CN114526683B - High-spatial-resolution temperature and strain optical fiber sensing system and measuring method - Google Patents
High-spatial-resolution temperature and strain optical fiber sensing system and measuring method Download PDFInfo
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Abstract
The invention relates to a high-spatial-resolution temperature strain optical fiber sensing system and a measuring method, belonging to the technical field of distributed optical fiber sensing; the temperature and strain cross sensitivity problem in the distributed optical fiber sensing process is solved; the temperature and the strain of the single-mode fiber are measured simultaneously by utilizing Brillouin scattering and Rayleigh backscattering, the Brillouin optical frequency domain analysis principle and the Rayleigh reflection principle are combined, the Brillouin frequency shift and the backward Rayleigh scattering wavelength drift are measured simultaneously, and finally, the temperature and the strain are sensed simultaneously based on the difference of two physical quantities and the temperature and the strain sensitivity coefficient.
Description
Technical Field
The invention relates to an optical fiber sensing system, belongs to the technical field of distributed optical fiber sensing, and in particular relates to a high-spatial-resolution temperature and strain optical fiber sensing system and a measuring method.
Background
When light is transmitted in an optical fiber, the change of physical fields such as temperature, strain or electromagnetic field in the external environment can change parameters such as light intensity, wavelength, phase, frequency, polarization state and the like of the transmitted light. The change of the physical field parameter can be demodulated by monitoring the change of the parameter of the transmitted light, namely the sensing of the sensing physical quantity is realized by using the optical fiber. Compared with the traditional sensing technology, the optical fiber sensing technology has the advantages of high sensitivity, light weight, strong electromagnetic interference resistance, good electrical insulation, large transmission capacity, long service life and the like, thereby being widely applied to safety monitoring of important infrastructures such as traffic tunnels, bridge buildings, petroleum pipelines, coal mines and the like in engineering and various fields of life.
Distributed optical fiber sensing temperature and strain sensing technology is widely used in industrial monitoring. However, most sensing systems relying on a single optical parameter are difficult to realize temperature and strain common sensing, and some sensing systems even have a cross sensitivity problem, and errors are introduced in actual monitoring, so that the change of temperature and strain cannot be distinguished. With the application of special optical fibers and the development of technologies based on other scattering mechanism sensing and the like, the temperature strain cross sensitivity problem is solved to a certain extent, but higher spatial resolution is difficult to ensure, and application bottlenecks exist in occasions needing short distance and high spatial resolution, such as spacecraft internal link diagnosis, medical instrument structure deformation monitoring and the like, so that a high spatial resolution temperature strain simultaneous sensing scheme is needed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and solves the technical problems that: an improvement in the hardware architecture of high spatial resolution temperature and strain fiber optic sensing systems is provided.
In order to solve the technical problems, the invention adopts the following technical scheme: the temperature strain acquisition system based on the Brillouin scattering optical frequency domain comprises a narrow-line laser, a first optical fiber coupler, a detection optical path, a pumping optical path, a sensing optical fiber, a second wavelength division multiplexer and a vector network analysis device, wherein the narrow-line laser divides an emitted 1310nm narrow-line laser source signal into two paths through the first optical fiber coupler, one path is used as detection light to enter the detection optical path, the detection light enters the sensing optical fiber after being processed, the other path is used as the pumping optical path, the pump light after being subjected to electro-optical modulation is input into the vector network analysis device for measurement and demodulation, then enters the second wavelength division multiplexer after being processed, enters the sensing optical fiber for carrying out a Brillouin process, and the detection light carries SBS information and is processed and then enters the vector network analysis device for measurement after being subjected to the stimulated Brillouin process in the optical fiber, so that a baseband transmission function of the sensing optical fiber is obtained;
the temperature strain acquisition system based on Rayleigh scattering light frequency domain reflection comprises a tunable laser, a third optical fiber coupler, a main interference system and an auxiliary interference system, wherein the tunable laser divides 1550nm laser signals into two paths to be emitted through the third optical fiber coupler, one path enters the main interference system to be processed and then outputs backward Rayleigh scattering light, and the detection light and a pumping light path of the temperature strain acquisition system based on the Brillouin scattering light frequency domain enter the main interference system, and the other path enters the auxiliary interference system.
The data processing software maps data from an optical frequency domain to a distance domain through a fast Fourier algorithm after the data acquisition system acquires reference data and test data, selects distance domain information of a small section of test optical fiber in the distance domain by using a sliding window, maps the information of the distance domain to the optical frequency domain through an inverse fast Fourier algorithm, and demodulates a backward Rayleigh scattering spectrum peak offset before and after the temperature or stress change of the small section of optical fiber in the optical frequency domain by using a cross-correlation algorithm, and finally calculates the temperature or strain change of the small section of optical fiber according to the peak offset.
