Hollow-core optical fiber Kerr effect nonlinear coefficient characterization method, device and equipment and storage medium

Abstract

The invention discloses a hollow-core optical fiber Kerr effect nonlinear coefficient characterization method, device and equipment and a storage medium, and relates to the technical field of optical communication, and the method comprises the steps: receiving a high-order modulation signal transmitted by a to-be-tested hollow-core optical fiber in a transmitting end, and carrying out the demodulation of the high-order modulation signal, and obtaining a high-order demodulation signal; mapping the high-order demodulation signal into a constellation diagram, and determining the nonlinear phase shift of the high-order demodulation signal in the constellation diagram; based on the nonlinear phase shift of the high-order demodulation signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model, determining a Kerr effect nonlinear refractive index coefficient of the to-be-tested hollow-core optical fiber; and based on the Kerr effect nonlinear refractive index coefficient of the to-be-tested hollow-core optical fiber, optimizing the communication performance of the to-be-tested hollow-core optical fiber. Through the mode, the mapping points in the demodulated signal constellation diagram are analyzed to determine the nonlinear phase shift, so that the nonlinear refractive index coefficient of the Kerr effect is accurately calculated by utilizing the nonlinear mathematical model and the nonlinear phase shift.

Description

Technical Field

[0001] The present application relates to the field of optical communication technology, and in particular to a method, device, equipment and storage medium for characterizing the nonlinear coefficient of the Kerr effect of a hollow-core optical fiber. Background Art

[0002] With the rise of technologies and industries such as cloud computing, big data, and artificial intelligence, the demand for ultra-large capacity and ultra-low latency data transmission is growing rapidly. Hollow-core optical fiber, due to its outstanding advantages in low nonlinearity, large communication window, and low loss, can well solve the capacity and latency limit problems of commercial quartz optical fiber from the perspective of physical properties, and has become the mainstream technical means for building the next generation of large-bandwidth and low-latency optical communication systems.

[0003] Nonlinear effects are the main factor limiting the capacity and distance improvement of optical fiber communication systems. Among them, the Kerr effect has the most serious impact on high-speed optical signals. Therefore, in order to give full play to the performance advantages of optical fiber channels, it is necessary to model and characterize the Kerr effect nonlinearity of optical fibers, so as to improve system performance by establishing an adaptive coding modulation equalization method. However, the current measurement method is difficult to accurately measure the Kerr effect nonlinear refractive index coefficient of hollow-core optical fibers.

[0004] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0005] The main purpose of the present application is to provide a method, device, equipment and storage medium for characterizing the nonlinear coefficient of the Kerr effect of a hollow core optical fiber, aiming to solve the technical problem in the prior art that it is difficult to accurately measure the nonlinear refractive index coefficient of the Kerr effect of a hollow core optical fiber.

[0006] To achieve the above object, the present application provides a method for characterizing the nonlinear coefficient of the Kerr effect of a hollow core optical fiber, the method comprising: Receiving a high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, and demodulating the high-order modulated signal to obtain a high-order demodulated signal; Mapping the high-order demodulated signal into a constellation diagram, and determining a nonlinear phase shift of the high-order demodulated signal in the constellation diagram; Determine the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; Based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested, the communication performance of the hollow-core optical fiber to be tested is optimized.

[0007] In one embodiment, a first corresponding relationship among signal strength, effective optical fiber length, Kerr effect nonlinear coefficient and nonlinear phase shift is obtained; Based on the first corresponding relationship, determining a second corresponding relationship between the slope of a fitting curve of signal intensity and nonlinear phase shift, the effective optical fiber length, and the nonlinear coefficient of the Kerr effect; Obtaining a third corresponding relationship between the Kerr effect nonlinear refractive index coefficient, the effective mode field area, the signal light wavelength and the Kerr effect nonlinear coefficient; Based on the second corresponding relationship, converting the third corresponding relationship into a fourth corresponding relationship between the slope of a fitting curve of signal intensity and nonlinear phase shift, an effective mode field area, a signal light wavelength, an effective optical fiber length, a Kerr effect nonlinear coefficient, and a Kerr effect nonlinear refractive index coefficient; Based on the fourth corresponding relationship, the nonlinear mathematical model of the Kerr effect is constructed.

[0008] In one embodiment, the high-order demodulated signal is mapped to a constellation diagram, and a center position of a mapping point of the high-order demodulated signal in the constellation diagram is determined; Determine a rotation angle between the mapping point and the origin based on a center position of the mapping point of the high-order demodulated signal in the constellation diagram; Based on the rotation angle, a nonlinear phase shift of the high-order demodulated signal in a constellation diagram is determined.

[0009] In one embodiment, mapping points of the high-order demodulated signal in the constellation diagram are classified according to signal strength to determine a plurality of mapping groups, wherein the signal strength of the mapping points in each mapping group is the same; Based on the rotation angles of the mapping points in the mapping group, an arithmetic mean of the rotation angles of the mapping group is determined, and the arithmetic mean of the rotation angles of the mapping group is used as the nonlinear phase shift of the mapping points in the mapping group.

[0010] In one embodiment, mapping points of the high-order demodulated signal in the constellation diagram are clustered to determine cluster centers of mapping points of the high-order demodulated signal in the constellation diagram; Based on the position of the cluster center of the mapping point of the high-order demodulated signal in the constellation diagram, the center position of the mapping point of the high-order demodulated signal in the constellation diagram is determined.

[0011] In one embodiment, the high-order modulated signal is obtained by modulating a high-order orthogonal amplitude modulation signal on multiple orthogonal subcarriers, the high-order orthogonal amplitude modulation signal is modulated using a coherent optical orthogonal frequency division multiplexing modulation strategy, and the rate of the orthogonal amplitude modulation signal is greater than the rate of the subcarrier.

