Communication parameter monitoring method and system

Abstract

The invention discloses a communication parameter monitoring method and system, and relates to the technical field of optical fiber communication, the communication parameter monitoring method is applied to the communication parameter monitoring system, the communication parameter monitoring system comprises a sending end and a receiving end, and the communication parameter monitoring method comprises the following steps: the sending end inserts a preset pilot frequency in to-be-transmitted information to generate a modulation signal; the sending end sends the modulation signal to a receiving end, and a receiving signal is obtained after coherent receiving; the receiving end carries out digital signal processing on the received signal and extracts pilot frequency information; and the receiving end calculates communication parameters between the sending end and the receiving end according to the pilot frequency information. The signal and the frequency domain pilot frequency are simultaneously transmitted and received, and the power of the frequency domain pilot frequency is far less than the power of the signal, so that the influence on the signal can be ignored, the online monitoring can be realized on the basis of not interrupting the communication service, and the multi-damage cooperative monitoring is realized. Through the communication parameter monitoring method, guarantee can be provided for stable operation and resource scheduling of the space division multiplexing system.

Description

Technical Field

[0001] This application relates to the field of optical fiber communication technology, and particularly to a communication parameter monitoring method and system. Background Art

[0002] With the rapid development of emerging information technologies such as artificial intelligence, large models, Internet of Things, and cloud computing, the global information traffic has shown exponential growth. To meet this demand, optical fiber communication systems have fully exploited the multiplexing potential of optical signals in multi-dimensional physical domains such as time, orthogonality, frequency, and polarization. However, the utilization rate of the communication capacity of single-mode optical fibers has approached its theoretical limit (nonlinear Shannon limit). Facing the upcoming optical fiber transmission capacity crisis, space division multiplexing (SDM) technology, as the only unexploited spatial dimension in the optical fiber physical layer, has become an inevitable choice to break through the capacity limit of optical fiber communication systems.

[0003] In space division multiplexing optical fiber transmission, the signal faces the coupling effect of multi-dimensional losses, which not only increases the complexity of the digital signal processing system at the receiving end but also poses risks of system capacity fluctuations and even communication interruptions. Traditional monitoring methods can only monitor a single damage parameter and have not achieved multi-damage collaborative coupling monitoring.

[0004] Therefore, how to perform multi-loss collaborative monitoring in a space division multiplexing channel environment is an urgent problem to be solved currently. Summary of the Invention

[0005] The main purpose of this application is to provide a communication parameter monitoring method and system, aiming to solve the technical problem that multi-damage collaborative monitoring cannot be performed in a space division multiplexing channel environment.

[0006] To achieve the above object, this application proposes a communication parameter monitoring method. The communication parameter monitoring method is applied to a communication parameter monitoring system, and the communication parameter monitoring system includes a sending end and a receiving end. The communication parameter monitoring method includes:

[0007] The sending end inserts a preset pilot into the information to be transmitted to generate a modulated signal;

[0008] The sending end sends the modulated signal to the receiving end, and after coherent reception, a received signal is obtained;

[0009] The receiving end performs digital signal processing on the received signal to extract pilot information;

[0010] The receiving end calculates the communication parameter between the sending end and the receiving end according to the pilot information.

[0011] In one embodiment, the step of the transmitting end inserting a preset pilot into the information to be transmitted and generating a modulation signal includes:

[0012] The transmitting end modulates and shapes the information to be transmitted to generate multiple signal acquisition paths;

[0013] The transmitting end inserts a preset pilot in the polarization dimension of each of the signal acquisition paths to obtain a modulation signal.

[0014] In one embodiment, the pilot information includes a multi-dimensional channel response matrix and a receiving-end pilot. The step of the receiving end performing digital signal processing on the received signal and extracting the pilot information includes:

[0015] The receiving end performs frequency offset compensation on the received signal to obtain a compensated signal;

[0016] The receiving end performs down-conversion and narrowband low-pass filtering on the compensated signal to extract the receiving-end pilot;

[0017] The receiving end constructs a multi-dimensional channel response matrix according to the receiving-end pilot.

[0018] In one embodiment, the step of the receiving end performing frequency offset compensation on the received signal and obtaining a compensated signal includes:

[0019] The receiving end calculates a frequency offset estimation result according to the preset pilot and the receiving-end pilot;

[0020] The receiving end performs frequency offset compensation on the received signal according to the frequency offset estimation result to obtain a compensated signal.

[0021] In one embodiment, the communication parameters include a mode coupling parameter, a mode-dependent loss coefficient, and an inter-mode group delay parameter. The step of the receiving end calculating the communication parameters between the transmitting end and the receiving end according to the pilot information includes:

[0022] The receiving end obtains the relative power distribution of the receiving-end pilot in each polarization mode and the channel matrices of multiple frequency points corresponding to the receiving-end pilot according to the pilot information and the preset pilot;

[0023] The receiving end estimates the mode coupling parameter according to the relative power distribution of each polarization mode;

[0024] The receiving end estimates the mode-dependent loss coefficient and the inter-mode group delay parameter according to the channel matrices of multiple frequency points corresponding to the receiving-end pilot.

