A measurement method and device based on forward light and backscattering

Abstract

The present invention discloses a measurement method and device based on forward light and backward scattering, the method comprising: performing high-order amplification processing on the received backward scattered light and forward light to obtain interference signals and initial beat frequency signals; demodulating the forward light and adding the interference signal to obtain pseudo continuous light; calculating the phase delay difference between the initial beat frequency signals at the same time to obtain vibration position information; converting the initial beat frequency signal to obtain a conversion signal, obtaining a second conversion signal when propagating through the optical fiber to be measured, and reconverting to obtain reflected light information; analyzing the reflected light information and vibration position information to obtain target strain information. The present invention reduces the maintenance cost of the optical communication system by converting single-frequency continuous light into linear frequency modulated continuous light and integrating multiple interferometers for demodulation positioning and strain sensing, realizes ultra-long distance sensing, and performs multi-point vibration and dynamic and static measurements, thereby improving sensing efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of optical engineering, and in particular to a measurement method and device based on forward light and backscattering. Background Art

[0002] Distributed fiber optic sensors have the advantages of high sensitivity, wide dynamic range, high reliability, spatially resolved information collection capability and resistance to electromagnetic interference. Through some technical means, the optical fibers of these communication cables can sense physical events in addition to normal communication functions. The integration of interaception can quickly establish a global information collection network at low cost and promote the development of the next generation of Internet of Things technology.

[0003] However, most distributed fiber optic sensing systems based on forward light use the interferometer structure of Mach–Zehnder interferometer (MZI), which makes it difficult to achieve multi-point vibration positioning and is easily interfered by other environmental noise on the sensing fiber optic link. It is also very difficult to achieve ultra-low frequency vibration and static measurement. The sensing distance of optical frequency domain reflectometer (OFDR) and phase sensitive optical time domain reflectometer (φ-OTDR) is greatly limited, and requires high cost for maintenance.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] The main purpose of the present invention is to provide a measurement method, system, terminal and computer-readable storage medium based on forward light and backward scattering, aiming to solve the problems in the prior art that ultra-low frequency vibration and static measurement of distributed optical fiber sensing systems based on forward light transmission are very difficult, and distributed optical fiber sensing systems based on backward scattering are difficult to install and maintain, resulting in high cost and low efficiency of optical communication systems.

[0006] To achieve the above object, the present invention provides a measurement method based on forward light and backscattering, and the measurement method based on forward light and backscattering comprises the following steps:

[0007] Receiving backscattered light and forward light, performing high-order amplification processing on the backscattered light and the forward light to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals, wherein the plurality of interference signals include the first interference signal and the second interference signal, and the plurality of initial beat frequency signals include a plurality of initial beat frequency signals of the forward light and an initial beat frequency signal of the backscattered light;

[0008] Demodulating the forward light to obtain phase change information of the forward light, screening out all non-interference interval signals of the forward light according to the phase change information, and replacing all the non-interference interval signals with the first interference signal and the second interference signal to obtain phase change information of pseudo-continuous light;

[0009] Calculating the phase delay difference between the multiple initial beat frequency signals of the forward light according to the phase change information of the pseudo continuous light to obtain the vibration position information;

[0010] Obtaining optical fiber information of the optical fiber to be tested, converting the initial beat frequency signal of the backscattered light to obtain a first conversion signal, applying strain to a preset area of ​​the optical fiber to be tested according to the optical fiber information when the first conversion signal propagates through the optical fiber to be tested to obtain a second conversion signal, and reconverting the first conversion signal and the second conversion signal to obtain reflected light information;

[0011] The reflected light information and the vibration position information are analyzed to obtain target strain information of the optical fiber to be tested.

[0012] Optionally, the measurement method based on forward light and backward scattering, wherein the receiving of backward scattered light and forward light, performing high-order amplification processing on the backward scattered light and the forward light to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals, specifically includes:

[0013] receiving the backscattered light emitted by the first laser and receiving the forward light output by the arbitrary waveform generator;

[0014] Controlling the electro-optical modulator to modulate the backscattered light and the forward light to obtain multi-order sidebands, and inputting the multi-order sidebands into the second laser through the second circulator to output a plurality of continuous frequency-sweeping lights;

[0015] The plurality of continuously swept frequency lights are transmitted to a plurality of sensing optical paths through a first circulator, and a first interference signal, a second interference signal and a plurality of initial beat frequency signals are output.

[0016] Optionally, the measurement method based on forward light and backscattering, wherein the receiving of the backscattered light emitted by the first laser and the receiving of the forward light output by the arbitrary waveform generator, further comprises:

[0017] The backscattered light and the forward light are transmitted to a preset laser resonant cavity for sideband confusion elimination processing, and the processed backscattered light and forward light are output.

[0018] Optionally, in the measurement method based on forward light and backward scattering, the plurality of sensing optical paths include: a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer and an optical frequency reflectometer, and the plurality of continuous frequency-sweeping lights include a first continuous frequency-sweeping light and a second continuous frequency-sweeping light;

[0019] The step of transmitting the plurality of continuous frequency-sweeping lights to the plurality of sensing optical paths through the first circulator and outputting the first interference signal, the second interference signal and the plurality of initial beat frequency signals specifically includes:

[0020] The first continuously swept frequency light is transmitted to the first Mach-Zehnder interferometer through the first circulator, a first reference arm light field and a first signal arm light field are output, and the first reference arm light field and the first signal arm light field are transmitted to the first optical coupler for interference to obtain a first interference signal, and a first initial beat frequency signal of the forward light is obtained according to the first reference arm light field and the first signal arm light field:

[0021] ;

[0022] in, Indicated in The first reference arm light field at time, represents the light field intensity of backscattered light in vacuum, represents the natural exponential function, represents the direction of the electric vector of the light field in the first reference arm, represents the center frequency of the backscattered light, Indicates the time, Indicates the tuning speed of the arbitrary waveform generator;

[0023] ;

[0024] in, Indicated in The first signal arm of the moment, The delay difference is When the light intensity decays, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field, represents the third reference arm light field, Indicates the phase change information of the forward light due to external interference;

[0025] ;

[0026] in, The delay difference is The reflection coefficient of the optical fiber to be tested is It represents the attenuation coefficient of the optical fiber to be tested. is the speed of light in vacuum, is the medium refractive index of the optical fiber to be tested;

[0027] ;

[0028] , ;

[0029] in, Indicated in The first initial beat signal at time, represents the beat frequency of the first reference arm light field and the first signal arm light field;

