Fiber optic accelerometer and pipeline leakage sensing system

Abstract

The present invention relates to a fiber optic accelerometer and a pipeline leakage sensing system. The fiber optic accelerometer comprises a sensing optical fiber, a first mass block, a metal diaphragm, a second mass block, and an integrated housing; a tapered structure is made on the sensing optical fiber, and the end of the sensing optical fiber is plated with a high-reflection film; the central part of the metal diaphragm is tightly clamped by the first mass block and the second mass block; the edge of the metal diaphragm is fixed together by the lower shell and the upper shell of the integrated housing. The pipeline leakage sensing system comprises a detection light source, a fiber optic accelerometer, a multiplexing device, a photodetector, and a signal acquisition and processing unit. By using a phase generation carrier unit to generate a carrier signal, combined with signal demodulation and processing, the system can accurately capture the weak vibration signal caused by pipeline leakage, and determine the leakage position through a cross-correlation operation algorithm, thereby improving the accuracy and reliability of pipeline leakage monitoring. In addition, the present invention has low cost, simple installation and maintenance, and good economy and scalability.

Description

Technical Field

[0001] The present invention relates to the field of sensing technology, and in particular to a fiber optic accelerometer, a method for manufacturing the fiber optic accelerometer, a pipeline leakage sensing system and a pipeline leakage monitoring method. Background Art

[0002] As a sensor that can accurately measure the acceleration change of an object, the accelerometer plays an irreplaceable role in many fields, and its technological development has also received widespread attention. In the field of traditional accelerometers, there are mainly piezoelectric, piezoresistive, capacitive and MEMS types, each of which is used in different application scenarios with its unique working principle and performance characteristics.

[0003] In the process of rapid development of modern industry and technology, pipeline transportation, as a key mode of transportation, is widely used in the transportation of various important materials such as oil, natural gas, tap water, etc. Its safe and stable operation is of vital importance to economic development and social stability.

[0004] However, with the increasing requirements for safety and monitoring accuracy in the pipeline transportation industry, traditional accelerometers have gradually exposed some limitations in pipeline leakage monitoring applications, and it is difficult to meet the complex and changeable actual working conditions. The use of optical fiber as a sensitive element has shown many potential advantages. It has ultra-high sensitivity and can keenly perceive extremely small acceleration changes, which is extremely critical for capturing the weak vibration signals generated in the early stage of pipeline leakage; at the same time, it has extremely strong anti-electromagnetic interference capabilities. Even in the presence of a complex electromagnetic environment around the pipeline, it can work stably and reliably to ensure the accuracy of the measurement data and effectively avoid the impact of electromagnetic interference on the monitoring results; in addition, its excellent high temperature and corrosion resistance enables it to adapt to the harsh working environment of the pipeline, whether it is a high-temperature and high-pressure oil and gas pipeline, or a chemical pipeline with corrosive media, it can maintain a good performance state, providing a strong guarantee for long-term and stable pipeline monitoring, and has unique application value and development potential in the field of pipeline leakage monitoring.

[0005] Although fiber optic accelerometers have many advantages in theory, there are still prominent technical bottlenecks when they are actually used in pipeline leakage monitoring, which seriously restricts their effective application and popularization in this field.

[0006] On the one hand, the existing fiber optic accelerometers have obvious defects in structural design, resulting in their sensitivity and resolution unable to meet the needs of high-precision monitoring. One type of fiber optic accelerometer uses fiber Bragg grating as the sensing fiber. Although this design structure is simple, due to the use of the pasting process, the fiber Bragg grating is prone to chirp faults, resulting in decreased sensitivity. The chirp fault distorts the reflected waveform of the fiber Bragg grating, reduces the accelerometer's ability to respond to acceleration changes, and cannot achieve high sensitivity and high resolution detection requirements. Especially in pipeline leakage monitoring, the weak vibration signal generated at the initial stage of the leakage point requires the sensor to have extremely high sensitivity to capture it in time. However, the defects of this structural design make it impossible for the existing accelerometer to accurately detect these tiny changes, and it is easy to miss the best time for emergency repairs. Another type of fiber optic accelerometer uses a structure in which the sensing fiber is wound around a mass block. Although this design can improve sensitivity, its manufacturing process is relatively complex and is prone to large mechanical errors, resulting in poor consistency. Due to the process non-uniformity and errors that may occur during the winding process, the coupling effect between the sensing fiber and the mass block is unstable, which in turn affects the accuracy and long-term stability of the accelerometer. These design defects make the existing fiber optic accelerometers perform unsatisfactorily in high-sensitivity, high-resolution applications, especially in the field of micro-leakage monitoring.

[0007] On the other hand, the corresponding sensor signal demodulation system also has many problems, and a demodulation solution with low cost, large dynamic range and fast response has not yet been developed. Most of the current demodulation methods are based on the bevel filtering method, which relies on a stable working zero point, and the dynamic range of the demodulation system is relatively limited. During the operation of the pipeline, if there are strong vibrations caused by large-scale mechanical construction, instantaneous large acceleration changes caused by pressure fluctuations, or when a serious leakage accident occurs in the pipeline, the existing demodulation system is often unable to accurately capture and process these drastically changing acceleration signals. This may cause the monitoring data to be lost or distorted, resulting in the inability to provide an accurate basis for the assessment and positioning of pipeline leaks. Summary of the invention

[0008] In view of the existing technical problems, the purpose of the present invention is to provide a fiber optic accelerometer and a pipeline leakage sensing system. Through the optimization design of the structure, the sensitivity performance of the sensor is fundamentally improved, so that it can achieve high-sensitivity and high-resolution detection to meet the needs of precision measurement. At the same time, a hardware demodulation system based on phase-generated carrier is provided, which will have the characteristics of low cost, large dynamic range and fast demodulation, thereby effectively solving the two key problems currently faced by fiber optic accelerometers.

[0009] A fiber optic accelerometer comprises a sensing fiber, a first mass block, a metal diaphragm, a second mass block and an integrated housing; a tapered structure is formed on the sensing fiber, and a high-reflection film is plated on the end of the sensing fiber; the integrated housing consists of an upper housing and a lower housing; through holes are respectively formed in the upper housing, the first mass block, the second mass block and the metal diaphragm of the integrated housing for the sensing fiber to pass through in sequence; the central part of the metal diaphragm is tightly clamped by the first mass block and the second mass block; the edge part of the metal diaphragm is fixed together by the lower housing and the upper housing of the integrated housing, thereby encapsulating a spring oscillator structure formed by the sensing fiber, the first mass block, the metal diaphragm and the second mass block.

[0010] The metal diaphragm is made of beryllium copper material.