[0025] In one embodiment, the step of estimating the mode-dependent loss coefficient and the inter-mode group delay parameter according to the channel matrices of multiple frequency points corresponding to the receiving-end pilot includes:

[0026] The receiving end calculates the eigenvalues of each group of channel matrices according to the channel matrices corresponding to the frequency points of the multiple groups of receiving-end pilots;

[0027] The receiving end estimates the mode-related loss according to the eigenvalues of each group of channel matrices;

[0028] The receiving end divides any two groups of channel matrices to obtain the corresponding inter-mode matrix, and calculates the eigenvalues of the inter-mode matrix;

[0029] The receiving end estimates the inter-mode group delay parameter according to the eigenvalues of the inter-mode matrix.

[0030] This application also proposes a communication parameter monitoring system, which includes a sending end and a receiving end;

[0031] The sending end is used to insert a preset pilot into the information to be transmitted to generate a modulated signal;

[0032] The sending end is used to send the modulated signal to the receiving end, and after coherent reception, a received signal is obtained;

[0033] The receiving end is used to perform digital signal processing on the received signal to extract pilot information;

[0034] The receiving end is also used to calculate the communication parameters between the sending end and the receiving end according to the pilot information.

[0035] In one embodiment, the sending end is also used to modulate and shape the information to be transmitted to generate multiple signal acquisition paths;

[0036] The sending end is also used to insert a preset pilot in the polarization dimension of each of the signal acquisition paths to obtain a modulated signal.

[0037] In one embodiment, the receiving end is also used to perform frequency offset compensation on the received signal to obtain a compensated signal;

[0038] The receiving end is also used to perform down-conversion and narrowband low-pass filtering on the compensated signal to extract the receiving-end pilot;

[0039] The receiving end is also used to construct a multi-dimensional channel response matrix according to the receiving-end pilot.

[0040] In one embodiment, the receiving end is also used to calculate a frequency offset estimation result according to the preset pilot and the receiving-end pilot;

[0041] The receiving end is also used to perform frequency offset compensation on the received signal according to the frequency offset estimation result to obtain a compensated signal.

[0042] One or more technical solutions proposed in this application have at least the following technical effects:

[0043] The communication parameter monitoring method is applied to a communication parameter monitoring system. The communication parameter monitoring system includes a sending end and a receiving end. The communication parameter monitoring method includes: the sending end inserts a preset pilot into the information to be transmitted, generates a modulation signal, and sends the modulation signal to the receiving end; the receiving end performs digital signal processing on the received signal and extracts the pilot information of the received pilot; the receiving end calculates the communication parameters between the sending end and the receiving end according to the pilot information and the preset pilot. By inserting a preset pilot into the information to be transmitted and sending it to the receiving end, the receiving end can extract the pilot information of the pilot, realizing multi-parameter joint monitoring. Since the signal and the frequency-domain pilot are transmitted and received simultaneously, and the power of the frequency-domain pilot is much smaller than the signal power, the influence on the signal can be ignored, and online monitoring can be realized without interrupting the communication service, realizing multi-damage collaborative monitoring. Further, it provides guarantee for the stable operation and resource scheduling of the space division multiplexing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application.

[0045] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is a schematic flowchart of the first embodiment of the communication parameter monitoring method of this application;

[0047] Figure 2 It is a schematic diagram of the communication parameter monitoring system of the embodiment of the communication parameter monitoring method of this application;

[0048] Figure 3 It is a schematic flowchart of the second embodiment of the communication parameter monitoring method of this application;

[0049] Figure 4 It is a schematic diagram of the spectrum of the modulation signal of the embodiment of this application;

[0050] Figure 5 It is a schematic flowchart of the third embodiment of the communication parameter monitoring method of this application;

[0051] Figure 6 It is a flowchart of the mode coupling, mode-dependent loss, and inter-mode group time monitoring of the embodiment of this application;

[0052] Figure 7 Schematic diagram of the communication parameter monitoring system according to the fourth embodiment of the present application.

[0053] Explanation of the reference numerals in the accompanying drawings:

[0054] 10. Transmitting end; 20. Receiving end.

[0055] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. Specific implementation manners

[0056] It should be understood that the specific embodiments described herein are only used to explain the technical solution of the present application and are not used to limit the present application.

[0057] In order to better understand the technical solution of the present application, the following will be described in detail with reference to the accompanying drawings of the specification and specific implementation manners.

[0058] With the rapid development of emerging information technologies such as artificial intelligence, large models, Internet of Things, and cloud computing, the global information traffic has shown exponential growth. To meet this demand, fiber optic communication systems have fully exploited the multiplexing potential of optical signals in multi-dimensional physical domains such as time, orthogonality, frequency, and polarization. However, the utilization rate of the communication capacity of single-mode optical fibers has approached its theoretical limit (nonlinear Shannon limit). Facing the upcoming fiber optic transmission capacity crisis, space division multiplexing technology (SDM), as the only unexploited spatial dimension in the fiber optic physical layer, has become an inevitable choice to break through the capacity limit of fiber optic communication systems. In space division multiplexing fiber optic transmission, the signal faces the coupling effect of multi-dimensional losses, which not only increases the complexity of the digital signal processing system at the receiving end but also poses risks of system capacity fluctuations and even communication interruptions. Traditional monitoring methods can only monitor a single damage parameter and have not yet achieved multi-damage collaborative coupling monitoring.

