阅读说明：本技术 一种分布式光纤温度与应变同时传感系统 (Distributed optical fiber temperature and strain simultaneous sensing system ) 是由 白清 徐淑婉 梁昌硕 方正 高妍 张红娟 王宇 刘昕 靳宝全 刘香莲 于 2021-07-30 设计创作，主要内容包括：本发明公开了一种分布式光纤温度与应变同时传感系统,具体属于分布式光纤传感技术领域。通过稳频激光器发出稳频光进入两路,一路进入光频域反射系统,一路进入相干光时域反射系统。两路的后向瑞利散射光通过波分复用器解复用完成温度和应变的测量；根据解调出传感光纤中的瑞利散射频移来确定双参量敏感系数,构建双参量传感矩阵,实现温度与应变的同时测量,解决了温度与应变之间的交叉敏感问题；而且对系统进行偏振分集接收处理,可以消除随机偏振态导致可能无法检测到拍频信号的影响,提高系统信噪比；对系统光源的非线性进行增加辅助干涉仪处理,可以消除系统中的相位噪声；从而在提升精度的情况下保证温度与应变的同时测量。(The invention discloses a distributed optical fiber temperature and strain simultaneous sensing system, and particularly belongs to the technical field of distributed optical fiber sensing. The frequency stabilized light emitted by the frequency stabilized laser enters two paths, one path enters the light frequency domain reflection system, and the other path enters the coherent light time domain reflection system. The two paths of backward Rayleigh scattering light are demultiplexed by a wavelength division multiplexer to complete the measurement of temperature and strain; determining double-parameter sensitive coefficients according to the modulated Rayleigh scattering frequency shift in the sensing optical fiber, constructing a double-parameter sensing matrix, realizing simultaneous measurement of temperature and strain, and solving the problem of cross sensitivity between the temperature and the strain; moreover, the polarization diversity receiving processing is carried out on the system, so that the influence that the beat frequency signal possibly cannot be detected due to the random polarization state can be eliminated, and the signal-to-noise ratio of the system is improved; the nonlinearity of the system light source is subjected to additional auxiliary interferometer processing, so that phase noise in the system can be eliminated; thereby guaranteeing simultaneous measurement of temperature and strain under the condition of improving precision.)

1. A distributed fiber optic simultaneous temperature and strain sensing system, comprising:

the device comprises a frequency stabilized laser (1), an optical IQ modulator (2), a bridge (3), an arbitrary waveform generator (4), a first optical fiber coupler (5), a second optical fiber coupler (6), a first optical fiber circulator (7), a wavelength division multiplexer (8), an optical fiber to be detected (9), a third optical fiber coupler (11), a polarization beam splitter (12), a first balanced photoelectric detector (13), a fourth optical fiber coupler (14), a delay optical fiber (15), a fifth optical fiber coupler (17), a photoelectric detector (18), a sixth optical fiber coupler (19), a signal generator (20), an electro-optical modulator (21), a second optical fiber circulator (23), a seventh optical fiber coupler (24), a second balanced photoelectric detector (25), a signal processing device (26) and an eighth optical fiber coupler (28);

