Chaotic BOTDA double-parameter high-precision sensing device and method fused with Raman scattering

Abstract

The invention relates to the field of distributed optical fiber sensing, and discloses a chaos BOTDA (Brillouin Optical Time Domain Analysis) double-parameter high-precision sensing device and method fused with Raman scattering. In the device, laser output by a narrow linewidth laser is subjected to double-sideband modulation and then enters one end of a sensing optical fiber as detection light; chaos laser output by the broadband chaos laser source is divided into two paths after pulse modulation, and one path serves as pump light and enters the other end of the sensing optical fiber; a Raman scattering light signal generated by spontaneous Raman scattering of the pump light in the sensing optical fiber and the other path of reference light are detected by an avalanche photodetector and then are emitted to a data acquisition and analysis system to obtain temperature distribution along the line, and the chaos pump light and the detection light which are propagated in opposite directions generate stimulated Brillouin scattering in the sensing optical fiber; after being detected by a photoelectric detector, the Brillouin signals are sent to a data acquisition and analysis system to obtain Brillouin signals, and strain distribution is obtained by combining temperature distribution demodulation. According to the invention, high-precision cross-free demodulation of temperature and strain can be realized.

Description

Technical Field

[0001] This invention relates to the field of distributed optical fiber sensing, specifically to a chaotic BOTDA dual-parameter high-precision sensing device and method that integrates Raman scattering. Background Technology

[0002] In recent years, BOTDA sensing technology based on stimulated Brillouin scattering (BBS) has become an important technical means for the full life-cycle safety monitoring of large-scale infrastructure facilities such as oil and gas pipelines, high-voltage power grids, and civil engineering buildings, thanks to its advantages of long sensing distance, high measurement accuracy, and distributed monitoring capabilities. It has been widely applied in scenarios such as leak early warning, deformation monitoring, and condition assessment. However, the sensitivity of stimulated Brillouin scattering light signals in optical fibers to the coupling of temperature and strain information makes it challenging to achieve cross-sensitive temperature and strain measurements based on BOTDA technology.

[0003] To address this, researchers have proposed solutions such as special optical fibers, Raman / Rayleigh scattering-assisted demodulation, and artificial neural network demodulation. Utilizing the sensitivity differences of Brillouin scattering in special optical fibers to temperature and stress, the University of Pittsburgh achieved 1-m spatial resolution measurements over a 20-m sensing distance using dual-core optical fibers, with average errors of 0.24% and 3.7% for temperature and strain, respectively (Sensors, 2018, 18(4): 1176). The University of Pisa, Italy, proposed a distributed optical fiber sensor scheme using cyclic pulse coding and single-pulse hybrid Raman / Brillouin optical temporal domain analysis, achieving meter-level spatial resolution simultaneous sensing of dual parameters over a 10 km sensing fiber, with measurement resolutions of 3.4 ℃ and 80 με for temperature and strain, respectively (Optics Letters, 2013, 38(20): 4162-4165). Dalian University of Technology combined stimulated Brillouin scattering and Rayleigh scattering techniques to achieve a spatial resolution of 50 cm at a sensing distance of 92 m, with measurement accuracies of 1.2 ℃ and 15 με for temperature and strain, respectively (Sensors, 2013, 13(2):1836-1845). Hong Kong Polytechnic University proposed a scheme using deep neural network technology to simultaneously measure temperature and strain, achieving a spatial resolution of 2 m in a 24 km long LEAF, with a standard deviation of 2.4 ℃ / 66.2 με for temperature / strain (OpticsExpress, 2019, 27(3): 2530-2543).