[0059] The present application provides a solution applied to a communication parameter monitoring system. The communication parameter monitoring system includes a transmitting end and a receiving end. The communication parameter monitoring method includes: the transmitting end inserts a preset pilot into the information to be transmitted to generate a modulated signal; the transmitting end sends the modulated signal to the receiving end, and after coherent reception, a received signal is obtained; the receiving end performs digital signal processing on the received signal to extract the pilot information; the receiving end calculates the communication parameters between the transmitting end and the receiving end according to the pilot information. By inserting a preset pilot into the information to be transmitted and sending it to the receiving end, the receiving end can extract the pilot information of the pilot, realizing multi-parameter joint monitoring. Since the signal and the frequency-domain pilot are transmitted and received simultaneously, and the power of the frequency-domain pilot is much smaller than that of the signal, the influence on the signal can be ignored, and online monitoring can be realized without interrupting the communication service, achieving multi-damage collaborative monitoring. Further, the reliability and stability of communication in the space division multiplexing channel environment are improved.

[0060] Based on this, the embodiments of the present application provide a communication parameter monitoring method. Referring to Figure 1 , Figure 1 which is a schematic flowchart of the first embodiment of the communication parameter monitoring method of the present application. It should be noted that the communication parameter monitoring method is applied to a communication parameter monitoring system, and the communication parameter monitoring system includes a sending end and a receiving end. In this embodiment, the communication parameter monitoring method includes steps S10 to S30:

[0061] Step S10, the sending end inserts a preset pilot into the information to be transmitted to generate a modulated signal.

[0062] It should be noted that the sending end can be a device or module in the communication system responsible for generating and transmitting signals, which is used to integrate the preset pilot and the information to be transmitted into a composite signal. The information to be transmitted can be a digital bit stream or an analog signal. In a spatial division multiplexing system, the information to be transmitted is segmented into different spatial modes (such as optical fiber cores or mode groups) for parallel transmission. The preset pilot can be a pre-designed known reference signal, which can have a specific frequency, power, and time-frequency structure (such as a comb-shaped spectrum), and is used to provide a traceable benchmark for channel impairment monitoring. The modulated signal can be understood as a composite signal formed by loading the information to be transmitted and the preset pilot onto a carrier, and the modulation methods include but are not limited to QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 64QAM (Quadrature Amplitude Modulation), etc.

[0063] Step S20, the sending end sends the modulated signal to the receiving end, and after coherent reception, a received signal is obtained.

[0064] It should be noted that the receiving end can be a device or module in the communication system responsible for receiving and parsing the modulated signal. Coherent reception has high sensitivity and anti-interference ability, and can effectively improve the performance of the communication system.

[0065] Step S30, the receiving end performs digital signal processing on the received signal and extracts the pilot information.

[0066] It should be noted that the receiving end can be a device or module in the communication system responsible for receiving and parsing the modulated signal. Digital signal processing can be understood as a technology for performing various operations, transformations, and analyses on digital signals. Exemplarily, the receiving end needs to first perform analog-to-digital conversion on the received signal to turn it into a digital signal, and then perform processing on the digital signal, such as filtering, amplification, demodulation, decoding, etc. operations, to recover the original signal or extract the information carried in the original signal. The pilot information can be understood as the pilot component separated from the received signal by the receiving end. Exemplarily, the time-domain pilot signal can be converted to the frequency domain through Fourier transform, which is used to characterize the amplitude and phase characteristics of the signal at different frequency components.

[0067] Step S40, the receiving end calculates the communication parameters between the sending end and the receiving end according to the pilot information.

[0068] It should be noted that the communication parameters can be understood as physical quantities characterizing the channel impairment characteristics.

[0069] Exemplarily, the communication parameter monitoring system is as Figure 2 shown. Taking the signal transmission in two modes as an example, the information to be transmitted (such as a bit sequence) is processed by the digital signal processing system (Tx DSP) at the sending end. A preset pilot is inserted into the transmitted signal, and the bit sequence is mapped into the required modulation format signals respectively. The modulation formats include but are not limited to QPSK, 16QAM, 64QAM, etc. The signal processed by Tx DSP is used to drive a dual-polarization IQ modulator after digital-to-analog conversion (DAC). The modulated signal is multiplexed by a multiplexer and then loaded onto a space-division multiplexing optical fiber for transmission. In Figure 2 it, two strongly coupled few-mode optical fibers are taken as an example for analysis. After the signal is transmitted through the optical fiber and reaches the receiving end, it is divided into two paths by a demultiplexer and subjected to coherent detection respectively. The detected signal is processed by the digital signal processing system (Rx DSP) at the receiving end after analog-to-digital conversion.

[0070] In this embodiment, by inserting a preset pilot into the information to be transmitted and sending it to the receiving end, the receiving end can extract the pilot information of the pilot, realizing multi-parameter joint monitoring. Since the signal and the frequency-domain pilot are transmitted and received simultaneously, and the power of the frequency-domain pilot is much smaller than that of the signal, the influence on the signal can be ignored, and online monitoring can be realized without interrupting the communication service, realizing multi-impairment collaborative monitoring. Further, it provides guarantee for the stable operation and resource scheduling of the space-division multiplexing system.

[0071] Referring to Figure 3 , Figure 3 is the flowchart of the second embodiment of the communication parameter monitoring method of this application. Based on the first embodiment shown above Figure 1 a second embodiment of the communication parameter monitoring method of this application is proposed.

[0072] In the second embodiment, the step S10 includes:

[0073] Step S101, the sending end modulates and shapes the information to be transmitted to generate multiple signal acquisition paths.

[0074] It should be noted that modulating and shaping can be understood as mapping the information to be transmitted into an optical or electrical waveform, and the time-frequency characteristics of the signal can be optimized through a pulse shaping filter. Multiple signal acquisition paths can be understood as space-division multiplexing paths generated after modulating and shaping the information to be transmitted at the sending end.

