Strain sensing demodulation method and device based on optical frequency domain reflection, and storage medium

Abstract

The invention provides a strain sensing demodulation method and device based on optical frequency domain reflection and a storage medium. The method comprises the following steps: respectively acquiring detection signals of a calibration optical fiber and a to-be-detected optical fiber and converting the detection signals into a calibration curve and a to-be-detected curve; synchronously sliding and intercepting the calibration curve and the to-be-measured curve based on the first window to obtain a plurality of first local calibration signals and a plurality of first local to-be-measured signals; performing cross-correlation on the first local calibration signal and the first local to-be-measured signal which are corresponding in position, and positioning a first strain position of the to-be-measured optical fiber according to a result; extracting extended data segments at the first strain positions of the calibration curve and the curve to be measured; and intercepting the extended data segment based on synchronous sliding of the second window, performing cross-correlation on the obtained second local calibration signal and the second local to-be-measured signal, and determining a strain value of the to-be-measured optical fiber according to a result. According to the method, the false peak of the non-strain region is suppressed through large window screening, and fine demodulation is only started for the suspicious region, so that the overall calculation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of optical fiber sensing technology, and in particular to a strain sensing demodulation method, apparatus, and storage medium based on optical frequency domain reflection. Background Technology

[0002] Strain measurement is an important technique in precision engineering. Optical Frequency Domain Reflectometry (OFDR) is an advanced instrument based on coherent detection technology, capable of real-time and accurate strain sensing and deformation monitoring, and has been widely used in civil engineering, aerospace, machinery manufacturing, and energy extraction. In OFDR, the main interferometer detects reflection points at different locations on the optical fiber, corresponding to different frequency components of the signal. When local strain occurs in the optical fiber, the Rayleigh scattering spectrum passing through this point will shift. OFDR can measure strain by demodulating the location and magnitude of the Rayleigh scattering spectrum shift in the optical fiber.

[0003] Traditional OFDR strain demodulation employs a cross-correlation algorithm, which calculates and finds peaks by cross-correlation of Rayleigh scattering wavelengths at various locations in the fiber before and after strain. However, the sensing performance of this demodulation algorithm is directly limited by the window width in the cross-correlation algorithm: using a large window width improves the wavelength resolution of the OFDR system but reduces the spatial resolution; an excessively wide window not only results in low spatial resolution but also fails to correctly demodulate strain information. Conversely, using a small window width improves spatial resolution but reduces wavelength resolution. In traditional single-window sliding cross-correlation methods for strain calculation, spurious peaks appear in non-strain regions when the window is too small, leading to incorrect strain assessment. This paper proposes a novel OFDR strain sensing demodulation method based on nested windows. Compared to the traditional cross-correlation algorithm, this two-stage detection process achieves high spatial resolution demodulation results at strain locations while suppressing spurious peaks in non-strain regions. Furthermore, the nested window peak-finding effect balances the trade-off between spatial and wavelength resolution to some extent.

[0004] In existing technologies, CN113607074B, a strain sensing demodulation algorithm based on overlapping windows in optical frequency domain reflection, provides a method of cross-correlation peak finding by overlapping windows to ensure spatial and wavelength resolution. However, this method cannot solve the problem of spurious peaks in the strain detection process. Furthermore, CN117168337B, an OFDR strain edge optimization method and test method, uses window translation to ensure that most of the data within the translated window contains only strain or no strain, thereby obtaining a high-quality cross-correlation peak. However, this patent aims to correct jump errors at strain occurrence edges, and the single-size window still suffers from limited spatial resolution; simultaneously, the threshold aims to detect jumps at strain occurrence edges and address spurious peaks at other non-first strain locations. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a strain sensing demodulation method based on optical frequency domain reflection, which optimizes high spatial resolution, high sensitivity, spurious peak suppression, and computational efficiency.

[0006] In a first aspect, embodiments of the present invention provide a strain sensing demodulation method for optical frequency domain reflection, applied to a distributed optical fiber sensing device for optical frequency domain reflection, the method comprising: The distributed optical fiber sensing device based on the optical frequency domain reflection acquires the detection signals of the calibration fiber and the fiber under test, respectively, and converts the detection signals into calibration curves and test curves, respectively. Based on the synchronous sliding capture of the calibration curve and the test curve in the first window, the obtained preliminary signal segments are processed to obtain multiple first local calibration signals and multiple first local test signals, wherein one first local calibration signal corresponds to one first local test signal in position; Perform cross-correlation calculation on the first local calibration signal and the first local test signal corresponding to the position, and locate the first strain position of the test optical fiber according to the result of the cross-correlation calculation. Extended data segments are extracted from the calibration curve and the test curve corresponding to the first strain position, respectively. The calibration curve and the test curve corresponding to the extended data segment are synchronously slid-triggered based on the second window, and the obtained secondary signal segment is processed to obtain multiple second local calibration signals and second local test signals, wherein the width of the second window is smaller than the width of the first window; A cross-correlation operation is performed on the second local calibration signal and the second local test signal corresponding to the position, and the strain value of the test fiber at the corresponding position is determined based on the result of the cross-correlation operation.

[0007] In some embodiments of the present invention, the device includes a main interferometer and an auxiliary interferometer, wherein the main interferometer and the auxiliary interferometer acquire probe laser from the same linearly tunable laser; the step of the distributed optical fiber sensing device based on the optical frequency domain reflection acquiring the probe signals of the calibration fiber and the fiber under test respectively includes: The main interferometer acquires the detection signals of the calibration fiber and the fiber under test, respectively, and the auxiliary interferometer resamples the main interferometer signal of the detection signals to remove the influence of light source nonlinear noise in the detection signals.

[0008] In some embodiments of the present invention, the step of converting the detection signal into a calibration curve and a test curve includes: Fast Fourier transform is performed on the detection signals corresponding to the calibration fiber and the fiber under test, respectively, to obtain the calibration distance domain information of the calibration fiber and the test distance domain information of the fiber under test. Based on the calibration distance domain information of the calibration fiber and the test distance domain information of the fiber under test, the calibration curve and the test curve are plotted respectively.