[0030] The first continuously swept frequency light is transmitted to the second Mach-Zehnder interferometer through the first circulator, a second reference arm light field and a second signal arm light field are output, and the second reference arm light field and the second signal arm light field are transmitted to the second optical coupler for interference to obtain a second interference signal, and a second initial beat frequency signal of the forward light is obtained according to the second reference arm light field and the second signal arm light field:

[0031] ;

[0032] in, Indicated in The light field of the second reference arm at time, represents the direction of the electric vector of the light field of the second reference arm;

[0033] ;

[0034] in, Indicated in The second signal arm at the moment, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field, The delay difference is Light intensity decays;

[0035] ;

[0036] , ;

[0037] in, Indicated in The second initial beat signal at time, represents the beat frequency of the second reference arm light field and the second signal arm light field;

[0038] The second continuously swept frequency light is transmitted to the optical frequency reflectometer through the first circulator, and a third reference arm light field and a third signal arm light field are outputted. According to the third reference arm light field and the third signal arm light field, a third initial beat frequency signal of the backscattered light is obtained:

[0039] ;

[0040] in, Indicated in The third reference arm light field at time , represents the direction of the electric vector of the light field in the third reference arm, Indicated in Phase change information of backscattered light at the moment;

[0041] ;

[0042] in, Indicated in The third signal arm at the moment, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field at The delay difference is The light intensity decays when

[0043] ;

[0044] , ;

[0045] in, Indicated in The third initial beat signal at time, It represents the beat frequency of the third reference arm light field and the third signal arm light field.

[0046] Optionally, the measurement method based on forward light and backward scattering, wherein the demodulating the forward light to obtain phase change information of the forward light, screening out all non-interference interval signals of the forward light according to the phase change information, and using the first interference signal and the second interference signal to replace all the non-interference interval signals to obtain the phase change information of the pseudo-continuous light, specifically includes:

[0047] Transmitting the forward light to the photoelectric balance module, outputting a light intensity signal, and demodulating the light intensity signal using a demodulator to obtain phase change information of the forward light;

[0048] Through a threshold peak-finding algorithm, all non-interference interval signals of the forward light are screened out according to the phase change information, and the first interference signal and the second interference signal are used to replace all the non-interference interval signals to obtain the phase change information of the pseudo-continuous light.

[0049] Optionally, the measurement method based on forward light and backward scattering, wherein the phase delay difference between the multiple initial beat frequency signals of the forward light is calculated according to the phase change information of the pseudo-continuous light to obtain the vibration position information, specifically includes:

[0050] According to a preset demodulation algorithm, the phase change information of the pseudo continuous light is demodulated to obtain an orthogonal component;

[0051] ;

[0052] in, Indicates that pseudo-continuous light is The phase change information caused by external interference at any time, represents the orthogonal components, represents the orthogonal component of the first initial beat signal or the second initial beat signal, express or ;

[0053] The phase delay difference between the first initial beat frequency signal and the second initial beat frequency signal is calculated using a cross-correlation function:

[0054] ;

[0055] , ;

[0056] ;

[0057] in, represents the cross-correlation function, Indicates that pseudo-continuous light is The phase change information caused by external interference at any time, Indicates that pseudo-continuous light is The phase change information caused by external interference at any time, Indicates the phase delay difference;

[0058] The vibration position information of the forward light is obtained according to the phase delay difference and the orthogonal component.

[0059] Optionally, the measurement method based on forward light and backward scattering, wherein the fiber information of the optical fiber to be measured is obtained, the initial beat frequency signal of the backscattered light is converted and processed to obtain a first conversion signal, when the first conversion signal propagates through the optical fiber to be measured, strain is applied to a preset area of ​​the optical fiber to be measured according to the optical fiber information to obtain a second conversion signal, and the first conversion signal and the second conversion signal are re-converted and processed to obtain reflected light information, specifically includes:

[0060] Obtaining optical fiber information of the optical fiber to be tested, constructing a sliding window, and converting the third initial beat frequency signal from the wavelength domain to the distance domain through the sliding window to obtain a first conversion signal;

[0061] When the first conversion signal propagates through the optical fiber to be tested, a preset area of ​​the optical fiber to be tested is determined according to the optical fiber information, and a signal generated by a preset piezoelectric device is input into the preset area to obtain a second conversion signal within the preset area;

[0062] Respectively converting the first conversion signal and the second conversion signal from the distance domain to the wavelength domain through the sliding window to obtain a first target signal and a second target signal within the sliding window;

[0063] The first target signal and the second target signal are cross-correlated in the wavelength domain by using the cross-correlation function to obtain reflected light information corresponding to the third initial beat frequency signal.

[0064] Optionally, the measurement method based on forward light and backward scattering, wherein the analyzing the reflected light information and the vibration position information to obtain the target strain information of the optical fiber to be measured, specifically includes:

[0065] Analyzing the reflected light information corresponding to the backscattered light and the vibration position information corresponding to the forward light to obtain initial strain information of the optical fiber to be tested;

[0066] The target strain information is extracted from the initial strain information through the sliding window.

[0067] In addition, to achieve the above-mentioned purpose, the present invention further provides a measurement device based on forward light and backward scattering, wherein the measurement device based on forward light and backward scattering comprises:

[0068] A linear frequency-sweeping light source, used for receiving backscattered light and forward light, and performing high-order amplification processing on the backscattered light and the forward light;

[0069] A sensing optical path system, used to obtain multiple interference signals and multiple initial beat frequency signals after high-order amplification processing, demodulate the forward light, obtain phase change information of the forward light, screen out all non-interference interval signals of the forward light according to the phase change information, and use the first interference signal and the second interference signal to replace all the non-interference interval signals to obtain phase change information of pseudo-continuous light, calculate the phase delay difference between the multiple initial beat frequency signals of the forward light according to the phase change information of the pseudo-continuous light, and obtain vibration position information;

[0070] An optical frequency reflectometer is used to obtain optical fiber information of the optical fiber to be tested, convert the initial beat frequency signal of the backscattered light to obtain a first conversion signal, apply strain to a preset area of ​​the optical fiber to be tested according to the optical fiber information when the first conversion signal propagates through the optical fiber to be tested, obtain a second conversion signal, and re-convert the first conversion signal and the second conversion signal to obtain reflected light information, analyze the reflected light information and the vibration position information, and obtain target strain information of the optical fiber to be tested, wherein the optical frequency reflectometer is in the sensing optical path system.

