Anti-resonant hollow-core fiber kerr effect nonlinear coefficient characterization method, device, equipment and system

Abstract

This application discloses a method, apparatus, device, and system for characterizing the Kerr effect nonlinear coefficient in antiresonant hollow-core optical fiber, relating to the field of optical fiber communication technology. The method is applied at the transmitting end and includes: processing an input data bitstream based on a bit loading strategy to obtain a baseband orthogonal frequency division multiplexing (OFDM) signal; modulating a composite optical signal according to the baseband OFDM signal to obtain a transmittable optical signal; and transmitting the transmittable optical signal through the hollow-core optical fiber under test, so that the receiving end can characterize the Kerr effect nonlinear coefficient and the communication performance of the hollow-core optical fiber under test based on the transmittable optical signal. By mapping different modulation orders of the signal subcarriers, the high-order OFDM QAM signal to be measured is modulated onto the optical field at the transmitting end through a modulator. The receiving end then characterizes the Kerr effect nonlinear coefficient based on the modulated optical field signal, achieving accurate characterization of the Kerr effect nonlinear coefficient.

Description

Technical Field

[0001] This application relates to the field of optical fiber communication technology, and in particular to a method, apparatus, equipment and system for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow optical fiber. Background Technology

[0002] The development of social productivity and major social changes have spurred the upgrading of optical fiber communication technology. For example, the rise of new industries such as artificial intelligence and cloud computing has led to a rapid increase in demand for high-capacity, long-distance, low-latency data transmission. In the continuous development of optical communication, transmission rate and transmission distance are two indicators for measuring the efficiency and economic benefits of a communication system, typically measured by the bit rate-distance product. Statistics show that the bit rate-distance product of optical fiber communication systems has increased tenfold every four years over the past 30 years. New technologies such as tunable lasers, optical amplifiers, wavelength division multiplexing (WDM), and digital coherence have greatly improved the performance of optical communication systems, but have also brought new problems, such as the inherent dispersion and nonlinearity limitations of optical fibers. The emergence of a new transmission medium—anti-resonate hollow core fiber (AR-HCF)—is expected to break the capacity and latency limits of commercial silica fiber under nonlinear channels. Its outstanding advantages, such as low nonlinearity, large communication window, and low loss, provide technical support for building next-generation high-bandwidth, low-latency optical communication systems.

[0003] Characterizing and monitoring the nonlinearity of the channel within an optical fiber link is a crucial foundation for subsequent accurate nonlinear compensation. The nonlinear effect of optical fiber refers to the effect caused by nonlinear polarization of the fiber medium under strong light, including stimulated scattering nonlinearity and Kerr nonlinearity. The former is a nonlinear effect caused by scattering, such as stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS). The latter is caused by the change in the refractive index of the fiber with light intensity, such as self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM). Nonlinear effects have a significant impact on high-capacity, long-distance wavelength division multiplexing (WDM) optical fiber communication systems. For example, in S+C+L band WDM systems, the optical amplifier amplifies the signal while greatly enhancing the nonlinear effects within the optical fiber link. Among these, the Kerr nonlinear effect is the main factor affecting the performance of high-speed, high-capacity channels. Therefore, characterizing the Kerr nonlinear coefficient of optical fiber channels has become a current research hotspot.

[0004] Kerr nonlinearity coefficients can be characterized by measuring the inherent characteristics of the nonlinear effect itself. The SPM method utilizes the broadening of the modulation signal spectrum by the SPM effect, while the XPM method utilizes the induced phase shift of the SPM effect. Both of these methods require specific signal light sources and can only measure a limited range of fiber lengths and dispersion magnitudes, resulting in unstable nonlinearity coefficient measurements. The FWM method uses the power of newly generated frequency light waves within the optical channel to measure the nonlinearity coefficient, offering high accuracy and stability, but requires an additional pump light source and precise control of the pump and probe light to be in the same polarization state. All these characterization methods are significantly affected by experimental conditions such as fiber dispersion, input optical power, and fiber length, leading to a certain degree of divergence between measured data and theoretical values. Furthermore, according to existing reports, the Kerr nonlinearity coefficient n² of hollow-core fiber is three orders of magnitude lower than that of single-mode silica fiber, reaching the 10⁻²³ level. Therefore, traditional characterization methods with relatively coarse measurement accuracy cannot be used to accurately characterize hollow-core fibers with ultra-low nonlinearity coefficients. Summary of the Invention

[0005] The main objective of this application is to provide a method, apparatus, equipment, and system for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber, aiming to solve the technical problem of low accuracy in calculating the Kerr effect nonlinear coefficient using existing single-mode fiber nonlinear measurement methods.

[0006] To achieve the above objectives, this application proposes a method for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber. This method is applied at the transmitting end and includes:

[0007] The input data bitstream is processed based on a bit loading strategy to obtain a baseband orthogonal frequency division multiplexed signal.

[0008] The composite optical signal is modulated according to the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted.

[0009] The optical signal to be transmitted is transmitted through the hollow-core optical fiber under test, so that the receiving end can characterize the Kerr effect nonlinear coefficient and the communication performance of the hollow-core optical fiber under test based on the optical signal to be transmitted.

[0010] In one embodiment, the step of processing the input data bitstream based on a bit loading strategy to obtain a baseband orthogonal frequency division multiplexing signal includes:

[0011] The input data bitstream is converted from serial to parallel to obtain a parallel data stream;

[0012] The parallel data stream is processed based on a bit loading strategy to obtain the bit allocation results for each subcarrier;

[0013] Based on the bit allocation results of each subcarrier and the orthogonal amplitude modulation strategy, symbol mapping is performed to obtain the target mapping data;

[0014] The target mapping data is converted into a baseband orthogonal frequency division multiplexed signal by a waveform generator.

[0015] In one embodiment, the step of processing the parallel data stream based on a bit loading strategy to obtain the bit allocation results for each subcarrier includes:

[0016] The channel state of the parallel data stream is estimated based on the bit loading strategy to obtain the channel state estimation result;

[0017] Based on the preset bit allocation strategy and the channel state estimation results, bit allocation is performed on each subcarrier of the parallel data stream to obtain the bit allocation results for each subcarrier.