[0009] In some embodiments of the present invention, the step of synchronously sliding and capturing the calibration curve and the test curve based on a first window, and processing the obtained preliminary signal segments to obtain multiple first local calibration signals and multiple first local test signals includes: Based on the first window, synchronous sliding interception is performed on the calibration curve and the test curve to obtain multiple first local calibration distance information and multiple first local test distance information; The first local calibration distance information and the first local measured distance information are respectively padded with zeros at the ends and subjected to inverse fast Fourier transform to obtain the first local calibration wavelength signal and the first local measured wavelength signal; The average wavelength domain signals of the first local calibration wavelength signal and the first local test wavelength signal are removed respectively to obtain the first local calibration signal and the first local test signal.

[0010] In some embodiments of the present invention, the step of locating the first strain position of the optical fiber under test based on the result of cross-correlation calculation includes: Based on the resolution requirements and system noise level of the optical frequency domain reflection system, the strain threshold is determined. The strain threshold is compared with the first peak offset obtained by cross-correlation calculation of the calibration fiber and the fiber under test at each position. Based on the comparison result, it is determined whether there is strain at the corresponding position and the first strain position is located based on the determination result.

[0011] In some embodiments of the present invention, the step of performing cross-correlation calculation on the second local calibration signal and the second local test signal corresponding to the position, and determining the strain value of the fiber under test at the corresponding position based on the result of the cross-correlation calculation, includes: The second strain position is determined based on all the second peak offsets obtained by cross-correlation calculation of all the second local calibration signals and the second local test signals; Plot the spectral offset curves based on all the second peak offsets; The average value of all second peak offsets within the second strain position is obtained, and the difference between the average value of the second peak offsets and the average value of the spectral offset curve is calculated to obtain the strain value at the second strain position.

[0012] In a second aspect, embodiments of the present invention provide a distributed optical fiber sensing device for optical frequency domain reflection, characterized in that it is used to perform the strain sensing demodulation method for optical frequency domain reflection described in the above-mentioned embodiments, the device comprising: A linearly tunable laser is used to provide probe laser light to the calibration fiber and the fiber under test; The main interferometer is used to transmit probe laser to the calibration fiber and the fiber under test and demodulate the probe signals transmitted back in the calibration fiber and the fiber under test. The acquisition card is used to receive and process the electrical signals demodulated by the main interferometer; The main interferometer includes a first beam splitter, a first circulator, a first coupler, a polarization beam splitter, and a main balanced photodetector. The first beam splitter transmits the probe laser from the linearly tunable laser to the first circulator and the first coupler, respectively. The first circulator transmits the probe laser to the fiber under test and the calibration fiber, and transmits the probe signal fed back from the fiber under test and the calibration fiber to the first coupler. The first coupler couples the probe laser and the probe signal into a beat frequency signal, and transmits the beat frequency signal to the polarization beam splitter. The polarization beam splitter eliminates the polarization fading noise in the beat frequency signal and transmits the beat frequency signal to the balanced photodetector. The main balanced photodetector converts the beat frequency signal into an electrical signal and transmits it to the acquisition card.

[0013] In some embodiments of the present invention, the device further includes an auxiliary interferometer for removing the influence of light source nonlinear noise in the detection signal; the auxiliary interferometer includes a second circulator, a second coupler, an auxiliary balanced photodetector, a time-delay fiber, a first Faraday rotator, and a second Faraday rotator; the second circulator is used to transmit the detection laser to the second coupler; the second coupler is used to transmit the detection laser to the time-delay fiber, the first Faraday rotator, and the second Faraday rotator and receive the reflected signal, and the second coupler is also used to transmit the reflected signal to the second circulator and the auxiliary balanced photodetector respectively; the second circulator is used to transmit the reflected signal to the auxiliary balanced photodetector; the auxiliary balanced photodetector is used to convert the reflected signal transmitted by the second circulator and the second coupler into an electrical signal and transmit it to the acquisition card.

[0014] Thirdly, embodiments of the present invention provide a computer device including a memory and a processor, wherein the memory is used to store at least one program, and the processor is used to load the at least one program to execute the strain sensing demodulation method for optical frequency domain reflection described in the above-mentioned embodiments.

[0015] Fourthly, a computer-readable storage medium stores computer-executable instructions for causing a computer to perform the strain sensing demodulation method for optical frequency domain reflection as described in the embodiments above.

[0016] The strain sensing demodulation method based on optical frequency domain reflection in this invention performs a preliminary scan using a large first window to locate potential strain regions, followed by fine measurement within the located region using a small second window, thus achieving a two-stage refined strain detection process. This method offers the following advantages: the large window effectively suppresses spurious peaks in non-strain regions; the coordinated operation of the large and small windows balances spatial resolution and measurement sensitivity; and fine demodulation is initiated only for suspicious regions, significantly improving overall computational efficiency. Attached Figure Description

[0017] Figure 1 This is a flowchart of the strain sensing demodulation method for optical frequency domain reflection according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the extended data segment according to an embodiment of the present invention; Figure 3 This is a structural diagram of a distributed optical fiber sensing device for optical frequency domain reflection according to another embodiment of the present invention; Figure 4 This is a comparison chart of measurement results for the strain sensing demodulation method based on optical frequency domain reflection that does not employ the embodiments of the present invention; Figure 5 The graph shows the measurement results of the strain sensing demodulation method based on optical frequency domain reflection according to an embodiment of the present invention. Figure 6 This is a schematic diagram of the cross-correlation spectral fluctuations of the OFDR system according to an embodiment of the present invention; Figure 7 This is a structural diagram of a computer device provided in another embodiment of the present invention.