[0004] In summary, although some solutions can achieve dual-parameter sensing of temperature and strain information, the research and fabrication costs of special optical fibers are high in the early stages, and the connection and coupling are difficult. The Raman / Rayleigh scattering-assisted demodulation scheme suffers from the problem of mutual constraints between sensing distance and measurement accuracy. The artificial neural network demodulation scheme requires the creation of a large number of simulation and experimental datasets in the early stages of measurement, and the training time is long. Therefore, a new sensing device is needed to achieve accurate dual-parameter sensing of temperature and strain information. Summary of the Invention

[0005] To address the challenges of existing BOTDA systems based on stimulated Brillouin scattering, such as the difficulty in balancing long-distance and high-precision measurement, and the cross-sensitivity to temperature and strain, this invention proposes a high-precision dual-parameter sensing device and method for chaotic BOTDA that integrates Raman scattering. This method improves the system's sensing distance and demodulation accuracy while enabling cross-sensitivity measurement of both temperature and strain.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a high-precision dual-parameter chaotic BOTDA sensing device that integrates Raman scattering, comprising a narrow linewidth laser, a broadband chaotic laser source, a sensing fiber, a first optical circulator, a photodetector, an avalanche photodetector, and a data acquisition and analysis system. The narrow linewidth laser output from the narrow linewidth laser is modulated by a double-sideband and enters one end of the sensing fiber as the probe light; the chaotic laser output from the broadband chaotic laser source is pulse-modulated and split into two paths, one as the reference light and the other as the pump light, which enters the other end of the sensing fiber through the first optical circulator. The Raman scattered light signal generated by the spontaneous Raman scattering of the pump light in the sensing fiber is output by the first optical circulator and, together with the reference light, is photoelectrically converted by the avalanche photodetector and transmitted to the data acquisition and analysis system. Simultaneously, the chaotic pump light and probe light propagating in opposite directions undergo stimulated Brillouin scattering in the sensing fiber. The amplified probe light is output through the first optical circulator, undergoes photoelectric conversion by the photodetector, and is then sent to the data acquisition and analysis system to obtain the Brillouin signal. The data acquisition and analysis system is used to demodulate the temperature distribution along the sensing fiber based on the Raman scattered light signal and the reference light signal; it is also used to demodulate the strain distribution along the sensing fiber based on the Brillouin signal detected by the photodetector and the temperature distribution, thereby achieving cross-demodulation of temperature and strain.

[0007] The aforementioned chaotic BOTDA dual-parameter high-precision sensing device incorporating Raman scattering further includes an electro-optic modulator, a first erbium-doped fiber amplifier, a polarization scrambler, an optical isolator, a semiconductor optical amplifier, a second erbium-doped fiber amplifier, a first fiber coupler, a first optical circulator, a wavelength division multiplexer, and a second fiber coupler. The narrow linewidth laser output from the narrow linewidth laser is modulated on both sides by an electro-optic modulator, amplified by a first erbium-doped fiber amplifier, and then enters one end of the sensing fiber as probe light after passing through a polarizer and an optical isolator. The chaotic laser output from the broadband chaotic laser source is pulse-modulated by a semiconductor optical amplifier. The pulse-modulated chaotic laser is amplified by a second erbium-doped fiber amplifier and then split into two paths by a first fiber coupler. One path is used as a reference light and incident on the second fiber coupler, while the other path is used as a pump light and enters the other end of the sensing fiber through a first optical circulator. The pump light undergoes spontaneous Raman scattering in the optical fiber. The Raman scattered light signal is output through the first optical circulator and wavelength division multiplexer, and then incident on the second optical fiber coupler together with the reference light. The Raman scattered light signal and the reference light are coupled through the second optical fiber coupler, and the signal is photoelectrically converted by the avalanche photodetector and transmitted to the data acquisition and analysis system. The chaotic pump light and probe light propagating in opposite directions undergo stimulated Brillouin scattering in the sensing fiber. The amplified probe light is output through the first optical circulator and wavelength division multiplexer. One of the sidebands is filtered out by the filter and then enters the photodetector for photoelectric conversion before being sent to the data acquisition and analysis system.

[0008] The broadband chaotic laser source includes a distributed feedback semiconductor laser, a second optical circulator, a third fiber coupler, a third erbium-doped fiber amplifier, a fiber polarization controller, and an optical attenuator. The distributed feedback semiconductor laser has no built-in isolator. Its output laser enters the third fiber coupler after passing through the second optical circulator. The light output from the first output end of the third fiber coupler passes through the third erbium-doped fiber amplifier, the fiber polarization controller, and the optical attenuator, then returns through the second optical circulator and enters the distributed feedback semiconductor laser, causing disturbance and causing it to output broadband chaotic laser light. The broadband chaotic laser light is output from the second output end of the third fiber coupler.