[0018] In one embodiment, the step of modulating the composite optical signal based on the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted includes:

[0019] Input the baseband orthogonal frequency division multiplexed signal to the signal modulator to determine the in-phase signal and the quadrature signal;

[0020] The composite optical signal is modulated based on the in-phase signal and the quadrature signal to obtain the optical signal to be transmitted.

[0021] To achieve the above objectives, this application proposes a method for characterizing the Kerr effect nonlinear coefficient in antiresonant hollow fiber. This method is applied at the receiving end and includes:

[0022] When the optical signal to be transmitted is received from the hollow optical fiber under test, the optical signal to be transmitted is converted to obtain the target digital signal;

[0023] The target digital signal is processed to obtain the target processed signal;

[0024] Based on the target processed signal and the preset Kerr effect coefficient model, the Kerr effect nonlinear coefficient is obtained, and the communication performance of the hollow fiber under test is characterized.

[0025] In one embodiment, the step of characterizing the target processed signal and a preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficients includes:

[0026] Based on the modulation format of the target processing signal, an orthogonal amplitude modulation signal of the corresponding modulation order is mapped to obtain the orthogonal amplitude modulation signal corresponding to the target processing signal;

[0027] The average amplitude of the same value corresponding to the quadrature amplitude modulation signal is calculated to obtain the average same amplitude.

[0028] Input the average equal amplitude into the preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficient.

[0029] In one embodiment, the step of inputting the average equal amplitude to a preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficients includes:

[0030] Input the average equal amplitude into the preset Kerr effect coefficient model to obtain the target Kerr effect coefficients corresponding to each subcarrier signal and each orthogonal amplitude modulation format;

[0031] The Kerr effect nonlinear coefficient is obtained by averaging the multiple target Kerr effect coefficients.

[0032] Furthermore, to achieve the above objectives, this application also proposes a device for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber, the device comprising:

[0033] The processing module is used to process the input data bit stream based on the bit loading strategy to obtain the baseband orthogonal frequency division multiplexing signal;

[0034] The modulation module is used to modulate the composite optical signal according to the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted;

[0035] The characterization module is used to transmit the optical signal to be transmitted through the hollow fiber under test, so that the receiving end can characterize the Kerr effect nonlinear coefficient and the communication performance of the hollow fiber under test based on the optical signal to be transmitted.

[0036] Furthermore, to achieve the above objectives, this application also proposes a device for characterizing the nonlinear coefficient of the Kerr effect in antiresonant hollow fiber. The device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. The computer program is configured to implement the steps of the method for characterizing the nonlinear coefficient of the Kerr effect in antiresonant hollow fiber as described above.

[0037] In addition, to achieve the above objectives, this application also proposes a storage medium, which is a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the steps of the method for characterizing the nonlinear coefficient of the Kerr effect in anti-resonant hollow fiber as described above.

[0038] 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 method for characterizing the nonlinear coefficient of the Kerr effect in anti-resonant hollow fiber as described above.

[0039] This application processes the input data bitstream using a bit-loading strategy to obtain a baseband orthogonal frequency division multiplexing (OFDM) signal. The composite optical signal is then modulated using the OFDM signal to obtain a transmittable optical signal. This transmittable optical signal is then transmitted through a hollow-core optical fiber under test, allowing the receiver to characterize the Kerr effect nonlinearity coefficient and the communication performance of the fiber based on the transmittable optical signal. By mapping different modulation orders to the signal subcarriers, the high-order OFDM QAM signal to be measured is modulated onto the optical field at the transmitter. The receiver then characterizes the Kerr effect nonlinearity coefficient based on the modulated optical field signal, achieving accurate characterization of the Kerr effect nonlinearity coefficient. Attached Figure Description

[0040] 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.

[0041] 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.

[0042] Figure 1 This is a flowchart illustrating an embodiment of the method for characterizing the nonlinear coefficient of the Kerr effect in anti-resonant hollow fiber applied to the transmitter.

[0043] Figure 2 This is a schematic diagram of the QAM modulation constellation mapping relationship under the AWGN channel provided in Example 1 of the application of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method to the transmitter.

[0044] Figure 3 This provides different QAM mappings and nonlinear phase shifts for Example 1, which applies the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method of this application to the transmitter. With signal strength |A| 2 A schematic diagram of the linear fitting relationship;

[0045] Figure 4 This is a schematic diagram of the two-dimensional Kerr nonlinear measurement principle based on the modulation domain and frequency domain, provided for the first embodiment of the application of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method of this application to the transmitter.

[0046] Figure 5 This is a flowchart illustrating an embodiment of the method for characterizing the nonlinear coefficient of the Kerr effect in anti-resonant hollow fiber, as described in this application, applied to the receiver.

[0047] Figure 6 A block diagram for measuring the two-dimensional Kerr nonlinear coefficient of an m-channel WDM bit-loading OFDM optical communication system is provided in Embodiment 1 of the application of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method of this application to the receiver.

[0048] Figure 7 The following is a flowchart of the DSP in the Kerr nonlinear characterization system based on WDM-OFDM combined with bit loading modulation technology, provided in Example 1 of the application of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method to the receiver: (a) transmitter, (b) receiver;

[0049] Figure 8 This is a schematic diagram of the module structure of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device according to an embodiment of this application;

[0050] Figure 9This is a schematic diagram of the equipment structure of the hardware operating environment involved in the method for characterizing the nonlinear coefficient of the Kerr effect in antiresonant hollow fiber in the embodiments of this application.

[0051] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0052] 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.

[0053] 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.

[0054] The main solution of this application embodiment is: to process the input data bit stream based on the bit loading strategy to obtain a baseband orthogonal frequency division multiplexing signal; to modulate the composite optical signal according to the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted; and to transmit the optical signal to be transmitted through the hollow-core optical fiber under test so that the receiving end can characterize the Kerr effect nonlinear coefficient and the communication performance of the hollow-core optical fiber under test according to the optical signal to be transmitted.