the output end of the frequency stabilized laser (1) is connected with the input end of an eighth optical fiber coupler (28), the first output end of the eighth optical fiber coupler (28) is connected with an optical signal input end A of an optical IQ modulator (2), the output end of an arbitrary waveform generator (4) is connected with an input end B of an electric bridge (3), and the output end C and the output end D of the electric bridge (3) are respectively connected with an I phase electric signal input end and a Q phase electric signal input end of the optical IQ modulator (2); the output end of the optical IQ modulator (2) is connected with the input end E of the first optical fiber coupler (5), the output end F of the first optical fiber coupler (5) is connected with the input end of the second optical fiber coupler (6), and the output end G of the first optical fiber coupler (5) is connected with the input end of the fourth optical fiber coupler (14); the output end V of the second optical fiber coupler (6) is connected with the first port J of the first optical fiber circulator (7), and the output end H of the second optical fiber coupler (6) is connected with the input end I of the third optical fiber coupler (11); a second port K of the first optical fiber circulator (7) is connected with a second port of the wavelength division multiplexer (8), and a third port M of the first optical fiber circulator (7) is connected with an input end N of a third optical fiber coupler (11); the output end of the third optical fiber coupler (11) is connected with the input end of the polarization beam splitter (12), two output ends of the polarization beam splitter (12) are respectively connected with the input end O and the input end P of the first balanced photoelectric detector (13), and the output end of the first balanced photoelectric detector (13) is connected with the input end Q of the signal processing device (26); an output end R of the fourth optical fiber coupler (14) is connected with an input end S of the fifth optical fiber coupler (17), an output end T of the fourth optical fiber coupler (14) is connected with an input end U of the fifth optical fiber coupler (17) through a delay optical fiber (15), and an output end of the fifth optical fiber coupler (17) is connected with an input end of the photoelectric detector (18); the output end of the photoelectric detector (18) is connected with the input end W of the signal processing device (26); a second output end of the eighth optical fiber coupler (28) is connected with an input end a of the sixth optical fiber coupler (19), an output end n of the sixth optical fiber coupler (19) is connected with an input end b of the electro-optical modulator (21), an output end of the signal generator (20) is connected with an input end c of the electro-optical modulator (21), an output end d of the electro-optical modulator (21) is connected with a first port e of the second circulator (23), and an output end h of the sixth optical fiber coupler (19) is connected with an input end i of the seventh optical fiber coupler (24); a second port f of the second optical fiber circulator (23) is connected with a first port of the wavelength division multiplexer (8), and the output end of the wavelength division multiplexer (8) is connected with the optical fiber (9) to be tested; a third port g of the second optical fiber circulator (23) is connected with an input end m of a seventh optical fiber coupler (24); two output ends of the seventh optical fiber coupler (24) are respectively connected with an input end j and an input end k of the second balanced photoelectric detector (25), and an output end of the second balanced photoelectric detector (25) is connected with an input end L of the signal processing device (26).

2. The distributed optical fiber temperature and strain simultaneous sensing system according to claim 1, characterized in that the first polarization controller (10) is arranged on a line connecting the output end H of the second optical fiber coupler (6) and the input end I of the third optical fiber coupler (11); and a second polarization controller (16) is arranged on a line connecting the output end R of the fourth optical fiber coupler (14) with the input end S of the fifth optical fiber coupler (17).

3. The distributed optical fiber temperature and strain simultaneous sensing system according to claim 1, characterized in that a continuum optical amplifier (27) is arranged on a line connecting the third port M of the first optical fiber circulator (7) and the input end N of the third optical fiber coupler (11); a pulse light amplifier (22) is arranged on a line connecting the output end d of the electro-optical modulator (21) and the first port e of the second optical fiber circulator (23).

Technical Field

The invention relates to the technical field of distributed optical fiber sensing, in particular to a distributed optical fiber temperature and strain simultaneous sensing system.

Background

In recent years, optical fiber sensors have attracted wide research interest worldwide, and optical fiber sensing technology is widely applied to safety monitoring of large structures such as pipelines and bridges in geological settlement disaster areas due to the advantages of long measuring distance, electromagnetic interference resistance, corrosion resistance and the like. Due to their distributed capabilities, they show advantages over conventional sensors, in the way Optical Time Domain Reflectometry (OTDR) and Optical Frequency Domain Reflectometry (OFDR) have found ways to meet various practical needs. However, OFDR adopts continuous sweep frequency optical detection, has the characteristics of high spatial resolution and large dynamic range, and the sensitivity of the coherent detection scheme is high, so that the spatial resolution of millimeter wave band can be obtained. The OFDR fills the blank of the OTDR in the measurement range, and has important application value in the actual temperature and strain monitoring applications of intelligent materials, structural health monitoring and the like.