[0009] The filter includes a third optical circulator and a fiber Bragg grating. The amplified probe light is output through the first optical circulator and wavelength division multiplexer, then enters the fiber Bragg grating through the third optical circulator. One of the sidebands is filtered out by the fiber Bragg grating, and then returns to the third optical circulator and enters the photodetector.

[0010] The aforementioned chaotic BOTDA dual-parameter high-precision sensing device with Raman scattering integrates Raman scattering. The Raman scattered light signal generated by the spontaneous Raman scattering of the pump light in the sensing fiber is output as a Raman anti-Stokes light signal after passing through a first optical circulator and a wavelength division multiplexer.

[0011] The first, second, and third fiber optic couplers are all 1×2 fiber optic couplers.

[0012] The aforementioned chaotic BOTDA dual-parameter high-precision sensing device integrating Raman scattering further includes a microwave signal generator, a bias controller, and the signal output terminal of the microwave signal generator is connected to the microwave signal input terminal of the high-speed electro-optic modulator; the signal output terminal of the bias controller is connected to the bias input terminal of the high-speed electro-optic modulator.

[0013] The data acquisition and analysis system is used to obtain the temperature distribution along the sensing fiber by performing correlation demodulation based on the Raman scattered light signal and the reference light signal.

[0014] The narrow linewidth laser and the broadband chaotic laser source both have a wavelength of 1550nm. The 1550nm / 1450nm channel of the wavelength division multiplexer is connected to the output of the first optical circulator, the 1450nm channel is connected to the second fiber coupler, and the 1550nm channel is connected to the filter.

[0015] Furthermore, this invention also provides a high-precision dual-parameter sensing method for chaotic BOTDA based on Raman scattering, implemented using the aforementioned high-precision dual-parameter sensing device for chaotic BOTDA based on Raman scattering, comprising the following steps: Step 1: Acquire the reference optical signal and the Raman scattered optical signal along the sensing fiber, and perform relevant demodulation calculations to obtain the temperature distribution along the sensing fiber; Step 2: Acquire the Brillouin signal along the sensing fiber and, in conjunction with the temperature distribution, perform temperature calibration on the strain distribution along the demodulated sensing fiber 8.

[0016] The present invention discloses a high-precision dual-parameter chaotic BOTDA sensing device and method incorporating Raman scattering, which has advantages and positive effects compared with existing BOTDA sensing systems. 1. Compared to existing single-narrow-linewidth laser source BOTDA technology, this invention provides the probe and pump light sources in the BOTDA system from two independent light sources. The probe light source remains a conventional narrow-linewidth laser, while the pump light source is replaced by a broadband chaotic laser generated by an active optical feedback structure. Because the pump light is a broadband chaotic laser, the probe light at each scanning frequency point during stimulated Brillouin gain in the fiber will obtain a wider range of gain. Therefore, the gain intensity will be improved across the entire gain spectrum, effectively enhancing the sensing range and measurement accuracy of the BOTDA system.

[0017] 2. Compared with existing BOTDA technology, this invention replaces the narrow-linewidth pump light, which originates from the same source as the probe light, with a broadband chaotic laser. On the one hand, the broadband gain characteristics of the broadband chaotic pump light on the probe light are used to further enhance the sensing distance and measurement accuracy of the BOTDA system. On the other hand, a chaotic Raman sensing system is constructed by exciting Raman scattered light signals in the sensing fiber using chaotic pump pulses. Based on the high correlation between the incident chaotic laser and the chaotic Raman scattered light excited in the fiber, temperature localization and demodulation with high spatial resolution up to millimeters can be achieved. At the same time, by combining the Raman sensing system with the Brillouin sensing system, which is sensitive only to temperature information along the fiber, the problem of cross-sensitivity between temperature and strain measurements in BOTDA sensing systems can be solved.

