Methods, apparatus, equipment, and storage media for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber.

Abstract

The application discloses a kind of hollow-core fiber kerr effect nonlinear coefficient measurement method, device, equipment and storage medium, it is related to optical communication technical field, the method comprises the following steps: receiving the high-order modulated signal of transmission in the launch end to be measured hollow-core fiber, high-order modulated signal is demodulated, and high-order demodulation signal is obtained;High-order demodulation signal is mapped to constellation diagram, and the nonlinear phase shift of high-order demodulation signal in constellation diagram is determined;Based on the nonlinear phase shift of high-order demodulation signal in constellation diagram and the pre-constructed kerr effect nonlinear mathematical model, the kerr effect nonlinear refractive index coefficient of to-be-measured hollow-core fiber is determined;Based on the kerr effect nonlinear refractive index coefficient of to-be-measured hollow-core fiber, the communication performance of to-be-measured hollow-core fiber is optimized.Through the above-mentioned mode, the mapping point in the signal constellation diagram after demodulation is analyzed, and the nonlinear phase shift is determined, so as to accurately calculate the kerr effect nonlinear refractive index coefficient by using nonlinear mathematical model and nonlinear phase shift.

Description

TECHNICAL FIELD

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

[0002] With the rise of cloud computing, big data, artificial intelligence and other technologies and industries, the demand for ultra-large capacity and ultra-low latency data transmission is growing rapidly. Hollow-core fiber has outstanding advantages in nonlinearity, large communication window, and small loss, which can well solve the capacity and latency limit problems of commercial quartz optical fiber from the 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 effect is the main factor limiting the capacity and distance improvement of optical fiber communication system, among which the Kerr effect has the most serious impact on high-speed optical signals. Therefore, in order to take advantage of the performance of optical fiber channel, it is necessary to model and characterize the Kerr effect nonlinearity of optical fiber, so as to improve the system performance by establishing appropriate encoding modulation and equalization methods. However, the current measurement method is difficult to accurately measure the Kerr effect nonlinear refractive index coefficient of hollow-core fiber.

[0004] The above content is only used to assist in understanding the technical solutions of the present application and does not represent the acknowledgement of the above content as prior art. SUMMARY

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

[0006] To achieve the above purpose, the present application provides a hollow-core fiber Kerr effect nonlinear coefficient measurement method, which comprises:

[0007] Receiving a high-order modulation signal transmitted by a to-be-measured hollow-core fiber in a transmitting end, demodulating the high-order modulation signal to obtain a high-order demodulation signal;

[0008] Mapping the high-order demodulation signal to a constellation diagram and determining the nonlinear phase shift of the high-order demodulation signal in the constellation diagram;

[0009] Based on the nonlinear phase shift of the high-order demodulation signal in the constellation diagram and the pre-constructed Kerr effect nonlinear mathematical model, the Kerr effect nonlinear refractive index coefficient of the to-be-measured hollow-core fiber is determined;

[0010] Based on the Kerr effect nonlinear refractive index coefficient of the to-be-measured hollow-core fiber, the communication performance of the to-be-measured hollow-core fiber is optimized.

[0011] In an embodiment, a first correspondence between the signal intensity, the effective fiber length, the Kerr effect nonlinear coefficient and the nonlinear phase shift is obtained;

[0012] Based on the first correspondence, a second correspondence between the fitting curve slope of the signal intensity and the nonlinear phase shift, the effective fiber length and the Kerr effect nonlinear coefficient is determined;

[0013] A third correspondence between the Kerr effect nonlinear refractive index coefficient, the effective mode field area, the signal light wavelength and the Kerr effect nonlinear coefficient is obtained;

[0014] Based on the second correspondence, the third correspondence is converted into a fourth correspondence between the fitting curve slope of the signal intensity and the 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;

[0015] Based on the fourth correspondence, the Kerr effect nonlinear mathematical model is constructed.

[0016] In an embodiment, the high-order demodulation signal is mapped into a constellation diagram, and a center position of a mapping point of the high-order demodulation signal in the constellation diagram is determined;

[0017] Based on the center position of the mapping point of the high-order demodulation signal in the constellation diagram, a rotation angle between the mapping point and the origin is determined;

[0018] Based on the rotation angle, a nonlinear phase shift of the high-order demodulation signal in the constellation diagram is determined.

[0019] In an embodiment, the mapping points of the high-order demodulation signal in the constellation diagram are classified according to the signal intensity, and a plurality of mapping groups are determined, and the signal intensities of the mapping points in each mapping group are the same;

[0020] Based on the rotation angles of the mapping points in the mapping groups, an arithmetic mean of the rotation angles of the mapping groups is determined, and the arithmetic mean of the rotation angles of the mapping groups is taken as the nonlinear phase shift of the mapping points in the mapping groups.

[0021] In an embodiment, the mapping points of the high-order demodulation signal in the constellation diagram are clustered, and a clustering center of the mapping points of the high-order demodulation signal in the constellation diagram is determined;

[0022] Based on the position of the clustering center of the mapping points of the high-order demodulation signal in the constellation diagram, the center position of the mapping points of the high-order demodulation signal in the constellation diagram is determined.

[0023] In an embodiment, the high-order modulation signal is obtained by modulating a high-order quadrature amplitude modulation signal on a plurality of orthogonal subcarriers, the high-order quadrature amplitude modulation signal being modulated by a coherent optical quadrature amplitude modulation strategy, a rate of the quadrature amplitude modulation signal being greater than a rate of the subcarriers.

[0024] In an embodiment, a total time period is determined based on a number of the subcarriers and a time period of the subcarriers.