[0071] Optionally, in the measurement device based on forward light and backward scattering, the multiple initial beat frequency signals include a first initial beat frequency signal and a second initial beat frequency signal, and the sensing optical path system further includes:

[0072] a first Mach-Zehnder interferometer, used for performing interference processing on the continuously swept-frequency light to obtain the first interference signal and the first initial beat frequency signal;

[0073] The second Mach-Zehnder interferometer is used to perform interference processing on the continuously swept-frequency light to obtain the second interference signal and the second initial beat frequency signal.

[0074] In the present invention, backscattered light and forward light are received, and high-order amplification processing is performed on the backscattered light and the forward light to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals, wherein the plurality of interference signals include a first interference signal and a second interference signal, and the plurality of initial beat frequency signals include a plurality of initial beat frequency signals of the forward light and an initial beat frequency signal of the backscattered light; the forward light is demodulated to obtain phase change information of the forward light, and all non-interference interval signals of the forward light are screened out according to the phase change information, and the first interference signal and the second interference signal are used to replace all the non-interference interval signals to obtain pseudo-continuous light. Phase change information; according to the phase change information of the pseudo-continuous light, calculate the phase delay difference between the multiple initial beat frequency signals of the forward light to obtain vibration position information; obtain the fiber information of the optical fiber to be tested, convert the initial beat frequency signal of the backscattered light to obtain a first conversion signal, when the first conversion signal propagates through the optical fiber to be tested, apply strain to the preset area of ​​the optical fiber to be tested according to the optical fiber information to obtain a second conversion signal, and reconvert the first conversion signal and the second conversion signal to obtain reflected light information; analyze the reflected light information and the vibration position information to obtain the target strain information of the optical fiber to be tested. The present invention reduces the maintenance cost of the optical communication system by converting single-frequency continuous light into linear frequency modulated continuous light and integrating multiple interferometers for demodulation positioning and strain sensing, realizes ultra-long distance sensing, and performs multi-point vibration and dynamic and static measurements, thereby improving sensing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 It is a flow chart of a preferred embodiment of the measurement method based on forward light and backscattering of the present invention;

[0076] Figure 2 It is a demodulation flow chart of a preferred embodiment of the measurement method based on forward light and backscattering of the present invention;

[0077] Figure 3 It is a signal diagram of the light intensity time domain of the non-interference interval and the interference interval of the preferred embodiment of the measurement method based on forward light and backward scattering of the present invention;

[0078] Figure 4 Schematic diagram of pseudo-continuous light of a preferred embodiment of the measurement method based on forward light and backscattering of the present invention;

[0079] Figure 5 It is a schematic diagram of the cross-correlation spectrum of a preferred embodiment of the measurement method based on forward light and backscattering of the present invention;

[0080] Figure 6 is a signal processing flow chart of the measurement method based on forward light and backscattering of the present invention;

[0081] Figure 7 It is a structural schematic diagram of the measurement method based on forward light and backscattering of the present invention. DETAILED DESCRIPTION

[0082] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0083] The measurement method based on forward light and backscattering described in the preferred embodiment of the present invention is as follows: Figure 1 As shown, the measurement method based on forward light and backscattering includes the following steps:

[0084] Step S10, receiving backscattered light and forward light, performing high-order amplification processing on the backscattered light and the forward light, and obtaining a first interference signal, a second interference signal and a plurality of initial beat frequency signals, wherein the plurality of interference signals include the first interference signal and the second interference signal, and the plurality of initial beat frequency signals include a plurality of initial beat frequency signals of the forward light and an initial beat frequency signal of the backscattered light.

[0085] Among them, high-order sideband modulation technology is used (the principle of high-order modulation refers to the use of signal amplitude and phase to carry information to achieve higher transmission efficiency and reliability) to increase the frequency sweep range of the received backscattered light and forward light. At the same time, optical injection locking technology is used (the performance of the laser is improved by injecting light into a laser resonant cavity working at a specific frequency, and the injected light frequency is equal to the laser frequency) to eliminate sideband aliasing. For example, light with a frequency sweep range of 15 GHz (15 gigahertz) is amplified to 60 GHz through the fourth order, which can significantly improve the spatial resolution in the OFDR (Optical Frequency Domain Reflectometry) system.

[0086] Specifically, the backscattered light emitted by the first laser is received, and the forward light output by the arbitrary waveform generator is received; the electro-optical modulator is controlled to modulate the backscattered light and the forward light to obtain multi-order sidebands, and the multi-order sidebands are input to the second laser through the second circulator to output a plurality of continuous frequency-sweeping lights; the plurality of continuous frequency-sweeping lights are transmitted to a plurality of sensing optical paths through the first circulator to output a first interference signal, a second interference signal and a plurality of initial beat frequency signals.

[0087] Among them, Laser1 (the first laser) produces a center frequency of The ultra-narrow linewidth backscattered light and the forward light output by the arbitrary waveform generator can generate multi-order sidebands after being modulated by the EOM (Electro-Optic Modulator) and injected into Laser2 (the second laser) through the circulator. The driving signal of the EOM comes from the chirped swept frequency signal (a frequency modulated signal whose frequency changes linearly with time) output by the AWG (Arbitrary Waveform Generator) after being amplified by the Amplifier (voltage amplifier). Laser2 (the second laser) is a tunable laser. By adjusting the voltage of Laser2, the center frequency of the output light of Laser2 is adjusted to the i-th order sideband of Laser1, and a swept frequency range of The continuous frequency sweep light achieves a wider frequency response and a longer sensing range.

