Frequency modulation nonlinear correction method based on frequency domain phase shift asynchronous resampling

Abstract

The invention provides a frequency modulation nonlinear correction method based on frequency domain phase shift asynchronous resampling. The method is realized based on a sweep frequency interference measurement device, and the method utilizes signals detected by two balance detectors to carry out a series of calculations so as to determine a target distance. According to the method, the problem that in an existing synchronous resampling frequency modulation nonlinear correction method, the nonlinear correction effect is not ideal due to the fact that the optical frequency of the auxiliary interferometer and the optical frequency of the measurement interferometer are not synchronous can be solved, correction can be more accurate through frequency domain phase shift resampling, and the correction effect is not limited by the sampling rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of frequency-modulated continuous wave-based sweep interferometry, in particular to a frequency-modulated nonlinear correction method based on frequency-domain phase shift asynchronous resampling. BACKGROUND

[0002] Frequency-modulated continuous wave-based sweep interferometry is an absolute distance measurement method, which uses the constant optical frequency difference between the measurement light and the reference light in the interferometer to detect the absolute distance of the target. Influenced by the nonlinear modulation of the optical frequency of the sweep light source, the nonlinear change of the optical frequency difference with time leads to the degeneration of the harmonicity of the measurement signal, and the energy of the main lobe of the signal spectrum representing the target leaks to the side lobe, resulting in that the target position cannot be determined by the spectrum. The optoelectronic phase-locked loop method, the phase comparison method, and the resampling method are used as classical methods for nonlinear correction. However, the optoelectronic phase-locked loop method is difficult to realize in physics and is prone to lose lock under fast sweep and strong nonlinearity, and it is difficult to control the laser source to realize stable output of linear sweep light; the phase comparison method is limited by the phase demodulation accuracy and cannot realize multi-target phase discrimination, making it difficult to realize non-cooperative or multi-target common-path measurement; the resampling method, as the most widely used method for solving nonlinear correction, is difficult to ensure the nonlinear correction effect of the sweep under the phenomenon of asynchronous light frequency caused by the mismatch of the optical path of the interferometer. To solve the problems existing in the above methods, the present application proposes a frequency-modulated nonlinear correction method based on frequency-domain phase shift asynchronous resampling. SUMMARY

[0003] The present application aims to solve the problems in the prior art and proposes a frequency-modulated nonlinear correction method based on frequency-domain phase shift asynchronous resampling.

[0004] The present application is realized by the following technical solutions, and the present application proposes a frequency-modulated nonlinear correction method based on frequency-domain phase shift asynchronous resampling, which comprises:

[0005] Step 1: obtaining the measurement signal i mea (t) and the auxiliary signal i aux (t) by two balanced detectors;

[0006] Step 2: performing fast Fourier transform on i mea (t) of step 1 to obtain I mea (f), calculating the frequency f mea corresponding to the maximum energy of I max1 , and converting f max1 into a target distance rough measurement value R mea1 ;

[0007] Step 3: according to the known auxiliary interferometer length R f and the R mea1, the first-order discrete asynchronous quantity m required for asynchronous processing is calculated;

[0008] Step 4: i aux (t) is obtained by performing asynchronous processing on i auxm (t) of Step 1;

[0009] Step 5: i auxm (k) is obtained by performing asynchronous resampling on i mea (t) of Step 1 using i mea1 (t) as the sampling clock;

[0010] Step 6: I mea1 (f) is obtained by performing a fast Fourier transform on i mea1 (k) of Step 5, and the frequency f mea1 corresponding to the maximum energy of I max2 (f) is calculated; max2 f mea2 is converted into the target distance coarse measurement value R aux ;

[0011] Step 7: N continuous asynchronous quantities τ1, τ2, …, τ N required for asynchronous processing are calculated according to the known auxiliary interferometer length R aux and R mea2 obtained in Step 6;

[0012] Step 8: I aux (f) is obtained by performing a Fourier transform on i aux (t) of Step 1, and phase shift factors exp(–j2πfτ N ) are constructed using τ1, τ2, …, τ n obtained in Step 7 to perform frequency-domain phase shifting on I aux (f), and then inverse Fourier transform is performed to the time domain to obtain N asynchronous clock signals i aux1 (t), i aux2 (t), …, i auxN (t);

[0013] Step 9: i aux1 (t), i aux2 (t), …, i auxN (t) of Step 8 are combined with different weights to obtain The weights of the respective asynchronous clock signals are γ1, γ2, …, γ N ;

[0014] Step 10: i mea (k) is obtained by performing asynchronous resampling on i mea (t) of Step 1 using i mea2 as the sampling clock;mea2 (k), and i mea2 (k) is subjected to a spectrum analysis, thereby determining the target distance R mea .