[0011] The sensing optical fiber is prepared with a tapered structure by chemical corrosion or hot-melt tapering; the central part of the metal diaphragm is tightly clamped by the first mass block and the second mass block by magnetic attraction or gluing; the first mass block, the metal diaphragm and the second mass block are formed with a through hole in the middle by mechanical or laser drilling technology; the end of the sensing optical fiber is plated with metal or multi-layer medium by magnetron sputtering to form a high-reflective film for enhancing the reflected signal; the upper shell and the lower shell of the integrated shell are fixed by a first screw and a second screw.

[0012] A pipeline leakage sensing system comprises a detection light source, an optical isolator, a first optical fiber coupler, a first circulator, a second circulator, a first polarization controller, a second polarization controller, a phase generation carrier unit, a second optical fiber coupler, a third optical fiber coupler, a first photodetector, a fourth optical fiber coupler, a second photodetector, a signal acquisition processing unit, a first multiplexing device, a second multiplexing device, a first optical fiber accelerometer, and a second optical fiber accelerometer; the first optical fiber accelerometer and the second optical fiber accelerometer adopt the optical fiber accelerometer;

[0013] The detection light source is a narrow line width laser or a tunable laser; the light emitted by the detection light source is divided into three after passing through the optical isolator and the first optical fiber coupler, forming a first detection light, a second detection light and a third detection light;

[0014] The first detection light is transmitted to the first light outlet of the first circulator, the second light outlet of the first circulator is connected to the first multiplexing device, the first multiplexing device is connected to one or more fiber accelerometers, the return light passes through the third light outlet of the first circulator and then enters the third fiber coupler via the first polarization controller, is received by the first photodetector, and then passes through the signal acquisition and processing unit;

[0015] The second detection light is transmitted to the second light outlet of the second circulator, the second light outlet of the second circulator is connected to the second multiplexing device, the second multiplexing device is connected to one or more fiber accelerometers, the return light passes through the third light outlet of the second circulator and then enters the fourth fiber coupler via the second polarization controller, is received by the second photodetector, and then passes through the signal acquisition processing unit;

[0016] The third detection light passes through the phase generation carrier unit and is split into two through the second fiber coupler. One path passes through the third fiber coupler and the signal beam of the fiber optic accelerometer connected to the first multiplexing device, is received by the first photodetector, and then passes through the signal acquisition and processing unit; the other path passes through the fourth fiber coupler and the signal beam of the fiber optic accelerometer connected to the second multiplexing device, is received by the second photodetector, and then passes through the signal acquisition and processing unit.

[0017] When the first multiplexing device and the second multiplexing device are time division multiplexing devices, they are the first optical switch and the second optical switch; or when the first multiplexing device and the second multiplexing device are wavelength division multiplexing devices, they are the first wavelength division multiplexer and the second wavelength division multiplexer; the phase generation carrier unit is used to generate a carrier signal;

[0018] The first photodetector and the second photodetector are used to convert received optical signals into electrical signals; and the signal acquisition and processing unit is used to demodulate the electrical signals output by the first photodetector and the second photodetector.

[0019] The phase generation carrier unit comprises piezoelectric ceramics, single-mode optical fiber and a signal generator; the single-mode optical fiber is tightly wound around the piezoelectric ceramics, and the signal generator is used to apply an excitation signal to the piezoelectric ceramics.

[0020] The signal acquisition and processing unit comprises an acquisition card and a host computer processing program; the acquisition card has two data transmission channels for respectively receiving electrical signals from the first photodetector and the second photodetector.

[0021] The host computer processing program demodulates the signal received by the acquisition card based on the algorithm of phase-generated carrier demodulation technology; the algorithm based on phase-generated carrier demodulation technology includes signal DC removal processing, signal mixing, low-pass filtering, signal difference, signal differentiation, signal integration, and high-pass filtering.

[0022] The installation positions of the multiple fiber optic accelerometers connected to the first multiplexing device and the second multiplexing device on the pipeline follow specific layout rules, which are determined based on the length, direction, branching conditions and historical leakage data of the pipeline to ensure that the most representative and sensitive vibration signals can be obtained, thereby improving the accuracy and reliability of leakage monitoring. The method for determining the installation position also takes into account the distribution of vibration sources in the surrounding environment. By analyzing the environmental vibration spectrum, the fiber optic accelerometer is installed at a location with less vibration interference.

[0023] A pipeline leakage monitoring method based on cross-correlation operation adopts the pipeline leakage sensing system, comprising the following steps: using a pair of optical fiber accelerometers, the optical fiber accelerometer connected to the first multiplexing device and the optical fiber accelerometer connected to the second multiplexing device to detect the pipeline and obtain corresponding vibration signals; performing cross-correlation operation on the signals detected by the pair of optical fiber accelerometers after demodulation by the signal acquisition and processing unit; observing the peak deviation of the cross-correlation optical signal, and determining the peak position by an accurate peak detection algorithm, wherein the peak detection algorithm can accurately identify the main peak and the secondary peak of the cross-correlation optical signal in the presence of noise and signal fluctuation, and record the position information, and calculate the time delay of the two signals according to the change of the peak position, so as to calculate the specific position of the pipeline leakage.

[0024] Compared with the existing technology, the optical fiber accelerometer, pipeline leakage sensing system and pipeline leakage monitoring method provided by the examples of the present invention have the following beneficial effects:

[0025] First, in terms of sensor structure design, the innovative use of a spring oscillator structure that combines sensing optical fiber, mass block and metal diaphragm significantly improves the sensitivity of the sensor. Through precise optimization of parameters such as the size and material of the mass block and metal diaphragm, the sensor can more sensitively capture tiny acceleration changes, which is of key significance for the detection of weak vibration signals generated in the early stages of pipeline leakage, greatly improving the early warning capability of leakage monitoring, and effectively solving the problem of insufficient sensitivity of traditional fiber optic accelerometers, so that it can show excellent performance in precision application scenarios such as microgravity measurement, mechanical detection at the biological cell level, and high-precision inertial navigation systems, expanding the application range of fiber optic accelerometers.

[0026] Secondly, from the manufacturing method point of view, the fiber optic accelerometer manufacturing process provided by the present invention has good operability and repeatability. By clarifying the processing requirements and assembly steps of each component, it is possible to stably produce fiber optic accelerometer products with consistent and reliable performance, promoting the widespread application of fiber optic accelerometers in more fields.

[0027] Thirdly, the hardware demodulation system based on phase-generated carrier brings many advantages to the whole solution. On the one hand, it has a large dynamic range of demodulation capabilities, which can cope with weak leakage signals during pipeline operation and strong vibration signals caused by various complex working conditions (such as large-scale mechanical construction, pressure changes, etc.), ensuring that vibration characteristic information can be accurately extracted under different degrees of pipeline vibration, providing solid data support for accurate assessment and positioning of pipeline leakage, and overcoming the defects of limited dynamic range of traditional demodulation methods. On the other hand, the demodulation system realizes fast demodulation, meeting the strict requirements of pipeline transportation systems for real-time monitoring. When a pipeline leakage accident occurs, the measurement data can be quickly demodulated and analyzed, and accurate information can be provided for rapid emergency disposal of the pipeline in a timely manner, avoiding information lag caused by slow demodulation speed, and effectively reducing the losses and risks that may be caused by leakage accidents.