[0088] The plurality of sensing optical paths include: a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer and an optical frequency reflectometer, and the plurality of continuous frequency-sweeping lights include a first continuous frequency-sweeping light and a second continuous frequency-sweeping light. The first continuous frequency-sweeping light is transmitted to the first Mach-Zehnder interferometer through a first circulator, a first reference arm light field and a first signal arm light field are output, and the first reference arm light field and the first signal arm light field are transmitted to a first optical coupler for interference to obtain a first interference signal, and a first initial beat frequency signal of the forward light is obtained according to the first reference arm light field and the first signal arm light field:

[0089] ;

[0090] in, Indicated in The first reference arm light field at time, represents the light field intensity of backscattered light in vacuum, represents the natural exponential function, represents the direction of the electric vector of the light field in the first reference arm, represents the center frequency of the backscattered light, Indicates the time, Indicates the tuning speed of the arbitrary waveform generator;

[0091] ;

[0092] in, Indicated in The first signal arm of the moment, The delay difference is When the light intensity decays, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field, represents the third reference arm light field, Indicates the phase change information of the forward light due to external interference;

[0093] ;

[0094] in, The delay difference is The reflection coefficient of the optical fiber to be tested is It represents the attenuation coefficient of the optical fiber to be tested. is the speed of light in vacuum, is the medium refractive index of the optical fiber to be tested;

[0095] ;

[0096] , ;

[0097] in, Indicated in The first initial beat signal at time, represents the beat frequency of the first reference arm light field and the first signal arm light field; where, due to , it can be seen that different positions of the optical fiber to be tested correspond to different beat frequencies, and there is a proportional linear relationship between them; the first continuous frequency sweep light is transmitted to the second Mach-Zehnder interferometer through the first circulator, the second reference arm light field and the second signal arm light field are output, and are transmitted to the second optical coupler for interference to obtain a second interference signal, and the second initial beat frequency signal of the forward light is obtained according to the second reference arm light field and the second signal arm light field:

[0098] ;

[0099] in, Indicated in The light field of the second reference arm at time, represents the direction of the electric vector of the light field of the second reference arm;

[0100] ;

[0101] in, Indicated in The second signal arm at the moment, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field, The delay difference is Light intensity decays;

[0102] ;

[0103] , ;

[0104] in, Indicated in The second initial beat signal at time, Represents the beat frequency of the second reference arm light field and the second signal arm light field; transmits the second continuously swept frequency light to the optical frequency reflectometer through the first circulator, outputs the third reference arm light field and the third signal arm light field, and obtains the third initial beat frequency signal of the backscattered light according to the third reference arm light field and the third signal arm light field:

[0105] ;

[0106] in, Indicated in The third reference arm light field at time , represents the direction of the electric vector of the light field in the third reference arm, Indicated in Phase change information of backscattered light at the moment;

[0107] ;

[0108] in, Indicated in The third signal arm at the moment, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field at The delay difference is The light intensity decays when

[0109] ;

[0110] , ;

[0111] in, Indicated in The third initial beat signal at time, It represents the beat frequency of the third reference arm light field and the third signal arm light field.

[0112] The continuously swept light after high-order lock-in amplification enters the sensing optical path through the circulator. The sensing optical path can be divided into three parts, namely OFDR, MZI1 (MZI stands for Mach-Zehnder interferometer, and the number represents its number) and MZI2. The signal arm of MZI1 is the first signal arm, and the reference arm is the first reference arm. The light in the first signal arm and the first reference arm interferes in OC1 (OC stands for Optical Coupler, and the number represents its number), and the interference signal is received by BPD3 (BPD stands for Balanced Photodetector Module, and the number represents its number). The signal arm of MZI2 is the second signal arm, and the reference arm is the reference arm second reference arm. The light in the second signal arm and the second reference arm interferes in OC2, and the interference signal is received by BPD1. The signal arm of OFDR is the third signal arm, and the reference arm is the third reference arm, and interference occurs in OC3. Finally, the polarization diversity method (i.e., the received optical signal is split into orthogonal polarization directions, and the photoelectric conversion is performed separately and then algebraically added) is used to eliminate the influence of OFDR polarization fading, effectively reducing the interference of other environmental noise on the sensor fiber link.

[0113] Furthermore, the backscattered light and the forward light are transmitted to a preset laser resonant cavity for sideband confusion elimination processing, and the processed backscattered light and forward light are output, thereby reducing measurement errors and improving measurement accuracy.

[0114] Step S20, demodulate the forward light to obtain phase change information of the forward light, filter out all non-interference interval signals of the forward light according to the phase change information, and use the first interference signal and the second interference signal to replace all the non-interference interval signals to obtain phase change information of pseudo-continuous light.

[0115] Among them, the process of demodulating the forward light is as follows Figure 2 As shown in the figure, since the sweep signal output by the AWG starts the second sweep cycle immediately after the end of one sweep cycle, the sweep light output at the end of the previous sweep cycle will beat the sweep light at the beginning of the next sweep cycle. At this time, the beat frequency of the sweep light is not or , but mutated into a much larger or frequency. Since the BPD used has bandwidth limitations and is much smaller than the beat frequency at the end of the sweep cycle, the MZI receiver cannot receive this signal at this time. Here, the optical signal in the end area of ​​the sweep cycle is called the non-interference interval signal. The phase information generated by external interference cannot be extracted in the non-interference interval. Therefore, the non-interference interval signal needs to be replaced with the adjacent interference interval signal. Before performing the signal replacement operation, the starting and ending positions of the non-interference signal interval need to be found; since the light intensity of the interference signal is greater than the light intensity of the non-interference signal, a suitable threshold can be set as the minimum peak height of the peak-finding algorithm to find the starting and ending positions of the non-interference interval.

[0116] However, a single MZI structure cannot obtain distributed vibration position information, so two MZI structures are needed to form a double Mach-Zehnder interferometer (DMZI) to obtain a double-end signal and calculate the time delay to obtain the vibration position information. Because the light intensity signal obtained by BPD and the vibration signal are in a nonlinear relationship, it is necessary to demodulate the light intensity signal to obtain the phase to calculate the phase time delay at both ends to obtain the vibration position information. The Hilbert transform can construct an analytical signal of a signal to obtain the orthogonal component of the signal, and through I / Q (In-phase / Quadrature, where "I" represents the in-phase component, "Q" represents the orthogonal component, and " / " represents or) demodulation to obtain the instantaneous phase of the signal.

[0117] Specifically, the forward light is transmitted to the photoelectric balancing module, a light intensity signal is output, and the light intensity signal is demodulated by a demodulator to obtain phase change information of the forward light; through a threshold peak-finding algorithm, all non-interference interval signals of the forward light are screened out according to the phase change information, and the first interference signal and the second interference signal are used to replace all the non-interference interval signals to obtain phase change information of pseudo-continuous light.

[0118] Let the length of the non-interference interval be , the interference interval is located at both ends of the non-interference interval, set as well as , the starting time of the non-interference interval found by the threshold peak-finding algorithm is , the end time is , the light intensity signal in the non-interference interval is ,like Figure 3 and Figure 4 As shown. Zhongcong The numerical value is replaced by middle The value of Zhongcong The numerical value is replaced by middle The value of pseudo-continuous light It can be expressed as:

[0119] .