[0025] A dispersion length of the to-be-measured hollow core fiber is determined based on the total time period and a group velocity dispersion parameter of the to-be-measured hollow core fiber, a boosting multiple between the dispersion length of the to-be-measured hollow core fiber and a single carrier modulation dispersion length being a square number of the number of the subcarriers.

[0026] When a transmission distance of the high-order modulation signal is less than the dispersion length, a step of receiving the high-order modulation signal transmitted by the to-be-measured hollow core fiber in the transmitting end, demodulating the high-order modulation signal, and obtaining a high-order demodulation signal is performed.

[0027] In addition, to achieve the above object, the present application further provides a hollow core fiber Kerr effect nonlinear coefficient measuring device, which comprises:

[0028] A demodulation module is configured to receive the high-order modulation signal transmitted by the to-be-measured hollow core fiber in the transmitting end, demodulate the high-order modulation signal, and obtain a high-order demodulation signal.

[0029] A mapping module is configured to map the high-order demodulation signal to a constellation diagram and determine a nonlinear phase shift of the high-order demodulation signal in the constellation diagram.

[0030] A characterization module is configured to determine a Kerr effect nonlinear refractive index coefficient of the to-be-measured hollow core fiber 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.

[0031] An optimization module is configured to optimize a communication performance of the to-be-measured hollow core fiber based on the Kerr effect nonlinear refractive index coefficient of the to-be-measured hollow core fiber.

[0032] In addition, to achieve the above object, the present application further provides a hollow core fiber Kerr effect nonlinear coefficient measuring device, which comprises 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 above hollow core fiber Kerr effect nonlinear coefficient measuring method.

[0033] In addition, to achieve the above objectives, the present invention also proposes a storage medium, which is a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the steps of the hollow fiber Kerr effect nonlinear coefficient measurement method described above.

[0034] In addition, to achieve the above objectives, this application also provides a computer program product, which includes a computer program that, when executed by a processor, implements the steps of the hollow fiber Kerr effect nonlinear coefficient measurement method as described above.

[0035] This application provides a method for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber. The method involves receiving a high-order modulated signal transmitted from the hollow-core optical fiber under test at the transmitter, demodulating the high-order modulated signal to obtain a high-order demodulated signal, mapping the high-order demodulated signal onto a constellation diagram, and determining the nonlinear phase shift of the high-order demodulated signal in the constellation diagram. 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 Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber under test is determined. Based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber under test, the communication performance of the hollow-core optical fiber under test is optimized. Through the above method, the received modulated signal is demodulated to recover the constellation diagram damaged by nonlinearity. The mapping points in the constellation diagram are analyzed to determine the nonlinear phase shift. Therefore, 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. This allows for the establishment of an appropriate coding modulation equalization strategy to improve communication performance, solving the technical problem of accurately measuring the Kerr effect nonlinear refractive index coefficient of hollow-core optical fiber. Attached Figure Description

[0036] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a flowchart illustrating an embodiment of the method for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber according to this application.

[0039] Figure 2 A schematic diagram of the 64QAM modulation constellation mapping relationship for the method of measuring the Kerr effect nonlinear coefficient of hollow fiber provided in Embodiment 1 of this application;

[0040] Figure 3 A schematic diagram of the nonlinear phase shift of the hollow-core optical fiber Kerr effect nonlinear coefficient measurement method provided in Embodiment 1 of this application;

[0041] Figure 4 This is a schematic diagram of the slope of the fitting curve for the method of measuring the Kerr effect nonlinear coefficient of hollow optical fiber provided in Embodiment 1 of this application.

[0042] Figure 5 This is a flowchart illustrating Embodiment 2 of the method for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber according to this application.

[0043] Figure 6 This is a flowchart illustrating Embodiment 3 of the method for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber according to this application.

[0044] Figure 7 A schematic diagram of the overall architecture of the hollow-core optical fiber Kerr effect nonlinear coefficient measurement method provided in Embodiment 3 of this application;

[0045] Figure 8 This is a schematic diagram of the transmitter DSP of the hollow fiber Kerr effect nonlinear coefficient measurement method provided in Embodiment 3 of this application;

[0046] Figure 9 This is a schematic diagram of the receiving end DSP of the hollow fiber Kerr effect nonlinear coefficient measurement method provided in Embodiment 3 of this application;

[0047] Figure 10 This is a schematic diagram of the module structure of the hollow fiber Kerr effect nonlinear coefficient measurement device according to an embodiment of this application;

[0048] Figure 11 This is a schematic diagram of the equipment structure of the hardware operating environment involved in the measurement method of the Kerr effect nonlinear coefficient of hollow fiber in the embodiments of this application.

[0049] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0050] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0051] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.

[0052] The main solution of this application embodiment is as follows: receiving the high-order modulation signal transmitted in the hollow-core optical fiber under test at the transmitter, demodulating the high-order modulation 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 under test 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 under test based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber under test.

[0053] Currently, the measurement methods used are insufficient for accurately measuring the Kerr effect nonlinear refractive index coefficient of hollow-core optical fibers.

[0054] This application provides a solution to demodulate the received modulated signal, recover the constellation diagram damaged by nonlinearity, analyze the mapping points in the constellation diagram to determine the nonlinear phase shift, and then 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 appropriate coding modulation equalization strategy to improve communication performance. This solves the technical problem of the difficulty in accurately measuring the Kerr effect nonlinear refractive index coefficient of hollow fiber.

