Distributed optical fiber sensing system capable of simultaneously measuring temperature, strain and vibration

Abstract

The utility model discloses a distributed optical fiber sensing system capable of simultaneously measuring temperature, strain and vibration, and relates to the technical field of optical fiber sensing. The system comprises a narrow linewidth laser, an optical fiber coupler, an electro-optical modulator, an optical fiber circulator, a polarization maintaining fiber bragg grating, a semiconductor optical amplifier, a random scrambler, a delay optical fiber, an erbium-doped optical fiber amplifier, an adjustable grating filter, an optical attenuator, a photoelectric balance detector, a photoelectric detector, a data acquisition card, an arbitrary waveform generator, a direct-current power supply and the like. The system provided by the utility model can realize simultaneous detection of vibration, temperature / strain along the line through a single sensing optical fiber; the device has the advantages of high fusion degree and low cost, cross aliasing and power competition between pulse light are effectively avoided, and simultaneous measurement of multiple parameters is achieved; the system is high in fusion degree and low in cost.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fiber sensing, in particular to a distributed optical fiber sensing system for simultaneously measuring temperature, strain and vibration. Background Art

[0002] Distributed optical fiber sensors (DOFS) offer the unique advantage of distributed, continuous measurement over traditional point sensors, and hold broad application prospects in industrial monitoring. Distributed optical fiber sensors based on Brillouin scattering can only measure temperature and strain signals along the sensing fiber; those based on Raman scattering can only measure temperature signals along the sensing fiber; and those based on Rayleigh scattering can only measure vibration signals along the sensing fiber. Regardless of the type of DOFS used, the measurement parameters (typically temperature, strain, or vibration) are relatively limited. However, in industrial monitoring, coordinated multi-parameter measurements are urgently needed to accurately identify fault events. Utility Model Content

[0003] In view of the above problems, the present invention proposes a distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration.

[0004] A distributed fiber optic sensing system for simultaneous measurement of temperature, strain, and vibration comprises: a narrow linewidth laser 1, a first fiber coupler 2, a first electro-optic modulator 3, a first fiber circulator 4, a polarization-maintaining fiber Bragg grating 5, a first semiconductor optical amplifier 6, a random polarization scrambler 7, a second electro-optic modulator 8, a second fiber coupler 9, a time-delay fiber 10, a second semiconductor optical amplifier 11, a third fiber coupler 12, a first erbium-doped fiber amplifier 13, a second fiber circulator 14, a third electro-optic modulator 15, a tunable grating filter 16, a second erbium-doped fiber amplifier 17, a fourth fiber coupler 18, an optical attenuator 19, a fifth fiber coupler 20, a photoelectric balanced detector 21, a photoelectric detector 22, a data acquisition card 23, an arbitrary waveform generator 24, and a DC power supply 25; wherein,

[0005] The optical signal output end of the narrow linewidth laser 1 is connected to the optical signal input end of the first fiber coupler 2, and the optical signal output end of the first fiber coupler 2 is respectively connected to the optical signal input end of the first electro-optical modulator 3, the optical signal input end of the optical attenuator 19, and the optical signal input end of the second electro-optical modulator 8;

[0006] The optical signal output end of the first electro-optical modulator 3 is connected to the first port 4-1 of the first optical fiber circulator 4, the second port 4-2 of the first optical fiber circulator 4 is connected to the polarization-maintaining fiber Bragg grating 5, the third port 4-3 of the first optical fiber circulator 4 is connected to the optical signal input end of the first semiconductor optical amplifier 6, the optical signal output end of the first semiconductor optical amplifier 6 is connected to the optical signal input end of the random polarization scrambler 7, and the optical signal output end of the random polarization scrambler 7 is connected to the optical signal input end of the third optical fiber coupler 12;

[0007] An optical signal output end of the second electro-optical modulator 8 is connected to an optical signal input end of the second fiber coupler 9, and an optical signal output end of the second fiber coupler 9 is respectively connected to one end of a delay fiber 10 and an optical signal input end of a third electro-optical modulator 15. The other end of the delay fiber 10 is connected to an optical signal input end of a second semiconductor optical amplifier 11, and an optical signal output end of the second semiconductor optical amplifier 11 is connected to an optical signal input end of a third fiber coupler 12. An optical signal output end of the third electro-optical modulator 15 is connected to an optical signal input end of a tunable grating filter 16, and an optical signal output end of the tunable grating filter 16 is connected to an optical signal input end of a second erbium-doped fiber amplifier 17. An optical signal output end of the second erbium-doped fiber amplifier 17 is connected to one end of a sensing fiber.