[0075] Exemplarily, a root raised cosine filter can be used to shape the signals respectively. After shaping, the signals are subjected to subcarrier multiplexing (SCM), and the number of subcarriers for each polarization of each mode can be designed according to requirements. A guard bandwidth is reserved between adjacent subcarriers of the SCM signal for protection. The guard bandwidth needs to ensure that adjacent subcarriers do not overlap according to the subcarrier baud rate and the setting of the shaping filter.

[0076] Step S102, the transmitting end inserts a preset pilot in the polarization dimension of each signal acquisition path to obtain a modulated signal.

[0077] It should be noted that after generating the multi-channel spatial division multiplexing signal, a frequency-domain pilot can be inserted in the polarization dimension of each multiplexing path. Exemplarily, a frequency-domain pilot f can be inserted respectively in each polarization of each mode of the information to be transmitted. kij , and the spectral schematic diagram of the generated modulated signal is as Figure 4 shown, where the subscript k is the corresponding mode, i ∈ {x, y} represents the polarization where the pilot is located, and j ∈ {1, 2} represents the position where the pilot is located. Taking the subcarrier multiplexing signal as an example, when inserting the pilot, the pilot is located in the gap between adjacent subcarriers. It should be noted that since the power of the pilot signal is small enough, in a single-carrier signal, the pilot can also be directly placed above the signal spectrum, but the receiving end needs an additional algorithm to eliminate the inserted pilot.

[0078] Exemplarily, a frequency-domain pilot with a frequency of ω is inserted respectively in each polarization of each mode of the information to be transmitted. kij to obtain a modulated signal, and the modulated signal can be expressed by formula (1).

[0079]

[0080] In formula (1), s ki (t) is the signal to be modulated, k is the corresponding mode, and i ∈ {x, y} represents the polarization of the signal; A is the amplitude corresponding to the pilot, and the power of the pilot is much smaller than the power of the signal, and the power ratio of the pilot signal is lower than -15 dB. ω kij is the frequency of the pilot, and j ∈ {1, 2} indicates the group of the pilot. The pilot frequencies with the same j are preferably controlled within 200 MHz.

[0081] Exemplarily, when the transmitting end adds a frequency-domain pilot, the pilot and the signal may not be directly superimposed. Instead, the pilot and the signal are separated in the time domain. By designing the frame structure of the signal, only the frequency-domain pilot is loaded in a section of the beginning data, and then the signal to be transmitted is added. The signal to be transmitted can be of any modulation format and multiplexing method. The receiving end extracts the sequence corresponding to the pilot after frame synchronization to estimate the impairment.

[0082] In addition, the added frequency-domain pilot can be changed. The added frequency-domain pilot may not be added simultaneously in the I and Q branches. For example,j2πft This form exists. It is also possible to add cos(2πft) only to the I or Q path, or add other waveforms with single-frequency peaks such as sawtooth waves and triangular waves. In addition, the added frequency-domain pilot can also be added not in the digital domain but in the optical domain. For example, by changing the bias point and introducing other lasers to add the frequency-domain pilot.

[0083] In this embodiment, by shaping the signal to improve the subcarrier multiplexing density, the crosstalk power between adjacent modes is reduced. By ensuring that adjacent subcarriers do not overlap, the bit error rate caused by non-ideal filtering is avoided. After generating the multi-channel spatial division multiplexing signal, frequency-domain pilots are inserted into the polarization dimension of each multiplexing path, and preset pilots are inserted, realizing that a single pilot transmission can simultaneously obtain mode coupling and loss parameters, and realizing multi-impairment collaborative monitoring without interrupting the communication service.

[0084] In one implementation, the pilot information includes a multi-dimensional channel response matrix and a receiver pilot. The step S30 includes: the receiver performs frequency offset compensation on the received signal to obtain the compensated signal; the receiver performs down-conversion and narrowband low-pass filtering on the compensated signal to extract the receiver pilot; the receiver constructs a multi-dimensional channel response matrix according to the receiver pilot.

[0085] It should be noted that the step of the receiver performing frequency offset compensation on the received signal to obtain the compensated signal includes: the receiver calculates the frequency offset estimation result according to the preset pilot and the receiver pilot; the receiver performs frequency offset compensation on the received signal according to the frequency offset estimation result to obtain the compensated signal.

[0086] It should be noted that the frequency offset estimation result can be understood as the frequency offset amount calculated by comparing the preset pilot frequency and the received pilot frequency. The frequency offset can be eliminated by performing frequency translation on multiple signals. Exemplarily, the signal received by the receiver can be expressed as formula (2).

[0087]

[0088] In formula (2), f j is the jth group of pilots. Since the frequency difference of pilots with the same j is within 200 MHz, it can be approximately considered that f 1xj ≈f 1yj ≈f 2xj ≈f 2yj ≈f j ; PT Tj (t) and PT Rj (t) are the transmitted and received frequency-domain pilots respectively. PT Tj (t) is expressed as formula (3). H(f j ) is the optical fiber channel at the frequency of f jThe frequency response is expressed as Equation (4).

[0089]

[0090] Correspondingly, the received frequency-domain pilots can be expressed as Equation (5).