[0055] It should be noted that the executing entity in this embodiment can be a computing service device with data processing, network communication, and program execution functions, such as a tablet computer, personal computer, or mobile phone, or an electronic device capable of performing the above functions, such as a hollow-core fiber Kerr effect nonlinear coefficient measurement device. This embodiment does not specifically limit it in this regard. The following uses a hollow-core fiber Kerr effect nonlinear coefficient measurement device as an example to describe this embodiment and the following embodiments.

[0056] This application provides a method for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber, referring to... Figure 1 , Figure 1 This is a flowchart illustrating the first embodiment of the method for measuring the Kerr effect nonlinear coefficient of hollow optical fiber according to this application.

[0057] In this embodiment, the method for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber includes steps S10~S40:

[0058] Step S10: Receive the high-order modulation signal transmitted in the hollow-core optical fiber under test in the transmitter, and demodulate the high-order modulation signal to obtain a high-order demodulated signal.

[0059] It should be noted that the hollow-core fiber under test is the hollow-core fiber for which the Kerr effect nonlinear coefficient needs to be measured. The higher-order modulation signal is the signal transmitted from the transmitter to the receiver through the hollow-core fiber under test. It is obtained by modulating a higher-order orthogonal amplitude modulation signal onto multiple orthogonal subcarriers. The orthogonal amplitude modulation signal is the higher-order QAM (Quadrature Amplitude Modulation) signal; that is, the higher-order modulation signal is the modulated higher-order QAM signal. In this embodiment, a coherent optical orthogonal frequency division multiplexing modulation strategy is used to modulate the higher-order QAM signal. The coherent optical orthogonal frequency division multiplexing modulation strategy is CO-OFDM (Coherent Optical Orthogonal Frequency Division Multiplexing) technology. In this case, the higher-order modulation signal can be considered a higher-order OFDM-QAM signal. In other embodiments, intensity modulation direct detection OFDM (Direct Detection Optical Orthogonal Frequency Division Multiplexing, DDO-OFDM) can also be used; no specific limitation is made.

[0060] It is understandable that CO-OFDM can modulate high-order QAM signals onto multiple orthogonal low-speed subcarriers. The rate of the orthogonal amplitude modulation signal is much greater than the rate of the subcarriers, thereby obtaining a larger dispersion length and thus realizing long-distance measurement of high-order OFDM-QAM signals.

[0061] It should be understood that after receiving a 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 impairments. If the Kerr effect nonlinear coefficient is directly calculated, it is difficult to guarantee the accuracy.

[0062] Step S20: Map the higher-order demodulated signal onto the constellation diagram and determine the nonlinear phase shift of the higher-order demodulated signal in the constellation diagram;

[0063] It should be noted that in this embodiment, the high-order demodulated signal is mapped onto a constellation diagram. The mapping points in the constellation diagram typically contain symbol information with different amplitude and phase combinations. For example, refer to... Figure 2 For 64QAM, different mapping points correspond to different positions in two-dimensional coordinates, which can be represented in coordinate form as follows: , There are a total of 64 mapping points. Due to the Kerr nonlinear effect, the mapping points in the constellation diagram usually rotate. The rotation angle of the mapping points is the nonlinear phase shift of the mapping points. (Refer to...) Figure 3Mapping points with different signal intensities will experience different degrees of nonlinear phase shift. .

[0064] It is understandable that this embodiment needs to determine the nonlinear phase shift of the higher-order demodulated signal in the constellation diagram. The center position can be found in the constellation diagram first, and the final nonlinear phase shift can be determined based on the rotation angle between the center position and the origin.

[0065] Step S30: Based on the nonlinear phase shift of the higher-order demodulated signal in the constellation diagram and the pre-constructed nonlinear mathematical model of the Kerr effect, determine the nonlinear refractive index coefficient of the hollow fiber under test.

[0066] It should be noted that the Kerr effect nonlinear mathematical model is the constellation mapping-Kerr nonlinear mathematical model constructed in this embodiment.

[0067] In one feasible implementation, the steps of constructing a nonlinear mathematical model of the Kerr effect may include steps S301 to S303:

[0068] Step S301: Obtain the first correspondence between signal strength, effective fiber length, Kerr effect nonlinear coefficient and nonlinear phase shift; based on the first correspondence, determine the second correspondence between the slope of the fitting curve of signal strength and nonlinear phase shift, effective fiber length and Kerr effect nonlinear coefficient.

[0069] It should be noted that the first correspondence between signal strength, effective fiber length, Kerr effect nonlinear coefficient, and nonlinear phase shift—that is, the formula for calculating nonlinear phase shift—is based on nonlinear optics theory. The nonlinear phase shift is directly proportional to the signal strength, as shown below:

[0070]

[0071] In the formula, Indicates nonlinear phase shift, Indicates signal strength. Indicates time, Represents the nonlinear coefficient of the Kerr effect. This represents the effective fiber length. The formula for calculating the effective fiber length is shown below:

[0072]

[0073] In the formula, Indicates the effective fiber length. Indicates the loss coefficient. This indicates the actual length of the hollow fiber to be tested.

[0074] Additionally, it should be noted that the referenceFigure 4 Nonlinear phase shift With signal strength The slope of the curve can be obtained through fitting, i.e., the slope of the fitted curve. The second correspondence between signal strength and the slope of the fitted curve of nonlinear phase shift, effective fiber length, and Kerr effect nonlinear coefficient, i.e., the formula for calculating the slope of the fitted curve, is shown below:

[0075]

[0076] In the formula, This represents the slope of the fitted curve. Represents the nonlinear coefficient of the Kerr effect. Indicates the effective fiber length.