[0018] 3. Compared with existing temperature / strain dual-parameter sensing systems, this invention achieves efficient fusion of Brillouin and Raman dual-scattering sensing systems by introducing broadband chaotic laser into the pump path of the BOTDA system. While effectively improving the system's sensing distance and measurement accuracy, it can simultaneously achieve cross-sensitivity-free demodulation of temperature and strain along the optical fiber. Attached Figure Description

[0019] Figure 1 A schematic diagram of the structure of a chaotic BOTDA dual-parameter high-precision sensing device that integrates Raman scattering is provided in an embodiment of the present invention; Figure 2 A schematic diagram illustrating the principle of stimulated Brillouin scattering broadband gain between narrow-linewidth probe light and broadband chaotic pump light within the sensing fiber in this embodiment of the invention.

[0020] In the diagram: 1. Narrow linewidth laser; 2. High-speed electro-optic modulator; 3. Microwave signal generator; 4. Bias controller; 5. First erbium-doped fiber amplifier; 6. Polarizer; 7. Optical isolator; 8. Sensing fiber; 9. Distributed feedback semiconductor laser; 10. Second optical circulator; 11. Third fiber coupler; 12. Third erbium-doped fiber amplifier; 13. Fiber polarization controller; 14. Optical attenuator; 15. Semiconductor optical amplifier; 16. Second erbium-doped fiber amplifier; 17. First fiber coupler; 18. First optical circulator; 19. Wavelength division multiplexer; 20. Third optical circulator; 21. Fiber Bragg grating; 22. Second fiber coupler; 23. Avalanche photodetector; 24. Photodetector; 25. Data acquisition and analysis system. Detailed Implementation

[0021] 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.

[0022] Example 1 like Figure 1 As shown, Embodiment 1 of the present invention provides a high-precision dual-parameter chaotic BOTDA sensing device incorporating Raman scattering, comprising a narrow-linewidth laser 1, a broadband chaotic laser source, a sensing fiber 8, a first optical circulator 18, a photodetector 24, an avalanche photodetector 23, and a data acquisition and analysis system 25; the narrow-linewidth laser output from the narrow-linewidth laser 1 is modulated by a double-sideband and enters one end of the sensing fiber 8 as the probe light; the chaotic laser output from the broadband chaotic laser source is pulse-modulated and split into two paths, one as a reference light and the other as a pump light. The first optical circulator 18 enters the other end of the sensing fiber 8; the Raman scattered light signal generated by the spontaneous Raman scattering of the pump light in the fiber is output by the first optical circulator 18 and, together with the reference light, is photoelectrically converted by the avalanche photodetector and transmitted to the data acquisition and analysis system; at the same time, the chaotic pump light and the probe light propagating in opposite directions undergo stimulated Brillouin scattering in the sensing fiber 8, and the amplified probe light is output by the first optical circulator 18, photoelectrically converted by the photodetector 24, and then sent to the data acquisition and analysis system 25 to obtain the Brillouin signal.

[0023] The data acquisition and analysis system 25 is used to demodulate the temperature distribution along the sensing fiber 8 based on the Raman scattered light signal and the reference light signal; it is also used to demodulate the strain distribution along the sensing fiber 8 based on the Brillouin signal detected by the photodetector 24 and the temperature distribution, thereby achieving cross-demodulation of temperature and strain.

[0024] Furthermore, the chaotic BOTDA dual-parameter high-precision sensing device integrating Raman scattering in this embodiment also includes an electro-optic modulator 2, a first erbium-doped fiber amplifier 5, a polarization scrambler 6, an optical isolator 7, a semiconductor optical amplifier 15, a second erbium-doped fiber amplifier 16, a first fiber coupler 17, a first optical circulator 18, a wavelength division multiplexer 19, and a second fiber coupler 22.

[0025] Specifically, the narrow-linewidth laser output from the narrow-linewidth laser 1 is modulated by the electro-optic modulator 2 on both sides, amplified by the first erbium-doped fiber amplifier 5, and then enters one end of the sensing fiber 8 as probe light after passing through the polarizer 6 and the optical isolator 7; the chaotic laser output from the broadband chaotic laser source is pulse-modulated by the semiconductor optical amplifier 15, and the pulse-modulated chaotic laser is amplified by the second erbium-doped fiber amplifier 16 and then split into two paths by the first fiber coupler 17. One path is used as reference light and incident on the second fiber coupler 22, and the other path is used as pump light and enters the other end of the sensing fiber 8 through the first optical circulator 18.