[0018] Figure reference numerals: 1. Linear tunable laser; 2. 95:5 beam splitter; 3. Second circulator; 4. First beam splitter; 5. Second coupler; 6. First circulator; 7. Third balanced photodetector; 8. First coupler; 9. Detection fiber of main interferometer; 10. Delay fiber of auxiliary interferometer; 11. First Faraday rotator; 12. Second Faraday rotator; 13. First polarization beam splitter; 14. Second polarization beam splitter; 15. First balanced photodetector; 16. Second balanced photodetector; 17. Data acquisition card; 18. Computer; 19. Auxiliary interferometer; 20. Main interferometer. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0021] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0022] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0023] The concepts mentioned in the embodiments of the present invention are explained below: OFDR system: Optical Frequency Domain Reflectometry, is a high-precision sensing system that uses linear frequency modulated laser and interferometry to achieve distributed strain and temperature measurement with millimeter-level spatial resolution over an entire optical fiber; Cross-correlation algorithm: It is a method to measure the similarity between two signals by sliding comparison. It calculates the degree of matching of one signal with respect to another signal at different offset positions. When the two are best aligned, the correlation function will show a peak. The position offset of the peak directly reflects the relative displacement between the two signals. Rayleigh scattering is an elastic scattering phenomenon caused by the microscopic density inhomogeneity of the optical fiber material itself. When light propagates in an optical fiber, it interacts with particles much smaller than its wavelength, causing a small portion of the light to change direction and scatter in all directions. The scattered light that returns along its original path is called Rayleigh backscattering. The wavelength (frequency) of this scattered light is the same as the incident light, and its scattering intensity is fixed after the optical fiber is manufactured and randomly distributed with position, like a unique "fingerprint" of the optical fiber. FFT: Fast Fourier Transform, is an efficient algorithm that can quickly decompose a signal from a time-domain waveform that varies with time into its different frequency components, thereby obtaining a frequency domain representation of the signal.

[0024] The control method of the present invention will be further described below with reference to the accompanying drawings.

[0025] Reference Figures 1-5 , Figure 1 This is a flowchart of the strain sensing demodulation method for optical frequency domain reflection provided in an embodiment of the present invention. Figure 3 As another embodiment of the present invention, a distributed optical fiber sensing device for optical frequency domain reflection includes the following method: Step S100: The distributed optical fiber sensing device based on optical frequency domain reflection acquires the detection signals of the calibration fiber and the fiber under test, respectively, and converts the detection signals into calibration curves and test curves, respectively. It should be noted that in step S100, the calibration fiber is a standard fiber that has not undergone strain, and the detection signals obtained from the calibration fiber and the fiber under test are Rayleigh backscattered signals. In order to obtain the specific strain value of the fiber under test, this embodiment of the invention applies a cross-correlation algorithm. Therefore, it is necessary to obtain the Rayleigh backscattered signals of the two types of fibers separately, and determine whether the fiber under test has undergone strain based on the degree of matching between the two. It is understood that in the actual detection process, the detection signal of the calibration fiber can be obtained only once for calibration, or it can be repeatedly obtained and the average value taken as the calibration; different fibers under test can be replaced as needed, and the corresponding detection signals can be repeatedly obtained.

[0026] Step S200: Based on the first window, synchronously slide and capture the calibration curve and the curve to be tested, and process the obtained preliminary signal segment to obtain multiple first local calibration signals and multiple first local test signals, wherein one first local calibration signal corresponds to one first local test signal in position; It should be noted that step S200 is the coarse localization step of the demodulation method provided in this embodiment of the invention. Its core purpose is to divide the complete and continuous Rayleigh scattering curve into a series of continuous, finite-length local signal segments, i.e., preliminary signal segments. After a series of window processing steps, a first local calibration signal and a first local test signal can be obtained, laying the foundation for subsequent cross-correlation calculations. By synchronously sliding the first window, the local scattering signals of the test fiber and the calibration fiber at each possible location can be systematically compared. If the two signal segments in a certain local region are highly similar, the cross-correlation value will be high, indicating that no strain or very small strain has occurred in that region; conversely, if the similarity is low, it indicates that the spectrum of that region may have drifted due to strain, suggesting that a strain point may exist there.

[0027] Step S300: Perform cross-correlation calculation on the first local calibration signal and the first local test signal corresponding to the position, and locate the first strain position of the fiber under test according to the result of the cross-correlation calculation. It should be noted that in step S300, by performing cross-correlation on each pair of signals generated in step S200, the similarity between them is quantitatively evaluated, and the approximate region of strain on the fiber under test is preliminarily identified and locked based on significant changes in similarity. For a region without strain, the local test signal and the local calibration signal will highly overlap, and the cross-correlation function will produce a sharp peak at the zero displacement. Conversely, if a region has undergone strain, the signal shapes of the two signals are similar but have undergone relative translation, the peak position of the cross-correlation function will shift, and the amplitude of the peak may decrease due to signal distortion. By detecting anomalies in these peak characteristics (position shift, peak amplitude), it can be determined whether strain exists within the local window. This step marks the possible locations of strain in the fiber under test, thereby narrowing down the possible locations of strain in the fiber under test to several suspicious points.

[0028] Step S400: Extract extended data segments from the calibration curve and the curve to be measured corresponding to the first strain position, respectively. It should be noted that in step S400, the first window used in steps S200 and S300 is relatively large, and strain may occur at any location within the window. When the strain point is close to the window boundary, in the next step of using a small-sized window for sliding calculation, the cross-correlation calculation may fail or produce erroneous peaks (i.e., false peaks) due to the signal segment being too short or the features being incomplete. Therefore, this embodiment of the invention extracts a longer extended data segment, ensuring sufficient boundary-free signal data before and after the strain point, providing a reliable working range for fine analysis. In one embodiment of the invention, as... Figure 4 As shown, if the first window is M, the extracted extended data segment can be a data segment with a total length of 3M, encompassing the strain occurrence positions of both the calibration curve and the test curve, the window before the strain occurrence position, and the window after the strain occurrence position. It is understandable that, since subsequent operations involving secondary window sliding and cross-correlation calculations are required on the extended data segment, it is necessary to extend the data segment simultaneously on both the calibration curve and the test curve, rather than solely on the test curve.

[0029] Step S500: Based on the second window, synchronously slide and capture the calibration curve and the curve to be tested corresponding to the extended data segment, and process the obtained secondary signal segment to obtain multiple second local calibration signals and second local test signals, wherein the width of the second window is smaller than the width of the first window; It should be noted that the purpose of step S500 is to use a smaller second window N within the extended data segment provided in step S400, which has eliminated boundary effects, to rescan the initially located suspected strain region with higher spatial resolution. This generates corresponding signal pairs (the second local calibration signal and the second local test signal corresponding to the position) for the final calculation of the precise strain value at each specific data point. These signal pairs originate from the signal segments of the calibration curve and the test curve, respectively, after a second sliding truncation. In some embodiments of the present invention, the second window N is much smaller than the first window M. Based on this, it can capture the Rayleigh scattering characteristics of smaller regions on the fiber under test, resulting in a strain distribution map with higher positional accuracy. It can distinguish denser strain points or steeper strain gradients, allowing subsequent cross-correlation calculations to more directly and accurately reflect the spectral shift caused by strain at that specific point.