[0055] Kerr nonlinearity coefficients can be characterized by measuring the inherent characteristics of the nonlinear effect itself. The SPM method utilizes the broadening of the modulation signal spectrum by the SPM effect, while the XPM method utilizes the induced phase shift of the SPM effect. Both of these methods require specific signal light sources and can only measure a limited range of fiber lengths and dispersion magnitudes, resulting in unstable nonlinearity coefficient measurements. The FWM method uses the power of newly generated frequency light waves within the optical channel to measure the nonlinearity coefficient, offering high accuracy and stability, but requires an additional pump light source and precise control of the pump and probe light to be in the same polarization state. All these characterization methods are significantly affected by experimental conditions such as fiber dispersion, input optical power, and fiber length, leading to a certain degree of divergence between measured data and theoretical values. Furthermore, according to existing reports, the Kerr nonlinearity coefficient n² of hollow-core fiber is three orders of magnitude lower than that of single-mode silica fiber, reaching the 10⁻²³ level. Therefore, traditional characterization methods with relatively coarse measurement accuracy cannot be used to accurately characterize hollow-core fibers with ultra-low nonlinearity coefficients.

[0056] This application processes the input data bitstream using a bit-loading strategy to obtain a baseband orthogonal frequency division multiplexing (OFDM) signal. The composite optical signal is then modulated using the OFDM signal to obtain a transmittable optical signal. This transmittable optical signal is then transmitted through a hollow-core optical fiber under test, allowing the receiver to characterize the Kerr effect nonlinearity coefficient and the communication performance of the fiber based on the transmittable optical signal. By mapping different modulation orders to the signal subcarriers, the high-order OFDM QAM signal to be measured is modulated onto the optical field at the transmitter. The receiver then characterizes the Kerr effect nonlinearity coefficient based on the modulated optical field signal, achieving accurate characterization of the Kerr effect nonlinearity coefficient.

[0057] 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 a device for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber that can achieve the above functions. The following description uses the device for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber as an example to illustrate this embodiment and the following embodiments.

[0058] Based on this, embodiments of this application provide a method for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber, referring to... Figure 1 , Figure 1 This is a flowchart illustrating the first embodiment of the method for characterizing the nonlinear coefficient of the Kerr effect in antiresonant hollow fiber applied to the transmitter.

[0059] In this embodiment, the method for characterizing the Kerr effect nonlinear coefficient of the anti-resonant hollow fiber includes steps S10 to S40:

[0060] Step S10: Based on the bit loading strategy, the input data bit stream is processed to obtain the baseband orthogonal frequency division multiplexing signal;

[0061] It should be noted that this embodiment proposes a two-dimensional characterization method for the Kerr nonlinear coefficients of hollow-core optical fibers based on wavelength division multiplexing-orthogonal frequency division multiplexing (WDM-OFDM) combined with bit loading technology, starting from the modulation and frequency domains. The optimal QAM modulation order is selected based on the signal-to-noise ratio (SNR) of each OFDM subcarrier to reduce measurement errors caused by signal constellation divergence under low SNR conditions. Simultaneously, constructing a high-capacity WDM transmission system makes it easier to excite the Kerr nonlinear effect, allowing for individual measurements of each WDM channel at the receiver. Averaging of identical amplitudes of QAM (orthogonal amplitude modulation) signals, including identical amplitudes in different quadrants within the same QAM modulation format and identical amplitudes of different QAM modulations, further reduces measurement errors. Finally, the average value of the Kerr nonlinear coefficients is calculated based on the two-dimensional measurement results.

[0062] Understandably, bit loading strategy refers to determining the maximum modulation order (i.e., the number of bits each subcarrier can carry) based on the SNR of each subcarrier. Subcarriers with high SNR can carry more bits, while those with low SNR carry fewer bits; this is bit loading technology. The input data bitstream refers to the data bitstream obtained from the network layer or application layer that needs to be transmitted. This data can be any form of digital information, such as text, images, and video. Baseband Orthogonal Frequency Division Multiplexing (OFDM) signal refers to the original OFDM signal before carrier modulation, i.e., the baseband OFDM signal.

[0063] In this implementation, OFDM multicarrier modulation technology ensures that the measured length of the optical fiber under test is unaffected by modulation signal parameters such as the signal baud rate. The generation of the OFDM baseband signal is implemented in Digital Signal Processing (DSP). Specifically, the input data bitstream is first converted from serial to parallel to a multi-channel parallel data stream. Bit loading technology is used, which estimates the channel state using known pilot signals or training sequences. Based on the channel estimation results, a corresponding number of bits are allocated to each subcarrier. The allocation principle is to maximize the total throughput of the system while meeting certain bit error rate requirements and power limitations. For the bits allocated to each subcarrier, symbol mapping is performed according to the adapted QAM modulation. Zero-padding is added to the mapped data to construct a guard band, and then an Inverse Fast Fourier Transform (IFFT) is performed. A cyclic prefix (CP) is added 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, i.e., the baseband OFDM signal, by an arbitrary waveform generator.

[0064] In one feasible implementation, step S10 may include steps A11 to A14:

[0065] Step A11: Perform serial-to-parallel conversion on the input data bitstream to obtain a parallel data stream;

[0066] It should be noted that parallel data streams refer to the process of breaking down a high-speed serial data bit stream into multiple low-speed parallel data streams through serial-to-parallel conversion.

[0067] Step A12: Perform data processing on the parallel data stream based on the bit loading strategy to obtain the bit allocation results for each subcarrier;

[0068] Understandably, a subcarrier refers to a series of mutually orthogonal carrier frequencies used for data transmission, and the bit allocation result refers to the result of allocating a corresponding number of bits to each subcarrier.

[0069] In practice, the channel state is estimated using known pilot signals or training sequences. Based on the channel estimation results, a corresponding number of bits are allocated to each subcarrier. The allocation principle is to maximize the total throughput of the system while meeting certain bit error rate requirements and power constraints.

