Gas pipeline vibration measurement system and method based on optical fiber sensors

Abstract

The present invention discloses a gas pipeline vibration measurement system and method based on fiber optic sensors. The system includes: a transmitting end, which includes a white light source, a multi-stage optical beam splitter module arranged downstream of the white light source, and an optical fiber circulator array arranged downstream of the multi-stage optical beam splitter module; a receiving end, which includes a multi-stage optical combiner module, a tunable optical filter, a photodetector, a low-noise amplifier circuit, a low-pass filter circuit, and a signal processing module that are signal-connected to the optical fiber circulator array. Thereby, the temperature interference problem of the gas pipeline vibration detection sensing network based on fiber optic sensors is solved. At the same time, through various sensor installation methods, the detection method increases the dimension of sensing information, reduces the complexity of the equipment, and reduces the equipment cost.

Description

Technical Field

[0001] The present invention relates to the technical field of gas pipeline safety protection, and particularly to a gas pipeline vibration measurement system and method based on an optical fiber sensor. Background Art

[0002] The information provided in this part is only background information related to the present disclosure, and it is not necessarily prior art.

[0003] As an important infrastructure for industrial production and urban civil use, gas pipelines play an important role in urban development and people's daily life. As a carrier device for flammable and explosive dangerous gases such as natural gas, liquefied petroleum gas, and coal gas, once leakage occurs, it will pose a great social danger and also cause huge economic losses to gas companies. Therefore, the safe operation of urban gas pipelines is of great significance to social economy, production and life, and people's well-being.

[0004] There are many inducements for gas pipeline leakage, such as pipeline aging, corrosion, natural or man-made damage, etc. Therefore, the manifestations during damage are also diverse, and there are many detection methods: sectional pressure method, magnetic flaw detection method, negative pressure method, vibration detection method, etc. However, traditional manual maintenance has poor real-time performance and relatively low efficiency. In order to improve the system stability, it is very necessary to introduce automation technology for safety monitoring.

[0005] Currently, in the method of gas pipeline vibration detection based on optical fiber sensors, most optical fiber sensors sense environmental vibration based on the elasto-optic effect or backscattering principle of optical fiber materials. Sensors based on this mechanism mostly use fiber grating structures, interferometric fiber structures, or backscattering distributed optical fiber sensing structures to work and have the ability to sense pipeline vibration. However, they are also affected by factors such as thermal effects and fiber deformation, resulting in coupling interference problems of irrelevant quantities such as temperature and static stress, easily obtaining incorrect recognition results and generating false alarms, which greatly reduces the accuracy and stability of the sensing system. In addition, the existing detection methods utilize the elasto-optic effect of optical fibers and cannot identify the vibration direction generated by the pipeline. Their sensing results are the comprehensive influence of vibration on the deformation of the optical fiber, and only a single-dimensional sensing signal can be provided, unable to provide more-dimensional information for vibration mode recognition. At the same time, some traditional pipeline vibration sensing methods detect the change in spectral wavelength, which also poses challenges to the complexity and cost of the demodulation device; there is also a distributed optical fiber sensing system using backscattering, which has high requirements for the light source power, and the energy of the reflected sensing signal is weak, and also has high requirements for the denoising algorithm of the demodulation device. Summary of the Invention

[0006] The object of the present invention is to provide a gas pipeline vibration measurement system and method based on an optical fiber sensor, so as to at least partially solve the problems that existing sensors are vulnerable to crosstalk of irrelevant factors such as temperature and the accuracy of gas pipeline safety monitoring is relatively low; as well as the technical problems of single-dimensional sensing signals and high system complexity. This object is achieved through the following technical solutions:

[0007] The present invention provides a gas pipeline vibration measurement system based on an optical fiber sensor, and the optical fiber sensor includes:

[0008] Single-mode optical fiber segments, and there are two single-mode optical fiber segments;

[0009] A hollow-core optical fiber segment, which is arranged between the two single-mode optical fiber segments and forms an anti-resonant optical waveguide structure;

[0010] An inner-coated capillary glass tube, which is sleeved on the outer peripheries of the single-mode optical fiber segments and the hollow-core optical fiber segment;

[0011] The system includes:

[0012] A transmitting end, which includes a white light source, a multi-stage optical beam splitter module arranged downstream of the white light source, and an optical fiber circulator array arranged downstream of the multi-stage optical beam splitter module;

[0013] A receiving end, which includes a multi-stage optical combiner module, a tunable optical filter, a photodetector, a low-noise amplification circuit, a low-pass filtering circuit, and a signal processing module that are signal-connected to the optical fiber circulator array.

[0014] Further, the signal processing module includes:

[0015] An AD data acquisition module, a positioning algorithm module, a multi-dimensional vibration data sorting module, and a pattern recognition and threshold processing module.

