90 results about "Nonlinear coefficient" patented technology

The invention belongs to the technical field of nondestructive testing, and particularly relates to a detection method for quantitatively evaluating fatigue damage in a pipeline through a nonlinear ultrasonic technology. 316 stainless steel and SA335GRP-11 ferrite steel samples are adopted, a welding seam area is formed through V-shaped groove welding, fatigue loading is conducted, and actual pipeline fatigue damage is simulated; for the samples with different fatigue cycles, nonlinear response signals of the samples are obtained; fourier transform is carried out on the obtained signal to obtain an energy spectrum of the signal, and energy changes of the signal on a fundamental frequency band and a second harmonic frequency band are analyzed; and calculating a nonlinear coefficient, and analyzing a change rule of the nonlinear coefficient along with fatigue cycles, so that the evolution process of fatigue damage in the pipeline is evaluated. According to the method, energy is used for replacing the amplitude value, on the basis of the formula principle, integration is used for replacing the amplitude value to improve the intensity of the characterization nonlinear ultrasonic signal, the early stage of damage and the later stage of crack initiation are detected, and reliable guarantee is provided for safe operation of an industrial pipeline system.

The invention discloses a non-destructive testing stress evaluation method based on a nonlinear ultrasonic Lamb wave static component, and belongs to the technical field of stress detection, and the method comprises the following steps: S1, constructing a Rayleigh-Lamb equation introducing an elastomer nonlinear theory, and further determining a Lamb wave frequency dispersion curve of a to-be-detected plate, the excitation frequency and the excitation mode of the excitation source are determined according to the Lamb wave frequency dispersion curve; s2, exciting lamb waves for determining excitation frequency and excitation mode at one end of the stress detection area of the plate to be detected, and receiving and extracting corresponding signals through the other end of the stress detection area; s3, inverting the phase of the extracted signal, and exciting and receiving the inverted signal again; and S4, processing the received signal, and calculating an ultrasonic nonlinear coefficient as an evaluation parameter of the stress state of the plate to be detected. According to the invention, the selection of the fundamental wave frequency and mode is more flexible, the related parameters of the high-attenuation material can be measured, and the early damage and stress state in the material can be effectively evaluated.

The invention discloses a controllable adjustment method and system for the motion state of a space optical soliton, and belongs to the field of optics, and the method comprises the steps: carrying out the periodic modulation of a transverse refractive index and a nonlinear coefficient in an optical lattice; constructing a nonlinear Schrodinger equation for describing light beam transmission characteristics based on the periodically modulated optical lattice; solving the nonlinear Schrodinger equation by using an equivalent particle method to obtain an optical soliton center position; and based on the center position of the optical soliton, the controllable adjustment of the motion state of the space optical soliton is completed through numerical simulation verification. According to the method, the transverse refractive index and the nonlinear coefficient are periodically modulated through the optical lattice, a new nonlinear Schrodinger equation is deduced and obtained, the nonlinear Schrodinger equation is solved through an equivalent particle method, several states of transmission of optical solitons in the optical lattice are analyzed, the correctness of the equation is verified through numerical values, and the nonlinear Schrodinger equation is obtained. The problem of motion trail control when optical solitons are transmitted in optical lattices is solved.

The invention provides a comprehensive noise reduction performance evaluation method for a nonlinear ultrasonic detection signal noise reduction algorithm, and the method comprises the steps: firstly constructing a multi-working-condition noise reduction performance pre-screening mechanism based on error band analysis based on early-stage experimental data, and then introducing a radar map as an evaluation tool for the comprehensive noise reduction effect of the signal noise reduction algorithm. The noise reduction effects of a moving average method (MA), a spectral subtraction method (SS), a short-time Fourier transform method (STFT), a wavelet transform method (WT) and an orthogonal matching pursuit algorithm (OMP) are compared, and finally a signal noise reduction algorithm with the optimal comprehensive efficiency is screened out. On the basis of algorithm optimization, quantitative mapping rules between microcrack three-dimensional geometric parameters and relative nonlinear coefficients are analyzed through regression modeling, and the significant level of the correlation degree of the relative nonlinear coefficients and microcrack size parameters is effectively improved; and a high-confidence theoretical support is provided for quantitative nondestructive detection of the microcracks in engineering practice.