[0091]

[0092] At the receiving-end DSP, first estimate the frequency offset Δf by comparing the frequency difference between the received signal pilots and the transmitted signal pilots. After estimating the frequency offset, shift each received pilot to zero frequency, and then extract each frequency-domain pilot using a narrow-bandwidth low-pass filter, which is expressed as Equation (6).

[0093]

[0094] In the above formula, X k1,ix,j is the frequency-domain pilot extracted at the receiving end, and H{·} represents the low-pass filtering operation. After extracting the receiving-end pilots, the channel transmission matrix corresponding to the corresponding frequency points can be estimated from the obtained pilots. From the j-th group of frequency-domain pilots, the estimation of the channel matrix is expressed as Equation (7).

[0095]

[0096] In this embodiment, crosstalk caused by mode coupling is eliminated through demultiplexing, providing a pure signal base for subsequent single-channel parameter calculation. Multiple signals are processed independently, improving the monitoring efficiency. The receiving end compensates for the frequency offset of multiple signals, ensuring the accuracy of channel matrix construction. During the damage monitoring process, only the down-conversion and low-pass filtering of pilots are designed, which also greatly reduces the DSP calculation complexity.

[0097] Referring to Figure 5 , Figure 5 is a schematic flowchart of the third embodiment of the communication parameter monitoring method of the present application. Based on the second embodiment shown above Figure 3 a third embodiment of the communication parameter monitoring method of the present application is proposed.

[0098] In the third embodiment, the communication parameters include mode coupling parameters, mode-dependent loss coefficients, and inter-mode group delay parameters. The step S40 includes:

[0099] Step S401, the receiving end obtains the relative power distribution of the received pilots in each polarization mode and the channel matrix corresponding to multiple groups of received pilots at corresponding frequency points according to the pilot information and the preset pilots.

[0100] It should be noted that the relative power distribution can be understood as the power ratio of the received pilot in different polarization modes, reflecting the energy coupling between modes. The multi-frequency channel matrix can be composed of the responses of different pilot frequencies.

[0101] Step S402: The receiving end estimates the mode coupling parameter according to the relative power distribution of each polarization mode.

[0102] It should be noted that the mode coupling parameter can be an index quantifying the energy leakage between different modes, such as the coupling coefficient from mode 1 to mode 2. Exemplarily, after obtaining the received pilots in each frequency domain at the receiving end, since the frequencies loaded by different modes at the transmitting end are different, the mode coupling of the channel can be directly evaluated by calculating the power distribution of the transmitting-end pilot in other modes. The mode coupling is measured by the ratio of the power of the signal coupled to other modes to the power remaining in this mode. Then the mode coupling parameter can be calculated by formulas (8) to (9).

[0103]

[0104] In formulas (8) to (9), α 12 (dB) and α 21 (dB) are the coupling strengths from mode 1 to 2 and from mode 2 to 1 respectively, in units of dB.

[0105] Step S403: The receiving end estimates the mode-related loss coefficient and the inter-mode group delay parameter according to the channel matrix corresponding to multiple groups of received pilots at corresponding frequencies.

[0106] It should be noted that the mode-related loss coefficient (MDL) can be the power attenuation difference of signals in different modes during transmission, and the inter-mode group delay parameter (MGD) can be the time difference of signals in different modes arriving at the receiving end.

[0107] In this embodiment, according to the pilot information and the preset pilot, the relative power distribution of the received pilot in each polarization mode and the channel matrix corresponding to multiple groups of received pilots at corresponding frequencies are obtained, providing a complete channel state, laying a foundation for subsequent parameter decoupling, realizing synchronous acquisition of mode coupling, MDL, and MGD in a single measurement, and realizing multi-impairment collaborative monitoring.

[0108] In one implementation manner, based on the above third embodiment, the step of estimating the mode-related loss coefficient and the inter-mode group delay parameter according to the channel matrix corresponding to multiple groups of received pilots at corresponding frequencies includes: the receiving end calculates the eigenvalues of each group of channel matrices according to the channel matrix corresponding to multiple groups of received pilots at corresponding frequencies; the receiving end estimates the mode-related loss according to the eigenvalues of each group of channel matrices; the receiving end divides any two groups of channel matrices to obtain the corresponding inter-mode matrix and calculates the eigenvalues of the inter-mode matrix; the receiving end estimates the inter-mode group delay parameter according to the eigenvalues of the inter-mode matrix.

[0109] Exemplarily, the flow block diagrams of mode coupling, mode-dependent loss, and intermodal group time monitoring are as Figure 6 shown. The mode-dependent loss and intermodal group delay can be estimated by . First, find the eigenvalues of the matrix , which are expressed as formula (10).

[0110]

[0111] where λ 1x,j , λ 1y,j , λ 2x,j , λ 2y,j are the corresponding four eigenvalues, and the relative mode-dependent losses between the four polarizations can be expressed as formula (11).

[0112]

[0113] In formula (11), represents the mode-dependent loss of the i 2 polarization of the k 2 mode relative to the i 1 polarization of the k 1 mode. In the channel matrix estimated from the frequency-domain pilot, the MGD appears as the phase difference between different polarization modes. However, random modes in the optical fiber can also introduce intermodal phase differences, and mode coupling and MGD cannot be directly decoupled from each other in . It should be noted that the influence of MGD is frequency-dependent, while mode coupling is frequency-independent. This property can be utilized to eliminate the influence of mode coupling and achieve the estimation of MGD. The above process is expressed as formulas (12) to (13).