[0016] Further, the multi-stage optical beam splitter module includes: multi-stage optical beam splitter components arranged in sequence;

[0017] Among them,

[0018] The first-stage optical beam splitter component includes a single 1×n optical beam splitter, and its incident port is connected to the light source end;

[0019] The second-stage optical beam splitter component includes n 1×n optical beam splitters, and the incident ports of the 1×n optical beam splitters are connected to the output ports of the 1×n optical beam splitter of the previous stage;

[0020] The third-stage optical beam splitter component includes n 2One 1×n optical splitter, and the input ports of each of the 1×n optical splitters are connected to the output ports of the 1×n optical splitters at the previous level;

[0021] And so on, the j-th stage optical beam combining component includes n (j-1) One 1×n optical splitter, and the input ports of each of the 1×n optical splitters are connected to the output ports of the 1×n optical splitters at the previous level.

[0022] Furthermore, the multi-stage optical beam combining module includes: multi-stage optical beam combining components arranged in sequence;

[0023] Wherein,

[0024] The first-stage optical beam combining component includes one 1×n optical beam combiner, and its input port is connected to the light source end;

[0025] The second-stage optical beam combining component includes n 1×n optical beam combiners, and the input ports of each of the 1×n optical beam combiners are connected to the output ports of the 1×n optical beam combiners at the previous level;

[0026] The third-stage optical beam combining component includes n 2 One 1×n optical beam combiner, and the input ports of each of the 1×n optical beam combiners are connected to the output ports of the 1×n optical beam combiners at the previous level.

[0027] And so on, the j-th stage optical beam combining component includes n (j-1) One 1×n optical beam combiner, and the input ports of each of the 1×n optical beam combiners are connected to the output ports of the 1×n optical beam combiners at the previous level.

[0028] The present invention also provides a method for measuring the vibration of a gas pipeline, based on the optical fiber sensor as described above, the method includes:

[0029] S1: Prepare the optical fiber sensor, and arrange a plurality of the optical fiber sensors on the gas pipeline in a preset manner;

[0030] S2: Connect a reflection filter to the end of each optical fiber sensor respectively, and the center wavelength of each reflection filter corresponds to the anti-resonant wavelength of each optical fiber sensor one by one, and a sensing network is formed;

[0031] S3: Connect each sensing node on the sensing network to the gas pipeline vibration measurement system through a single-mode optical fiber, and complete the wiring connection of the transmitting end and the receiving end;

[0032] S4: The vibration information collected from the sensing network is accessed to the receiving end of the gas pipeline vibration measurement system through the port of the optical fiber sensor;

[0033] S5: Connect the obtained sensing information array of a single sensor to the multi-dimensional vibration data processing module. According to the system pattern recognition requirements, determine the number of dimensions q of a single measurement point, and calculate the sensing information matrix of each point on this processing module. Among them, q ≥ 1;

[0034] S6: Conduct spectrum analysis on each fiber optic sensor according to the information matrix, and obtain the pipeline safety situation level warning based on the spectrum analysis results.

[0035] Furthermore, in step S3, connect each sensing node on the sensing network to the gas pipeline vibration measurement system through single-mode optical fibers, and complete the wiring connection of the transmitting end and the receiving end, specifically including:

[0036] The transmitting end injects stable light in the C+L band into the multi-stage optical beam splitting module through a white light source, and evenly divides the light into n j parts;

[0037] Connect to the input port of the fiber optic sensor, and connect out from the output port of the fiber optic sensor, and connect to the fiber optic bundle introduced by the gas pipeline in sequence.

[0038] Furthermore, in step S4, the vibration information collected from the sensing network is connected to the receiving end of the gas pipeline vibration measurement system through the ports of the fiber optic sensors, specifically including:

[0039] Connect to the multi-stage optical beam combining module, combine n j sensing signals into one optical signal and then connect to the tunable optical filter;

[0040] Expand the anti-resonant wavelengths of multiple said fiber optic sensors on the time axis, and use the time-division multiplexing method to filter out the signals of different anti-resonant wavelengths in combination with the control signal given by the positioning algorithm module;

[0041] Connect to the optoelectronic conversion module to convert the optical signal into a processable electrical signal;

[0042] Pass through the low-noise amplification and low-noise filtering module in sequence to obtain an optimized sensing analog signal, and this sensing analog signal reflects the light intensity value A reflected by the sensor i at a certain point on the pipeline at time T1 i_T1 ;

[0043] Connect this sensing analog signal to the AD data acquisition module for data acquisition, and convert the analog signal A i_T1 into a digital signal D i_T1 , and then connect to the positioning algorithm module to record the position information Address_i, and form an information array [D i_T1 , Address_i], and this information array contains the vibration information and position information at time T1;

[0044] Change the central wavelength of the tunable optical filter in sequence, collect the vibration information of each point on the pipeline in the sensing network once, and then cycle to collect the sensing information at different times according to this method;

[0045] Set the system time resolution as Δt, which means that each sensor collects sensing information every Δt, and the sensing information array [D i_T1 , D i_(T1+Δt) , …, D i_(T1+p*Δt) , Address_i] of each sensor in a time period can be obtained, and the p value is a parameter value determined based on signal processing requirements.

