CN111721394A - Gas pipeline vibration measurement system and method based on optical fiber sensor - Google Patents

Abstract

The invention discloses a gas pipeline vibration measurement system and method based on an optical fiber sensor, wherein the system comprises: the optical fiber circulator array comprises a transmitting end and a plurality of optical fiber circulator arrays, wherein the transmitting end comprises a white light source, a multi-stage optical splitter module arranged at the downstream of the white light source, and an optical fiber circulator array arranged at the downstream of the multi-stage optical splitter module; and the receiving end comprises a multi-stage optical beam combiner module, a tunable optical filter, a photoelectric detector, a low-noise amplifying circuit, a low-pass filtering circuit and a signal processing module, wherein the multi-stage optical beam combiner module is in signal connection with the optical fiber circulator array. The method solves the problem of temperature interference of the gas pipeline vibration detection sensor network based on the optical fiber sensor, and meanwhile, the detection method increases the dimension of sensing information, reduces the complexity of equipment and reduces the equipment cost through various sensor installation modes.

Description

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

Technical Field

The invention relates to the technical field of gas pipeline safety protection, in particular to a gas pipeline vibration measurement system and method based on an optical fiber sensor.

Background

This section provides background information related to the present disclosure only and is not necessarily prior art.

The gas pipeline is used as an important infrastructure for industrial production and civil use in cities and towns, and plays an important role in urban development and daily life of people. As bearing equipment for flammable and explosive dangerous gases such as natural gas, liquefied petroleum gas, coal gas and the like, once leakage occurs, huge social danger can be generated, and meanwhile, huge economic loss can be caused to a gas company. Therefore, the safe operation of the urban gas pipeline has great significance to social economy, production and living, and human welfare.

The causes of gas pipeline leakage are many, such as pipeline aging, corrosion, natural or artificial damage, etc. Therefore, the expression forms of the damaged part are various, and the detection methods are also various: sectional pressure method, magnetic flaw detection method, negative pressure method, vibration detection method, etc. However, the traditional manual maintenance is poor in real-time performance and relatively low in efficiency, and it is necessary to introduce an automation technology for safety monitoring in order to improve the stability of the system.

At present, in a method for detecting vibration of a gas pipeline based on an optical fiber sensor, most of the optical fiber sensors sense environmental vibration based on an elasto-optical effect or a backscattering principle of an optical fiber material. The sensor based on the mechanism works by mostly utilizing a fiber grating structure or an interference type fiber structure or a backscattering type distributed fiber sensing structure, and has sensing capability on pipeline vibration. But also can be influenced by factors such as thermal effect, optical fiber deformation and the like, and the problem of irrelevant quantity coupling interference such as temperature, static stress and the like is generated, so that a wrong identification result is easily obtained, a false alarm is generated, and the accuracy and the stability of the sensing system are greatly reduced. In addition, the existing detection method utilizes the elasto-optical effect of the optical fiber, the vibration direction generated by the pipeline cannot be identified, the sensing result is the comprehensive influence of vibration on the deformation of the optical fiber, only a single-dimensional sensing signal can be provided, and more-dimensional information cannot be provided for vibration mode identification. Meanwhile, part of the traditional pipeline vibration sensing methods are used for detecting the change of spectral wavelength, which also provides challenges for the complexity and cost of demodulation equipment; and a distributed optical fiber sensing system utilizing backscattering has higher requirements on the power of a light source, the energy of a reflected sensing signal is weaker, and the requirements on a denoising algorithm of demodulation equipment are also higher.

Disclosure of Invention

The invention aims to provide a gas pipeline vibration measuring system and method based on an optical fiber sensor, which at least partially solve the problems that the existing sensor is easy to be interfered by irrelevant factors such as temperature and the like and the accuracy rate of the safety monitoring of a gas pipeline is low; and the technical problems of single dimension of sensing signals and high system complexity. The purpose is realized by the following technical scheme:

the invention provides a gas pipeline vibration measurement system based on an optical fiber sensor, which comprises:

a single mode fiber section, the single mode fiber section being two sections;

the hollow core optical fiber section is arranged between the two single-mode optical fiber sections and forms an anti-resonance optical waveguide structure;

the inner film-coated capillary glass tube is sleeved on the peripheries of the single-mode optical fiber section and the hollow optical fiber section;

the system comprises:

the optical fiber circulator array comprises a transmitting end and a plurality of optical fiber circulator arrays, wherein the transmitting end comprises a white light source, a multi-stage optical splitter module arranged at the downstream of the white light source, and an optical fiber circulator array arranged at the downstream of the multi-stage optical splitter module;

and the receiving end comprises a multi-stage optical beam combiner module, a tunable optical filter, a photoelectric detector, a low-noise amplifying circuit, a low-pass filtering circuit and a signal processing module, wherein the multi-stage optical beam combiner module is in signal connection with the optical fiber circulator array.