[0114]

[0115] In the above formulas, the matrix U eliminates the interference of mode coupling, and then the eigenvalues of the matrix U are solved: ρ = eig{U}, where ρ 1x , ρ 1y , ρ 2x , ρ 2y are the corresponding four eigenvalues. represents the intermodal group delay of the i 2 polarization of the k 2 mode relative to the i 1 polarization of the k 1 mode.

[0116] In this embodiment, the mode-related loss coefficient and the inter-mode group delay parameter are estimated according to the channel matrix of multiple groups of received pilots corresponding to frequency points. It does not depend on signal impairment decoupling, and damage monitoring can be achieved by extracting pilots, with high robustness to channel impairments. Due to the high spectral concentration of frequency-domain pilots, near the frequency where the pilot is located, the pilot spectral intensity is much higher than the noise intensity, and it also has strong robustness to white noise.

[0117] In addition, the present application proposes a fourth embodiment, and the fourth embodiment provides a communication parameter monitoring system, as Figure 7 shown, the communication parameter monitoring system includes a transmitting end 10 and a receiving end 20. Among them, the transmitting end 10 is used to insert a preset pilot into the information to be transmitted to generate a modulated signal; the transmitting end 10 is used to send the modulated signal to the receiving end 20, and after coherent reception, a received signal is obtained; the receiving end 20 is used to perform digital signal processing on the received signal to extract pilot information; the receiving end 20 is further used to calculate the communication parameters between the transmitting end 10 and the receiving end 20 according to the pilot information.

[0118] It should be noted that the transmitting end 10 can be a device or module in a communication system responsible for generating and transmitting signals, and is used to integrate a preset pilot with the information to be transmitted into a composite signal. The information to be transmitted can be a digital bit stream or an analog signal. In a spatial division multiplexing system, the information to be transmitted is divided into different spatial modes (such as optical fiber cores or mode groups) for parallel transmission. The preset pilot can be a pre-designed known reference signal, which can have a specific frequency, power, and time-frequency structure (such as a comb-shaped spectrum), and is used to provide a traceable benchmark for channel impairment monitoring. The modulated signal can be understood as a composite signal formed by loading the information to be transmitted and the preset pilot onto a carrier, and the modulation methods include but are not limited to QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 64QAM (Quadrature Amplitude Modulation), etc. The receiving end 20 can be a device or module in a communication system responsible for receiving and analyzing the modulated signal. Digital signal processing can be understood as a technology for performing various operations, transformations, and analyses on digital signals. Exemplarily, the receiving end 20 needs to first perform analog-to-digital conversion on the received signal to become a digital signal, and then perform operations on the digital signal, such as filtering, amplification, demodulation, decoding, etc., to restore the original signal or extract the information carried in the original signal. The pilot information can be understood as the pilot component separated by the receiving end 20 from the received signal. Exemplarily, the time-domain pilot signal can be converted to the frequency domain through Fourier transform, and is used to characterize the amplitude and phase characteristics of the signal at different frequency components. The communication parameter can be understood as a physical quantity representing the characteristics of channel impairment.

[0119] Exemplarily, as Figure 7As shown, taking the signal transmission in two modes as an example, the information to be transmitted (such as a bit sequence) is processed by the digital signal processing system (Tx DSP) of the transmitting end 10. A preset pilot is inserted into the transmitted signal, and the bit sequence is respectively mapped to the signal of the required modulation format, and the modulation format includes but is not limited to QPSK, 16QAM, 64QAM, etc. The signal processed by the TxDSP is used to drive the dual-polarization IQ modulator after digital-to-analog conversion (DAC). The modulated signal is multiplexed by a multiplexer and then loaded onto a space-division multiplexing optical fiber for transmission, and is analyzed with two strongly coupled few-mode optical fibers as an example in Figure 7 After the signal is transmitted through the optical fiber and reaches the receiving end 20, it is divided into two paths by a demultiplexer for coherent detection respectively. The detected signal is processed by the digital signal processing system (Rx DSP) of the receiving end 20 after analog-to-digital conversion.

[0120] In this embodiment, by inserting a preset pilot into the information to be transmitted and sending it to the receiving end, the receiving end can extract the pilot information of the pilot, realizing multi-parameter joint monitoring. Since the signal and the frequency-domain pilot are transmitted and received simultaneously, and the power of the frequency-domain pilot is much smaller than that of the signal, the influence on the signal can be ignored, and online monitoring can be realized without interrupting the communication service, realizing multi-damage collaborative monitoring. Realizing damage monitoring through DSP on the basis of the existing communication system without borrowing other devices greatly reduces the monitoring cost.

[0121] In one implementation manner, the transmitting end 10 is further configured to modulate and shape the information to be transmitted to generate multiple signal acquisition paths; the transmitting end 10 is further configured to insert a preset pilot in the polarization dimension of each signal acquisition path to obtain a modulated signal.

[0122] It should be noted that modulating and shaping can be understood as mapping the information to be transmitted into an optical or electrical waveform, and the time-frequency characteristics of the signal can be optimized through a pulse shaping filter. Multiple signal acquisition paths can be understood as space-division multiplexing paths generated after the information to be transmitted is modulated and shaped at the transmitting end 10.

[0123] Exemplarily, a root-raised cosine filter can be used to shape the signal respectively. After shaping, the signals are subjected to subcarrier multiplexing (SCM), and the number of subcarriers of each polarization of each mode can be designed according to requirements. A guard bandwidth is reserved between adjacent subcarriers of the SCM signal. According to the subcarrier baud rate and the setting of the shaping filter, it is necessary to ensure that adjacent subcarriers do not overlap.