[0046] Furthermore, in step S6, perform spectral analysis on each fiber optic sensor according to the information matrix, and obtain the pipeline safety situation level warning based on the spectral analysis result, specifically including:

[0047] Input the information matrix into the pattern recognition and threshold module, and perform spectral analysis on each sensor through the sensing information matrix;

[0048] Combine the multi-dimensional information of a single point to perform corresponding pattern recognition analysis, and exclude the pipeline vibration data caused by non-pipeline leakage;

[0049] Combine the dynamic threshold to give a pipeline safety situation level warning for the valid data.

[0050] The vibration measurement system and method based on fiber optic sensors provided by the present invention change the traditional fiber optic sensing mechanism, introduce fiber optic sensors based on the anti-resonant principle, effectively solve the temperature interference problem of the entire sensing network, improve the performance of the fiber optic sensing network, and make the vibration measurement more accurate; at the same time, the installation method, sensing system networking method and sensing host system structure applied to the safety monitoring of gas pipelines increase the dimension of sensing information through various installation methods of sensors, providing a data basis for the pattern recognition of gas pipeline vibration signals. Thus, the temperature interference problem of the gas pipeline vibration detection sensing network based on fiber optic sensors is solved. At the same time, this detection method increases the dimension of sensing information through various sensor installation methods, reduces the complexity of the equipment, and reduces the equipment cost. Description of the Drawings

[0051] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0052] Figure 1 It is a schematic structural diagram of a specific embodiment of the fiber optic sensor provided by the present invention;

[0053] Figure 2 is Figure 1 a schematic diagram of the sensing mechanism during the vibration detection of the fiber optic sensor shown;

[0054] Figure 3 is a schematic diagram of the distribution of the sensors provided by the present invention in the vibration monitoring sensing network of the gas pipeline;

[0055] Figure 4 is a schematic diagram of the structure of a specific embodiment of the gas pipeline vibration measurement system provided by the present invention;

[0056] Figure 5 is a schematic diagram of the structure of the multi-stage optical splitting (combining) module provided by the present invention.

[0057] The reference numerals are as follows:

[0058] 100 - single-mode fiber section, 200 - hollow-core fiber section, 300 - inner-coated capillary glass tube

[0059] 1 - transmitting end, 11 - white light source, 12 - multi-stage optical splitter module, 13 - fiber optic circulator array

[0060] 2 - receiving end, 21 - multi-stage optical combiner module, 22 - tunable optical filter, 23 - photodetector, 24 - low-noise amplifier circuit, 25 - low-pass filter circuit, 26 - signal processing module

[0061] 261 - AD data acquisition module, 262 - positioning algorithm module, 263 - multi-dimensional vibration data sorting module, 264 - pattern recognition and threshold processing module Specific Embodiment

[0062] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully communicated to those skilled in the art.

[0063] The vibration measurement system and method based on a novel fiber optic sensor provided by the present invention change the traditional fiber optic sensing mechanism, introduce a fiber optic sensor based on the anti-resonant principle, effectively solve the temperature interference problem of the entire sensing network, improve the performance of the fiber optic sensing network, and make vibration measurement more accurate; at the same time, the installation method, the sensing system network layout method and the structure of the sensing host system applied to the safety monitoring of gas pipelines increase the dimension of sensing information through various sensor installation methods, providing a data basis for the pattern recognition of gas pipeline vibration signals. Thus, the temperature interference problem of the gas pipeline vibration detection sensing network based on fiber optic sensors is solved. At the same time, this detection method increases the dimension of sensing information through various sensor installation methods, reduces the complexity of the equipment, and reduces the equipment cost.

[0064] In a specific embodiment, as Figure 1 shown, the fiber optic sensor provided by the present invention includes a single-mode fiber section 100, a hollow-core fiber section 200, and an inner-coated capillary glass tube 300; wherein, there are two sections of the single-mode fiber section 100, and the hollow-core fiber section 200 is arranged between the two sections of the single-mode fiber section 100 to form an anti-resonant optical waveguide structure; the inner-coated capillary glass tube 300 is sleeved on the outer periphery of the single-mode fiber section 100 and the hollow-core fiber section 200.

[0065] Preferably, the inner-coated capillary glass tube 300 is sleeved on one side of the single-mode fiber section 100 and a partial pipe section of the hollow-core fiber section 200 close to the single-mode fiber section 100 on this side. That is to say, the main body of this fiber optic sensor is composed of two sections of SMF (Single Mode Fiber) and one section of HCF fiber (Hollow Core Fiber) to form an SMF-HCF-SMF structure, thus forming an ARROW structure (Anti-Resonant Reflecting Optical Waveguide). Then, an inner-coated capillary glass tube is sleeved on the basis of this ARROW structure to sense the environmental displacement amount. The specific structure is shown in Figure 1 shown.