[0077] Step S302: Obtain the third correspondence between the Kerr effect nonlinear refractive index coefficient, effective mode area, signal light wavelength and Kerr effect nonlinear coefficient. Based on the second correspondence, transform the third correspondence into a fourth correspondence between the slope of the fitting curve of signal intensity and nonlinear phase shift, effective mode area, signal light wavelength, effective fiber length, Kerr effect nonlinear coefficient and Kerr effect nonlinear refractive index coefficient.

[0078] It should be noted that the third correspondence between the Kerr effect nonlinear refractive index coefficient, effective mode area, signal light wavelength, and Kerr effect nonlinear coefficient, i.e., the calculation formula for the Kerr nonlinear coefficient, is as follows:

[0079]

[0080] In the formula, This represents the nonlinear refractive index coefficient due to the Kerr effect. This represents the effective mode field area of ​​the hollow-core optical fiber under test. The wavelength of the signal light representing the higher-order demodulated signal. Let represent the nonlinear coefficient of the Kerr effect. Therefore, the following calculation formula can be obtained:

[0081]

[0082] Furthermore, according to Through derivation, a fourth correspondence can be obtained between the slope of the fitting curve of signal intensity versus nonlinear phase shift, effective mode area, signal wavelength, effective fiber length, Kerr effect nonlinear coefficient, and Kerr effect nonlinear refractive index coefficient, as shown below:

[0083]

[0084] In the formula, This represents the nonlinear refractive index coefficient due to the Kerr effect. This represents the effective mode field area of ​​the hollow-core optical fiber under test. The wavelength of the signal light representing the higher-order demodulated signal. This represents the slope of the fitted curve. Indicates the effective fiber length.

[0085] Step S303: Based on the fourth correspondence, construct the nonlinear mathematical model of the Kerr effect.

[0086] It is understandable that a nonlinear mathematical model of the Kerr effect is constructed based on the fourth correspondence between the slope of the fitted curve of signal strength and nonlinear phase shift, effective mode area, signal wavelength, effective fiber length, Kerr effect nonlinear coefficient, and Kerr effect nonlinear refractive index coefficient.

[0087] It should be understood that by substituting the nonlinear phase shift of the higher-order demodulated signal in the constellation diagram into the nonlinear mathematical model of the Kerr effect, the nonlinear refractive index coefficient of the hollow fiber under test can be calculated. .

[0088] In addition to the nonlinear phase shift, other required parameters in this model can be obtained by characterizing the hollow-core fiber under test, such as the effective fiber length and effective mode area. Furthermore, by adjusting the signal wavelength of the higher-order modulation signal and performing multiple measurements, the average value of these measurements can be used as the final Kerr effect nonlinear refractive index coefficient, thereby reducing measurement errors.

[0089] Step S40: Optimize the communication performance of the hollow fiber under test based on the Kerr effect nonlinear refractive index coefficient.

[0090] It should be noted that after characterizing the Kerr effect nonlinear coefficients of the hollow-core fiber under test, communication performance can be improved by establishing an appropriate coding modulation equalization strategy.

[0091] This embodiment provides a method for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber. It receives a high-order modulated signal transmitted from the hollow-core optical fiber under test at the transmitting end, demodulates the high-order modulated signal to obtain a high-order demodulated signal, maps the high-order demodulated signal onto a constellation diagram, and determines the nonlinear phase shift of the high-order demodulated signal in the constellation diagram. 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 Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber under test is determined. Based on the Kerr effect nonlinear refractive index coefficient of the hollow-core optical fiber under test, the communication performance of the hollow-core optical fiber under test is optimized. Through the above method, the received modulated signal is demodulated to recover the constellation diagram damaged by nonlinearity. The mapping points in the constellation diagram are analyzed to determine the nonlinear phase shift. Thus, 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. This allows for the establishment of an appropriate coding modulation equalization strategy to improve communication performance.

[0092] Based on the first embodiment of this application, in the second embodiment of this application, the content that is the same as or similar to that in Embodiment 1 above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 5 Step S20 may include steps S201 to S203:

[0093] Step S201: Map the higher-order demodulated signal onto a constellation diagram to determine the center position of the mapping point of the higher-order demodulated signal in the constellation diagram;

[0094] In one feasible implementation, step S201 includes: clustering the mapping points of the higher-order demodulated signal in the constellation diagram to determine the cluster center of the mapping points of the higher-order demodulated signal in the constellation diagram; and determining the center position of the mapping points of the higher-order demodulated signal in the constellation diagram based on the position of the cluster center of the mapping points of the higher-order demodulated signal in the constellation diagram.

[0095] It is understood that this embodiment uses a clustering algorithm to analyze the mapping points in the constellation diagram, determine the cluster centers, and thus find the central location of the mapping points in the constellation diagram. The clustering algorithm can be K-means clustering, other suitable clustering methods, or deep learning algorithms or genetic algorithms; no specific limitation is made. This embodiment uses K-means clustering, which will not increase the complexity of the DSP.

[0096] Step S202: Based on the center position of the mapping point of the higher-order demodulated signal in the constellation diagram, determine the rotation angle between the mapping point and the origin;

[0097] It should be noted that the rotation angle of the mapping point relative to the origin can be obtained based on the center position of the mapping point in the constellation diagram.

[0098] Step S203: Based on the rotation angle, determine the nonlinear phase shift of the higher-order demodulated signal in the constellation diagram.