Further, the signal processing module includes:

the device comprises an AD data acquisition module, a positioning algorithm module, a multi-dimensional vibration data sorting module and a mode identification and threshold processing module.

Further, the multi-stage optical splitter module includes: the multistage optical splitter components are arranged in sequence;

wherein the content of the first and second substances,

the first-stage optical beam splitter component comprises 1 × n optical beam splitter, and an incident port of the first-stage optical beam splitter component is connected with an optical source end;

the second-stage optical splitter component comprises n 1 × n optical splitters, and an incident port of each 1 × n optical splitter is connected with an output port of the 1 × n optical splitter at the upper stage;

the third stage optical splitter assembly includes n ²1 × n optical beam splitters, and the incident port of each 1 × n optical beam splitter is connected with the output port of the 1 × n optical beam splitter at the upper stage;

and so on, the j-th level optical beam splitter component comprises n ^(j-1)1 × n optical beam splitters, and the incident port of each 1 × n optical beam splitter is connected with the output port of the 1 × n optical beam splitter at the upper stage.

Further, the multi-stage optical combiner module includes: the multistage optical beam combiner components are arranged in sequence;

wherein the content of the first and second substances,

the first-stage optical beam combiner assembly comprises 1 × n optical beam combiner, and an incident port of the first-stage optical beam combiner is connected with an optical source end;

the second-stage optical beam combiner assembly comprises n 1 xn optical beam combiners, and an incident port of each 1 xn optical beam combiner is connected with an output port of the 1 xn optical beam combiner at the upper stage;

the third stage of optical beam combiner assembly comprises n ²1 × n optical beam combiners, and the incident port of each 1 × n optical beam combiner is connected with the output port of the 1 × n optical beam combiner at the upper stage;

by analogy, the j-th-stage optical beam combiner component comprises n^(j-1)And the incident port of each 1 × n optical beam combiner is connected with the output port of the 1 × n optical beam combiner at the upper stage.

The invention also provides a gas pipeline vibration measuring method based on the optical fiber sensor, which comprises the following steps:

s1: preparing the optical fiber sensors, and arranging the optical fiber sensors on a gas pipeline according to a preset mode;

s2: the tail end of each optical fiber sensor is respectively connected with a reflection type filter, the center wavelength of each reflection type filter corresponds to the anti-resonance wavelength of each optical fiber sensor one by one, and a sensing network is formed;

s3: connecting each sensing node on the sensing network into a gas pipeline vibration measurement system through a single-mode optical fiber, and completing wiring connection of a transmitting end and a receiving end;

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;

s5: the obtained sensing information array of a single sensor is accessed into a multi-dimensional vibration data processing module, the dimension number q of a single measuring point is determined according to the system mode identification requirement, and a sensing information matrix of each point is calculated on the processing module

Wherein q is more than or equal to 1;

s6: and carrying out spectrum analysis on each optical fiber sensor according to the information matrix, and acquiring pipeline safety condition grade early warning based on the spectrum analysis result.

Further, in step S3, 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 connection between the transmitting end and the receiving end is completed, which specifically includes:

the emitting end injects the C + L waveband stable light into the multistage light beam splitting module through the white light source to divide the light into n^jPreparing;

the optical fiber sensor is connected to the input port of the optical fiber sensor, is connected out from the output port of the optical fiber sensor, and is connected with an optical fiber bundle introduced by a gas pipeline in sequence.

Further, in step 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, and the method specifically includes:

connecting into a multi-stage light beam combining module to combine n^jThe sensing signals are combined into one path of optical signal and then are accessed into a tunable optical filter;

the anti-resonance wavelengths of the optical fiber sensors are expanded on a time axis, and signals with different anti-resonance wavelengths are filtered in a time-sharing mode by combining a control signal given by a positioning algorithm module;

the photoelectric conversion module is connected to convert the optical signal into a processable electrical signal;

sequentially passing through a low-noise amplification module and a low-noise filtering module to obtain an optimized sensing analog signal, wherein the sensing analog signal reflects T₁Light intensity value A reflected by sensor i at certain point of time pipeline_{i_T1}；

The sensing analog signal is accessed into an AD data acquisition module for data acquisition, and an analog signal A is accessed_{i_T1}Conversion into digital signal D_{i_T1}Then accessing a positioning algorithm module, recording the position information Address _ i, and forming an information array [ D ]_{i_T1},Address_i]The information array contains T₁Vibration information and position information at the moment;

sequentially changing the central wavelength of the tunable optical filter, collecting vibration information of each point of the pipeline in the sensing network, and circularly collecting the sensing information at different moments according to the method;

setting the time resolution of the system as delta t, representing that each sensor collects sensing information once at interval delta t, and obtaining a sensing information array [ D ] of each sensor in a time period_{i_T1},D_{i_(T1+Δt)},…,D_{i_(T1+p*Δt)},Address_i]The p-value is a parameter value determined based on signal processing requirements.