[0066] Figure 2The schematic diagram of the sensing mechanism for vibration detection of the fiber optic sensor used in the present invention is given. By utilizing the anti-resonance working mechanism of this fiber optic sensor, the micro-radial displacement of the outer capillary glass tube can be reflected in the light intensity at the resonance point of the transmission spectrum. The dynamic displacement change is vibration, so the environmental vibration can be detected using the light intensity change. The specific sensing principle can be described as follows: This structure of capillary glass tube coated with HCF can be described as a FP (Fabry–Perot) etalon in the cross-sectional direction of the optical fiber, that is, the ARROW structure. Since the refractive index of the core in HCF is less than that of the cladding, the core mode oscillates and reflects within the core, and at the same time, part of the energy enters the cladding of HCF and is reflected and transmitted in the cladding, forming a cladding mode. The cladding mode is reflected at both outer interfaces (the interface without the covered capillary glass tube and the interface with the covered capillary glass tube). When the wavelength does not satisfy the resonance condition (anti-resonance wavelength), the transmitted light will be confined in the hollow core of HCF as the core mode; on the contrary, when the wavelength satisfies the resonance condition (anti-resonance wavelength), the transmitted light cannot be reflected by the FP resonator and will radiate out through the cladding of HCF. Therefore, a periodic and relatively narrow lossy dip corresponding to the resonance condition of ARROW will appear in the transmission spectrum. The resonance wavelength λd can be expressed as:

[0067]

[0068] In formula (1), n0 and n1 are the refractive indices of air and the HCF cladding respectively, and H is the resonance order. The transmission power T at the anti-resonance wavelength resonant can be expressed as:

[0069]

[0070] In formula (2), r is the reflection coefficient (a constant) between the air core and the cladding in HCF, r’ is the reflection coefficient between the HCF cladding and the capillary glass tube, and I r m esonant is the input light intensity at the resonance wavelength. It can be seen from Figure 2 that the right part of HCF in this sensor is covered by the capillary glass tube, while the other part is not covered by the capillary glass tube. Therefore, r’ will be a variable, and its value depends on the position of the capillary tube. In the HCF cladding not covered by the capillary tube, the reflection coefficient between the cladding and air is low (its value is about 0.04 according to the theory of Fresnel reflection); in the HCF cladding covered by the capillary tube, the reflection coefficient between the cladding and the silver film on the inner wall of the capillary glass is high (its value can be approximated as 1).

[0071] Therefore, when a small part of the HCF is covered by the capillary glass tube, most of the transmitted light at the resonance point will leak through the HCF cladding; conversely, if most of the HCF is covered by the capillary tube, due to the high reflectivity of the silver film, most of the light will be reflected on the silver film and confined to propagate within the waveguide. Therefore, if the capillary glass tube moves alone along the radial direction of the sensor, r’ will vary according to the covered length of the capillary tube, resulting in T resonant changing with the covered length, and dynamically showing radial vibration measurement.

[0072] With the ARROW structure fixed, the change of the sensor output spectrum when the outer capillary glass tube vibrates. At this anti-resonance wavelength, as the position of the capillary glass tube covering the HCF changes, the transmission power T resonant will change, and the anti-resonance wavelength basically remains unchanged. Combining with the sensing mechanism of the fiber optic sensor, it can be seen that this sensor is different from the traditional vibration sensor that utilizes the characteristics of fiber optic materials. The change of T resonant is not affected by the deformation and temperature of the optical fiber, and is only related to the relative position of the HCF and the capillary glass tube, significantly increasing the accuracy and stability of the vibration sensor. At the same time, this sensor only senses a single vibration direction (the radial direction of the sensor), making the sensing information more directional and providing more specific sensing information for the subsequent safety detection of gas pipelines.

[0073] In addition to the above fiber optic sensor, the present invention also provides a gas pipeline vibration measurement system based on this fiber optic sensor, as Figure 4 shown. The system includes a transmitting end 1 and a receiving end 2. Among them, the transmitting end 1 includes a white light source 11, a multi-stage optical beam splitter module 12 arranged downstream of the white light source 11, and an optical fiber circulator array 13 arranged downstream of the multi-stage optical beam splitter module 12; the receiving end 2 includes a multi-stage optical combiner module 21, a tunable optical filter 22, a photodetector 23, a low-noise amplifier circuit 24, a low-pass filter circuit 25, and a signal processing module 26 that are signal-connected to the optical fiber circulator array 13. According to Figure 3 the distribution schematic diagram of the provided sensor in the gas pipeline vibration monitoring sensing network, in order to achieve long-distance safety monitoring of gas pipelines, the present invention constructs a multi-point distributed gas pipeline vibration monitoring sensing network. Among them, the broadband light (C+L band) is evenly divided into N optical paths by the optical beam splitter from the left side of the figure, and enters the 1-port of the optical fiber circulator respectively, and then is input into the fiber optic sensors at each sensing point through the 2-port; after passing through the reflection-type filters connected behind the sensors (the wavelengths of each filter are different and the same as the anti-resonance wavelength of the sensor), the light carrying the sensing information is selectively reflected back to the optical fiber circulator and output from the 3-port, and enters the backend signal processing unit.

[0074] The sensor network host is the main structure of the gas pipeline vibration measurement system. As Figure 4 shown, this host mainly provides functions such as light source signal, signal demodulation, and early warning for the gas pipeline safety monitoring system. This sensor network host mainly consists of two parts, one is the transmitting end, and the other is the receiving end. The transmitting end includes a white light source, a j-level optical splitter module, and an optical fiber circulator array; the receiving end includes a j-level optical combiner module, a tunable optical filter, a photodetector, a low-noise amplifier circuit, a low-pass filter circuit, and a signal processing module. The signal processing module includes an AD data acquisition module, a positioning algorithm module, a multi-dimensional vibration data sorting module, and a pattern recognition and threshold processing module. The entire sensor network host in the present invention is composed of the above-mentioned functional modules.

