Distributed strain and temperature sensing apparatus and method based on chaotic laser rayleigh scattering

Abstract

The application belongs to the field of distributed optical fiber sensing detection, and discloses a distributed strain and temperature sensing device and method based on chaotic laser Rayleigh scattering. The device comprises a chaotic laser. Chaotic laser emitted by the chaotic laser enters a pulse modulator after an isolator, is modulated into pulsed laser, then enters a sensing optical fiber through a first optical circulator after a light amplifier and a polarization scrambler. Rayleigh scattering occurs along the sensing optical fiber, backward Rayleigh scattering light signals are output after returning to the first optical circulator, and are converted into electric signals by a photoelectric detector. The electric signals enter a data processing system after a data acquisition card. Quantitative measurement of strain is realized through linear relationship between cross-correlation frequency shift and strain or temperature. The application uses chaotic laser with low coherence state as detection light pulse, which can ensure wide measurement range under medium sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of distributed optical fiber sensing systems, specifically a distributed strain and temperature sensing device and method based on chaotic laser Rayleigh scattering, which can realize distributed sensing and measurement of strain and temperature information at the test location. Background Technology

[0002] Distributed fiber optic sensing technology uses optical fiber as the signal transmission and sensing medium. Compared with traditional sensors, optical fiber has advantages such as small size, high sensitivity, and strong resistance to electromagnetic interference. Therefore, fiber optic sensing technology has attracted attention since its emergence and has been widely used in defense, military, aerospace, metrology and testing fields.

[0003] Distributed fiber optic sensing systems mainly include three types: those based on Rayleigh scattering, those based on Raman scattering, and those based on Brillouin scattering. Among these, distributed fiber optic sensing systems based on Brillouin scattering (BOTDR, BOTDA) and Rayleigh scattering can measure strain and temperature information at different locations along the fiber optic cable, and can be applied in many practical applications (smart structures, smart buildings, smart bridges, etc.). However, depending on the specific requirements of the application scenario, the sensing system needs to achieve high-precision and high-resolution quantitative monitoring. The accuracy and resolution ultimately depend on the power of the scattered light and the sensing sensitivity coefficient. If a weak Brillouin scattered light is used, the sensing accuracy and resolution are generally poor. Distributed fiber optic sensors based on backscattering Rayleigh scattering, because they detect Rayleigh scattered signal light power more strongly than Brillouin scattered light light power, can achieve higher sensing resolution than Brillouin sensors. These advantages have led to the widespread application of Rayleigh scattering-based distributed sensing systems in some fields.

[0004] Traditional COTD systems typically use narrow-linewidth laser sources with strong coherence. The narrower the laser linewidth, the easier it is for the optical signal to interfere. Ultra-narrow linewidths in these systems provide strong coherence, making the interference effect more significant and thus improving system sensitivity. However, excessively high sensitivity means that static Rayleigh scattering spectra can only be accurately measured under experimental conditions, making them difficult to apply to engineering measurements. Secondly, the strain measurement range of a COTD is related to the wavelength scanning range of the light source. Based on known stress sensitivity, a measurement range of 1000 με requires a wavelength range of 1.2 nm. Traditional COTD systems, due to their use of highly coherent narrow-linewidth light sources, struggle to achieve strain measurements within this range. Chaotic lasers, as low-coherence light sources with controllable spectral bandwidth, can reduce the system sensitivity to a level acceptable for practical engineering environments when used in COTD systems. Simultaneously, the center wavelength of chaotic light sources can be adjusted to a range close to 5 nm, a characteristic that has the potential to expand the strain measurement range. Therefore, using chaotic light sources ensures that the COTD system achieves a wider measurement range with moderate sensitivity. Summary of the Invention

[0005] This invention overcomes the problem that the existing COTDR system has a narrow measurement range and is difficult to apply to engineering measurement. It provides a distributed strain temperature sensing device and method based on chaotic laser Rayleigh scattering to achieve a wide measurement range with moderate sensitivity.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a distributed strain temperature sensing device based on chaotic laser Rayleigh scattering, comprising: a chaotic laser, an isolator, a pulse modulator, an optical amplifier, a polarizer, a first optical circulator, a sensing fiber, a photodetector, a data acquisition card, and a data processing system.

