WO2022068881A1

WO2022068881A1 - Vibration detecting system

Info

Publication number: WO2022068881A1
Application number: PCT/CN2021/121737
Authority: WO
Inventors: 任广
Original assignee: 中兴通讯股份有限公司
Priority date: 2020-09-29
Filing date: 2021-09-29
Publication date: 2022-04-07
Also published as: CN114323241A

Abstract

A vibration detecting system, comprising: lasers (101, 201, 301, 401), acousto-optic modulators (102, 202, 302, 402), two-way communication units (103, 203, 303, 403, 501), sensing optical fibers (104, 204, 304, 404, 503), narrowband filters (105, 205, 305, 405), conversion units (106, 206, 306, 406) having a photoelectric conversion function, and signal processing units (107, 207, 307, 407). An output end of each of the lasers (101, 201, 301, 401) is connected to an input end of each of the acousto-optic modulators (102, 202, 302, 402); an output end of each of the acousto-optic modulators (102, 202, 302, 402) is connected to a first end of each of the two-way communication units (103, 203, 303, 403, 501); a second end of each of the two-way communication units (103, 203, 303, 403, 501) is connected to the sensing optical fibers (104, 204, 304, 404, 503); a third end of each of the two-way communication units (103, 203, 303, 403, 501) is connected to an input end of each of the narrowband filters (105, 205, 305, 405); an output end of each of the narrowband filters (105, 205, 305, 405) is connected to an input end of each of the conversion units (106, 206, 306, 406); an output end of each of the conversion units (106, 206, 306, 406) is connected to the signal processing units (107, 207, 307, 407). The system uses the narrowband filters (105, 205, 305, 405) to filter out noise in backscatter signals, thereby avoiding new noise caused by using an optical fiber amplifier, improving the signal-to-noise ratio of the backscatter signals, and improving the detection precision of the system.

Description

A vibration detection system

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on the Chinese patent application with the application number "202011055431.X" and the application date is September 29, 2020, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is incorporated herein by reference. into this application.

technical field

The embodiments of the present application relate to the technical field of optical fiber sensing, and in particular, to a vibration detection system.

Background technique

At present, the use of optical fibers to sense changes in physical quantities has become a mainstream technology today. For example, the changes in light energy generated by the influence of external vibrations when light propagates in optical fibers are used to monitor vibration events; this technology is used in buildings, oil pipelines, etc. Intrusion detection and other aspects have a relatively wide range of applications. In the phase sensitive optical time domain reflectometer (Φ-OTDR) system, the signal-to-noise ratio of the backscattered signal is low. Therefore, in order to enlarge the backscattered signal and improve the signal-to-noise ratio, a fiber amplifier is usually added before the conversion unit. to amplify the backscattered signal.

However, the fiber amplifier will also amplify the noise in the backscattered signal, and the fiber amplifier itself is an active device, which will generate new noise during operation, so that the signal-to-noise ratio of the backscattered signal has not been improved; , due to the strong optical power of the amplified backscattered signal, after the amplified backscattered signal enters the fiber, it is easy to cause nonlinear effects, that is, when the optical power reaches a certain intensity, other invalid signals will be excited. , will also reduce the signal-to-noise ratio of the backscattered signal, thereby reducing the detection accuracy of the entire Φ-OTDR system.

SUMMARY OF THE INVENTION

The embodiment of the present application provides a vibration detection system, including: a laser, an acousto-optic modulator, a two-way communication unit, a sensing fiber, a narrowband filter, a conversion unit with photoelectric conversion function, and a signal processing unit; the output of the laser The end is connected to the input end of the acousto-optic modulator, the output end of the acousto-optic modulator is connected to the first end of the two-way communication unit, and the second end of the two-way communication unit is connected to the sensing fiber; the The third end of the bidirectional communication unit is connected to the input end of the narrowband filter, the output end of the narrowband filter is connected to the input end of the conversion unit, and the output end of the conversion unit is connected to the signal processing unit; the The transmission direction of the signal in the two-way communication unit is: from the first end of the two-way communication unit to the second end of the two-way communication unit, and from the second end of the two-way communication unit to the third end.