The detection light path comprises an IQ modulator, a radio frequency microwave signal source, a first erbium-doped optical fiber amplifier, an optical isolator, a first wavelength division multiplexer and a tail end optical fiber ring, wherein the emergent end of a 1310nm narrow linewidth laser is connected with a port A1 of an optical fiber coupler, and a port A2 of the optical fiber coupler is connected with a port B1 of the IQ modulator; the radio frequency output end of the radio frequency microwave signal source is connected with a radio frequency incidence port B3 of the IQ modulator through a high-frequency coaxial cable; the port B2 of the IQ modulator is connected with the incident end of the first erbium-doped fiber amplifier; the emergent end of the first erbium-doped fiber amplifier is connected with the incident end of the optical isolator; the emergent end of the optical isolator is connected with a port C1 of the first wavelength division multiplexer; the port C3 of the first wavelength division multiplexer is connected to the entrance end of the distal fiber optic ring.
The pumping light path comprises an electro-optical modulator, a second optical fiber coupler, a second erbium-doped optical fiber amplifier, a scrambler, a first circulator, a first photoelectric detector, a second photoelectric detector and a signal source, and a port A3 of the optical fiber coupler is connected with a port D1 of the electro-optical modulator;
the port D2 of the electro-optic modulator is connected with the port E1 of the second optical fiber coupler; the port E3 of the second optical fiber coupler is connected with the incident end of the first photoelectric detector; the emergent end of the first photoelectric detector is connected with a port H2 of the vector network analysis device;
the port E2 of the second optical fiber coupler is connected with the incident end of the second erbium-doped optical fiber amplifier; the emergent end of the second erbium-doped fiber amplifier is connected with the incident end of the scrambler; the emergent end of the deflector is connected with a port F1 of the first circulator; the port F3 of the first circulator is connected with the incident end of the second photoelectric detector; the emergent end of the second photoelectric detector is connected with a port H3 of the vector network analysis device;
the port F2 of the first circulator is connected with the port G1 of the second wavelength division multiplexer; the port G2 of the second wavelength division multiplexer is connected with the incident end of the sensing optical fiber; the emergent end of the sensing optical fiber is connected with a port C2 of the first wavelength division multiplexer; the port H1 of the vector network analysis device is connected with the incident end of the signal source; the outgoing end of the signal source is connected with a port D3 of the electro-optical modulator.
The main interference system comprises a fourth optical fiber coupler, a second circulator, a first polarization controller, a second polarization controller, a fifth optical fiber coupler and a polarization beam splitter, wherein the emergent end of a 1550nm tunable laser is connected with a port I1 of a third optical fiber coupler; the port I2 of the third optical fiber coupler is connected with the port J1 of the fourth optical fiber coupler; the exit port J2 of the fourth optical fiber coupler is connected with the port K1 of the second circulator; the port K2 of the second circulator is connected with the incident end of the first polarization controller; the emergent end of the first polarization controller is connected with a port G3 of the second wavelength division multiplexer;
the port J3 of the fourth optical fiber coupler is connected with the incident end of the second polarization controller; the emergent end of the second polarization controller is connected with L2 of the fifth optical fiber coupler;
the port K3 of the second circulator is connected with the port L1 of the fifth optical fiber coupler; the port L3 of the fifth optical fiber coupler is connected with the port M1 of the polarization beam splitter; the port M2 of the polarization beam splitter is connected with the port O1 of the data acquisition system; the port M3 of the polarization beam splitter is connected with the port O2 of the data acquisition system.
The auxiliary interference system comprises a triggering interferometer, and a port I3 of the third optical fiber coupler is connected with an incident end of the triggering interferometer; the emergent end of the triggering interferometer is connected with a port O3 of the data acquisition system.
A high spatial resolution temperature and strain fiber sensing measurement method comprises the following steps:
s1: acquiring a baseband transfer function of the sensing optical fiber through a temperature strain acquisition system based on a Brillouin scattering optical frequency domain, and obtaining the Brillouin frequency shift of the sensing optical fiber after resolving;
s2: acquiring backward Rayleigh scattering wavelength drift of a sensing optical fiber through a temperature strain acquisition system based on Rayleigh scattering light frequency domain reflection;
s3: after the data acquisition system acquires the reference data and the test data, the data processing software maps the data from an optical frequency domain to a distance domain through a fast Fourier algorithm, the distance domain information of a small section of test optical fiber is selected by using a sliding window in the distance domain, the distance domain information is mapped to the optical frequency domain through an inverse fast Fourier algorithm, the temperature or the peak offset of a backward Rayleigh scattering spectrum before and after the stress change of the small section of optical fiber is demodulated by using a cross-correlation algorithm in the optical frequency domain, and finally the temperature or the change of the strain of the small section of optical fiber is calculated according to the peak offset.
