A method, apparatus and system for calibration of inter-transceiver path crosstalk

Abstract

The application discloses a kind of inter-channel crosstalk calibration method, device and system of coherent transceiver, it is related to optical communication technical field.The method comprises: the auxiliary calibration signal generated is loaded on the four-way channel of coherent transmitter and sent to coherent receiver;Wherein, the auxiliary calibration signal generated is inter-channel mutually orthogonal and the multi-carrier frequency signal of sub-carrier frequency amplitude increases with frequency rise;Coherent transmitter receives the crosstalk calibration issued by coherent receiver, carries out frequency-dependent crosstalk compensation based on crosstalk calibration, and sends the calibrated service signal after compensation to coherent receiver;Wherein, crosstalk calibration is the crosstalk value obtained by coherent receiver according to auxiliary calibration signal and based on the frequency-dependent crosstalk measurement of crosstalk angle reconstruction.The present application can solve the technical problems that the existing inter-channel crosstalk calibration technology has high complexity, poor precision and cannot be applied to different rate and modulation format coherent optical modules, meet the actual application demand.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication technology, in particular to a method, device and system for calibrating inter-channel crosstalk of a coherent transceiver. BACKGROUND

[0002] With the rapid deployment and promotion of bandwidth-intensive applications such as AI (Artificial Intelligence), 5G and the Internet of Things, optical coherent transmission is entering the era of single-wavelength channel Tbps (Tera bit per second). With the breakthrough of advanced indium phosphide / thin-film lithium niobate material technology and corresponding integrated packaging technology, the current high-speed coherent transceiver can achieve a bandwidth of up to 70-100GHz or more, and support 400Gbps to Tbps high-speed signal modulation and demodulation. However, although integrated packaging helps to alleviate the connection loss between discrete components and helps to increase the overall module bandwidth, the reduction of optical / electrical circuit trace distance and the compactness of the module size also introduce crosstalk between adjacent channels of the DP-IQ (Dual Polarization-Inphase and Quadrature) branch of the coherent transceiver. That is, the energy of the current channel leaks and superimposes on the adjacent channel, which destroys the original orthogonal characteristics of the four-channel DP-IQ modulation and causes crosstalk. In addition, since the radio frequency signal loss along the transmission line is frequency-dependent, the inter-channel interference also exhibits frequency-dependent characteristics. With the increase of bandwidth, the inter-channel crosstalk of large bandwidth chips may even increase from -40dB to -15dB. Such frequency-dependent crosstalk is difficult to compensate for by traditional DSP (Digital Signal Processing) technology. Therefore, in order to improve the performance of high-speed optical transmission, a wide range and high sensitivity inter-channel crosstalk calibration is needed for high-speed coherent optical transceivers.

[0003] At present, vector instruments such as vector network analyzers are widely used in intensity modulation direct detection systems to correct the crosstalk intensity between adjacent wavelength channels, but cannot be applied to phase modulation demodulation coherent transceivers, and the cost is high. In recent years, some researchers have proposed using a generalized linear MIMO (Multiple Input Multiple Output) equalizer in the DSP chip of the coherent transceiver itself to compensate for the crosstalk between the DP-IQ channels. This solution avoids the use of high-cost instruments, but the complexity is more than twice that of the traditional MIMO equalizer. And the compensation performance of the generalized MIMO equalizer depends largely on the convergence accuracy of the equalizer. In the presence of severe DP-IQ crosstalk or severe frequency-dependent crosstalk or other transceiver impairments, the performance of the equalizer may be greatly reduced, resulting in inaccurate compensation of the crosstalk between the channels.

[0004] In addition, there have been some studies on the calibration of frequency-dependent impairments of coherent transceivers such as channel delay, channel bandwidth response, etc. using multi-tone signals, and such schemes have the characteristics of low complexity and high accuracy, but due to the mutual influence of channel crosstalk and frequency offset phase noise in fiber transmission systems, the energy of the multi-tone signal is mixed multiple times between the DP-IQ branches, making it difficult to demodulate the multi-tone signal and calibrate the crosstalk. Therefore, there is no related multi-tone modulation and demodulation scheme that can solve the channel crosstalk calibration caused by channel energy leakage. At the same time, the existing multi-tone signal-based calibration schemes for impairments other than crosstalk usually use multi-tone signals with equal power at each frequency point, which may have precision loss in the calibration of high-frequency crosstalk, and thus are not suitable for calibration of modules with different bandwidths and modulation formats. SUMMARY

[0005] The present application aims to provide a coherent transceiver inter-channel crosstalk calibration method, device and system for high-precision measurement and compensation of frequency-dependent crosstalk between adjacent channels of a coherent transceiver, solving the technical problems of high complexity, poor precision and inability to be applied to different rate and modulation format coherent optical modules of existing inter-channel crosstalk calibration techniques, and meeting the actual application requirements.

[0006] To achieve the above purpose, in a first aspect, the embodiments of the present application provide a coherent transceiver inter-channel crosstalk calibration method, which comprises:

[0007] The coherent transmitter loads the generated auxiliary calibration signal on the four channels of the coherent transmitter and sends it to the coherent receiver; wherein the generated auxiliary calibration signal is a multi-carrier signal that is orthogonal to each other between channels and has a sub-carrier frequency amplitude that increases with frequency.

[0008] The coherent transmitter receives the crosstalk calibration sent by the coherent receiver, performs frequency-dependent crosstalk compensation based on the crosstalk calibration, and sends the compensated calibration service signal to the coherent receiver; wherein the crosstalk calibration is a crosstalk value obtained by the coherent receiver performing frequency-dependent crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal.

[0009] In combination with the first aspect, in an implementation, the generation of the auxiliary calibration signal comprises:

[0010] Four mutually orthogonal multi-carrier signals are generated; optical module modulation information of the coherent transmitter is obtained, including modulation order, modulation baud rate and sampling rate; a calibration bandwidth is set according to the modulation baud rate; the total number of sub-carrier frequencies of the multi-carrier signal is set according to the modulation order; a sub-carrier frequency interval is set according to the calibration bandwidth and the total number of sub-carrier frequencies; and the amplitude of each sub-carrier frequency is set according to the modulation baud rate, the total number of sub-carrier frequencies and the sampling rate.

[0011] In combination with the first aspect, in an implementation, when the coherent transmitter performs frequency-dependent crosstalk compensation, the following method is used: the crosstalk compensation coefficient is obtained from the crosstalk calibration sent by the coherent receiver, and the compensation depth is adaptively adjusted according to the modulation baud rate and the modulation format, and the compensation depth is reduced for high-order modulation and high-baud signals.