Description of drawings

One or more embodiments are exemplified by the pictures in the corresponding drawings, and these exemplifications do not constitute limitations of the embodiments, and elements with the same reference numerals in the drawings are denoted as similar elements, Unless otherwise stated, the figures in the accompanying drawings do not constitute a scale limitation.

1 is a schematic diagram of a circuit structure of a vibration detection system according to a first embodiment of the present application;

2 is a schematic diagram of a circuit structure of a bidirectional communication unit according to the first embodiment of the present application;

3 is a schematic diagram of a circuit structure of a vibration detection system according to a second embodiment of the present application;

4 is a schematic diagram of a circuit structure of a vibration detection system according to a third embodiment of the present application;

5 is a schematic diagram of a circuit structure of a second optical fiber splitting unit according to a third embodiment of the present application;

6 is a schematic diagram of a circuit structure of a vibration detection system according to a fourth embodiment of the present application;

7 is a schematic diagram of a circuit structure of a third optical fiber branching unit according to a fourth embodiment of the present application;

8 is a schematic diagram of a partial circuit structure of a vibration detection system according to a fifth embodiment of the present application;

9 is a schematic circuit structure diagram of a schematic circuit structure diagram of a Raman combiner and a Raman amplifier of two adjacent branches of a vibration detection system according to a fifth embodiment of the present application.

Detailed ways

The main purpose of the embodiments of the present application is to propose a vibration detection system, which improves the signal-to-noise ratio of the backscattered signal, thereby improving the detection accuracy of the entire system.

In the vibration detection system proposed in this application, when the sensing fiber is subjected to external vibration, the intensity of the light transmitted in the sensing fiber will change, which will cause changes in the backscattered signal. The second end is transmitted to the third end of the two-way communication unit. Therefore, the backscattered signal output by the third end of the two-way communication unit will also be transformed, so that the vibration detection system can detect the external vibration by detecting the backscattered signal. In this application, a narrow-band filter is connected to the third end of the two-way communication unit, and the narrow-band filter is used to replace the fiber amplifier in the related art, thereby filtering out the noise in the backscattered signal and avoiding the problem caused by the fiber amplifier. The new noise problem improves the signal-to-noise ratio of the backscattered signal, thereby improving the detection accuracy of the entire system.

In order to make the objectives, technical solutions and advantages of the embodiments of the present application more clear, each embodiment of the present application will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that, in each embodiment of the present application, many technical details are provided for the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can be realized. The following divisions of the various embodiments are for the convenience of description, and should not constitute any limitation on the specific implementation of the present application, and the various embodiments may be combined with each other and referred to each other on the premise of not contradicting each other.

The first embodiment of the present application relates to a vibration detection system. The schematic diagram of the circuit structure of the vibration detection system in this embodiment is shown in FIG. 1 , including: a laser 101 , an acousto-optic modulator 102 , a two-way communication unit 103 , a sensor Optical fiber 104 , narrowband filter 105 , conversion unit 106 with photoelectric conversion function, signal processing unit 107 .

Specifically, the output end of the laser 101 is connected to the input end of the acousto-optic modulator 102, the output end of the acousto-optic modulator 102 is connected to the first end a of the bidirectional communication unit 103, and the second end b of the bidirectional communication unit 103 is connected to the sensor Optical fiber 104; the third end c of the bidirectional communication unit 103 is connected to the input end of the narrowband filter 105, the output end of the narrowband filter 105 is connected to the input end of the conversion unit 106, and the output end of the conversion unit 106 is connected to the signal processing unit 107; bidirectional communication The transmission direction of the signal in the unit 103 is: from the first end of the bidirectional communication unit 103 to the second end of the bidirectional communication unit 103 , and from the second end of the bidirectional communication unit 103 to the third end of the bidirectional communication unit 103 .