The invention discloses a light field regulation and control device capable of simultaneously realizing dual-frequency different diffraction functions, which is characterized in that lithium niobate crystals are processed by the device in combination with a laser processing technology and a vacuum quenching technology; the laser processing technology erases the nonlinear coefficient of the lithium niobate crystal and changes the refractive index at the same time; the vacuum quenching process generates a pyroelectric field to polarize the ferroelectric domain of the lithium niobate crystal, changes the sign of a nonlinear coefficient, and does not influence the refractive index; the grating arrays processed by the two technologies are perpendicular to each other and are nested together, and one-dimensional linear diffraction and two-dimensional nonlinear diffraction are respectively carried out on a fundamental frequency light field based on the change of a refractive index and a nonlinear coefficient. And due to different structures formed by changing the refractive index and the nonlinear coefficient, the fundamental frequency light and the frequency doubling light can respectively realize light field regulation and control with different functions.

The invention belongs to the technical field of ultrasonic imaging, and particularly relates to an ultrasonic nonlinear parameter imaging method and system, a medium and a program product. The method comprises the following steps: calculating a fundamental signal and a harmonic signal based on an ultrasonic echo RF signal; extracting the amplitude of the fundamental wave signal and the amplitude of the harmonic wave signal, and calculating to obtain a fundamental wave amplitude ratio and a harmonic wave amplitude ratio; calculating an initial value of a nonlinear coefficient according to a ratio of the fundamental wave amplitude ratio to the harmonic wave amplitude ratio, and estimating a value range of the nonlinear coefficient by using a Newton iteration method; and generating an ultrasonic image based on the value range of the nonlinear coefficient. In the ultrasonic non-linear parameter imaging process, a method for solving a non-linear coefficient by adopting a Newton iteration method is further disclosed, so that the dynamic range of the estimated non-linear coefficient value is expanded, the distinguishing between normal tissues and focus tissues in an obtained ultrasonic image is more obvious, and the sensitivity is higher.

The invention relates to a cable accessory-based insulation silicone rubber thermal aging state detection method, apparatus and device. The method comprises the steps of obtaining a correlation model and a to-be-detected sample; transmitting ultrasonic waves to the to-be-detected sample for aging test to obtain a primary echo time domain signal; processing the primary echo time domain signal to obtain a spectrogram, and extracting a fundamental wave amplitude and a second harmonic amplitude from the spectrogram; calculating a relative nonlinear coefficient according to the fundamental wave amplitude and the second harmonic amplitude; and inputting the relative nonlinear coefficient into the correlation model for analysis to obtain the thermal aging degree. The method comprises the following steps: transmitting and receiving ultrasonic waves to and from a sample to be detected to obtain a primary echo time-domain signal, processing the primary echo time-domain signal to obtain a relative nonlinear coefficient, and inputting the relative nonlinear coefficient into a correlation model to analyze and evaluate the thermal aging degree of the identified thermal aging state of the sample to be detected. The microstructure change of the to-be-detected sample caused by thermal aging can be accurately captured, and the thermal aging state can be accurately evaluated.

The invention provides a microcrack positioning method and system of a nonlinear ultrasonic mixing signal, and relates to the technical field of nondestructive testing. The method comprises the following steps: exciting signals with different frequencies into a test piece for resonance, collecting echo signals generated by signal resonance at a plurality of measurement points, performing Fourier transform processing on the plurality of echo signals to generate a prediction spectrogram, and calculating a prediction nonlinear coefficient of a microcrack position according to the prediction spectrogram; the method comprises the following steps: performing displacement processing on a simulation test piece model, simulating material displacement caused by propagation of a frequency mixing signal needing to be excited in a material, obtaining a displacement relation graph, performing Fourier transform processing, generating a simulation spectrogram, and calculating a simulation nonlinear coefficient of a simulation microcrack position according to the simulation spectrogram. The simulated nonlinear coefficient is used for verifying and predicting the nonlinear coefficient to obtain the position of the micro-crack, so that the micro-crack is accurately positioned, the micro-crack can be effectively identified and positioned, and a high-sensitivity and high-resolution detection result is provided.