[0028] In addition, in the overall design of the pipeline leakage sensing system, the collaborative work between the various components optimizes the signal transmission, acquisition and processing process. The reasonable configuration of components such as the detection light source, fiber coupler, circulator, polarization controller and photodetector ensures the efficient transmission and accurate acquisition of optical signals, reduces signal loss and interference, and further improves the detection accuracy and reliability of the system. At the same time, the design of the signal acquisition and processing unit adopts a suitable acquisition card and a host computer processing program based on phase generation carrier demodulation technology. Through the comprehensive application of multiple signal processing algorithms, it can effectively remove noise and extract useful signals, enhance the system's ability to process complex signals, and make the entire pipeline leakage sensing system more stable, accurate and efficient in practical applications.

[0029] Finally, the pipeline leakage monitoring method based on cross-correlation operation proposed in the present invention can accurately calculate the time delay of two signals through accurate peak detection algorithm and cross-correlation operation, thereby realizing accurate positioning of pipeline leakage position. This method not only improves the accuracy of leakage positioning, but also has stronger noise resistance and adaptability compared with traditional monitoring methods. It can accurately identify leakage in complex pipeline operation environments, provide strong technical support for pipeline maintenance and repair, and effectively guarantee the safety and stability of pipeline transportation. It has significant economic and social benefits, and is expected to be widely promoted and applied in the pipeline transportation industry, leading the new development of pipeline leakage monitoring technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic structural diagram of a fiber optic accelerometer according to an embodiment of the present invention.

[0031] FIG. 2 is a schematic diagram of the structure of a sensing optical fiber in a fiber optic accelerometer according to an embodiment of the present invention.

[0032] FIG3 is a flow chart of a method for manufacturing a fiber optic accelerometer according to an embodiment of the present invention.

[0033] FIG. 4 is a diagram of a pipeline leakage sensing system based on a time division multiplexing device according to an embodiment of the present invention.

[0034] FIG. 5 is a diagram of a pipeline leakage sensing system based on a wavelength division multiplexing device according to an embodiment of the present invention.

[0035] FIG. 6 is a schematic diagram of a pipeline leakage monitoring method according to an embodiment of the present invention.

[0036] In the figure: sensing optical fiber 11, high reflection film 12, tapered structure 13, first mass block 14, metal diaphragm 15, second mass block 16, first screw 17, second screw 18, integrated housing 19, narrow linewidth laser 31, optical isolator 32, first fiber coupler 33, first circulator 34, second circulator 35, first polarization controller 36, second polarization controller 37, phase generation carrier unit 38, second fiber coupler 39, third fiber coupler 310, first photodetector 311, fourth fiber coupler 312, second photodetector 313, signal acquisition processing unit 314, first optical switch 315, second optical switch 316, first fiber accelerometer 317, second fiber accelerometer 318, pipeline body 319, marked leakage point 320, tunable laser 41, first wavelength division multiplexer 42, second wavelength division multiplexer 43, first optical signal 51, second optical signal 52. DETAILED DESCRIPTION

[0037] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In this specification, the size ratios in the drawings do not represent the actual size ratios, but are only used to reflect the relative position relationship and connection relationship between the components. Components with the same name or the same number represent similar or identical structures and are only for illustrative purposes.

[0039] It should be noted that when an element is referred to as being “connected” to another element or an element is referred to as being “connected to” another element, it may be directly connected to the other element or there may be an intervening element.

[0040] The terms "first", "second", etc. in the specification and claims of the embodiments of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0042] As shown in FIG1 , a fiber optic accelerometer includes a sensing fiber 11, a first mass block 14, a metal diaphragm 15, a second mass block 16, and an integrated housing 19; a tapered structure 13 is made on the sensing fiber, and a high-reflection film 12 is plated on the end of the sensing fiber; the integrated housing 19 consists of an upper housing and a lower housing; through holes are respectively made in the upper housing, the first mass block 14, the second mass block 16, and the metal diaphragm 15 of the integrated housing 19 for the sensing fiber 11 to pass through in sequence; the center portion of the metal diaphragm 15 is tightly clamped by the first mass block 14 and the second mass block 16; the edge portion of the metal diaphragm 15 is fixed together by the lower housing and the upper housing of the integrated housing 19, thereby encapsulating the spring oscillator structure composed of the sensing fiber 11, the first mass block 14, the metal diaphragm 15, and the second mass block 16.

[0043] As shown in FIGS. 1 and 2 , the end face of the sensing optical fiber is coated with a high-reflection film 12. This design significantly improves the reflectivity of light, thereby effectively increasing the power of the returned optical signal, laying a solid foundation for enhancing the detection sensitivity and optimizing the performance of the entire accelerometer. Figure 2 As shown, the sensing optical fiber 11 is made of a single-mode optical fiber with stable performance as the basic material, and is manufactured by chemical etching or hot-melt taper to meet the requirements. It has a taper structure 13 in the middle and a high-reflection film 12 on the end face. The core of a single-mode optical fiber is relatively thin, and only one mode of light propagation is allowed. It has the characteristics of low dispersion and low loss, and can achieve long-distance, high-speed data transmission.

[0044] This sensing fiber has unique advantages and principles in fiber optic sensing. The tapered structure of the fiber makes it highly sensitive to small changes in the surrounding environment. The sensitivity enhancement principle is based on: ,

[0045] in Fis the force, A is the cross-sectional area, E is the Young's modulus, and ϵ is the strain of the optical fiber. According to the formula, the smaller the cross-sectional area, the greater the stress, and the greater the strain of the optical fiber. In the process of optical fiber sensing, when external physical quantities such as stress, temperature, magnetic field or chemical composition change, the optical properties of the optical fiber will change accordingly. For example, its refractive index will fluctuate with changes in the external environment. This is because the surface of the optical fiber interacts more significantly with external substances, and external factors can more easily affect the propagation path and speed of light in the optical fiber, resulting in changes in the refractive index. This change in refractive index will further cause changes in the propagation characteristics of light, such as light intensity, phase, polarization state, etc. By accurately detecting the changes in these optical signals, high-sensitivity and high-precision detection of various physical quantities and chemical components can be achieved, which provides a solid foundation for the application of optical fiber sensing technology in many fields, enabling optical fiber-based sensors to capture subtle signal changes in complex and changing environments, and thus provide reliable data support for various monitoring and control systems.