Specifically, the laser 101 of the vibration detection system of this embodiment is a device that generates an optical signal. After the laser 101 generates an optical signal, the optical signal is transmitted to the acousto-optic modulator 102 through the output end of the laser 101, and the acousto-optic modulator 102 The optical signal is modulated, for example, the phase of the optical signal can be modulated by the acousto-optic modulator 102; after that, the modulated optical signal enters the two-way communication unit 103 and is transmitted to the sensing fiber 104. This process is the light generated by the laser 101. The transmission path of the signal, and the transmission direction of the backscattered signal is opposite to the transmission direction of the optical signal; therefore, the present application adds a two-way communication unit 103 between the sensing fiber 104 and the acousto-optic modulator 102, and according to the two-way communication The functional characteristics of the unit 103, the backscattered signal is transmitted from the second end b of the bidirectional communication unit 103 to the third end c of the bidirectional communication unit 103, so that the backscattered signal can be transmitted through the third end c of the bidirectional communication unit 103 To the narrowband filter 105, the narrowband filter 105 can filter out the noise of other wavelengths and improve the signal-to-noise ratio of the backscattered signal; finally, the backscattered signal is transmitted to the conversion unit 106, and the conversion unit 106 converts the backscattered signal The optical signal is converted into an electrical signal and then input to the signal processing unit 107 for the signal processing unit 107 to analyze and process the electrical signal, thereby obtaining the external vibration condition.

It should be noted that the backscattered signal is generated according to the optical signal generated by the laser 101 during the transmission process, and is opposite to the transmission path of the optical signal; when the sensing fiber 104 is subjected to external vibration, the inside of the sensing fiber 104 The intensity and phase of the transmitted light will change, and at the same time, the backscattered signal will also change. Therefore, the backscattered signal output by the third end c of the two-way communication unit 103 will also change, so that the vibration detection system can The situation of external vibration is detected by detecting the backscattered signal; therefore, in this embodiment, the narrowband filter 105 is connected to the third end c of the two-way communication unit 103, and the narrowband filter 105 is used to replace the commonly used fiber amplifier, thereby filtering out The noise in the backscattered signal avoids the problem of new noise caused by the fiber amplifier, improves the signal-to-noise ratio of the backscattered signal, and thus improves the detection accuracy of the entire system.

In one example, the two-way communication unit 103 is an optical circulator. According to the characteristics of the optical circulator, the optical signal generated by the laser 101 is transmitted from the first end of the bidirectional communication unit 103 to the second end of the bidirectional communication unit 103, and the backscattered signal is transmitted from the second end of the bidirectional communication unit 103 to the bidirectional communication unit 103. The third end of the communication unit 103 .

In an example, as shown in FIG. 2 , the two-way communication unit 103 includes a seventh optical fiber splitter 1031 and a one-way isolator 1032; the seventh optical fiber splitter 1031 includes three ports, a first end h, a second end i , the third end j, wherein the first end h and the second end i are located on one side of the seventh optical fiber splitter 1031 (the left side in FIG. 2 ), and the third end j is located on the side of the seventh optical fiber splitter 1031 On the other side (the right side in Figure 2), according to the characteristics of the optical fiber splitter, the signal in this embodiment can be transmitted from the first end h, the second end i to the third end j, or from the third end. The terminal j is respectively transmitted to the first terminal h and the second terminal i. Specifically, the first end of the one-way isolator 1032 serves as the first end a of the two-way communication unit 103, and the second end of the one-way isolator 1032 is connected to the first end h of the seventh fiber splitter 1031; the seventh fiber The second end i of the splitter 1031 is used as the third end c of the bidirectional communication unit 103, the third end j of the seventh fiber optic splitter 1031 is used as the second end b of the bidirectional communication unit 103; the unidirectional isolator 1032 is used for The signal blocking the first end h of the seventh fiber splitter 1031 is transmitted to the acousto-optic modulator 102 . In this embodiment, the seventh optical fiber splitter 1031 and the one-way isolator 1032 are arranged together, thereby realizing the functions of the two-way communication unit 103 .