[0012] In combination with the first aspect, in an implementation, the coherent transmitter performs frequency-dependent crosstalk compensation using a preset static MIMO equalizer; the preset static MIMO equalizer is provided with two groups, respectively used for crosstalk compensation of X polarization and Y polarization; each group of static MIMO equalizers is a 2x2 real number MIMO equalizer, the equalizer coefficient is obtained from the crosstalk calibration sent by the coherent receiver, and the compensation depth is adaptively adjusted according to the modulation baud rate and the modulation format, and the compensation depth is reduced for high-order modulation and high-baud signals.

[0013] The second aspect, the embodiment of the present application also provides a kind of calibration method of coherent transceiver inter-channel crosstalk, which comprises:

[0014] The coherent receiver receives the auxiliary calibration signal sent by the coherent transmitter on four channels; wherein the auxiliary calibration signal is a multi-carrier signal that is mutually orthogonal between channels and has sub-carrier frequency amplitude increasing with frequency.

[0015] The coherent receiver performs frequency-dependent crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal, obtains crosstalk calibration, and sends it to the coherent transmitter; wherein the crosstalk calibration is used by the transmitter to perform frequency-dependent crosstalk compensation based on the crosstalk calibration.

[0016] The coherent receiver receives the calibration service signal after crosstalk compensation by the coherent transmitter, and performs equalization demodulation on the calibration service signal.

[0017] In conjunction with the second aspect, in one embodiment, the coherent receiver performs frequency-related crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal to obtain crosstalk calibration, including:

[0018] By introducing a frequency-dependent phase extraction factor α(fn), the preprocessed auxiliary calibration signal is reconstructed into a crosstalk-free signal; where α(fn) is used to extract inter-channel crosstalk and phase deviation caused by laser phase rotation, and to reconstruct a crosstalk-free signal accordingly.

[0019] Select the nth frequency point (n = 1, ..., N), scan α(fn) in the range [0, 2π] to obtain the intensity curve of the subcarrier signal at the nth frequency point of the reconstructed signal; where N is the total number of subcarrier signals in the multi-carrier signal.

[0020] Obtain the phase extraction factor corresponding to the intensity extremum point, denoted as α. max (fn), and the α max (fn) is the sum of the crosstalk angle and the laser phase at that frequency, where the laser phase is a constant;

[0021] The α values ​​at the nth frequency points (n=2, ..., N) are sequentially... max (fn), minus α at the first frequency point max (f1) calculates the crosstalk angle of the subcarrier signal at the nth frequency point, and calculates the corresponding crosstalk value based on the crosstalk angle.

[0022] In conjunction with the second aspect, in one implementation, during the equalization and demodulation of the calibration service signal by the coherent receiver, a 2×2 complex MIMO equalizer is used for polarization demultiplexing equalization.

[0023] Thirdly, embodiments of the present invention also provide a coherent transmitter based on the method in the first aspect embodiment, the coherent transmitter including an auxiliary calibration signal transmission unit and a calibration service signal transmission unit;

[0024] The auxiliary calibration signal transmission unit is used to: load the generated auxiliary calibration signal onto the four channels of the coherent transmitter and transmit it to the coherent receiver; wherein, the generated auxiliary calibration signal is a multi-carrier signal that is mutually orthogonal between channels and whose sub-carrier frequency amplitude increases with frequency.

[0025] The calibration service signal transmission unit is used to: receive crosstalk calibration sent by the coherent receiver, perform frequency-related crosstalk compensation based on the crosstalk calibration, and send the compensated calibration service signal to the coherent receiver; wherein, the crosstalk calibration is the crosstalk value obtained by the coherent receiver through frequency-related crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal.

[0026] In a fourth aspect, the embodiments of the present application further provide a coherent receiver based on the method in the second aspect, which comprises a crosstalk calibration unit and a service signal demodulation unit.

[0027] The crosstalk calibration unit is configured to receive an auxiliary calibration signal sent by the coherent transmitter on four channels, the auxiliary calibration signal being a multi-carrier signal with inter-channel orthogonality and sub-carrier frequency amplitude increasing with frequency, and to perform frequency-dependent crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal to obtain crosstalk calibration and send the crosstalk calibration to the coherent transmitter, wherein the crosstalk calibration is used by the transmitter to perform frequency-dependent crosstalk compensation.

[0028] The service signal demodulation unit is configured to receive the calibrated service signal after crosstalk compensation by the coherent transmitter and to perform equalization demodulation on the calibrated service signal.

[0029] In a fifth aspect, the embodiments of the present application further provide a crosstalk calibration system between channels of a coherent transceiver, which comprises the coherent transmitter of the third aspect and the coherent receiver of the fourth aspect.

[0030] The technical solutions provided by the embodiments of the present application have the following beneficial effects:

[0031] In the embodiments, the coherent transmitter generates an auxiliary calibration signal, which is a multi-carrier signal with inter-channel orthogonality and sub-carrier frequency amplitude increasing with frequency, and can be applied to different application scenarios of channel crosstalk measurement of coherent optical modules. Meanwhile, frequency-dependent crosstalk measurement based on crosstalk angle reconstruction is performed in the coherent receiver, which can realize wide-range, high-precision and low-complexity measurement and calibration of frequency-dependent crosstalk between adjacent channels of the coherent transceiver. Finally, low-complexity frequency-dependent crosstalk compensation is performed in the coherent transmitter based on the measurement and calibration, so as to realize the calibration of the frequency-dependent crosstalk between channels, thereby solving the technical problems of high complexity, poor precision and inapplicability to different rate and modulation format coherent optical modules of the existing channel crosstalk calibration technology, and meeting the actual application requirements. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 FIG. 1 is a flowchart of a first embodiment of the crosstalk calibration method between channels of a coherent transceiver according to the present application;

[0033] Figure 2 FIG. 2 is a specific flowchart of generating an auxiliary calibration signal according to the present application;

[0034] Figure 3 FIG. 3 is a multi-carrier signal spectrum diagram in different scenarios in an example according to the present application;

[0035] Figure 4A schematic diagram of a cross-talk compensation method for compensating cross-talk of X polarization in an example;

[0036] Figure 5 A flowchart of a second embodiment of the method for calibrating inter-channel cross-talk of a coherent transceiver according to the present application;

[0037] Figure 6 A schematic diagram of a specific process for measuring cross-talk according to the present application;