[0012] In one embodiment, a total time period is determined based on the number of subcarriers and the time period of the subcarriers; Determine the dispersion length of the hollow-core optical fiber to be tested based on the total time period and the group velocity dispersion parameter of the hollow-core optical fiber to be tested, wherein the improvement factor between the dispersion length of the hollow-core optical fiber to be tested and the single-carrier modulation dispersion length is the square of the number of subcarriers; When the transmission distance of the high-order modulated signal is less than the dispersion length, the steps of receiving the high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, demodulating the high-order modulated signal, and obtaining a high-order demodulated signal are performed.

[0013] In addition, to achieve the above purpose, the present application also proposes a hollow-core optical fiber Kerr effect nonlinear coefficient characterization device, the hollow-core optical fiber Kerr effect nonlinear coefficient characterization device comprising: A demodulation module is used to receive a high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, and demodulate the high-order modulated signal to obtain a high-order demodulated signal; A mapping module, used to map the high-order demodulated signal into a constellation diagram and determine a nonlinear phase shift of the high-order demodulated signal in the constellation diagram; A characterization module, used to determine the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; The optimization module is used to optimize the communication performance of the hollow-core optical fiber to be tested based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested.

[0014] In addition, to achieve the above-mentioned purpose, the present application also proposes a hollow-core fiber Kerr effect nonlinear coefficient characterization device, the hollow-core fiber Kerr effect nonlinear coefficient characterization device includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the hollow-core fiber Kerr effect nonlinear coefficient characterization method as described above.

[0015] In addition, to achieve the above-mentioned purpose, the present invention also proposes a storage medium, which is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect are implemented as described above.

[0016] In addition, to achieve the above-mentioned purpose, the present application also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the steps of the method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect as described above are implemented.

[0017] The present application provides a method for characterizing the nonlinear coefficient of the Kerr effect of a hollow core fiber, receiving a high-order modulation signal transmitted by a hollow core fiber to be tested in a transmitting end, demodulating the high-order modulation signal, and obtaining a high-order demodulated signal; mapping the high-order demodulated signal to a constellation diagram, and determining the nonlinear phase shift of the high-order demodulated signal in the constellation diagram; determining the Kerr effect nonlinear refractive index coefficient of the hollow core fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; optimizing the communication performance of the hollow core fiber to be tested based on the Kerr effect nonlinear refractive index coefficient of the hollow core fiber to be tested. Through the above method, the received modulation signal is demodulated, the constellation diagram damaged by nonlinearity is restored, the mapping points in the constellation diagram are analyzed, and the nonlinear phase shift is determined, so that the Kerr effect nonlinear mathematical model and the nonlinear phase shift are used for fine characterization, and the Kerr effect nonlinear refractive index coefficient is accurately calculated, and then an adaptive coding modulation equalization strategy can be established to improve the communication performance, solving the technical problem that it is difficult to accurately measure the nonlinear refractive index coefficient of the Kerr effect of the hollow core fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0020] Figure 1 This is a flow chart of Embodiment 1 of the hollow-core optical fiber Kerr effect nonlinear coefficient characterization method of the present application; Figure 2 A schematic diagram of the 64QAM modulation constellation mapping relationship of the hollow-core fiber Kerr effect nonlinear coefficient characterization method provided in Example 1 of the present application; Figure 3 A schematic diagram of nonlinear phase shift of a method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect provided in Example 1 of the present application; Figure 4 A schematic diagram of the slope of a fitting curve of the method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect provided in Example 1 of the present application; Figure 5 This is a flow chart of Embodiment 2 of the hollow-core optical fiber Kerr effect nonlinear coefficient characterization method of the present application; Figure 6 This is a flow chart of Embodiment 3 of the hollow-core optical fiber Kerr effect nonlinear coefficient characterization method of the present application; Figure 7 A schematic diagram of the overall architecture of a method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect provided in Example 3 of the present application; Figure 8 A schematic diagram of a DSP at the transmitting end of a method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect provided in Example 3 of the present application; Fig. 9 A schematic diagram of a DSP at a receiving end of a hollow-core optical fiber Kerr effect nonlinear coefficient characterization method provided in Example 3 of the present application; Fig.10 This is a schematic diagram of the module structure of a hollow-core optical fiber Kerr effect nonlinear coefficient characterization device according to an embodiment of the present application; Fig.11 Schematic diagram of the device structure of the hardware operating environment involved in the method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect in the embodiment of the present application.

[0021] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0022] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application and are not used to limit the present application.

[0023] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0024] The main solution of the embodiment of the present application is: receiving a high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, demodulating the high-order modulated signal to obtain a high-order demodulated signal; mapping the high-order demodulated signal to a constellation diagram, and determining the nonlinear phase shift of the high-order demodulated signal in the constellation diagram; determining the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; and optimizing the communication performance of the hollow-core optical fiber to be tested based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested.

[0025] At present, the measurement method used is difficult to accurately measure the Kerr effect nonlinear refractive index coefficient of hollow-core optical fiber.

[0026] The present application provides a solution to demodulate the received modulated signal, restore the constellation diagram damaged by nonlinearity, analyze the mapping points in the constellation diagram, determine the nonlinear phase shift, and use the Kerr effect nonlinear mathematical model and nonlinear phase shift for fine characterization, accurately calculate the Kerr effect nonlinear refractive index coefficient, and then establish an adaptive coding modulation equalization strategy to improve communication performance, solving the technical problem of difficulty in accurately measuring the Kerr effect nonlinear refractive index coefficient of hollow-core optical fiber.