[0120] By combining forward optical sensing with OFDR, a threshold peak-finding algorithm is used to obtain the starting and ending points of the non-interference area and replace the non-interference interval signal with the adjacent interference interval signal to generate a pseudo-continuous optical signal for demodulation. This achieves ultra-long-distance sensing while realizing multi-point vibration and static measurement at the near end. It can also reduce the resources, power and maintenance required to support the detection system, and can be integrated with existing optical communication systems to reduce costs and maintenance.

[0121] Step S30: Calculate the phase delay difference between the multiple initial beat frequency signals of the forward light according to the phase change information of the pseudo-continuous light to obtain the vibration position information.

[0122] The key step in locating vibration in the DMZI structure is to calculate the time delay between the two interference signals modulated by the interference, because the positioning algorithm is highly dependent on the time delay. and There is a nonlinear relationship between the external vibration signal and the phase change caused by the external vibration in the light field. There is a linear relationship between them, so the positioning algorithm based on the DMZI structure usually needs to demodulate the light intensity signal to obtain , and then use the cross-correlation algorithm to calculate the phase delay difference between the two MZI receiving ends to obtain the position where the vibration occurs. Specifically, according to a preset demodulation algorithm, the phase change information of the pseudo-continuous light is demodulated to obtain the orthogonal component;

[0123] ;

[0124] in, Indicates that pseudo-continuous light is The phase change information caused by external interference at any time, represents the orthogonal components, represents the orthogonal component of the first initial beat signal or the second initial beat signal, express or ; Using the cross-correlation function, the phase delay difference between the first initial beat frequency signal and the second initial beat frequency signal is calculated:

[0125] ;

[0126] , ;

[0127] ;

[0128] in, represents the cross-correlation function, Indicates that pseudo-continuous light is The phase change information caused by external interference at any time, Indicates that pseudo-continuous light is The phase change information caused by external interference at any time, represents a phase delay difference; and according to the phase delay difference and the orthogonal component, the vibration position information of the forward light is obtained.

[0129] In order to simplify the expression, the influence of light intensity attenuation and DC component is ignored, so the formula of the light intensity signal at the MZI receiving end is simplified to obtain:

[0130] ;

[0131] in, and Represent two moments respectively, and the calculation formula is:

[0132] , .

[0133] like Figure 5 As shown in Figure 2, according to the expression of the cross-correlation function, we can know that There is an obvious maximum value at The peak position of the relationship curve can determine the phase delay difference.

[0134] Step S40, obtaining the optical fiber information of the optical fiber to be tested, converting the initial beat frequency signal of the backscattered light to obtain a first conversion signal, applying strain to a preset area of ​​the optical fiber to be tested according to the optical fiber information when the first conversion signal propagates through the optical fiber to be tested to obtain a second conversion signal, and reconverting the first conversion signal and the second conversion signal to obtain reflected light information.

[0135] Specifically, the optical fiber information of the optical fiber to be tested is obtained, a sliding window is constructed, and the third initial beat frequency signal is converted from the wavelength domain to the distance domain through the sliding window to obtain a first conversion signal; when the first conversion signal propagates through the optical fiber to be tested, a preset area of ​​the optical fiber to be tested is determined according to the optical fiber information, and a signal generated by a preset piezoelectric device is input into the preset area to obtain a second conversion signal within the preset area; the first conversion signal and the second conversion signal are respectively converted from the distance domain to the wavelength domain through the sliding window to obtain a first target signal and a second target signal within the sliding window; and the first target signal and the second target signal are cross-correlated in the wavelength domain using the cross-correlation function to obtain reflected light information corresponding to the third initial beat frequency signal.

[0136] The initial beat frequency signal is processed by Fourier transform to convert the wavelength domain of the optical frequency domain signal into the distance domain; Figure 6 As shown, the OFDR system is used to collect two sets of Rayleigh scattering signals, one set is used as the reference signal (first conversion signal), at this time the optical fiber to be tested is not affected by the strain, and the other set is used as the measurement signal (second conversion signal), at this time a strain is applied to a certain area on the optical fiber to be tested; then, the reference signal and the measurement signal are converted from the time domain to the distance domain (frequency domain) by Fourier transform, and then a sliding window is used to select Rayleigh scattering signals at different positions (when the particle size is much smaller than the wavelength of the incident light (less than one tenth of the wavelength), the intensity of the scattered light in each direction is different, and the intensity is inversely proportional to the fourth power of the wavelength of the incident light. This phenomenon is called Rayleigh scattering); wherein the window size can be determined according to the spatial resolution of the OFDR system ( ) is used to determine, and the application of Hilbert transform and in-phase / quadrature (I / Q) demodulation technology to extract the optical phase can effectively analyze the distance-resolved vibration signal as well as the vibration amplitude and frequency, thereby ensuring the accuracy of the test data.

[0137] Step S50: Analyze the reflected light information and the vibration position information to obtain target strain information of the optical fiber to be tested.

[0138] Specifically, the reflected light information corresponding to the backscattered light and the vibration position information corresponding to the forward light are analyzed to obtain initial strain information of the optical fiber to be tested; and target strain information is extracted from the initial strain information through the sliding window.

[0139] Among them, the Rayleigh scattered signal in the sliding window is converted to the wavelength domain through inverse Fourier transform, and the reference signal and the measured signal are cross-correlated in the wavelength domain. At this time, the wavelength drift of the correlation peak reflects the strain information of the optical fiber to be measured at the sliding window. By changing the position of the sliding window and repeating the inverse Fourier transform and cross-correlation steps, distributed strain measurement can be achieved. Combined with the use of OFDR technology, the ultra-long distributed optical fiber sensing technology based on forward light sensing can take into account both dynamic and static measurements.

[0140] The present invention reduces the maintenance cost of the optical communication system by converting single-frequency continuous light into linear frequency modulated continuous light and integrating multiple interferometers for demodulation positioning and strain sensing, realizes ultra-long-distance sensing, and performs multi-point vibration and dynamic and static measurements, thereby improving the sensing efficiency.