[0070] In one feasible implementation, step A12 may include steps B11 to B12:

[0071] Step B11: Estimate the channel state of the parallel data stream based on the bit loading strategy to obtain the channel state estimation result;

[0072] As can be understood, channel state estimation (CSE) refers to the influence of the channel on the signal during transmission from the transmitter to the receiver in a communication system. CSE results are a quantitative description of the characteristics of the current communication channel after analyzing the received signal. These characteristics include, but are not limited to, channel response, noise level, multipath effects, and fading.

[0073] In practice, the channel state of multiple parallel data streams is estimated based on bit loading technology. That is, the channel state is estimated by using known pilot signals or training sequences, and finally the channel state estimation result is determined.

[0074] Step B12: Based on the preset bit allocation strategy and the channel state estimation result, perform bit allocation on each subcarrier of the parallel data stream to obtain the bit allocation result of each subcarrier.

[0075] It is understandable that a preset bit allocation strategy refers to a pre-set allocation strategy that maximizes the total throughput of the system while meeting certain bit error rate requirements and power limitations.

[0076] In practice, based on the bit allocation principle, that is, under the premise of meeting certain bit error rate requirements and power limitations, the total throughput of the system is maximized, and bits are allocated to each subcarrier to obtain the result of allocating a corresponding number of bits to each subcarrier.

[0077] Step A13: Based on the bit allocation results of each subcarrier and the orthogonal amplitude modulation strategy, symbol mapping is performed to obtain the target mapping data;

[0078] It is understandable that Quadrature Amplitude Modulation (QAM) strategy refers to a strategy of transmitting information by changing the amplitude and phase of the carrier signal, and target mapping data refers to the complex values ​​obtained after QAM modulation on each subcarrier.

[0079] In practical implementation, based on the channel state estimation results, bit loading technology is used to allocate a certain number of bits to each subcarrier. For example, under high signal-to-noise ratio (SNR) conditions, more bits can be allocated to a subcarrier, and a higher QAM modulation order (such as 64-QAM) can be selected, while under low SNR conditions, fewer bits may be allocated and a lower-order modulation format (such as QPSK or 4-QAM) may be selected. Based on the number of bits allocated to each subcarrier, a suitable QAM modulation format is chosen. For example, if 2 bits are allocated, 4-QAM can be selected. Then, according to the selected QAM modulation format, the bit sequence allocated to that subcarrier is mapped to a specific constellation point on the constellation diagram. For example, in 16-QAM, every 4 bits are mapped to a constellation point. According to the constellation diagram design, the I / Q components of each constellation point can be determined by lookup tables or calculation formulas, finally obtaining the complex values ​​obtained after QAM modulation on each subcarrier.

[0080] Step A14: The target mapping data is converted into a baseband orthogonal frequency division multiplexed signal by a waveform generator.

[0081] Understandably, the mapped data is zero-padding to construct a guard band, followed by an Inverse Fast Fourier Transform (IFFT). A cyclic prefix (CP) is added to the time-domain OFDM signal to prevent inter-symbol interference caused by channel dispersion. After serial-to-parallel conversion, it is converted into an analog signal, i.e., a baseband OFDM signal, via an arbitrary waveform generator.

[0082] It should be noted that, such as Figure 2 As shown, the QAM (Quadrature Amplitude Modulation) signal constellation diagram is represented in coordinate form as (x... i ,y j For a 16QAM signal, i,j = ±1, ±3, totaling 16 mapping points; for a 64QAM signal, i,j = ±1, ±3, ±5, ±7, totaling 64 mapping points; and for a 128QAM signal, i,j = ±1, ±3, ±5, ±7, ±9, ±11, totaling 128 mapping points. The mapping points in the constellation diagram rotate due to the Kerr nonlinear effect; the rotation angle is the nonlinear phase shift. Mapping points with different signal intensities experience varying degrees of nonlinear phase shift. The horizontal axis (X-axis) is labeled In-Phase, representing the in-phase component of the signal, i.e., the real part. The vertical axis (Y-axis) is labeled Quadrature, representing the quadrature component of the signal, i.e., the imaginary part. For example... Figure 3 As shown, for different QAM mappings, the nonlinear phase shift With signal strength |A| 2 The relationship between them is obtained by fitting the curve slope k, where γ is the Kerr nonlinear coefficient, and L eff This refers to the effective fiber length.

[0083] It should be noted that, as Figure 4 As shown, bit loading technology is a technique used in communication systems to optimize data transmission. Taking an OFDM (Orthogonal Frequency Division Multiplexing) system as an example, a wideband channel is divided into multiple mutually orthogonal sub-channels, each with relatively independent fading characteristics. Bit loading technology utilizes this characteristic, allocating a different number of bits to each sub-channel for data transmission based on channel conditions such as the SNR (Short-Range Noise Ratio) of each sub-channel. For sub-channels with high SNR, more bits are allocated, and a lower modulation format is used; while for sub-channels with low SNR, fewer bits are allocated, and a higher modulation format is used.

[0084] Step S20: Modulate the composite optical signal according to the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted;

[0085] It is understandable that a composite optical signal refers to a multi-wavelength optical signal synthesized from multiple optical signals of different wavelengths through wavelength division multiplexing technology, while the optical signal to be transmitted refers to the optical signal to be transmitted through hollow optical fiber.

[0086] In practical implementation, at the transmitting end, m independent light sources generate optical signals of different wavelengths, which are combined by an m×1 wavelength division multiplexer to obtain a multi-wavelength optical signal synthesized from multiple optical signals of different wavelengths through wavelength division multiplexing technology. The transmitting end adopts a scheme of continuous tunable laser plus IQ modulator to modulate the electrical signal to be transmitted onto the optical field, that is, each wavelength of optical signal is independently modulated by the baseband OFDM signal to obtain the optical signal to be transmitted through the hollow fiber.