[0038] Figure 7 A schematic diagram of the relationship between the intensity extreme point of different frequency points and max A schematic diagram of the relationship between (fn) and cross-talk;

[0039] Figure 8 A schematic diagram of a conventional equalization and demodulation of a received signal in a coherent receiver according to the present application;

[0040] Figure 9 A schematic diagram of a generalized MIMO equalizer for compensating cross-talk in a coherent receiver according to the prior art;

[0041] Figure 10 A flowchart of a method for calibrating inter-channel cross-talk of a coherent transceiver according to the present application in an example;

[0042] Figure 11 A schematic diagram of the spectrum of a multi-carrier signal in different transmission processes according to the present application;

[0043] Figure 12 A schematic diagram of an architecture of an embodiment of a system for calibrating inter-channel cross-talk of a coherent transceiver according to the present application. DETAILED DESCRIPTION

[0044] To make the technical problems, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] However, it should be noted that the examples to be introduced below are only some specific examples and do not limit the embodiments of the present application to the following specific steps, values, conditions, data, sequences, etc. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0046] Embodiment One

[0047] The embodiments of the present application provide a method for calibrating inter-channel cross-talk of a coherent transceiver. With reference to Figure 1 , Figure 1 A flowchart of a first embodiment of the method for calibrating inter-channel cross-talk of a coherent transceiver according to the present application. As shown in FIG. 1, the method comprises the following steps: Figure 1As shown in the figure, a method for calibrating inter-channel crosstalk of a coherent transceiver includes:

[0048] Step A1, the coherent transmitter loads a generated auxiliary calibration signal on the four channels of the coherent transmitter to send to the coherent receiver; wherein the generated auxiliary calibration signal is a multi-carrier signal that is mutually orthogonal between channels and has a sub-carrier frequency amplitude that increases with frequency;

[0049] Step A2, the coherent transmitter receives a crosstalk calibration issued by the coherent receiver, performs frequency-dependent crosstalk compensation based on the crosstalk calibration, and sends the compensated calibration service signal to the coherent receiver; wherein the crosstalk calibration is a crosstalk value obtained by the coherent receiver from frequency-dependent crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal.

[0050] It can be understood that in the embodiment, the coherent transmitter generates an auxiliary calibration signal, which is a multi-carrier signal that is orthogonal between channels and has a sub-carrier frequency amplitude that increases with frequency. Unlike the prior art, the multi-carrier signal has a difference in amplitude between high-frequency carrier signals and low-frequency carrier signals that increases with modulation order and modulation bit rate, which can be applied to different channel crosstalk measurement scenarios of coherent optical modules.

[0051] Further, referring to Figure 2 As an optional embodiment, in step A1 of the embodiment, the generation of the auxiliary calibration signal includes:

[0052] S201, generate a four-channel multi-carrier signal with mutual orthogonality, the expression of the multi-carrier signal is formula (1) and the sub-carrier frequency contained in the multi-carrier signal satisfies formula (2);

[0053]

[0054] In formula (1), n represents the nth sub-carrier, Amp ab (n) is the amplitude of the nth sub-carrier on the ab branch, f ab (n) is the frequency of the nth sub-carrier, n≤N, N is the total number of sub-carriers, a∈[X, Y], b∈[I, Q];

[0055] f ab (n) = F ab + nf base (2);

[0056] In formula (2), F ab is the initial frequency of the sub-carrier closest to the zero frequency point, f base is the sub-carrier interval.

[0057] It can be understood that four multi-carrier signals with mutual orthogonal relationship will be generated in the embodiment, such as S XI , S XQ , S YI , S YQ The four multi-carrier signals will be input into the four input ports TXI, TXQ, TYI and TYQ of the coherent transmitter respectively. According to the design of the embodiment, F XI , F YI , F XQ , F YQ respectively equal to 0, f base / 4, f base / 2 and 3f base / 4. It can be seen that the sub-carrier frequencies contained in the four multi-carrier signals are not equal to each other, and have the characteristics of mutual orthogonality and non-overlapping.

[0058] S202, obtaining the optical module modulation information of the current coherent transmitter, including the modulation order M, the modulation baud rate f baud and the sampling rate f DAC . It can be understood that the modulation format corresponding to the modulation order M is M-QAM (Quadrature Amplitude Modulation).

[0059] S203, setting the calibration bandwidth f baud according to the modulation baud rate f cal . In actual application, the calibration bandwidth f cal =1.1f baud .

[0060] S204, setting the total number of sub-carriers N of the multi-carrier signal according to the modulation order M. It can be understood that the higher the modulation order is, the more sensitive to crosstalk is. In order to ensure the measurement accuracy, the embodiment designs to select fewer sub-carrier numbers for crosstalk measurement to improve the signal-to-noise ratio of each sub-carrier. Therefore, the total number of sub-carriers N of the multi-carrier signal is set to change with the modulation order M, and the specific setting formula is:

[0061] N = 256 / log2(M) (3);

[0062] S205, setting the sub-carrier spacing f base according to the calibration bandwidth f cal and the total number of sub-carriers N. Similarly, since the total number of sub-carriers N of the multi-carrier signal is set to change with the modulation order M, for the fixed calibration bandwidth, the sub-carrier spacing f base of the multi-carrier signal is also set to change with the modulation order M, and the specific setting formula is:

[0063] f base = f cal / N=1.1f baud log2(M) / 256 (4).

[0064] S206, According to the modulation baud rate f baud Total number of subcarriers N and sampling rate f DAC Set the amplitude Amp of each subcarrier frequency ab (n). It is understandable that since crosstalk between channels often occurs in the high-frequency range, and devices suffer significant energy loss at high frequencies, it is necessary to further design the amplitude of each sub-carrier frequency in a multi-carrier signal to improve the strength of the multi-carrier signal at high frequencies and obtain a higher signal-to-noise ratio. In specific applications, the amplitude of each sub-carrier frequency in the multi-carrier signal can be set as follows:

[0065] Amp ab (n) = 1 + 4nf baud / N / f DAC (5).

[0066] After the above steps, the auxiliary calibration signal (i.e., a multi-carrier signal where the channels are orthogonal and the sub-carrier amplitude increases with frequency) is generated. Furthermore, following this generation method, multi-carrier signals with sub-carrier amplitude varying with frequency can be designed, suitable for application scenarios involving channel crosstalk measurement of coherent optical modules with different rates and modulation formats.