[0141] Furthermore, if Figure 7 As shown, based on the above-mentioned measurement method based on forward light and backward scattering, the present invention also provides a measurement device based on forward light and backward scattering, wherein the measurement device based on forward light and backward scattering includes:

[0142] A linear frequency-sweeping light source, used for receiving backscattered light and forward light, and performing high-order amplification processing on the backscattered light and the forward light;

[0143] A sensing optical path system, used to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals after high-order amplification processing, demodulate the forward light, obtain phase change information of the forward light, screen out all non-interference interval signals of the forward light according to the phase change information, and use the first interference signal and the second interference signal to replace all the non-interference interval signals to obtain phase change information of pseudo-continuous light, calculate the phase delay difference between the plurality of initial beat frequency signals of the forward light according to the phase change information of the pseudo-continuous light, and obtain vibration position information;

[0144] An optical frequency reflectometer is used to obtain optical fiber information of the optical fiber to be tested, convert the initial beat frequency signal of the backscattered light to obtain a first conversion signal, apply strain to a preset area of ​​the optical fiber to be tested according to the optical fiber information when the first conversion signal propagates through the optical fiber to be tested, obtain a second conversion signal, and re-convert the first conversion signal and the second conversion signal to obtain reflected light information, analyze the reflected light information and the vibration position information, and obtain target strain information of the optical fiber to be tested, wherein the optical frequency reflectometer is in the sensing optical path system.

[0145] Among them, the first signal arm is 3-4-5, the first reference arm is 6-5, the second signal arm is 6-7-8, the second reference arm is 2-8, the third signal arm is 4-5-4-3-9, and the third reference arm is 2-9; among them, 1 represents the line from OC6 to Cir4 (Cir represents Circulator, and the number represents the number), 2 represents the line from OC6 to OC4, 3 represents Cir1, 4 represents the line from FUT (Fiber Under Test) to PZT (Piezoelectric Zirconate Titanate), 5 represents OC1, 6 represents OC5, 7 represents the line from PZT to FUT, 8 represents OC2, and 9 represents OC3.

[0146] Among them, the multiple interference signals include a first interference signal and a second interference signal, the multiple initial beat frequency signals include a first initial beat frequency signal and a second initial beat frequency signal, and the sensing optical path system also includes: a first Mach-Zehnder interferometer, used to perform interference processing on the continuous swept frequency light to obtain the first interference signal and the first initial beat frequency signal; a second Mach-Zehnder interferometer, used to perform interference processing on the continuous swept frequency light to obtain the second interference signal and the second initial beat frequency signal.

[0147] Among them, the PZT is located at Z in the FUT and is wound with two optical fibers of the same length, which can ensure that the PZT is located at the same position in different paths.

[0148] In addition, the detection frequency range and detection distance of the distributed vibration optical fiber sensor of the present invention can be changed; the optical fiber type can be changed, and can be replaced by special optical fibers that are sensitive to vibration, or other types of optical fibers, such as: multi-core optical fibers, polarization-maintaining optical fibers, etc.; the generation method of linear frequency sweep light can be changed, for example: using internal adjustment of an external cavity laser to generate frequency sweep light, etc. In addition, different demodulation methods can also be applied, such as 3×3 coupler demodulation, etc.

[0149] In summary, the present invention provides a measurement method based on forward light and backward scattering and related equipment, the method comprising: receiving backward scattered light and forward light, performing high-order amplification processing on the backward scattered light and the forward light to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals, wherein the plurality of interference signals include a first interference signal and a second interference signal, and the plurality of initial beat frequency signals include a plurality of initial beat frequency signals of the forward light and an initial beat frequency signal of the backward scattered light; demodulating the forward light to obtain phase change information of the forward light, screening out all non-interference interval signals of the forward light according to the phase change information, and using the first interference signal and the second interference signal to replace all The non-interference interval signal is used to obtain the phase change information of the pseudo-continuous light; according to the phase change information of the pseudo-continuous light, the phase delay difference between the multiple initial beat frequency signals of the forward light is calculated to obtain the vibration position information; the optical fiber information of the optical fiber to be tested is obtained, and the initial beat frequency signal of the backscattered light is converted and processed to obtain a first conversion signal. When the first conversion signal propagates through the optical fiber to be tested, strain is applied to the preset area of ​​the optical fiber to be tested according to the optical fiber information to obtain a second conversion signal, and the first conversion signal and the second conversion signal are re-converted to obtain reflected light information; the reflected light information and the vibration position information are analyzed to obtain the target strain information of the optical fiber to be tested. The present invention reduces the maintenance cost of the optical communication system by converting single-frequency continuous light into linear frequency modulated continuous light and integrating multiple interferometers for demodulation positioning and strain sensing, realizes ultra-long distance sensing, and performs multi-point vibration and dynamic and static measurements, thereby improving the sensing efficiency.