[0087] In one feasible implementation, step S20 may include steps C11 to C12:

[0088] Step C11: Input the baseband orthogonal frequency division multiplexing signal to the signal modulator to determine the in-phase signal and the quadrature signal;

[0089] It is understandable that a signal modulator refers to an IQ (In-phase and Quadrature Modulator) modulator, which is a device used to convert baseband electrical signals into radio frequency or optical carrier signals. An in-phase signal refers to a signal component that is in phase with the carrier, usually referring to the signal part that has the same phase as the reference carrier signal. A quadrature signal refers to a signal component that is 90 degrees out of phase with the carrier, that is, the signal part that is quadrature with the reference carrier signal.

[0090] In practice, the generated baseband OFDM analog signal is input to the two input ports (in-phase component I and quadrature component Q) of the IQ modulator. These electrical signals control the bias voltage inside the IQ modulator, thereby changing the amplitude and phase of the optical signal passing through the modulator.

[0091] Step C12: Modulate the composite optical signal based on the in-phase signal and the quadrature signal to obtain the optical signal to be transmitted.

[0092] In practice, the IQ modulator modulates the amplitude and phase of the optical carrier based on the input baseband OFDM signal (I and Q components). Specifically, the in-phase and quadrature baseband signals are multiplied by the carrier signal and its 90-degree phase-shifted version, respectively. The in-phase signal is multiplied by the original phase carrier signal, while the quadrature signal is multiplied by a carrier signal with a 90-degree phase shift. The modulated in-phase and quadrature signals are then added together to form the final modulated signal. This signal contains all the frequency components of the original information, and its amplitude and phase can be adjusted according to changes in the in-phase and quadrature signals.

[0093] Step S30: The optical signal to be transmitted is transmitted through the hollow fiber under test, so that the receiving end can characterize the Kerr effect nonlinear coefficient and the communication performance of the hollow fiber under test based on the optical signal to be transmitted.

[0094] In practice, the transmitter passes the modulated optical signal through an optical amplifier before it enters the transmission link of the hollow fiber under test. This allows the receiver to characterize the Kerr effect nonlinear coefficient based on the transmitted signal and determine the corresponding bit error rate (BER) and bandwidth utilization based on the Kerr effect nonlinear coefficient, thereby characterizing the communication performance of the hollow fiber under test.

[0095] It should be noted that this embodiment utilizes bit loading technology to optimize bit allocation based on channel conditions, enabling different wavelength channels and different subcarriers within each wavelength channel to load the most suitable modulation format signal, reducing measurement errors caused by signal constellation point divergence under low SNR conditions, and eliminating measurement inaccuracies caused by differences in channel performance; it also constructs a high-capacity WDM transmission system, utilizing its high power density characteristics to easily excite the Kerr nonlinear effect; and by combining WDM and OFDM technologies, it can simultaneously acquire signal information of different wavelength channels and different subcarriers within each wavelength channel, calculating the average value of the Kerr nonlinear coefficient characterizing the medium at a specific wavelength from both the modulation domain and frequency domain dimensions.

[0096] This embodiment processes the input data bitstream using a bit-loading strategy to obtain a baseband orthogonal frequency division multiplexing (OFDM) signal. The composite optical signal is then modulated using the OFDM signal to obtain the optical signal to be transmitted. This optical signal is then transmitted through the hollow-core fiber under test, allowing the receiver to characterize the Kerr effect nonlinearity coefficient and the communication performance of the fiber. By mapping different modulation orders to the signal subcarriers, the high-order OFDM QAM signal to be measured is modulated onto the optical field at the transmitter. The receiver then characterizes the Kerr effect nonlinearity coefficient based on the modulated optical field signal, achieving accurate characterization of the Kerr effect nonlinearity coefficient.

[0097] Based on the first embodiment of this application applied to the transmitting end, in the first embodiment of this application applied to the receiving end, the content that is the same as or similar to the first embodiment applied to the transmitting end described above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 5 The method for characterizing the Kerr effect nonlinear coefficient of anti-resonant hollow fiber is applied at the receiving end, and the method further includes steps S11 to S13:

[0098] Step S11: When the optical signal to be transmitted is received from the hollow optical fiber to be tested, the optical signal to be transmitted is converted to obtain the target digital signal.

[0099] It is understandable that the target digital signal refers to the result of digitizing the received analog electrical signal.

[0100] In practice, at the receiving end, the optical signal first enters a 1×m wavelength demultiplexer, and after being separated by wavelength, each WDM channel is measured individually. 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.

[0101] Step S12: Perform data processing on the target digital signal to obtain the target processed signal;

[0102] It is understandable that the target processing signal refers to the signal after digital signal processing (DSP) of the digital signal.

[0103] In specific implementation, the OFDM signal processing flow in this embodiment includes synchronization, phase noise compensation, serial-to-parallel conversion, CP removal, FFT, demodulation and QAM mapping, parallel-to-serial conversion, etc., and finally obtains the target processed signal.

[0104] Step S13: Based on the target processing signal and the preset Kerr effect coefficient model, the Kerr effect nonlinear coefficient is obtained, and the communication performance of the hollow fiber under test is characterized.

[0105] It is understandable that the presupposed Kerr effect coefficient model refers to the constellation mapping-Kerr nonlinear mathematical model.

[0106] In practical implementation, QAM signal mapping of corresponding modulation orders is performed for signals with different modulation formats. The average amplitude of the same QAM signal is taken, including the same amplitude in different quadrants within the same QAM modulation format and the same amplitude across different QAM modulations. Then, the center position of each constellation point is characterized using the K-means clustering algorithm. Based on the constellation mapping-Kerr nonlinear mathematical model, the Kerr nonlinear coefficient n² of the fiber under test is finally calculated. Based on multiple sets of measurement results across multiple subcarrier signals and different QAM modulation formats, the average value of the Kerr nonlinear coefficient of the fiber under test is calculated. Finally, the communication performance of the fiber under test is characterized by the average value of the Kerr nonlinear coefficient.