The specific steps of the S1 are as follows:
the narrow linewidth laser source signal emitted by the narrow linewidth laser working at 1310nm is divided into two paths through the first optical fiber coupler, one path is used as detection light to enter the IQ modulator from the port B1, and the detection light is modulated by the IQ modulator through the radio frequency microwave signal source by the signal incident from the port B3 around the Brillouin frequency shift by suppressing the carrier single sideband signal;
the detection light enters a first erbium-doped optical fiber amplifier for optical power amplification after single sideband modulation, the detection light amplified by the first erbium-doped optical fiber amplifier enters an optical isolator, the detection light emitted by the optical isolator enters a first wavelength division multiplexer from a port C1, the detection light enters a sensing optical fiber after being emitted from a port C2 of the first wavelength division multiplexer, and the detection light which is subjected to stimulated Brillouin effect with pulse light in the sensing optical fiber enters a port G2 of a second wavelength division multiplexer;
the other path of the first optical fiber coupler is used as a pumping light path to enter the electro-optical modulator from the port D1, and the port H1 of the vector network analysis device outputs a signal within the frequency range of the transfer function to drive a radio frequency signal source;
the pump light modulated by each angular frequency Wm in the electro-optical modulator enters the second optical fiber coupler through the port E1, and part of light of the output port E3 of the second optical fiber coupler enters the first photoelectric detector to be converted into an electric signal, and the electric signal enters the vector network analysis device through the incident port H2 to be measured and demodulated;
the other part of pump light output by the second optical fiber coupler enters the second erbium-doped optical fiber amplifier through the emergent port E2 to be amplified, the pump light emergent from the second erbium-doped optical fiber amplifier enters the polarization scrambler, the pump light emergent from the polarization scrambler enters the emergent port F2 from the incident port F1 of the first circulator, and then enters the second wavelength division multiplexer and then enters the sensing optical fiber to be stimulated Brillouin process;
after the stimulated Brillouin process in the optical fiber, the detection light carries SBS information, the SBS information passes through the sensing optical fiber, enters the first circulator after entering through the port G2 of the second wavelength division multiplexer, exits from the port G1 of the first circulator, enters the second photoelectric detector, is converted into an electric signal, enters the vector network analysis device from the port H3 and is measured, and the baseband transfer function of the sensing optical fiber is obtained.
The specific steps of the S2 are as follows:
a tunable laser operating at 1550nm had a spectral ratio of 90:10 into two ends, 90% of outgoing light enters the main system through a port I2, and firstly enters 90 through a port J1: 10, after the detection light emitted from 90% of the exit port J2 of the fourth optical fiber coupler enters the second circulator, the detection light is then emitted from the second circulator port K2, the detection light emitted from the second circulator port K2 enters the port G3 of the second wavelength division multiplexer through the first polarization controller, the detection light emitted from the port G2 of the second wavelength division multiplexer enters the sensing optical fiber, and the detection light of 1550nm emitted from the sensing optical fiber enters the first wavelength division multiplexer from the port C2;
the backward Rayleigh scattered light of 1550nm in the detection optical fiber enters from a port G2 after passing through a second wavelength division multiplexer, the backward Rayleigh scattered light emitted from a port G3 of the second wavelength division multiplexer enters into a port K2 of a second circulator through a first polarization controller and exits from the port K3, and enters into a fifth optical fiber coupler through a port L1 to be mixed with reference light;
the 10% emergent port J3 of the fourth optical fiber coupler is used as reference light to enter the second polarization controller from the incident port, and the second polarization controller enters the fifth optical fiber coupler from the port L2 to be mixed with the detection light after emergent;
the tunable laser has a spectral ratio of 90: after the third optical fiber coupler is divided into two ends to be emitted, 10% of light enters the auxiliary interference system from the emitting port, and enters the data acquisition system through the triggering interferometer to form a triggering signal.
Compared with the prior art, the invention has the following beneficial effects:
1. different from the optical time domain reflection technology, the invention adopts the optical frequency domain measurement method, so that the measurement spatial resolution can be greatly improved.
2. The invention avoids the problems of lower precision and higher implementation cost caused by the conventional method of laying the accompanying reference optical fiber and expensive special optical fiber, and can realize simultaneous measurement of temperature and strain by using only a single mode optical fiber based on the principles of Brillouin frequency shift and backward Rayleigh scattering wavelength drift.