[0124] It should be noted that after generating multiple space-division multiplexing signals, frequency-domain pilots can be inserted in the polarization dimension of each multiplexing path. Exemplarily, frequency-domain pilots f can be inserted respectively in each polarization of each mode of the information to be transmitted kij , and the schematic diagram of the spectrum of the generated modulated signal is asFigure 4 As shown, where the subscript k is the corresponding mode, i ∈ {x, y} represents the polarization where the pilot is located, and j ∈ {1, 2} represents the position where the pilot is located. Taking the subcarrier multiplexed signal as an example, pilots are inserted, and the pilots are located in the gaps between adjacent subcarriers. It should be noted that since the power of the pilot signal is small enough, the pilot can also be directly placed above the signal spectrum in the single-carrier signal, but the receiving end 20 requires an additional algorithm to eliminate the inserted pilot.

[0125] Exemplarily, frequency-domain pilots with a frequency of ω are respectively inserted in each polarization of each mode of the information to be transmitted. kij to obtain a modulated signal, which can be expressed by Equation (14).

[0126]

[0127] In Equation (14), s ki (t) is the signal to be modulated, k is the corresponding mode, and i ∈ {x, y} represents the polarization of the signal; A is the amplitude corresponding to the pilot, and the power of the pilot is much smaller than the power of the signal, and the power ratio of the pilot signal is lower than -15 dB. ω kij is the frequency of the pilot, and j ∈ {1, 2} indicates the group of the pilot. The pilot frequencies with the same j are preferably controlled within 200 MHz.

[0128] In this embodiment, by shaping the signal, the subcarrier multiplexing density is increased, and the crosstalk power between adjacent modes is reduced. By ensuring that adjacent subcarriers do not overlap, the bit error rate caused by non-ideal filtering is avoided. After generating the multi-channel space-division multiplexed signal, frequency-domain pilots are inserted in the polarization dimension of each multiplexing path to insert preset pilots, realizing that the mode coupling and loss parameters can be obtained simultaneously by a single pilot transmission, and multi-impairment collaborative monitoring is realized on the basis of not interrupting the communication service.

[0129] In one implementation, the receiving end 20 is further configured to perform frequency offset compensation on the received signal to obtain a compensated signal; the receiving end 20 is further configured to perform down-conversion and narrowband low-pass filtering on the compensated signal to extract the received-end pilot; the receiving end 20 is further configured to construct a multi-dimensional channel response matrix according to the received-end pilot.

[0130] It should be noted that the receiving end 20 is further configured to calculate a frequency offset estimation result according to the preset pilot and the received-end pilot; the receiving end 20 is further configured to perform frequency offset compensation on the received signal according to the frequency offset estimation result to obtain a compensated signal.

[0131] It should be noted that the multiple signals can be baseband signal streams corresponding to each spatial channel, carrying data and pilot information of the corresponding channels. The steps for the receiving end 20 to perform frequency offset compensation on the received signal and obtain the compensated signal include: the receiving end 20 calculates a frequency offset estimation result based on a preset pilot and a received pilot at the receiving end; the receiving end 20 performs frequency offset compensation on the received signal according to the frequency offset estimation result to obtain the compensated signal.

[0132] It should be noted that the frequency offset estimation result can be the frequency offset amount calculated by comparing the preset pilot frequency and the received pilot frequency. The frequency offset can be eliminated by performing frequency translation on the multiple signals. Exemplarily, the signal received by the receiving end 20 can be expressed by formula (15).

[0133]

[0134] In formula (15), f j is the j-th group of pilots. Since the frequency difference of the pilots with the same j is within 200 MHz, it can be approximately considered that f 1xj ≈f 1yj ≈f 2xj ≈f 2yj ≈f j ; PT Tj (t) and PT Rj (t) are the transmitted and received frequency-domain pilots respectively, and PT Tj (t) is expressed by formula (16). H(f j ) is the frequency response of the optical fiber channel at the frequency of f j and is expressed by formula (17).

[0135]

[0136] Correspondingly, the received frequency-domain pilot can be expressed by formula (18).

[0137]

[0138] At the receiving end 20, first estimate the frequency offset Δf by comparing the frequency difference between the received signal pilot and the transmitted signal pilot. After estimating the frequency offset, shift each received pilot to zero frequency, and then extract each frequency-domain pilot with a narrow-bandwidth low-pass filter, which is expressed by formula (19).

[0139]

[0140] In the above formula, X k1,ix,j is the frequency-domain pilot extracted by the receiving end 20, and H{·} represents the low-pass filtering operation. After extracting the received pilot, the channel transmission matrix at the corresponding frequency point can be estimated from the obtained pilot.

[0141] From the j-th group of frequency-domain pilots, the estimation of the channel matrix can be obtained. It is expressed as Equation (20).

[0142]

[0143] In this embodiment, crosstalk caused by mode coupling is eliminated through demultiplexing, providing a pure signal base for subsequent single-channel parameter calculation. The multi-channel signals are processed independently, improving the monitoring efficiency. The receiver compensates for the frequency offset of the multi-channel signals, ensuring the accuracy of the channel matrix construction. During the damage monitoring process, only the down-conversion and low-pass filtering of the pilots are designed, greatly reducing the DSP computational complexity.

[0144] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the communication parameter monitoring method of this application. Based on this technical concept, more forms of simple transformations are within the protection scope of this application.

