol of this symbol subsequence is located in the first quadrant, the quadrant information of the first symbol of each symbol subsequence is determined by the magnitude value of the decision.

[0056] The quadrant value of the current phase pilot is compared with the quadrant information value recovered from the phase pilot. The current phase pilot is the phase pilot added to the beginning of each subsequence at the transmitting end, transmitted with the subsequence, and becomes the phase pilot added to the beginning of each subsequence at the receiving end. The quadrant value of the current phase pilot is determined as follows: if both the real and imaginary parts of the phase pilot are positive, it belongs to the first quadrant; if the real part is negative and the imaginary part is positive, it belongs to the second quadrant; if both the real and imaginary parts are negative, it belongs to the third quadrant; and if the real part is positive and the imaginary part is negative, it belongs to the fourth quadrant. The quadrant information recovered from the phase pilot is achieved through amplitude determination using the minimum Euclidean distance criterion, as described above. A phase ambiguity value can be obtained. The current phase ambiguity value cannot be directly used to eliminate phase ambiguity. Since the phase ambiguity value is 90 degrees and its integer multiples, a value between 90 degrees and its integer multiples that is closest to the current phase ambiguity value is taken as the final phase ambiguity value.

[0057] The final phase blur value is applied to each symbol subsequence to achieve the final phase blur compensation. The specific compensation method is as follows: If the current phase pilot is located in the first quadrant, but the quadrant recovered from the phase pilot is in the third quadrant, it means that the two are separated by two quadrants. Assuming the number of quadrants that are separated is N, then the final angle that needs to be compensated is Nπ / 2. RXSUB j Indicates the sequence of the j-th receiving terminal: (5) Corresponding to the above method, the present invention also provides an apparatus / system including a computer device, the computer device including a processor and a memory, the memory storing computer instructions, the processor executing the computer instructions stored in the memory, and when the computer instructions are executed by the processor, the apparatus / system performs the steps of the method as described above.

[0058] like Figure 4 and Figure 5 As shown, the present invention introduces a scheme based on the Principal Component Phase Estimation (PCPE) algorithm for blind carrier phase recovery. Compared with the original traditional PCPE scheme, the Generalized Mutual Information (GMI) index is significantly improved, reflecting a significant increase in the maximum reliable information rate that the channel can transmit. The present invention also introduces a scheme based on the Blind Phase Search (BPS) algorithm for blind carrier phase recovery. Compared with the original traditional BPS scheme, the GMI index is steadily improved across all signal-to-noise ratio (SNR) ranges, resulting in more reliable data transmission performance.

[0059] This invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the aforementioned edge computing server deployment method. The computer-readable storage medium can be a tangible storage medium, such as random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, floppy disks, hard disks, removable storage disks, CD-ROMs, or any other form of storage medium known in the art.

[0060] In summary, the blind carrier phase recovery method and system for optical fiber communication described in this invention involves the transmitter dividing the QAM symbol sequence into symbol subsequences and adding a phase pilot with a specific fixed amplitude based on the quadrant of the first symbol in each subsequence. After completing blind carrier phase recovery, the receiver determines the original quadrant of the phase pilot using the minimum Euclidean distance criterion, compares it with the current quadrant, calculates the final phase ambiguity value in the form of 90 degrees or its integer multiples, and compensates the corresponding symbol subsequence. This invention cleverly breaks the 90-degree rotational symmetry of the constellation diagram through amplitude coding, effectively identifying and correcting the inherent fourfold phase ambiguity in the blind phase recovery algorithm. This scheme significantly reduces error propagation caused by phase ambiguity, improves the system's bit error rate and generalized mutual information performance, and also has the advantages of strong compatibility, simple implementation, and low system overhead.

[0061] Those skilled in the art will understand that the exemplary components, systems, and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Whether implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention. When implemented in hardware, it can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this invention are programs or code segments used to perform the desired tasks. The programs or code segments can be stored in a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried in a carrier wave.