[0008] The optical signal output end of the third fiber coupler 12 is connected to the optical signal input end of the first erbium-doped fiber amplifier 13, the optical signal output end of the first erbium-doped fiber amplifier 13 is connected to the first port 14-1 of the second fiber circulator 14, and the second port 14-2 of the second fiber circulator 14 is connected to the other end of the sensing fiber; the third port 14-3 of the second fiber circulator 14 is connected to the optical signal input end of the fourth fiber coupler 18, and the optical signal output end of the fourth fiber coupler 18 is respectively connected to the optical signal input end of the fifth fiber coupler 20 and the optical signal input end of the photodetector 22;

[0009] The optical signal output end of the optical attenuator 19 is connected to the optical signal input end of the fifth optical fiber coupler 20, the optical signal output end of the fifth optical fiber coupler 20 is connected to the optical signal input end of the photoelectric balance detector 21, and the electrical signal output end of the photoelectric balance detector 21 and the electrical signal output end of the photoelectric detector 22 are respectively connected to the data acquisition card 23;

[0010] The RF output terminal of the arbitrary waveform generator 24 is respectively connected to the RF signal input terminal of the first electro-optical modulator 3, the RF signal input terminal of the first semiconductor optical amplifier 6, the RF signal input terminal of the second electro-optical modulator 8, the RF signal input terminal of the second semiconductor optical amplifier 11, the RF signal input terminal of the third electro-optical modulator 15, and the trigger signal input terminal of the data acquisition card 23;

[0011] The output end of the DC power supply 25 is connected to the bias voltage input end of the first electro-optical modulator 3 , the bias voltage input end of the second electro-optical modulator 8 , and the bias voltage input end of the third electro-optical modulator 15 , respectively.

[0012] Furthermore, the narrow linewidth laser 1 is a polarization-maintaining laser with an output power of 40 mW, a wavelength of 1550.14 nm, and a linewidth of 1 kHz.

[0013] Furthermore, the first fiber coupler 2 is a 1×3 polarization-maintaining coupler with a splitting ratio of 33:33:33; the second fiber coupler 9 and the third fiber coupler 12 are 1×2 polarization-maintaining couplers with a splitting ratio of 50:50; the fourth fiber coupler 19 is a 1×2 coupler with a splitting ratio of 50:50; and the fifth fiber coupler 21 is a 2×2 coupler with a splitting ratio of 50:50.

[0014] Furthermore, the first electro-optical modulator 3 and the third electro-optical modulator 16 are polarization-maintaining modulators with a bandwidth of 10 GHz and an extinction ratio of 30 dB; the second electro-optical modulator 8 is a polarization-maintaining modulator with a bandwidth of 2 GHz and an extinction ratio of 30 dB.

[0015] Furthermore, the central wavelength of the polarization-maintaining fiber Bragg grating 5 is 1550.08 nm, and the 3 dB reflection bandwidth is 0.08 nm.

[0016] Furthermore, the extinction ratios of the first semiconductor optical amplifier 6 and the second semiconductor optical amplifier 11 are both 45 dB.

[0017] Furthermore, the 3dB operating bandwidth of the photoelectric balanced detector 22 is 2 GHz.

[0018] Furthermore, the 3dB operating bandwidth of the photodetector 23 is 100 MHz.

[0019] Furthermore, the data acquisition card 24 has a sampling rate of 5 GS / s and a sampling resolution of 14 bits.