Drawings
The invention is further described below with reference to the accompanying drawings:
FIG. 1 is a schematic diagram of the structure of the present invention;
in the figure: 1. a narrow linewidth laser; 2. a first optical fiber coupler; 3. an IQ modulator; 4. a radio frequency microwave signal source; 5. a first erbium-doped fiber amplifier; 6. an optical isolator; 7. a first wavelength division multiplexer; 8. a distal fiber optic ring; 9. a sensing optical fiber; 10. an electro-optic modulator; 11. a second fiber coupler; 12. a second erbium-doped fiber amplifier; 13. a scrambler; 14. a first circulator; 15. a second wavelength division multiplexer; 16. a first photodetector; 17. a second photodetector; 18. a signal source; 19. vector network analysis means; 20. a tunable laser; 21. a third fiber coupler; 22. a fourth fiber coupler; 23. a second circulator; 24. a first polarization controller; 25. a second polarization controller; 26. a fifth fiber coupler; 27. a polarizing beam splitter; 28. a data acquisition system; 29. triggering the interferometer.
Detailed Description
As shown in fig. 1, the high spatial resolution temperature and strain fiber sensing system provided by the present invention includes: a 1310nm narrow linewidth laser 1, a first optical fiber coupler 2, an IQ modulator 3, a radio frequency microwave signal source 4, a first erbium-doped optical fiber amplifier 5, an optical isolator 6, a first wavelength division multiplexer 7, a terminal optical fiber loop 8, a sensing optical fiber 9, an electro-optic modulator 10, a second optical fiber coupler 11, a second erbium-doped optical fiber amplifier 12, a scrambler 13, a first circulator 14, a second wavelength division multiplexer 15, a first photodetector 16, a second photodetector 17, a signal source 18, a vector network analysis device 19, a 1550nm tunable laser 20, a third optical fiber coupler 21, a fourth optical fiber coupler 22, a second circulator 23, a first polarization controller 24, a second polarization controller 25, a fifth optical fiber coupler 26, a polarization beam splitter 27, a data acquisition system 28 and a triggering interferometer 29.
The invention is characterized in that the Brillouin optical frequency domain analysis principle and the Rayleigh Li Guangpin domain reflection principle are combined to realize the simultaneous measurement of Brillouin frequency shift and backward Rayleigh scattering wavelength drift, thereby realizing the detection of temperature and strain without cross sensitivity. Wherein, the temperature and strain measurement implementation mode based on the Brillouin scattering optical frequency domain analysis principle is as follows:
the narrow linewidth laser source signal emitted by the narrow linewidth laser 1 working at 1310nm is divided into two paths through the first optical fiber coupler 2, one path is used as detection light, the detection light enters the IQ modulator 3 from the port B1, and the detection light is modulated by the IQ modulator 3 through the radio frequency microwave signal source 4 by the signal incident from the port B3 around the Brillouin frequency shift by the carrier-suppressing single sideband signal. The detection light enters the first erbium-doped optical fiber amplifier 5 for optical power amplification after single sideband modulation, the detection light amplified by the first erbium-doped optical fiber amplifier 5 enters the optical isolator 6, the optical isolator 6 ensures unidirectional transmission, the detection light emitted by the optical isolator enters the first wavelength division multiplexer 7 from the port C1, the detection light emitted by the first wavelength division multiplexer 7 enters the sensing optical fiber 9 after the detection light is emitted from the port C2 of the first wavelength division multiplexer 7, and the detection light which is subjected to stimulated Brillouin effect with the pulse light in the sensing optical fiber enters the port G2 of the second wavelength division multiplexer 15;
the other path of the first optical fiber coupler 2 is used as a pumping light path to enter the electro-optical modulator 10 from the port D1, and the port H1 of the vector network analysis device 19 outputs a signal in the frequency range of the transfer function to drive the radio frequency signal source 18. The pump light modulated by each angular frequency Wm in the electro-optical modulator 10 enters the second optical fiber coupler 11 through the port E1, and 10% of the light output by the port E3 of the second optical fiber coupler 11 enters the first photodetector 16 to be converted into an electric signal, and enters the vector network analysis device 19 through the incident port H2 for measurement and demodulation. The second fiber coupler 11 outputs 90% of the pump light to the second erbium-doped fiber amplifier 12 through the exit port E2 for amplification, and the pump light exiting through the second erbium-doped fiber amplifier 12 enters the scrambler 13, and the scrambler 13 is used to minimize gain fluctuation due to the change of the polarization state of the pump along the sensing fiber. The pump light emitted from the deflector 13 enters from the incident port F1 of the first circulator 14 and exits from the port F2, and then enters the wavelength division multiplexer 15 and then exits into the sensing optical fiber 9 for stimulated brillouin process.