[0107] In one feasible implementation, step S13 may include steps D11 to D13:

[0108] Step D11: Map the quadrature amplitude modulation signal of the corresponding modulation order according to the modulation format of the target processing signal to obtain the quadrature amplitude modulation signal corresponding to the target processing signal;

[0109] As we can understand it, modulation format refers to the method or technique of converting digital information into analog signals. Different modulation formats represent different bit sequences by changing certain characteristics of the carrier (such as amplitude, frequency, or phase). Common modulation formats include Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), Phase Shift Keying (PSK), and Quadrature Amplitude Modulation (QAM). The modulation order refers to the number of different states that each symbol can represent, which determines how many bits of information each symbol can carry. A quadrature amplitude modulated signal refers to a signal generated by quadrature amplitude modulation technology. It uses two orthogonal carriers (I and Q components) to transmit amplitude and phase information simultaneously and can be visually represented by a constellation diagram.

[0110] In practical implementation, for signals with different modulation formats, QAM signals of corresponding modulation orders are mapped to obtain quadrature amplitude modulation signals. For example, according to the modulation order (16-QAM in groups of 4 bits, 64-QAM in groups of 6 bits), the input bitstream is grouped and mapped to corresponding points on the constellation diagram. Constellation points with the same amplitude are found within the same modulation format or between different modulation formats. The actual receiving positions of these constellation points with the same amplitude are averaged to reduce the influence of noise and other nonlinear effects, thereby more accurately determining the center position of the constellation diagram.

[0111] Step D12: Calculate the average of the same amplitudes corresponding to the quadrature amplitude modulation signals to obtain the average same amplitude.

[0112] It is understandable that the average amplitude refers to the average value of the actual receiving positions of constellation points with the same or similar amplitude.

[0113] In practice, the same amplitude of the QAM signal is averaged, including the same amplitude in different quadrants within the same QAM modulation format and the same amplitude in different QAM modulations. This effectively reduces random fluctuations caused by noise or other interference factors, thereby improving the accuracy of constellation center position estimation.

[0114] Step D13: Input the average equal amplitude into the preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficient.

[0115] In practice, the average value of the actual receiving positions of constellation points with the same or similar amplitudes is input into the constellation mapping-Kerr nonlinear mathematical model, thereby obtaining the Kerr nonlinear coefficient n2 value of the fiber under test output by the model.

[0116] In one feasible implementation, step D13 may include steps E11 to E12:

[0117] Step E11: Input the average equal amplitude into the preset Kerr effect coefficient model to obtain the target Kerr effect coefficients corresponding to each subcarrier signal and each orthogonal amplitude modulation format;

[0118] Understandably, the average value of the actual receiving positions of constellation points with the same or similar amplitudes is input into the constellation mapping-Kerr nonlinear mathematical model to calculate the Kerr nonlinear coefficient n2 of the fiber under test. That is, the target Kerr effect coefficient is obtained based on multiple sets of measurement results across two dimensions: multiple subcarrier signals and different QAM modulation formats.

[0119] Step E12: The mean of the multiple target Kerr effect coefficients is calculated to obtain the Kerr effect nonlinear coefficient.

[0120] In practice, the average value of the Kerr nonlinear coefficient of the fiber under test is obtained by averaging multiple sets of measurement results based on multiple subcarrier signals and different QAM modulation formats.

[0121] It should be noted that, such as Figure 6 As shown, this embodiment constructs a high-capacity WDM (Wavelength Division Multiplexing) transmission system, making it easy to excite the Kerr nonlinear effect. At the transmitting end, m independent light sources generate optical signals of different wavelengths, which are combined by an m×1 wavelength division multiplexer. Utilizing OFDM multicarrier modulation technology, the measured length of the fiber under test is unaffected by modulation signal parameters such as the signal baud rate. The generation of the OFDM baseband signal is implemented in digital signal processing (DSP), with the transmitting end DSP, such as... Figure 7 As shown in (a), the input data bitstream is first converted from serial to parallel to a multi-channel parallel data stream. Bit loading technology is used, which estimates the channel state using known pilot signals or training sequences. Based on the channel estimation results, a corresponding number of bits are allocated to each subcarrier. The allocation principle is to maximize the total throughput of the system while meeting certain bit error rate requirements and power constraints. For the bits allocated to each subcarrier, symbol mapping is performed according to the adapted QAM modulation. Zero padding is added to the mapped data to construct a guard band, and then an Inverse Fast Fourier Transform (IFFT) is performed. A cyclic prefix (CP) is added 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, i.e., a baseband OFDM signal, by an arbitrary waveform generator. Multiple lasers generate optical signals of different wavelengths, and an optical combiner combines these signals into a single composite optical signal. The transmitting end employs a continuously tunable laser with an IQ modulator to modulate the electrical signal to be transmitted onto the optical field; that is, each wavelength of the optical signal is independently modulated by the baseband OFDM signal. The modulated optical signal, after being amplified by an optical amplifier, enters the hollow-core fiber transmission link under test. The input optical power is controlled by the optical amplifier and an adjustable optical attenuator to better excite nonlinear effects. At the receiving end, the optical signal first enters a 1×m wavelength demultiplexer, and after wavelength separation, each WDM channel is measured individually. 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. The OFDM signal processing flow is as follows: Figure 7As shown in (b), the process includes synchronization, phase noise compensation, serial-to-parallel conversion, CP removal, FFT, demodulation and QAM mapping, and parallel-to-serial conversion. For different modulation formats, QAM signal mapping of the corresponding modulation order is performed. The average amplitude of the same QAM signal is taken, including the same amplitude in different quadrants within the same QAM modulation format and the same amplitude across different QAM modulations. The K-means clustering algorithm is then used to characterize the center position of each constellation point. Based on the constellation mapping-Kerr nonlinear mathematical model, the Kerr nonlinear coefficient n² of the fiber under test is finally calculated. The average value of the Kerr nonlinear coefficient of the fiber under test is calculated based on multiple sets of measurement results across multiple subcarrier signals and different QAM modulation formats.