The invention discloses a carbon fiber prepreg laying layer defect detection method and system based on nonlinear guided waves, and the method comprises the steps: arranging excitation and receiving sensor arrays at the inner side and the outer side of a carbon fiber prepreg region, transmitting Hanning window modulation sine wave signals through the excitation sensor arrays, arranging an acoustic metamaterial layer on the surface of a detection region, and detecting the defects of the carbon fiber prepreg laying layer through the acoustic metamaterial layer. An excitation sensor array is divided into two groups to emit different phase signals, so that wave beams are focused at specified positions in a detection area and interact with each other, normalized time-frequency analysis is performed on reference signals and to-be-detected signals, second harmonic components and sideband frequency components are extracted, a relative nonlinear coefficient is calculated based on a signal difference value, and the relative nonlinear coefficient is calculated. And processing and receiving full matrix data of the sensor array by adopting a full focusing method, and reconstructing a nonlinear coefficient distribution image in the carbon fiber prepreg to carry out defect positioning and quantitative evaluation on the acoustic metamaterial layer. According to the invention, accurate and reliable detection and early warning of micro-defects in the carbon fiber prepreg laying process are realized.

The invention discloses a 2-micron-waveband adjustable all-fiber high-repetition-frequency pulse light source generator, belongs to the technical field of laser light source manufacturing, and aims to solve the problem that an existing 2-micron-waveband passive all-fiber mode-locked pulse laser light source is difficult to give consideration to fs-magnitude narrow pulse width and ultra-short-cavity-length high-fundamental-frequency repetition frequency output. The laser comprises a semiconductor laser pumping source, a wavelength division multiplexer, an extrusion type polarization controller I, a polarization-maintaining highly-doped gain fiber, an extrusion type polarization controller II, a long cone region tapering micro-nano fiber, a 2 * 2 fiber coupler and a fiber Faraday mirror. According to the invention, the long-cone micro-nanofiber is introduced into the cavity, and the long-cone micro-nanofiber has the characteristic of high nonlinear coefficient, so that the cavity length can be greatly shortened, enough nonlinear phase shift can be accumulated, and fs-magnitude ultrashort pulse can be output. The device is low in loss, stable in performance and easy to integrate with other optical fiber systems. The laser can be applied to the fields of optical communication, non-metallic material processing, laser medical treatment, intermediate infrared laser pumping sources and the like.

The invention relates to the technical field of temperature compensation, in particular to a temperature compensation method and system based on an inertial device, and provides the following scheme that the inertial device is calibrated, output characteristic data under different temperature conditions are obtained, and compensation parameters are calculated in combination with a real-time temperature state. The method comprises the following steps: modeling output characteristic data through adaptive fuzzy reasoning, and calculating a temperature dependency coefficient and a temperature nonlinear coefficient; analyzing the relationship between the filtering signal and the temperature change by using a grey correlation method; calculating an influence factor and performing temperature compensation on the output signal according to the factor; and adopting a genetic algorithm to carry out optimization adjustment and iterative updating on compensation parameters, and finally outputting a signal subjected to temperature compensation. According to the invention, the output precision and stability of the inertial device in a temperature change environment are improved, and the method has high adaptability and reliability.

The invention discloses an XLPE cable insulation defect type identification and severity evaluation method. The method comprises the following steps: S1, sample preparation, S2, data acquisition, S3, feature parameter extraction, S4, feature fusion and preprocessing, S5, hierarchical model construction, S6, model training and verification, and S7, model practical application. According to the method, through multi-dimensional feature fusion, dielectric loss (aging overall characterization) and a nonlinear coefficient (local defect sensitivity) are combined, and the recognition accuracy is improved; meanwhile, through a hierarchical model, the defect type is determined firstly, and then the severity is evaluated in a targeted manner, so that feature confusion of different defects can be avoided, and accurate classification and severity quantitative evaluation of the XPLE cable insulation defects are realized; the problem that no diagnosis technology for other defects except for the partial discharge defect exists in XLPE cable insulation at present is solved.

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

The invention discloses a high-order frequency doubling orbital angular momentum mode generation device, which is characterized in that a laser direct writing technology is utilized to erase a second-order nonlinear coefficient in a lithium niobate crystal to form a three-dimensional fork-shaped grating array; each layer of fork-shaped grating is a pattern obtained by performing non-collinear interference on an OAM mode with topological charge of 10 and a Gaussian mode according to a holographic theory and then performing binarization processing; when each fork-shaped grating is processed, the central area of the fork-shaped grating is avoided; a fundamental frequency light beam meets a quasi-phase matching condition through the processed lithium niobate crystal, light field regulation and control are carried out while frequency multiplication conversion is carried out, and generation of a high-quality high-order nonlinear OAM mode is achieved.