[0015] Further, in steps 1 and 2, the measurement signal i mea (t) and the auxiliary signal i aux (t) are obtained by two balanced detectors, respectively:

[0016]

[0017] wherein A mea , A aux represent the amplitudes of the measurement signal and the auxiliary signal, respectively, τ mea , τ aux represent the group delay of the measurement interferometer and the auxiliary interferometer, respectively, f0, Δf (n-1) (t) represent the initial optical frequency of the frequency-modulated light source and the n-1th derivative of Δf(t), respectively, Δf(t) is a time-varying sweep nonlinear curve, and N is the maximum order of the sweep nonlinearity.

[0018] The target distance coarse value R mea1 :

[0019]

[0020] wherein f max1 is the frequency corresponding to the maximum spectral energy of i mea (t), c is the speed of light, K is the frequency-modulation rate value of the frequency-modulated light source, and n air is the refractive index in air.

[0021] Further, in step 3, the first-order discrete asynchronous quantity m:

[0022]

[0023] wherein n g represents the refractive index of the optical fiber, and Fs is the sampling frequency of the signal.

[0024] Further, in step 4, the first-order asynchronous clock i aux (t) is obtained by subjecting i auxm (t) of step 1 to asynchronous processing:

[0025]

[0026] wherein τ mea1 represents the group delay of the interferometer with a length of R mea1 , and represents the first-order derivative of i auxm(t) the 3~N order swept nonlinear phase term of the signal phase.

[0027] Further, in steps 5 and 6, i auxm (t) is asynchronously resampled with the phase of the sampling clock to obtain i mea (k) in the k domain: mea1

[0028]

[0029] wherein the phase of i auxm (k) changes linearly with k, k = 1, 2, 3, …, represents the 3~N order swept nonlinear phase term of the signal phase of i mea1 (k).

[0030] The target distance coarse measurement value R mea2 :

[0031]

[0032] wherein f max2 is the frequency corresponding to the maximum spectral energy of i mea1 (k).

[0033] Further, in step 7, the following equation needs to be satisfied:

[0034]

[0035] wherein formula (8) represents the pth equation, and solving the N equations can obtain the N continuous asynchronous quantities τ1, τ2, …, τ N analytical expression, when N = 2, the analytical expression is as follows:

[0036]

[0037] Further, in steps 8 and 9, the N asynchronous clock signals i aux1 (t), i aux2 (t), …, i auxN (t) are obtained:

[0038] i auxn (t) = IFFT [I aux (f)exp(-j2πfτ n )] n = 1, 2, 3, …, N (11)

[0039] The N asynchronous clock signals i aux1 (t), i aux2 (t), …, i​​auxN The phase of (t) is combined with different weights to obtain The weights of the asynchronous clock signals are γ1, γ2, …, γ N ;

[0040]

[0041] Further, in step 10, the i (k) obtained in step 1 is asynchronously resampled with the sampling clock to obtain i mea (k) in the k domain: mea2

[0042]

[0043] The i mea2 (k) is subjected to spectral analysis to determine the target distance R mea :

[0044]

[0045] Wherein, f max3 is the frequency corresponding to the maximum spectral energy of i mea2 (k).

[0046] The application further provides an electronic device, including a memory and a processor, the memory stores a computer program, and the processor realizes the steps of the frequency domain phase shift asynchronous resampling-based frequency modulation nonlinear correction method when executing the computer program.

[0047] The application further provides a computer readable storage medium for storing computer instructions, and the computer instructions realize the steps of the frequency domain phase shift asynchronous resampling-based frequency modulation nonlinear correction method when executed by a processor.

