Device and method for monitoring flow and leakage in liquid pipeline based on optical fiber sensing

Abstract

The invention belongs to the technical field of distributed optical fiber sensing, and particularly relates to a device and a method for monitoring flow and leakage in a liquid pipeline based on optical fiber sensing. The device comprises a scattering enhancement detection system, a scanning laser, a second optical fiber coupler, an optical fiber circulator, an optical fiber wavelength division multiplexer, an optical fiber grating strain sensor, a fourth photoelectric detector, a data acquisition unit, a data processing unit and a scattering enhancement optical fiber. The second optical fiber coupler, the optical fiber wavelength division multiplexer and the data acquisition unit are all connected with the scattering enhancement detection system; the scanning laser, the second optical fiber coupler and the optical fiber circulator are connected in sequence; and the optical fiber circulator, the optical fiber wavelength division multiplexer, the fourth photoelectric detector, the data acquisition unit and the data processing unit are connected in sequence. According to the device and the method provided by the invention, the pipeline leakage condition can be monitored in real time while the pipeline flow can be accurately measured.

Description

Technical Field

[0001] The present invention belongs to the technical field of distributed optical fiber sensing, and in particular relates to a flow and leakage monitoring device and method in a liquid pipeline based on optical fiber sensing. Background Art

[0002] Fiber-optic distributed acoustic sensor (DAS) has many advantages such as non-intrusiveness, long test distance and immunity to electromagnetic interference. It has been widely used in exploration, security and structural health monitoring in the past decade. Traditional DAS systems use single-mode optical fiber as the sensing unit. Due to problems such as the optical fiber preparation process, the refractive index distribution inside the single-mode optical fiber is uneven, which leads to random interference between scattered signals, resulting in coherent fading. The coherent fading problem will seriously affect the test performance of the DAS system. Specifically, the signal amplitude at the fading point is very low, which makes phase demodulation difficult and the perception signal cannot be effectively extracted. Scattering-enhanced optical fiber can effectively increase the intensity of the reflected signal by periodically writing gratings on the fiber core. The scattering-enhanced DAS system can effectively solve the coherent fading problem and improve the performance of the DAS system.

[0003] In the process of transmitting liquids through pipelines, accurate flow monitoring is crucial, which can not only ensure the safety of transmission, but also improve the transmission efficiency. The leakage problem in pipeline transportation has always been a serious safety issue. The leakage of liquids such as gasoline will cause huge economic losses and energy losses, cause environmental pollution and may also cause casualties. Real-time monitoring of pipelines, timely locating the leakage points and repairing the leakage locations can greatly reduce economic losses and avoid the occurrence of large-scale safety accidents.

[0004] In terms of pipeline flow testing, leakage monitoring and third-party disturbance detection, fiber optic sensing technology is becoming a standard technology and playing an increasingly important role. Chinese patent CN201910195421.7 discloses a system and method for monitoring the flow rate of liquid in a pipeline based on distributed fiber optic temperature sensing technology, which can realize flow rate monitoring of multiple pipelines, but the need to lay heating cables at the same time is more complicated to implement. Chinese patent CN202211247692.0 proposes a leakage monitoring device based on distributed fiber optic strain sensing technology, which uses the principle of expansion of the expansion belt when encountering liquid to monitor full-temperature liquid leakage. Chinese patent CN202122144034.6 proposes a pipeline multi-parameter monitoring system, which uses different types of fiber gratings to monitor the temperature, flow rate and pressure in the pipeline, but it is difficult to monitor leakage events at all locations along the pipeline.

[0005] In addition, DAS technology has been increasingly reported to be used for real-time monitoring of oil and gas pipeline leaks and third-party disturbances due to its significant advantages such as long monitoring distance and high test frequency. Chinese patent CN201910599778.1 proposes a system that uses multiple sensing optical fibers and multiple DAS data processing systems to work together to achieve the measurement of flow velocity, leakage and other parameters. However, the data processing method is complex and requires the laying of multiple sensing optical fibers. Too many split paths will also affect the monitoring distance.