Further, in step S6, performing spectrum analysis on each optical fiber sensor according to the information matrix, and obtaining a pipeline safety condition level warning based on a spectrum analysis result, specifically including:

transmitting the information matrix into a pattern recognition and threshold module, and performing spectrum analysis on each sensor through the sensing information matrix;

performing corresponding pattern recognition analysis by combining single-point multi-dimensional information, and eliminating pipeline vibration data caused by non-pipeline leakage;

and carrying out pipeline safety condition grade early warning on the effective data by combining the dynamic threshold value.

According to the vibration measurement system and method based on the optical fiber sensor, the traditional optical fiber sensing mechanism is changed, the optical fiber sensor based on the anti-resonance principle is introduced, the temperature interference problem of the whole sensing network is effectively solved, the performance of the optical fiber sensing network is improved, and the vibration measurement is more accurate; meanwhile, the installation mode, the sensing system networking method and the sensing host system structure applied to the safety monitoring of the gas pipeline increase the dimension of sensing information through various installation modes of the sensor, and provide a data basis for mode identification of gas pipeline vibration signals. The method solves the problem of temperature interference of the gas pipeline vibration detection sensor network based on the optical fiber sensor, and meanwhile, the detection method increases the dimension of sensing information, reduces the complexity of equipment and reduces the equipment cost through various sensor installation modes.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like parts are designated by like reference numerals throughout the drawings. In the drawings:

FIG. 1 is a schematic structural diagram of an embodiment of an optical fiber sensor provided in the present invention;

FIG. 2 is a schematic diagram of a sensing mechanism of the optical fiber sensor shown in FIG. 1 during vibration detection;

FIG. 3 is a schematic distribution diagram of sensors provided by the present invention in a gas pipeline vibration monitoring sensor network;

FIG. 4 is a schematic structural diagram of an embodiment of a gas pipeline vibration measurement system provided by the present invention;

fig. 5 is a schematic structural diagram of the multi-stage light splitting (combining) module provided in the present invention.

The reference numbers are as follows:

100-single mode fiber section 200-hollow core fiber section 300-inner coated capillary glass tube

1-emitting end 11-white light source 12-multi-stage optical beam splitter module 13-optical fiber circulator array

2-receiving end 21-multistage optical beam combiner module 22-tunable optical filter 23-photoelectric detector 24-low noise amplifying circuit 25-low pass filter circuit 26-signal processing module

261-AD data acquisition module 262-positioning algorithm module 263-multidimensional vibration data sorting module 264-mode identification and threshold processing module

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

According to the vibration measurement system and method based on the novel optical fiber sensor, the traditional optical fiber sensing mechanism is changed, the optical fiber sensor based on the anti-resonance principle is introduced, the temperature interference problem of the whole sensing network is effectively solved, the performance of the optical fiber sensing network is improved, and the vibration measurement is more accurate; meanwhile, the installation mode, the sensing system networking method and the sensing host system structure applied to the safety monitoring of the gas pipeline increase the dimension of sensing information through various sensor installation modes, and provide a data basis for mode identification of gas pipeline vibration signals. The method solves the problem of temperature interference of the gas pipeline vibration detection sensor network based on the optical fiber sensor, and meanwhile, the detection method increases the dimension of sensing information, reduces the complexity of equipment and reduces the equipment cost through various sensor installation modes.

In one embodiment, as shown in fig. 1, the fiber sensor provided by the present invention comprises a single-mode fiber segment 100, a hollow fiber segment 200 and an inner coated capillary glass tube 300; the single-mode optical fiber section 100 is two sections, and the hollow core optical fiber section 200 is arranged between the two sections of the single-mode optical fiber section 100 and forms an anti-resonance optical waveguide structure; the inner coated capillary glass tube 300 is sleeved on the peripheries of the single-mode fiber section 100 and the hollow fiber section 200.

Preferably, the inner coated capillary glass tube 300 is sleeved on the single mode fiber section 100 at one side, and the hollow core fiber section 200 is close to a part of the single mode fiber section 100. That is, the Fiber sensor body is composed of two sections of SMF (Single Mode Fiber) and one section of HCF (Hollow Core Fiber) to form a SMF-HCF-SMF structure, thereby forming an ARROW structure (Anti-Resonant Reflecting optical waveguide). An inner film-coated capillary glass tube is sleeved outside the ARROW structure for sensing environmental displacement, and the specific structure is shown in figure 1.