[0026] The pump light undergoes spontaneous Raman scattering in the optical fiber. The resulting Raman scattered light signal is output through the first optical circulator 18 and wavelength division multiplexer 19, and then incident on the second optical fiber coupler 22 together with the reference light. The light signal after passing through the second optical fiber coupler 22 and the reference light is photoelectrically converted by the avalanche photodetector 23 and then transmitted to the data acquisition and analysis system 25.

[0027] The chaotic pump light and probe light propagating in opposite directions undergo stimulated Brillouin scattering in the sensing fiber 8. The amplified probe light is output through the first optical circulator 18 and wavelength division multiplexer 19. One of the sidebands is filtered out by the filter and then enters the photodetector 24 for photoelectric conversion before being sent to the data acquisition and analysis system 25.

[0028] Furthermore, such as Figure 1 As shown, in this embodiment, the broadband chaotic laser source includes a distributed feedback semiconductor laser 9, a second optical circulator 10, a third fiber coupler 11, a third erbium-doped fiber amplifier 12, a fiber polarization controller 13, and an optical attenuator 14. The distributed feedback semiconductor laser 9 has no built-in isolator. Its output laser enters the third fiber coupler 11 after passing through the second optical circulator 10. The light output from the first output end of the third fiber coupler 11 passes through the third erbium-doped fiber amplifier 12, the fiber polarization controller 13, and the optical attenuator 14, and then returns through the second optical circulator 10 and enters the distributed feedback semiconductor laser 9, causing disturbance and causing it to output broadband chaotic laser. The broadband chaotic laser is output from the second output end of the third fiber coupler 11.

[0029] Specifically, in this embodiment, the narrow linewidth laser 1 is a semiconductor laser with a linewidth of 20 kHz. The electro-optic modulator 2 is a high-speed electro-optic modulator with a modulation bandwidth of 0.01~22.3 GHz.

[0030] Specifically, in this embodiment, the output end of the narrow linewidth laser 1 is connected to the input end of the electro-optic modulator 2; the output end of the high-speed electro-optic modulator 2 is connected to the input end of the first erbium-doped fiber amplifier 5 via a single-mode fiber jumper; the output end of the first erbium-doped fiber amplifier 5 is connected to the input end of the polarizer 6 via a single-mode fiber jumper; the output end of the polarizer 6 is connected to the output end of the optical isolator 7 via a single-mode fiber jumper; the output end of the optical isolator 7 is connected to one end of the sensing fiber 8 via a single-mode fiber jumper; and the other end of the sensing fiber 8 is connected to the reflecting end of the first optical circulator 18 via a single-mode fiber jumper.

[0031] Specifically, in this embodiment, the output end of the distributed feedback semiconductor laser 9 is connected to the reflecting end of the second optical circulator 10; the output end of the second optical circulator 10 is connected to the input end of the third optical fiber coupler 11 via a single-mode optical fiber; the first output end of the third optical fiber coupler 11 is connected to the input end of the third erbium-doped fiber amplifier 12 via a single-mode optical fiber jumper; the output end of the third erbium-doped fiber amplifier 12 is connected to the input end of the fiber polarization controller 13 via a single-mode optical fiber jumper; the output end of the fiber polarization controller 13 is connected to the input end of the optical attenuator 14 via a single-mode optical fiber jumper; and the output end of the optical attenuator 14 is connected to the input end of the second optical circulator 10 via a single-mode optical fiber jumper.

[0032] Specifically, in this embodiment, the second output of the third fiber coupler 11 is connected to the input of the semiconductor optical amplifier 15 via a single-mode fiber optic patch cord; the output of the semiconductor optical amplifier 15 is connected to the input of the second erbium-doped fiber amplifier 16 via a single-mode fiber optic patch cord; the output of the second erbium-doped fiber amplifier 16 is connected to the input of the first fiber coupler 17 via a single-mode fiber optic patch cord; the first output of the first fiber coupler 17 is connected to the input of the first optical circulator 18 via a single-mode fiber optic patch cord; the output of the first optical circulator 18 is connected to the input of the wavelength division multiplexer 19; the first output of the wavelength division multiplexer 19 is connected to the first input of the second fiber coupler 22 via a single-mode fiber optic patch cord; the second output of the first fiber coupler 17 is connected to the second input of the second fiber coupler 22 via a single-mode fiber optic patch cord; the output of the second fiber coupler 22 is connected to the input of the avalanche photodetector 23 via a single-mode fiber optic patch cord; and the output of the avalanche photodetector 23 is connected to the first input of the data acquisition and analysis system 25.