[0027] It should be noted that the execution subject of this embodiment can be a computing service device with data processing, network communication and program running functions, such as a tablet computer, a personal computer, a mobile phone, etc., or an electronic device capable of realizing the above functions, a hollow-core fiber Kerr effect nonlinear coefficient characterization device, etc., and this embodiment does not specifically limit this. The following takes the hollow-core fiber Kerr effect nonlinear coefficient characterization device as an example to illustrate this embodiment and the following embodiments.

[0028] The present invention provides a method for characterizing the nonlinear coefficient of the Kerr effect of a hollow core optical fiber. Figure 1 , Figure 1 This is a flow chart of the first embodiment of the hollow-core optical fiber Kerr effect nonlinear coefficient characterization method of the present application.

[0029] In this embodiment, the method for characterizing the nonlinear coefficient of the hollow core optical fiber Kerr effect includes steps S10 to S40: Step S10, receiving a high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, and demodulating the high-order modulated signal to obtain a high-order demodulated signal; It should be noted that the hollow core optical fiber to be tested is the hollow core optical fiber whose nonlinear coefficient of Kerr effect needs to be measured. The high-order modulated signal is a signal transmitted from the transmitting end to the receiving end through the hollow core optical fiber to be tested, and is obtained by modulating the high-order orthogonal amplitude modulation signal on multiple orthogonal subcarriers. The orthogonal amplitude modulation signal is a high-order QAM (Quadrature Amplitude Modulation) signal, that is, the high-order modulated signal is a modulated high-order QAM signal. This embodiment uses a coherent optical orthogonal frequency division multiplexing modulation strategy to modulate the high-order QAM signal. The coherent optical orthogonal frequency division multiplexing modulation strategy is CO-OFDM (Coherent Optical Orthogonal Frequency Division Multiplexing) technology. At this time, the high-order modulated signal can be considered as a high-order OFDM-QAM signal. In other implementations, intensity modulation direct detection OFDM (Direct Detection Optical Orthogonal Frequency Division Multiplexing, DDO-OFDM) can also be used, and no specific limitation is made to this.

[0030] It can be understood that through CO-OFDM, high-order QAM signals can be modulated on multiple orthogonal low-speed subcarriers, and the rate of the orthogonal amplitude modulation signal is much larger than the rate of the subcarrier, thereby obtaining a larger dispersion length, thereby realizing long-distance measurement of high-order OFDM-QAM signals.

[0031] It should be understood that after receiving the high-order modulated signal at the receiving end, it is demodulated. The signal obtained after demodulation is the high-order demodulated signal. The high-order demodulated signal usually has certain nonlinear damage. If the Kerr effect nonlinear coefficient is calculated directly, it is difficult to guarantee accuracy.

[0032] Step S20, mapping the high-order demodulated signal into a constellation diagram, and determining a nonlinear phase shift of the high-order demodulated signal in the constellation diagram; It should be noted that, in this embodiment, the high-order demodulated signal is mapped into a constellation diagram, and the mapping points in the constellation diagram generally contain symbol information of different amplitudes and different phase combinations. For example, refer to Figure 2 For 64QAM, different mapping points correspond to different positions in the two-dimensional coordinate system, which can be expressed in the form of coordinates as , , a total of 64 mapping points. Affected by the Kerr nonlinear effect, the mapping points in the constellation diagram usually rotate. The rotation angle of the mapping point is the nonlinear phase shift of the mapping point. Figure 3 , mapping points with different signal strengths will experience different degrees of nonlinear phase shift .

[0033] It is understandable that this embodiment needs to determine the nonlinear phase shift of the high-order demodulated signal in the constellation diagram. The center position can be first found in the constellation diagram, and the final nonlinear phase shift can be determined based on the rotation angle between the center position and the origin.

[0034] Step S30, determining the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; It should be noted that the Kerr effect nonlinear mathematical model is the constellation mapping-Kerr nonlinear mathematical model constructed in this embodiment.

[0035] In a feasible implementation, the step of constructing the Kerr effect nonlinear mathematical model may include steps S301 to S303: Step S301, obtaining a first corresponding relationship among signal strength, effective fiber length, Kerr effect nonlinear coefficient and nonlinear phase shift, and determining a second corresponding relationship among the slope of a fitting curve of signal strength and nonlinear phase shift, effective fiber length and Kerr effect nonlinear coefficient based on the first corresponding relationship; It should be noted that the first corresponding relationship between signal intensity, effective fiber length, Kerr effect nonlinear coefficient and nonlinear phase shift is the calculation relationship of nonlinear phase shift. According to nonlinear optical theory, nonlinear phase shift is proportional to signal intensity, as shown below:

[0036]

[0037] In the formula, represents the nonlinear phase shift, Indicates signal strength, Indicates time, represents the Kerr effect nonlinear coefficient, Indicates the effective optical fiber length. The calculation formula for the effective optical fiber length is as follows:

[0038] In the formula, Indicates the effective fiber length, represents the loss coefficient, Indicates the actual length of the hollow-core fiber to be tested.

[0039] In addition, it should be noted that the reference Figure 4 , nonlinear phase shift With signal strength The slope of the curve can be obtained by fitting, that is, the slope of the fitting curve. The second corresponding relationship between the slope of the fitting curve of signal intensity and nonlinear phase shift, the effective fiber length and the Kerr effect nonlinear coefficient is the calculation relationship of the slope of the fitting curve, as shown below:

[0040] In the formula, represents the slope of the fitting curve, represents the Kerr effect nonlinear coefficient, Indicates the effective optical fiber length.