[0062] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0063] In this invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or in place of features of other embodiments.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations of the embodiments of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for blind carrier phase recovery in a coherent optical fiber communication system to eliminate phase ambiguity, characterized in that, The method is executed at the receiving end, and the method includes: The receiver receives a QAM symbol sequence modulated by the transmitter. The QAM symbol sequence is divided into symbol subsequences according to a set length by the transmitter. A phase pilot is added according to the quadrant to which the first symbol in each symbol subsequence belongs. The phase pilot is matched with each of the four quadrants by mutually distinguishable fixed amplitudes. Based on a preset algorithm, carrier phase recovery is performed on the QAM symbol sequence, and the corresponding phase pilot is extracted from the symbol subsequence according to the set length. The minimum Euclidean distance criterion is used to determine the amplitude and determine the original quadrant of the first symbol in each symbol subsequence. Obtain the current quadrant of the phase pilot corresponding to each symbol subsequence in the QAM symbol sequence, compare the current quadrant of each phase pilot with the original quadrant to obtain the phase ambiguity value, calculate the quotient of the phase ambiguity value divided by 90 degrees, round the quotient to the nearest integer, and then multiply the integer obtained by 90 degrees to obtain the final phase ambiguity value. Phase compensation is performed on each symbol subsequence according to the corresponding final phase ambiguity value.

2. The blind carrier phase recovery method for coherent optical fiber communication systems to eliminate phase ambiguity according to claim 1, characterized in that, The preset algorithm is a blind carrier phase recovery algorithm.

3. The blind carrier phase recovery method for coherent optical fiber communication systems to eliminate phase ambiguity according to claim 2, characterized in that, The set length used to divide the symbol subsequence is set based on the linewidth tolerance of the blind carrier phase recovery algorithm, and is calculated as follows: ； in, This indicates the set length. floor Indicates rounding down to the nearest integer. This represents the sum of the linewidths of the lasers at the receiving and transmitting ends. Indicates the symbol period.

4. The blind carrier phase recovery method for eliminating phase ambiguity in a coherent optical fiber communication system according to claim 1, characterized in that, The fixed amplitude of the phase pilot is an arithmetic sequence proportional to the quadrant number, and the fixed amplitude is greater than the maximum amplitude value in the QAM symbol.

5. The blind carrier phase recovery method for eliminating phase ambiguity in a coherent optical fiber communication system according to claim 1, characterized in that, Before receiving the QAM symbol sequence modulated by the transmitter, the method further includes receiving the set length published by the transmitter.

6. A receiving device for eliminating phase ambiguity, characterized in that, The receiving device includes a receiving module, a phase recovery and decoding module, a fuzzy value calculation module, and a compensation module; The receiving module is used to receive a QAM symbol sequence modulated by the transmitting end. The QAM symbol sequence is divided into symbol groups by the transmitting end according to a set length, and a phase pilot is added according to the quadrant to which the first symbol in each symbol group belongs. The phase pilots are matched to the four quadrants respectively by mutually distinct fixed amplitudes; The phase recovery and decoding module is used to perform carrier phase recovery on the QAM symbol sequence based on a preset blind carrier phase recovery algorithm, extract the corresponding phase pilot of the symbol group according to the set length, and use the minimum Euclidean distance criterion to determine the amplitude to determine the original quadrant of the first symbol in each symbol group. The ambiguity value calculation module is used to obtain the current quadrant of the phase pilot corresponding to each symbol group in the QAM symbol sequence, compare the current quadrant of each phase pilot with the original quadrant to obtain the phase ambiguity value, calculate the quotient of the phase ambiguity value divided by 90 degrees, round the quotient to the nearest integer, and then multiply the integer obtained by 90 degrees to obtain the final phase ambiguity value. The compensation module is used to perform phase compensation on each symbol group according to the corresponding final phase ambiguity value.

7. A fiber optic communication system for eliminating phase ambiguity, characterized in that, The system includes: The transmitting device is used to divide the QAM symbol sequence to be transmitted into symbol groups according to a set length, determine the quadrant to which the first symbol in each symbol group belongs, generate a phase pilot with a corresponding fixed amplitude according to the quadrant, and insert the phase pilot before the corresponding symbol group for transmission; And the receiving device for eliminating phase ambiguity as described in claim 6.

8. A computer-readable storage medium having a computer program or instructions stored thereon, characterized in that, When the computer program or instructions are executed by a processor, they implement the steps of the method as described in any one of claims 1 to 5.

9. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by a processor, they implement the steps of the method described in any one of claims 1 to 5.

Images