[0067] For example, suppose scenario A uses 16QAM modulation with a modulation rate of 45 Gbaud; and scenario B uses QPSK modulation with a modulation rate of 90 Gbaud. Based on the above generation method, different multi-carrier signals can be designed for the two scenarios. The corresponding parameters are shown in Table 1 below, and the multi-carrier signal spectrum is as follows. Figure 3 As shown:

[0068] Table 1

[0069]

[0070] From the above two examples of multi-carrier signal design, it can be seen that: (1) Scenario A uses 16QAM modulation and Scenario B uses QPSK modulation. Scenario A has a higher modulation format than Scenario B and is more sensitive to crosstalk. The number of carrier frequencies N in the multi-carrier signal design is less, which can improve the signal-to-noise ratio of each carrier frequency and ensure measurement accuracy; (2) Scenario A uses a 45Gbaud modulation rate and Scenario B uses a 90Gbaud modulation rate. Scenario B has a higher modulation rate than Scenario A. The higher the baud rate, the more serious the high-frequency bandwidth loss of the device. The carrier frequency signal located at the high frequency is amplified more, which improves the high-frequency signal-to-noise ratio and ensures the high-frequency measurement accuracy.

[0071] In addition, it can be understood that, in the embodiment, the coherent transmitter performs frequency-dependent crosstalk compensation based on the crosstalk calibration issued by the coherent receiver. Unlike the prior art, the crosstalk compensation method adopted in the embodiment is that the crosstalk compensation coefficient is obtained from the measured frequency-dependent crosstalk value (i.e. the crosstalk calibration issued by the coherent receiver), and the compensation depth can be adaptively adjusted according to the modulation rate and modulation format of the coherent optical module, and the compensation depth is reduced for high-order modulation and high baud signals, thereby solving the problem of PAPR (Peak to Average Ratio) increase and signal-to-noise ratio decrease of the transmitted signal caused by counter compensation, and effectively improving the crosstalk compensation effect.

[0072] Further, as an optional implementation, in step A2 of the embodiment, the coherent transmitter performs frequency-dependent crosstalk compensation based on the crosstalk calibration, which includes: performing frequency-dependent crosstalk compensation on the service signal by using a preset static MIMO equalizer, the preset static MIMO equalizer being provided with two groups of static MIMO equalizers for X polarization and Y polarization crosstalk compensation respectively; each group of static MIMO equalizers is a 2x2 real number MIMO equalizer, and the equalizer coefficient is obtained according to the crosstalk calibration issued by the coherent receiver; and the compensation depth is adaptively adjusted according to the modulation baud rate and modulation format, and the compensation depth is reduced for high-order modulation and high baud signals.

[0073] Exemplarily, referring to Figure 4 , Figure 4 is a schematic diagram of the crosstalk compensation method adopted in the embodiment for X polarization crosstalk compensation. As shown in Figure 4 , the preset static MIMO equalizer is arranged after the static filter equalizer of the coherent transmitter DSP, that is, after the service signal is subjected to QAM modulation, up-sampling, frequency offset shaping, inter-channel time delay compensation, dispersion pre-compensation and other conventional DSP processing in the static equalizer, the service signal is subjected to frequency-dependent crosstalk compensation by the preset static MIMO equalizer, and then enters the iFFT module and the resampling module. As shown in Figure 4 , the preset static MIMO equalizer is composed of a 2x2 real number MIMO equalizer, and the equalizer coefficient is obtained according to the crosstalk calibration issued by the coherent receiver (i.e. the measured frequency-dependent crosstalk angle). Specifically, the calculation formula is shown in formula (6) and formula (7):

[0074] TXI_c(f)=TXI(f)Cos(β2(f))-ATXQ(f)Sin(β1(f)) (6);

[0075] TXQ_c(f)=TXQ(f)Cos(β1(f))-ATXI(f)Sin(β2(f)) (7);

[0076] TXQ(f)Sin(β1(f)) is the Q-to-I crosstalk signal calculated according to the crosstalk calibration angle value, TXI(f)Cos(β2(f)) represents the I-to-Q crosstalk signal after the I-to-Q crosstalk of the I-to-Q crosstalk signal, TXI(f)Sin(β2(f)) is the I-to-Q crosstalk signal calculated according to the crosstalk calibration angle value, TXQ(f)Cos(β1(f)) represents the Q-to-I crosstalk signal after the Q-to-I crosstalk of the Q-to-I crosstalk signal, and A is a compensation depth coefficient, and its expression is:

[0077] A=f DAC / (2f baud ) / (log2(M) / 2)=f DAC / f baud / log2(M) (8)。

[0078] The preset static MIMO equalizer adopts the calculation of formula (6) and formula (7), and can realize the compensation of the frequency-dependent crosstalk between channels; and formula (8) is used for the compensation depth design of channel crosstalk, the compensation depth is adaptively adjusted, the compensation depth of high-order modulation and high baud signals is reduced, and the problems of the PAPR increase and the signal-to-noise ratio reduction of the transmission signal caused by the counter compensation are solved, and the crosstalk compensation effect can be effectively improved.

[0079] Embodiment two

[0080] Based on the same inventive concept, the application also provides a calibration method for crosstalk between channels of a coherent transceiver. Referring to Figure 5 , Figure 5 is a flowchart of the second embodiment of the calibration method for crosstalk between channels of a coherent transceiver. As shown in Figure 5 , the calibration method for crosstalk between channels of a coherent transceiver comprises the following steps:

[0081] Step B1, the coherent receiver receives the auxiliary calibration signal sent by the coherent transmitter on the four-channel; the auxiliary calibration signal is a multi-carrier signal orthogonal to each other between channels and the amplitude of the sub-carrier frequency increases with the increase of the frequency.

[0082] Step B2, the coherent receiver performs frequency-dependent crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal to obtain crosstalk calibration, and delivers the crosstalk calibration to the coherent transmitter; the crosstalk calibration is used for the transmitter to perform frequency-dependent crosstalk compensation based on the crosstalk calibration;

[0083] Step B3, the coherent receiver receives the calibration service signal after the coherent transmitter performs crosstalk compensation, and performs equalization demodulation on the calibration service signal.

[0084] It can be understood that in the embodiment, the coherent receiver will perform frequency-dependent crosstalk measurement based on crosstalk angle reconstruction on the four-way received signal loaded with the auxiliary calibration signal in the digital domain, so as to obtain the crosstalk calibration. This crosstalk measurement based on crosstalk angle reconstruction is a frequency-dependent crosstalk measurement method using crosstalk-free signal reconstruction plus frequency point-by-frequency point crosstalk angle search, which can realize wide-range, high-precision and low-complexity calibration of frequency-dependent crosstalk between IQ channels of the coherent transceiver.