[0041] Step S302, obtaining a third corresponding relationship between the Kerr effect nonlinear refractive index coefficient, the effective mode field area, the signal light wavelength and the Kerr effect nonlinear coefficient, and based on the second corresponding relationship, converting the third corresponding relationship into a fourth corresponding relationship between the slope of a fitting curve of signal intensity and nonlinear phase shift, the effective mode field area, the signal light wavelength, the effective optical fiber length, the Kerr effect nonlinear coefficient and the Kerr effect nonlinear refractive index coefficient; It should be noted that the third corresponding relationship between the Kerr effect nonlinear refractive index coefficient, the effective mode field area, the signal light wavelength and the Kerr effect nonlinear coefficient, that is, the calculation relationship of the Kerr nonlinear coefficient, is as follows:

[0042] In the formula, represents the Kerr effect nonlinear refractive index coefficient, It represents the effective mode field area of ​​the hollow core fiber to be tested. represents the wavelength of the signal light of the high-order demodulated signal, represents the nonlinear coefficient of the Kerr effect. Thus, the following calculation relationship can be obtained:

[0043] Furthermore, according to By deducing, the fourth corresponding relationship between the slope of the fitting curve of signal intensity and nonlinear phase shift, the effective mode field area, the signal light wavelength, the effective fiber length, the Kerr effect nonlinear coefficient and the Kerr effect nonlinear refractive index coefficient can be obtained as shown below:

[0044] In the formula, represents the Kerr effect nonlinear refractive index coefficient, It represents the effective mode field area of ​​the hollow core fiber to be tested. represents the wavelength of the signal light of the high-order demodulated signal, represents the slope of the fitting curve, Indicates the effective optical fiber length.

[0045] Step S303: constructing the Kerr effect nonlinear mathematical model based on the fourth corresponding relationship.

[0046] It can be understood that the Kerr effect nonlinear mathematical model is constructed based on the fourth corresponding relationship between the slope of the fitting curve of signal intensity and nonlinear phase shift, the effective mode field area, the signal light wavelength, the effective optical fiber length, the Kerr effect nonlinear coefficient and the Kerr effect nonlinear refractive index coefficient.

[0047] It should be understood that by substituting the nonlinear phase shift of the high-order demodulated signal in the constellation diagram into the nonlinear mathematical model of the Kerr effect, the Kerr effect nonlinear refractive index coefficient of the hollow-core fiber to be tested can be calculated. .

[0048] In addition to the nonlinear phase shift, other parameters required in the model can be obtained by characterizing the hollow core fiber to be tested, such as effective fiber length and effective mode field area. In addition, the wavelength of the signal light of the high-order modulation signal can be adjusted, and multiple measurements can be performed, and the average value of multiple measurements can be used as the final Kerr effect nonlinear refractive index coefficient to reduce the measurement error.

[0049] Step S40: optimizing the communication performance of the hollow-core optical fiber to be tested based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested.

[0050] It should be noted that after the characterization of the nonlinear coefficient of the hollow core optical fiber Kerr effect to be tested is completed, the communication performance can be improved by establishing an adaptive coding modulation equalization strategy.

[0051] This embodiment provides a method for characterizing the nonlinear coefficient of the Kerr effect of a hollow core fiber, receiving a high-order modulated signal transmitted by a hollow core fiber to be tested in a transmitting end, demodulating the high-order modulated signal to obtain a high-order demodulated signal; mapping the high-order demodulated signal to a constellation diagram, and determining the nonlinear phase shift of the high-order demodulated signal in the constellation diagram; determining the Kerr effect nonlinear refractive index coefficient of the hollow core fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; optimizing the communication performance of the hollow core fiber to be tested based on the Kerr effect nonlinear refractive index coefficient of the hollow core fiber to be tested. In the above manner, the received modulated signal is demodulated, the constellation diagram damaged by nonlinearity is restored, the mapping points in the constellation diagram are analyzed, and the nonlinear phase shift is determined, so that the Kerr effect nonlinear mathematical model and the nonlinear phase shift are used for fine characterization, and the Kerr effect nonlinear refractive index coefficient is accurately calculated, and then an adaptive coding modulation equalization strategy can be established to improve communication performance.

[0052] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar contents as those in the above-mentioned embodiment 1 can refer to the above introduction, and will not be repeated later. Figure 5 , step S20 may include steps S201 to S203: Step S201, mapping the high-order demodulated signal to a constellation diagram, and determining the center position of the mapping point of the high-order demodulated signal in the constellation diagram; In a feasible implementation, step S201 includes: clustering the mapping points of the high-order demodulation signal in the constellation diagram to determine the clustering center of the mapping points of the high-order demodulation signal in the constellation diagram; based on the position of the clustering center of the mapping points of the high-order demodulation signal in the constellation diagram, determining the center position of the mapping points of the high-order demodulation signal in the constellation diagram.

[0053] It is understandable that this embodiment uses a clustering algorithm to analyze the mapping points in the constellation diagram to determine the cluster center, thereby finding the center position of the mapping points in the constellation diagram. The clustering algorithm can use a K-means clustering algorithm, or other suitable clustering methods, or a deep learning algorithm, a genetic algorithm, which is not specifically limited. This embodiment uses a K-means clustering algorithm, which does not increase the complexity of the DSP.

[0054] Step S202, determining a rotation angle between the mapping point and the origin based on the center position of the mapping point of the high-order demodulated signal in the constellation diagram; It should be noted that, according to the center position of the mapping point in the constellation diagram, the rotation angle of the mapping point relative to the origin can be obtained.

[0055] Step S203: determining a nonlinear phase shift of the high-order demodulated signal in a constellation diagram based on the rotation angle.

[0056] In a feasible implementation, step S203 includes: classifying the mapping points of the high-order demodulated signal in the constellation diagram according to signal strength, determining multiple mapping groups, and the signal strength of the mapping points in each mapping group is the same; based on the rotation angle of the mapping points in the mapping group, determining the arithmetic mean of the rotation angle of the mapping group, and using the arithmetic mean of the rotation angle of the mapping group as the nonlinear phase shift of the mapping points in the mapping group.