[0030] Step S600: Perform cross-correlation calculation on the second local calibration signal and the second local test signal corresponding to the position, and determine the strain value of the fiber under test at the corresponding position based on the result of the cross-correlation calculation.

[0031] It should be noted that in step S600, the high-resolution local signal pair generated in step S500 (the second local calibration signal and the second local signal to be measured corresponding to the position) is used to accurately calculate the specific strain value of the fiber under test at each tiny spatial point through high-precision cross-correlation calculation. It can be understood that the purpose of the cross-correlation calculation in step S600 is no longer coarse positioning, but precise measurement. By calculating the precise offset of the cross-correlation peak between the second local calibration signal and the second local signal to be measured, the frequency shift of the Rayleigh scattering spectrum caused by strain can be determined. Based on the known strain-frequency sensitivity coefficient, this frequency shift can be directly converted into a precise strain value (usually in microstrain, µε). Due to the small second window and short sliding step, this step can output a continuous, point-by-point strain distribution curve within the extended data segment coverage area with the system's highest spatial resolution (e.g., millimeter level). A comparison of measurement results using the strain sensing demodulation method based on optical frequency domain reflection without employing this embodiment of the invention is shown in the figure. Figure 5 As shown in the figure, the measurement results of the strain sensing demodulation method based on optical frequency domain reflection according to an embodiment of the present invention are as follows. Figure 6 As shown.

[0032] It should be noted that in steps S100 to S600, the strain sensing demodulation process of optical frequency domain reflection begins with the synchronous acquisition and conversion of Rayleigh scattering signals from the unstrained calibration fiber and the fiber under test. Subsequently, the system uses a relatively wide initial window to synchronously slide along the two curves, extracting continuous local signal segments. By calculating the cross-correlation function of these new local signal segments, the system quickly identifies the segments in the fiber under test where the scattering characteristics change significantly, completing the initial strain region localization. After determining the potential strain region, the system truncates an extended data segment longer than the initial window, centered on each region. This operation aims to provide sufficient signal buffering for subsequent analysis and effectively avoid boundary effects caused by truncating scattering characteristics. Within this extended segment, the system uses a smaller, narrower window for high-density sliding, again truncating the corresponding local signals. Finally, by performing precise cross-correlation operations on these high spatial resolution local signal pairs and accurately tracking their peak offset, the system can calculate the precise strain value of the fiber at each specific location, thereby achieving high-resolution measurement of the strain distribution. This method achieves high spatial resolution quantization of strain by combining initial positioning with wide window and precise demodulation with narrow window, ensuring measurement efficiency. Compared with traditional methods that use a single window size and rely on high overlap sliding, the two-stage positioning strategy adopted in this invention shows significant advantages in computational efficiency and result reliability. Although the traditional window overlap method can improve positioning accuracy through high-density sampling, the computational cost is too high because a complete cross-correlation operation is required for each sliding step. At the same time, the single-window method is prone to false peaks when the strain point is near the window boundary due to incomplete signal features. In contrast, this method quickly screens and locks the suspicious area with a wide window, and then uses a narrow window for fine demodulation within the extended data segment. This not only greatly reduces unnecessary dense calculations, but also fundamentally eliminates boundary effects by providing a sufficient signal buffer area, ensuring the accuracy of strain positioning and the reliability of strain value calculation.

[0033] Additionally, in one embodiment, reference is made to Figure 1 , Figure 3 ,exist Figure 1 In step S100 of the illustrated embodiment, the device includes a main interferometer 20 and an auxiliary interferometer 19. The main interferometer 20 and the auxiliary interferometer 19 obtain probe laser light from the same linearly tunable laser 1. This step also includes, but is not limited to, the following steps: Step S101: Based on the main interferometer 20, the detection signals of the calibration fiber and the fiber under test are acquired respectively, and the detection signals are resampled by the auxiliary interferometer 19 to remove the influence of the nonlinear noise of the light source in the detection signals.

[0034] It should be noted that in actual use, tunable lasers in OFDR systems all exhibit sweep frequency nonlinearity. That is, the laser frequency does not change along a perfect straight line over time, but rather as a fluctuating curve. This means the sweep speed γ is not a constant. Because γ is variable, even for a fixed point on the fiber, the generated beat signal frequency f_beat will fluctuate over time. In this case, if an FFT is directly performed on the beat signal of the main interferometer 20, this frequency fluctuation will lead to spectral broadening, peak value reduction, and resolution degradation. Therefore, in this embodiment of the invention, to eliminate the effects of the above-mentioned defects, a resampling method based on the auxiliary interferometer 19 is adopted. The principle is that since the main interferometer 20 and the auxiliary interferometer 19 use the same laser source, the sweep frequency nonlinearity they experience is completely synchronized and consistent. Therefore, the signal from the auxiliary interferometer 19 provides a real-time reference for measuring the instantaneous sweep frequency state of the laser. Based on this, the core idea of ​​resampling is: instead of performing FFT on the signal of the master interferometer 20 at sampling points with equal time intervals, it maps the signal to sampling points with equal optical frequency intervals before performing FFT. This transforms the signal of the master interferometer 20 from a signal S(t) distorted by both time t and nonlinear γ(t) into a signal S(ν) that is linearly related only to the optical frequency ν. Then, performing FFT on this new signal S(ν), which is uniformly sampled in the optical frequency domain, is equivalent to returning to the ideal linear frequency sweep situation. The beat frequency f_beat and the distance z re-establish a stable and linear correspondence, thereby eliminating the spectral broadening and resolution degradation problems caused by the nonlinearity of the laser frequency sweep.

[0035] Additionally, in one embodiment, in Figure 1 Step S100 in the illustrated embodiment further includes, but is not limited to, the following steps: Step S110: Perform fast Fourier transform on the detection signals corresponding to the calibration fiber and the fiber under test respectively to obtain the calibration distance domain information of the calibration fiber and the test distance domain information of the fiber under test. Step S120: Based on the calibration distance domain information of the calibration fiber and the test distance domain information of the fiber under test, the calibration curve and the test curve are plotted respectively.