[0075] Furthermore, the signal processing module includes an AD data acquisition module 261, a positioning algorithm module 262, a multi-dimensional vibration data sorting module 263, and a pattern recognition and threshold processing module 264. The multi-level optical splitter module includes: multi-level optical splitter components arranged in sequence; among them, the first-level optical splitter component includes 1 1×n optical splitter, and its incident port is connected to the light source end; the second-level optical splitter component includes n 1×n optical splitters, and the incident ports of each of the 1×n optical splitters are connected to the output ports of the 1×n optical splitters of the previous level; the third-level optical splitter component includes n 2 1×n optical splitters, and the incident ports of each of the 1×n optical splitters are connected to the output ports of the 1×n optical splitters of the previous level; and so on, the j-level optical splitter component includes n (j-1) 1×n optical splitters, and the incident ports of each of the 1×n optical splitters are connected to the output ports of the 1×n optical splitters of the previous level.

[0076] Similarly, the multi-level optical combiner module includes: multi-level optical combiner components arranged in sequence; among them, the first-level optical combiner component includes 1 1×n optical combiner, and its incident port is connected to the light source end; the second-level optical combiner component includes n 1×n optical combiners, and the incident ports of each of the 1×n optical combiners are connected to the output ports of the 1×n optical combiners of the previous level; the third-level optical combiner component includes n 2 1×n optical combiners, and the incident ports of each of the 1×n optical combiners are connected to the output ports of the 1×n optical combiners of the previous level; and so on, the j-level optical combiner component includes n (j-1) 1×n optical combiners, and the incident ports of each of the 1×n optical combiners are connected to the output ports of the 1×n optical combiners of the previous level.

[0077] That is to say, as Figure 5Schematic diagram of the multi-stage optical splitting (combining) beam module required for the given sensing host. This module is mainly composed of 1×n optical splitting (combining) beam splitters. Taking the jth stage as an example, the first stage consists of 1 1×n optical splitting (combining) beam splitter, and its port 1 is connected to the light source end; the second stage consists of n 1×n optical splitting (combining) beam splitters, and the port 1 of each optical splitting (combining) beam splitter is connected to the output end of the previous stage; the third stage consists of n 2 1×n optical splitting (combining) beam splitters, and the port 1 of each optical splitting (combining) beam splitter is connected to the output end of the previous stage; and so on, the jth stage consists of n (j-1) 1×n optical splitting (combining) beam splitters, and the port 1 of each optical splitting (combining) beam splitter is connected to the output end of the previous stage. Finally, there are n j optical splitting outputs, forming a multi-stage optical splitting (combining) beam splitter module. As Figure 5 shown, if light enters from the left and exits from the right, then this module is a multi-stage optical splitting module; if light enters from the right and exits from the left, then this module is a multi-stage optical combining module.

[0078] The present invention also provides a method for measuring the vibration of a gas pipeline. Based on the above-mentioned optical fiber sensor, the method includes the following steps:

[0079] S1: Prepare the optical fiber sensor and arrange multiple such optical fiber sensors on the gas pipeline in a preset manner. Specifically, according to the Figure 1 structure of the optical fiber sensor shown, a temperature-insensitive optical fiber vibration sensor is fabricated.

[0080] The specific manufacturing process and indicators are as follows: The HCF consists of a hollow with an inner diameter of d1 and an annular cladding with a thickness of d2. An HCF with a length of L1 is cut using a high-precision cutting knife, and the two ends of the SMF and the HCF are fused using a traditional optical fiber fusion splicer. Then, the fabricated ARROW structure is inserted into a capillary glass tube with a silver film plated on its inner diameter, and the thickness of the silver film is d5. This silver film plays a role in total reflection. This capillary glass tube consists of a hollow with an inner diameter of d3 and an annular glass cladding with a thickness of d4, and d3 is slightly larger than the outer diameter of the HCF ((d3-(d1 + 2d2)) < 7μm). Since the outer diameters of the SMF and the HCF and the hollow of the capillary glass tube are uniform, when the ARROW structure undergoes a radial displacement, it can smoothly pass through the capillary glass tube, forming an optical fiber sensor based on the ARROW structure.

[0081] Due to the directional constraint characteristics of vibration perception of this sensor, different installation directions on the pipeline will collect vibration information in different dimensions, providing a data basis for subsequent signal processing and pattern recognition. According to the requirements of collecting vibration information in different directions, the outer capillary glass tube in the sensor is glued at the corresponding pipeline position. At the same time, the ARROW optical fiber structure is tightened with a fixed stress along the sensor layout direction and fixed on the external wiring bracket of the pipeline to avoid the influence of the vibration of the gas pipeline on the position of the ARROW structure. According to the sensing mechanism, the pipeline vibration information is reflected in the radial displacement of the capillary glass tube. Therefore, the number of sensors arranged at a single point on the pipeline determines the dimension of the sensing information collected at that point. Assuming the length of the gas pipeline is L and the monitoring spatial resolution is the length q, then (L / q + 1) sensing points are required. Let each sensing point require k-dimensional sensing information, then the number of fiber optic sensors required is N (N = k * (L / q + 1)). According to Formula 1, by precisely controlling the length of the HCF, an ARROW structure with different anti-resonant wavelengths can be obtained. Sensors with different anti-resonant wavelengths are distributed at different positions on the gas pipeline, forming positioning information under wavelength discrimination.