[0057] It should be noted that, in this embodiment, mapping points are classified according to signal strength, and mapping points with the same signal strength are grouped together. A group of mapping points is a mapping group, and multiple mapping groups can be obtained, and the signal strengths of the mapping points in the mapping groups are the same. The arithmetic mean of the rotation angle is the arithmetic mean of the rotation angle, and the arithmetic mean of the rotation angles of all mapping points in the mapping group is used as the nonlinear phase shift of the mapping group, thereby reducing the influence of sampling changes.

[0058] The present embodiment provides a method for characterizing the nonlinear coefficient of the Kerr effect in a hollow core optical fiber, which maps a high-order demodulated signal to a constellation diagram, determines the center position of a mapping point of the high-order demodulated signal in the constellation diagram; determines the rotation angle between the mapping point and the origin based on the center position of the mapping point of the high-order demodulated signal in the constellation diagram; determines the nonlinear phase shift of the high-order demodulated signal in the constellation diagram based on the rotation angle, and accurately determines the center position of the mapping point through clustering, and accurately calculates the nonlinear phase shift, so that the nonlinear mathematical model of the Kerr effect and the nonlinear phase shift can be used for fine characterization, and the nonlinear refractive index coefficient of the Kerr effect can be accurately calculated, and then an adaptive coding modulation equalization strategy can be established to improve communication performance.

[0059] Based on the first embodiment of the present application, in the third embodiment of the present application, the same or similar contents as those in the above embodiment can refer to the above introduction, and will not be repeated later. Figure 6 , before step S10, steps S01 to S03 may be included: Step S01, determining a total time period based on the number of the subcarriers and the time period of the subcarriers; It should be noted that fiber dispersion is one of the channel damage phenomena that cannot be ignored in optical communication systems. Its impact is related to the signal rate. The calculation expression of dispersion length is:

[0060] In the formula, It represents the time period of the high-order modulation signal, and its reciprocal corresponds to the baud rate of the high-order modulation signal. It represents the group velocity dispersion parameter. The group velocity dispersion value of hollow-core fiber is about one-sixth of that of quartz fiber.

[0061] It is understandable that when the actual fiber transmission distance When the actual fiber transmission distance is When the signal transmission is greatly affected by dispersion, the Kerr nonlinear coefficient cannot be characterized based on signal distortion (nonlinear phase shift) in this case.

[0062] Therefore, this embodiment modulates the high-order QAM signal on multiple orthogonal low-speed subcarriers. subcarriers, for modulation For a high-order modulation signal with multiple subcarriers, the time period , It represents the time period of each subcarrier, so that the total time period, that is, the total time period, can be calculated according to the number of subcarriers and the time period of the subcarriers as the time period of the high-order modulation signal.

[0063] Step S02, determining the dispersion length of the hollow-core optical fiber to be tested based on the total time period and the group velocity dispersion parameter of the hollow-core optical fiber to be tested, wherein the improvement factor between the dispersion length of the hollow-core optical fiber to be tested and the single-carrier modulation dispersion length is the square of the number of subcarriers; It should be noted that, according to the total time period and the group velocity dispersion parameter of the hollow-core optical fiber to be tested, the dispersion length of the hollow-core optical fiber to be tested is calculated. At this time, compared with the single-carrier modulation dispersion length, the dispersion length of the hollow-core optical fiber to be tested in this embodiment can be improved. It can be seen that the increase factor is the square of the number of subcarriers, which can effectively increase the measurement length.

[0064] Step S03, when the transmission distance of the high-order modulated signal is less than the dispersion length, execute the step of receiving the high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, demodulating the high-order modulated signal, and obtaining a high-order demodulated signal.

[0065] It can be understood that when the transmission distance of the high-order modulated signal is less than the dispersion length, steps S10 to S40 are performed to characterize the Kerr effect nonlinear coefficient of the hollow-core optical fiber to be measured. times.

[0066] Furthermore, the transmitter can add a cyclic prefix (CP) to the signal to prevent inter-symbol interference caused by channel dispersion.

[0067] This embodiment provides a method for characterizing the nonlinear coefficient of the Kerr effect of a hollow core fiber, which modulates a high-order QAM signal on multiple orthogonal low-speed subcarriers to obtain a larger dispersion length, thereby achieving long-distance measurement of high-order OFDM-QAM signals.

[0068] For example, in order to help understand the implementation process of the hollow-core fiber Kerr effect nonlinear coefficient characterization method obtained by combining this embodiment with the above-mentioned embodiment 3, please refer to Figure 7 , Figure 7 A schematic diagram of the overall architecture of a hollow-core fiber Kerr effect nonlinear coefficient characterization method is provided, specifically: By adjusting the value of the variable optical attenuator (VOA) at the transmitting end, the optical power of the fiber can be changed to better stimulate the nonlinear effect. The OFDM baseband signal is generated in the digital signal processing (DSP). Figure 8 The serial bit stream input by the transmitter is first converted into multiple parallel data streams through serial / parallel conversion. Each data stream is mapped according to QAM modulation. The mapped data is padded with zeros to construct a protection band. Then, an inverse Fourier transform (IFFT) is performed to add a cyclic prefix to the time domain OFDM signal to prevent inter-symbol interference caused by channel dispersion. After the serial / parallel conversion, it is converted into an analog signal, i.e., a baseband OFDM signal, through an arbitrary waveform generator (AWG). The transmitter uses a continuously tunable laser plus an IQ modulator to modulate the electrical signal to be transmitted into the optical field. After the modulated optical signal passes through an optical amplifier, it enters the hollow-core optical fiber transmission link to be tested. The received optical signal is converted into an analog electrical signal through a coherent receiver, and finally sampled into a digital signal by a real-time oscilloscope and further processed by DSP. Reference Fig. 9 The processing flow of the high-order modulated signal received by the receiving end includes synchronization, phase noise compensation, serial-to-parallel conversion, CP removal, FFT, demodulation and QAM mapping, etc. According to the constellation mapping relationship after demodulation, the center position of each mapping point is characterized, and finally the Kerr nonlinear refractive index coefficient of the hollow-core fiber to be tested is calculated. At the same time, the link and DSP parameters can be optimized according to the output signal quality (such as signal-to-noise ratio and bit error rate) to obtain the best state.