Specifically, the first end of the one-way isolator 1032 is connected to the second end of the acousto-optic modulator 102 as the first end a of the two-way communication unit 103, and the second end of the one-way isolator 1032 is connected to the seventh optical fiber splitter The first end h of 1031, the unidirectional isolator 1032 has the function of unidirectional isolation, and can block the signal of the first end h of the seventh fiber splitter 1031 from being transmitted to the acousto-optic modulator 102, that is, blocking the signal from the unidirectional The second end of the isolator 1032 is transmitted to the first end of the one-way isolator 1032; that is, when the optical signal generated by the laser 101 reaches the first end of the one-way isolator 1032, it can pass through the The first end is transmitted to the second end of the one-way isolator 1032, so that the optical signal generated by the laser 101 is transmitted to the seventh fiber splitter 1031, which can realize the forward transmission of the optical signal, but cannot realize the reverse transmission of the signal . The backscattered signal in this embodiment is transmitted from the third end j of the seventh optical fiber splitter 1031 to the first end h of the seventh optical fiber splitter 1031 and the second end of the seventh optical fiber splitter 1031 respectively i, and the first end h of the seventh optical fiber splitter 1031 is connected with a one-way isolator 1032, which can block the signal of the first end h of the seventh optical fiber splitter 1031 from being transmitted to the acousto-optic modulation the device 102 so that the backscattered signal is only transmitted from the second end b of the two-way communication unit 103 to the third end c of the two-way communication unit 103 .

In one example, the vibration detection system further includes: a fiber amplifier; the output end of the laser 101 is connected to the input end of the acousto-optic modulator 102 through the fiber amplifier. Specifically, the fiber amplifier is arranged between the laser 101 and the acousto-optic modulator 102. In this embodiment, by setting the fiber amplifier to amplify the signal output by the laser 101, the detection distance can be improved; After the amplifier, the problems of unevenness of the optical pulse and slow rise of the rising edge when the optical signal is amplified by the optical fiber amplifier can be eliminated. In practical applications, the fiber amplifier is specifically an erbium-doped fiber amplifier.

It should be noted that the acousto-optic modulator 102 is further connected with a driver, and the driver is used to drive the acousto-optic modulator 102 to modulate the optical signal generated by the laser 101 .

In an example, the signal processing unit 107 includes an analog-to-digital converter and a data processing module; the output end of the conversion unit 106 is connected to the input end of the analog-to-digital converter, and the output end of the analog-to-digital converter is connected to the data processing module. Specifically, the input to the signal processing unit 107 is an electrical signal. By setting an analog-to-digital converter, the electrical signal is converted into a digital signal for analysis and processing by the data processing module, thereby analyzing and obtaining the external vibration.

A second embodiment of the present application relates to a vibration detection system. The second embodiment is substantially the same as the first embodiment, and the main difference is that: in the second embodiment of the present application, the conversion unit also has a coherent demodulation function; the vibration detection system further includes a first optical fiber branching unit. It should be noted that the relevant technical details of the above-mentioned first embodiment are still valid in this embodiment, and are not repeated here in order to avoid repetition.

A schematic diagram of the circuit structure of a vibration detection system involved in the second embodiment of the present application is shown in FIG. 3, including: a laser 201, an acousto-optic modulator 202, a two-way communication unit 203, a sensing fiber 204, a narrowband filter 205, The conversion unit 206 , the signal processing unit 207 , and the first fiber splitting unit 208 .

Specifically, the output end of the laser 201 is connected to the input end of the acousto-optic modulator 202 through the first output end e of the first optical fiber branching unit 208 , and the output end of the acousto-optic modulator 202 is connected to the first end of the two-way communication unit 203 The second end of the bidirectional communication unit 203 is connected to the sensing fiber 204; the third end of the bidirectional communication unit 203 is connected to the input end of the narrowband filter 205, and the output end of the narrowband filter 205 is connected to the input end of the conversion unit 206, and the conversion unit The output end of 206 is connected to the signal processing unit 207 ; the output end of the laser 201 is also connected to the input end of the conversion unit 206 through the second output end f of the first fiber splitting unit 208 .

Specifically, the first fiber splitting unit 208 includes an input end d and two output ends (ie, the first output end e and the second output end f); the output end of the laser 201 is connected to the first fiber splitting unit 208 The input end d, the first output end e of the first fiber splitting unit 208 is connected to the input end of the acousto-optic modulator 202 ; the second output end f of the first fiber splitting unit 208 is connected to the input end of the conversion unit 206 . In one example, the first fiber splitting unit 208 is a fiber splitter.