[0020] The beneficial technical effects of the utility model are:

[0021] The OCC-BOTDA (Optical Chirp Chain Brillouin Optical Time-Domain Analysis) system is a Brillouin optical time-domain analysis (BOTDA) system based on the optical chirp chain (OCC) technology; the TGD-OFDR (Time-gated Digital Optical Frequency Domain Reflectometry) system is a time-gated digital optical frequency domain reflectometer. The utility model proposes a distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration, which can realize simultaneous and rapid measurement of multiple parameters: the OCC-BOTDA system uses an optical chirp chain as the detection light, and the measurement speed of the temperature and strain signals is limited to the length of the sensing fiber and the average number of the Brillouin gain curve. The measurement speed of the vibration signal of the TGD-OFDR system is only limited to the length of the sensing fiber; the fusion of the OCC-BOTDA system and the TGD-OFDR system can simultaneously measure the temperature, strain and vibration through a single sensing fiber. It realizes simultaneous detection of vibration, temperature / strain along the line; it has the advantages of high integration and low cost: the chirped pulse light of the TGD-OFDR system and the detection light of the OCC-BOTDA system in the system are both realized by secondary modulation based on the double-sideband optical chirp chain modulated by the same modulator; the pump pulse light of the OCC-BOTDA system and the chirped pulse light of the TGD-OFDR system are controlled by time division-frequency division multiplexing technology and injected into the same sensing optical fiber in sequence, effectively avoiding cross-aliasing and power competition between the pulse lights while realizing simultaneous measurement of multiple parameters; the system has high integration and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, in which:

[0023] Figure 1 This is a schematic structural diagram of a distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to an embodiment of the present utility model;

[0024] Figure 2 This is an example diagram of the time-varying process of the vibration phase information measured by the TGD-OFDR system in an embodiment of the present utility model;

[0025] Figure 3 This is an example diagram of the vibration phase information spectrum measured by the TGD-OFDR system in an embodiment of the present utility model;

[0026] Figure 4This is an example diagram of strain information measured by the OCC-BOTDA system in an embodiment of the present utility model. DETAILED DESCRIPTION

[0027] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided solely to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the scope of the present invention in any way. Rather, these embodiments are provided to make this disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0028] In order to solve the problem that coordinated multi-parameter measurement is urgently needed in industrial monitoring, but distributed optical fiber sensors can measure few parameters simultaneously, the utility model proposes a distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration.

[0029] like Figure 1 As shown, the system includes: a narrow linewidth laser 1, a first fiber coupler 2, a first electro-optic modulator 3, a first fiber circulator 4, a polarization-maintaining fiber Bragg grating 5, a first semiconductor optical amplifier 6, a random polarization scrambler 7, a second electro-optic modulator 8, a second fiber coupler 9, a delay fiber 10, a second semiconductor optical amplifier 11, a third fiber coupler 12, a first erbium-doped fiber amplifier 13, a second fiber circulator 14, a third electro-optic modulator 15, a tunable grating filter 16, a second erbium-doped fiber amplifier 17, a fourth fiber coupler 18, an optical attenuator 19, a fifth fiber coupler 20, a photoelectric balanced detector 21, a photoelectric detector 22, a data acquisition card 23, an arbitrary waveform generator 24, and a DC power supply 25; wherein,

[0030] The optical signal output end of the narrow linewidth laser 1 is connected to the optical signal input end of the first fiber coupler 2, and the optical signal output end of the first fiber coupler 2 is respectively connected to the optical signal input end of the first electro-optical modulator 3, the optical signal input end of the optical attenuator 19, and the optical signal input end of the second electro-optical modulator 8;

[0031] The optical signal output end of the first electro-optical modulator 3 is connected to the first port 4-1 of the first optical fiber circulator 4, the second port 4-2 of the first optical fiber circulator 4 is connected to the polarization-maintaining fiber Bragg grating 5, the third port 4-3 of the first optical fiber circulator 4 is connected to the optical signal input end of the first semiconductor optical amplifier 6, the optical signal output end of the first semiconductor optical amplifier 6 is connected to the optical signal input end of the random polarization scrambler 7, and the optical signal output end of the random polarization scrambler 7 is connected to the optical signal input end of the third optical fiber coupler 12;