[0069] It should be noted that the above examples are only used to understand the present application and do not constitute a limitation on the method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect of the present application. More simple transformations based on this technical concept are all within the scope of protection of the present application.

[0070] The present application also provides a hollow-core optical fiber Kerr effect nonlinear coefficient characterization device, please refer to Fig.10 , the hollow core fiber Kerr effect nonlinear coefficient characterization device includes: The demodulation module 10 is used to receive a high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, and demodulate the high-order modulated signal to obtain a high-order demodulated signal.

[0071] The mapping module 20 is used to map the high-order demodulated signal into a constellation diagram and determine the nonlinear phase shift of the high-order demodulated signal in the constellation diagram.

[0072] The characterization module 30 is used to determine the Kerr effect nonlinear refractive index coefficient of the hollow core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and the pre-constructed Kerr effect nonlinear mathematical model.

[0073] The optimization module 40 is used to optimize the communication performance of the hollow-core optical fiber to be tested based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested.

[0074] In a feasible implementation manner, the characterization module 30 is further used to obtain a first corresponding relationship between signal strength, effective optical fiber length, Kerr effect nonlinear coefficient and nonlinear phase shift; Based on the first corresponding relationship, determining a second corresponding relationship between the slope of a fitting curve of signal intensity and nonlinear phase shift, the effective optical fiber length, and the nonlinear coefficient of the Kerr effect; Obtaining a third corresponding relationship between the Kerr effect nonlinear refractive index coefficient, the effective mode field area, the signal light wavelength and the Kerr effect nonlinear coefficient; Based on the second corresponding relationship, converting the third corresponding relationship into a fourth corresponding relationship between the slope of a fitting curve of signal intensity and nonlinear phase shift, an effective mode field area, a signal light wavelength, an effective optical fiber length, a Kerr effect nonlinear coefficient, and a Kerr effect nonlinear refractive index coefficient; Based on the fourth corresponding relationship, the nonlinear mathematical model of the Kerr effect is constructed.

[0075] In a feasible implementation manner, the mapping module 20 is further used to map the high-order demodulated signal to a constellation diagram, and determine the center position of a mapping point of the high-order demodulated signal in the constellation diagram; Determine a rotation angle between the mapping point and the origin based on a center position of the mapping point of the high-order demodulated signal in the constellation diagram; Based on the rotation angle, a nonlinear phase shift of the high-order demodulated signal in a constellation diagram is determined.

[0076] In a feasible implementation manner, the mapping module 20 is further used to classify the mapping points of the high-order demodulated signal in the constellation diagram according to the signal strength, and determine a plurality of mapping groups, wherein the signal strength of the mapping points in each mapping group is the same; Based on the rotation angles of the mapping points in the mapping group, an arithmetic mean of the rotation angles of the mapping group is determined, and the arithmetic mean of the rotation angles of the mapping group is used as the nonlinear phase shift of the mapping points in the mapping group.

[0077] In a feasible implementation manner, the mapping module 20 is further used to cluster the mapping points of the high-order demodulated signal in the constellation diagram to determine the clustering center of the mapping points of the high-order demodulated signal in the constellation diagram; Based on the position of the cluster center of the mapping point of the high-order demodulated signal in the constellation diagram, the center position of the mapping point of the high-order demodulated signal in the constellation diagram is determined.

[0078] In a feasible implementation manner, the high-order modulated signal is obtained by modulating a high-order orthogonal amplitude modulation signal on multiple orthogonal subcarriers, the high-order orthogonal amplitude modulation signal is modulated using a coherent optical orthogonal frequency division multiplexing modulation strategy, and the rate of the orthogonal amplitude modulation signal is greater than the rate of the subcarrier.

[0079] In a feasible implementation manner, the demodulation module 10 is further configured to determine a total time period based on the number of the subcarriers and the time period of the subcarriers; Determine the dispersion length of the hollow-core optical fiber to be tested based on the total time period and the group velocity dispersion parameter of the hollow-core optical fiber to be tested, wherein the improvement factor between the dispersion length of the hollow-core optical fiber to be tested and the single-carrier modulation dispersion length is the square of the number of subcarriers; When the transmission distance of the high-order modulated signal is less than the dispersion length, the steps of receiving the high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, demodulating the high-order modulated signal, and obtaining a high-order demodulated signal are performed.

[0080] The hollow-core fiber Kerr effect nonlinear coefficient characterization device provided by the present application adopts the hollow-core fiber Kerr effect nonlinear coefficient characterization method in the above-mentioned embodiment, which can solve the technical problem that it is difficult to accurately measure the hollow-core fiber Kerr effect nonlinear refractive index coefficient. Compared with the prior art, the beneficial effects of the hollow-core fiber Kerr effect nonlinear coefficient characterization device provided by the present application are the same as the beneficial effects of the hollow-core fiber Kerr effect nonlinear coefficient characterization method provided by the above-mentioned embodiment, and other technical features in the hollow-core fiber Kerr effect nonlinear coefficient characterization device are the same as the features disclosed in the above-mentioned embodiment method, which will not be repeated here.