[0006] Based on current technical means, there is a lack of a liquid pipeline flow and leakage simultaneous monitoring device and method with a simple structure and data processing method and long-distance monitoring capability. Summary of the invention

[0007] In view of the above technical problems, the present invention provides a flow and leakage monitoring device and method in a liquid pipeline based on optical fiber sensing, which can accurately measure the pipeline flow and perform real-time monitoring of pipeline leakage.

[0008] The present invention is achieved through the following technical solutions: A flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing, the device comprising: a scattering enhancement detection system, a scanning laser, a second optical fiber coupler, an optical fiber circulator, an optical fiber wavelength division multiplexer, an optical fiber Bragg grating strain sensor, a fourth photoelectric detector, a data acquisition unit, a data processing unit and a scattering enhancement optical fiber; The second optical fiber coupler, the optical fiber wavelength division multiplexer and the data acquisition unit are all connected to the scattering enhancement detection system; the scattering enhancement detection system is used to detect and demodulate the vibration signal; The scanning laser, the second fiber coupler, and the fiber circulator are connected in sequence; the scattering enhancement fiber and the fiber grating strain sensor are arranged in a liquid pipeline to be detected; The optical fiber circulator, the optical fiber wavelength division multiplexer, the fourth photoelectric detector, the data acquisition unit and the data processing unit are connected in sequence.

[0009] Further, the scanning laser is connected to an input end of the second fiber coupler; the other input end of the second fiber coupler is connected to the scattering enhancement detection system; and the output end of the second fiber coupler is connected to the first port of the fiber circulator; The third port of the fiber circulator is connected to the fiber wavelength division multiplexer, and the output port corresponding to the scattering enhancement band of the fiber wavelength division multiplexer is connected to the scattering enhancement detection system; and the output end of the fiber wavelength division multiplexer corresponding to the band of the fiber grating strain sensor is connected to the fourth photodetector; the output end of the fourth photodetector is connected to the channel of the data acquisition unit; the analog output interface of the data acquisition unit is connected to the scattering enhancement detection system; and the data output interface of the data acquisition unit is connected to the data processing unit.

[0010] Furthermore, the second port of the fiber circulator is connected to the scattering-enhanced optical fiber, and the scattering-enhanced optical fiber is connected to the fiber Bragg grating strain sensor; or, the second port of the fiber circulator is connected to the fiber Bragg grating strain sensor, and the fiber Bragg grating strain sensor is connected to the scattering-enhanced optical fiber.

[0011] Further, the scattering enhancement detection system is a 3x3 coupler-based scattering enhancement system; The 3x3 coupler-based scattering enhancement system includes a narrow linewidth laser, a first fiber coupler, an acousto-optic modulator driver, an acousto-optic modulator, a fiber amplifier, a fiber bandpass filter, a three-by-three fiber coupler, a first photodetector, a second photodetector, a third photodetector, and a polarization controller; The output end of the narrow linewidth laser is connected to the input end of the fiber coupler, one output end of the fiber coupler is connected to the acousto-optic modulator, and the other output end of the fiber coupler is connected to the input end of the polarization controller; The output end of the polarization controller is connected to an input port of the three-by-three fiber coupler; the output port corresponding to the scattering enhancement band of the fiber wavelength division multiplexer is connected to another input port of the three-by-three fiber coupler; the scanning laser band output port of the fiber wavelength division multiplexer is connected to the fourth photodetector; The output end of the acousto-optic modulator is connected to the input end of the optical fiber amplifier, the output end of the optical fiber amplifier is connected to the input end of the optical fiber bandpass filter, and the output end of the optical fiber bandpass filter is connected to an input end of the second optical fiber coupler; The three output ports of the three-by-three optical fiber coupler are respectively connected to the first photodetector, the second photodetector and the third photodetector; the three outputs of the first photodetector, the second photodetector and the third photodetector are respectively connected to the three inputs of the data acquisition unit; The analog output end of the data acquisition unit is connected to the input end driven by the acousto-optic modulator; and the output end driven by the acousto-optic modulator is connected to the acousto-optic modulator.