[0082] S2: Connect a reflective filter to the end of each fiber optic sensor respectively, and the center wavelength of each reflective filter corresponds one-to-one with the anti-resonant wavelength of each fiber optic sensor, forming a sensing network. This filter plays the role of wavelength selection and light reflection, and can usually be realized by using FBG. Since the reflection wavelengths of the sensors at each sensing node are different, make a mapping mark of the position and wavelength. In this way, the optical power at the anti-resonant wavelength will reflect the pipeline vibration information and position information at that point.

[0083] S3: Connect each sensing node on the sensing network to the gas pipeline vibration measurement system through a single-mode fiber, and complete the wiring connection of the transmitting end and the receiving end; specifically, the transmitting end injects stable light in the C+L band into the multi-stage optical beam splitting module through a white light source, and evenly divides the light into n j parts; access the input port of the fiber optic sensor, and connect it out from the output port of the fiber optic sensor, and access it in sequence with the fiber optic bundle introduced by the gas pipeline.

[0084] That is to say, after the sensing network is arranged, connect each sensing node to the sensing network host in the present invention through a single-mode fiber. The transmitting end injects stable light in the C+L band into the multi-stage optical beam splitting module through a white light source, and evenly divides the light into n j parts; then access port 1 of the fiber optic circulator, come out from port 2, and access it in a certain order with the fiber optic bundle introduced by the gas pipeline. In this way, the wiring connection of the receiving end host is completed.

[0085] S4: The vibration information collected from the sensing network is accessed through the ports of the fiber optic sensors to the receiving end of the gas pipeline vibration measurement system. Specifically, it is accessed to a multi-stage optical combiner module, and n j sensing signals are combined into one optical signal and then accessed to a tunable optical filter. The anti-resonant wavelengths of multiple said fiber optic sensors are expanded on the time axis, and in a time-division multiplexing manner, combined with the control signal given by the positioning algorithm module, the signals of different anti-resonant wavelengths are filtered out time-divisionally. It is accessed to an optoelectronic conversion module to convert the optical signal into a processable electrical signal. After passing through a low-noise amplification and low-noise filtering module in sequence, an optimized sensing analog signal is obtained, and this sensing analog signal reflects the optical intensity value A reflected back by sensor i at a certain point of the pipeline at time T1 i_T1 ; This sensing analog signal is accessed to an AD data acquisition module for data acquisition, and the analog signal A i_T1 is converted into a digital signal D i_T1 , and then accessed to the positioning algorithm module to record the position information Address_i, forming an information array [D i_T1 , Address_i], and this information array contains the vibration information and position information at time T1. The central wavelength of the tunable optical filter is changed in sequence, the vibration information of each point of the pipeline in the sensing network is collected once, and then the sensing information at different times is collected in a loop according to this method. The system time resolution is set as Δt, indicating that each sensor collects sensing information at intervals of Δt, and the sensing information array [D i_T1 , D i_(T1+Δt) , …, D i_(T1+p*Δt) , Address_i] of each sensor in a time period can be obtained, and the p value is a parameter value determined based on signal processing requirements.

[0086] S5: The sensing information array of a single sensor obtained is accessed to a multi-dimensional vibration data processing module. According to the system pattern recognition requirements, the number of dimensions q of a single measurement point is determined, and the sensing information matrix of each point is calculated on this processing module where q ≥ 1;

[0087] S6: Spectrum analysis is performed on each fiber optic sensor according to the information matrix, and a pipeline safety situation level warning is obtained based on the spectrum analysis result. Specifically, the information matrix is passed into the pattern recognition and threshold module, and spectrum analysis is performed on each sensor through the sensing information matrix; corresponding pattern recognition analysis is combined with the multi-dimensional information of a single point to exclude the pipeline vibration data caused by non-pipeline leakage; a pipeline safety situation level warning is given to the valid data in combination with the dynamic threshold.

[0088] In this way, the fiber optic sensor, the vibration measurement system and method based on the fiber optic sensor provided by the present invention have the characteristics of strong anti-interference ability, low false alarm rate, high measurement accuracy and low design cost; specifically, it has the following technical effects:

[0089] 1) The present invention introduces a novel fiber optic sensor into the gas pipeline vibration measurement system. Since the sensor has an anti-resonant waveguide structure and uses the sensing mechanism of relative physical displacement between optical fibers for vibration measurement, the sensing system is insensitive to temperature, greatly improving the anti-interference ability of the system.

[0090] 2) Since the fiber optic sensor is only sensitive to vibration signals with direction constraints, different vibration signals in different component directions can be obtained according to different installation methods, providing multi-dimensional reference information for system pattern recognition, providing more data support for further improving the system's safety warning ability, and reducing the false alarm rate of the system.