In practical applications, the optical signal generated by the laser 201 will be decomposed by the first optical fiber splitting unit 208 according to a preset ratio, so as to be decomposed into two branches, wherein the preset ratio is set according to actual requirements, This embodiment does not make a specific limitation. For example, one percent of the optical signal is transmitted to the conversion unit 206 through the second output end f of the first optical fiber splitting unit 208 , and ninety-nine percent of the optical signal is transmitted through the second output end f of the first optical fiber splitting unit 208 An output end e and the acousto-optic modulator 202 are transmitted to the bidirectional communication unit 203, and the above-mentioned backscattered signal is generated based on the 99% optical signal during its transmission process, and the backscattered signal is generated from The second end b of the bidirectional communication unit 103 is transmitted to the third end c of the bidirectional communication unit 103, and is transmitted to the conversion unit 206 through the narrowband filter 205 at the third end c of the bidirectional communication unit 103; After one-half of the optical signal and the backscattered signal, the two signals are coherently demodulated to obtain an optical signal after the two signals are mixed. After that, the conversion unit 206 converts the mixed optical signal into an electrical signal. signal for the signal processing unit 207 to analyze and process the electrical signal.

In this embodiment, by adding the function of coherent demodulation in the conversion unit 206, part of the optical signal in the optical signal generated by the laser 201 is coherently demodulated together with the backscattered signal, thereby improving the signal-to-noise ratio of the backscattered signal, Improve the accuracy of vibration detection by the system.

It should be noted that the conversion unit 206 with the photoelectric conversion function and the coherent demodulation function can be integrated into one device, or can be two independent devices, for example, can be divided into two independent devices, the coherent receiver and the photoelectric converter. device.

In one example, the arrangement paths of every two sensing fibers 204 are the same. By setting the arrangement paths of the two sensing fibers 204 to be the same, the two sensing fibers 204 can serve as backups for each other. When one of the sensing fibers 204 fails, the other sensing fiber 204 can also detect normally. Improve the anti-fault ability of the system.

In one example, multiple sensing fibers 204 are placed in different directions. For example, when there are two sensing fibers 204, the directions of the two sensing fibers 204 can be set in a "cross" arrangement, so as to expand the detection range of the system as much as possible. This embodiment further expands the detection range of the system by setting the sensing fibers 204 with different directions.

It should be noted that, in practical applications, every two optical fibers can be set as a group, that is, the arrangement paths of the two sensing fibers 204 in the group are the same. While further expanding the detection range of the system, the system can also have better anti-fault capability.

A third embodiment of the present application relates to a vibration detection system. The third embodiment is substantially the same as the first embodiment, and the main difference is that: in the third embodiment of the present application, the vibration detection system further includes: a second optical fiber branching unit. It should be noted that the relevant technical details of the above-mentioned first embodiment are still valid in this embodiment, and are not repeated here in order to avoid repetition.

A schematic diagram of the circuit structure of a vibration detection system involved in the third embodiment of the present application is shown in FIG. 4, including: a laser 301, an acousto-optic modulator 302, a two-way communication unit 303, a sensing fiber 304, a narrowband filter 305, The conversion unit 306 , the signal processing unit 307 , and the second fiber splitting unit 309 . It should be noted that only four output ends of the second optical fiber splitting unit 309 are shown in FIG. 3 . However, in actual situations, the number of output ends of the second optical fiber splitting unit 309 may be greater than four or less than four. each, which is not specifically limited in this embodiment.

Specifically, the output end of the laser 301 is connected to the input end of the acousto-optic modulator 302, and the output end of the acousto-optic modulator 302 is connected to the input end of the second optical fiber branching unit 309, and the second optical fiber branching unit 309 includes N outputs end, the number of the bidirectional communication unit 303, the sensing fiber 304, the narrowband filter 305, and the conversion unit 306 are all N; N is a natural number greater than or equal to 2; The first ends of the two-way communication units 303 are connected in a one-to-one correspondence, the second ends of the N two-way communication units 303 are connected with the N sensing fibers 304 in a one-to-one correspondence; the third ends of the N two-way communication units 303 are connected with the N narrowband filters The input terminals of the N narrowband filters 305 are connected to the input terminals of the N conversion units 306 in one-to-one correspondence; the output terminals of the N conversion units 306 are connected to the signal processing unit 307 .

In practical applications, the number of signal processing units 307 may be one or more. When the number of output ends of the second fiber splitting unit 309 is large, the number of signal processing units 307 may be appropriately increased. Therefore, the signal processing unit 307 The number of can be set according to actual needs, which is not specifically limited in this embodiment.