[0150] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0151] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A measurement method based on forward light and backscattering, It is characterized in that The measurement method based on forward light and backscattering includes: Receiving backscattered light and forward light, performing high-order amplification processing on the backscattered light and the forward light to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals, wherein the plurality of initial beat frequency signals include a plurality of initial beat frequency signals of the forward light and an initial beat frequency signal of the backscattered light; The receiving of the backscattered light and the forward light, and performing high-order amplification processing on the backscattered light and the forward light to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals specifically includes: receiving the backscattered light emitted by the first laser and receiving the forward light output by the arbitrary waveform generator; Controlling the electro-optical modulator to modulate the backscattered light and the forward light to obtain multi-order sidebands, and inputting the multi-order sidebands into the second laser through the second circulator to output a plurality of continuous frequency-sweeping lights; Transmitting the plurality of continuous frequency-sweeping lights to a plurality of sensing optical paths through a first circulator, and outputting a first interference signal, a second interference signal and a plurality of initial beat frequency signals; Wherein, the plurality of sensing optical paths include: a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer and an optical frequency reflectometer, and the plurality of continuous frequency-sweeping lights include a first continuous frequency-sweeping light and a second continuous frequency-sweeping light; The step of transmitting the plurality of continuous frequency-sweeping lights to the plurality of sensing optical paths through the first circulator and outputting the first interference signal, the second interference signal and the plurality of initial beat frequency signals specifically includes: The first continuously swept frequency light is transmitted to the first Mach-Zehnder interferometer through the first circulator, a first reference arm light field and a first signal arm light field are output, and the first reference arm light field and the first signal arm light field are transmitted to the first optical coupler for interference to obtain a first interference signal, and a first initial beat frequency signal of the forward light is obtained according to the first reference arm light field and the first signal arm light field: ； in, Indicated in The first reference arm light field at time, represents the light field intensity of backscattered light in vacuum, represents the natural exponential function, represents the direction of the electric vector of the light field in the first reference arm, represents the center frequency of the backscattered light, Indicates the time, Indicates the tuning speed of the arbitrary waveform generator; ； in, Indicated in The first signal arm of the moment, The delay difference is When the light intensity decays, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field, represents the third reference arm light field, Indicates the phase change information of the forward light due to external interference; ； in, The delay difference is The reflection coefficient of the optical fiber to be tested is It represents the attenuation coefficient of the optical fiber to be tested. is the speed of light in vacuum, is the medium refractive index of the optical fiber to be tested; ； ， ； in, Indicated in The first initial beat signal at time, represents the beat frequency of the first reference arm light field and the first signal arm light field; The first continuously swept frequency light is transmitted to the second Mach-Zehnder interferometer through the first circulator, a second reference arm light field and a second signal arm light field are output, and the second reference arm light field and the second signal arm light field are transmitted to the second optical coupler for interference to obtain a second interference signal, and a second initial beat frequency signal of the forward light is obtained according to the second reference arm light field and the second signal arm light field: ； in, Indicated in The light field of the second reference arm at time , represents the direction of the electric vector of the light field of the second reference arm; ； in, Indicated in The second signal arm at the moment, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field, The delay difference is Light intensity decays; ； ， ； in, Indicated in The second initial beat signal at time, represents the beat frequency of the second reference arm light field and the second signal arm light field; The second continuously swept frequency light is transmitted to the optical frequency reflectometer through the first circulator, and a third reference arm light field and a third signal arm light field are outputted. According to the third reference arm light field and the third signal arm light field, a third initial beat frequency signal of the backscattered light is obtained: ； in, Indicated in The third reference arm light field at time , represents the direction of the electric vector of the light field in the third reference arm, Indicated in Phase change information of backscattered light at the moment; ； in, Indicated in The third signal arm at the moment, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field at The delay difference is The light intensity decays when ； ， ； in, Indicated in The third initial beat signal at time, represents the beat frequency of the third reference arm light field and the third signal arm light field; Demodulating the forward light to obtain phase change information of the forward light, screening out all non-interference interval signals of the forward light according to the phase change information, and replacing all the non-interference interval signals with the first interference signal and the second interference signal to obtain phase change information of pseudo-continuous light; Calculating the phase delay difference between the multiple initial beat frequency signals of the forward light according to the phase change information of the pseudo continuous light to obtain the vibration position information; Obtaining optical fiber information of the optical fiber to be tested, converting the initial beat frequency signal of the backscattered light to obtain a first conversion signal, applying strain to a preset area of ​​the optical fiber to be tested according to the optical fiber information when the first conversion signal propagates through the optical fiber to be tested to obtain a second conversion signal, and reconverting the first conversion signal and the second conversion signal to obtain reflected light information; The step of acquiring optical fiber information of the optical fiber to be tested, converting the initial beat frequency signal of the backscattered light to obtain a first conversion signal, applying strain to a preset area of ​​the optical fiber to be tested according to the optical fiber information when the first conversion signal propagates through the optical fiber to be tested to obtain a second conversion signal, and reconverting the first conversion signal and the second conversion signal to obtain reflected light information specifically includes: Obtaining optical fiber information of the optical fiber to be tested, constructing a sliding window, and converting the third initial beat frequency signal from the wavelength domain to the distance domain through the sliding window to obtain a first conversion signal; When the first conversion signal propagates through the optical fiber to be tested, a preset area of ​​the optical fiber to be tested is determined according to the optical fiber information, and a signal generated by a preset piezoelectric device is input into the preset area to obtain a second conversion signal within the preset area; Respectively converting the first conversion signal and the second conversion signal from the distance domain to the wavelength domain through the sliding window to obtain a first target signal and a second target signal within the sliding window; Using a cross-correlation function, cross-correlate the first target signal and the second target signal in the wavelength domain to obtain reflected light information corresponding to the third initial beat frequency signal; The reflected light information and the vibration position information are analyzed to obtain target strain information of the optical fiber to be tested.

2. The measurement method based on forward light and backscattering according to claim 1, It is characterized in that The method further comprises: receiving the backscattered light emitted by the first laser and receiving the forward light output by the arbitrary waveform generator; and then: The backscattered light and the forward light are transmitted to a preset laser resonant cavity for sideband confusion elimination processing, and the processed backscattered light and forward light are output.

3. The measurement method based on forward light and backscattering according to claim 1, It is characterized in that The demodulating the forward light to obtain phase change information of the forward light, screening out all non-interference interval signals of the forward light according to the phase change information, and replacing all the non-interference interval signals with the first interference signal and the second interference signal to obtain phase change information of pseudo-continuous light, specifically includes: Transmitting the forward light to the photoelectric balance module, outputting a light intensity signal, and demodulating the light intensity signal using a demodulator to obtain phase change information of the forward light; Through a threshold peak-finding algorithm, all non-interference interval signals of the forward light are screened out according to the phase change information, and the first interference signal and the second interference signal are used to replace all the non-interference interval signals to obtain the phase change information of the pseudo-continuous light.

4. The measurement method based on forward light and backscattering according to claim 1, It is characterized in that The step of calculating the phase delay difference between the multiple initial beat frequency signals of the forward light according to the phase change information of the pseudo-continuous light to obtain the vibration position information specifically includes: According to a preset demodulation algorithm, the phase change information of the pseudo continuous light is demodulated to obtain an orthogonal component; ； in, Indicates that pseudo-continuous light is The phase change information caused by external interference at any time, represents the orthogonal components, represents the orthogonal component of the first initial beat signal or the second initial beat signal, express or ; The phase delay difference between the first initial beat frequency signal and the second initial beat frequency signal is calculated using a cross-correlation function: ； ， ； ； in, represents the cross-correlation function, Indicates that pseudo-continuous light The phase change information caused by external interference at any time, Indicates that pseudo-continuous light The phase change information caused by external interference at any time, Indicates the phase delay difference; The vibration position information of the forward light is obtained according to the phase delay difference and the orthogonal component.

5. The measurement method based on forward light and backscattering according to claim 1, It is characterized in that The analyzing the reflected light information and the vibration position information to obtain the target strain information of the optical fiber to be tested specifically includes: Analyzing the reflected light information corresponding to the backscattered light and the vibration position information corresponding to the forward light to obtain initial strain information of the optical fiber to be tested; The target strain information is extracted from the initial strain information through the sliding window.