[0046] The metal diaphragm 15 is made of beryllium copper.

[0047] As shown in FIG1 , the metal diaphragm 15 can be tightly clamped by the first mass block 14 and the second mass block 16 by magnetic attraction or gluing, and the metal diaphragm 15 is tightly clamped by the upper shell and the lower shell of the integrated housing 19. This ingenious connection method not only ensures the stability of the structure, but also provides a reliable basis for subsequent vibration conduction. The first mass block 14, the metal diaphragm 15 and the second mass block 16 can form a through hole in the middle by mechanical or laser drilling technology. The spring oscillator structure composed of the sensing optical fiber 11, the mass block and the metal diaphragm 15 is the core of the entire fiber optic accelerometer. When any form of disturbance occurs in the external environment, the acceleration generated by the disturbance will act on the fiber optic accelerometer, causing the spring oscillator structure to produce a corresponding vibration response. During this vibration process, due to the inertial effect of the mass block and the elastic deformation of the spring oscillator structure, the length of the optical fiber will inevitably undergo a subtle but accurately measurable change. In this embodiment, the mass of the first mass block 14 and the second mass block 16 is less than or equal to 8 grams; the diameter of the central hollow circular hole of the first mass block 14 and the second mass block 16 is less than or equal to 2 mm. The diameter of the metal diaphragm 15 is less than or equal to 15 mm, the thickness is less than or equal to 0.3 mm, and the diameter of the central hollow circular hole is less than or equal to 2 mm. The resonant frequency of the spring oscillator type optical fiber accelerometer composed of the sensing optical fiber, the mass block and the metal diaphragm can be calculated by formula (1):

[0048] (1);

[0049] Where, f0 represents the natural frequency of the fiber optic accelerometer, m represents the total mass of the mass block, R represents the outer diameter of the metal diaphragm, r represents the inner diameter of the metal diaphragm, E represents the elastic modulus of the metal diaphragm, v represents the Poisson's ratio of the metal diaphragm, and h represents the thickness of the metal diaphragm.

[0050] Dynamic sensitivity of fiber optic accelerometer M It can be expressed as:

[0051] (2);

[0052] Where M0 is the static voltage sensitivity of the fiber optic accelerometer, and ϵ represents the damping ratio of the fiber optic accelerometer.

[0053] As a key medium for optical signal transmission, sensing optical fiber plays a vital role in pipeline leakage monitoring scenarios. When abnormal conditions occur in the surrounding environment of the pipeline system, such as small vibrations caused by pipeline leakage, the spring oscillator structure in which the optical fiber is located will produce a corresponding vibration response, which will cause extremely subtle changes in the length of the optical fiber. This slight change in length will directly have a significant impact on the optical properties of light propagating in the optical fiber, among which the change in optical path is particularly critical, which will further cause changes in the phase, amplitude and other related parameters of the light. With a high-precision optical detection system, the subtle changes in these optical signals during the propagation process can be accurately captured and analyzed. Through demodulation algorithms and signal processing processes, the changes in these optical parameters are converted into optical signal change data that can be accurately quantified, and these data are closely related to the characteristics of external vibration signals. In this way, accurate perception and measurement of vibration signals caused by pipeline leakage can be achieved.

[0054] The integrated housing 19 is designed to consist of two parts, an upper housing and a lower housing. Its core function is to provide a comprehensive and reliable packaging protection mechanism for the precision spring oscillator structure jointly constructed by the sensing optical fiber 11, the mass block and the metal diaphragm 15.

[0055] like Figure 1 As shown, the upper shell and the lower shell of the integrated housing 19 are tightly matched in structure, and are firmly connected and fixed by the first screw 17 and the second screw 18, ensuring the stability and sealing of the entire packaging structure. This connection method not only effectively prevents external dust, water vapor and other possible pollutants from eroding and interfering with the internal sensitive structure, but also can resist the adverse effects of external mechanical shock and vibration on the spring oscillator structure to a certain extent, thereby providing a solid physical protection foundation for the stable and accurate operation of the fiber optic accelerometer in a complex and changeable actual working environment, ensuring the reliability and stability of its various performance indicators, extending its service life, and strongly supporting the efficient and continuous operation of the entire fiber optic accelerometer system in actual application scenarios.

[0056] FIG3 is a flow chart of a method for manufacturing a fiber optic accelerometer according to an embodiment of the present invention. As shown in FIG3 , the manufacturing method includes: first, processing the sensing optical fiber 11 by chemical etching or hot-melt taper to prepare the taper structure 13, and coating the end face of the sensing optical fiber with metal or multi-layer dielectric by magnetron sputtering to form a high-reflection film 12.

[0057] Next, a through hole is formed in the middle of the first mass block 14, the metal diaphragm 15 and the second mass block 16 by using mechanical or laser drilling technology. After that, the sensing optical fiber is passed through the upper shell of the integrated housing 19, the first mass block 14, the metal diaphragm 15 and the second mass block 16 in sequence, and optical glue is used to glue and fix the contact interface between the optical fiber and the mass block to ensure that the sensing optical fiber 11 is in a straightened state inside the mass block.

[0058] Finally, the integrated housing 19 consists of an upper shell and a lower shell. The two parts are tightly matched in structure and are firmly connected and fixed by a first screw 17 and a second screw 18, thereby ensuring the stability and sealing of the entire packaging structure and providing reliable protection for the internal structure of the fiber optic accelerometer.

[0059] FIG4 is a diagram of a pipeline leakage sensing system based on a time division multiplexing device according to an embodiment of the present invention. Figure 4 As shown, the sensing system includes: a narrow linewidth laser 31, an optical isolator 32, a first fiber coupler 33, a first circulator 34, a second circulator 35, a second fiber coupler 39, a first polarization controller 36, a second polarization controller 37, a first optical switch 315, a second optical switch 316, a first fiber accelerometer 317, a second fiber accelerometer 318, a third fiber coupler 310, a fourth fiber coupler 312, a first photodetector 311, a second photodetector 313, a phase generation carrier unit 38 and a signal acquisition processing unit 314.

[0060] In this embodiment, the fiber optic accelerometer includes a sensing fiber 11, a first mass block 14, a metal diaphragm 15, a second mass block 16, and an integrated housing 19; a tapered structure 13 is made on the sensing fiber and a high-reflection film 12 is plated at its end; the integrated housing 19 consists of an upper shell and a lower shell; through holes are made in the upper shell, the first mass block 14, the second mass block 16 and the metal diaphragm 15 of the integrated housing 19; the sensing fiber 11 passes through the upper shell, the first mass block 14, the metal diaphragm 15 and the second mass block 16 of the integrated housing 19 in sequence; the lower shell and the upper shell of the integrated housing 19 are fixed together to encapsulate the spring oscillator structure composed of the sensing fiber 11, the first mass block 14, the metal diaphragm 15 and the second mass block 16.