Specifically, the second optical fiber branching unit 309 has one input end and N output ends, and the output ends of each second optical fiber branching unit 309 are sequentially connected to a bidirectional communication unit 303, a narrowband filter 305, a converter unit 306, and after that, the outputs of the N conversion units 306 are commonly connected to the same information processing unit.

In this embodiment, by arranging the second optical fiber splitting unit 309 with N output ends, the vibration system can detect the vibration at any fiber detection position, thereby expanding the detection range of the entire system.

In an example, as shown in FIG. 5 , it is a schematic diagram of the circuit structure of the second optical fiber splitting unit 309 . The second optical fiber splitting unit includes a first optical fiber splitter 3091 , a second optical fiber splitter 3092 , and a third optical fiber splitter3093;

The input end of the first optical fiber splitter 3091 is used as the input end of the second optical fiber splitting unit 309, the first output end of the first optical fiber splitter 3091 is connected to the input end of the second optical fiber splitter 3092, and the first optical fiber splitter The second output end of the optical fiber splitter 3091 is connected to the input end of the third optical fiber splitter 3093; The second output ends serve as the four output ends of the second fiber splitting unit 309 .

A fourth embodiment of the present application relates to a vibration detection system. The fourth embodiment is roughly the same as the third embodiment, and the main difference is that: in the fourth embodiment of the present application, the conversion unit also has a coherent demodulation function; the vibration detection system further includes: a first optical fiber branching unit, a Three fiber splitting units. It should be noted that, the relevant technical details of the above-mentioned third embodiment are still valid in this embodiment, and are not repeated here in order to avoid repetition.

A schematic diagram of the circuit structure of a vibration detection system involved in the fourth embodiment of the present application is shown in FIG. 6, including: a laser 401, an acousto-optic modulator 402, a two-way communication unit 403, a sensing fiber 404, a narrowband filter 405, The conversion unit 406 , the signal processing unit 407 , the first optical fiber branching unit 408 , the second optical fiber branching unit 409 , and the third optical fiber branching unit 410 . It should be noted that only the four output ends of the second optical fiber splitting unit 409 and the third optical fiber splitting unit 410 are shown in FIG. The number of the output ends of the circuit unit 410 may be more than four or less than four, which is not specifically limited in this embodiment.

Specifically, the output end of the laser 401 is connected to the input end of the acousto-optic modulator 402 through the first output end of the first optical fiber branching unit 408 , and the output end of the acousto-optic modulator 402 is connected to the output end of the second optical fiber branching unit 409 . The input end, the second fiber splitting unit 409 includes N output ends, the number of the bidirectional communication unit 403, the sensing fiber 404, the narrowband filter 405, and the conversion unit 406 are all N; N is a natural number greater than or equal to 2; The N output ends of the two-fiber splitting unit 409 are connected to the first ends of the N bidirectional communication units 403 in a one-to-one correspondence, and the second ends of the N two-way communication units 403 are connected to the N sensing fibers 404 in a one-to-one correspondence; N The third ends of the two-way communication units 403 are connected to the input ends of the N narrowband filters 405 in one-to-one correspondence, and the output ends of the N narrowband filters 405 are connected to the input ends of the N conversion units 406 in one-to-one correspondence; The output terminals of the conversion unit 406 are commonly connected to a signal processing unit 407 .

The output end of the laser 401 is also connected to the input end of the third optical fiber branching unit 410 through the second output end of the first optical fiber branching unit 408, and the third optical fiber branching unit 410 includes N output ends; The N output terminals of the unit 410 are connected to the input terminals of the N conversion units 406 in a one-to-one correspondence.

In this embodiment, since the conversion unit 406 has the function of coherent demodulation, and the second fiber splitting unit 409 with N output ends and the third fiber splitting unit 410 with N output ends are provided, the backscattered signal is improved in While increasing the signal-to-noise ratio, the detection range of the entire system is expanded.