6. A measurement device based on forward light and backscattering, It is characterized in that The measurement device based on forward light and backscattering comprises: A linear frequency-sweeping light source, used for receiving backscattered light and forward light, and performing high-order amplification processing on the backscattered light and the forward light; The receiving of the backscattered light and the forward light, and performing high-order amplification processing on the backscattered light and the forward light to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals specifically includes: receiving the backscattered light emitted by the first laser and receiving the forward light output by the arbitrary waveform generator; Controlling the electro-optical modulator to modulate the backscattered light and the forward light to obtain multi-order sidebands, and inputting the multi-order sidebands into the second laser through the second circulator to output a plurality of continuous frequency-sweeping lights; Transmitting the plurality of continuous frequency-sweeping lights to a plurality of sensing optical paths through a first circulator, and outputting a first interference signal, a second interference signal and a plurality of initial beat frequency signals; Wherein, the plurality of sensing optical paths include: a first Mach-Zehnder interferometer, a second Mach-Zehnder interferometer and an optical frequency reflectometer, and the plurality of continuous frequency-sweeping lights include a first continuous frequency-sweeping light and a second continuous frequency-sweeping light; The step of transmitting the plurality of continuous frequency-sweeping lights to the plurality of sensing optical paths through the first circulator and outputting the first interference signal, the second interference signal and the plurality of initial beat frequency signals specifically includes: The first continuously swept frequency light is transmitted to the first Mach-Zehnder interferometer through the first circulator, a first reference arm light field and a first signal arm light field are output, and the first reference arm light field and the first signal arm light field are transmitted to the first optical coupler for interference to obtain a first interference signal, and a first initial beat frequency signal of the forward light is obtained according to the first reference arm light field and the first signal arm light field: ； in, Indicated in The first reference arm light field at time, represents the light field intensity of backscattered light in vacuum, represents the natural exponential function, represents the direction of the electric vector of the light field in the first reference arm, represents the center frequency of the backscattered light, Indicates the time, Indicates the tuning speed of the arbitrary waveform generator; ； in, Indicated in The first signal arm of the moment, The delay difference is When the light intensity decays, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field, represents the third reference arm light field, Indicates the phase change information of the forward light due to external interference; ； in, The delay difference is The reflection coefficient of the optical fiber to be tested is It represents the attenuation coefficient of the optical fiber to be tested. is the speed of light in vacuum, is the medium refractive index of the optical fiber to be tested; ； ， ； in, Indicated in The first initial beat signal at time, represents the beat frequency of the first reference arm light field and the first signal arm light field; The first continuously swept frequency light is transmitted to the second Mach-Zehnder interferometer through the first circulator, a second reference arm light field and a second signal arm light field are output, and the second reference arm light field and the second signal arm light field are transmitted to the second optical coupler for interference to obtain a second interference signal, and a second initial beat frequency signal of the forward light is obtained according to the second reference arm light field and the second signal arm light field: ； in, Indicated in The light field of the second reference arm at time , represents the direction of the electric vector of the light field of the second reference arm; ； in, Indicated in The second signal arm at the moment, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field, The delay difference is Light intensity decays; ； ， ； in, Indicated in The second initial beat signal at time, represents the beat frequency of the second reference arm light field and the second signal arm light field; The second continuously swept frequency light is transmitted to the optical frequency reflectometer through the first circulator, and a third reference arm light field and a third signal arm light field are outputted. According to the third reference arm light field and the third signal arm light field, a third initial beat frequency signal of the backscattered light is obtained: ； in, Indicated in The third reference arm light field at time , represents the direction of the electric vector of the light field in the third reference arm, Indicated in Phase change information of backscattered light at the moment; ； in, Indicated in The third signal arm at the moment, Indicates that the fiber under test The time delay difference between the current reference arm light field and the current signal arm light field at The delay difference is The light intensity decays when ； ， ； in, Indicated in The third initial beat signal at time, represents the beat frequency of the third reference arm light field and the third signal arm light field; A sensing optical path system, used to obtain a first interference signal, a second interference signal and a plurality of initial beat frequency signals after high-order amplification processing, demodulate the forward light, obtain phase change information of the forward light, screen out all non-interference interval signals of the forward light according to the phase change information, and use the first interference signal and the second interference signal to replace all the non-interference interval signals to obtain phase change information of pseudo-continuous light, calculate the phase delay difference between the plurality of initial beat frequency signals of the forward light according to the phase change information of the pseudo-continuous light, and obtain vibration position information; An optical frequency reflectometer, used to obtain optical fiber information of the optical fiber to be tested, convert the initial beat frequency signal of the backscattered light to obtain a first conversion signal, apply strain to a preset area of ​​the optical fiber to be tested according to the optical fiber information when the first conversion signal propagates through the optical fiber to be tested, obtain a second conversion signal, and reconvert the first conversion signal and the second conversion signal to obtain reflected light information, analyze the reflected light information and the vibration position information, and obtain target strain information of the optical fiber to be tested, wherein the optical frequency reflectometer is in the sensing optical path system; The step of acquiring optical fiber information of the optical fiber to be tested, converting the initial beat frequency signal of the backscattered light to obtain a first conversion signal, applying strain to a preset area of ​​the optical fiber to be tested according to the optical fiber information when the first conversion signal propagates through the optical fiber to be tested to obtain a second conversion signal, and reconverting the first conversion signal and the second conversion signal to obtain reflected light information specifically includes: Obtaining optical fiber information of the optical fiber to be tested, constructing a sliding window, and converting the third initial beat frequency signal from the wavelength domain to the distance domain through the sliding window to obtain a first conversion signal; When the first conversion signal propagates through the optical fiber to be tested, a preset area of ​​the optical fiber to be tested is determined according to the optical fiber information, and a signal generated by a preset piezoelectric device is input into the preset area to obtain a second conversion signal within the preset area; Respectively converting the first conversion signal and the second conversion signal from the distance domain to the wavelength domain through the sliding window to obtain a first target signal and a second target signal within the sliding window; The first target signal and the second target signal are cross-correlated in the wavelength domain by using a cross-correlation function to obtain reflected light information corresponding to the third initial beat frequency signal.

7. The measurement device based on forward light and backscattering according to claim 6, It is characterized in that The multiple initial beat frequency signals include a first initial beat frequency signal and a second initial beat frequency signal, and the sensing optical path system further includes: a first Mach-Zehnder interferometer, used for performing interference processing on the continuously swept-frequency light to obtain the first interference signal and the first initial beat frequency signal; The second Mach-Zehnder interferometer is used to perform interference processing on the continuously swept-frequency light to obtain the second interference signal and the second initial beat frequency signal.

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