[0007] The chaotic laser emitted by the chaotic laser is optically isolated by an isolator, then modulated into a pulsed laser by a pulse modulator, amplified by an optical amplifier, scrambled by a polarizer, and then enters the sensing fiber through a first optical circulator. Rayleigh scattering occurs along the sensing fiber, and the resulting backscattered Rayleigh light signal returns to the first optical circulator and is output. It is then converted into an electrical signal by the photodetector, and the electrical signal is converted into an A / D signal by a data acquisition card before entering the data processing system.

[0008] The data processing system is used to perform cross-correlation calculations on the Rayleigh scattering intensity at different laser frequencies at various locations under static conditions and the Rayleigh scattering intensity under measurement conditions, and to calculate the strain or temperature value at that location based on the spectral frequency shift corresponding to the maximum value of the cross-correlation calculation.

[0009] The chaotic laser includes:

[0010] The system comprises a semiconductor laser, a second optical circulator, a polarization controller, a variable optical attenuator, and a coupler. The single-frequency laser output from the semiconductor laser is split into two beams by the coupler after passing through the second optical circulator. One beam, after having its power and polarization state adjusted by the variable optical attenuator and the polarization controller respectively, returns to the semiconductor laser after passing through the second optical circulator, driving it into a chaotic state. The other beam outputs chaotic laser light as the output of the chaotic laser.

[0011] The coupler is an optical fiber coupler, and the semiconductor laser, the second optical circulator, the polarization controller, the variable optical attenuator, and the coupler are connected by single-mode optical fiber patch cords.

[0012] The semiconductor laser is a distributed feedback semiconductor laser.

[0013] The chaotic laser, isolator, pulse modulator, optical amplifier, polarizer, and first optical circulator are connected by single-mode fiber optic jumpers, and the first optical circulator is connected to the photodetector by a single-mode fiber optic jumper.

[0014] The calculation formula for temperature or strain by the data processing system is as follows:

[0015] Δλ=S ε Δε+S T ΔT;

[0016] Where Δλ represents the spectral shift, S ε and S T Let represent the stress sensitivity coefficient and temperature sensitivity coefficient, respectively, and Δε and ΔT represent the strain change and temperature change, respectively.

[0017] Furthermore, this invention also provides a distributed strain temperature sensing method based on chaotic laser Rayleigh scattering, implemented using the aforementioned device, comprising the following steps:

[0018] S1. First, under static conditions, the center wavelength of the chaotic laser is adjusted stepwise, and Rayleigh scattering signals of the incident pulse at various locations of the sensing fiber at different wavelengths are collected to obtain the three-dimensional scattering spectrum of Rayleigh scattering intensity as a function of distance and frequency, and it is saved as a reference.

[0019] S2. Then, in a real environment with stress or temperature effects, collect three-dimensional Rayleigh scattering spectra at various locations on the sensing fiber.

[0020] S3. Using the data processing system, perform cross-correlation between the static Rayleigh scattering spectrum at the corresponding location and the Rayleigh scattering spectrum under the actual environment, and calculate the strain or temperature value at that location based on the spectral frequency shift corresponding to the maximum value of the cross-correlation operation.

[0021] The calculation formula is:

[0022] Δλ=S ε Δε+S T ΔT;

[0023] Where Δλ represents the spectral shift, S ε and S T Let represent the stress sensitivity coefficient and temperature sensitivity coefficient, respectively, and Δε and ΔT represent the strain change and temperature change, respectively.

[0024] This invention provides a distributed strain-temperature sensing device and method based on chaotic laser Rayleigh scattering. It employs a chaotic laser with low coherence as the probe light pulse, ensuring a wide measurement range under moderate sensitivity conditions. This characteristic corresponds to the performance specifications of large-scale infrastructure health monitoring systems. The system acquires the backscattered Rayleigh signal generated along the fiber optic cable by the chaotic pulse light, and achieves quantitative strain measurement through the linear relationship between cross-correlation frequency shift and strain or temperature. Compared with existing distributed fiber optic sensing technologies, it has the following advantages:

[0025] 1. Compared with distributed fiber optic sensing systems based on Brillouin scattering, this invention utilizes the Rayleigh scattering effect in optical fibers for sensing. Since the Rayleigh scattering signal light power is stronger than the Brillouin scattering light power, and the temperature and strain coefficients that cause frequency changes due to temperature or strain are smaller, this invention can achieve higher sensing resolution and accuracy than Brillouin sensors, with the sensing resolution being two orders of magnitude higher.