[0061] In this embodiment, the detection light source is a narrow line width laser 31, and the light emitted is the detection light, and its wavelength is around 1550 nanometers, for example, it can be 1550 nanometers ± 5 nanometers, and the present invention is not limited to this. In other embodiments, the detection light source can be a light source with other wavelength ranges; the pumping form can be thermal pumping, etc.

[0062] In this embodiment, the first multiplexing device is a first optical switch 315 , and the second multiplexing device is a second optical switch 316 .

[0063] In this embodiment, the phase generation carrier unit 38 is used to generate a carrier signal, and uses piezoelectric ceramics, single-mode optical fiber and a signal generator. The single-mode optical fiber is tightly wound on the piezoelectric ceramics, the signal generator is used to excite the piezoelectric ceramics, and the characteristic frequency of the piezoelectric ceramics is less than or equal to 1 kHz, and the winding length of the single-mode optical fiber is less than or equal to 1 meter. The phase generation carrier unit 38 precisely modulates the phase of the signal light, combines it with the detection light returned by the optical fiber accelerometer, and finally measures the pipeline vibration signal.

[0064] In this embodiment, the signal acquisition processing unit 314 includes an acquisition card and a host computer processing program. The acquisition card has two independent data transmission channels, which respectively receive electrical signals from the first photodetector 311 and the second photodetector 313, and enter the acquisition card through high-speed sampling, with a sampling rate of up to 250 MHz, to meet the system's requirements for real-time capture and accurate detection of high-frequency signals.

[0065] The received signal is then demodulated by the host computer processing program, which uses a series of algorithms based on phase generation carrier demodulation technology to process the signal in detail. First, the DC component in the electrical signal is removed through signal de-DC processing to ensure that only the AC signal related to vibration is retained. Then, the signal is mixed with the carrier signal to generate a difference frequency signal to improve the resolution of low-frequency signals. Next, a low-pass filter operation removes high-frequency noise, retains useful vibration signals, and improves the signal-to-noise ratio. The differential operation further enhances the dynamically changing part of the signal, making the vibration characteristics more obvious. The signal differentiation step extracts the change rate information of the signal, especially for rapidly changing vibration signals, which can more accurately capture the subtle changes in the early stage of pipeline leakage. Through signal integration, the amplitude characteristics of the vibration signal are restored to optimize the demodulation effect. Finally, a high-pass filter is used to remove low-frequency noise to ensure the system's accurate analysis of high-frequency vibration signals.

[0066] These demodulation technologies effectively improve the system's ability to demodulate vibration signals of different frequencies and intensities, ensuring that whether it is a weak initial leakage signal or a large-amplitude vibration signal, the vibration characteristic information can be accurately extracted to achieve high-precision and large dynamic range pipeline leakage monitoring.

[0067] In the working process of the system, the light emitted by the narrow linewidth laser 31 is divided into three after passing through the optical isolator 32 and the first optical fiber coupler 33, forming a first detection light, a second detection light and a third detection light.

[0068] The first detection light is transmitted to the first light outlet of the first circulator 34, the second light outlet of the first circulator 34 is connected to the first optical switch 315, the first optical switch 315 can be connected to one or more fiber optic accelerometers, and the return light passes through the third light outlet of the first circulator 34 and then enters the third fiber optic coupler 310 via the first polarization controller 36, is received by the first photodetector 311, and then passes through the signal acquisition and processing unit 314.

[0069] The second detection light is transmitted to the second light outlet of the second circulator 35, and the second light outlet of the second circulator 35 is connected to the second optical switch 316. The second optical switch 316 can be connected to one or more fiber optic accelerometers. The return light passes through the third light outlet of the second circulator 35 and then enters the fourth fiber optic coupler 312 via the second polarization controller 37, and is received by the second photodetector 313, and then passes through the signal acquisition and processing unit 314.

[0070] The third detection light passes through the phase generating carrier unit 38 and is divided into two parts via the second optical fiber coupler 39. One part passes through the third optical fiber coupler 310 and the signal combination of the first optical fiber accelerometer 317 connected to the first optical switch 315, is received by the first photodetector 311, and then passes through the signal acquisition and processing unit 314; the other part passes through the fourth optical fiber coupler 312 and the signal combination of the second optical fiber accelerometer 318 connected to the second optical switch 316, is received by the second photodetector 313, and then passes through the signal acquisition and processing unit 314.

[0071] The signal acquisition processing unit demodulates the electrical signals from the first photodetector 311 and the second photodetector 313 to extract vibration characteristic information and restore the signals, thereby achieving high-precision detection of pipeline vibration signals.

[0072] The working principle of the pipeline leakage system based on fiber optic accelerometer is as follows:

[0073] When a pipeline leaks, the pressure change generated at the leak point triggers a pipeline vibration wave, which is transmitted to the fiber optic accelerometer. The spring oscillator structure composed of the sensing fiber, mass block and metal diaphragm responds to the vibration. Among them, the sensing fiber is tightly embedded in the mass block in a straightened state. This tight and stable connection method ensures that the vibration of the spring oscillator structure can be effectively transmitted to the sensing fiber, causing the length of the sensing fiber to change slightly but measurably during the vibration process. The change in the length of the sensing fiber will further cause corresponding changes in physical quantities such as optical path and refractive index inside the sensing fiber, thereby modulating the optical signal transmitted in the sensing fiber.

[0074] The light emitted by the detection light source first enters the phase generation carrier unit, in which the phase of the signal light is precisely modulated according to a specific carrier signal, and then combined with the detection light returned from the fiber optic accelerometer. The combined light beam is finally received by the photodetector. The photodetector converts the optical signal into an electrical signal, and these electrical signals carry the vibration information sensed by the fiber optic accelerometer. Next, the signal acquisition and processing unit demodulates the electrical signal output by the photodetector, extracts and restores the vibration characteristic information in the electrical signal through algorithms and signal processing procedures, and finally realizes high-precision detection of pipeline vibration signals. It is worth noting that in the structural design of the fiber optic accelerometer, the spring oscillator structure can produce more significant displacement changes when subjected to the same magnitude of vibration force, thereby enabling the optical fiber to more sensitively sense the vibration information, effectively improving the sensitivity performance of the fiber optic accelerometer.

[0075] At the same time, the demodulation technology based on phase-generated carrier plays a key role in the entire signal processing process. This technology can efficiently and accurately demodulate the optical signals corresponding to vibration signals of different intensities and frequencies, thereby achieving a large dynamic range of signal demodulation capabilities, ensuring that both weak vibration signals at the initial stage of leakage and large amplitude vibration signals generated under some complex working conditions can be accurately demodulated and restored, meeting the stringent requirements of pipeline leakage monitoring for vibration signal detection in different scenarios.