[0048] The application has the following beneficial effects:

[0049] The application can inhibit the problem that the nonlinear correction effect is not ideal due to the asynchronization of the light frequencies of the auxiliary interferometer and the measurement interferometer in the existing synchronous resampling frequency modulation nonlinear correction method, and the frequency domain phase shift resampling can make the correction more accurate, and the correction effect is not limited by the sampling rate. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings. ​

[0051] Figure 1 is a schematic diagram of the light path structure of the present application;

[0052] Figure 2 is a flow chart of the frequency domain phase shift asynchronous resampling based frequency modulation nonlinear correction method of the present application;

[0053] Figure 3 is an experimental diagram in the flow of the present application (Fs=250MHz / s; R aux =15m; R mea ≈248m);

[0054] Figure 4 is a single target measurement spectrum experimental diagram (Fs=250MHz / s; R aux =15m; R mea ≈250m; (a)-(c) represent the ranging spectrum after correction by using the prior resampling method; (d)-(f) represent the ranging spectrum after processing by using the method of the present application);

[0055] Figure 5 is a double target ranging spectrum experimental diagram (Fs=250MHz / s; R aux =15m; the double targets are located near 248m; (a)-(b) represent the ranging spectrum after correction by using the prior resampling method; (c)-(d) represent the ranging spectrum after processing by using the method of the present application, and the sub-diagram in (d) represents an enlarged diagram of the double target ranging spectrum). DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0057] The frequency modulation nonlinear correction method based on frequency domain phase shift asynchronous resampling of the present application is realized based on a frequency sweeping interferometric measurement device, and the frequency sweeping interferometric measurement device is based on the light path structure of a double Mach-Zehnder interferometer, as shown in Figure 1As shown, the swept light output from the frequency-modulated light source is split into measurement light and reference light by coupler 1, which then enter the measurement interferometer and auxiliary interferometer, respectively. The measurement light (splittered by coupler 2) enters the measurement arm of the measurement interferometer, passes through the circulator, exits from the optical system, is transmitted to the target surface for reflection, and the reflected light passes through the optical system and exits from the other end of the circulator. It is then combined with the reference light (splittered by coupler 3) entering the reference arm of the measurement interferometer at coupler 4 to form a measurement signal, which is detected by the balanced detector 1. The measurement light (splittered by coupler 2) and the reference light (splittered by coupler 3) entering the auxiliary interferometer pass through two optical fibers of different lengths and are combined at coupler 5 to form an auxiliary signal, which is detected by the balanced detector 2.

[0058] Specifically, in combination Figures 2-5 This invention proposes a frequency modulation nonlinearity correction method based on frequency domain phase shift asynchronous resampling, the method comprising:

[0059] Step 1: The measurement signal i is obtained by two balanced detectors. mea (t) and auxiliary signal i aux (t);

[0060] Step 2: For i in Step 1 mea (t) is subjected to a fast Fourier transform to obtain I mea (f), calculate I mea The frequency f corresponding to the maximum energy of (f) max1 , will f max1 Convert to coarse target distance R mea1 ;

[0061] Step 3: Based on the known length R of the auxiliary interferometer f R obtained in step 2 mea1 Calculate the first-order discrete asynchronous quantity m required for asynchronous processing;

[0062] Step 4: For i in Step 1 aux (t) is the first-order asynchronous clock i obtained by asynchronous processing. auxm (t);

[0063] Step 5: Using i auxm The phase of (t) is the sampling clock, and the i obtained in step 1 is... mea (t) performs asynchronous resampling to obtain i in the k-domain mea1 (k);

[0064] Step 6: For i in step 5 mea1 (k) Perform a Fast Fourier Transform to obtain I mea1 (f), calculate I mea1 The frequency f corresponding to the maximum energy of (f) max2 , will f max2Convert to coarse target distance R mea2 ;

[0065] Step 7: Based on the known length R of the auxiliary interferometer aux R obtained in step 6 mea2 Calculate the N consecutive asynchronous quantities τ1, τ2, ..., τ required for asynchronous processing. N ;

[0066] Step 8: For i in step 1 aux (t) is subjected to Fourier transform to obtain I aux (f) Using the τ1, τ2, ..., τ obtained in step 7 N Construct the phase shift factor exp(–j2πfτ) n ), to I aux (f) Perform a frequency domain phase shift, and then perform an inverse Fourier transform to the time domain to obtain N asynchronous clock signals i. aux1 (t),i aux2 (t),…,i auxN (t);

[0067] Step 9: For the N asynchronous clock signals i from step 8 aux1 (t),i aux2 (t),…,i auxN The phase of (t) is synthesized with different weights to obtain The weights of each asynchronous clock signal are γ1, γ2, ..., γ N ;

[0068] Step 10: with For the sampling clock, i obtained in step 1 mea (t) performs asynchronous resampling to obtain i in the k-domain mea2 (k), for i mea2 (k) Perform spectral analysis to determine the target distance R. mea .