In one example, as shown in FIG. 7 , it is a schematic diagram of the circuit structure of the third optical fiber splitting unit 410 . The third optical fiber splitting unit 410 includes a fourth optical fiber splitter 4101 , a fifth optical fiber splitter 4102 , a sixth optical fiber splitter Optical fiber splitter 4103; the input end of the fourth optical fiber splitter 4101 is used as the input end of the third optical fiber splitting unit 410, and the first output end of the fourth optical fiber splitter 4101 is connected to the input end of the fifth optical fiber splitter 4102 , the second output end of the fourth fiber optic splitter 4101 is connected to the input end of the sixth fiber optic splitter 4103; the first output end and the second output end of the fifth fiber optic splitter 4102 are connected to the sixth fiber optic splitter 4103 The first output end and the second output end of , are used as the four output ends of the third fiber splitting unit 410 .

A fifth embodiment of the present application relates to a vibration detection system. The fifth embodiment adds a Raman amplifier and a Raman multiplexer on the basis of the above-mentioned first to fourth embodiments.

A schematic diagram of a partial circuit structure of a vibration detection system involved in the fifth embodiment of the present application is shown in FIG. It should be noted that the structure in FIG. 8 can be applied to any one of the first to fourth embodiments above. Therefore, the relevant technical details of the first to fourth embodiments above are still valid in this embodiment, and are To avoid repetition, no further description will be given here.

Specifically, whether there is only one bidirectional communication unit 501 or N bidirectional communication units 501 in the system, the second end of one bidirectional communication unit 501 is connected to a sensing fiber 503 through a Raman multiplexer 502, a Raman A Raman amplifier 504 is also connected to the combiner 502 .

Specifically, when the bidirectional communication unit 501 is provided with a second optical fiber branching unit (not marked in the figure), and the second optical fiber branching unit includes N output terminals, each output terminal is respectively connected to the bidirectional communication unit in turn. 501 , a Raman combiner 502 , and a sensing fiber 503 . In an example, each Raman combiner 502 can be connected to a Raman amplifier 504 respectively, so that the backscattered signal of each branch can be amplified, and the detection distance of each branch in the system can be improved; In an example, the Raman combiners 502 of every two adjacent branches may be connected to a Raman amplifier 504 in common, as shown in FIG. 9 , the Raman combiners 502 and the Raman amplifiers of the two adjacent branches are A schematic diagram of the circuit structure of 504, the output end of the Raman amplifier 504 is connected to the input end of an optical fiber splitter 505, the first output end of the optical fiber splitter 505 is connected to the Raman combiner 502 in one of the branches, and the optical fiber splitter The second output end of the splitter is connected to the Raman combiner 502 in the other branch; thus, the number of Raman amplifiers 504 is saved, and the cost is saved.

In this embodiment, the optical signal transmitted in the circuit is amplified by the Raman amplifier 504 and the Raman combiner 502, thereby amplifying the backscattered signal and improving the detection distance of the system.

Those of ordinary skill in the art can understand that the above-mentioned embodiments are specific embodiments for realizing the present application, and in practical applications, various changes in form and details can be made without departing from the spirit and the spirit of the present application. scope.

Claims

A vibration detection system, comprising: a laser, an acousto-optic modulator, a two-way communication unit, a sensing fiber, a narrow-band filter, a conversion unit with photoelectric conversion function, and a signal processing unit;

The output end of the laser is connected to the input end of the acousto-optic modulator, the output end of the acousto-optic modulator is connected to the first end of the two-way communication unit, and the second end of the two-way communication unit is connected to the transmission unit. sensor fiber;

The third end of the two-way communication unit is connected to the input end of the narrowband filter, the output end of the narrowband filter is connected to the input end of the conversion unit, and the output end of the conversion unit is connected to the signal processing unit;

The transmission direction of the signal in the two-way communication unit is: from the first end of the two-way communication unit to the second end of the two-way communication unit, and from the second end of the two-way communication unit to the two-way communication unit the third end of the unit.
The vibration detection system according to claim 1, wherein the conversion unit further has a coherent demodulation function; the vibration detection system further comprises a first optical fiber branching unit;

The output end of the laser is connected to the input end of the acousto-optic modulator through the first output end of the first optical fiber branching unit;

The output end of the laser is also connected to the input end of the conversion unit through the second output end of the first optical fiber branching unit.
The vibration detection system according to claim 1, wherein the vibration detection system further comprises: a second optical fiber branching unit;