[0032] An optical signal output end of the second electro-optical modulator 8 is connected to an optical signal input end of the second fiber coupler 9, and an optical signal output end of the second fiber coupler 9 is respectively connected to one end of a delay fiber 10 and an optical signal input end of a third electro-optical modulator 15. The other end of the delay fiber 10 is connected to an optical signal input end of a second semiconductor optical amplifier 11, and an optical signal output end of the second semiconductor optical amplifier 11 is connected to an optical signal input end of a third fiber coupler 12. An optical signal output end of the third electro-optical modulator 15 is connected to an optical signal input end of a tunable grating filter 16, and an optical signal output end of the tunable grating filter 16 is connected to an optical signal input end of a second erbium-doped fiber amplifier 17. An optical signal output end of the second erbium-doped fiber amplifier 17 is connected to one end of a sensing fiber.

[0033] The optical signal output end of the third fiber coupler 12 is connected to the optical signal input end of the first erbium-doped fiber amplifier 13, the optical signal output end of the first erbium-doped fiber amplifier 13 is connected to the first port 14-1 of the second fiber circulator 14, and the second port 14-2 of the second fiber circulator 14 is connected to the other end of the sensing fiber; the third port 14-3 of the second fiber circulator 14 is connected to the optical signal input end of the fourth fiber coupler 18, and the optical signal output end of the fourth fiber coupler 18 is respectively connected to the optical signal input end of the fifth fiber coupler 20 and the optical signal input end of the photodetector 22;

[0034] The optical signal output end of the optical attenuator 19 is connected to the optical signal input end of the fifth optical fiber coupler 20, the optical signal output end of the fifth optical fiber coupler 20 is connected to the optical signal input end of the photoelectric balance detector 21, and the electrical signal output end of the photoelectric balance detector 21 and the electrical signal output end of the photoelectric detector 22 are respectively connected to the data acquisition card 23;

[0035] The RF output terminal of the arbitrary waveform generator 24 is respectively connected to the RF signal input terminal of the first electro-optical modulator 3, the RF signal input terminal of the first semiconductor optical amplifier 6, the RF signal input terminal of the second electro-optical modulator 8, the RF signal input terminal of the second semiconductor optical amplifier 11, the RF signal input terminal of the third electro-optical modulator 15, and the trigger signal input terminal of the data acquisition card 23;

[0036] The output end of the DC power supply 25 is connected to the bias voltage input end of the first electro-optical modulator 3 , the bias voltage input end of the second electro-optical modulator 8 , and the bias voltage input end of the third electro-optical modulator 15 , respectively.

[0037] In this embodiment, preferably, the narrow linewidth laser 1 is a polarization-maintaining laser with an output power of 40 mW, a wavelength of 1550.14 nm, and a linewidth of 1 kHz.

[0038] In this embodiment, preferably, the first fiber coupler 2 is a 1×3 polarization-maintaining coupler with a splitting ratio of 33:33:33; the second fiber coupler 9 and the third fiber coupler 12 are 1×2 polarization-maintaining couplers with a splitting ratio of 50:50; the fourth fiber coupler 19 is a 1×2 coupler with a splitting ratio of 50:50; and the fifth fiber coupler 21 is a 2×2 coupler with a splitting ratio of 50:50.

[0039] In this embodiment, preferably, the first electro-optical modulator 3 and the third electro-optical modulator 16 are polarization-maintaining modulators with a bandwidth of 10 GHz and an extinction ratio of 30 dB; the second electro-optical modulator 8 is a polarization-maintaining modulator with a bandwidth of 2 GHz and an extinction ratio of 30 dB.

[0040] In this embodiment, preferably, the central wavelength of the polarization-maintaining fiber Bragg grating 5 is 1550.08 nm, and the 3 dB reflection bandwidth is 0.08 nm.

[0041] In this embodiment, preferably, the extinction ratios of the first semiconductor optical amplifier 6 and the second semiconductor optical amplifier 11 are both 45 dB.