However, the distributed optical fiber sensor is sensitive to both strain and temperature, so that temperature change and strain change cannot be distinguished, and errors can be introduced when strain or temperature is monitored. Therefore, in the process of researching an Optical Frequency Domain Reflectometer (OFDR), two parameters of temperature and strain need to be accurately measured, and the problem of cross sensitivity is solved, so that the simultaneous measurement of the temperature and the strain is realized.

Disclosure of Invention

The invention provides a distributed optical fiber temperature and strain simultaneous sensing system which adopts an optical frequency domain reflection system and a coherent optical time domain reflection system. Because the temperature and the strain coefficient of the optical fibers of the two systems are different, the two parameters come from completely different systems and are independent of each other; the method can construct double-parameter matrix operation by measuring Rayleigh frequency shift on the optical fiber to be measured to obtain the temperature and strain values which change at the same time of temperature and strain, thereby solving the problem of cross sensitivity and realizing the simultaneous measurement of temperature and strain. The invention adopts the IQ modulation frequency sweep technology, adopts a double-interference system software phase noise compensation method to inhibit the nonlinearity of a frequency sweep light source, and adopts a polarization diversity receiving system to eliminate the influence of polarization fading, thereby realizing the simultaneous measurement of temperature and strain under high spatial resolution.

The technical scheme adopted by the invention for solving the technical problems is as follows: a distributed fiber optic simultaneous temperature and strain sensing system, comprising:

the device comprises a frequency stabilized laser, an optical IQ modulator, an electric bridge, an arbitrary waveform generator, a first optical fiber coupler, a second optical fiber coupler, a first optical fiber circulator, a wavelength division multiplexer, an optical fiber to be detected, a third optical fiber coupler, a polarization beam splitter, a first balanced photoelectric detector, a fourth optical fiber coupler, a delay optical fiber, a fifth optical fiber coupler, a photoelectric detector, a sixth optical fiber coupler, a signal generator, an electro-optical modulator, a second optical fiber circulator, a seventh optical fiber coupler, a second balanced photoelectric detector, a signal processing device and an eighth optical fiber coupler;

the output end of the frequency stabilized laser is connected with the input end of an eighth optical fiber coupler, the first output end of the eighth optical fiber coupler is connected with an optical signal input end A of an optical IQ modulator, the output end of an arbitrary waveform generator is connected with an input end B of an electric bridge, and an output end C and an output end D of the electric bridge are respectively connected with an I phase electric signal input end and a Q phase electric signal input end of the optical IQ modulator; the output end of the optical IQ modulator is connected with the input end E of the first optical fiber coupler, the output end F of the first optical fiber coupler is connected with the input end of the second optical fiber coupler, and the output end G of the first optical fiber coupler is connected with the input end of the fourth optical fiber coupler; the output end V of the second optical fiber coupler is connected with the first port J of the first optical fiber circulator, and the output end H of the second optical fiber coupler is connected with the input end I of the third optical fiber coupler; a second port K of the first optical fiber circulator is connected with a second port of the wavelength division multiplexer, and a third port M of the first optical fiber circulator is connected with an input end N of a third optical fiber coupler; the output end of the third optical fiber coupler is connected with the input end of the polarization beam splitter, two output ends of the polarization beam splitter are respectively connected with the input end O and the input end P of the first balanced photoelectric detector, and the output end of the first balanced photoelectric detector is connected with the input end Q of the signal processing device; the output end R of the fourth optical fiber coupler is connected with the input end S of the fifth optical fiber coupler, the output end T of the fourth optical fiber coupler is connected with the input end U of the fifth optical fiber coupler through a delay optical fiber, and the output end of the fifth optical fiber coupler is connected with the input end of the photoelectric detector; the output end of the photoelectric detector is connected with the input end W of the signal processing device; a second output end of the eighth optical fiber coupler is connected with an input end a of the sixth optical fiber coupler, an output end n of the sixth optical fiber coupler is connected with an input end b of the electro-optical modulator, an output end of the signal generator is connected with an input end c of the electro-optical modulator, an output end d of the electro-optical modulator is connected with a first port e of the second circulator, and an output end h of the sixth optical fiber coupler is connected with an input end i of the seventh optical fiber coupler; a second port f of the second optical fiber circulator is connected with a first port of the wavelength division multiplexer, and the output end of the wavelength division multiplexer is connected with the optical fiber to be tested; a third port g of the second optical fiber circulator is connected with an input end m of the seventh optical fiber coupler; two output ends of the seventh optical fiber coupler are respectively connected with an input end j and an input end k of the second balanced photoelectric detector, and an output end of the second balanced photoelectric detector is connected with an input end L of the signal processing device.