After the stimulated brillouin process in the optical fiber, the detection light carries SBS information, after passing through the sensing optical fiber 9, enters the circulator 14 after entering through the port G2 of the wavelength division multiplexer 15 and exiting from the port G1, exits from the port F3 of the circulator 14 and enters the second photoelectric detector 17 to be converted into an electric signal, then enters the vector network analysis device 19 from the port H3 to be measured, the baseband transmission function of the sensing optical fiber is obtained, the analog signal output by the network analyzer is converted into a digital signal through analog-to-digital conversion, and then inverse fast Fourier transformation is carried out, so that the result can be approximately the sensing optical fiber impulse response H (t), and the Brillouin frequency shift of the optical fiber is included.
Temperature and strain measurement embodiments based on the principle of rayleigh scattering optical frequency domain reflection are as follows:
the tunable laser 20 operating at 1550nm has a split ratio of 90:10, the third fiber coupler 21 is divided into two ends to emit, 90% of emitted light enters the main system through the port I2, and first enters 90 through the port J1: 10, the fourth optical fiber coupler 22 of the present invention, after the probe light emitted from 90% of the exit port J2 of the fourth optical fiber coupler 22 enters the second circulator 23, the probe light is then emitted from the port K2 of the second circulator 23, the probe light emitted from the port K2 of the second circulator 23 enters the port G3 of the second wavelength division multiplexer 15 through the first polarization controller 24, the probe light emitted from the port G2 of the second wavelength division multiplexer 15 enters the sensing optical fiber 9, the probe light of 1550nm emitted from the sensing optical fiber 9 enters the first wavelength division multiplexer 7 through the port C2, the first wavelength division multiplexer 7 is used for emitting the probe light of 1550nm emitted from the tunable laser 20 into the end optical fiber from the port C3 so as to be separated from the optical fiber loop, the end optical fiber loop 8 is simultaneously used for reducing fresnel reflection, the probe light of 1550nm enters from the port G2 after the backward rayleigh scattering light in the probe optical fiber 9 passes through the wavelength division multiplexer 15, the backward rayleigh scattering light emitted from the port G3 of the wavelength division multiplexer 15 enters the first polarization controller 24 into the second circulator 23, the probe light enters the first wavelength division multiplexer 7 through the port K2, the first wavelength division multiplexer 7 is used for coupling the probe light from the exit port K2 through the fifth port L26, and the reference light enters the fifth port 1.
The 10% output port J3 of the fourth fiber coupler 22 is used as reference light, and enters the second polarization controller 25 from the input port, and the second polarization controller 25 is output and enters the fifth fiber coupler 26 from the port L2 to mix with the probe light.
The reference light and the probe light enter the polarization beam splitter 27 after being mixed in the fifth fiber coupler 26. A mixed-mode polarization diversity receiving mode is adopted in a main interference receiving part to eliminate the polarization fading phenomenon. The data acquisition process after each scan of the data acquisition system 28 is identical, and the data acquisition card triggers and acquires the test signal of the main interferometer according to the beat frequency signal of the auxiliary interference. After the reference data and the test data are acquired, the data processing software maps the data from an optical frequency domain to a distance domain through a fast Fourier algorithm, the distance domain information of a small section of test optical fiber is selected by using a sliding window in the distance domain, the distance domain information is mapped to the optical frequency domain through an inverse fast Fourier algorithm, the backward Rayleigh scattering spectrum peak offset before and after the temperature or stress change of the small section of optical fiber is demodulated by using a cross-correlation algorithm in the optical frequency domain, and finally the temperature or strain change of the small section of optical fiber is calculated according to the peak offset. The temperature or stress variation of each segment of the fiber can be measured by repeating the above process.
After the Brillouin frequency shift and the backward Rayleigh scattering wavelength shift are obtained, the complete temperature and strain discrimination can be realized by combining two equations according to the linear relation between the Brillouin frequency shift and the backward Rayleigh scattering spectral shift and the temperature strain.
Wherein:∆Tis the amount of change in temperature and,∆εis the amount of change in the strain,
and->
Is the strain coefficient and temperature coefficient of the Rayleigh scattering wavelength drift,/for>
And->
Is the strain and temperature coefficient of the brillouin shift, < >>
Is the brillouin shift change amount,∆λis the backward Rayleigh scattering wavelength drift,>
. And for a certain sensing optical fiber, according to the temperature and the strain coefficient of the Brillouin frequency shift and the temperature and the strain coefficient of the backward Rayleigh scattering wavelength drift, the temperature strain distribution information of the sensing optical fiber can be obtained by utilizing the temperature and the strain coefficient.