Optical transmission property estimation device comprising:a transmission waveform restoration unit configured to restore a transmission signal from a reception signal obtained by receiving an optical signal by a coherent detection system; andan estimation unit configured to estimate an optical power distribution in a transmission line by estimating a nonlinear coefficient in a propagation equation of a light wave by a linear least square method based on the restored transmission signal and the reception signal.

The invention discloses an uncertainty analysis method and device for wind power prediction and a storage medium, and relates to the technical field of wind power prediction, and the method comprises the steps: carrying out the data sensing of a target wind power plant region through a plurality of sensors, and obtaining a plurality of operation data sets of a wind power plant; performing wind power similarity analysis based on the plurality of operation data sets, determining a nonlinear coefficient, and training and constructing a Gaussian regression model; inputting variables into the Gaussian regression model, and outputting a regression data set; performing uncertainty analysis on the wind power prediction data according to the data uncertainty interval, and determining a confidence interval of the wind power; and performing control analysis on the target wind power plant, and formulating a scheduling control strategy. According to the method and the device, the technical problem of low operation efficiency and reliability of the wind power plant caused by inaccurate prediction of the wind power in the prior art is solved, and the technical effects of realizing accurate prediction of the wind power and improving the operation efficiency and reliability of the wind power plant are achieved.

The invention discloses an anti-floating plate displacement calculation method and system considering soil body distribution rigidity and material nonlinearity. The calculation method comprises the following steps that upward buoyancy borne by a tunnel segment below an anti-floating plate is calculated; calculating the maximum load of the floating force diffused to the overlying soil of the tunnel segment; calculating the equivalent uniform load of the anti-floating plate based on the non-uniform diffusion of the maximum load of the overlying soil body; and based on the elastic foundation beam theory, calculating the displacement of the anti-floating plate by considering the soil body distribution rigidity and the nonlinear coefficient of the anti-floating plate material. According to the method, the characteristics of soil body distribution rigidity and material nonlinearity are combined, and the real displacement condition of the anti-floating plate under the complex working condition can be reflected more accurately.

The present invention discloses a method for measuring the acoustic nonlinear coefficient of a material by using the phase relationship. It uses finite-amplitude ultrasound to perform non-destructive testing on a material with mechanical nonlinearity, performs Hilbert transform processing on the detected and / or calculated displacement signal or particle vibration velocity signal to obtain the phase of the nonlinear signal, and then obtains the normalized angular frequency through numerical calculation, so as to measure the acoustic nonlinear coefficient according to the maximum value of the normalized angular frequency. The method of the present invention is simpler, and can expand the experimental conditions. The nonlinear coefficient can still be measured under conditions of longer distance, stronger excitation, and larger nonlinear coefficient, and the test results are more accurate; the applicable conditions of the present invention can approach the generation position of the shock wave.

The present invention discloses a method for determining an on-orbit calibration nonlinear coefficient of a satellite-borne microwave radiometer before launch. The method comprises: sequentially observing three calibration blackbodies by the satellite-borne microwave radiometer to be measured within a scanning cycle to obtain observation voltages and brightness temperatures corresponding to three different temperatures; the three calibration blackbodies comprise: a cold calibration blackbody at the boiling point of liquid nitrogen, a hot calibration blackbody at ambient temperature, and a calibration blackbody at an intermediate temperature between the cold and ambient temperatures; obtaining a secondary calibration curve from the observation voltages and brightness temperatures at the three different temperatures; determining virtual cold space data from the secondary calibration curve through virtual cold space observation; if observation data at an intermediate value between the virtual cold space data and the hot calibration blackbody data can be determined from the virtual cold space data and the hot calibration blackbody data, calculating the nonlinear coefficient from the virtual cold space data and the hot calibration blackbody data; otherwise, calculating the nonlinear coefficient from the virtual cold space data, the hot calibration blackbody data, and the intermediate temperature blackbody data.

This invention belongs to the field of ultrasound imaging technology, specifically relating to an ultrasound nonlinear parameter imaging method, system, medium, and program product. The method includes: calculating a fundamental wave signal and harmonic signals based on ultrasound echo RF signals; extracting the amplitudes of the fundamental wave signal and the harmonic signals, and calculating the fundamental wave amplitude ratio and harmonic amplitude ratio; calculating an initial value of the nonlinear coefficient based on the ratio between the fundamental wave amplitude ratio and the harmonic amplitude ratio, and estimating the range of values ​​for the nonlinear coefficient using Newton's iteration method; and generating an ultrasound image based on the range of values ​​for the nonlinear coefficient. In the process of ultrasound nonlinear parameter imaging, a method for solving the nonlinear coefficient using Newton's iteration method is further disclosed, thereby expanding the dynamic range of the estimated nonlinear coefficient values, resulting in a clearer distinction between normal tissue and lesion tissue in the obtained ultrasound image, and higher sensitivity.