A first polarization controller is arranged on a circuit connecting the output end H of the second optical fiber coupler and the input end I of the third optical fiber coupler; and a second polarization controller is arranged on a circuit connecting the output end R of the fourth optical fiber coupler with the input end S of the fifth optical fiber coupler.

A continuous optical amplifier is arranged on a line connecting the third port M of the first optical fiber circulator with the input end N of the third optical fiber coupler; and a pulse light amplifier is arranged on a line connecting the output end d of the electro-optical modulator and the first port e of the second optical fiber circulator.

Different from the prior art, the distributed optical fiber temperature and strain simultaneous sensing system disclosed by the invention combines an optical frequency domain reflection system and a coherent optical time domain reflection system, separates backward Rayleigh scattering light with different frequencies in a detection optical fiber through a wavelength division multiplexer, and demodulates the temperature and the strain by adopting the backward Rayleigh scattering spectrum frequency shift of the optical frequency domain reflection system and the coherent optical time domain reflection system, so that the problem of cross sensitivity of temperature and strain sensing is solved, and the problem that the signal-to-noise ratio of the system is deteriorated and the sensing precision and the real-time property are influenced due to phase noise caused by nonlinearity of a sweep frequency light source and polarization fading is also avoided; the invention can optimize the spatial resolution of the system, compensate the phase noise, improve the signal-to-noise ratio, further improve the measurement accuracy of the system and realize high-precision sensing.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a schematic structural diagram of a distributed fiber temperature and strain simultaneous sensing system provided by the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described are only for illustrating the present invention and are not to be construed as limiting the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, the present invention provides a distributed fiber optic simultaneous temperature and strain sensing system, comprising: the device comprises a frequency stabilized laser 1, an optical IQ modulator 2, a bridge 3, an arbitrary waveform generator 4, a first optical fiber coupler 5, a second optical fiber coupler 6, a first optical fiber circulator 7, a wavelength division multiplexer 8, an optical fiber to be measured 9, a third optical fiber coupler 11, a polarization beam splitter 12, a first balanced photodetector 13, a fourth optical fiber coupler 14, a delay optical fiber 15, a fifth optical fiber coupler 17, a photodetector 18, a sixth optical fiber coupler 19, a signal generator 20, an electro-optical modulator 21, a second optical fiber circulator 23, a seventh optical fiber coupler 24, a second balanced photodetector 25, a signal processing device 26 and an eighth optical fiber coupler 28;