[0012] Further, the scattering enhancement detection system is a heterodyne scattering enhancement detection system; the heterodyne scattering enhancement detection system comprises a narrow linewidth laser, a first fiber coupler, an acousto-optic modulator driver, an acousto-optic modulator, an electro-optic modulator, a fiber amplifier, a fiber bandpass filter, a polarization controller, a third fiber coupler, and a first photodetector; The output end of the narrow linewidth laser is connected to an input port of the first optical fiber coupler; the two output ends of the first optical fiber coupler are connected to the acousto-optic modulator and the polarization controller respectively; The output end of the acousto-optic modulator is connected to the input end of the electro-optic modulator; the electro-optic modulator is used to shift the frequency of the optical signal; the electro-optic modulator, the erbium-doped fiber amplifier, and the fiber bandpass filter are connected in sequence; the fiber bandpass filter is connected to an input end of the second fiber coupler; The output end of the polarization controller is connected to an input end of the third fiber coupler, and the other input end of the third fiber coupler is connected to an output port corresponding to the scattering enhancement band of the fiber wavelength division multiplexer; the output end of the third fiber coupler is connected to the first photodetector, and the output end of the first photodetector is connected to the data acquisition unit; the analog output end of the data acquisition unit is connected to the acousto-optic modulator driver to provide a modulation signal, and the acousto-optic modulator driver is connected to the acousto-optic modulator.

[0013] Furthermore, the narrow linewidth laser has an operating band of 1550 nm and is used to output optical signals with different pulse widths.

[0014] Furthermore, the working band of the scanning laser is 1310nm, which is used to perform wavelength scanning within the range of plus or minus 20nm; the optical fiber wavelength division multiplexer is used to distinguish between the 1550nm optical band and the 1310nm optical band.

[0015] A method for monitoring flow and leakage in a liquid pipeline based on optical fiber sensing, the method comprising: Step 1: Turn on the scanning laser to measure the wavelength of light returned by the fiber Bragg grating strain sensor when there is no liquid flowing in the pipeline and at different liquid flow rates, thereby obtaining the strain change and establishing a relationship curve between strain and flow rate; Step 2: Turn on the narrow linewidth laser to enable the scattering enhanced detection system to work, record the demodulated phase data along the pipeline under no leakage and different leakage conditions of the liquid pipeline, and establish a data set; use the data set to train the convolutional neural network to obtain the turbulence feature convolution kernel; Step 3: The system is officially working. The data acquisition unit performs phase demodulation based on a three-by-three fiber coupler on the data collected based on the 3x3 coupler scattering enhancement system to obtain demodulated phase data; or the data acquisition unit performs phase demodulation based on a heterodyne form on the data collected from the heterodyne scattering enhancement detection system to obtain demodulated phase data; The data of the fiber Bragg grating strain sensor is filtered and denoised before being sent to the data processing unit. Using the strain and flow velocity relationship curve obtained in step one and step two and the turbulence characteristic convolution kernel, the data processing unit performs convolution neural network operations on the demodulated phase data to identify turbulence caused by leakage, converts the strain data into flow velocity to obtain the flow velocity result, and finally displays the result.

[0016] In the present invention, a weak reflection Bragg fiber grating is etched in the middle of the scattering enhanced optical fiber, and the central wavelength of the weak reflection Bragg fiber grating is consistent with the wavelength of a narrow linewidth laser in a scattering enhanced detection system, so that the light emitted by the narrow linewidth laser can be effectively reflected, and a strain-sensitive fiber grating is connected to the front end or the rear end of the scattering enhanced optical fiber; the central wavelength of the strain-sensitive fiber grating is consistent with the scanning central wavelength of the scanning laser, so that the strain change on the fiber grating can be normally demodulated, and the strain fiber grating is reflective and needs to be packaged, which is used to enhance robustness while isolating temperature influence.

[0017] Beneficial technical effects of the present invention: In the method provided by the present invention, leakage and flow rate monitoring are respectively in the 1550nm band and the 1310nm band, so they can be monitored simultaneously without interfering with each other, and have the advantages of long monitoring distance, simple structure and data processing method.