[0026] 2. Compared with traditional COTDR technology, the light source used in this invention is a low-coherence chaotic light source. Compared with narrow-linewidth lasers, the use of low-coherence chaotic light ensures that the system can achieve wide stress range measurement under moderate sensitivity, overcoming the defects of existing COTDR systems, such as small measurement range and high sensitivity leading to inaccurate measurement of static Rayleigh scattering spectra.

[0027] 3. Chaotic lasers have the characteristics of adjustable coherence length and center frequency, and controllable spectral bandwidth. This invention uses a single feedback loop external cavity chaotic laser source to replace the narrow linewidth laser and its corresponding linear frequency modulation device in the traditional COTDR system, which makes the cost low, the structure simple, and the anti-interference ability strong and the noise tolerance high. Attached Figure Description

[0028] Figure 1 A schematic diagram of a distributed strain temperature sensing device based on chaotic laser Rayleigh scattering provided in an embodiment of the present invention;

[0029] In the diagram: 1-Semiconductor laser, 2-First optical circulator, 3-Polarization controller, 4-Variable optical attenuator, 5-Coupled, 6-Optical isolator, 7-Pulse modulator, 8-Optical amplifier, 9-Polarization scrambler, 10-Second optical circulator, 11-Sensing fiber, 12-Photodetector, 13-Data acquisition card, 14-Data processing system. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] like Figure 1 As shown, this embodiment of the invention provides a distributed strain temperature sensing device based on chaotic laser Rayleigh scattering, including: a chaotic laser, an isolator 6, a pulse modulator 7, an optical amplifier 8, a polarizer 9, a first optical circulator 10, a sensing fiber 11, a photodetector 12, a data acquisition card 13, and a data processing system 14.

[0033] The chaotic laser emitted by the chaotic laser is optically isolated by isolator 6, then modulated into a pulsed laser by pulse modulator 7, amplified by optical amplifier 8, and scrambled by polarizer 9 before entering sensing fiber 11 through first optical circulator 10. Rayleigh scattering occurs along sensing fiber 11, and the resulting backscattered Rayleigh light signal returns to first optical circulator 10 and is output and converted into an electrical signal by photodetector 12. The electrical signal is then converted into an A / D signal by data acquisition card 13 and enters data processing system 14. Data processing system 14 is used to perform cross-correlation calculations on the Rayleigh scattering intensity at different laser frequencies at various locations under static conditions and the Rayleigh scattering intensity under measurement conditions, and calculates the strain or temperature value at that location based on the spectral frequency shift corresponding to the maximum value of the cross-correlation calculation.

[0034] Specifically, in this embodiment, the chaotic laser includes: a semiconductor laser 1, a second optical circulator 2, a polarization controller 3, a variable optical attenuator 4, and a coupler 5. The single-frequency laser output from the semiconductor laser 1 is split into two beams by the coupler 5 after passing through the second optical circulator 2. One beam is adjusted by the variable optical attenuator 3 and the polarization controller 4 respectively, and then returns to the semiconductor laser 1 after passing through the second optical circulator 2 to drive it into a chaotic state. The other beam outputs chaotic laser as the output of the chaotic laser.

[0035] Specifically, in this embodiment, the coupler 5 is a 1×2 fiber optic coupler, and the semiconductor laser 1, the second optical circulator 2, the polarization controller 3, the variable optical attenuator 4, and the coupler 5 are connected by a single-mode fiber optic patch cord.

[0036] Specifically, in this embodiment, the semiconductor laser 1 is a distributed feedback semiconductor laser. The optical amplifier 8 is an erbium-doped fiber amplifier.