[0042] In this embodiment, preferably, the 3dB operating bandwidth of the photoelectric balance detector 22 is 2 GHz, and the 3dB operating bandwidth of the photoelectric detector 23 is 100 MHz.

[0043] In this embodiment, preferably, the sampling rate of the data acquisition card 24 is 5 GS / s and the sampling resolution is 14 bits.

[0044] In this embodiment, preferably, the working process of a distributed optical fiber sensing system for simultaneous measurement of temperature, strain, and vibration is as follows:

[0045] The single-frequency continuous light output by the narrow-linewidth laser 1 is divided into three paths: upper, middle, and lower paths by the first fiber coupler 2. The upper path light is used as the pump pulse light modulation of the OCC-BOTDA system; the middle path light is used as the reference light of the TGD-OFDR system; and the lower path light is used to modulate the optical chirp chain. After being split, it is used as the detection pulse light modulation of the TGD-OFDR system and as the detection light of the OCC-BOTDA system.

[0046] The added continuous light is intensity modulated by the first electro-optical modulator 3, and the frequency shift is controlled by the arbitrary waveform generator 24. The double-sideband continuous light, after the carrier frequency is suppressed by the DC power supply 25, is injected into the polarization-maintaining fiber Bragg grating 5 by the first fiber circulator 4 to filter out the lower sideband. The remaining upper sideband continuous light is periodically modulated into pulse light by the first semiconductor optical amplifier 6, and the polarization state is disrupted by the random polarization scrambler 7 to serve as the pump pulse light of the OCC-BOTDA system.

[0047] The lower continuous light is linearly swept modulated by the second electro-optical modulator 8, and the sweep range is controlled by the arbitrary waveform generator 24. The DC power supply 25 suppresses the carrier frequency component to achieve double-sideband swept modulation. The modulated continuous light is divided into two upper and lower branches by the second fiber coupler 9: the upper branch is injected into the second semiconductor optical amplifier 11 through the delay fiber 10 and periodically modulated into positive and negative chirped pulse light, which serves as the detection pulse light of the TGD-OFDR system. It is then combined with the pump pulse light through the third fiber coupler 12 and power pre-amplified by the first erbium-doped fiber amplifier 13, and finally transmitted through the second fiber ring The double-sideband swept continuous light of the lower branch is frequency-shift modulated by the third electro-optical modulator 15, and the high-frequency optical chirp chain filtered out by the tunable grating filter 16 is used as the detection light of the OCC-BOTDA system. After power pre-amplification by the second erbium-doped fiber amplifier 17, it is reversely injected into the sensing fiber. The frequency difference between the detection light and the pump pulse light is approximately equal to the Brillouin frequency shift. Due to the stimulated Brillouin scattering effect, when the high-frequency detection light meets the pump pulse light, part of the energy of the high-frequency detection light will pass through the acoustic wave field to the pump pulse light. The energy transfer is maximized when the frequency difference between the two is equal to the Brillouin frequency shift.

[0048] The backscattered Rayleigh light and high-frequency continuous light in the sensing fiber enter the fourth fiber coupler 18 through the second fiber circulator 14 and are divided into two parts. One part, combined with the mid-path continuous light after power adjustment by the optical attenuator 19, enters the fifth fiber coupler 20 for coherent frequency beat. The light is then converted to photoelectricity by a photoelectric balanced detector 21 and recorded by a data acquisition card 23 as the sensing signal for the TGD-OFDR system, used to detect vibration information in the external environment along the sensing fiber. The other part is converted to photoelectricity by a photoelectric detector 22 and recorded by a data acquisition card 23 as the sensing signal for the OCC-BOTDA system, used to detect temperature and strain information in the external environment along the sensing fiber. Ultimately, the system achieves simultaneous measurement of ambient temperature, strain, and vibration within a single sensing fiber, meeting the urgent need for collaborative multi-parameter measurement in industrial monitoring.