[0018] The device and method for monitoring flow and leakage in a liquid pipeline based on scattering-enhanced distributed optical fiber acoustic sensing (DAS) technology provided by the present invention have a simple structure and data processing method, and have long-distance monitoring capabilities. They can accurately measure pipeline flow and perform real-time monitoring of pipeline leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a system diagram for implementing flow and leakage monitoring in a pipeline based on a 3x3 coupler scattering enhancement system in Example 1 of the present invention; Figure 2 A diagram of a pipeline flow and leakage monitoring implementation system based on a heterodyne demodulation scattering enhancement system in Example 2 of the present invention; The figures are marked as follows: 1. narrow linewidth laser; 2. first fiber coupler; 2'. second fiber coupler; 3. acousto-optic modulator driver; 4. acousto-optic modulator; 5. fiber amplifier; 6. fiber bandpass filter; 7. scanning laser; 8. electro-optic modulator; 9. fiber circulator; 10. fiber wavelength division multiplexer; 11. three-by-three fiber coupler; 12. first photodetector; 12'. second photodetector; 12''. third photodetector; 12'''. fourth photodetector; 13. data acquisition unit; 14. polarization controller; 15. fiber grating strain sensor; 16. data processing unit; 17. scattering enhanced fiber. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0021] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.

[0022] Embodiment 1: A flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing, see the attached Figure 1 The device comprises: a scattering enhancement detection system, a scanning laser 7, a second fiber coupler 2', a fiber circulator 9, a fiber wavelength division multiplexer 10, a fiber grating strain sensor 15, a fourth photodetector 12''', a data acquisition unit 13, a data processing unit 16 and a scattering enhancement fiber 17; The second optical fiber coupler 2', the optical fiber wavelength division multiplexer 10 and the data acquisition unit 13 are all connected to the scattering enhancement detection system; the scattering enhancement detection system uses optical principles to detect and demodulate vibration signals with high sensitivity; The scanning laser 7, the second fiber coupler 2', and the fiber circulator 9 are connected in sequence; the scattering enhancement fiber 17 and the fiber grating strain sensor 15 are arranged in the liquid pipeline to be detected; The optical fiber circulator 9, the optical fiber wavelength division multiplexer 10, the fourth photodetector 12''', the data acquisition unit 13 and the data processing unit 16 are connected in sequence.

[0023] In this embodiment, the scanning laser 7 is connected to one input end of the second fiber coupler 2'; the other input end of the second fiber coupler 2' is connected to the scattering enhancement detection system; therefore, the output end of the second fiber coupler 2' is connected to the first port of the fiber circulator 9; The third port of the optical fiber circulator 9 is connected to the optical fiber wavelength division multiplexer 10, and the output port corresponding to the scattering enhancement band of the optical fiber wavelength division multiplexer 10 is connected to the scattering enhancement detection system; and the output end of the optical fiber wavelength division multiplexer 10 corresponding to the band of the optical fiber grating strain sensor 15 is connected to the fourth photodetector 12'''; the output end of the fourth photodetector 12''' is connected to the channel of the data acquisition unit 13; the analog output interface of the data acquisition unit 13 is connected to the scattering enhancement detection system; the data output interface of the data acquisition unit 13 is connected to the data processing unit 16.

[0024] In this embodiment, the second port of the fiber circulator 9 is connected to the scattering enhanced optical fiber 17, and the scattering enhanced optical fiber 17 is connected to the fiber Bragg grating strain sensor 15; or, the second port of the fiber circulator 9 is connected to the fiber Bragg grating strain sensor 15, and the fiber Bragg grating strain sensor 15 is connected to the scattering enhanced optical fiber 17.