Fig. 2 is a schematic diagram showing a sensing mechanism of vibration detection of the optical fiber sensor used in the present invention. By utilizing the anti-resonance working mechanism of the optical fiber sensor, the micro radial displacement of the outer sleeve capillary glass tube can be reflected on the light intensity of the resonance point of the transmission spectrum, and the dynamic displacement change is vibration, so that the environmental vibration is detected by using the light intensity change. The specific sensing principle can be described as follows: the structure of the capillary glass tube coated HCF can be described as FP (Fabry-Perot) etalon in the fiber cross section direction, i.e. ARROW structure. Because the refractive index of the fiber core in the HCF is smaller than that of the cladding, the fiber core mode oscillates and reflects in the fiber core, and meanwhile, part of energy enters the cladding of the HCF and is reflected and transmitted in the cladding to form a cladding mode. The cladding mode is reflected at both external interfaces (the interface without the coated capillary glass tube and the interface with the coated capillary glass tube). When the wavelength fails to satisfy the resonance condition (anti-resonance wavelength), the transmitted light will be confined in the hollow core of the HCF as a mandrel; in contrast, when the wavelength satisfies the resonance condition (antiresonance wavelength), the conducted light cannot be reflected by the FP resonator, and will be radiated outward through the cladding of the HCF. Periodic and narrow lossy dips corresponding to resonance conditions of ARROW may occur in the transmission spectrum. The resonance wavelength λ d can be expressed as:

in the formula (1), n₀、n₁The refractive indices of the air and HCF cladding, respectively, and H the resonance order. Transmission power T at antiresonance wavelength_resonantCan be expressed as:

in the formula (2), r is a reflection coefficient (constant) between the air core and the cladding in the HCF, r' is a reflection coefficient between the HCF cladding and the capillary glass tube, I_rm_esonantIs the input light intensity at the resonant wavelength. As can be seen from fig. 2, the right part of the HCF in this sensor is covered by the capillary glass tube, while the other part is not covered by the capillary glass tube. Thus, r' will be a variable whose value depends on the position of the capillary. In HCF cladding not covered by capillaries, the reflection coefficient between the cladding and air is low (about 0.04 according to fresnel reflection theory); in HCF cladding covered by capillary, the reflection coefficient between the cladding and the capillary glass optical wall silver film is high (which may be approximately 1).

Thus, when a small portion 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 a large portion of the HCF is covered by the capillary, most of the light will be reflected at the silver film and transported trapped within the waveguide due to the high reflectivity of the silver film. Therefore, if the capillary glass tube is moved in the sensor radial direction alone, r' will vary depending on the covered length of the capillary tube, resulting in T_resonantWill vary with the length of the cover and will behave dynamically as a radial vibration measurement.

Under the condition that the ARROW structure is fixed, the output spectrum of the sensor changes when the capillary glass tube of the outer sleeve vibrates. At the antiresonance wavelength, the transmission power T is changed along with the change of the HCF covering position of the capillary glass tube_resonantWill change and the anti-resonance wavelength will not change substantially. The sensing mechanism of the combined optical fiber sensor is known, and the sensor is different from the traditional vibration sensor which utilizes the characteristics of optical fiber materials, T_resonantVariations of (2)The vibration sensor is not influenced by optical fiber deformation and temperature, is only related to the relative positions of the HCF and the capillary glass tube, and obviously improves the accuracy and stability of the vibration sensor. Meanwhile, the sensor only senses a single vibration direction (the radial direction of the sensor), so that the sensing information has higher directivity, and more similar sensing information is provided for the subsequent safety detection of the gas pipeline.

In addition to the optical fiber sensor, the present invention further provides a gas pipeline vibration measurement system based on the optical fiber sensor, as shown in fig. 4, the system includes an emitting end 1 and a receiving end 2, wherein the emitting end 1 includes a white light source 11, a multi-stage optical splitter module 12 disposed downstream of the white light source 11, and an optical fiber circulator array 13 disposed downstream of the multi-stage optical splitter module 12; the receiving end 2 includes a multi-stage optical combiner module 21 in signal connection with the optical fiber circulator array 13, 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. According to the distribution schematic diagram of the sensors in the gas pipeline vibration monitoring and sensing network provided by fig. 3, in order to realize long-distance safety monitoring of the gas pipeline, the multipoint distributed gas pipeline vibration monitoring and sensing network is constructed. The wide-spectrum light (C + L wave band) is equally divided into N light paths from the left side of the figure through the optical beam splitter, respectively enters the port 1 of the optical fiber circulator, and then is input into the optical fiber sensors at the sensing points through the port 2; after passing through a reflection type filter connected behind the sensor (the wavelength of each filter is different and is the same as the anti-resonance wavelength of the sensor), the light with the sensing information is selectively reflected back to the optical fiber circulator and is output from the 3 ports to enter a back-end signal processing unit.