[0033] Furthermore, in this embodiment, the filter includes a third optical circulator 20 and a fiber Bragg grating 21. The amplified probe light is output through the first optical circulator 18 and the wavelength division multiplexer 19, and then enters the fiber Bragg grating 21 through the third optical circulator 20. One sideband is filtered out by the fiber Bragg grating 21, which can be a low-frequency sideband. The single sideband obtained after filtering returns to the third optical circulator 20 and enters the photodetector 24.

[0034] Specifically, in this embodiment, the second output of wavelength division multiplexer 19 is connected to the input of third optical circulator 20 via a single-mode fiber optic patch cord; the output of fiber Bragg grating 21 is connected to the reflector of third optical circulator 20 via a single-mode fiber optic patch cord; the output of third optical circulator 20 is connected to the input of photodetector 24 via a single-mode fiber optic patch cord; and the output of photodetector 24 is connected to the second input of data acquisition and analysis system 25.

[0035] Specifically, in this embodiment, the data acquisition and analysis system 25 is used to obtain the temperature distribution along the sensing fiber 8 by performing autocorrelation demodulation based on the beat frequency signal between the Raman scattered light signal and the reference light signal. In this embodiment, a chaotic Raman sensing system is constructed by exciting Raman scattered light signals in the sensing fiber 8 with chaotic pump pulse light. Based on the high correlation characteristics between the incident chaotic laser (reference light) and the chaotic Raman scattered light excited in the sensing fiber by the chaotic pump pulse light, high spatial resolution temperature localization and demodulation up to millimeter level is achieved. High spatial resolution temperature demodulation is performed based on the changes in the correlation peaks of the two optical signals, ultimately achieving efficient fusion of the Brillouin and Raman systems and cross-free demodulation of temperature strain.

[0036] Specifically, in this embodiment, the generated Raman scattered light signal is output as a Raman anti-Stokes light signal after passing through the first optical circulator 18 and the wavelength division multiplexer 19. High-precision temperature distribution along the sensing fiber 8 can be obtained through correlation demodulation of the Raman anti-Stokes light signal and the reference light signal.

[0037] Specifically, in this embodiment, the wavelengths of the narrow linewidth laser 1 and the broadband chaotic laser source are both 1550nm. The input of the wavelength division multiplexer 19 is a 1550nm / 1450nm channel, which is connected to the output of the first optical circulator 18. The first output is a 1450nm channel, which is connected to the second fiber coupler 22. The second output is a 1550nm channel, which is connected to the filter.

[0038] Specifically, in this embodiment, the data acquisition and analysis system is used to obtain the temperature distribution along the sensing fiber 8 by performing correlation demodulation based on the Raman scattered light signal and the reference light signal; it is also used to obtain the strain distribution along the sensing fiber 8 by demodulating the Brillouin signal detected by the photodetector 24 and combining it with the temperature distribution, so as to finally realize dual-parameter sensing of temperature and strain that balances long sensing distance and high measurement accuracy.

[0039] Furthermore, in this embodiment, the first fiber optic coupler 17, the second fiber optic coupler 22, and the third fiber optic coupler 11 are all 1×2 fiber optic couplers.

[0040] Furthermore, this embodiment also includes a microwave signal generator 3, a bias controller 4, and the signal output terminal of the microwave signal generator 3 is connected to the microwave signal input terminal of the high-speed electro-optic modulator 2; the signal output terminal of the bias controller 4 is connected to the bias input terminal of the high-speed electro-optic modulator 2.

[0041] like Figure 2 As shown, when the pump light of the same origin with narrow linewidth acts in the sensing fiber, the gain of the probe light is a single-frequency gain due to the narrow linewidth limitation of the pump light, and its gain effect is limited. When the broadband chaotic light in this application is used as the pump light, the broadband gain effect of the pump light can greatly increase the gain of the Brillouin signal and improve the signal-to-noise ratio of the system.