[0025] In this embodiment, the scattering enhancement detection system is a 3x3 coupler-based scattering enhancement system 101; The 3x3 coupler-based scattering enhancement system 101 includes a narrow linewidth laser 1, a first fiber coupler 2, an acousto-optic modulator driver 3, an acousto-optic modulator 4, a fiber amplifier 5, a fiber bandpass filter 6, a three-by-three fiber coupler 11, a first photodetector 12, a second photodetector 12', a third photodetector 12'', and a polarization controller 14; The output end of the narrow linewidth laser 1 is connected to the input end of the fiber coupler 2, one output end of the fiber coupler 2 is connected to the acousto-optic modulator 4, and the other output end of the fiber coupler 2 is connected to the input end of the polarization controller 14; The output end of the polarization controller 14 is connected to an input port of the three-by-three fiber coupler 11; the output port corresponding to the scattering enhancement band of the fiber wavelength division multiplexer 10 is connected to another input port of the three-by-three fiber coupler 11; the scanning laser band output port of the fiber wavelength division multiplexer 10 is connected to the fourth photodetector 12'''; The output end of the acousto-optic modulator 4 is connected to the input end of the optical fiber amplifier 5, the output end of the optical fiber amplifier 5 is connected to the input end of the optical fiber bandpass filter 6, and the output end of the optical fiber bandpass filter 6 is connected to an input end of the second optical fiber coupler 2'; The three output ports of the three-by-three fiber coupler 11 are respectively connected to the first photodetector 12, the second photodetector 12' and the third photodetector 12'; the three outputs of the first photodetector 12, the second photodetector 12' and the third photodetector 12' are respectively connected to the three inputs of the data acquisition unit 13; The analog output end of the data acquisition unit 13 is connected to the input end of the AOM driver 3 ; and the output end of the AOM driver 3 is connected to the AOM 4 .

[0026] In this embodiment, the narrow linewidth laser 1 has an operating wavelength of 1550 nm and is used to output optical signals with different pulse widths.

[0027] In this embodiment, the working wavelength band of the scanning laser 7 is 1310 nm, which is used to perform wavelength scanning within the range of plus or minus 20 nm; the optical fiber wavelength division multiplexer 10 can at least distinguish between the 1550 nm optical band and the 1310 nm optical band.

[0028] In this embodiment, in the device, the scanning laser 7, the second fiber coupler 2', the fiber circulator 9, the scattering enhanced fiber 17 and the fiber Bragg grating strain sensor 15 are connected in sequence; or The scanning laser 7, the second fiber coupler 2', the fiber circulator 9, the fiber grating strain sensor 15 and the scattering enhancement fiber 17 are connected in sequence.

[0029] Embodiment 2: A flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing. This embodiment is basically the same as Embodiment 1, except that the difference lies in the scattering enhancement detection system. Figure 2 In this embodiment, the scattering enhancement detection system is a heterodyne scattering enhancement detection system 201; the heterodyne scattering enhancement detection system 201 includes a narrow linewidth laser 1, a first fiber coupler 2, an acousto-optic modulator driver 3, an acousto-optic modulator 4, an electro-optic modulator 8, a fiber amplifier 5, a fiber bandpass filter 6, a polarization controller 14, a third fiber coupler 2'', and a first photodetector 12; The output end of the narrow linewidth laser 1 is connected to an input port of the first fiber coupler 2; the two output ends of the first fiber coupler 2 are connected to the acousto-optic modulator 4 and the polarization controller 14 respectively; The output end of the acousto-optic modulator 4 is connected to the input end of the electro-optic modulator 8; the electro-optic modulator 8 is used to shift the frequency of the optical signal; the electro-optic modulator 8, the erbium-doped fiber amplifier 5, and the fiber bandpass filter 6 are connected in sequence; the fiber bandpass filter 6 is connected to an input end of the second fiber coupler 2'; The output end of the polarization controller 14 is connected to an input end of the third fiber coupler 2'', and the other input end of the third fiber coupler 2'' is connected to the output port corresponding to the scattering enhancement band of the fiber wavelength division multiplexer 10; the output end of the third fiber coupler 2'' is connected to the first photodetector 12, and the output end of the first photodetector 12 is connected to the data acquisition unit 13; the analog output end of the data acquisition unit 13 is connected to the acousto-optic modulator driver 3 to provide a modulation signal, and the acousto-optic modulator driver 3 is connected to the acousto-optic modulator 4.

[0030] Embodiment 3: A method for monitoring flow and leakage in a liquid pipeline based on optical fiber sensing, using the device described in Embodiment 1 or Embodiment 2, the method comprising: Step 1: Turn on the scanning laser to measure the wavelength of light returned by the fiber Bragg grating strain sensor when there is no liquid flowing in the pipeline and at different liquid flow rates, thereby obtaining the strain change and establishing a relationship curve between strain and flow rate; Step 2: Turn on the narrow linewidth laser to enable the scattering enhanced detection system to work, record the demodulated phase data along the pipeline under no leakage and different leakage conditions of the liquid pipeline, and establish a data set; the turbulence caused by the leakage is reflected in the demodulated phase data, and the convolutional neural network is trained using the data set to obtain a turbulence characteristic convolution kernel; Among them, the convolutional neural network is trained using the data set to obtain a turbulence characteristic convolution kernel, and the conventional technology of using convolutional neural networks in the prior art for optical fiber data processing can be used (such as the method for obtaining a convolution kernel based on a neural network disclosed in patent CN202111521196.5).