[0069] In step 1, the measurement signal i is obtained by two balanced detectors respectively. mea (t) and auxiliary signal i aux (t):

[0070]

[0071] Among them, A mea A aux τ represents the amplitude of the measured signal and the auxiliary signal, respectively. mea , τ aux The propagation group delays of the measuring interferometer and the auxiliary interferometer are given by f0 and Δf, respectively. (n-1)(t) represents the initial optical frequency of the frequency-modulated light source and the n-1th derivative of Δf(t), respectively. Δf(t) is the sweep frequency nonlinear curve that varies with time, and N is the maximum order of the sweep frequency nonlinearity.

[0072] In step 2, for i in step 1 mea (t) is subjected to a fast Fourier transform to obtain I mea (f), the experimental results are as follows Figure 3 As shown in (a), calculate I. mea The frequency f corresponding to the maximum energy of (f) max1 , will f max1 Convert to coarse target distance R mea1 The target distance coarse measurement value R mea1 :

[0073]

[0074] Among them, f max1 For i mea The frequency corresponding to the maximum spectral energy of (t), where c is the speed of light, K is the modulation rate of the frequency-modulated light source, and n air is the refractive index in air.

[0075] In step 3, the first-order discrete asynchronous quantity m:

[0076]

[0077] Where, n g Fs represents the refractive index of the optical fiber, and Fs is the sampling frequency of the signal.

[0078] In step 4, for i in step 1 aux (t) is the first-order asynchronous clock i obtained by asynchronous processing. auxm (t):

[0079]

[0080] Where, τ mea1 The length of the interferometer is represented by R. mea1 Group delay, Representing i auxm (t) The 3rd to Nth order swept frequency nonlinear phase terms of the signal phase.

[0081] In step 5, i auxm The phase of (t) is the sampling clock, and the i obtained in step 1 is... mea (t) performs asynchronous resampling to obtain i in the k-domain mea1 (k):

[0082]

[0083] Among them, i auxm Phase of (k) It varies linearly with k, k = 1, 2, 3, ... Representing i mea1 (k) Signal phase 3 to Nth order swept frequency nonlinear phase term;

[0084] In step 6, for i in step 5 mea1 (k) Perform a Fast Fourier Transform to obtain I mea1 (f), the experimental results are as follows Figure 3 As shown in (b), calculate I. mea1 The frequency f corresponding to the maximum energy of (f) max2 , will f max2 Convert to coarse target distance R mea2 The target distance coarse measurement value R mea2 :

[0085]

[0086] Among them, f max2 For i mea1 The frequency corresponding to the maximum spectral energy of (k).

[0087] In step 7, the following equation condition must be satisfied:

[0088]

[0089] Formula (8) represents the p-th equation. Solving the N equations yields the N asynchronous quantities τ1, τ2, ..., τ that can take continuous values, required for asynchronous processing. N The analytical expression, when N=2, is as follows:

[0090]

[0091] In step 8, for step 1, i aux (t) is subjected to Fourier transform to obtain I aux (f) Using the τ1, τ2, ..., τ obtained in step 7 N Construct the phase shift factor exp(–j2πfτ) n ), to I aux (f) Perform a frequency domain phase shift, and then perform an inverse Fourier transform to the time domain to obtain N asynchronous clock signals i. aux1 (t),i aux2 (t),…,i auxN (t); the N asynchronous clock signals i aux1 (t),i aux2 (t),…,i auxN (t):

[0092] i auxn (t) = IFFT[I aux (f)exp(-j2πfτ n )] n=1,2,3,...,N (11)

[0093] In step 9, the N asynchronous clock signals i from step 8 are... aux1 (t),i aux2 (t),…,i auxN The phase of (t) is synthesized with different weights to obtain The weights of each asynchronous clock signal are γ1, γ2, ..., γ N ;

[0094]

[0095] In step 10, the use of For the sampling clock, i obtained in step 1 mea (t) performs asynchronous resampling to obtain i in the k-domain mea2 (k):

[0096]

[0097] to i mea2 (k) Perform spectral analysis, and the experimental results are as follows: Figure 3 As shown in (c), the target distance R is determined. mea :

[0098]

[0099] Among them, f max3 For i mea2 The frequency corresponding to the maximum spectral energy of (k).