[0085] Further, as shown in Figure 6 As an optional implementation, in step B2 of the embodiment, the coherent receiver performs frequency-dependent crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal to obtain crosstalk calibration, which includes:

[0086] S601, a crosstalk-free signal is reconstructed by introducing a frequency-dependent phase extraction factor α(fn); wherein α(fn) is used to extract the phase deviation caused by inter-channel crosstalk and laser phase rotation, and the crosstalk-free signal is reconstructed based on the phase deviation.

[0087] It can be understood that after the auxiliary calibration signal is transmitted to the coherent receiver through the optical fiber link, the coherent receiver will perform detection to obtain four-way radio frequency signals RXI, RXQ, RYI and RYQ from the four input ports respectively; and the received signal will be preprocessed, such as frequency offset estimation and frequency offset compensation, in a digital signal processing (DSP) module.

[0088] For example, taking the channel crosstalk between RXI and RXQ as an example, before performing crosstalk measurement, the coherent receiver first performs preprocessing of frequency offset estimation and frequency offset compensation on RXI and RXQ. Considering the residual laser phase noise effect and the amplitude frequency response of the transceiver, the two-way signals after preprocessing can be represented as:

[0089]

[0090] Wherein, μ(f) and γ(f) represent the frequency-dependent crosstalk of the coherent transmitter and the coherent receiver respectively, and the inter-channel crosstalk at different fn frequency points is regarded as rotation angles μ(f) and γ(f) according to the law of conservation of energy; θ represents the azimuth angle introduced by the laser phase rotation. An amplitude-phase-frequency response of a transmission channel of a non-coherent optical communication system in the presence of a laser frequency offset.

[0091] As shown in equation (9), due to the transceiver crosstalk and the laser phase rotation effect, the RXI, RXQ signals of the coherent receiver contain the TXI, TXQ signals of the coherent transmitter at the same time, and the two are mixed with each other. Based on the power conservation formula of the frequency-dependent crosstalk, the transceiver crosstalk rotation angle and the laser phase are combined into one term in the model, and it is difficult to separate the crosstalk independently.

[0092] In order to solve the problem that the crosstalk is difficult to separate from the laser phase and measure independently, the embodiment particularly introduces a frequency-dependent phase extraction factor α(fn) for extracting the phase deviation caused by the inter-channel crosstalk and the laser phase rotation, and reconstructs the crosstalk-free signal based on this. Exemplarily, the reconstructed crosstalk-free signal can be written as equation (10):

[0093]

[0094] Since the transmit signals TXI and TXQ are orthogonal to each other in the frequency domain, as shown in the lower part of equation (10), the reconstructed crosstalk-free signal is further written as a function of the transmit signals TXI and TXQ, and does not contain the cross terms of the two. Wherein, M I and M Q are functions of α(fn), θ, μ(f), γ(f).

[0095] S602, select the nth=1,…N frequency point, scan α(fn) in the range of [0, 2π], and obtain the intensity curve of the sub-carrier signal at the nth frequency point of the reconstructed signal.

[0096] Specifically, in actual application, the frequency point fn is fixed, and the phase extraction factor α(fn) is scanned in the range of [0, 2π], and the intensity curve corresponding to the nth sub-carrier signal can be obtained as shown in equation (11):

[0097]

[0098] S603, obtain the phase extraction factor corresponding to the intensity extreme point, denoted as α max (fn); and the α max (fn) is the sum of the crosstalk angle and the laser phase of the frequency point, wherein the laser phase is a constant.

[0099] It can be understood that when Amp_Rx(α(fn)) in equation (11) takes the maximum, the M I and M Q of the nth sub-carrier signal at the frequency point fn reach the intensity extreme point, as shown in equation (12):

[0100]

[0101] At this intensity extreme point, the corresponding phase extraction factor α is obtained. max (fn), the α max (fn) satisfies the relationship between inter-channel crosstalk and phase deviation caused by laser phase rotation as expressed in equation (13):

[0102] α max1 (fn)=θ+γ(f XI,n )+μ(f XI,n ), α max2 (fn)=θ+γ(f XQ,n )+μ(f XQ,n (13).

[0103] S604. Sequentially assign α values ​​at the nth frequency points (n=2,...N) max (fn), minus α at the first frequency point max (f1) eliminates the influence of the laser phase constant, calculates the crosstalk angle of the subcarrier signal at the nth frequency point, and calculates the corresponding crosstalk value based on the crosstalk angle.

[0104] It is understandable that in practical applications, since the phase azimuth angle θ introduced by the laser in equation (13) can be regarded as a constant during the measurement time and recovered by the equalizer in the receiver's DSP, the phase extraction factor α at the first frequency point f1 can be obtained. max1 (f1), α max2 (f1) is taken as a reference value, and the phase extraction factor α at other subcarrier frequencies is used. max1 (fn), α max2 Subtracting the reference value from (fn) yields the crosstalk angles β1 and β2 at different frequencies. The specific calculation formulas are shown in equations (14) and (15):

[0105] β1(f1) = α max1 (f1), β2(f1) = α max2 (f1) (14);

[0106] β1(fn) = α max1 (fn)-α max1 (f1), β2(fn) = α max2 (fn)-α max2 (f1) (15).

[0107] See Figure 7 As shown, Figure 7 For the extreme intensity points at different frequencies, α corresponds to max A diagram illustrating the relationship between (fn) and crosstalk. (See diagram below.)Figure 7 As shown, when there is no frequency-dependent crosstalk at the nth frequency point, the extreme point of the intensity curve calculated in step S603 corresponds to an α max (fn) coincides with the α max (fn) coincides with the α max (fn) coincides with the α max (fn) coincides with the α

[0108] After that, the corresponding crosstalk value can be calculated by the obtained crosstalk angle, so as to realize the frequency-dependent crosstalk calibration in the full bandwidth range. Exemplarily, the crosstalk value calculation formula is as follows:

[0109] XT TRx_IQ (fn) = Sin(β1(fn)) / Cos(β2(fn)) (16);

[0110] XT TRx_QI (fn) = Sin(β2(fn)) / Cos(β1(fn)) (17);

[0111] Wherein, XT TRx_IQ (fn) represents the crosstalk value of the XQ channel to the XI channel, and XT TRx_QI (fn) represents the crosstalk value of the XI channel to the XQ channel.