[0037] Specifically, in this embodiment, the emitting end of the semiconductor laser 1 is connected to the emitting end of the first optical circulator 2 via a single-mode fiber optic patch cord; the reflecting end of the first optical circulator 2 is connected to the incident end of the 1×2 fiber optic coupler 5 via a single-mode fiber optic patch cord; one emitting end of the 1×2 fiber optic coupler 5 is connected to the incident end of the variable optical attenuator 4 via a single-mode fiber optic patch cord; the emitting end of the variable optical attenuator 4 is connected to the incident end of the polarization controller 3 via a single-mode fiber optic patch cord; the emitting end of the polarization controller 3 is connected to the incident end of the first optical circulator 2 via a single-mode fiber optic patch cord; and the other emitting end of the 1×2 fiber optic coupler 5 is connected to the incident end of the optical isolator 6 via a single-mode fiber optic patch cord.

[0038] The output end of optical isolator 6 is connected to the input end of pulse modulator 7 via a single-mode fiber optic patch cord. The output end of pulse modulator 7 is connected to the input end of erbium-doped fiber amplifier 8 via a single-mode fiber optic patch cord. The output end of erbium-doped fiber amplifier 8 is connected to the input end of polarizer scrambler 9 via a single-mode fiber optic patch cord. The output end of polarizer 9 is connected to the input end of second optical circulator 10 via a single-mode fiber optic patch cord. The output end of second optical circulator 10 is connected to sensing fiber optic cable 11. The reflecting end of second optical circulator 10 is connected to the input end of photodetector 12 via a single-mode fiber optic patch cord. The output end of photodetector 12 is connected to the input end of data acquisition card 13 via a high-frequency cable. The output end of data acquisition card 13 is connected to data processing system 14.

[0039] The working principle of the sensing device in this embodiment is as follows.

[0040] (1) The single-frequency laser output from the distributed feedback semiconductor laser 1 without a built-in isolator is injected into a single feedback loop via the first optical circulator 2. The variable optical attenuator 3 and the polarization controller 4 adjust the power and polarization state of the feedback light, respectively, driving the semiconductor laser 1 into a chaotic state. By controlling the laser temperature control, optical feedback intensity, external cavity length, and polarization matching state, the chaotic state can be optimized, and the center wavelength and spectral bandwidth can be adjusted. The generated chaotic laser is output through the output terminal of the optical isolator 6.

[0041] (2) The chaotic light output from the optical isolator 6 is modulated into pulse light by the pulse modulator 7. Then, the power of the chaotic pulse light can be amplified to several watts by the erbium-doped fiber amplifier 8. Then, the polarization is scrambled by the polarizer 9 to reduce the influence of polarization noise. After that, the light pulse enters the sensing fiber 11 and Rayleigh scattering occurs along the fiber. The photodetector 12 converts the backscattered Rayleigh scattering light signal into an electrical signal. The electrical signal is converted into an A / D signal by the data acquisition card 13 and then enters the data processing system 14. Subsequently, the center wavelength of the chaotic laser is adjusted stepwise to obtain the Rayleigh scattering spectrum at different wavelengths. By processing and analyzing the acquired data, the strain and temperature information at the location where the chaotic light pulse signal is subjected to Rayleigh scattering in the sensing fiber can be obtained.

[0042] If a light pulse with a pulse width of W and a frequency of v is injected from the beginning of the sensing fiber 11, the optical power of the backscattered Rayleigh signal received at the beginning of the fiber after time t is given by the following formula:

[0043]

[0044] Where m and n represent any two scattering points within the fiber segment containing the pulse, v is the frequency of the optical pulse, and a m and a n τ represents the amplitude of the backscattered Rayleigh signal at scattering points m and n. m and τ n Let represent the time delay of the backscattered Rayleigh signals at scattering points m and n. The time difference between the backscattered Rayleigh signals at any two scattering points is:

[0045] τ n -τ m =2L nm n f / c; (2)

[0046] Where L nm Let m be the distance between scattering point m and scattering point n, and n be the distance between scattering point m and scattering point n. f Let be the refractive index of the optical fiber, and c be the speed of light in a vacuum. Because the refractive index of the optical fiber and the distance between the scattering points change with the external strain and temperature of the fiber, the time difference τ between any two scattering points will vary. n -τ m As the temperature or strain changes, the light power will also change, as shown in equation (1). Since the light source frequency and time difference are multiplicative, it can be seen that by adjusting the light source to change its frequency by Δv, the received scattered light power will be equal to that before the temperature or strain change. Substituting equation (2) into equation (1), it can be seen that if the scattered light power is equal before and after the temperature or strain change, Δv must satisfy the following equation:

[0047] v0L nm (T0,ε0)nf (T0,ε0) / c=(v0+Δv)L nm (T,ε)n f (T,ε) / c; (3)

[0048] Therefore, according to equation (3), we have:

[0049] Δv≈-v0(1+C ε )Δε-v0(ρ T +C T )ΔT; (4)

[0050] Where v0 is the frequency of the light source before the strain change, and C ε and C T For Rayleigh-related strain and temperature coefficients, ρ T The coefficient of thermal expansion of the optical fiber material is used, and the distance L between scattering points is compensated by the change in the light source frequency. nm and refractive index n f The change in frequency shift of the backscattered Rayleigh signal is approximately linearly related to strain and temperature, as shown in the above analysis. Therefore, distributed quantitative sensing of strain and temperature can be achieved by judging the change in frequency shift. The magnitude of the frequency shift at a certain point in the optical fiber can be obtained by cross-correlation calculation between the Rayleigh scattering signal spectrum at that location and the Rayleigh scattering signal spectrum at the same location under static conditions.

[0051] In summary, in this embodiment, the calculation formula for temperature or strain by the data processing system is as follows:

[0052] Δλ=S ε Δε+S T ΔT; (5)

[0053] Where Δλ represents the wavelength offset, S ε and S T Let S represent the stress sensitivity coefficient and temperature sensitivity coefficient, respectively, and Δε and ΔT represent the strain change and temperature change, respectively. The stress sensitivity coefficient S... ε and temperature sensitivity coefficient S T The linear relationship between temperature or strain and frequency shift can be obtained experimentally and then calculated. For example, by applying a known temperature or strain to the fiber stepper and measuring the corresponding wavelength shift, the linear relationship between temperature or strain and wavelength shift can be obtained, and thus the temperature or strain coefficient can be obtained.

[0054] Example 2

[0055] Embodiment 2 of the present invention provides a distributed strain temperature sensing method based on chaotic laser Rayleigh scattering, implemented using the device described in Embodiment 1, and includes the following steps:

[0056] S1. First, under static conditions, the center wavelength of the chaotic laser is adjusted stepwise, and Rayleigh scattering signals of the incident pulse at various locations on the sensing fiber at different wavelengths are collected to obtain the three-dimensional scattering spectrum of Rayleigh scattering intensity as a function of distance and frequency, and this spectrum is saved as a reference.

[0057] S2. Then, in a real environment with stress or temperature effects, Rayleigh scattering spectra at various locations on the sensing fiber are collected in the same steps as in S1. During measurement, by stepping and adjusting the center wavelength of the chaotic laser, Rayleigh scattering signals of the incident pulse at different wavelengths at various locations on the sensing fiber can be collected, thus obtaining a three-dimensional scattering spectrum of Rayleigh scattering intensity distribution with distance and frequency in the real environment.

[0058] S3. Using the data processing system 14, perform cross-correlation between the Rayleigh scattering spectrum under static conditions and the Rayleigh scattering spectrum under actual conditions at the corresponding location, and calculate the strain or temperature value at that location based on the spectral frequency shift corresponding to the maximum value of the cross-correlation operation. The calculation formula is the above formula (5).

[0059] Cross-correlation is performed between the Rayleigh scattering spectra under static conditions and those under actual environmental conditions at corresponding locations. If the temperature or strain remains unchanged compared to the static conditions, the cross-correlation function reaches its maximum value at no frequency shift. If the temperature or strain changes, the cross-correlation function reaches its maximum value at a frequency shift Δv. Therefore, the frequency shift compensation required for temperature or strain changes at each location can be obtained through cross-correlation. Considering the known stress sensitivity coefficient S... ε =1.2pm / με and temperature coefficient S T When the temperature is 10.8 pm / ℃, the strain change or temperature change can be calculated using equation (5).