[0049] This utility model proposes a DOFS system that integrates multiple scattering mechanisms, enabling the measurement of multiple parameters along the sensing fiber. This highly integrated sensing structure can effectively reduce sensor costs and can be more efficiently used in industrial monitoring fields. Figure 2 This is an example diagram of the time-varying process of the vibration phase information measured by the TGD-OFDR system in the system. The corresponding spectrum is Figure 3 , it can be seen that the frequency of the vibration signal is 40.1Hz. Figure 4 This is the strain information measured by the OCC-BOTDA system in the system, and the strain magnitude is 600με.

[0050] The utility model proposes a distributed fiber optic sensing system for simultaneous measurement of temperature, strain and vibration, which can realize simultaneous and rapid measurement of multiple parameters: the OCC-BOTDA system uses an optical chirp chain as the detection light, and the measurement speed of temperature and strain signals is limited only by the length of the sensing fiber and the average number of Brillouin gain curves; the measurement speed of the vibration signal of the TGD-OFDR system is only limited by the length of the sensing fiber; the fusion of the OCC-BOTDA system and the TGD-OFDR system can realize the simultaneous detection of vibration and temperature / strain along the line through a single sensing fiber. It has the advantages of high integration and low cost: the chirped pulse light of the TGD-OFDR system and the detection light of the OCC-BOTDA system in the system are both realized by secondary modulation based on the double-sideband optical chirp chain modulated by the same modulator; the pump pulse light of the OCC-BOTDA system and the chirped pulse light of the TGD-OFDR system are controlled by time division-frequency division multiplexing technology and injected into the same sensing optical fiber in sequence, effectively avoiding cross-aliasing and power competition between the pulse lights while realizing simultaneous measurement of multiple parameters; the system has high integration and low cost.

[0051] Although the spirit and principles of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the specific embodiments disclosed, and the division into various aspects does not mean that the features of these aspects cannot be combined to benefit. Such division is merely for the convenience of expression. The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration, characterized in that: include: A narrow linewidth laser (1), a first fiber coupler (2), a first electro-optic modulator (3), a first fiber circulator (4), a polarization-maintaining fiber Bragg grating (5), a first semiconductor optical amplifier (6), a random polarization scrambler (7), a second electro-optic modulator (8), a second fiber coupler (9), a time-delay fiber (10), a second semiconductor optical amplifier (11), a third fiber coupler (12), a first erbium-doped fiber amplifier (13), a second fiber circulator (14), a third electro-optic modulator (15), a tunable grating filter (16), a second erbium-doped fiber amplifier (17), a fourth fiber coupler (18), an optical attenuator (19), a fifth fiber coupler (20), a photoelectric balanced detector (21), a photoelectric detector (22), a data acquisition card (23), an arbitrary waveform generator (24), and a DC power supply (25); wherein, The optical signal output end of the narrow linewidth laser (1) is connected to the optical signal input end of the first optical fiber coupler (2), and the optical signal output end of the first optical fiber coupler (2) is respectively connected to the optical signal input end of the first electro-optical modulator (3), the optical signal input end of the optical attenuator (19), and the optical signal input end of the second electro-optical modulator (8); The optical signal output end of the first electro-optical modulator (3) is connected to the first port (4-1) of the first optical fiber circulator (4), the second port (4-2) of the first optical fiber circulator (4) is connected to the polarization-maintaining fiber Bragg grating (5), the third port (4-3) of the first optical fiber circulator (4) is connected to the optical signal input end of the first semiconductor optical amplifier (6), the optical signal output end of the first semiconductor optical amplifier (6) is connected to the optical signal input end of the random polarization scrambler (7), and the optical signal output end of the random polarization scrambler (7) is connected to the optical signal input end of the third optical fiber coupler (12); The optical signal output end of the second electro-optical modulator (8) is connected to the optical signal input end of the second optical fiber coupler (9), the optical signal output end of the second optical fiber coupler (9) is respectively connected to one end of the delay optical fiber (10) and the optical signal input end of the third electro-optical modulator (15), the other end of the delay optical fiber (10) is connected to the optical signal input end of the second semiconductor optical amplifier (11), and the optical signal output end of the second semiconductor optical amplifier (11) is connected to the optical signal input end of the third optical fiber coupler (12); The optical signal output end of the third electro-optical modulator (15) is connected to the optical signal input end of the tunable grating filter (16), the optical signal output end of the tunable grating filter (16) is connected to the optical signal input end of the second erbium-doped fiber amplifier (17), and the optical signal output end of the second erbium-doped fiber amplifier (17) is connected to one end of the sensing optical fiber; The optical signal output end of the third optical fiber coupler (12) is connected to the optical signal input end of the first erbium-doped optical fiber amplifier (13), the optical signal output end of the first erbium-doped optical fiber amplifier (13) is connected to the first port (14-1) of the second optical fiber circulator (14), and the second port (14-2) of the second optical fiber circulator (14) is connected to the other end of the sensing optical fiber; the third port (14-3) of the second optical fiber circulator (14) is connected to the optical signal input end of the fourth optical fiber coupler (18), and the optical signal output end of the fourth optical fiber coupler (18) is respectively connected to the optical signal input end of the fifth optical fiber coupler (20) and the optical signal input end of the photodetector (22); The optical signal output end of the optical attenuator (19) is connected to the optical signal input end of the fifth optical fiber coupler (20), the optical signal output end of the fifth optical fiber coupler (20) is connected to the optical signal input end of the photoelectric balance detector (21), and the electrical signal output end of the photoelectric balance detector (21) and the electrical signal output end of the photoelectric detector (22) are respectively connected to the data acquisition card (23); The radio frequency output end of the arbitrary waveform generator (24) is respectively connected to the radio frequency signal input end of the first electro-optical modulator (3), the radio frequency signal input end of the first semiconductor optical amplifier (6), the radio frequency signal input end of the second electro-optical modulator (8), the radio frequency signal input end of the second semiconductor optical amplifier (11), the radio frequency signal input end of the third electro-optical modulator (15), and the trigger signal input end of the data acquisition card (23); The output end of the DC power supply (25) is respectively connected to the bias voltage input end of the first electro-optical modulator (3), the bias voltage input end of the second electro-optical modulator (8), and the bias voltage input end of the third electro-optical modulator (15).