the output end of the frequency stabilized laser 1 is connected with the input end of an eighth optical fiber coupler 28, the first output end of the eighth optical fiber coupler 28 is connected with an optical signal input end a of an optical IQ modulator 2, the output end of an arbitrary waveform generator 4 is connected with an input end B of an electric bridge 3, and an output end C and an output end D of the electric bridge 3 are respectively connected with an input end of an I-phase electric signal and an input end of a Q-phase electric signal of the optical IQ modulator 2; the output end of the optical IQ modulator 2 is connected with the input end E of the first optical fiber coupler 5, the output end F of the first optical fiber coupler 5 is connected with the input end of the second optical fiber coupler 6, and the output end G of the first optical fiber coupler 5 is connected with the input end of the fourth optical fiber coupler 14; the output end V of the second optical fiber coupler 6 is connected with the first port J of the first optical fiber circulator 7, and the output end H of the second optical fiber coupler 6 is connected with the input end I of the third optical fiber coupler 11; a second port K of the first optical fiber circulator 7 is connected with a second port of the wavelength division multiplexer 8, and a third port M of the first optical fiber circulator 7 is connected with an input end N of a third optical fiber coupler 11; the output end of the third optical fiber coupler 11 is connected to the input end of the polarization beam splitter 12, two output ends of the polarization beam splitter 12 are respectively connected to the input end O and the input end P of the first balanced photodetector 13, and the output end of the first balanced photodetector 13 is connected to the input end Q of the signal processing device 26; an output end R of the fourth optical fiber coupler 14 is connected with an input end S of the fifth optical fiber coupler 17, an output end T of the fourth optical fiber coupler 14 is connected with an input end U of the fifth optical fiber coupler 17 through a delay optical fiber 15, and an output end of the fifth optical fiber coupler 17 is connected with an input end of a photoelectric detector 18; the output end of the photodetector 18 is connected with the input end W of the signal processing device 26; a second output end of the eighth optical fiber coupler 28 is connected to the input end a of the sixth optical fiber coupler 19, the output end n of the sixth optical fiber coupler 19 is connected to the input end b of the electro-optical modulator 21, the output end of the signal generator 20 is connected to the input end c of the electro-optical modulator 21, the output end d of the electro-optical modulator 21 is connected to the first port e of the second circulator 23, and the output end h of the sixth optical fiber coupler 19 is connected to the input end i of the seventh optical fiber coupler 24; a second port f of the second optical fiber circulator 23 is connected with a first port of the wavelength division multiplexer 8, and the output end of the wavelength division multiplexer 8 is connected with the optical fiber 9 to be tested; the third port g of the second optical fiber circulator 23 is connected with the input end m of the seventh optical fiber coupler 24; two output ends of the seventh optical fiber coupler 24 are respectively connected to the input end j and the input end k of the second balanced photodetector 25, and an output end of the second balanced photodetector 25 is connected to the input end L of the signal processing device 26.

A first polarization controller 10 is arranged on a circuit connecting the output end H of the second optical fiber coupler 6 and the input end I of the third optical fiber coupler 11; a second polarization controller 16 is arranged on a line connecting the output end R of the fourth optical fiber coupler 14 with the input end S of the fifth optical fiber coupler 17.

Wherein, a continuous optical amplifier 27 is arranged on a line connecting the third port M of the first optical fiber circulator 7 and the input end N of the third optical fiber coupler 11; a pulsed light amplifier 22 is provided on a line connecting the output end d of the electro-optical modulator 21 and the first port e of the second fiber circulator 23.

The working principle of the invention is as follows: the invention uses a frequency stabilized laser 1 to send out frequency stabilized light to enter two paths, one path is modulated into pulse light by an electro-optic modulator 21 to enter an optical fiber to be tested (coherent light time domain reflection system), and the other path is modulated into frequency swept light by an optical IQ modulator 2 to enter the optical fiber to be tested (optical frequency domain reflection system); the two paths of backward Rayleigh scattering light are demultiplexed by a wavelength division multiplexer 8 to finish the measurement of temperature and strain; after the beat frequency is carried out on the reference light and the reference light, the double-parameter sensitive coefficient is determined according to the Rayleigh dispersion frequency shift in the demodulated sensing optical fiber, a double-parameter sensing matrix is constructed, the simultaneous measurement of temperature and strain is realized, and the problem of cross sensitivity between the temperature and the strain is solved; moreover, the polarization diversity receiving processing is carried out on the system, so that the influence that the beat frequency signal possibly cannot be detected due to the random polarization state can be eliminated, and the signal-to-noise ratio of the system is improved; the nonlinearity of the system light source is subjected to additional auxiliary interferometer processing, so that phase noise in the system can be eliminated; thereby guaranteeing simultaneous measurement of temperature and strain under the condition of improving precision.