The output end of the acousto-optic modulator is connected to the input end of the second optical fiber branching unit, the second optical fiber branching unit includes N output ends, the two-way communication unit, the sensing fiber, the The number of the narrowband filter and the conversion unit is N; N is a natural number greater than or equal to 2;

The N output ends of the second optical fiber branching unit are connected to the first ends of the N bidirectional communication units in a one-to-one correspondence, and the second ends of the N bidirectional communication units are connected to the N sensing fibers. A corresponding connection;

The third terminals of the N bidirectional communication units are connected to the input terminals of the N narrowband filters in a one-to-one correspondence, and the output terminals of the N narrowband filters are connected to the input terminals of the N conversion units one by one. corresponding connection;

The output terminals of the N conversion units are connected to the signal processing unit.
The vibration detection system according to claim 3, wherein the conversion unit further has a coherent demodulation function;

The vibration detection system further includes: a first optical fiber branching unit, a third optical fiber branching unit;

The output end of the laser is connected to the input end of the acousto-optic modulator through the first output end of the first optical fiber branching unit;

The output end of the laser is also connected to the input end of the third optical fiber branching unit through the second output end of the first optical fiber branching unit, and the third optical fiber branching unit includes N output ends; The N output ends of the optical fiber branching unit are connected to the N input ends of the conversion units in a one-to-one correspondence.
The vibration detection system according to claim 4, wherein the second optical fiber splitting unit comprises a first optical fiber splitter, a second optical fiber splitter, and a third optical fiber splitter;

The input end of the first optical fiber splitter is used as the input end of the second optical fiber splitting unit, and the first output end of the first optical fiber splitter is connected to the input end of the second optical fiber splitter, so The second output end of the first fiber optic splitter is connected to the input end of the third fiber optic splitter; the first output end and the second output end of the second fiber optic splitter are connected to the third fiber optic splitter. The first output end and the second output end of the splitter are used as the four output ends of the second optical fiber splitting unit;

The third optical fiber splitting unit includes a fourth optical fiber splitter, a fifth optical fiber splitter, and a sixth optical fiber splitter;

The input end of the fourth optical fiber splitter is used as the input end of the third optical fiber splitting unit, and the first output end of the fourth optical fiber splitter is connected to the input end of the fifth optical fiber splitter, so the The second output end of the fourth optical fiber splitter is connected to the input end of the sixth optical fiber splitter; the first output end and the second output end of the fifth optical fiber splitter are connected to the sixth optical fiber splitter. The first output end and the second output end of the splitter are used as the four output ends of the third optical fiber splitting unit.
The vibration detection system according to any one of claims 1 to 5, wherein the vibration detection system further comprises: a Raman amplifier and a Raman combiner;

A second end of one of the two-way communication units is connected with one of the sensing fibers through the Raman combiner;

One of the Raman combiners is also connected with one of the Raman amplifiers.
The vibration detection system according to any one of claims 1 to 6, wherein the vibration detection system further comprises: an optical fiber amplifier;

The output end of the laser is connected to the input end of the acousto-optic modulator through the fiber amplifier.
The vibration detection system of any one of claims 1 to 7, wherein the two-way communication unit is an optical circulator.
The vibration detection system according to any one of claims 1 to 7, wherein the two-way communication unit comprises a seventh optical fiber splitter, a one-way isolator;

The first end of the one-way isolator serves as the first end of the two-way communication unit, and the second end of the one-way isolator is connected to the first end of the seventh optical fiber splitter;

The second end of the seventh optical fiber splitter serves as the third end of the two-way communication unit, and the third end of the seventh optical fiber splitter serves as the second end of the two-way communication unit;

The one-way isolator is used for blocking the signal of the first end of the seventh fiber splitter from being transmitted to the acousto-optic modulator.
The vibration detection system according to any one of claims 3 to 5, wherein the arrangement paths of every two sensing fibers are the same.
The vibration detection system of any one of claims 3 to 5, wherein a plurality of the sensing fibers are placed in different directions.
The vibration detection system according to any one of claims 1 to 11, wherein the signal processing unit comprises: an analog-to-digital converter, a data processing module;

The output end of the conversion unit is connected to the input end of the analog-to-digital converter, and the output end of the analog-to-digital converter is connected to the data processing module.