[0091] 3) Since the present system uses wavelength to locate the pipeline position and uses the time-division multiplexing method to collect sensor information at different times, it greatly saves the number of light sources and optoelectronic converters, reduces the system complexity, and makes the system simple to implement and low in cost.

[0092] A novel temperature-insensitive fiber optic sensing structure is introduced into the gas safety monitoring system based on fiber optic sensing technology. By using the anti-resonant waveguide structure, the traditional fiber optic sensing method that uses the elasto-optic effect and thermo-optic effect of materials for information perception is changed. The relative physical displacement between optical fibers is used for vibration sensing, greatly improving the anti-interference ability of the system. At the same time, according to different installation and wiring methods of the sensor, single-point different-dimensional vibration information is introduced, providing multi-dimensional data for subsequent signal processing and making pattern recognition more accurate. The reflective filter connected after each sensing point makes each fiber optic sensor adopt a probe-type wiring method, enabling the construction of the sensing system with only one optical fiber between the fiber optic sensor and the host, greatly simplifying the complexity of sensor installation and wiring. The sensing system uses wavelength to locate the pipeline position and integrates the sensing information of each position point by using time-division multiplexing technology, enabling the system to be realized with a single light source and optoelectronic converter, greatly reducing the system complexity and cost.

[0093] It should be understood that the terms used herein are for the purpose of describing particular example embodiments only and are not intended to be limiting. Unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" as used herein may also include the plural forms. The terms "comprising", "including", "containing", and "having" are inclusive and thus specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order described or illustrated, unless specifically indicated as an order of performance. It should also be understood that additional or alternative steps may be used.

[0094] Although the terms first, second, third, etc. may be used herein to describe multiple elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or section from another. Unless the context clearly indicates otherwise, terms such as "first", "second", and other numerical terms when used herein do not imply an order or sequence. Thus, the first element, component, region, layer, or section discussed below may be referred to as the second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0095] For ease of description, spatial relative relationship terms may be used herein to describe the relationship of one element or feature shown in the figures to another element or feature, such as "inside", "outside", "inner side", "outer side", "below", "beneath", "above", "over", etc. Such spatial relative relationship terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is flipped, an element described as "below" or "beneath" other elements or features will then be oriented "above" or "over" the other elements or features. Thus, the example term "below" can include both an orientation above and below. The device may be otherwise oriented (rotated 90 degrees or in other directions) and the spatial relative relationship descriptors used herein are to be interpreted accordingly.

[0096] As described above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A gas pipeline vibration measurement system based on an optical fiber sensor, characterized in that, The optical fiber sensor includes: Single-mode optical fiber segments, and there are two single-mode optical fiber segments; A medium hollow optical fiber segment, which is arranged between the two single-mode optical fiber segments and forms an anti-resonant optical waveguide structure; An inner-coated capillary glass tube, which is sleeved on the outer peripheries of the single-mode optical fiber segments and the medium hollow optical fiber segment; The system includes: A transmitting end, which includes a white light source, a multi-stage optical beam splitter module arranged downstream of the white light source, and an optical fiber circulator array arranged downstream of the multi-stage optical beam splitter module; A receiving end, which includes a multi-stage optical combiner module, a tunable optical filter, a photodetector, a low-noise amplification circuit, a low-pass filtering circuit, and a signal processing module that are signal-connected to the optical fiber circulator array; and The ends of the optical fiber sensors are respectively connected to reflection filters, and the central wavelengths of the reflection filters correspond to the anti-resonant wavelengths of the optical fiber sensors, forming a sensing network. Each sensing node on the sensing network is connected to the gas pipeline vibration measurement system through a single-mode optical fiber, and the wiring connections between the transmitting end and the receiving end are completed. The vibration information collected from the sensing network is accessed to the receiving end of the gas pipeline vibration measurement system through the ports of the optical fiber sensors.

2. The gas pipeline vibration measurement system according to claim 1, wherein The signal processing module includes: An AD data acquisition module, a positioning algorithm module, a multi-dimensional vibration data sorting module, and a pattern recognition and threshold processing module.

3. The gas pipeline vibration measurement system according to claim 2, characterized in that The multi-stage optical beam splitter module includes: multi-stage optical beam splitter components arranged in sequence; Among them, The first-stage optical beam splitter component includes one 1×n optical beam splitter, and its incident port is connected to the light source end; The second-stage optical beam splitter component includes n 1×n optical beam splitters, and the incident ports of the 1×n optical beam splitters in the second-stage optical beam splitter component are connected to the output ports of the 1×n optical beam splitters in the first-stage optical beam splitter component of the previous stage; The third-level optical beam splitter assembly includes n 2 1×n optical beam splitters, and the input ports of the 1×n optical beam splitters in the third-level optical beam splitter assembly are connected to the output ports of the 1×n optical beam splitters in the second-level optical beam splitter assembly of the previous level; By analogy, the j-th level optical beam splitter component includes n (j-1) 1×n optical beam splitters, and the input ports of the 1×n optical beam splitters in the j-th level optical beam splitter component are connected to the output ports of the 1×n optical beam splitters in the previous level.