[0112] Further, referring to Figure 8 As shown, as an optional embodiment, in step B3 of the embodiment, a 2x2 complex MIMO equalizer is used for polarization demultiplexing equalization in the equalization and demodulation process of the coherent receiver, which is different from the inter-channel crosstalk compensation generalized equalizer of the prior art coherent receiver, and has the characteristics of lower complexity.

[0113] Specifically, referring to Figure 8 As shown, in the coherent receiver DSP of the embodiment, a conventional DSP is used for equalization and demodulation of the received signal, that is, after clock recovery, frequency offset recovery and static equalization, only a 2x2 complex MIMO equalizer is used for polarization demultiplexing equalization, so only 4 complex equalizers (equivalent to 8 real equalizers) are needed to realize signal demodulation, plus the 8 static real equalizers (two polarizations, each polarization has a 2x2 real MIMO equalizer) of the coherent transmitter, a total of 16 real equalizers. Although the generalized equalizer can also realize inter-channel crosstalk compensation, it needs to input the received signal and its conjugate signal (conj() represents conjugate) into a 4x4 complex MIMO equalizer for processing in the coherent receiver, as shown inFigure 9 As shown in the table 2, the complexity of the crosstalk compensation scheme of the embodiment is higher than that of the generalized MIMO equalizer crosstalk compensation scheme, and 16 complex equalizers, equivalent to 32 real equalizers, are required, which is twice as complex as the present scheme.

[0114] Table 2

[0115]

[0116] In order to better understand the calibration method of inter-channel crosstalk of the coherent transceiver, the specific content of the calibration method of the present application will be illustrated below in combination with the contents of embodiments one and two and the accompanying drawings.

[0117] Referring to Figure 10 As shown in the table 2, the complexity of the crosstalk compensation scheme of the embodiment is higher than that of the generalized MIMO equalizer crosstalk compensation scheme, and 16 complex equalizers, equivalent to 32 real equalizers, are required, which is twice as complex as the present scheme.

[0118] Step S101, generating an auxiliary calibration signal in the coherent transmitter, the auxiliary calibration signal being a multi-carrier signal with mutually orthogonal channels and sub-carrier amplitudes increasing with frequency, to adapt to the inter-channel crosstalk calibration of optical modules with different rates and modulation formats, the spectrum being as shown in Figure 11 (a). The specific generation process of the auxiliary calibration signal is described in the corresponding content of embodiment one, which will not be repeated here.

[0119] Step S102, loading the generated auxiliary calibration signal on the XI, XQ, YI and YQ channels of the coherent transmitter, for optoelectronic modulation, to obtain a frequency-domain orthogonal multi-carrier signal at the output of the coherent transmitter, the spectrum being as shown in Figure 11 (b). As shown in Figure 11 (b), due to the influence of device bandwidth, the high-frequency power of the original multi-carrier signal with increasing sub-carrier amplitude (power) with frequency may be attenuated, and the example in the figure is that the power is attenuated to the same power at each frequency point; at the same time, due to inter-channel crosstalk, the originally orthogonal sub-carrier components between channels leak to adjacent channels.

[0120] Step S103, transmitting the output multi-carrier signal in the fiber link, and the spectrum being as shown in Figure 11 (c) under the action of polarization rotation and other fiber effects, the originally orthogonal sub-carrier components between channels further leak to adjacent channels and overlap with the inter-channel crosstalk of the transmitter, which is difficult to directly extract and measure.

[0121] Step S104, the coherent receiver coherently detects the polarization multiplexed QAM signal transmitted, and obtains four multi-carrier signals (i.e., four digital domain received signals) XI, XQ, YI and YQ through an analog-to-digital converter, and the spectrum thereof is as shown in the following figure. Figure 11 As shown in (d), the originally orthogonal subcarrier components between channels are further leaked to adjacent channels due to the inter-channel crosstalk of the receiver, and it is difficult to directly extract the measurement due to the overlap of the inter-channel crosstalk caused by the inter-channel crosstalk and the optical field phase rotation of the transmitting end.

[0122] Step S105, the coherent receiver performs frequency-dependent crosstalk measurement based on crosstalk angle reconstruction on the four multi-carrier signals, obtains crosstalk calibration, and delivers the crosstalk calibration to the coherent transmitter. In this step, by using the crosstalk measurement method based on crosstalk angle reconstruction, wide-range, high-precision and low-complexity measurement and calibration of the frequency-dependent crosstalk between the IQ channels of the coherent transceiver can be realized. For details of the frequency-dependent crosstalk measurement based on crosstalk angle reconstruction, refer to the corresponding content described in Embodiment Two, which will not be described here.

[0123] Step S106, the coherent transmitter receives the crosstalk calibration delivered by the coherent receiver, performs frequency-dependent crosstalk compensation based on the crosstalk calibration, and sends the compensated calibration service signal to the coherent receiver. In this step, after receiving the crosstalk calibration delivered by the coherent receiver, the coherent transmitter performs frequency-dependent crosstalk compensation based on the crosstalk calibration to realize the calibration of the frequency-dependent crosstalk between channels. For details of the crosstalk compensation process, refer to the corresponding content described in Embodiment One, which will not be described here.

[0124] Step S107, after receiving the crosstalk-compensated calibration service signal, the coherent receiver performs regular equalization demodulation on the calibration service signal.

[0125] Embodiment Three

[0126] Based on the same inventive concept, the embodiments of the present application also provide a coherent transmitter based on the calibration method of Embodiment One. As shown in Figure 12 The coherent transmitter comprises an auxiliary calibration signal delivery unit and a calibration service signal delivery unit.

[0127] The auxiliary calibration signal delivery unit is configured to load the generated auxiliary calibration signal on the four channels of the coherent transmitter and send it to the coherent receiver. The generated auxiliary calibration signal is a multi-carrier signal with mutually orthogonal channels and increasing subcarrier amplitude with frequency.

[0128] The calibration service signal issuing unit is configured to receive the crosstalk calibration issued by the coherent receiver, perform frequency-dependent crosstalk compensation based on the crosstalk calibration, and send the compensated calibration service signal to the coherent receiver; wherein the crosstalk calibration is a crosstalk value obtained by the coherent receiver from frequency-dependent crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal.

[0129] In addition, it should be noted that the various variations and other specific examples of the aforementioned calibration method for inter-channel crosstalk of the coherent transceiver are also applicable to the coherent transmitter of the present embodiment, and the implementation method of the coherent transmitter in the present embodiment can be clearly understood by the person skilled in the art through the detailed description of the aforementioned method. Therefore, for the sake of brevity of the specification, the implementation method of the coherent transmitter in the present embodiment will not be described in detail here.