2. A distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to claim 1, characterized in that: The narrow linewidth laser (1) is a polarization-maintaining laser with an output power of 40 mW, a wavelength of 1550.14 nm, and a linewidth of 1 kHz.

3. A distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to claim 1, characterized in that: The first optical fiber coupler (2) is a 1×3 polarization-maintaining coupler with a splitting ratio of 33:33:33; the second optical fiber coupler (9) and the third optical fiber coupler (12) are 1×2 polarization-maintaining couplers with a splitting ratio of 50:50; the fourth optical fiber coupler (18) is a 1×2 coupler with a splitting ratio of 50:50; and the fifth optical fiber coupler (20) is a 2×2 coupler with a splitting ratio of 50:

50.

4. A distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to claim 1, characterized in that: The first electro-optical modulator (3) and the third electro-optical modulator (15) are polarization-maintaining modulators with a bandwidth of 10 GHz and an extinction ratio of 30 dB; the second electro-optical modulator (8) is a polarization-maintaining modulator with a bandwidth of 2 GHz and an extinction ratio of 30 dB.

5. The distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to claim 1, characterized in that: The central wavelength of the polarization-maintaining fiber Bragg grating (5) is 1550.08 nm, and the 3dB reflection bandwidth is 0.08 nm.

6. A distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to claim 1, characterized in that: The extinction ratios of the first semiconductor optical amplifier (6) and the second semiconductor optical amplifier (11) are both 45 dB.

7. The distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to claim 1, characterized in that: The 3dB operating bandwidth of the photoelectric balance detector (21) is 2 GHz.

8. The distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to claim 1, characterized in that: The 3dB operating bandwidth of the photodetector (22) is 100MHz.

9. The distributed optical fiber sensing system for simultaneous measurement of temperature, strain and vibration according to claim 1, characterized in that: The data acquisition card (23) has a sampling rate of 5 GS / s and a sampling resolution of 14 bits.

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