[0031] Step 3: The system is officially working. The data acquisition unit performs phase demodulation based on a three-by-three fiber coupler on the data collected based on the 3x3 coupler scattering enhancement system to obtain demodulated phase data; or the data acquisition unit performs phase demodulation based on a heterodyne form on the data collected from the heterodyne scattering enhancement detection system to obtain demodulated phase data; The data of the fiber Bragg grating strain sensor is filtered and denoised before being sent to the data processing unit. Using the strain and flow velocity relationship curve obtained in step one and step two and the turbulence characteristic convolution kernel, the data processing unit performs convolution neural network operations on the demodulated phase data to identify turbulence caused by leakage, converts the strain data into flow velocity to obtain the flow velocity result, and finally displays the result.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing, characterized in that: The device comprises: a scattering enhancement detection system, a scanning laser, a second optical fiber coupler, an optical fiber circulator, an optical fiber wavelength division multiplexer, an optical fiber grating strain sensor, a fourth photoelectric detector, a data acquisition unit, a data processing unit and a scattering enhancement optical fiber; The second optical fiber coupler, the optical fiber wavelength division multiplexer and the data acquisition unit are all connected to the scattering enhancement detection system; the scattering enhancement detection system is used to detect and demodulate the vibration signal; The scanning laser, the second fiber coupler, and the fiber circulator are connected in sequence; the scattering enhancement fiber and the fiber grating strain sensor are arranged in a liquid pipeline to be detected; The optical fiber circulator, the optical fiber wavelength division multiplexer, the fourth photoelectric detector, the data acquisition unit and the data processing unit are connected in sequence.

2. According to claim 1, a flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing is characterized in that: The scanning laser is connected to an input end of a second optical fiber coupler; the other input end of the second optical fiber coupler is connected to the scattering enhancement detection system; the output end of the second optical fiber coupler is connected to the first port of the optical fiber circulator; The third port of the fiber circulator is connected to the fiber wavelength division multiplexer, and the output port corresponding to the scattering enhancement band of the fiber wavelength division multiplexer is connected to the scattering enhancement detection system; and the output end of the fiber wavelength division multiplexer corresponding to the band of the fiber grating strain sensor is connected to the fourth photodetector; the output end of the fourth photodetector is connected to the channel of the data acquisition unit; the analog output interface of the data acquisition unit is connected to the scattering enhancement detection system; and the data output interface of the data acquisition unit is connected to the data processing unit.

3. According to claim 1, a flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing is characterized in that: The second port of the fiber optic circulator is connected to the scattering-enhanced optical fiber, and the scattering-enhanced optical fiber is connected to the fiber grating strain sensor; or the second port of the fiber optic circulator is connected to the fiber grating strain sensor, and the fiber grating strain sensor is connected to the scattering-enhanced optical fiber.

4. According to claim 1, a flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing is characterized in that: The scattering enhancement detection system is a 3x3 coupler-based scattering enhancement system; The 3x3 coupler-based scattering enhancement system includes a narrow linewidth laser, a first fiber coupler, an acousto-optic modulator driver, an acousto-optic modulator, a fiber amplifier, a fiber bandpass filter, a three-by-three fiber coupler, a first photodetector, a second photodetector, a third photodetector, and a polarization controller; The output end of the narrow linewidth laser is connected to the input end of the fiber coupler, one output end of the fiber coupler is connected to the acousto-optic modulator, and the other output end of the fiber coupler is connected to the input end of the polarization controller; The output end of the polarization controller is connected to an input port of the three-by-three fiber coupler; the output port corresponding to the scattering enhancement band of the fiber wavelength division multiplexer is connected to another input port of the three-by-three fiber coupler; the scanning laser band output port of the fiber wavelength division multiplexer is connected to the fourth photodetector; The output end of the acousto-optic modulator is connected to the input end of the optical fiber amplifier, the output end of the optical fiber amplifier is connected to the input end of the optical fiber bandpass filter, and the output end of the optical fiber bandpass filter is connected to an input end of the second optical fiber coupler; The three output ports of the three-by-three optical fiber coupler are respectively connected to the first photodetector, the second photodetector and the third photodetector; the three outputs of the first photodetector, the second photodetector and the third photodetector are respectively connected to the three inputs of the data acquisition unit; The analog output end of the data acquisition unit is connected to the input end driven by the acousto-optic modulator; and the output end driven by the acousto-optic modulator is connected to the acousto-optic modulator.