[0076] From the perspective of the overall system architecture, the signal demodulation system has a simple and clear structural design, and all the various devices used have cost advantages, without the need for expensive high-end equipment and complex manufacturing processes. This simple and low-cost design concept enables the entire fiber optic accelerometer system to effectively control costs while achieving high-precision, large dynamic range vibration signal detection, and has the economic feasibility of being widely used and promoted in large-scale pipeline leakage monitoring networks.

[0077] The main function of the optical switch is to act as a time-division multiplexing device. By switching, it can detect pipeline vibration signals at different locations, so that multiple accelerometers can share a system. Specifically, the optical switch can obtain a set of accelerometer signals at different locations in sequence in different time periods, and transmit a set of vibration signals at each location to the system for processing. This time-division multiplexing method can not only reduce the hardware cost of the system and reduce the need for multiple independent signal processing channels, but also improve the overall efficiency of the system. By switching the optical switch, the system can share resources between multiple accelerometers, realize real-time monitoring of different parts of the pipeline, and ensure that the vibration signals at each location can be accurately collected and analyzed. Therefore, the optical switch plays a key role in the pipeline monitoring system, improving the scalability and cost-effectiveness of the system.

[0078] FIG4 also shows a typical schematic diagram of the deployment of fiber optic accelerometers on a pipeline for monitoring pipeline leakage. Figure 4 In the example, a pair of fiber optic accelerometers (first fiber optic accelerometer 317 and second fiber optic accelerometer 318) do not need to be buried underground, but are firmly installed on the surface of the pipeline to ensure that the sensor can stably obtain the vibration signal of the pipeline. 319 shows the pipeline body, and 320 is the marked leakage point. When a leakage occurs, it will cause abnormal flow of fluid inside the pipeline, thereby generating specific vibration signals. These vibration signals are captured and monitored in real time by reasonably arranged fiber optic accelerometers.

[0079] The installation location of the fiber optic accelerometer follows specific layout rules. These rules are based on a comprehensive analysis of the length, direction, branching of the pipeline, and historical leakage data to ensure that the installed sensor can obtain the most representative and sensitive vibration signal. In addition, the determination of the installation location also fully considers the distribution of vibration sources in the surrounding environment. By analyzing the ambient vibration spectrum, the fiber optic accelerometer is placed in a location with less vibration interference to further improve the accuracy and reliability of leakage signal detection. Therefore, by scientifically arranging fiber optic accelerometers, the vibration characteristics of the pipeline leakage area can be effectively monitored to achieve accurate leakage detection.

[0080] FIG5 is a diagram of a pipeline leakage sensing system based on a wavelength division multiplexing device according to an embodiment of the present invention. Figure 5As shown, the sensing system includes: a tunable laser 41, an optical isolator 32, a first fiber coupler 33, a first circulator 34, a second circulator 35, a second fiber coupler 39, a first polarization controller 36, a second polarization controller 37, a first wavelength division multiplexer 42, a second wavelength division multiplexer 43, a first fiber accelerometer 317, a second fiber accelerometer 318, a third fiber coupler 310, a fourth fiber coupler 312, a first photodetector 311, a second photodetector 313, a phase generation carrier unit 38 and a signal acquisition processing unit 314.

[0081] In this embodiment, the fiber optic accelerometer includes a sensing fiber 11, a first mass block 14, a metal diaphragm 15, a second mass block 16, and an integrated housing 19; a tapered structure 13 is made on the sensing fiber and a high-reflection film 12 is plated at its end; the integrated housing 19 consists of an upper shell and a lower shell; through holes are made in the upper shell, the first mass block 14, the second mass block 16 and the metal diaphragm 15 of the integrated housing 19; the sensing fiber 11 passes through the upper shell, the first mass block 14, the metal diaphragm 15 and the second mass block 16 of the integrated housing 19 in sequence; the lower shell and the upper shell of the integrated housing 19 are fixed together to encapsulate the spring oscillator structure composed of the sensing fiber 11, the first mass block 14, the metal diaphragm 15 and the second mass block 16.

[0082] In this embodiment, the detection light source is a tunable laser 41, and the light emitted is the detection light; the tunable laser is finely adjusted at different wavelengths, providing flexible light source selection.

[0083] In this embodiment, the first multiplexing device uses a first wavelength division multiplexer 42, and the second multiplexing device uses a second wavelength division multiplexer 43.

[0084] In this embodiment, the phase generation carrier unit 38 is used to generate a carrier signal, and uses piezoelectric ceramics, single-mode optical fiber and a signal generator. The single-mode optical fiber is tightly wound on the piezoelectric ceramics, the signal generator is used to excite the piezoelectric ceramics, and the characteristic frequency of the piezoelectric ceramics is less than or equal to 1 kHz, and the winding length of the single-mode optical fiber is less than or equal to 1 meter. The phase generation carrier unit 38 precisely modulates the phase of the signal light, combines it with the detection light returned by the optical fiber accelerometer, and finally measures the pipeline vibration signal.

[0085] In this embodiment, the signal acquisition processing unit 314 includes an acquisition card and a host computer processing program. The acquisition card has two independent data transmission channels, which respectively receive electrical signals from the first photodetector 311 and the second photodetector 313, and enter the acquisition card through high-speed sampling, with a sampling rate of up to 250 MHz, to meet the system's requirements for real-time capture and accurate detection of high-frequency signals.

[0086] The received signal is then demodulated by the host computer processing program, which uses a series of algorithms based on phase generation carrier demodulation technology to process the signal in detail. First, the DC component in the electrical signal is removed through signal de-DC processing to ensure that only the AC signal related to vibration is retained. Then, the signal is mixed with the carrier signal to generate a difference frequency signal to improve the resolution of low-frequency signals. Next, a low-pass filter operation removes high-frequency noise, retains useful vibration signals, and improves the signal-to-noise ratio. The differential operation further enhances the dynamically changing part of the signal, making the vibration characteristics more obvious. The signal differentiation step extracts the change rate information of the signal, especially for rapidly changing vibration signals, which can more accurately capture the subtle changes in the early stage of pipeline leakage. Through signal integration, the amplitude characteristics of the vibration signal are restored to optimize the demodulation effect. Finally, a high-pass filter is used to remove low-frequency noise to ensure the system's accurate analysis of high-frequency vibration signals.

[0087] These demodulation technologies effectively improve the system's ability to demodulate vibration signals of different frequencies and intensities, ensuring that whether it is a weak initial leakage signal or a large-amplitude vibration signal, the vibration characteristic information can be accurately extracted to achieve high-precision and large dynamic range pipeline leakage monitoring.

[0088] In the working process of the system, the light emitted by the tunable laser 41 is divided into three after passing through the optical isolator 32 and the first optical fiber coupler 33, forming a first detection light, a second detection light and a third detection light.