[0081] The present application provides a hollow-core optical fiber Kerr effect nonlinear coefficient characterization device, the hollow-core optical fiber Kerr effect nonlinear coefficient characterization device comprising: at least one processor; and a memory connected to the at least one processor in communication; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the hollow-core optical fiber Kerr effect nonlinear coefficient characterization method in the above-mentioned embodiment 1.

[0082] Reference below Fig.11 , which shows a schematic diagram of the structure of a hollow-core fiber Kerr effect nonlinear coefficient characterization device suitable for implementing the embodiment of the present application. The hollow-core fiber Kerr effect nonlinear coefficient characterization device in the embodiment of the present application may include but is not limited to mobile terminals such as mobile phones, laptop computers, digital broadcast receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Descriptions), PMPs (Portable Media Players), vehicle-mounted terminals (such as vehicle-mounted navigation terminals), etc., and fixed terminals such as digital TVs, desktop computers, etc. Fig.11 The hollow-core optical fiber Kerr effect nonlinear coefficient characterization device shown is only an example and should not bring any limitation to the function and scope of use of the embodiments of the present application.

[0083] like Fig.11As shown, the hollow-core fiber Kerr effect nonlinear coefficient characterization device may include a processing device 1001 (such as a central processing unit, a graphics processor, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM: Read Only Memory) 1002 or a program loaded from a storage device 1003 to a random access memory (RAM: Random Access Memory) 1004. Various programs and data required for the operation of the hollow-core fiber Kerr effect nonlinear coefficient characterization device are also stored in RAM1004. The processing device 1001, ROM1002 and RAM1004 are connected to each other through a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to the I / O interface 1006: input devices 1007 including, for example, a touch screen, a touchpad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; storage devices 1003 including, for example, a magnetic tape, a hard disk, etc.; and communication devices 1009. The communication device 1009 can allow the hollow-core fiber Kerr effect nonlinear coefficient characterization device to communicate wirelessly or wired with other devices to exchange data. Although the hollow-core fiber Kerr effect nonlinear coefficient characterization device with various systems is shown in the figure, it should be understood that it is not required to implement or have all the systems shown. More or fewer systems may be implemented or have instead.

[0084] In particular, according to the embodiments disclosed in the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, the embodiments disclosed in the present application include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through a communication device, or installed from a storage device 1003, or installed from a ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the method of the embodiment disclosed in the present application are executed.

[0085] The hollow-core fiber Kerr effect nonlinear coefficient characterization device provided by the present application adopts the hollow-core fiber Kerr effect nonlinear coefficient characterization method in the above-mentioned embodiment, which can solve the technical problem that it is difficult to accurately measure the hollow-core fiber Kerr effect nonlinear refractive index coefficient. Compared with the prior art, the beneficial effects of the hollow-core fiber Kerr effect nonlinear coefficient characterization device provided by the present application are the same as the beneficial effects of the hollow-core fiber Kerr effect nonlinear coefficient characterization method provided by the above-mentioned embodiment, and other technical features in the hollow-core fiber Kerr effect nonlinear coefficient characterization device are the same as the features disclosed in the previous embodiment method, which will not be repeated here.

[0086] It should be understood that the various parts disclosed in this application can be implemented by hardware, software, firmware or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0087] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0088] The present application provides a computer-readable storage medium having computer-readable program instructions (ie, computer programs) stored thereon, and the computer-readable program instructions are used to execute the hollow-core optical fiber Kerr effect nonlinear coefficient characterization method in the above-mentioned embodiment.

[0089] The computer-readable storage medium provided in the present application may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, systems or devices, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM: Random Access Memory), a read-only memory (ROM: Read Only Memory), an erasable programmable read-only memory (EPROM: Erasable Programmable Read Only Memory or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM: CD-Read Only Memory), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, system or device. The program code contained on the computer-readable storage medium may be transmitted using any appropriate medium, including but not limited to: wires, optical cables, RF (Radio Frequency: Radio Frequency), etc., or any suitable combination of the above.

[0090] The computer-readable storage medium may be included in the hollow-core optical fiber Kerr effect nonlinear coefficient characterization device; or may exist independently without being assembled into the hollow-core optical fiber Kerr effect nonlinear coefficient characterization device.

[0091] The computer-readable storage medium carries one or more programs. When the one or more programs are executed by the hollow-core optical fiber Kerr effect nonlinear coefficient characterization device, the hollow-core optical fiber Kerr effect nonlinear coefficient characterization device: receives a high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, demodulates the high-order modulated signal, and obtains a high-order demodulated signal; maps the high-order demodulated signal to a constellation diagram, and determines the nonlinear phase shift of the high-order demodulated signal in the constellation diagram; determines the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; and optimizes the communication performance of the hollow-core optical fiber to be tested based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested.

[0092] Computer program code for performing the operations of the present application may be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0093] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present application. In this regard, each square box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the square box can also occur in a sequence different from that marked in the accompanying drawings. For example, two square boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each square box in the block diagram and / or flow chart, and the combination of the square boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0094] The modules involved in the embodiments described in this application may be implemented by software or hardware, wherein the name of the module does not constitute a limitation on the unit itself in some cases.

[0095] The readable storage medium provided in the present application is a computer-readable storage medium, which stores computer-readable program instructions (i.e., computer programs) for executing the above-mentioned hollow-core fiber Kerr effect nonlinear coefficient characterization method, and can solve the technical problem that it is difficult to accurately measure the hollow-core fiber Kerr effect nonlinear refractive index coefficient. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided in the present application are the same as the beneficial effects of the hollow-core fiber Kerr effect nonlinear coefficient characterization method provided in the above-mentioned embodiment, and will not be repeated here.

[0096] The present application also provides a computer program product, including a computer program, which implements the steps of the above-mentioned hollow-core optical fiber Kerr effect nonlinear coefficient characterization method when executed by a processor.