[0099] In one feasible implementation, step S203 includes: classifying the mapping points of the higher-order demodulated signal in the constellation diagram according to the signal strength, determining multiple mapping groups, wherein the signal strength of the mapping points in each mapping group is the same; determining the arithmetic mean of the rotation angles of the mapping groups based on the rotation angles of the mapping points in the mapping groups, and using the arithmetic mean of the rotation angles of the mapping groups as the nonlinear phase shift of the mapping points in the mapping groups.

[0100] It should be noted that in this embodiment, the mapping points are classified according to signal strength. Mapping points with the same signal strength are grouped together, and a group of mapping points is called a mapping group. Multiple mapping groups can be obtained, and the signal strength of the mapping points in the mapping group is the same. The arithmetic mean of the rotation angle is the arithmetic mean of the rotation angles. 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 variations.

[0101] This embodiment provides a method for measuring the nonlinear coefficient of the Kerr effect in hollow-core optical fiber. The method maps a high-order demodulated signal onto a constellation diagram, determining the center position of the mapped point in the diagram. Based on the center position, the rotation angle between the mapped point and the origin is determined. Based on the rotation angle, the nonlinear phase shift of the high-order demodulated signal in the constellation diagram is determined. Through clustering, the center position of the mapped point is accurately determined, and the nonlinear phase shift is accurately calculated. This allows for a refined characterization using the nonlinear mathematical model of the Kerr effect and the nonlinear phase shift, enabling the accurate calculation of the nonlinear refractive index coefficient of the Kerr effect. Furthermore, an appropriate coding modulation equalization strategy can be established to improve communication performance.

[0102] Based on the first embodiment of this application, in the third embodiment of this application, the same or similar content as the above embodiment can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 6 Steps S01 to S03 may be included before step S10:

[0103] Step S01: Determine the total time period based on the number of subcarriers and the time period of the subcarriers;

[0104] It should be noted that fiber dispersion is one of the channel impairment phenomena that cannot be ignored in optical communication systems. Its impact is related to the signal rate, and the expression for calculating the dispersion length is:

[0105]

[0106] In the formula, This represents the time period of the higher-order modulation signal, and its reciprocal corresponds to the baud rate of the higher-order modulation signal. This represents the group velocity dispersion parameter; the group velocity dispersion value of hollow fiber is approximately one-sixth that of silica fiber.

[0107] It is understandable that when the actual fiber optic transmission distance... At this time, signal transmission is not affected by dispersion, and when the actual fiber optic transmission distance is... At this time, signal transmission is greatly affected by dispersion, and in this case, the Kerr nonlinear coefficient cannot be characterized by signal distortion (nonlinear phase shift).

[0108] Therefore, in this embodiment, the high-order QAM signal is modulated onto multiple orthogonal low-speed subcarriers, assuming a total of Subcarriers, for modulation to For a high-order modulation signal with individual subcarriers, the time period , This represents the time period of each subcarrier. Therefore, based on the number of subcarriers and their time periods, the total time period can be calculated, which serves as the time period of the higher-order modulation signal.

[0109] Step S02: Based on the total time period and the group velocity dispersion parameter of the hollow fiber under test, determine the dispersion length of the hollow fiber under test. The boost factor between the dispersion length of the hollow fiber under test and the single-carrier modulation dispersion length is the square of the number of subcarriers.

[0110] It should be noted that, based on the total time period and the group velocity dispersion parameters of the hollow fiber under test, the dispersion length of the hollow fiber under test is calculated. Therefore, compared to the dispersion length of single-carrier modulation, the dispersion length of the hollow fiber under test in this embodiment can be improved. The multiplier is the square of the number of subcarriers, which effectively increases the measurement length.

[0111] Step S03: When the transmission distance of the higher-order modulation signal is less than the dispersion length, perform the step of receiving the higher-order modulation signal transmitted in the hollow fiber under test in the receiving end, demodulating the higher-order modulation signal, and obtaining the higher-order demodulated signal.

[0112] It is understandable that when the transmission distance of the high-order modulated signal is less than the dispersion length, steps S10~S40 are executed to characterize the Kerr effect nonlinear coefficient of the hollow-core fiber under test. This embodiment can increase the measurement length to single-carrier modulation. times.

[0113] Furthermore, the transmitter can add a cyclic prefix (CP) to the signal to prevent inter-symbol interference caused by channel dispersion.

[0114] This embodiment provides a method for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber. The high-order QAM signal is modulated on multiple orthogonal low-speed subcarriers to obtain a larger dispersion length, thereby realizing long-distance measurement of the high-order OFDM-QAM signal.

[0115] For example, to help understand the implementation process of the hollow-core fiber Kerr effect nonlinear coefficient measurement method obtained by combining this embodiment with the above-described embodiment three, please refer to... Figure 7 , Figure 7 A schematic diagram of the overall architecture of a method for measuring the Kerr effect nonlinear coefficient in hollow-core optical fibers is provided, specifically:

[0116] By adjusting the value of the variable optical attenuator (VOA) at the transmitter, the input optical power is changed to better excite nonlinear effects. The OFDM baseband signal is generated in digital signal processing (DSP), referencing... Figure 8 The serial bitstream input at the transmitter is first converted into a multi-parallel data stream via serial-to-parallel conversion. Each data stream is then mapped using QAM modulation, and the mapped data is padded with zeros to construct a guard band. Next, an Inverse Fast 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 serial-to-parallel conversion, the signal is converted into an analog signal (baseband OFDM signal) by an Arbitrary Waveform Generator (AWG). The transmitter uses a continuously tunable laser with an IQ modulator to modulate the electrical signal to be transmitted onto the optical field. The modulated optical signal is then amplified and entered into the hollow-core fiber optic transmission link under test. The received optical signal is converted into an analog electrical signal by a coherent receiver, and finally sampled into a digital signal by a real-time oscilloscope for further DSP processing. (Reference) Figure 9 The receiving end's processing flow for the received high-order modulated signal includes synchronization, phase noise compensation, serial-to-parallel conversion, CP removal, FFT, demodulation, and QAM mapping. Based on the demodulated constellation mapping relationship, the center position of each mapping point is characterized, and finally the Kerr nonlinear refractive index coefficient of the hollow fiber under test 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.