[0122] This embodiment obtains the target Kerr effect coefficients for each subcarrier signal and each orthogonal amplitude modulation format by inputting the average amplitude of the same value into a preset Kerr effect coefficient model. The Kerr effect nonlinear coefficient is then calculated by averaging multiple target Kerr effect coefficients. At the receiving end, each WDM channel is individually measured, and the received digital signal is demodulated using OFDM-QAM modulation. For different subcarrier signals, a QAM constellation diagram of the corresponding modulation order with nonlinear impairment is recovered. The average amplitude of the QAM signals is taken, and a clustering analysis algorithm is used to accurately characterize the center position of the QAM constellation diagram, calculating the corresponding Kerr nonlinear coefficient n2. This achieves the calculation of the average value of the Kerr nonlinear coefficient representing the medium from both the modulation and frequency domains, thereby improving the accuracy of the Kerr nonlinear coefficient calculation.

[0123] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the method for characterizing the nonlinear coefficient of the Kerr effect in antiresonant hollow fiber in this application. Any simple transformations based on this technical concept are within the protection scope of this application.

[0124] This application also provides a device for characterizing the Kerr effect nonlinear coefficient of anti-resonant hollow fiber; please refer to [reference needed]. Figure 8 The anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device is applied at the transmitting end, and the device includes:

[0125] Processing module 10 is used to process the input data bit stream based on a bit loading strategy to obtain a baseband orthogonal frequency division multiplexing signal;

[0126] Modulation module 20 is used to modulate the composite optical signal according to the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted;

[0127] The characterization module 30 is used to transmit the optical signal to be transmitted through the hollow fiber under test, so that the receiving end can characterize the Kerr effect nonlinear coefficient and the communication performance of the hollow fiber under test based on the optical signal to be transmitted.

[0128] Optionally, the processing module 10 is further configured to:

[0129] The input data bitstream is converted from serial to parallel to obtain a parallel data stream;

[0130] The parallel data stream is processed based on a bit loading strategy to obtain the bit allocation results for each subcarrier;

[0131] Based on the bit allocation results of each subcarrier and the orthogonal amplitude modulation strategy, symbol mapping is performed to obtain the target mapping data;

[0132] The target mapping data is converted into a baseband orthogonal frequency division multiplexed signal by a waveform generator.

[0133] Optionally, the processing module 10 is further configured to:

[0134] The channel state of the parallel data stream is estimated based on the bit loading strategy to obtain the channel state estimation result;

[0135] Based on the preset bit allocation strategy and the channel state estimation results, bit allocation is performed on each subcarrier of the parallel data stream to obtain the bit allocation results for each subcarrier.

[0136] Optionally, the modulation module 20 is further configured to:

[0137] Input the baseband orthogonal frequency division multiplexed signal to the signal modulator to determine the in-phase signal and the quadrature signal;

[0138] The composite optical signal is modulated based on the in-phase signal and the quadrature signal to obtain the optical signal to be transmitted.

[0139] This application also provides a device for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber, which is applied at the receiving end, and the device includes:

[0140] The conversion module 101 is used to convert the optical signal to be transmitted into a target digital signal when it receives the optical signal to be transmitted from the hollow optical fiber to be tested.

[0141] The calculation module 102 is used to perform data processing on the target digital signal to obtain the target processed signal;

[0142] The calculation module 102 is also used to characterize the target processing signal and the preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficient and characterize the communication performance of the hollow fiber under test.

[0143] The computing module 102 is also used for:

[0144] Based on the modulation format of the target processing signal, an orthogonal amplitude modulation signal of the corresponding modulation order is mapped to obtain the orthogonal amplitude modulation signal corresponding to the target processing signal;

[0145] The average amplitude of the same value corresponding to the quadrature amplitude modulation signal is calculated to obtain the average same amplitude.

[0146] Input the average equal amplitude into the preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficient.

[0147] The computing module 102 is also used for:

[0148] Input the average equal amplitude into the preset Kerr effect coefficient model to obtain the target Kerr effect coefficients corresponding to each subcarrier signal and each orthogonal amplitude modulation format;

[0149] The Kerr effect nonlinear coefficient is obtained by averaging the multiple target Kerr effect coefficients.

[0150] The anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device provided in this application employs the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method described in the above embodiments, which can solve the technical problem of low accuracy in calculating the Kerr effect nonlinear coefficient using existing single-mode fiber nonlinear measurement methods. Compared with the prior art, the beneficial effects of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device provided in this application are the same as those of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method provided in the above embodiments, and other technical features in the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device are the same as those disclosed in the methods of the above embodiments, and will not be repeated here.

[0151] This application provides a device for characterizing the Kerr effect nonlinear coefficient of antiresonant 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 execute the method for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber in the above embodiment 1.

[0152] The following is for reference. Figure 9This document illustrates a structural schematic diagram of a device suitable for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber in embodiments of this application. The device for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber in embodiments of this application 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 9 The device for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments of this application.

[0153] like Figure 9 As shown, the device for characterizing the Kerr effect nonlinear coefficients of antiresonant hollow fiber may include a processing unit 1001 (e.g., a central processing unit, a graphics processing unit, 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 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 anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device to communicate wirelessly or wiredly with other devices to exchange data. Although the figure shows anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization devices 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.

[0154] 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.

[0155] The anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device provided in this application employs the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method described in the above embodiments, which can solve the technical problem of low accuracy in calculating the Kerr effect nonlinear coefficient using existing single-mode fiber nonlinear measurement methods. Compared with the prior art, the beneficial effects of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device provided in this application are the same as those of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method provided in the above embodiments, and other technical features in this anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device are the same as those disclosed in the previous embodiment method, and will not be repeated here.

[0156] 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.

[0157] The above description is merely a specific embodiment 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.

[0158] 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 method for characterizing the nonlinear coefficient of the Kerr effect in anti-resonant hollow fiber in the above embodiments.

[0159] 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.