[0130] Embodiment Four

[0131] Based on the same inventive concept, the present embodiment also provides a coherent receiver based on the calibration method of the aforementioned embodiment two. As shown in Figure 12 the coherent receiver comprises a crosstalk calibration unit and a service signal demodulation unit.

[0132] The crosstalk calibration unit is configured to receive the auxiliary calibration signal sent by the coherent transmitter on the four channels, wherein the auxiliary calibration signal is a multi-carrier signal with orthogonal channels and increasing sub-carrier amplitudes with frequency; and perform frequency-dependent crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal to obtain crosstalk calibration and issue it to the coherent transmitter; wherein the crosstalk calibration is used by the transmitter to perform frequency-dependent crosstalk compensation based on the crosstalk calibration.

[0133] The service signal demodulation unit is configured to receive the calibration service signal compensated by the coherent transmitter, and perform equalization demodulation on the calibration service signal.

[0134] Similarly, it should be noted that the various variations and other specific examples of the aforementioned calibration method for inter-channel crosstalk of the coherent transceiver are also applicable to the coherent receiver of the present embodiment, and the implementation method of the coherent receiver in the present embodiment can be clearly understood by the person skilled in the art through the detailed description of the aforementioned method. Therefore, for the sake of brevity of the specification, the implementation method of the coherent receiver in the present embodiment will not be described in detail here.

[0135] Embodiment Five

[0136] Based on the same inventive concept, the present embodiment also provides a calibration system for inter-channel crosstalk of a coherent transceiver, as shown in Figure 12 the calibration system comprises the coherent transmitter of the aforementioned embodiment three and the coherent receiver of the aforementioned embodiment four.

[0137] Note: The above sequence numbers of the embodiments of the present application are only for description, not representing advantages and disadvantages of the embodiments.

[0138] The terms "comprise", "comprising", "include", "including", "have", "has", "contain", "containing", "include", "including", "involving", and disjunctive language (e.g., "or", "if", "etc.") are used herein to mean one or more of the stated items, including any items listed after the term, but not excluding others. The term "and / or" means "and" or "or". The terms "comprise", "comprising", "include", "including", "have", "has", "contain", "containing", "include", "including", "involving", and conjunctive language (e.g., "and", "also", "etc.") are used herein to mean one or more of the stated items, including any items listed after the term, but not excluding others.

[0139] In the description of the embodiments of the present application, "exemplary", "for example", "e.g." or "for instance" are used on the basis that a proper meaning of the related words is understood by those skilled in the art to indicate an example, instance, or illustration. Any embodiment or design scheme described as "exemplary", "for example", "e.g." or "for instance" in the embodiments of the present application should not be interpreted as being more preferred or superior to other embodiments or design schemes. In fact, the words "exemplary", "for example", "e.g." or "for instance" are used to present related concepts in a specific way.

[0140] The advantages, benefits, effects, and the like mentioned in the embodiments of the present application are only examples, and are not limiting. It cannot be considered that these advantages, benefits, effects, and the like are necessarily possessed by each of the embodiments of the present application. In addition, the above-described specific details disclosed in the embodiments of the present application are only for the purpose of illustration and understanding, and are not limiting. The above-described specific details do not limit the embodiments of the present application to be necessarily implemented with the above-described specific details.

[0141] The block diagrams of the devices, apparatuses, equipment, systems involved in the embodiments of the present application are only illustrative examples, and are not intended to require or imply that the connection, arrangement, configuration must be as shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, equipment, systems can be connected, arranged, configured in any way. The words "or" and "and" used in the embodiments of the present application refer to the words "and / or", and can be used interchangeably unless the context clearly indicates otherwise. The word "such as" used in the embodiments of the present application refers to the phrase "such as but not limited to", and can be used interchangeably. The terms "first", "second", and "third" and the like are used to distinguish different objects, and do not represent the order of sequence, nor limit the "first", "second", and "third" to be different types.

[0142] Each operation in the embodiments of the present application can be performed by any appropriate means capable of performing the corresponding function. The means can include various hardware and / or software components and / or modules, including but not limited to a circuit or a processor of hardware.

[0143] The methods of embodiments of the application include one or more acts for implementing the methods described above. The methods and / or acts can be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order is specified, the order and / or use of terms can be modified without departing from the scope of the claims.

[0144] Those skilled in the art can make various changes, substitutions and alterations to the techniques described herein without departing from the teachings of the disclosure defined by the appended claims. Moreover, the scope of the claims of this disclosure is not limited to the specific aspects described above. Rather, the scope of the claims of this disclosure is limited solely by the terms of the claims.

[0145] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other aspects without departing from the scope of the application. Thus, the present application is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0146] The above description has been presented for the purpose of illustration and description. Furthermore, this description is not intended to limit embodiments of the application to the forms disclosed herein. Although several example aspects and embodiments have been discussed, those skilled in the art will recognize that certain modifications, substitutions, changes, additions and rearrangements can be made without departing from the scope of the application. And, some of the descriptions of the aspects have not been described in detail in order to avoid obscuring the application.

Claims

1. A method for calibrating inter-channel crosstalk in a coherent transceiver, characterized in that, The method includes: The coherent transmitter loads the generated auxiliary calibration signal onto the four channels of the coherent transmitter and transmits it to the coherent receiver; wherein, the generated auxiliary calibration signal is a multi-carrier signal that is mutually orthogonal between the channels and whose sub-carrier frequency amplitude increases with frequency. The coherent transmitter receives crosstalk calibration data from the coherent receiver, performs frequency-related crosstalk compensation based on the crosstalk calibration, and sends the compensated calibration service signal to the coherent receiver. The crosstalk calibration is a crosstalk value obtained by the coherent receiver through frequency-related crosstalk measurement based on crosstalk angle reconstruction using an auxiliary calibration signal. The coherent receiver performs frequency-related crosstalk measurement based on crosstalk angle reconstruction using the auxiliary calibration signal to obtain the crosstalk calibration, including: By introducing a frequency-related phase extraction factor ( fn The preprocessed auxiliary calibration signal is reconstructed without crosstalk; among which, fn Indicates frequency point, ( fn This is used to extract inter-channel crosstalk and phase deviation caused by laser phase rotation, and to reconstruct a crosstalk-free signal based on this; the nth, ... N Each frequency point, in [0 Scan within range ( fn This yields the intensity curve of the subcarrier signal at the nth frequency point of the reconstructed signal; where, N The total number of sub-carrier frequencies for the multi-carrier signal; obtain the phase extraction factor corresponding to the intensity extrema, denoted as . max ( fn ), and the max ( fn The sum of the crosstalk angle and the laser phase at that frequency point is given, where the laser phase is constant; the values ​​for n=2,… are then added sequentially. N On each frequency point max ( fn ), minus the first frequency point max ( f 1) Calculate the crosstalk angle of the subcarrier signal at the nth frequency point, and calculate the corresponding crosstalk value based on the crosstalk angle.