[0100] Figure 4 and Figure 5 The results represent the measurement results of a single target and a dual target after applying existing resampling methods and the method described in this invention, respectively.

[0101] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the frequency modulation nonlinear correction method based on frequency domain phase shift asynchronous resampling.

[0102] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of the frequency modulation nonlinear correction method based on frequency domain phase shift asynchronous resampling.

[0103] The memory in the embodiments of the present application can be a volatile memory or a nonvolatile memory, or can include both volatile and nonvolatile memory. Among them, the nonvolatile memory can be a read only memory (ROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically EPROM (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM) used as an external cache. By way of example, and not limitation, many forms of RAM can be used, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchlink DRAM (SLDRAM), and direct rambus RAM (DRRAM). It is noted that the memory of the methods described herein is intended to include, but not be limited to, these and any other suitable types of memory.

[0104] In the above embodiments, all or part of the methods can be implemented by software, hardware, firmware, or any combination thereof. When implemented by software, all or part of the methods can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions can be transferred from one website, computer, server, or data center to another website, computer, server, or data center through wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) manner. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that includes one or more available media sets. The available media can be magnetic media (such as floppy disk, hard disk, magnetic tape), optical media (such as high-density digital video disc (DVD)), or semiconductor media (such as solid state disc (SSD)), etc.

[0105] In the implementation process, each step of the above method can be completed by integrated logic circuit of hardware in the processor or instruction in the form of software. The steps of the method disclosed in the embodiments of the present application can be directly embodied as hardware processor execution, or executed by combination of hardware and software modules in the processor. The software module can be located in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, register, and other mature storage media in the art. The storage medium is located in the memory, and the processor reads the information in the memory and combines the hardware to complete the steps of the above method. To avoid repetition, it will not be described in detail here.

[0106] It should be noted that the processor in the embodiments of the present application can be an integrated circuit chip with a signal processing capability. In the implementation process, each step of the method embodiments can be completed by the integrated logic circuit of hardware or the instruction in the form of software in the processor. The processor mentioned above can be a general processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. The disclosed methods, steps and logic block diagrams in the embodiments of the present application can be implemented or executed. The general processor can be a microprocessor or the processor can also be any conventional processor. The steps of the method disclosed in combination with the embodiments of the present application can be directly embodied as a hardware code processor for execution, or a combination of hardware and software modules in the code processor for execution. The software module can be located in a random access memory, a flash memory, a read only memory, a programmable read only memory or an electrically erasable programmable memory, a register or other mature storage medium in the art. The storage medium is located in the memory, and the processor reads the information in the memory, and combines the hardware to complete the steps of the above method.

[0107] The above describes in detail the frequency domain phase shift asynchronous resampling based frequency modulation nonlinear correction method proposed in the present application. The principle and implementation manner of the present application are described by using specific examples. The above embodiment is only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manner and application range will be changed. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A frequency domain phase shift asynchronous resampling based method for correcting frequency modulation nonlinearity, characterized in that, The method comprises: Step 1: Measurement signal i is obtained from two balanced probes mea (t) with auxiliary signal i aux (t); Step 2: i of Step 1 mea (t) performing a fast Fourier transform to obtain I mea (f), calculating the frequency f mea corresponding to the energy maximum of I max1 (f) max1 converting f mea1 to a target distance coarse value R Step 3: Calculate the length R of the known auxiliary interferometer f R = R + R mea1 , calculate the first-order discrete asynchronous amount m required for asynchronous processing; Step 4: i of step 1 is paired with the first-order asynchronous clock i obtained by asynchronous processing aux (t) is paired with the first-order asynchronous clock i obtained by asynchronous processing auxm (t); Step 5: i auxm (t) is resampled asynchronously with the phase of the sampling clock to obtain i mea (k) in the k domain. mea1 (k) in the k domain. Step 6: i mea1 (k) performing a fast Fourier transform to obtain I mea1 (f), calculating the energy maximum of I mea1 (f) corresponds to a frequency f max2 , converting f max2 to a target distance coarse value R mea2 ; Step 7: Calculate the length R of the known auxiliary interferometer aux R = R + ΔR mea2 , and calculate N consecutive asynchronous quantities τ1, τ2, …, τN needed for asynchronous processing N ; Step 8: i aux (t) of step 1 aux (f) is Fourier transformed to get I N (f) is phase shifted in frequency domain by exp(-j2πfτ n ), and inverse Fourier transformed to time domain, N asynchronous clock signals i aux (t), i aux1 (t), i aux2 (t), …, i auxN (t) are obtained. Step 9: N asynchronous clock signals i of step 8 aux1 (t),i aux2 (t),…,i auxN (t) of step 8 are weighted and combined to obtain The weights of the asynchronous clock signals are γ1, γ2, …, γ N ; Step 10: resample i (t) with sampling clock to get i mea (k) in k domain. mea2 Step 8: analyze i mea2 (k) to determine target distance R mea .