[0117] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the method for measuring the nonlinear coefficient of the Kerr effect in hollow fiber. Any simple transformations based on this technical concept are within the protection scope of this application.

[0118] This application also provides a device for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber. Please refer to [reference needed]. Figure 10 The device for measuring the Kerr effect nonlinear coefficient of hollow optical fiber includes:

[0119] The demodulation module 10 is used to receive the high-order modulation signal transmitted in the hollow fiber under test in the transmitter, and demodulate the high-order modulation signal to obtain a high-order demodulated signal.

[0120] The mapping module 20 is used to map the higher-order demodulated signal onto a constellation diagram and determine the nonlinear phase shift of the higher-order demodulated signal in the constellation diagram.

[0121] The characterization module 30 is used to determine the Kerr effect nonlinear refractive index coefficient of the hollow fiber under test based on the nonlinear phase shift of the higher-order demodulated signal in the constellation diagram and the pre-constructed Kerr effect nonlinear mathematical model.

[0122] The optimization module 40 is used to optimize the communication performance of the hollow fiber under test based on the Kerr effect nonlinear refractive index coefficient of the hollow fiber under test.

[0123] In one feasible implementation, the characterization module 30 is further used to obtain a first correspondence between signal strength, effective fiber length, Kerr effect nonlinear coefficient and nonlinear phase shift;

[0124] Based on the first correspondence, a second correspondence is determined between the slope of the fitting curve of signal strength and nonlinear phase shift, the effective fiber length, and the Kerr effect nonlinear coefficient.

[0125] Obtain the third correspondence between the Kerr effect nonlinear refractive index coefficient, effective mode area, signal light wavelength, and Kerr effect nonlinear coefficient;

[0126] Based on the second correspondence, the third correspondence is transformed into a fourth correspondence between the slope of the fitting curve of signal intensity and nonlinear phase shift, effective mode area, signal light wavelength, effective fiber length, Kerr effect nonlinear coefficient, and Kerr effect nonlinear refractive index coefficient.

[0127] Based on the fourth correspondence, the nonlinear mathematical model of the Kerr effect is constructed.

[0128] In one feasible implementation, the mapping module 20 is further configured to map the higher-order demodulated signal onto a constellation diagram and determine the center position of the mapping point of the higher-order demodulated signal in the constellation diagram;

[0129] Based on the center position of the mapping point of the higher-order demodulated signal in the constellation diagram, the rotation angle between the mapping point and the origin is determined.

[0130] Based on the rotation angle, the nonlinear phase shift of the higher-order demodulated signal in the constellation diagram is determined.

[0131] In one feasible implementation, the mapping module 20 is further configured to classify the mapping points of the higher-order demodulated signal in the constellation diagram according to the signal strength, and determine multiple mapping groups, wherein the signal strength of the mapping points in each mapping group is the same.

[0132] Based on the rotation angles of the mapping points in the mapping group, the 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.

[0133] In one feasible implementation, the mapping module 20 is further configured to cluster the mapping points of the higher-order demodulated signal in the constellation diagram to determine the cluster center of the mapping points of the higher-order demodulated signal in the constellation diagram.

[0134] Based on the location of the cluster center of the mapping point of the higher-order demodulated signal in the constellation diagram, the center position of the mapping point of the higher-order demodulated signal in the constellation diagram is determined.

[0135] In one feasible implementation, the higher-order modulation signal is obtained by modulating a higher-order orthogonal amplitude modulation signal onto multiple orthogonal subcarriers. The higher-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 subcarriers.

[0136] In one feasible implementation, the demodulation module 10 is further configured to determine the total time period based on the number of subcarriers and the time period of the subcarriers;

[0137] Based on the total time period and the group velocity dispersion parameter of the hollow fiber under test, the dispersion length of the hollow fiber under test is determined, and the boost factor between the dispersion length of the hollow fiber under test and the single-carrier modulation dispersion length is the square of the number of subcarriers.

[0138] When the transmission distance of the higher-order modulation signal is less than the dispersion length, the steps of receiving the higher-order modulation signal transmitted in the hollow fiber under test in the receiving end, demodulating the higher-order modulation signal, and obtaining the higher-order demodulated signal are performed.

[0139] The hollow-core fiber Kerr effect nonlinear coefficient measuring device provided in this application, employing the hollow-core fiber Kerr effect nonlinear coefficient measuring method described in the above embodiments, can solve the technical problem of difficulty in accurately measuring the nonlinear refractive index coefficient of the hollow-core fiber Kerr effect. Compared with the prior art, the beneficial effects of the hollow-core fiber Kerr effect nonlinear coefficient measuring device provided in this application are the same as those of the hollow-core fiber Kerr effect nonlinear coefficient measuring method provided in the above embodiments, and other technical features in the hollow-core fiber Kerr effect nonlinear coefficient measuring device are the same as those disclosed in the methods of the above embodiments, and will not be repeated here.

[0140] This application provides a device for measuring the Kerr effect nonlinear coefficient of hollow fiber. The device includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method for measuring the Kerr effect nonlinear coefficient of hollow fiber in the above embodiment 1.