The following describes an embodiment of the present invention with reference to fig. 1: as shown in fig. 1, the frequency stabilized laser 1 emits frequency stabilized narrow band laser with a wavelength of 1550nm, and is divided into two paths by the eighth optical fiber coupler 28. One path enters an optical frequency domain reflection system, and a first output port of the eighth optical fiber coupler 28 outputs 1550nm frequency-stabilized light to an optical input end a of the optical IQ modulator 2 to serve as an optical carrier of the optical IQ modulator 2; the arbitrary waveform generator 4 periodically sends out a sweep frequency signal with constant amplitude, continuous phase and linear frequency change along with time, the signal is output to an input end B of the electric bridge 3, is converted into two signals with same frequency, same amplitude and mutually orthogonal phase through the electric bridge 3, and is respectively output to the optical IQ modulator 2 from an output end C and an output end D to be respectively used as I, Q phase modulation electric signals of the optical IQ modulator 2; the optical IQ modulator 2 modulates the frequency-stabilized optical carrier into single-sideband suppressed carrier frequency-swept light (12.8-16 Ghz) under the control of the modulation electric signal; the swept-frequency light is output to an input end E of the first fiber coupler 5, and is divided into 90% main interference light and 10% auxiliary interference light by the first fiber coupler 5.

The main interference light is output to the input end of the second optical fiber coupler 6 through the port F of the first optical fiber coupler 5, is divided into 90% detection light and 10% reference light through the second optical fiber coupler 6, the detection light is input to the first port J of the first optical fiber circulator 7, is output from the second port K of the first optical fiber circulator 7, enters the optical fiber 9 to be detected through the wavelength division multiplexer 8, and the reference light is output to the input port I of the third optical fiber coupler 11 through the first polarization controller 10. The backward scattering light returned by the optical fiber 9 to be measured is output to the second port K of the first optical fiber circulator 7 through the wavelength division multiplexer 8, and is output to the input port N of the third optical fiber coupler 11 from the third port M of the first optical fiber circulator 7 through the continuous light amplifier 27. The backward scattered light from the fiber under test at the input port N and the reference light from the input port I are combined into a main interference combined light at a ratio of 50:50 at the third fiber coupler 11 and output to the polarization beam splitter 12. The main interference combined light is divided into two beams of light with mutually orthogonal polarization states, namely S light and P light, in the polarization beam splitter 12, wherein the fast axis component of the main interference combined light is formed by combining the fast axis component of the backward scattering light of the optical fiber to be detected and the fast axis component of the reference light and is output to the input port O of the first balanced photoelectric detector 13; the slow axis component of the main interference combined light is formed by combining the slow axis component of the backward scattering light of the optical fiber to be detected and the slow axis component of the reference light, and is output to the input port P of the first balanced photodetector 13. In the first balanced photoelectric detector 13, the fast axis component of the backward scattering light of the optical fiber to be detected and the fast axis component of the reference light generate coherent beat frequency and are converted into electric signals, and a main interference fast axis beat frequency signal is obtained; and the slow axis component of the backward scattering light of the optical fiber to be detected and the slow axis component of the reference light generate coherent beat frequency and are converted into electric signals, so that main interference slow axis beat frequency signals are obtained. By adjusting the first polarization controller 10, after the power of the main interference fast axis beat signal and the power of the main interference slow axis beat signal are close to each other, the square of the main interference fast axis beat signal of the first balanced photodetector 13 and the square of the main interference slow axis beat signal of the first balanced photodetector 13 are summed and output to the signal processing device 26, so that polarization diversity reception of two orthogonal polarized lights is realized, the signal-to-noise ratio deterioration caused by polarization fading is reduced, and the signal-to-noise ratio of the system is improved. The signal processing device 26 receives the signal from the main interference system from the input port Q, and performs demodulation and analysis to obtain the distributed temperature and strain information of the optical fiber to be measured, thereby realizing simultaneous measurement of temperature and strain.