The main machine of the sensing network is the main structure of the gas pipeline vibration measuring system. As shown in fig. 4, the main machine mainly provides functions of light source signal and signal demodulation, early warning and the like for the gas pipeline safety monitoring system. The sensor network host mainly comprises two parts, namely a transmitting end and a receiving end. The transmitting end comprises a white light source, a j-level optical beam splitter module and an optical fiber circulator array; the receiving end comprises a j-level optical beam combiner module, a tunable optical filter, a photoelectric detector, a low-noise amplification circuit, a low-pass filter circuit and a signal processing module. The signal processing module comprises an AD data acquisition module, a positioning algorithm module, a multi-dimensional vibration data sorting module and a mode identification and threshold processing module. The sensing network host in the invention is composed of the above functional modules.

Furthermore, the signal processing module comprises an AD data acquisition module 261, a positioning algorithm module 262, a multi-dimensional vibration data sorting module 263 and a mode identification and threshold processing module 264, the multi-stage optical beam splitter module comprises multi-stage optical beam splitter assemblies which are sequentially arranged, wherein the first-stage optical beam splitter assembly comprises 1 × n optical beam splitter, an incident port of the first-stage optical beam splitter assembly is connected with an optical source end, the second-stage optical beam splitter assembly comprises n 1 × n optical beam splitters, an incident port of each 1 × n optical beam splitter is connected with an output port of the 1 × n optical beam splitter at the upper stage, and the third-stage optical beam splitter assembly comprises n optical beam splitter assemblies ²1 × n optical beam splitters, the incident port of each 1 × n optical beam splitter is connected with the output port of the 1 × n optical beam splitter at the upper stage, and so on, the j-th stage optical beam splitter component comprises n optical beam splitters ^(j-1)1 × n optical beam splitters, and the incident port of each 1 × n optical beam splitter is connected with the output port of the 1 × n optical beam splitter at the upper stage.

Similarly, the multi-stage optical combiner module comprises multi-stage optical combiner components which are sequentially arranged, wherein the first-stage optical combiner component comprises 1 × n optical combiners, incident ports of the first-stage optical combiners are connected with optical source ends, the second-stage optical combiner component comprises n 1 × n optical combiners, incident ports of the 1 × n optical combiners are connected with output ports of the 1 × n optical combiners at the upper stage, and the third-stage optical combiner component comprises n optical combiners ²1 × n optical beam combiners, and the incident port of each 1 × n optical beam combiner is connected with the output port of the 1 × n optical beam combiner at the upper stage, and so on, the j-th stage optical beam combiner component comprises n^(j-1)And the incident port of each 1 × n optical beam combiner is connected with the output port of the 1 × n optical beam combiner at the upper stage.

That is, as shown in fig. 5, the structure of the multi-stage beam splitting (combining) module required by the sensing host is schematically illustrated, the module mainly comprises 1 × n beam splitters, taking j stages as an example, the first stage comprises 1 × n beam splitters, 1 port is connected with the light source end, the second stage comprises n 1 × n beam splitters, each 1 port is connected with the output end of the first stage, and the third stage comprises n ²1 × n light beam splitters, each light beam splitter 1 port is connected with the output end of the upper stage, and so on, the j-th stage is composed of n ^(j-1)1 × n beam splitters, wherein each 1 port of the beam splitter is connected with the output end of the upper stage, and finally n^jThe light splitting output forms a multi-stage light splitting (combining) beam device module. As shown in fig. 5, light enters from the left side and exits from the right side, so that the module is a multi-stage light splitting module; the light enters from the right side and is output from the left side, and then the module is a multi-stage light combining module.

The invention also provides a gas pipeline vibration measuring method based on the optical fiber sensor, which comprises the following steps:

s1: and preparing the optical fiber sensors, and arranging the optical fiber sensors on a gas pipeline according to a preset mode. Specifically, according to the optical fiber sensor structure shown in fig. 1, a temperature insensitive optical fiber vibration sensor is manufactured.

The specific manufacturing process and indexes are as follows: the HCF consists of a core diameter d₁And a thickness d₂Is formed by the annular coating. Use the high-precision cutting knife to cut the length L₁And the SMF is fusion-spliced with both ends of the HCF by using a conventional optical fiber fusion splicer. Then inserting the manufactured ARROW structure into a capillary glass tube with the inner diameter plated with a silver film, wherein the thickness of the silver film is d₅. The silver film plays a role of total reflection. The capillary glass tube has an inner diameter d₃Is hollow and has a thickness d₄And d is a ring-shaped glass cladding layer of₃Slightly larger than the outer diameter of HCF ((d)₃-(d₁+2d₂))<7 μm). Because the SMF and HCF have uniform outer diameters and the hollow core of the capillary glass, the ARROW structure can smoothly pass through the capillary when radial displacement occursAnd the glass tube forms an optical fiber sensor based on an ARROW structure.