[0141] The following is for reference. Figure 11 This document illustrates a structural schematic diagram of a hollow-core fiber Kerr effect nonlinear coefficient measurement device suitable for implementing embodiments of this application. The hollow-core fiber Kerr effect nonlinear coefficient measurement device in this application embodiment may include, but is not limited to, mobile terminals such as mobile phones, laptops, digital broadcast receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Description), PMPs (Portable Media Players), and in-vehicle terminals (e.g., in-vehicle navigation terminals), as well as fixed terminals such as digital TVs and desktop computers. Figure 11 The hollow fiber Kerr effect nonlinear coefficient measurement device shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this application.

[0142] like Figure 11As shown, the hollow-core fiber Kerr effect nonlinear coefficient measurement device may include a processing unit 1001 (e.g., a central processing unit, graphics processor, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage device 1003 into a random access memory (RAM) 1004. The RAM 1004 also stores various programs and data required for the operation of the hollow-core fiber Kerr effect nonlinear coefficient measurement device. The processing unit 1001, ROM 1002, and RAM 1004 are interconnected via a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to I / O interface 1006: input devices 1007 including, for example, touchscreens, touchpads, keyboards, mice, image sensors, microphones, accelerometers, gyroscopes, etc.; output devices 1008 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 1003 including, for example, magnetic tapes, hard disks, etc.; and communication devices 1009. Communication device 1009 allows the hollow-core fiber Kerr effect nonlinear coefficient measuring device to communicate wirelessly or wiredly with other devices to exchange data. Although the figure shows a hollow-core fiber Kerr effect nonlinear coefficient measuring device with various systems, it should be understood that it is not required to implement or possess all the systems shown. More or fewer systems can be implemented alternatively.

[0143] Specifically, according to the embodiments disclosed in this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments disclosed in this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device, or installed from storage device 1003, or installed from ROM 1002. When the computer program is executed by processing device 1001, it performs the functions defined in the methods of the embodiments disclosed in this application.

[0144] The hollow-core fiber Kerr effect nonlinear coefficient measurement device provided in this application, employing the hollow-core fiber Kerr effect nonlinear coefficient measurement method described in the above embodiments, can solve the technical problem of difficulty in accurately measuring the nonlinear refractive index coefficient of the hollow-core fiber Kerr effect. Compared with the prior art, the beneficial effects of the hollow-core fiber Kerr effect nonlinear coefficient measurement device provided in this application are the same as those of the hollow-core fiber Kerr effect nonlinear coefficient measurement method provided in the above embodiments, and other technical features in this hollow-core fiber Kerr effect nonlinear coefficient measurement device are the same as those disclosed in the previous embodiment method, and will not be repeated here.

[0145] It should be understood that the various parts disclosed in this application can be implemented using 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 suitable manner in one or more embodiments or examples.

[0146] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0147] This application provides a computer-readable storage medium having computer-readable program instructions (i.e., a computer program) stored thereon, the computer-readable program instructions being used to execute the hollow fiber Kerr effect nonlinear coefficient measurement method in the above embodiments.

[0148] The computer-readable storage medium provided in this application may be, for example, a USB flash drive, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, system, or device. The program code contained on the computer-readable storage medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0149] The aforementioned computer-readable storage medium may be included in the hollow fiber Kerr effect nonlinear coefficient measuring device; or it may exist independently and not assembled into the hollow fiber Kerr effect nonlinear coefficient measuring device.

[0150] The aforementioned computer-readable storage medium carries one or more programs. When these programs are executed by the hollow-core fiber Kerr effect nonlinear coefficient measurement device, the device performs the following actions: receives a high-order modulation signal transmitted in the hollow-core fiber under test at the transmitting end; demodulates the high-order modulation signal to obtain a high-order demodulated signal; maps the high-order demodulated signal onto 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 fiber under test 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 fiber under test based on the Kerr effect nonlinear refractive index coefficient of the hollow-core fiber under test.

[0151] Computer program code for performing the operations of this application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a Local Area Network (LAN) or a Wide Area Network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0152] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0153] The modules described in the embodiments of this application can be implemented in software or hardware. The names of the modules do not necessarily limit the functionality of the unit itself.

[0154] The readable storage medium provided in this application is a computer-readable storage medium that stores computer-readable program instructions (i.e., a computer program) for executing the above-described method for measuring the nonlinear coefficient of the Kerr effect in hollow-core optical fibers. This solves the technical problem of the difficulty in accurately measuring the nonlinear refractive index coefficient of the Kerr effect in hollow-core optical fibers. Compared with the prior art, the beneficial effects of the computer-readable storage medium provided in this application are the same as those of the nonlinear coefficient measurement method for the Kerr effect in hollow-core optical fibers provided in the above embodiments, and will not be repeated here.

[0155] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described method for measuring the nonlinear coefficient of the Kerr effect in hollow optical fiber.

[0156] The computer program product provided in this application can solve the technical problem of the difficulty in accurately measuring the nonlinear refractive index coefficient of the Kerr effect in hollow optical fibers. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as those of the nonlinear coefficient measurement method of the Kerr effect in hollow optical fibers provided in the above embodiments, and will not be repeated here.