[0042] Example 2 Embodiment 2 of the present invention provides a high-precision dual-parameter sensing method for chaotic BOTDA based on Raman scattering, which is implemented based on the high-precision dual-parameter sensing device for chaotic BOTDA based on Raman scattering described in Embodiment 1, and includes the following steps: Step 1: Acquire the reference optical signal and the Raman scattered optical signal along the sensing fiber 8, and demodulate and calculate the temperature distribution along the sensing fiber 8. Step 2: Acquire the Brillouin signal along the sensing fiber 8, and combine it with the temperature distribution to perform temperature calibration on the strain distribution along the demodulated sensing fiber 8.

[0043] Specifically, in this embodiment, by measuring the Raman scattered light signal and the reference light signal, the temperature distribution along the sensing fiber 8 is obtained through correlation demodulation calculation. This allows for temperature correction of the strain distribution obtained by combining the Brillouin signal, thus solving the problems of existing stimulated Brillouin scattering BOTDA systems, which struggle to balance long distance and high measurement accuracy, and are sensitive to the cross-sensitivity of temperature and strain.

[0044] 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 high-precision dual-parameter sensing device for chaotic BOTDA incorporating Raman scattering, characterized in that, It includes a narrow linewidth laser (1), a broadband chaotic laser source, a sensing fiber (8), a first optical circulator (18), a photodetector (24), an avalanche photodetector (23), and a data acquisition and analysis system (25). The narrow linewidth laser output by the narrow linewidth laser (1) is modulated by double-sideband and enters one end of the sensing fiber (8) as the probe light; the chaotic laser output by the broadband chaotic laser source is pulsed and split into two paths, one as the reference light and the other as the pump light, which enters the other end of the sensing fiber (8) through the first optical circulator (18). The Raman scattered light signal generated by the spontaneous Raman scattering of the pump light in the sensing fiber (8) is output by the first optical circulator (18), and together with the reference light, is detected by the avalanche photodetector (23) and transmitted to the data acquisition and analysis system. At the same time, the chaotic pump light and probe light propagating in opposite directions undergo stimulated Brillouin scattering in the sensing fiber (8). The amplified probe light is output through the first optical circulator (18), and after photoelectric conversion by the photodetector (24), it is sent to the data acquisition and analysis system (25) to obtain the Brillouin signal. The data acquisition and analysis system (25) is used to demodulate the temperature distribution along the sensing fiber (8) based on the Raman scattered light signal and the reference light signal; it is also used to demodulate the strain distribution along the sensing fiber (8) based on the Brillouin signal detected by the photodetector (24) and the temperature distribution, thereby achieving cross-demodulation of temperature and strain.

2. The chaotic BOTDA dual-parameter high-precision sensing device integrating Raman scattering according to claim 1, characterized in that, It also includes an electro-optic modulator (2), a first erbium-doped fiber amplifier (5), a polarization scrambler (6), an optical isolator (7), a semiconductor optical amplifier (15), a second erbium-doped fiber amplifier (16), a first fiber coupler (17), a first optical circulator (18), a wavelength division multiplexer (19), and a second fiber coupler (22). The narrow linewidth laser output by the narrow linewidth laser (1) is modulated by the electro-optic modulator (2) on both sides, amplified by the first erbium-doped fiber amplifier (5), and then enters one end of the sensing fiber (8) as the probe light after passing through the polarizer (6) and the optical isolator (7). The chaotic laser output from the broadband chaotic laser source is pulse-modulated by a semiconductor optical amplifier (15). The pulse-modulated chaotic laser is amplified by a second erbium-doped fiber amplifier (16) and then split into two paths by a first fiber coupler (17). One path is used as a reference light and is incident on the second fiber coupler (22). The other path is used as a pump light and enters the other end of the sensing fiber (8) through a first optical circulator (18). The pump light undergoes spontaneous Raman scattering in the sensing fiber (8). The generated Raman scattered light signal is output through the first optical circulator (18) and wavelength division multiplexer (19), and then incident on the second fiber coupler (22) together with the reference light. The signal coupled by the second fiber coupler (22) is detected by the avalanche photodetector (23) and then transmitted to the data acquisition and analysis system (25). The chaotic pump light and probe light propagating in opposite directions undergo stimulated Brillouin scattering in the sensing fiber (8). The amplified probe light is output through the first optical circulator (18) and wavelength division multiplexer (19), and one of the sidebands is filtered out by the filter. Then it enters the photodetector (24) for photoelectric conversion and is sent to the data acquisition and analysis system (25).