Because the sensor has the direction constraint characteristic of vibration perception, vibration information with different dimensionalities can be collected in different installation directions on the pipeline, and a data basis is provided for subsequent signal processing and pattern recognition. According to the requirements of vibration information in different directions needing to be collected, the outer sleeve capillary glass tube in the sensor is glued and fixed at the position of the corresponding pipeline. Meanwhile, the ARROW optical fiber structure is tensioned along the arrangement direction of the sensor by using fixed stress and is fixed on a pipeline external wiring support, so that the influence of the vibration of a gas pipeline on the position of the ARROW structure is avoided. According to a sensing mechanism, the vibration information of the pipeline is reflected on the radial displacement of the capillary glass tube, so that the number of sensors arranged at a certain single point of the pipeline determines the dimension of the sensing information acquired at the point. Assuming that the length of the gas pipeline is L and the monitoring spatial resolution is the length q, the (L/q +1) sensing points are needed. If k pieces of dimensional sensing information are required for each sensing point, the number of optical fiber sensors is N (N ═ k × (L/q + 1)). According to the formula 1, ARROW structures with different anti-resonance wavelengths can be obtained by accurately controlling the length of the HCF. The sensors with different anti-resonance wavelengths are distributed at different positions of the gas pipeline, so that positioning information under wavelength division is formed.

S2: the tail end of each optical fiber sensor is respectively connected with a reflection type filter, the center wavelength of each reflection type filter corresponds to the anti-resonance wavelength of each optical fiber sensor one by one, and a sensing network is formed. The filter plays roles of wavelength selection and light reflection, and can be realized by using the FBG generally, and because the reflection wavelength of each sensing node sensor is different, a mapping mark of a position and a wavelength is made, so that the light power at the anti-resonance wavelength reflects the vibration information and the position information of the pipeline at the point.

S3: connecting each sensing node on the sensing network into a gas pipeline vibration measurement system through a single-mode optical fiber, and completing wiring connection of a transmitting end and a receiving end; specifically, the emitting end injects C + L waveband stable light into the multi-stage light beam splitting module through the white light source to divide the light into n^jPreparing; accessing an input port of the fiber optic sensor and receiving signals fromAnd the output port of the optical fiber sensor is connected out and is sequentially connected with an optical fiber bundle introduced by a gas pipeline.

That is, after the sensor network is arranged, each sensor node is connected to the sensor network host in the invention by using the single mode fiber. The emitting end injects the C + L waveband stable light into the multistage light beam splitting module through the white light source to divide the light into n^jPreparing; then the optical fiber is connected into the port 1 of the optical fiber circulator, and is connected with the optical fiber bundle introduced by the gas pipeline in a certain sequence after being discharged from the port 2. Thus, the wiring connection of the receiving-end host is completed.

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; specifically, a multi-stage optical beam combining module is connected to combine n^jThe sensing signals are combined into one path of optical signal and then are accessed into a tunable optical filter; the anti-resonance wavelengths of the optical fiber sensors are expanded on a time axis, and signals with different anti-resonance wavelengths are filtered in a time-sharing mode by combining a control signal given by a positioning algorithm module; the photoelectric conversion module is connected to convert the optical signal into a processable electrical signal; sequentially passing through a low-noise amplification module and a low-noise filtering module to obtain an optimized sensing analog signal, wherein the sensing analog signal reflects T₁Light intensity value A reflected by sensor i at certain point of time pipeline_{i_T1}(ii) a The sensing analog signal is accessed into an AD data acquisition module for data acquisition, and an analog signal A is accessed_{i_T1}Conversion into digital signal D_{i_T1}Then accessing a positioning algorithm module, recording the position information Address _ i, and forming an information array [ D ]_{i_T1},Address_i]The information array contains T₁Vibration information and position information at the moment; sequentially changing the central wavelength of the tunable optical filter, collecting vibration information of each point of the pipeline in the sensing network, and circularly collecting the sensing information at different moments according to the method; setting the time resolution of the system as delta t, representing that each sensor collects sensing information once at interval delta t, and obtaining a sensing information array [ D ] of each sensor in a time period_{i_T1},D_{i_(T1+Δt)},…,D_{i_(T1+p*Δt)},Address_i]P value is based onThe number processing requirement determines the parameter value.

S5: the obtained sensing information array of a single sensor is accessed into a multi-dimensional vibration data processing module, the dimension number q of a single measuring point is determined according to the system mode identification requirement, and a sensing information matrix of each point is calculated on the processing module

Wherein q is more than or equal to 1;

s6: and carrying out spectrum analysis on each optical fiber sensor according to the information matrix, and acquiring pipeline safety condition grade early warning based on the spectrum analysis result. Specifically, an information matrix is transmitted into a pattern recognition and threshold module, and the frequency spectrum analysis is carried out on each sensor through a sensing information matrix; performing corresponding pattern recognition analysis by combining single-point multi-dimensional information, and eliminating pipeline vibration data caused by non-pipeline leakage; and carrying out pipeline safety condition grade early warning on the effective data by combining the dynamic threshold value.