The other path enters a coherent optical time domain reflection system, a second output port of the eighth optical fiber coupler 28 outputs 1550nm frequency-stabilized light to an input end a of a sixth optical fiber coupler 19, and the frequency-stabilized light is divided into 99% detection light and 10% reference light by the sixth optical fiber coupler 19; the n port of the sixth optical fiber coupler 19 outputs the probe light to the optical input end b of the electro-optical modulator 21 for frequency shift (200 Mhz), so as to facilitate subsequent collection; meanwhile, the signal generator 20 sends out pulse signals with constant amplitude, constant frequency and constant pulse width to be input into a port c of the electro-optical modulator 21, and the electro-optical modulator 21 modulates the frequency-stabilized light waves into pulse signals under the control of electric signals and outputs the pulse signals from a port d of the electro-optical modulator 21; then, after being amplified by the pulse light amplifier 22, the signal is input to the first port e of the second optical fiber circulator 23, is output from the second port f of the second optical fiber circulator 23 and enters the optical fiber 9 to be tested through the wavelength division multiplexer 8, and the backscattered light returned by the optical fiber 9 to be tested is output to the second port f of the second optical fiber circulator 23 through the wavelength division multiplexer 8 and is output to the input port m of the seventh optical fiber coupler 24 from the third port g of the second optical fiber circulator 23; the sixth optical fiber coupler 19 outputs the reference light to an input port i of the seventh optical fiber coupler 24 to perform beat frequency on the backward scattering light returned by the optical fiber to be detected; the beat frequency signal is output to the second balanced detector 25, converted into an electric signal, and then input to the input port L of the signal processing device 26, and is demodulated and analyzed in the signal processing device 26 to obtain the distributed temperature and strain information of the optical fiber to be measured, so that the simultaneous measurement of temperature and strain is realized.

The K port of the first optical fiber circulator 7 and the f port of the second optical fiber circulator 23 are both connected with the wavelength division multiplexer 8, so that simultaneous detection and simultaneous measurement of the two systems are realized. The problem of cross sensitivity can be solved by respectively acquiring signals obtained by connecting two systems with the same optical fiber 9 to be measured and demodulating the signals, so that the simultaneous measurement of temperature and strain is realized.

Demodulating a result by combining an optical frequency domain reflection system and a coherent optical time domain reflection system, deriving a double-parameter sensitive coefficient, and constructing a double-parameter sensing matrix; and further analyzing the influence of the two systems on the sensitivity coefficient, verifying the sensitivity coefficient, calibrating and correcting, and finally realizing simultaneous measurement of temperature and strain. Respectively demodulating Rayleigh scattering spectrum frequency shift of the sensing optical fiber by using an optical frequency domain reflection system and a coherent optical time domain reflection system, and calibrating the optical fiber to be detected at different temperatures and strains; obtaining the temperature sensing coefficients of two systems at different temperature calibration curvesAndobtaining strain sensing coefficient from calibration curve of different strainAnd(ii) a When the temperature and the strain change simultaneously in the actual measurement, the Rayleigh scattering spectrum frequency shift is demodulated by using the optical frequency domain reflection systemThe frequency shift of Rayleigh scattering spectrum is demodulated by using a coherent optical time domain reflection systemThe corresponding temperature change is obtained by using the following relationshipChange in strain of：

The auxiliary interference light is output to the fourth optical fiber coupler 14 through the G port of the first optical fiber coupler 5, and is divided into standard light and delay light in a ratio of 50:50 through the fourth optical fiber coupler 14. Wherein, the standard light is output from the R port of the fourth fiber coupler 14 to the input port S of the fifth fiber coupler 17 through the second polarization controller 16. The delayed light is output from the T port of the fourth fiber coupler 14 to the input port U of the fifth fiber coupler 17 through the delay fiber 15, and the normal light and the delayed light are combined again at the fifth fiber coupler 17 in a ratio of 50:50 to be auxiliary interference combined light. The auxiliary interference combined light is output from the output port of the fifth optical fiber coupler 17 to the input port W of the signal processing device 26 through the photodetector 18. The signal processing device 26 receives the signal from the auxiliary interference system from the input port W and analyzes the signal to obtain system phase noise information to compensate for the phase noise from the main interference system signal, thereby reducing the system phase noise.

While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.