The invention relates to a high-spatial-resolution temperature and strain sensing system which is used for effectively solving the problem of temperature and strain cross sensitivity in the distributed optical fiber sensing process and ensuring higher spatial resolution. The invention combines the Brillouin optical frequency domain analysis principle and the Rayleigh Li Guangpin domain reflection principle in a common single-mode fiber to realize simultaneous measurement of Brillouin frequency shift and backward Rayleigh scattering wavelength drift, and finally realizes simultaneous sensing of temperature strain based on the difference of two physical quantities on temperature and strain sensitivity coefficients.
The specific structure of the invention needs to be described that the connection relation between the component modules adopted by the invention is definite and realizable, and besides the specific description in the embodiment, the specific connection relation can bring corresponding technical effects, and solves the technical problems of the invention on the premise of not depending on the execution of corresponding software programs.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (9)
1. A high spatial resolution temperature and strain fiber optic sensing system characterized by: the system comprises a temperature strain acquisition system based on a Brillouin scattering optical frequency domain and a temperature strain acquisition system based on Rayleigh scattering optical frequency domain reflection, wherein the temperature strain acquisition system based on the Brillouin scattering optical frequency domain comprises a narrow-line laser (1), a first optical fiber coupler (2), a detection optical path, a pumping optical path, a sensing optical fiber (9), a second wavelength division multiplexer (15) and a vector network analysis device (19), the narrow-line laser (1) divides an emitted 1310nm narrow-line laser source signal into two paths through the first optical fiber coupler (2), one path serves as detection light to enter the detection optical path, the detection light enters the sensing optical fiber (9) after being processed, the other path serves as a pumping optical path, the pumping light after being subjected to electro-optic modulation is input into the vector network analysis device (19) for measurement demodulation, then enters the second wavelength division multiplexer (15) after being processed, and then enters the sensing optical fiber (9) for stimulated Brillouin process, after the stimulated Brillouin process, the detection light carrying information enters the vector network analysis device (19) after being processed in the optical fiber, and the SBS measurement function is obtained after the stimulated Brillouin process in the optical fiber;
the temperature strain acquisition system based on Rayleigh scattering light frequency domain reflection comprises a tunable laser (20), a third optical fiber coupler (21), a main interference system and an auxiliary interference system, wherein the tunable laser (20) divides 1550nm laser signals into two paths to be emitted through the third optical fiber coupler (21), one path enters the main interference system to be processed and then outputs backward Rayleigh scattering light, and the detection light and a pumping light path of the temperature strain acquisition system based on the Brillouin scattering light frequency domain enter the main interference system, and the other path enters the auxiliary interference system.
2. A high spatial resolution temperature and strain fiber optic sensing system as in claim 1 wherein: the system also comprises a data acquisition system (28), wherein light paths emitted by the main interference system and the auxiliary interference system enter the data acquisition system (28), after the data acquisition system (28) acquires reference data and test data, data are mapped from an optical frequency domain to a distance domain by data processing software through a fast Fourier algorithm, distance domain information of a small section of test optical fiber is selected by using a sliding window in the distance domain, the information of the distance domain is mapped to the optical frequency domain by an inverse fast Fourier algorithm, and the temperature or the peak offset of a backward Rayleigh scattering spectrum before and after the stress change of the small section of optical fiber is demodulated by using a cross-correlation algorithm in the optical frequency domain, and finally the temperature or the change of the strain of the small section of optical fiber is calculated according to the peak offset.
3. A high spatial resolution temperature and strain fiber optic sensing system as in claim 2 wherein: the detection light path comprises an IQ modulator (3), a radio frequency microwave signal source (4), a first erbium-doped optical fiber amplifier (5), an optical isolator (6), a first wavelength division multiplexer (7) and an end optical fiber ring (8), wherein the emergent end of a 1310nm narrow linewidth laser (1) is connected with a port A1 of an optical fiber coupler (2), and a port A2 of the optical fiber coupler (2) is connected with a port B1 of the IQ modulator (3); the radio frequency output end of the radio frequency microwave signal source (4) is connected with the radio frequency incidence port B3 of the IQ modulator (3) through a high-frequency coaxial cable; the port B2 of the IQ modulator (3) is connected with the incident end of the first erbium-doped fiber amplifier (5); the emergent end of the first erbium-doped fiber amplifier (5) is connected with the incident end of the optical isolator (6); the emergent end of the optical isolator (6) is connected with a port C1 of the first wavelength division multiplexer (7); the port C3 of the first wavelength division multiplexer (7) is connected to the incident end of the terminal optical fiber ring (8).