3. The chaotic BOTDA dual-parameter high-precision sensing device integrating Raman scattering according to claim 2, characterized in that, The broadband chaotic laser source includes a distributed feedback semiconductor laser (9), a second optical circulator (10), a third fiber coupler (11), a third erbium-doped fiber amplifier (12), a fiber polarization controller (13), and an optical attenuator (14). The distributed feedback semiconductor laser (9) has no built-in isolator. Its output laser enters the third fiber coupler (11) after passing through the second optical circulator (10). The light output from the first output end of the third fiber coupler (11) passes through the third erbium-doped fiber amplifier (12), the fiber polarization controller (13), and the optical attenuator (14), and then returns through the second optical circulator (10) and enters the distributed feedback semiconductor laser (9), causing disturbance and outputting a broadband chaotic laser. The broadband chaotic laser is output from the second output end of the third fiber coupler (11).

4. The chaotic BOTDA dual-parameter high-precision sensing device integrating Raman scattering according to claim 2, characterized in that, The filter includes a third optical circulator (20) and a fiber Bragg grating (21). The amplified probe light is output through the first optical circulator (18) and wavelength division multiplexer (19), and then enters the fiber Bragg grating (21) through the third optical circulator (20). One of the sidebands is filtered out by the fiber Bragg grating (21), and then returns to the third optical circulator (20) and enters the photodetector (24).

5. The chaotic BOTDA dual-parameter high-precision sensing device integrating Raman scattering according to claim 2, characterized in that, The generated Raman scattered light signal is output as a Raman anti-Stokes light signal after passing through the first optical circulator (18) and wavelength division multiplexer (19).

6. The chaotic BOTDA dual-parameter high-precision sensing device integrating Raman scattering according to claim 2, characterized in that, The first fiber coupler (17), the second fiber coupler (22), and the third fiber coupler (11) are all 1×2 fiber couplers.

7. A high-precision dual-parameter sensing device for chaotic BOTDA incorporating Raman scattering according to claim 2, characterized in that, The wavelengths of the narrow linewidth laser (1) and the broadband chaotic laser source are both 1550nm. The 1550nm / 1450nm channel of the wavelength division multiplexer (19) is connected to the output of the first optical circulator (18), the 1450nm channel is connected to the second fiber coupler (22), and the 1550nm channel is connected to the filter.

8. The chaotic BOTDA dual-parameter high-precision sensing device fused with Raman scattering according to claim 1, characterized in that, It also includes a microwave signal generator (3), a bias controller (4), the signal output terminal of the microwave signal generator (3) is connected to the microwave signal input terminal of the high-speed electro-optic modulator (2); the signal output terminal of the bias controller (4) is connected to the bias input terminal of the high-speed electro-optic modulator (2).

9. The chaotic BOTDA dual-parameter high-precision sensing device integrating Raman scattering according to claim 1, characterized in that, The data acquisition and analysis system (25) is used to obtain the temperature distribution along the sensing fiber (8) by performing correlation demodulation based on the Raman scattered light signal and the reference light signal.

10. A high-precision dual-parameter sensing method for chaotic BOTDA based on Raman scattering, implemented based on the high-precision dual-parameter sensing device for chaotic BOTDA based on Raman scattering as described in any one of claims 1 to 7, comprising the following steps: Step 1: Obtain the reference optical signal and the Raman scattered optical signal along the sensing fiber (8), and perform relevant demodulation calculations to obtain the temperature distribution along the sensing fiber (8); Step 2: Obtain the Brillouin signal along the sensing fiber (8) and, in conjunction with the temperature distribution, perform temperature calibration on the strain distribution along the demodulated sensing fiber 8.

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