2. The method of claim 1, wherein, In steps 1 and 2, the measurement signals i mea (t) are obtained from two balance detectors, respectively aux (t): where A mea , A aux represent the amplitudes of the measurement signal and the auxiliary signal, respectively, τ mea , τ aux are the group delays of the measurement interferometer and the auxiliary interferometer, respectively, f0, Δf (n-1) (t) are the initial optical frequency of the frequency-modulated light source and the n-1th derivative of Δf(t), respectively, Δf(t) is a time-varying sweep nonlinear curve, and N is the maximum order of the sweep nonlinearity; The target distance rough value R mea1 : where f max1 is the frequency corresponding to the maximum spectral energy of i mea (t), c is the speed of light, K is the frequency modulation rate value of the frequency-modulated light source, n air is the refractive index in air.

3. The method of claim 2, wherein, In step 3, the first-order discrete asynchronous quantity m: where n g represents the refractive index of the optical fiber, and Fs is the sampling frequency of the signal.

4. The method of claim 3, wherein, In step 4, the i aux (t) a first-order asynchronous clock i auxm (t): where τ mea1 represents the group delay of the interferometer with length R mea1 , represents the 3 to Nth order swept nonlinear phase term of the i auxm (t) signal phase.

5. The method of claim 4, wherein, In steps 5 and 6, i auxm The phase of (t) is the sampling clock, and the i obtained in step 1 is... mea (t) performs asynchronous resampling to obtain i in the k-domain mea1 (k): where i auxm Phase of (k) Linearly varying with k, k = 1, 2, 3, …, Represent i mea1 (k) signal phase 3~N order sweep nonlinear phase term The target distance rough value R mea2 : wherein f max2 is the frequency corresponding to the maximum spectral energy of i mea1 (k).

6. The method of claim 5, wherein, In step 7, the following equation needs to be satisfied: wherein, formula (8) represents the pth equation, and N equations are solved to obtain N continuous values of the asynchronous quantities τ1, τ2, …, τN required for asynchronous processing N The analytical expression is as follows when N = 2:

7. The method of claim 6, wherein, In steps 8 and 9, the N asynchronous clock signals i aux1 (t),i aux2 (t),…,i auxN (t): i auxn (t) = IFFT [I aux (f) exp(-j2πfτ n )] n = 1,2,3,...,N (11) N asynchronous clock signals i of step 8 aux1 (t),i aux2 (t),…,i auxN (t) of different weights to obtain The weights of the asynchronous clock signals are γ1, γ2, …, γ N ; 8. The method of claim 7, wherein, In step 10, the i (k) obtained in step 1 is asynchronously resampled with the sampling clock to obtain i mea (t) in the k domain. mea2 (k): To i mea2 (k) performing a spectral analysis to determine the target distance R mea : where f max3 is the frequency corresponding to the maximum spectral energy of i mea2 (k). 9.An electronic device comprising a memory and a processor, the memory storing a computer program, wherein, The processor implements the steps of the method of any one of claims 1-8 when executing the computer program.

10. A computer readable storage medium for storing computer instructions, characterized in that, The computer instructions implement the steps of the method of any one of claims 1-8 when executed by the processor.

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