[0160] The aforementioned computer-readable storage medium may be included in the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device; or it may exist independently and not assembled into the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device.

[0161] The aforementioned computer-readable storage medium carries one or more programs. When these programs are executed by the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization device, the device performs the following actions: processes the input data bitstream based on a bit loading strategy to obtain a baseband orthogonal frequency division multiplexing (OFDM) signal; modulates the composite optical signal according to the OFDM signal to obtain a transmission optical signal; and transmits the transmission optical signal through the hollow fiber under test, so that the receiving end characterizes the Kerr effect nonlinear coefficient and the communication performance of the hollow fiber under test based on the transmission optical signal.

[0162] 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).

[0163] 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.

[0164] 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.

[0165] 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 characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber. This solves the technical problem of low accuracy in calculating the Kerr effect nonlinear coefficient using existing single-mode fiber nonlinearity measurement methods. 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 antiresonant hollow fiber Kerr effect nonlinear coefficient characterization method provided in the above embodiments, and will not be elaborated upon here.

[0166] 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 characterizing the nonlinear coefficient of the Kerr effect in antiresonant hollow fiber.

[0167] The computer program product provided in this application can solve the technical problem of low accuracy in calculating the Kerr effect nonlinear coefficient of existing single-mode fiber nonlinear measurement methods. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as those of the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method provided in the above embodiments, and will not be repeated here.

[0168] The above description is only a part of the embodiments of this application and does 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 for characterizing the Kerr effect nonlinear coefficients in antiresonant hollow-core optical fibers, characterized in that, The method for characterizing the Kerr effect nonlinear coefficient of anti-resonant hollow fiber is applied to the transmitter. The method includes: The input data bitstream is processed based on a bit loading strategy to obtain a baseband orthogonal frequency division multiplexed signal. The composite optical signal is modulated according to the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted. The optical signal to be transmitted is transmitted through the hollow-core optical fiber under test, so that the receiving end can characterize the Kerr effect nonlinear coefficient and the communication performance of the hollow-core optical fiber under test based on the optical signal to be transmitted.

2. The method as described in claim 1, characterized in that, The step of processing the input data bitstream based on the bit loading strategy to obtain the baseband orthogonal frequency division multiplexed signal includes: The input data bitstream is converted from serial to parallel to obtain a parallel data stream; The parallel data stream is processed based on a bit loading strategy to obtain the bit allocation results for each subcarrier; Based on the bit allocation results of each subcarrier and the orthogonal amplitude modulation strategy, symbol mapping is performed to obtain the target mapping data; The target mapping data is converted into a baseband orthogonal frequency division multiplexed signal by a waveform generator.

3. The method as described in claim 2, characterized in that, The step of processing the parallel data stream based on the bit loading strategy to obtain the bit allocation results of each subcarrier includes: The channel state of the parallel data stream is estimated based on the bit loading strategy to obtain the channel state estimation result; Based on the preset bit allocation strategy and the channel state estimation results, bit allocation is performed on each subcarrier of the parallel data stream to obtain the bit allocation results for each subcarrier.

4. The method as described in claim 1, characterized in that, The step of modulating the composite optical signal based on the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted includes: Input the baseband orthogonal frequency division multiplexed signal to the signal modulator to determine the in-phase signal and the quadrature signal; The composite optical signal is modulated based on the in-phase signal and the quadrature signal to obtain the optical signal to be transmitted.

5. A method for characterizing the Kerr effect nonlinear coefficients in anti-resonant hollow-core optical fibers, characterized in that, The method for characterizing the Kerr effect nonlinear coefficient of anti-resonant hollow fiber is applied at the receiving end, and the method includes: When the optical signal to be transmitted is received from the hollow optical fiber under test, the optical signal to be transmitted is converted to obtain the target digital signal; The target digital signal is processed to obtain the target processed signal; Based on the target processed signal and the preset Kerr effect coefficient model, the Kerr effect nonlinear coefficient is obtained, and the communication performance of the hollow fiber under test is characterized.

6. The method as described in claim 5, characterized in that, The step of characterizing the target processed signal and the preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficients includes: Based on the modulation format of the target processing signal, an orthogonal amplitude modulation signal of the corresponding modulation order is mapped to obtain the orthogonal amplitude modulation signal corresponding to the target processing signal; The average amplitude of the same value corresponding to the quadrature amplitude modulation signal is calculated to obtain the average same amplitude. Input the average equal amplitude into the preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficient.

7. The method as described in claim 6, characterized in that, The step of inputting the average equal amplitude into a preset Kerr effect coefficient model to obtain the Kerr effect nonlinear coefficients includes: Input the average equal amplitude into the preset Kerr effect coefficient model to obtain the target Kerr effect coefficients corresponding to each subcarrier signal and each orthogonal amplitude modulation format; The Kerr effect nonlinear coefficient is obtained by averaging the multiple target Kerr effect coefficients.

8. A device for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber, characterized in that, The device includes: The processing module is used to process the input data bit stream based on the bit loading strategy to obtain the baseband orthogonal frequency division multiplexing signal; The modulation module is used to modulate the composite optical signal according to the baseband orthogonal frequency division multiplexing signal to obtain the optical signal to be transmitted; The characterization module is used to transmit the optical signal to be transmitted through the hollow fiber under test, so that the receiving end can characterize the Kerr effect nonlinear coefficient and the communication performance of the hollow fiber under test based on the optical signal to be transmitted.

9. A device for characterizing the Kerr effect nonlinear coefficient of antiresonant hollow fiber, characterized in that, The 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 method for characterizing the nonlinear coefficient of the Kerr effect in antiresonant hollow fiber as described in any one of claims 1 to 7.

10. A system for characterizing the Kerr effect nonlinear coefficients in antiresonant hollow-core optical fibers, characterized in that, The anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization system includes a transmitter and a receiver. The transmitter performs the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method as described in any one of claims 1 to 4, and the receiver performs the anti-resonant hollow fiber Kerr effect nonlinear coefficient characterization method as described in any one of claims 5 to 7.

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