[0157] The above are only some embodiments of this application and do not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A method of measuring the Kerr nonlinearity of a hollow-core optical fiber, characterized in that, The method comprises: receiving a high-order modulation signal to be transmitted by the hollow-core optical fiber at the transmitting end, demodulating the high-order modulation signal to obtain a high-order demodulation signal; mapping the high-order demodulation signal to a constellation diagram and determining a nonlinear phase shift of the high-order demodulation signal in the constellation diagram, specifically comprising: clustering the mapping points of the high-order demodulation signal in the constellation diagram, and determining the cluster centers of the mapping points of the high-order demodulation signal in the constellation diagram; determining the center positions of the mapping points of the high-order demodulation signal in the constellation diagram based on the positions of the cluster centers of the mapping points of the high-order demodulation signal in the constellation diagram; determining the rotation angles between the mapping points and the origin in the constellation diagram based on the center positions of the mapping points of the high-order demodulation signal in the constellation diagram; classifying the mapping points of the high-order demodulation signal in the constellation diagram according to signal strength, and determining a plurality of mapping groups, the signal strengths of the mapping points in each mapping group being the same; determining the arithmetic mean of the rotation angles of the mapping groups based on the rotation angles of the mapping points in the mapping groups, and taking the arithmetic mean of the rotation angles of the mapping groups as the nonlinear phase shift of the mapping points in the mapping groups; determining the Kerr nonlinear refractive index coefficient of the hollow-core optical fiber to be tested based on the nonlinear phase shift of the high-order demodulation signal in the constellation diagram and the pre-constructed Kerr nonlinear mathematical model; optimizing the communication performance of the hollow-core optical fiber to be tested based on the Kerr nonlinear refractive index coefficient of the hollow-core optical fiber to be tested.

2. The method of claim 1, wherein, The method further comprises: obtaining a first correspondence relationship between signal strength, effective fiber length, Kerr nonlinear coefficient and nonlinear phase shift; determining a second correspondence relationship between the fitting curve slope of signal strength and nonlinear phase shift, effective fiber length and Kerr nonlinear coefficient based on the first correspondence relationship; obtaining a third correspondence relationship between Kerr nonlinear refractive index coefficient, effective mode field area, signal light wavelength and Kerr nonlinear coefficient; transforming the third correspondence relationship into a fourth correspondence relationship between the fitting curve slope of signal strength and nonlinear phase shift, effective mode field area, signal light wavelength, effective fiber length, Kerr nonlinear coefficient and Kerr nonlinear refractive index coefficient based on the second correspondence relationship; constructing the Kerr nonlinear mathematical model based on the fourth correspondence relationship.

3. The method of claim 1 or 2, wherein, The high-order modulation signal is obtained by modulating a high-order quadrature amplitude modulation signal on a plurality of orthogonal subcarriers, the high-order quadrature amplitude modulation signal is modulated by using a coherent optical orthogonal frequency division multiplexing modulation strategy, and the rate of the quadrature amplitude modulation signal is greater than the rate of the subcarriers.

4. The method of claim 3, wherein, The method further comprises: determining a total time period based on the number of subcarriers and the time period of the subcarriers. determining a dispersion length of the to-be-tested hollow core fiber based on the total time period and a group velocity dispersion parameter of the to-be-tested hollow core fiber, wherein a boosting multiple between the dispersion length of the to-be-tested hollow core fiber and a single carrier modulation dispersion length is a square number of the number of the subcarriers; when a transmission distance of the high-order modulation signal is less than the dispersion length, performing a step of receiving the high-order modulation signal transmitted by the to-be-tested hollow core fiber in the transmitting end, demodulating the high-order modulation signal to obtain a high-order demodulation signal.

5. A device for measuring the Kerr effect nonlinear coefficient of hollow-core optical fiber, characterized in that, The device comprises: a demodulation module configured to receive the high-order modulation signal transmitted by the to-be-tested hollow core fiber in the transmitting end, demodulate the high-order modulation signal to obtain a high-order demodulation signal; a mapping module configured to map the high-order demodulation signal to a constellation diagram and determine a nonlinear phase shift of the high-order demodulation signal in the constellation diagram; a characterization module configured to determine a Kerr effect nonlinear refractive index coefficient of the to-be-tested hollow core fiber 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; an optimization module configured to optimize a communication performance of the to-be-tested hollow core fiber based on the Kerr effect nonlinear refractive index coefficient of the to-be-tested hollow core fiber; the mapping module is further configured to cluster mapping points of the high-order demodulation signal in the constellation diagram and determine a cluster center of the mapping points of the high-order demodulation signal in the constellation diagram; determine a center position of the mapping points of the high-order demodulation signal in the constellation diagram based on a position of the cluster center of the mapping points of the high-order demodulation signal in the constellation diagram; determine a rotation angle between the mapping points and an origin based on the center position of the mapping points of the high-order demodulation signal in the constellation diagram; classify the mapping points of the high-order demodulation signal in the constellation diagram according to signal intensities, determine a plurality of mapping groups, and the signal intensities of the mapping points in each mapping group are the same; determine an arithmetic mean of the rotation angles of the mapping groups based on the rotation angles of the mapping points in the mapping groups, and take the arithmetic mean of the rotation angles of the mapping groups as the nonlinear phase shift of the mapping points in the mapping groups.

6. An apparatus for measuring a Kerr effect nonlinear coefficient of a hollow core optical fiber, characterized by, The device comprises a memory, a processor, and a computer program stored on the memory and executable on the processor, and the computer program is configured to implement the steps of the hollow core fiber Kerr effect nonlinear coefficient measurement method according to any one of claims 1 to 4.

7. A storage medium, characterized by The storage medium is a computer readable storage medium, and the storage medium stores a computer program, and the computer program is executed by the processor to implement the steps of the hollow core fiber Kerr effect nonlinear coefficient measurement method according to any one of claims 1 to 4.

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