Systems and methods for clamping force estimation are provided. In one example, the operations include generating a displacement-torque curve based on displacement data and motor torque data of an electric motor of the EMB system for a braking event having a switchover time. The operations also include determining a high torque value and a low torque value at the switchover time from the displacement-torque curve. The operations further include calculating a friction coefficient based on the high torque value and the low torque value. The operations further include determining a nonlinear coefficient from the displacement-torque curve. The operations include estimating a clamping force for a constant speed based on the friction coefficient and the nonlinear coefficient.

The invention discloses a light field control device for realizing dual-frequency different diffraction functions at the same time, characterized in that the device combines a laser processing technology and a vacuum quenching technology to process a lithium niobate crystal; the laser processing technology erases the nonlinear coefficient of the lithium niobate crystal and changes the refractive index at the same time; the vacuum quenching technology generates a pyroelectric field to polarize the ferroelectric domain of the lithium niobate crystal, changes the sign of the nonlinear coefficient, and does not affect the refractive index; the grating arrays processed by these two processes are perpendicular to each other and nested together, and based on the changes in the refractive index and the nonlinear coefficient, one-dimensional linear diffraction and two-dimensional nonlinear diffraction are respectively performed on the fundamental frequency light field; because the structures formed by the changes in the refractive index and the nonlinear coefficient are different, the fundamental frequency light and the doubled frequency light can respectively realize light field control with different functions.

The application discloses a controllable adjustment method and system for a spatial optical soliton motion state, and belongs to the optical field, and comprises the following steps: periodically modulating a transverse refractive index and a nonlinear coefficient in an optical lattice; constructing a nonlinear Schrodinger equation for describing a light beam transmission characteristic based on the optical lattice subjected to the periodic modulation; solving the nonlinear Schrodinger equation by using an equivalent particle method to obtain an optical soliton center position; and based on the optical soliton center position, completing controllable adjustment of the spatial optical soliton motion state through numerical simulation verification. The application periodically modulates the transverse refractive index and the nonlinear coefficient in the optical lattice, derives a new nonlinear Schrodinger equation, solves the nonlinear Schrodinger equation by using the equivalent particle method, analyzes several states of the optical soliton transmission in the optical lattice, and verifies the correctness of the equation through numerical simulation, so that the motion trajectory control problem of the optical soliton transmission in the optical lattice is solved.

The embodiment of the invention discloses an infrared band multi-mode calibration method and device. The method comprises the following steps: calculating a point spread function (PSF) of an original infrared image, and generating a spatial response matching filter function (SRMF) according to the PSF; carrying out two-dimensional convolution calculation on the SRMF to obtain an infrared image after effective space calibration; generating a possible spectral response function of ice pollution, and evaluating an optimal ice pollution spectral response through a cross calibration method; according to the optimal ice pollution spectral response, a spectral response function after possible spectral offset is generated, the optimal possible spectral offset is evaluated through a cross calibration method, and a spectral response function after spectral calibration is obtained through optimal sampling; calculating a linear coefficient, a nonlinear coefficient and a constant coefficient of radiometric calibration; and according to each coefficient of radiometric calibration, calculating the radiation quantity of the infrared image after multi-modal calibration. The method can overcome the existing problems and promote the quantification and multi-source fusion application of the satellite infrared data.

The invention discloses a performance analysis method and device based on a hard isolation passive optical fiber network, terminal equipment and a storage medium, and the method comprises the steps: constructing a simulation model used for representing the propagation of an optical signal in each channel according to a group velocity dispersion parameter, a preset attenuation coefficient and a preset nonlinear coefficient of each channel in the passive optical fiber network; and the simulation model is solved to obtain an approximate analytic solution used for representing the change of the optical signal in each channel along with time and space, so that the bit error rate and the achievable information rate of each channel in the passive optical network are calculated according to the approximate analytic solution, and finally, according to the bit error rate and the achievable information rate, the optical signal in the passive optical network is simulated according to the bit error rate and the achievable information rate. And generating a performance analysis result of the passive optical fiber network. Compared with a laboratory test method adopted in the prior art, the method has the advantage that the aim of performing performance analysis on the passive optical fiber network based on hard isolation efficiently at low cost can be achieved.