4. The gas pipeline vibration measurement system according to claim 3, characterized in that, The multi-stage optical combiner module includes: multi-stage optical combiner components arranged in sequence; Among them, The first-stage optical combiner component includes one 1×n optical combiner, and its incident port is connected to the light source end; The second-stage optical combiner component includes n 1×n optical combiners, and the incident ports of the 1×n optical combiners in the second-stage optical combiner component are connected to the output ports of the 1×n optical combiners in the first-stage optical combiner component of the previous stage; The third - level optical combiner assembly includes n 2 1×n optical combiners, and the input ports of the 1×n optical combiners in the third - level optical combiner assembly are connected to the output ports of the 1×n optical combiners in the second - level optical combiner assembly of the previous level; By analogy, the j-th level photosynthetic beam combiner assembly includes n (j-1) 1×n photosynthetic beam combiners, and the incident ports of the 1×n photosynthetic beam combiners in the j-th level photosynthetic beam combiner assembly are connected to the output ports of the 1×n photosynthetic beam combiners in the previous level.

5. A method for measuring the vibration of a gas pipeline, which is used to implement the gas pipeline vibration measurement system according to any one of claims 3-4, characterized in that, The method includes: S1: Prepare the optical fiber sensors, and arrange multiple optical fiber sensors on the gas pipeline in a preset manner; S2: Connect reflection filters to the ends of each optical fiber sensor respectively, and the central wavelengths of the reflection filters correspond one-to-one to the anti-resonant wavelengths of the optical fiber sensors, forming a sensing network; S3: Connect each sensing node on the sensing network to the gas pipeline vibration measurement system through a single-mode optical fiber, and complete the wiring connections between the transmitting end and the receiving end; S4: The vibration information collected from the sensing network is accessed through the ports of the fiber optic sensors to the receiving end of the gas pipeline vibration measurement system; among them, the sensing analog signal of the fiber optic sensor is accessed to the AD data acquisition module for data acquisition, and the analog signal A i_T1 is converted into a digital signal D i_T1 , and then accessed to the positioning algorithm module to record the position information Address_i, forming an information array [D i_T1 , Address_i], which contains the vibration information and position information at time T1; the central wavelength of the tunable optical filter is changed in sequence, and the vibration information of each point on the pipeline in the sensing network is collected once, and then the sensing information at different times is collected in this way in a loop; the system time resolution is set to Δt, indicating that each sensor collects sensing information at intervals of Δt, and the sensing information array of each sensor in a period can be obtained [D i_T1 , D i_(T1+Δt) , …, D i_(T1+p*Δt) , Address_i], and the p value is a parameter value determined based on signal processing requirements; S5: Connect the obtained sensing information array of a single sensor to the multi-dimensional vibration data processing module. According to the system pattern recognition requirements, determine the number of dimensions q of a single measurement point, and calculate the sensing information matrix of this point i on this processing module. Among them, q ≥ 1; S6: Perform spectral analysis on each fiber optic sensor according to the information matrix, and obtain the pipeline safety situation level warning based on the spectral analysis results.

6. The gas pipeline vibration measurement method according to claim 5, characterized in that, In step S3, connecting each sensing node on the sensing network to the gas pipeline vibration measurement system through a single-mode optical fiber and completing the wiring connections between the transmitting end and the receiving end specifically includes: The transmitting end injects stable C+L band light into a multi-stage optical beam splitting module through a white light source, and evenly divides the light into n j portions; Connect to the input port of the fiber optic sensor, lead out from the output port of the fiber optic sensor, and connect to the fiber optic bundle introduced by the gas pipeline in sequence.

7. The gas pipeline vibration measurement method according to claim 5, characterized in that, In step S4, the vibration information collected from the sensing network is connected to the receiving end of the gas pipeline vibration measurement system through the port of the fiber optic sensor, and further includes: Access the multi-stage photosynthetic beam module, and combine n j sensing signals into one optical signal and then access the tunable optical filter; Unfold the anti-resonant wavelengths of multiple said fiber optic sensors on the time axis, adopt a time-division multiplexing method, and combine the control signal given by the positioning algorithm module to filter out the signals of different anti-resonant wavelengths in a time-sharing manner; Connect to the optoelectronic conversion module to convert the optical signal into a processable electrical signal; After the low-noise amplification and low-noise filtering modules, the optimized sensor analog signal is obtained. The sensor analog signal reflects the light intensity value A reflected by the sensor at a certain point i in the pipeline at time T1. i_T1 .

8. The gas pipeline vibration measurement method according to claim 5, characterized in that, In step S6, perform spectral analysis on each fiber optic sensor according to the information matrix, and obtain the pipeline safety situation level warning based on the spectral analysis result, specifically including: Input the information matrix into the pattern recognition and threshold module to perform spectral analysis on each sensor through the sensing information matrix; Perform corresponding pattern recognition analysis by combining the multi-dimensional information of a single point to exclude the pipeline vibration data caused by non-pipeline leakage; Combine the dynamic threshold to give a pipeline safety situation level warning for the valid data.

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