[0036] It should be noted that the original probe signal acquired by the OFDR system is an interference beat frequency signal. When the probe laser emitted by the linearly tunable laser 1 propagates in the optical fiber, countless scattering points inside it generate weak backscattered Rayleigh light. These scattered lights return and encounter the reference light, causing interference. Since the optical path lengths of the scattered light from different distances are different, the beat frequencies generated after their interference with the reference light are also different. Therefore, this signal is the result of the superposition of all beat frequency signals of different frequencies, and it is impossible to directly analyze the specific location of the Rayleigh scattered light from this signal. Steps S110 to S120 convert the above signal into distance domain information that can directly reflect the Rayleigh scattering intensity at each point along the optical fiber by performing a fast Fourier transform on the resampled probe signal. This process decouples the originally mixed time-based interference waveform into a scattering intensity distribution map based on spatial location, so that scattering points at different physical locations on the optical fiber can be accurately distinguished on the curve. The calibration curve and the test curve obtained thus provide a comparison benchmark for subsequent point-by-point comparison and strain positioning using cross-correlation algorithms.

[0037] Additionally, in one embodiment, in Figure 1 Step S200 of the illustrated embodiment also includes, but is not limited to, the following steps: Step S210: Based on the first window, synchronous sliding interception is performed on the calibration curve and the curve to be measured to obtain multiple first local calibration distance information and multiple first local distance information to be measured; Step S220: Perform zero-padding at the ends and inverse fast Fourier transform on the first local calibration distance information and the first local distance to be measured information respectively to obtain the first local calibration wavelength signal and the first local distance to be measured wavelength signal. Step S230: Remove the average wavelength domain signal of the first local calibration wavelength signal and the first local test wavelength signal respectively to obtain the first local calibration signal and the first local test signal.

[0038] It should be noted that step S210 is the process of processing the range-domain information obtained in the above-described embodiments into a wavelength-domain signal that facilitates cross-correlation operations. Specifically, step S210 uses a large first window M for sliding truncation, aiming to extract segments containing sufficient Rayleigh scattering features from the complete range-domain curve; these segments are all range-domain information. Subsequently, step S220, through zero-padding at the ends and inverse fast Fourier transform, does not simply aim to restore the signal to its original state, but rather to generate an interpolated, high-resolution "pseudo" wavelength-domain spectrum within a local range, thereby encoding the strain information as a shift of the spectrum along the wavelength axis. Zero-padding at the ends increases the signal length by adding zero values ​​to the end of the signal, which is equivalent to interpolation in the transformed wavelength domain, thereby improving wavelength resolution. Step S230 is a zero-meaning process, the purpose of which is to eliminate the DC component (i.e., the average value of the wavelength-domain signal) in the signal, ensuring that subsequent cross-correlation operations can focus on the similarity comparison of the signal waveform and avoid interference from DC peaks to weak strain shift peaks. In cross-correlation calculations, the presence of a DC component generates a very large peak at the center of the cross-correlation function. This peak overwhelms the typically smaller offset peaks caused by strain, thus interfering with the judgment. Specifically, the method for calculating the average value of a wavelength domain signal is to find the arithmetic mean of all data points in a discrete wavelength domain signal containing L data points.

[0039] Additionally, in one embodiment, in Figure 1 Step S300 of the illustrated embodiment also includes, but is not limited to, the following steps: Step S310: Determine the strain threshold based on the resolution requirements of the optical frequency domain reflection system and the system noise level; Step S320: Compare the strain threshold with the first peak offset obtained by cross-correlation calculation of the calibration fiber and the fiber under test at each position, determine whether there is strain at the corresponding position based on the comparison result, and locate the first strain position based on the determination result.

[0040] It should be noted that in steps S310 to S320, the purpose of setting the strain threshold value is to determine whether the strain location has been identified and whether small window analysis needs to be initiated. The strain threshold value should be set based on the system's noise level and resolution requirements. Value can be understood as: Value = k·σ······Equation ①, In Equation ①, k is the reliability coefficient, which depends on the resolution requirements of the OFDR system, and σ is the standard deviation, describing the noise level of the OFDR system. The value is calculated by performing multiple measurements on the probe fiber using the OFDR system under the same conditions during cross-correlation demodulation within a large window, obtaining the cross-correlation offset data of the signal. The spectral fluctuation range σ is then calculated from the offset data. It is understood that the value of k can be determined based on experience and requirements. During the sensing process, different systems require different value pre-calibrations; the larger the k value, the lower the false positive rate of the OFDR system, and the smaller the k value, the higher the resolution of the OFDR system. In some embodiments of this invention, the value of k is 1.2-1.5.

[0041] The strain threshold value is determined before detection. Once determined, it can be compared with the first peak offset obtained by cross-correlation calculation between the calibrated fiber and the fiber under test to locate the first strain position. Specifically, the detailed steps for locating the first strain position are as follows: 1) Within the expected strain measurement range, for n strain conditions, use the OFDR system to acquire data at two different times.

[0042] 2) Perform n cross-correlation operations on n sets of data.

[0043] 3) In the case of a single large window M, cross-correlate the two sets of data from n data groups to obtain the spectral fluctuation curve under the same link, and calculate the spectral fluctuation range σ based on the n sets of spectral offset data. Figure 5 The cross-correlation spectral fluctuations of the OFDR system are presented for every 200 με variation in the range of 0–2000 με.

[0044] Additionally, in one embodiment, in Figure 1 Step S600 in the illustrated embodiment further includes, but is not limited to, the following steps: S610, determine the second strain position based on all the second peak offsets obtained by cross-correlation calculation of all second local calibration signals and second local test signals; S620, plots spectral offset curves based on all second peak offsets; S630, obtain the average value of all second peak offsets within the second strain position, and subtract the average value of the second peak offsets from the average value of the spectral offset curve to obtain the strain value at the second strain position.

[0045] It should be noted that in steps S610 to S630, the process of performing cross-correlation to obtain the second peak offset is the same as in the above-described embodiments. The only difference is that the objects of this cross-correlation operation are the second local calibration signal and the second local test signal from the extended data segment. These signal pairs are obtained by sliding and processing a second window N smaller than the first window M. Through the cross-correlation operation of the small window, the strain point is accurately located within the coarse positioning area, and several second strain positions are obtained. All the obtained second peak offsets (including those with strain and those without strain, with the second peak offset of those without strain being 0) are plotted as a spectral offset curve, and the average value of the local offset of the accurately located strain point is calculated. Then, the difference between this local average value and the global average value of the entire curve is taken to obtain the accurate strain value of the strain point at the second strain position. The purpose of the processing in steps S620 to S630 is to smooth the Gaussian noise with random fluctuations within the extended data segment and to eliminate common background drift interference caused by the system itself or environmental disturbances.