[0089] The first detection light is transmitted to the first light output port of the first circulator 34, the second light output port of the first circulator 34 is connected to the first wavelength division multiplexer 42, the first wavelength division multiplexer 42 can be connected to one or more fiber optic accelerometers, and the return light passes through the third light output port of the first circulator 34 and then enters the third fiber optic coupler 310 via the first polarization controller 36, is received by the first photodetector 311, and then passes through the signal acquisition and processing unit 314.

[0090] The second detection light is transmitted to the second light output port of the second circulator 35, and the second light output port of the second circulator 35 is connected to the second wavelength division multiplexer 43. The second wavelength division multiplexer 43 can be connected to one or more fiber optic accelerometers. The return light passes through the third light output port of the second circulator 35 and then enters the fourth fiber optic coupler 312 via the second polarization controller 37, is received by the second photodetector 313, and then passes through the signal acquisition and processing unit 314.

[0091] The third detection light passes through the phase generating carrier unit 38 and is divided into two parts via the second optical fiber coupler 39. One part passes through the third optical fiber coupler 310 and the signal combination of the first optical fiber accelerometer 317 connected to the first wavelength division multiplexer 42, is received by the first photodetector 311, and then passes through the signal acquisition and processing unit 314; the other part passes through the fourth optical fiber coupler 312 and the signal combination of the second optical fiber accelerometer 318 connected to the second wavelength division multiplexer 43, is received by the second photodetector 313, and then passes through the signal acquisition and processing unit 314.

[0092] The signal acquisition processing unit demodulates the electrical signals from the first photodetector 311 and the second photodetector 313 to extract vibration characteristic information and restore the signals, thereby achieving high-precision detection of pipeline vibration signals.

[0093] When a pipeline leaks, the pressure change generated at the leak point triggers pipeline vibration waves, which are transmitted to the fiber optic accelerometer. The spring oscillator structure composed of the sensing fiber, mass block and metal diaphragm responds to the vibration, and the length of the sensing fiber changes slightly, thereby modulating the optical signal. Through the phase generation carrier unit and signal demodulation technology, the system can efficiently and accurately demodulate the optical signal, extract vibration signals of different frequencies and intensities, and has a signal demodulation capability with a large dynamic range. This enables the system to accurately detect pipeline leaks at different vibration signal intensities and meet the monitoring needs under complex working conditions.

[0094] The main function of the wavelength division multiplexer is to multiplex and separate multiple signals through optical signals of different wavelengths, thereby realizing the simultaneous transmission and independent processing of multiple signals. Specifically, the wavelength division multiplexer can convert pipeline vibration signals at different locations into optical signals of different wavelengths and transmit them simultaneously through channels of different wavelengths. This method enables multiple accelerometers to transmit vibration signals at their respective locations to the system for processing at the same time through different optical wavelengths.

[0095] The wavelength division multiplexer avoids the overlap and interference of multiple signal channels by multiplexing the signals by wavelength, thereby improving the signal processing efficiency of the system. At the same time, wavelength division multiplexing technology can greatly reduce hardware costs, because multiple signals can share the same optical fiber channel for transmission, reducing the demand for optical fiber and transmission channels. In addition, the wavelength division multiplexer can improve the signal transmission capacity and the overall performance of the system without increasing the complexity of the system, so that the vibration signals of different parts of the pipeline can be transmitted simultaneously without interfering with each other, thereby realizing efficient monitoring and accurate analysis of the pipeline. Therefore, the wavelength division multiplexer plays a vital role in the pipeline monitoring system, not only improving the transmission efficiency and reliability of the system, but also enhancing the scalability and economy of the system.

[0096] Figure 5 It also shows a typical layout diagram of fiber optic accelerometers on pipelines to monitor pipeline leakage. Figure 5 In the embodiment, a pair of fiber optic accelerometers (first fiber optic accelerometer 317 and second fiber optic accelerometer 318) do not need to be buried underground, but are firmly installed on the surface of the pipeline to ensure that the sensor can stably obtain the vibration signal of the pipeline. 319 shows the pipeline body, and 320 is the marked leakage point. When a leakage occurs, it will cause abnormal flow of fluid inside the pipeline, thereby generating specific vibration signals. These vibration signals are captured and monitored in real time by the fiber optic accelerometers that are reasonably arranged.

[0097] The installation location of the fiber optic accelerometer follows specific layout rules. These rules are based on a comprehensive analysis of the length, direction, branching of the pipeline, and historical leakage data to ensure that the installed sensor can obtain the most representative and sensitive vibration signal. In addition, the determination of the installation location also fully considers the distribution of vibration sources in the surrounding environment. By analyzing the ambient vibration spectrum, the fiber optic accelerometer is placed in a location with less vibration interference to further improve the accuracy and reliability of leakage signal detection. Therefore, by scientifically arranging fiber optic accelerometers, the vibration characteristics of the pipeline leakage area can be effectively monitored to achieve accurate leakage detection.

[0098] Please refer to FIG6 , which is a schematic diagram of a pipeline leakage monitoring method according to an embodiment of the present invention. As shown in FIG6 , the curves in the figure represent the first optical signal 51 and the second optical signal 52 obtained by a pair of optical fiber accelerometers when the pipeline vibrates, and there is a certain time delay between the two signals. When a pipeline leaks, the vibration signal caused by the leak propagates to the two accelerometers at different times, resulting in a shift in the main peak position of the cross-correlated optical signal of the signal detected by the two accelerometers. According to the position of the main peak shift, the time delay ∆t can be calculated by the formula to further locate the specific position of the leak point on the pipeline.

[0099] In this embodiment, regarding the calculation of the delay:

[0100] Assume that the speed of the vibration signal caused by leakage propagating between the two sensors is v , the distance between the two sensors is d The time delay ∆t can be calculated from the cross-correlation main peak position drift of the two signals. Formula (3) is:

[0101] (3);

[0102] where ∆ x is the number of sample points for the main peak drift, f s is the sampling frequency of the signal.

[0103] In this embodiment, the calculation of the leakage point location is:

[0104] Based on the time delay ∆t, the location of the leak can be further determined. Assume that the distance from the leak point on the pipeline to an accelerometer is L 1, the distance to the other accelerometer is L 2, then:

[0105] (4);

[0106] By combining the above equations, the distance from the leak point to the first accelerometer is L 1 can be expressed as:

[0107] (5);

[0108] Correspondingly, the distance from the leak point to the second accelerometer L 2 is:

[0109] (6).

[0110] The technical features of the above-described embodiments can be further combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention is given by the attached claims and any equivalent technical solutions thereof.