Therefore, the optical fiber sensor, the vibration measurement system and the vibration measurement method based on the optical fiber sensor have the characteristics of strong anti-interference capability, low false alarm rate, high measurement precision and low design cost; specifically, it has the following technical effects:

1) the invention introduces a novel optical fiber sensor into a gas pipeline vibration measurement system. Because the sensor is of an anti-resonance waveguide structure, a sensing mechanism that relative physical displacement between optical fibers is used for vibration measurement is utilized, so that a sensing system is insensitive to temperature, and the anti-interference capability of the system is greatly improved.

2) Because the optical fiber sensor only has sensing capability on the vibration signals with direction constraint, the vibration signals with different component directions can be obtained according to different installation modes, multidimensional reference information is provided for system mode identification, more data support is provided for further improving the system safety early warning capability, and the system false alarm rate is reduced.

3) Because the system adopts the wavelength to position the pipeline and utilizes the time division multiplexing method to acquire the information of different sensors in a time-sharing way, the quantity of light sources and photoelectric converters is greatly saved, the complexity of the system is reduced, and the system is simple to realize and has low cost.

A novel temperature insensitive optical fiber sensing structure is introduced into a fuel gas safety monitoring system based on an optical fiber sensing technology. By using the anti-resonance waveguide structure, the mode that the traditional optical fiber sensing senses information by using the sensing mechanism of the elasto-optic effect and the thermo-optic effect of the material is changed. The relative physical displacement between the optical fibers is adopted for vibration sensing, so that the anti-interference capability of the system is greatly improved. Meanwhile, according to different installation and wiring modes of the sensor, single-point vibration information with different dimensions is introduced, multidimensional data are provided for subsequent signal processing, and mode identification is more accurate. The reflection-type filter is connected behind a single sensing point, so that each optical fiber sensor is changed into a probe type wiring mode, a sensing system is built only by one optical fiber between the optical fiber sensor and a host, and the complexity of sensor installation and wiring is greatly simplified. The sensing system utilizes the wavelength to position the pipeline position, utilizes the time division multiplexing technology to integrate the sensing information of each position point, so that the system can be realized by using a single light source and a photoelectric converter, and the complexity and the cost of the system are greatly reduced.

It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore 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 groups 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 identified as an order of performance. It should also be understood that additional or alternative steps may be used.

Although the terms first, second, third, etc. may be used herein to describe various 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 only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

For convenience of description, spatially relative terms, such as "inner", "outer", "lower", "below", "upper", "above", and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass 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 turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the example term "below … …" can include both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (8)

1. A gas pipeline vibration measurement system based on an optical fiber sensor is characterized in that the optical fiber sensor comprises:

a single mode fiber section, the single mode fiber section being two sections;

the hollow core optical fiber section is arranged between the two single-mode optical fiber sections and forms an anti-resonance optical waveguide structure;

the inner film-coated capillary glass tube is sleeved on the peripheries of the single-mode optical fiber section and the hollow optical fiber section;

the system comprises:

the optical fiber circulator array comprises a transmitting end and a plurality of optical fiber circulator arrays, wherein the transmitting end comprises a white light source, a multi-stage optical splitter module arranged at the downstream of the white light source, and an optical fiber circulator array arranged at the downstream of the multi-stage optical splitter module;

and the receiving end comprises a multi-stage optical beam combiner module, a tunable optical filter, a photoelectric detector, a low-noise amplifying circuit, a low-pass filtering circuit and a signal processing module, wherein the multi-stage optical beam combiner module is in signal connection with the optical fiber circulator array.

2. The gas pipeline vibration measurement system of claim 1, wherein the signal processing module comprises:

the device comprises an AD data acquisition module, a positioning algorithm module, a multi-dimensional vibration data sorting module and a mode identification and threshold processing module.

3. The gas duct vibration measurement system of claim 2, wherein the multi-stage optical splitter module comprises: the multistage optical splitter components are arranged in sequence;

wherein the content of the first and second substances,

the first-stage optical beam splitter component comprises 1 × n optical beam splitter, and an incident port of the first-stage optical beam splitter component is connected with an optical source end;

the second-stage optical splitter component comprises n 1 × n optical splitters, and an incident port of each 1 × n optical splitter is connected with an output port of the 1 × n optical splitter at the upper stage;

the third stage optical splitter assembly includes n²1 × n optical beam splitters, and the incident port of each 1 × n optical beam splitter is connected with the output port of the 1 × n optical beam splitter at the upper stage;

and so on, the j-th level optical beam splitter component comprises n^(j-1)1 × n optical beam splitters, and the incident port of each 1 × n optical beam splitter is connected with the output port of the 1 × n optical beam splitter at the upper stage.