[0046] Secondly, referring to Figure 3 This invention also provides a distributed optical fiber sensing device for optical frequency domain reflection, used to perform the strain sensing demodulation method for optical frequency domain reflection described in the above-mentioned embodiments. The device includes: Linearly tunable laser 1 is used to provide probe laser to the calibration fiber and the fiber under test; The main interferometer 20 is used to transmit probe lasers to the calibration fiber and the fiber under test and to demodulate the probe signals transmitted back from the calibration fiber and the fiber under test. Acquisition card 17 is used to receive and process the electrical signals demodulated by the main interferometer 20; The main interferometer 20 includes a first beam splitter 4, a first circulator 6, a first coupler 8, a polarization beam splitter, and a main balanced photodetector. The first beam splitter 4 is used to transmit the probe laser transmitted from the linearly tunable laser 1 to the first circulator 6 and the first coupler 8, respectively. The first circulator 6 is used to transmit the probe laser to the fiber under test and the calibration fiber, and to transmit the probe signals fed back from the fiber under test and the calibration fiber to the first coupler 8. The first coupler 8 is used to couple the probe laser and the probe signal into a beat frequency signal, and to transmit the beat frequency signal to the polarization beam splitter. The polarization beam splitter is used to eliminate the polarization fading noise in the beat frequency signal, and to transmit the beat frequency signal to the balanced photodetector. The main balanced photodetector is used to convert the beat frequency signal into an electrical signal and transmit it to the acquisition card 17.

[0047] It should be noted that the distributed optical fiber sensing device for optical frequency domain reflection includes: a linearly tunable laser 1, a 95:5 beam splitter 2, an auxiliary interferometer 19, a main interferometer 20, a data acquisition card 17, and a computer 18. Among them, the main interferometer 20 includes: a first beam splitter 4 (also a 95:5 beam splitter 2), a first circulator 6, the main interferometer 20 optical fiber, a first coupler 8 (a 50:50 coupler), polarization beam splitters (including a first polarization beam splitter 13 and a second polarization beam splitter 14), and balanced photodetectors (including a first balanced photodetector 15 and a second balanced photodetector 16). The main interferometer 20 (20) is the core of the distributed optical fiber sensing device for optical frequency domain reflection. By demodulating the offset of the Rayleigh scattering spectrum in the detection fiber, changes in external physical factors such as strain can be sensed. Specifically, port b of the first beam splitter 4 is connected to port a of the first coupler 8, and port b of the first beam splitter 4 outputs a probe laser with a power ratio of 5%; port c of the first beam splitter 4 is connected to port a of the first circulator 6, and port c of the first beam splitter 4 outputs a probe laser with a power ratio of 95%; port b of the first circulator 6 is connected to port b of the first coupler 8; port c of the first circulator 6 is connected to the probe fiber 9 of the main interferometer via the stretching region; port c of the first coupler 8 is connected to port a of the first polarization beam splitter 13; port b of the first polarization beam splitter 13 is connected to the first... The input terminal of a balanced photodetector 15 is connected; the c port of the first polarization beamsplitter 13 is connected to the input terminal of the first balanced photodetector 15; the d port of the first coupler 8 is connected to the a port of the second polarization beamsplitter 14; the b port of the second polarization beamsplitter 14 is connected to the input terminal of the second balanced photodetector 16; the c port of the second polarization beamsplitter 14 is connected to the input terminal of the second balanced photodetector 16; the output terminal of the second balanced photodetector 16 is connected to the input terminal of the data acquisition card 17; the output terminal of the second balanced photodetector 16 is connected to the input terminal of the data acquisition card 17.

[0048] Additionally, in one embodiment, reference is made to Figure 3 The device also includes an auxiliary interferometer 19, which is used to remove the influence of nonlinear noise from the light source in the detection signal. The auxiliary interferometer 19 includes a second circulator 3, a second coupler 5, an auxiliary balanced photodetector, a time-delay fiber, a first Faraday rotator 11, and a second Faraday rotator 12. The second circulator 3 is used to transmit the detection laser to the second coupler 5. The second coupler 5 is used to transmit the detection laser to the time-delay fiber, the first Faraday rotator 11, and the second Faraday rotator 12 and to receive the reflected signal. The second coupler 5 is also used to transmit the reflected signal to the second circulator 3 and the auxiliary balanced photodetector, respectively. The second circulator 3 is used to transmit the reflected signal to the auxiliary balanced photodetector. The auxiliary balanced photodetector is used to convert the reflected signal transmitted by the second circulator 3 and the second coupler 5 into an electrical signal and transmit it to the acquisition card 17.

[0049] The auxiliary interferometer 19 includes: a second circulator 3, a second coupler 5 (50:50 coupler), an auxiliary interferometer delay fiber 10, a first Faraday rotator 11, a second Faraday rotator 12, and a first balanced photodetector 15. The auxiliary interferometer 19 is used to acquire a reference signal containing nonlinear noise from the light source, and to compensate for the detection signal of the main interferometer 20, changing the sampling of the detection signal from equal time intervals to equal frequency intervals. Its purpose is to remove the influence of nonlinear noise from the light source in the detection signal of the main interferometer 20. Specifically, the linearly tunable laser 1 is connected to the input terminal of the acquisition card 17; the tunable laser is connected to port a of the 95:5 beam splitter 2; port b of the 95:5 beam splitter 2 is connected to port a of the second circulator 3, and port b of the 95:5 beam splitter 2 outputs a probe laser with a 5% power ratio; port c of the 95:5 beam splitter 2 is connected to port a of the second beam splitter, and port c of the 95:5 beam splitter 2 outputs a laser with a 95% power ratio; port b of the second circulator 3 is connected to the second coupler 5. The second coupler 3 has port a connected to the input of the third balanced photodetector 7; port c of the second coupler 5 is connected to the input of the third balanced photodetector 7; port c of the second coupler 5 is connected to the first Faraday rotator 11 via the delay fiber 10 of the auxiliary interferometer; port d of the second coupler 5 is connected to the second Faraday rotator 12; the output of the third balanced photodetector 7 is connected to the input of the acquisition card 17; and the output of the acquisition card 17 is connected to the computer 18.