Claims

1. A fiber optic accelerometer, characterized in that: The invention comprises a sensing optical fiber (11), a first mass block (14), a metal diaphragm (15), a second mass block (16), and an integrated housing (19); a tapered structure (13) is formed on the sensing optical fiber, and a high-reflection film (12) is plated on the end of the sensing optical fiber; the integrated housing (19) is composed of an upper housing and a lower housing; through holes are respectively formed on the upper housing, the first mass block (14), the second mass block (16), and the metal diaphragm (15) of the integrated housing (19) for the sensing optical fiber (11) to pass through in sequence; the center portion of the metal diaphragm (15) is tightly clamped by the first mass block (14) and the second mass block (16); the edge portion of the metal diaphragm (15) is fixed together by the lower housing and the upper housing of the integrated housing (19), thereby encapsulating a spring oscillator structure formed by the sensing optical fiber (11), the first mass block (14), the metal diaphragm (15), and the second mass block (16).

2. The fiber optic accelerometer according to claim 1, characterized in that: The metal diaphragm (15) is made of beryllium copper.

3. The fiber optic accelerometer according to claim 1, characterized in that: The sensing optical fiber (11) is prepared into a tapered structure (13) by chemical etching or hot-melt tapering; the central part of the metal diaphragm (15) is tightly clamped by the first mass block (14) and the second mass block (16) by magnetic attraction or gluing; the first mass block (14), the metal diaphragm (15) and the second mass block (16) are formed with a through hole in the middle by mechanical or laser drilling technology; the end of the sensing optical fiber (11) is plated with metal or multi-layer medium by magnetron sputtering to form a high-reflection film (12) for enhancing the reflected signal; the upper shell and the lower shell of the integrated shell (19) are fixed by a first screw (17) and a second screw (18).

4. A pipeline leakage sensing system, characterized in that: The optical fiber accelerometer comprises a detection light source, an optical isolator (32), a first optical fiber coupler (33), a first circulator (34), a second circulator (35), a first polarization controller (36), a second polarization controller (37), a phase generation carrier unit (38), a second optical fiber coupler (39), a third optical fiber coupler (310), a first photodetector (311), a fourth optical fiber coupler (312), a second photodetector (313), a signal acquisition processing unit (314), a first multiplexing device, a second multiplexing device, a first optical fiber accelerometer (317), and a second optical fiber accelerometer (318); the first optical fiber accelerometer (317) and the second optical fiber accelerometer (318) are optical fiber accelerometers according to claim 1; The detection light source is a narrow line width laser (31) or a tunable laser (41); the light emitted by the detection light source is split into three after passing through the optical isolator (32) and the first optical fiber coupler (33), forming a first detection light, a second detection light and a third detection light; The first detection light is transmitted to a first light outlet of a first circulator (34); a second light outlet of the first circulator (34) is connected to a first multiplexing device; the first multiplexing device is connected to one or more optical fiber accelerometers; the return light passes through a third light outlet of the first circulator (34) and then enters a third optical fiber coupler (310) via a first polarization controller (36), is received by a first photodetector (311), and then passes through a signal acquisition processing unit (314); The second detection light is transmitted to the second light output port of the second circulator (35), the second light output port of the second circulator (35) is connected to the second multiplexing device, the second multiplexing device is connected to one or more optical fiber accelerometers, and the return light passes through the third light output port of the second circulator (35) and then enters the fourth optical fiber coupler (312) via the second polarization controller (37), is received by the second photodetector (313), and then passes through the signal acquisition processing unit (314); The third detection light passes through the phase generation carrier unit (38) and is split into two via the second optical fiber coupler (39); one path passes through the third optical fiber coupler (310) and the signal beam of the optical fiber accelerometer connected to the first multiplexing device, is received by the first photodetector (311), and then passes through the signal acquisition processing unit (314); the other path passes through the fourth optical fiber coupler (312) and the signal beam of the optical fiber accelerometer connected to the second multiplexing device, is received by the second photodetector (313), and then passes through the signal acquisition processing unit (314); When the first multiplexing device and the second multiplexing device are time division multiplexing devices, they are the first optical switch (315) and the second optical switch (316); or when the first multiplexing device and the second multiplexing device are wavelength division multiplexing devices, they are the first wavelength division multiplexer (42) and the second wavelength division multiplexer (43); the phase generation carrier unit (38) is used to generate a carrier signal; The first photodetector (311) and the second photodetector (313) are used to convert received optical signals into electrical signals; The signal acquisition processing unit (314) is used to demodulate the electrical signals output by the first photodetector (311) and the second photodetector (313).

5. The pipeline leakage sensing system according to claim 4, characterized in that: The phase generation carrier unit (38) comprises piezoelectric ceramics, single-mode optical fiber and a signal generator; the single-mode optical fiber is tightly wound around the piezoelectric ceramics, and the signal generator is used to apply an excitation signal to the piezoelectric ceramics.

6. The pipeline leakage sensing system according to claim 4, characterized in that: The signal acquisition processing unit (314) comprises an acquisition card and a host computer processing program; the acquisition card has two data transmission channels, which respectively receive electrical signals from the first photodetector (311) and the second photodetector (313).

7. The pipeline leakage sensing system according to claim 6, characterized in that: The host computer processing program demodulates the signal received by the acquisition card based on the algorithm of phase-generated carrier demodulation technology; the algorithm based on phase-generated carrier demodulation technology includes signal DC removal processing, signal mixing, low-pass filtering, signal difference, signal differentiation, signal integration, and high-pass filtering.

8. The pipeline leakage sensing system according to claim 4, characterized in that: The installation positions of the multiple fiber optic accelerometers connected to the first multiplexing device and the second multiplexing device on the pipeline follow specific layout rules, which are determined based on the length, direction, branching conditions and historical leakage data of the pipeline to ensure that the most representative and sensitive vibration signals can be obtained, thereby improving the accuracy and reliability of leakage monitoring. The method for determining the installation position also takes into account the distribution of vibration sources in the surrounding environment. By analyzing the environmental vibration spectrum, the fiber optic accelerometer is installed at a location with less vibration interference.

9. A pipeline leakage monitoring method based on cross-correlation operation, characterized in that: The pipeline leakage sensing system according to claim 4 comprises the following steps: using a pair of fiber optic accelerometers, the fiber optic accelerometer connected to the first multiplexing device and the fiber optic accelerometer connected to the second multiplexing device to detect the pipeline and obtain corresponding vibration signals; performing cross-correlation operation on the signals detected by the pair of fiber optic accelerometers after demodulation by the signal acquisition and processing unit; observing the peak deviation of the cross-correlation optical signal and determining the peak position by an accurate peak detection algorithm, wherein the peak detection algorithm can accurately identify the main peak and the secondary peak of the cross-correlation optical signal in the presence of noise and signal fluctuations, and record the position information, and calculate the time delay of the two signals according to the change of the peak position, so as to calculate the specific position of the pipeline leakage.

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