[0097] The computer program product provided by the present application can solve the technical problem that it is difficult to accurately measure the nonlinear refractive index coefficient of the hollow-core optical fiber Kerr effect. Compared with the prior art, the beneficial effects of the computer program product provided by the present application are the same as the beneficial effects of the hollow-core optical fiber Kerr effect nonlinear coefficient characterization method provided by the above embodiment, and will not be repeated here.

[0098] The above are only some embodiments of the present application, and are not intended to limit the patent scope of the present application. All equivalent structural changes made using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A method for characterizing the nonlinear coefficient of the Kerr effect of a hollow core optical fiber, characterized in that: The method comprises: Receiving a high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, and demodulating the high-order modulated signal to obtain a high-order demodulated signal; Mapping the high-order demodulated signal into a constellation diagram, and determining a nonlinear phase shift of the high-order demodulated signal in the constellation diagram; Determine the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; Based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested, the communication performance of the hollow-core optical fiber to be tested is optimized.

2. The method according to claim 1, characterized in that Before the step of determining the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and the pre-constructed Kerr effect nonlinear mathematical model, the step further includes: Obtaining a first corresponding relationship between signal intensity, effective optical fiber length, Kerr effect nonlinear coefficient and nonlinear phase shift; Based on the first corresponding relationship, determining a second corresponding relationship between the slope of a fitting curve of signal intensity and nonlinear phase shift, the effective optical fiber length, and the nonlinear coefficient of the Kerr effect; Obtaining a third corresponding relationship between the Kerr effect nonlinear refractive index coefficient, the effective mode field area, the signal light wavelength and the Kerr effect nonlinear coefficient; Based on the second corresponding relationship, converting the third corresponding relationship into a fourth corresponding relationship between the slope of a fitting curve of signal intensity and nonlinear phase shift, an effective mode field area, a signal light wavelength, an effective optical fiber length, a Kerr effect nonlinear coefficient, and a Kerr effect nonlinear refractive index coefficient; Based on the fourth corresponding relationship, the nonlinear mathematical model of the Kerr effect is constructed.

3. The method according to claim 1, characterized in that The step of mapping the high-order demodulated signal into a constellation diagram and determining the nonlinear phase shift of the high-order demodulated signal in the constellation diagram comprises: Mapping the high-order demodulated signal to a constellation diagram, and determining a center position of a mapping point of the high-order demodulated signal in the constellation diagram; Determine a rotation angle between the mapping point and the origin based on a center position of the mapping point of the high-order demodulated signal in the constellation diagram; Based on the rotation angle, a nonlinear phase shift of the high-order demodulated signal in a constellation diagram is determined.

4. The method according to claim 3, characterized in that The step of determining the nonlinear phase shift of the high-order demodulated signal in the constellation diagram based on the rotation angle comprises: Classifying the mapping points of the high-order demodulated signal in the constellation diagram according to signal strength, and determining a plurality of mapping groups, wherein the signal strength of the mapping points in each mapping group is the same; Based on the rotation angles of the mapping points in the mapping group, an arithmetic mean of the rotation angles of the mapping group is determined, and the arithmetic mean of the rotation angles of the mapping group is used as the nonlinear phase shift of the mapping points in the mapping group.

5. The method according to claim 3, characterized in that The step of mapping the high-order demodulated signal to a constellation diagram and determining the center position of a mapping point of the high-order demodulated signal in the constellation diagram comprises: Clustering mapping points of the high-order demodulated signal in the constellation diagram to determine cluster centers of mapping points of the high-order demodulated signal in the constellation diagram; Based on the position of the cluster center of the mapping point of the high-order demodulated signal in the constellation diagram, the center position of the mapping point of the high-order demodulated signal in the constellation diagram is determined.

6. The method according to any one of claims 1 to 5, characterized in that The high-order modulated signal is obtained by modulating a high-order orthogonal amplitude modulation signal on multiple orthogonal subcarriers. The high-order orthogonal amplitude modulation signal is modulated using a coherent optical orthogonal frequency division multiplexing modulation strategy. The rate of the orthogonal amplitude modulation signal is greater than the rate of the subcarriers.

7. The method according to claim 6, characterized in that The method further comprises: Determining a total time period based on the number of the subcarriers and the time period of the subcarriers; Determine the dispersion length of the hollow-core optical fiber to be tested based on the total time period and the group velocity dispersion parameter of the hollow-core optical fiber to be tested, wherein the improvement factor between the dispersion length of the hollow-core optical fiber to be tested and the single-carrier modulation dispersion length is the square of the number of subcarriers; When the transmission distance of the high-order modulated signal is less than the dispersion length, the steps of receiving the high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, demodulating the high-order modulated signal, and obtaining a high-order demodulated signal are performed.

8. A hollow-core optical fiber Kerr effect nonlinear coefficient characterization device, characterized in that: The device comprises: A demodulation module is used to receive a high-order modulated signal transmitted by the hollow-core optical fiber to be tested in the transmitting end, and demodulate the high-order modulated signal to obtain a high-order demodulated signal; A mapping module, used to map the high-order demodulated signal into a constellation diagram and determine a nonlinear phase shift of the high-order demodulated signal in the constellation diagram; A characterization module, used to determine the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulated signal in the constellation diagram and a pre-constructed Kerr effect nonlinear mathematical model; The optimization module is used to optimize the communication performance of the hollow-core optical fiber to be tested based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber to be tested.

9. A hollow-core optical fiber Kerr effect nonlinear coefficient characterization device, characterized in that: The device comprises: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect according to any one of claims 1 to 7.

10. A storage medium, characterized in that: The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the method for characterizing the nonlinear coefficient of the hollow-core optical fiber Kerr effect as described in any one of claims 1 to 7 are implemented.

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