5. According to claim 1, a flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing is characterized in that: The scattering enhancement detection system is a heterodyne scattering enhancement detection system; the heterodyne scattering enhancement detection system comprises a narrow line width laser, a first fiber coupler, an acousto-optic modulator driver, an acousto-optic modulator, an electro-optic modulator, a fiber amplifier, a fiber bandpass filter, a polarization controller, a third fiber coupler, and a first photodetector; The output end of the narrow linewidth laser is connected to an input port of the first optical fiber coupler; the two output ends of the first optical fiber coupler are connected to the acousto-optic modulator and the polarization controller respectively; The output end of the acousto-optic modulator is connected to the input end of the electro-optic modulator; The electro-optic modulator is used to shift the frequency of the optical signal; The electro-optic modulator, the erbium-doped fiber amplifier, and the fiber bandpass filter are connected in sequence; the fiber bandpass filter is connected to an input end of the second fiber coupler; The output end of the polarization controller is connected to an input end of the third fiber coupler, and the other input end of the third fiber coupler is connected to an output port corresponding to the scattering enhancement band of the fiber wavelength division multiplexer; the output end of the third fiber coupler is connected to the first photodetector, and the output end of the first photodetector is connected to the data acquisition unit; the analog output end of the data acquisition unit is connected to the acousto-optic modulator driver to provide a modulation signal, and the acousto-optic modulator driver is connected to the acousto-optic modulator.

6. A flow and leakage monitoring device in a liquid pipeline based on optical fiber sensing according to claim 4 or 5, characterized in that: The narrow linewidth laser has an operating wavelength of 1550 nm and is used to output optical signals with different pulse widths.

7. The device for monitoring flow and leakage in a liquid pipeline based on optical fiber sensing according to claim 1, characterized in that: The working wavelength band of the scanning laser is 1310nm, and is used for wavelength scanning within the range of plus or minus 20nm; the optical fiber wavelength division multiplexer is used for distinguishing the 1550nm optical wavelength band from the 1310nm optical wavelength band.

8. A method for monitoring flow and leakage in a liquid pipeline based on optical fiber sensing, characterized in that: The method comprises: Step 1: Turn on the scanning laser to measure the wavelength of light returned by the fiber Bragg grating strain sensor when there is no liquid flowing in the pipeline and at different liquid flow rates, thereby obtaining the strain change and establishing a relationship curve between strain and flow rate; Step 2: Turn on the narrow linewidth laser to enable the scattering enhanced detection system to work, record the demodulated phase data along the pipeline under no leakage and different leakage conditions of the liquid pipeline, and establish a data set; use the data set to train the convolutional neural network to obtain the turbulence feature convolution kernel; Step 3: The system is officially working. The data acquisition unit performs phase demodulation based on a three-by-three fiber coupler on the data collected based on the 3x3 coupler scattering enhancement system to obtain demodulated phase data; or the data acquisition unit performs phase demodulation based on a heterodyne form on the data collected from the heterodyne scattering enhancement detection system to obtain demodulated phase data; The data of the fiber Bragg grating strain sensor is filtered and denoised before being sent to the data processing unit. Using the strain and flow velocity relationship curve obtained in step one and step two and the turbulence characteristic convolution kernel, the data processing unit performs convolution neural network operations on the demodulated phase data to identify turbulence caused by leakage, converts the strain data into flow velocity to obtain the flow velocity result, and finally displays the result.

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