4. A high spatial resolution temperature and strain fiber optic sensing system as in claim 3 wherein: the pumping light path comprises an electro-optical modulator (10), a second optical fiber coupler (11), a second erbium-doped optical fiber amplifier (12), a scrambler (13), a first circulator (14), a first photoelectric detector (16), a second photoelectric detector (17) and a signal source (18), and a port A3 of the optical fiber coupler (2) is connected with a port D1 of the electro-optical modulator (10);
the port D2 of the electro-optical modulator (10) is connected with the port E1 of the second optical fiber coupler (11); the port E3 of the second optical fiber coupler (11) is connected with the incident end of the first photoelectric detector (16); the emergent end of the first photoelectric detector (16) is connected with a port H2 of the vector network analysis device (19);
the port E2 of the second optical fiber coupler (11) is connected with the incident end of the second erbium-doped optical fiber amplifier (12); the emergent end of the second erbium-doped fiber amplifier (12) is connected with the incident end of the scrambler (13); the emergent end of the deflector (13) is connected with a port F1 of the first circulator (14); the port F3 of the first circulator (14) is connected with the incident end of the second photoelectric detector (17); the emergent end of the second photoelectric detector (17) is connected with a port H3 of the vector network analysis device (19);
the port F2 of the first circulator (14) is connected with the port G1 of the second wavelength division multiplexer (15); the port G2 of the second wavelength division multiplexer (15) is connected with the incident end of the sensing optical fiber (9); the emergent end of the sensing optical fiber (9) is connected with a port C2 of the first wavelength division multiplexer (7); the port H1 of the vector network analysis device (19) is connected with the incident end of the signal source (18); the output end of the signal source (18) is connected with a port D3 of the electro-optical modulator (10).
5. The high spatial resolution temperature and strain fiber optic sensing system of claim 4, wherein: the main interference system comprises a fourth optical fiber coupler (22), a second circulator (23), a first polarization controller (24), a second polarization controller (25), a fifth optical fiber coupler (26), a polarization beam splitter (27), and an exit end of a 1550nm tunable laser (20) is connected with a port I1 of a third optical fiber coupler (21); the port I2 of the third optical fiber coupler (21) is connected with the port J1 of the fourth optical fiber coupler (22); an exit port J2 of the fourth optical fiber coupler (22) is connected with a port K1 of the second circulator (23); the port K2 of the second circulator (23) is connected with the incident end of the first polarization controller (24); the emergent end of the first polarization controller (24) is connected with a port G3 of the second wavelength division multiplexer (15);
the port J3 of the fourth optical fiber coupler (22) is connected with the incident end of the second polarization controller (25); the emergent end of the second polarization controller (25) is connected with L2 of the fifth optical fiber coupler (26);
the port K3 of the second circulator (23) is connected with the port L1 of the fifth optical fiber coupler (26); the port L3 of the fifth optical fiber coupler (26) is connected with the port M1 of the polarization beam splitter (27); the port M2 of the polarization beam splitter (27) is connected with the port O1 of the data acquisition system (28); the port M3 of the polarization beam splitter (27) is connected with the port O2 of the data acquisition system (28).
6. A high spatial resolution temperature and strain fiber optic sensing system as in claim 5 wherein: the auxiliary interference system comprises a triggering interferometer (29), and a port I3 of the third optical fiber coupler (21) is connected with an incident end of the triggering interferometer (29); the exit end of the triggering interferometer (29) is connected with a port O3 of the data acquisition system (28).
7. A high spatial resolution temperature and strain fiber optic sensing measurement method employing the high spatial resolution temperature and strain fiber optic sensing system of any of claims 2-5, characterized by: the method comprises the following steps:
s1: acquiring a baseband transfer function of the sensing optical fiber (9) through a temperature strain acquisition system based on a Brillouin scattering optical frequency domain, and obtaining the Brillouin frequency shift of the sensing optical fiber (9) after resolving;
s2: the backward Rayleigh scattering wavelength drift of the sensing optical fiber (9) is obtained through a temperature strain acquisition system based on Rayleigh scattering light frequency domain reflection;
s3: after the data acquisition system (28) acquires the reference data and the test data, data processing software maps the data from an optical frequency domain to a distance domain through a fast Fourier algorithm, distance domain information of a small section of test optical fiber is selected by using a sliding window in the distance domain, the information of the distance domain is mapped to the optical frequency domain through an inverse fast Fourier algorithm, backward Rayleigh scattering spectrum peak offset before and after temperature or stress change of the small section of optical fiber is demodulated by using a cross-correlation algorithm in the optical frequency domain, and finally the temperature or strain change of the small section of optical fiber is calculated according to the peak offset.