4. The gas duct vibration measurement system of claim 3, wherein the multi-stage optical combiner module comprises: the multistage optical beam combiner components are arranged in sequence;

wherein the content of the first and second substances,

the first-stage optical beam combiner assembly comprises 1 × n optical beam combiner, and an incident port of the first-stage optical beam combiner is connected with an optical source end;

the second-stage optical beam combiner assembly comprises n 1 xn optical beam combiners, and an incident port of each 1 xn optical beam combiner is connected with an output port of the 1 xn optical beam combiner at the upper stage;

the third stage of optical beam combiner assembly comprises n²1 × n optical beam combiners, and the incident port of each 1 × n optical beam combiner is connected with the output port of the 1 × n optical beam combiner at the upper stage;

by analogy, the j-th-stage optical beam combiner component comprises n^(j-1)And the incident port of each 1 × n optical beam combiner is connected with the output port of the 1 × n optical beam combiner at the upper stage.

5. A gas conduit vibration measurement method for implementing a gas conduit vibration measurement system according to any one of claims 1 to 4, the method comprising:

s1: preparing the optical fiber sensors, and arranging the optical fiber sensors on a gas pipeline according to a preset mode;

s2: the tail end of each optical fiber sensor is respectively connected with a reflection type filter, the center wavelength of each reflection type filter corresponds to the anti-resonance wavelength of each optical fiber sensor one by one, and a sensing network is formed;

s3: connecting each sensing node on the sensing network into a gas pipeline vibration measurement system through a single-mode optical fiber, and completing wiring connection of a transmitting end and a receiving end;

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;

s5: the obtained sensing information array of a single sensor is accessed into a multi-dimensional vibration data processing module, the dimension number q of a single measuring point is determined according to the system mode identification requirement, and a sensing information matrix of the point i is calculated on the processing module

Wherein q is more than or equal to 1;

s6: and carrying out spectrum analysis on each optical fiber sensor according to the information matrix, and acquiring pipeline safety condition grade early warning based on the spectrum analysis result.

6. The gas pipeline vibration measurement method according to claim 5, wherein in step S3, 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 connection between the transmitting end and the receiving end is completed, specifically including:

the emitting end injects the C + L waveband stable light into the multistage light beam splitting module through the white light source to divide the light into n^jPreparing;

the optical fiber sensor is connected to the input port of the optical fiber sensor, is connected out from the output port of the optical fiber sensor, and is connected with an optical fiber bundle introduced by a gas pipeline in sequence.

7. The gas pipeline vibration measurement method according to claim 5, wherein in step S4, the vibration information collected from the sensing network is connected to a receiving end of the gas pipeline vibration measurement system through a port of the optical fiber sensor, and specifically includes:

connecting into a multi-stage light beam combining module to combine n^jThe sensing signals are combined into one path of optical signal and then are accessed into a tunable optical filter;

the anti-resonance wavelengths of the optical fiber sensors are expanded on a time axis, and signals with different anti-resonance wavelengths are filtered in a time-sharing mode by combining a control signal given by a positioning algorithm module;

the photoelectric conversion module is connected to convert the optical signal into a processable electrical signal;

sequentially passing through a low-noise amplification module and a low-noise filtering module to obtain an optimized sensing analog signal, wherein the sensing analog signal reflects T₁Light intensity value A reflected by sensor i at certain point of time pipeline_{i_T1}；

The sensing analog signal is accessed into an AD data acquisition module for data acquisition, and an analog signal A is accessed_{i_T1}Conversion into digital signal D_{i_T1}Then accessing a positioning algorithm module, recording the position information Address _ i, and forming an information array [ D ]_{i_T1},Address_i]The information array contains T₁Vibration information and position information at the moment;

sequentially changing the central wavelength of the tunable optical filter, collecting vibration information of each point of the pipeline in the sensing network, and circularly collecting the sensing information at different moments according to the method;

setting the time resolution of the system as delta t, representing that each sensor collects sensing information once at interval delta t, and obtaining a sensing information array [ D ] of each sensor in a time period_{i_T1},D_{i_(T1+Δt)},…,D_{i_(T1+p*Δt)},Address_i]The p-value is a parameter value determined based on signal processing requirements.

8. The gas pipeline vibration measurement method according to claim 5, wherein in step S6, performing spectrum analysis on each optical fiber sensor according to the information matrix, and obtaining pipeline safety condition level early warning based on the spectrum analysis result specifically comprises:

transmitting the information matrix into a pattern recognition and threshold module, and performing spectrum analysis on each sensor through the sensing information matrix;

performing corresponding pattern recognition analysis by combining single-point multi-dimensional information, and eliminating pipeline vibration data caused by non-pipeline leakage;

and carrying out pipeline safety condition grade early warning on the effective data by combining the dynamic threshold value.

Images