[0050] In one specific embodiment of the present invention, when the device is working, the linearly tunable laser 1 can be started to tune upon connection to a power source. The synchronous trigger signal of the linearly tunable laser 1 is transmitted to the external trigger input terminal of the acquisition card 17 as the external trigger signal of the acquisition card 17. The emitted light of the linearly tunable laser 1 enters through port a of the 95:5 beam splitter 2, enters through port b of the 95:5 beam splitter 2, enters through port a of the second circulator 3, exits through port b of the second circulator 3, enters through port a of the second coupler 5, and exits through ports c and d of the second coupler 5 at a ratio of 50:50, respectively entering the first Faraday rotating mirror 11 after passing through the delay fiber 10 of the auxiliary interferometer. The light is reflected by the second Faraday rotator 12, and the two reflected beams enter from ports c and d of the second coupler 5 respectively. After being combined, they exit from ports a and b of the second coupler 5 in a 50:50 ratio. The light exiting from port a of the second coupler 5 enters port b of the first circulator 6 and exits from port c of the first circulator 6 to the input end of the first balanced photodetector 15. The light exiting from port b of the second coupler 5 exits to the input end of the third balanced photodetector 7. The third balanced photodetector 7 converts the detected light signal into an interference beat frequency signal and transmits it to the acquisition card 17. The acquisition card 17 transmits the acquired analog electrical signal to the computer 18.

[0051] The output light from the linearly tunable laser 1 also enters through port a of the 95:5 beam splitter 2, passes through port c of the 95:5 beam splitter 2, and enters port a of the first beam splitter 4. The first beam splitter 4 splits the light into two beams, which exit from ports b and c of the first beam splitter 4, respectively. The light exiting from port b of the first beam splitter 4 enters port a of the first coupler 8, while the light exiting from port c of the first beam splitter 4 enters port a of the first circulator 6 and exits from port b of the first circulator 6. After passing through the probe fiber 9 of the master interferometer (which includes a stretcher), backscattered Rayleigh light is generated at the end and reflected back into port b of the first circulator 6. The light then exits from port c of the first circulator 6 and enters port b of the first coupler 8, where it is combined with the light entering from port a of the first coupler 8 and exits at a 50:50 ratio to ports a of the first polarization beam splitter 13 and the second polarization beam splitter 14, respectively. Light entering through port a of the first polarization beamsplitter 13 is split into vertically polarized light and horizontally polarized light. The vertically polarized light is output from port b of the first polarization beamsplitter 13 to the input of the first balanced photodetector 15, and the horizontally polarized light is output from port c of the first polarization beamsplitter 13 to the input of the second balanced photodetector 16. Light entering through port a of the second polarization beamsplitter 14 is also split into vertically polarized light and horizontally polarized light. The vertically polarized light is output from port b of the second polarization beamsplitter 14 to the input of the first balanced photodetector 15, and the horizontally polarized light is output from port c of the second polarization beamsplitter 14 to the input of the second balanced photodetector 16. The first balanced photodetector 15 and the second balanced photodetector 16 convert the acquired beat frequency interference signals into electrical signals and transmit them to the acquisition card 17. The acquisition card 17 then transmits the acquired analog electrical signals to the computer 18.

[0052] It should be noted that in the above embodiments, the linearly tunable laser 1 is used to provide a light source for the fiber optic sensing device, and it can achieve a high linearity and wide sweep frequency range tuning output. The first coupler 8 and the second coupler 5 are used for optical beat frequency interference. The delay fiber 10 of the auxiliary interferometer is used to obtain beat frequency signals with different optical paths of the interferometer arm and the reference arm. The dominant frequency of the beat frequency signal can be calculated from the tuning range, tuning rate, and optical path difference between the two arms of the interferometer. The first Faraday rotator 11 and the second Faraday rotator 12 are used to provide reflection for the interferometer and can eliminate the polarization fading phenomenon of the auxiliary interferometer 19. The function of the first polarization beam splitter 13 and the second polarization beam splitter 14 is to decompose the incident light into two linearly polarized beams with orthogonal polarization directions, eliminating the influence of polarization fading noise. The function of the first balanced photodetector 15 and the second balanced photodetector 16 is to convert the optical beat frequency signal into an electrical signal and filter out the combined frequency term. Computer 18 processes the interference signals acquired by the acquisition device to realize fiber optic sensing based on long-distance fiber optic gratings for measuring distributed fiber stress in optical frequency domain reflection.

[0053] like Figure 7 As shown, Figure 7 This is a structural diagram of a computer device provided in one embodiment of the present invention. The present invention also provides a computer device, comprising: The processor 801 can be implemented using a general-purpose central processing unit (CPU), microprocessor, application specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this application. The memory 802 can be implemented as a read-only memory (ROM), static storage device, dynamic storage device, or random access memory (RAM). The memory 802 can store the operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 802 and is called and executed by the processor 801 to execute the strain sensing demodulation method for optical frequency domain reflection of the embodiments of this application. The 803 input / output interface is used to implement information input and output. The communication interface 804 is used to enable communication and interaction between this device and other devices. Communication can be achieved through wired means (such as USB, network cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.). Bus 805 transmits information between various components of the device (e.g., processor 801, memory 802, input / output interface 803, and communication interface 804); The processor 801, memory 802, input / output interface 803, and communication interface 804 are connected to each other within the device via bus 805.