8. The high spatial resolution temperature and strain fiber optic sensing measurement method of claim 7, wherein: the specific steps of the S1 are as follows:
the narrow linewidth laser source signal emitted by the narrow linewidth laser (1) working at 1310nm is divided into two paths through the first optical fiber coupler (2), one path of the signal is used as detection light to enter the IQ modulator (3) from the port B1, and the detection light is modulated by the IQ modulator (3) through the radio frequency microwave signal source (4) by the signal incident from the port B3 around the Brillouin frequency shift to inhibit carrier single sideband signal;
the detection light enters a first erbium-doped optical fiber amplifier (5) for optical power amplification after single sideband modulation, the detection light amplified by the first erbium-doped optical fiber amplifier (5) enters an optical isolator (6), the detection light emitted by the optical isolator (6) enters a first wavelength division multiplexer (7) from a port C1, the detection light enters a sensing optical fiber (9) after being emitted from a port C2 of the first wavelength division multiplexer (7), and the detection light which is subjected to stimulated Brillouin effect with pulse light in the sensing optical fiber (9) enters a port G2 of a second wavelength division multiplexer (15);
the other path of the first optical fiber coupler (2) is used as a pumping light path to enter the electro-optical modulator (10) from the port D1, and the port H1 of the vector network analysis device (19) outputs a signal in the frequency range of the transfer function to drive the radio frequency signal source (18);
the pump light modulated by each angular frequency Wm in the electro-optical modulator (10) enters the second optical fiber coupler (11) through the port E1, and the light of a part of the output port E3 of the second optical fiber coupler (11) enters the first photoelectric detector (16) to be converted into an electric signal, and enters the vector network analysis device (19) through the incident port H2 for measurement and demodulation;
the second optical fiber coupler (11) outputs another part of pump light, the pump light enters the second erbium-doped optical fiber amplifier (12) through the emergent port E2 to be amplified, the pump light emergent from the second erbium-doped optical fiber amplifier (12) enters the scrambler (13), the pump light emergent from the scrambler (13) enters the emergent port F2 from the incident port F1 of the first circulator (14), and then enters the second wavelength division multiplexer (15) to be emergent and enter the sensing optical fiber (9) to carry out stimulated Brillouin process;
after the stimulated Brillouin process is carried out in the optical fiber, the detection light carries SBS information, the SBS information passes through the sensing optical fiber (9), enters the first circulator (14) after entering through a port G2 of the second wavelength division multiplexer (15) and exiting from a port G1, enters the second photoelectric detector (17) after exiting from a port F3 of the first circulator (14) and being converted into an electric signal, and enters the vector network analysis device (19) from a port H3 for measurement, and the baseband transmission function of the sensing optical fiber is obtained.
9. The high spatial resolution temperature and strain fiber optic sensing measurement method of claim 7, wherein: the specific steps of the S2 are as follows:
a tunable laser (20) operating at 1550nm has a splitting ratio of 90:10 into two ends, 90% of outgoing light enters the main system through a port I2, and first enters 90 through a port J1: 10, wherein after the detection light emitted from 90% of the exit port J2 of the fourth optical fiber coupler (22) enters the second circulator (23), the detection light is emitted from the port K2 of the second circulator (23), the detection light emitted from the port K2 of the second circulator (23) enters the port G3 of the second wavelength division multiplexer (15) through the first polarization controller (24), the detection light emitted from the port G2 of the second wavelength division multiplexer (15) enters the sensing optical fiber (9), and the detection light of 1550nm emitted from the sensing optical fiber (9) enters the first wavelength division multiplexer (7) from the port C2;
the backward Rayleigh scattering light of 1550nm in the detection optical fiber (9) enters from the port G2 after passing through the second wavelength division multiplexer (15), the backward Rayleigh scattering light emitted from the port G3 of the second wavelength division multiplexer (15) enters into the port K2 of the second circulator (23) through the first polarization controller (24) and exits from the port K3, and enters into the fifth optical fiber coupler (26) through the port L1 to be mixed with reference light;
a 10% emergent port J3 of the fourth optical fiber coupler (22) is used as reference light, the reference light enters the second polarization controller (25) from the incident port, and the second polarization controller (25) enters the fifth optical fiber coupler (26) from the port L2 for mixing with the detection light after emergent;
the tunable laser (20) has a splitting ratio of 90: after the third optical fiber coupler (21) is divided into two ends and exits, 10% of light enters the auxiliary interference system from the exit port I3 and enters the data acquisition system (28) through the triggering interferometer (29) to form a triggering signal.
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