[0145] The communication parameter monitoring system provided by this application adopts the communication parameter monitoring method in the above embodiment, which can solve the technical problem of inability to perform multi-damage collaborative monitoring in a space-division multiplexing channel environment. Compared with the prior art, the beneficial effects of the communication parameter monitoring system provided by this application are the same as those of the communication parameter monitoring method provided by the above embodiment, and the other technical features in the communication parameter monitoring system are the same as those disclosed in the above embodiment method, which will not be elaborated here.

[0146] It should be understood that each part disclosed in this application can be implemented by hardware, software, firmware, or a combination of them. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in a suitable manner in any one or more embodiments or examples.

[0147] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in this application, and all should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

[0148] The above is only a partial embodiment of this application, and it does not limit the patent scope of this application. Any equivalent structural transformation made using the content of the specification and drawings of this application under the technical concept of this application, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of this application.

Claims

1. A communication parameter monitoring method, characterized in that: The communication parameter monitoring method is applied to a communication parameter monitoring system, the communication parameter monitoring system includes a transmitting end and a receiving end, and the communication parameter monitoring method includes: The transmitting end inserts a preset pilot into the information to be transmitted to generate a modulated signal; The transmitting end sends the modulated signal to the receiving end, and obtains a received signal after coherent reception; The receiving end performs digital signal processing on the received signal to extract pilot information; The receiving end calculates a communication parameter between the sending end and the receiving end according to the pilot information.

2. The method according to claim 1, characterized in that The transmitting end inserts a preset pilot into the information to be transmitted to generate a modulated signal, comprising: The transmitting end modulates and shapes the information to be transmitted to generate multiple signal acquisition paths; The transmitting end inserts a preset pilot in the polarization dimension of each signal acquisition path to obtain a modulated signal.

3. The method according to claim 1, characterized in that The pilot information includes a multi-dimensional channel response matrix and a receiving end pilot, and the receiving end performs digital signal processing on the received signal to extract the pilot information, including: The receiving end performs frequency offset compensation on the received signal to obtain a compensated signal; The receiving end performs down-conversion and narrow-band low-pass filtering on the compensated signal to extract a receiving end pilot signal; The receiving end constructs a multi-dimensional channel response matrix according to the receiving end pilot.

4. The method according to claim 3, characterized in that The receiving end performs frequency offset compensation on the received signal to obtain a compensated signal, comprising: The receiving end calculates a frequency offset estimation result according to the preset pilot and the receiving end pilot; The receiving end performs frequency offset compensation on the received signal according to the frequency offset estimation result to obtain a compensated signal.

5. The method according to claim 1, characterized in that The communication parameters include mode coupling parameters, mode correlation loss coefficients, and inter-mode group delay parameters. The step of the receiving end calculating the communication parameters between the transmitting end and the receiving end according to the pilot information includes: The receiving end obtains the relative power distribution of the receiving end pilot in each polarization mode and the channel matrix of the frequency points corresponding to the multiple groups of receiving end pilots according to the pilot information and the preset pilot; The receiving end estimates a mode coupling parameter according to the relative power distribution of each polarization mode; The receiving end estimates the mode correlation loss coefficient and the inter-mode group delay parameter according to the channel matrix of the frequency points corresponding to the multiple groups of receiving end pilot signals.

6. The method according to claim 5, characterized in that The step of estimating the mode-related loss coefficient and the inter-mode group delay parameter according to the channel matrix of the frequency points corresponding to the multiple groups of the receiving end pilot signals comprises: The receiving end calculates the eigenvalues ​​of each group of channel matrices according to the channel matrices of the frequency points corresponding to the multiple groups of receiving end pilot signals; The receiving end estimates the mode correlation loss according to the eigenvalues ​​of each group of channel matrices; The receiving end divides any two groups of channel matrices to obtain a corresponding inter-modal matrix, and calculates an eigenvalue of the inter-modal matrix; The receiving end estimates the inter-mode group delay parameter according to the eigenvalue of the inter-mode matrix.

7. A communication parameter monitoring system, characterized in that: The communication parameter monitoring system includes a transmitting end and a receiving end; The transmitting end is used to insert a preset pilot into the information to be transmitted to generate a modulated signal; The transmitting end is used to send the modulated signal to the receiving end, and obtain a received signal after coherent reception; The receiving end is used to perform digital signal processing on the received signal and extract pilot information; The receiving end is further used to calculate the communication parameters between the sending end and the receiving end according to the pilot information.

8. The communication parameter monitoring system according to claim 7, characterized in that: The transmitting end is further used to modulate and shape the information to be transmitted to generate multiple signal acquisition paths; The transmitting end is further used to insert a preset pilot in the polarization dimension of each signal acquisition path to obtain a modulated signal.

9. The communication parameter monitoring system according to claim 7, characterized in that: The receiving end is further used to perform frequency offset compensation on the received signal to obtain a compensated signal; The receiving end is further used to perform down-conversion and narrow-band low-pass filtering on the compensated signal to extract the receiving end pilot signal; The receiving end is further used to construct a multi-dimensional channel response matrix according to the receiving end pilot.

10. The communication parameter monitoring system according to claim 9, characterized in that: The receiving end is further configured to calculate a frequency offset estimation result according to the preset pilot and the receiving end pilot; The receiving end is further used to perform frequency offset compensation on the received signal according to the frequency offset estimation result to obtain a compensated signal.

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