2. The calibration method for inter-channel crosstalk in a coherent transceiver as described in claim 1, characterized in that, The generation of the auxiliary calibration signal includes: Generate four multi-carrier signals with mutual orthogonal relationships; Obtain the modulation information of the optical module of the coherent transmitter, including modulation order, modulation baud rate, and sampling rate; Set the calibration bandwidth according to the modulation baud rate; The total number of sub-carrier frequencies of the multi-carrier signal is set according to the modulation order; Set the subcarrier frequency spacing according to the calibration bandwidth and the total number of subcarrier frequencies; The amplitude of each subcarrier frequency is set according to the modulation baud rate, the total number of subcarrier frequencies, and the sampling rate.

3. The calibration method for inter-channel crosstalk in a coherent transceiver as described in claim 1, characterized in that, When performing frequency-dependent crosstalk compensation, the coherent transmitter adopts the following method: the crosstalk compensation coefficient is obtained from the crosstalk calibration sent by the coherent receiver, and the compensation depth is adaptively adjusted according to the modulation baud rate and modulation format, and the compensation depth is reduced for high-order modulation and high baud signals.

4. The calibration method for inter-channel crosstalk in a coherent transceiver as described in claim 3, characterized in that: The coherent transmitter uses a preset static MIMO equalizer to compensate for frequency-related crosstalk; the preset static MIMO equalizer is provided in two sets, which are used for X-polarization and Y-polarization crosstalk compensation respectively. Each static MIMO equalizer is a 2×2 real MIMO equalizer. The equalizer coefficients are obtained based on the crosstalk calibration sent by the coherent receiver, and the compensation depth is adaptively adjusted according to the modulation baud rate and modulation format. The compensation depth is reduced for high-order modulation and high-baud signals.

5. A method for calibrating inter-channel crosstalk in a coherent transceiver, characterized in that, The method includes: The coherent receiver receives auxiliary calibration signals transmitted by the coherent transmitter onto four channels; wherein, the auxiliary calibration signals are multi-carrier signals that are mutually orthogonal between channels and whose sub-carrier frequency amplitudes increase with frequency. The coherent receiver performs frequency-related crosstalk measurement based on crosstalk angle reconstruction using the auxiliary calibration signal to obtain crosstalk calibration, and sends it to the coherent transmitter; wherein, the crosstalk calibration is used by the transmitter to perform frequency-related crosstalk compensation based on the crosstalk calibration; the coherent receiver performs frequency-related crosstalk measurement based on crosstalk angle reconstruction using the auxiliary calibration signal to obtain crosstalk calibration, including: By introducing a frequency-related phase extraction factor ( fn The preprocessed auxiliary calibration signal is reconstructed without crosstalk; among which, fn Indicates frequency point, ( fn This is used to extract inter-channel crosstalk and phase deviation caused by laser phase rotation, and to reconstruct a crosstalk-free signal based on this; the nth, ... N Each frequency point, in [0 Scan within range ( fn This yields the intensity curve of the subcarrier signal at the nth frequency point of the reconstructed signal; where, N The total number of sub-carrier frequencies for the multi-carrier signal; obtain the phase extraction factor corresponding to the intensity extrema, denoted as . max ( fn ), and the max ( fn The sum of the crosstalk angle and the laser phase at that frequency point is denoted as , where the laser phase is constant; and so on, for the n=2,… N On each frequency point max ( fn ), minus the first frequency point max ( f 1) Calculate the crosstalk angle of the subcarrier signal at the nth frequency point, and calculate the corresponding crosstalk value based on the crosstalk angle; The coherent receiver receives the calibration service signal after crosstalk compensation by the coherent transmitter and performs equalization and demodulation on the calibration service signal.

6. The calibration method for inter-channel crosstalk in a coherent transceiver as described in claim 5, characterized in that: During the equalization and demodulation of the calibration service signal by the coherent receiver, a 2×2 complex MIMO equalizer is used for polarization demultiplexing equalization.

7. A coherent transmitter based on the method of any one of claims 1 to 4, characterized in that: The coherent transmitter includes an auxiliary calibration signal transmission unit and a calibration service signal transmission unit; The auxiliary calibration signal transmission unit is used to: load the generated auxiliary calibration signal onto the four channels of the coherent transmitter and transmit it to the coherent receiver; wherein, the generated auxiliary calibration signal is a multi-carrier signal that is mutually orthogonal between channels and whose sub-carrier frequency amplitude increases with frequency. The calibration service signal transmission unit is used to: receive crosstalk calibration sent by the coherent receiver, perform frequency-related crosstalk compensation based on the crosstalk calibration, and send the compensated calibration service signal to the coherent receiver; wherein, the crosstalk calibration is the crosstalk value obtained by the coherent receiver through frequency-related crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signal.

8. A coherent receiver based on the method of any one of claims 5 or 6, characterized in that: The coherent receiver includes a crosstalk calibration unit and a service signal demodulation unit; The crosstalk calibration unit is configured to: receive auxiliary calibration signals transmitted from the coherent transmitter onto the four channels, wherein the auxiliary calibration signals are multi-carrier signals that are mutually orthogonal between the channels and whose sub-carrier frequency amplitudes increase with frequency; and perform frequency-related crosstalk measurement based on crosstalk angle reconstruction according to the auxiliary calibration signals to obtain crosstalk calibration, and send it to the coherent transmitter; wherein the crosstalk calibration is used by the transmitter to perform frequency-related crosstalk compensation based on the crosstalk calibration; The service signal demodulation unit is used to: receive the calibration service signal after crosstalk compensation by the coherent transmitter, and perform equalization demodulation on the calibration service signal.

9. A calibration system for inter-channel crosstalk in a coherent transceiver, characterized in that: The system includes the coherent transmitter as described in claim 7 and the coherent receiver as described in claim 8.

Images