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A distributed strain-temperature sensing device based on chaotic laser Rayleigh scattering, characterized in that, include: Chaotic laser, isolator (6), pulse modulator (7), optical amplifier (8), polarizer (9), first optical circulator (10), sensing fiber (11), photodetector (12), data acquisition card (13) and data processing system (14). The chaotic laser emitted by the chaotic laser is optically isolated by the isolator (6), then modulated into a pulse laser by the pulse modulator (7), and then amplified by the optical amplifier (8). After being scrambled by the polarizer (9), it enters the sensing fiber (11) through the first optical circulator (10). Rayleigh scattering occurs along the sensing fiber (11), and the generated backscattered Rayleigh light signal returns to the first optical circulator (10) and is output and converted into an electrical signal by the photodetector (12). The electrical signal is then converted into an A / D signal by the data acquisition card (13) and enters the data processing system (14). The data processing system (14) is used to perform cross-correlation calculations on the Rayleigh scattering intensity at different laser frequencies at various locations under static conditions and the Rayleigh scattering intensity under measurement conditions, and to calculate the strain or temperature value at the location based on the spectral frequency shift corresponding to the maximum value of the cross-correlation calculation. The Rayleigh scattering intensity at different laser frequencies is obtained by step-adjusting the center wavelength of the chaotic laser. The chaotic laser, isolator (6), pulse modulator (7), optical amplifier (8), polarizer (9), and first optical circulator (10) are connected by single-mode fiber optic jumpers, and the first optical circulator (10) and photodetector (12) are connected by single-mode fiber optic jumpers.

2. The distributed strain temperature sensing device based on chaotic laser Rayleigh scattering according to claim 1, characterized in that, The chaotic laser includes: The semiconductor laser (1), the second optical circulator (2), the polarization controller (3), the variable optical attenuator (4), and the coupler (5) are used to split the single-frequency laser output by the semiconductor laser (1) into two beams after passing through the second optical circulator (2). One beam is adjusted by the variable optical attenuator (4) and the polarization controller (3) to adjust the power and polarization state of the light, and then returns to the semiconductor laser (1) after passing through the second optical circulator (2) to drive it into a chaotic state. The other beam outputs chaotic laser as the output of the chaotic laser.

3. The distributed strain temperature sensing device based on chaotic laser Rayleigh scattering according to claim 2, characterized in that, The coupler (5) is a 1×2 fiber coupler, and the semiconductor laser (1), the second optical circulator (2), the polarization controller (3), the variable optical attenuator (4), and the coupler (5) are connected by a single-mode fiber jumper.

4. The distributed strain temperature sensing device based on chaotic laser Rayleigh scattering according to claim 2, characterized in that, The semiconductor laser (1) is a distributed feedback semiconductor laser.

5. The distributed strain temperature sensing device based on chaotic laser Rayleigh scattering according to claim 1, characterized in that, The calculation formula for temperature or strain by the data processing system is as follows: ； in, Indicates spectral shift. and These represent the stress sensitivity coefficient and the temperature sensitivity coefficient, respectively. and These represent strain change and temperature change, respectively.

6. A distributed strain-temperature sensing method based on chaotic laser Rayleigh scattering, implemented using the device described in claim 1, characterized in that, Includes the following steps: S1. First, under static conditions, the center wavelength of the chaotic laser is adjusted stepwise, and Rayleigh scattering signals of the incident pulse at various locations of the sensing fiber at different wavelengths are collected to obtain the three-dimensional scattering spectrum of Rayleigh scattering intensity as a function of distance and frequency, and it is saved as a reference. S2. Then, in a real environment with stress or temperature effects, collect three-dimensional Rayleigh scattering spectra at various locations on the sensing fiber. S3. Using the data processing system (14), perform cross-correlation between the static Rayleigh scattering spectrum at the corresponding location and the Rayleigh scattering spectrum under the actual environment, and calculate the strain or temperature value at the location based on the spectral frequency shift corresponding to the maximum value of the cross-correlation operation.

7. The distributed strain temperature sensing method based on chaotic laser Rayleigh scattering according to claim 6, characterized in that, The calculation formula is: ； in, Indicates spectral shift. and These represent the stress sensitivity coefficient and the temperature sensitivity coefficient, respectively. and These represent strain change and temperature change, respectively.

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