The invention relates to a multi-target equivalent static wind load calculation method suitable for a nonlinear structure. The method comprises the following steps: firstly, carrying out a nonlinear structure wind tunnel test and establishing a corresponding finite element model; secondly, obtaining an average component of the equivalent static wind load through a wind tunnel test result, obtaining an equivalent static wind load not including the average component through time-history analysis of a finite element model, namely a pulsation component, and obtaining a multi-target linear equivalent static wind load through combined analysis of the pulsation component and the average component; and finally, on the basis of the multi-target linear equivalent quiet wind load, correcting the multi-target linear equivalent quiet wind load in combination with a nonlinear coefficient, calculating to obtain a multi-target nonlinear equivalent quiet wind load, and expressing the multi-target nonlinear equivalent quiet wind load as a wind pressure coefficient form. The simultaneous equivalence of multiple extreme responses of a nonlinear structure is realized, and a convenient and accurate equivalent static wind load is provided for engineering design.

This invention discloses a system and method for monitoring the hydrogen damage state of metals, comprising: a hydrogen charging device for electrochemically charging a plate-shaped sample of the same metal as the target metal that has not undergone hydrogen damage; a hydrogen permeation measuring device for converting hydrogen atoms permeating into the sample into hydrogen ions during the hydrogen charging process and measuring the current generated by the free electrons produced during the conversion process in real time to obtain a hydrogen permeation curve; and an ultrasonic measuring device for emitting ultrasonic guided waves to the sample during the hydrogen charging process and receiving the nonlinear response signal generated by the guided waves exciting ultrasonic waves inside the sample, and then performing cepstral analysis on the received signal to obtain the nonlinear coefficients at different time periods. Based on this, combined with the hydrogen permeation curve, the correlation between the nonlinear response signal and the degree of hydrogen damage is determined, and then the nonlinear response signal of the target metal is substituted into the correlation to obtain the hydrogen damage state inside the metal. This invention can monitor and evaluate the degree of hydrogen damage inside metals in real time.

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for applying non-linearity to digital subcarriers. A receiver includes a detector circuit operable to receive a first optical signal over an optical link, the first optical signal carrying first data. The receiver includes a carrier recovery estimation circuit operable to generate compensated data by correcting errors in the first data. The receiver includes a non-linear coefficient estimation circuit operable to (i) receive the compensated data, and (ii) estimate one or more non-linear coefficients, wherein information indicative of the estimated non-linear coefficients is transmitted over an optical network, such that a second optical signal is transmitted based, at least in part, on the estimated non-linear coefficients, the second optical signal being received by the receiver.

An optical nonlinearity measurement method according to the present disclosure utilizes photon pair generation through a spontaneous four-wave mixing process, to observe photon pairs using an optical waveguide loaded with a two-dimensional material. Compared with the Z-scan method, the influence of free carriers on nonlinear refractive indexes is only indirect. With a parameter being the length of the attached two-dimensional material in the optical waveguide direction, a theoretical value of the coincidence rate of the photon pairs based on the coupled wave equation is fitted to a measured value of the coincidence rate of the photon pairs. For the coincidence rate of the photon pairs, the theoretical value based on the coupled wave equation is fitted to the measured value in a state reflecting the structure of the optical waveguide loaded with the two-dimensional material, and nonlinear coefficients γ1 and γ2 at that time are obtained.

This invention discloses a numerical inversion method for nonlinear stress fields, comprising: selecting a study area and constructing a three-dimensional geological model; discretizing the boundary surface of the three-dimensional geological model into multiple surface elements, assigning a nonlinear variation coefficient to each surface element to generate the nonlinear variation coefficient of the model boundary surface; determining the stress components with significant influence on the study area based on measured geostress values ​​as linear boundary conditions applied to the model; adjusting the nonlinear coefficients of the linear boundary conditions to obtain nonlinear boundary conditions; determining the calculated stress component values ​​at measured points under preset working conditions based on the nonlinear boundary conditions; determining the regression coefficients for each preset working condition using the principle of linear superposition and the least squares method based on the measured and calculated stress component values; and generating a nonlinear geostress field based on the nonlinear boundary conditions and regression coefficients and a numerical calculation model. This method achieves the loading of nonlinear stress boundaries, thereby determining the optimal nonlinear geostress field.