[0054] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof. The device embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separate, and may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0055] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically include computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0056] The above provides a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

Claims

1. A strain sensing demodulation method for optical frequency domain reflection, characterized in that, A distributed optical fiber sensing device applied to optical frequency domain reflection, the method comprising: The distributed optical fiber sensing device based on the optical frequency domain reflection acquires the detection signals of the calibration fiber and the fiber under test, respectively, and converts the detection signals into calibration curves and test curves, respectively. Based on the synchronous sliding capture of the calibration curve and the test curve in the first window, the obtained preliminary signal segments are processed to obtain multiple first local calibration signals and multiple first local test signals, wherein one first local calibration signal corresponds to one first local test signal in position; Perform cross-correlation calculation on the first local calibration signal and the first local test signal corresponding to the position, and locate the first strain position of the test optical fiber according to the result of the cross-correlation calculation. Extended data segments are extracted from the calibration curve and the test curve corresponding to the first strain position, respectively. The calibration curve and the test curve corresponding to the extended data segment are synchronously slid-triggered based on the second window, and the obtained secondary signal segment is processed to obtain multiple second local calibration signals and second local test signals, wherein the width of the second window is smaller than the width of the first window; A cross-correlation operation is performed on the second local calibration signal and the second local test signal corresponding to the position, and the strain value of the test fiber at the corresponding position is determined based on the result of the cross-correlation operation.

2. The strain sensing demodulation method for optical frequency domain reflection according to claim 1, characterized in that, The device includes a main interferometer and an auxiliary interferometer, which both acquire probe laser light from the same linearly tunable laser. The steps of acquiring the detection signals of the calibration fiber and the fiber under test by the distributed optical fiber sensing device based on the optical frequency domain reflection include: The main interferometer acquires the detection signals of the calibration fiber and the fiber under test, respectively, and the auxiliary interferometer resamples the main interferometer signal of the detection signals to remove the influence of light source nonlinear noise in the detection signals.

3. The strain sensing demodulation method for optical frequency domain reflection according to claim 1, characterized in that, The step of converting the detection signal into a calibration curve and a test curve includes: Fast Fourier transform is performed on the detection signals corresponding to the calibration fiber and the fiber under test, respectively, to obtain the calibration distance domain information of the calibration fiber and the test distance domain information of the fiber under test. Based on the calibration distance domain information of the calibration fiber and the test distance domain information of the fiber under test, the calibration curve and the test curve are plotted respectively.

4. The strain sensing demodulation method for optical frequency domain reflection according to claim 3, characterized in that, The step of synchronously sliding and capturing the calibration curve and the test curve based on a first window, and processing the obtained preliminary signal segments to obtain multiple first local calibration signals and multiple first local test signals includes: Based on the first window, synchronous sliding interception is performed on the calibration curve and the test curve to obtain multiple first local calibration distance information and multiple first local test distance information; The first local calibration distance information and the first local measured distance information are respectively padded with zeros at the ends and subjected to inverse fast Fourier transform to obtain the first local calibration wavelength signal and the first local measured wavelength signal; The average wavelength domain signals of the first local calibration wavelength signal and the first local test wavelength signal are removed respectively to obtain the first local calibration signal and the first local test signal.

5. The strain sensing demodulation method for optical frequency domain reflection according to claim 1, characterized in that, The step of locating the first strain position of the optical fiber under test based on the result of cross-correlation calculation includes: Based on the resolution requirements and system noise level of the optical frequency domain reflection system, the strain threshold is determined. The strain threshold is compared with the first peak offset obtained by cross-correlation calculation of the calibration fiber and the fiber under test at each position. Based on the comparison result, it is determined whether there is strain at the corresponding position and the first strain position is located based on the determination result.

6. The strain sensing demodulation method for optical frequency domain reflection according to claim 1, characterized in that, The step of performing cross-correlation calculations on the second local calibration signal and the second local test signal corresponding to the position, and determining the strain value of the fiber under test at the corresponding position based on the result of the cross-correlation calculation, includes: The second strain position is determined based on all the second peak offsets obtained by cross-correlation calculation of all the second local calibration signals and the second local test signals; Plot the spectral offset curves based on all the second peak offsets; The average value of all second peak offsets within the second strain position is obtained, and the difference between the average value of the second peak offsets and the average value of the spectral offset curve is calculated to obtain the strain value at the second strain position.

7. A distributed optical fiber sensing device based on optical frequency domain reflection, characterized in that, The apparatus for performing the strain sensing demodulation method for optical frequency domain reflection according to any one of claims 1 to 6, the apparatus comprising: A linearly tunable laser is used to provide probe laser light to the calibration fiber and the fiber under test; The main interferometer is used to transmit probe laser to the calibration fiber and the fiber under test and demodulate the probe signals transmitted back in the calibration fiber and the fiber under test. The acquisition card is used to receive and process the electrical signals demodulated by the main interferometer; The main interferometer includes a first beam splitter, a first circulator, a first coupler, a polarization beam splitter, and a main balanced photodetector. The first beam splitter transmits the probe laser from the linearly tunable laser to the first circulator and the first coupler, respectively. The first circulator transmits the probe laser to the fiber under test and the calibration fiber, and transmits the probe signal fed back from the fiber under test and the calibration fiber to the first coupler. The first coupler couples the probe laser and the probe signal into a beat frequency signal, and transmits the beat frequency signal to the polarization beam splitter. The polarization beam splitter eliminates the polarization fading noise in the beat frequency signal and transmits the beat frequency signal to the balanced photodetector. The main balanced photodetector converts the beat frequency signal into an electrical signal and transmits it to the acquisition card.

8. The distributed optical fiber sensing device for optical frequency domain reflection according to claim 7, characterized in that, The device further includes an auxiliary interferometer, which is used to remove the influence of nonlinear noise from the light source in the detection signal. The auxiliary interferometer includes a second circulator, a second coupler, an auxiliary balanced photodetector, a time-delay fiber, a first Faraday rotator, and a second Faraday rotator. The second circulator is used to transmit the detection laser to the second coupler. The second coupler is used to transmit the detection laser to the time-delay fiber, the first Faraday rotator, and the second Faraday rotator and to receive the reflected signal. The second coupler is also used to transmit the reflected signal to the second circulator and the auxiliary balanced photodetector, respectively. The second circulator is used to transmit the reflected signal to the auxiliary balanced photodetector. The auxiliary balanced photodetector is used to convert the reflected signal transmitted by the second circulator and the second coupler into an electrical signal and transmit it to the acquisition card.

9. A computer device, characterized in that, The method includes a memory and a processor, the memory being used to store at least one program, and the processor being used to load the at least one program to execute the strain sensing demodulation method for optical frequency domain reflection as described in any one of claims 1 to 6.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions for causing a computer to perform the strain sensing demodulation method for optical frequency domain reflection as described in any one of claims 1 to 6.

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