A multi-node distributed optical fiber hydrogen sensing detection system and method based on spectral-spatial double coding

Abstract

The application discloses a kind of multi-node distributed optical fiber hydrogen sensing detection system and method based on spectrum-space dual coding, belong to optical fiber gas sensing technical field.The system includes light source module, sensing optical fiber, multi-node hydrogen sensing module, optical signal demodulation module and data processing module, and multiple groups of sensing modules are coupled in the same sensing optical fiber by optical fiber multiplexing.The application configures unique spectrum code for each node by differentiating design optical resonance chip structure parameters, and constructs space code in combination with optical signal propagation delay, to form spectrum-space dual coding joint identification mechanism.The system relies on the change of optical parameters caused by hydrogen sensing of palladium-based composite resonance structure, and realizes node identification, leakage positioning and hydrogen concentration quantitative detection by fusing dual coding information.The application adopts all-optical passive detection, has the characteristics of intrinsic safety, explosion-proof and anti-electromagnetic interference, and has strong multi-node networking expansion, which is suitable for hydrogen online safety monitoring in hydrogen energy storage and transportation and industrial flammable and explosive scenes.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing and gas detection technology, specifically to a multi-node distributed fiber optic hydrogen sensing and detection system and method based on spectral-spatial dual coding.

[0002] This invention belongs to the interdisciplinary field of optical resonant fiber optic sensing and fiber optic multiplexing networking technology. Specifically, it involves deploying multiple hydrogen sensing nodes on a fiber optic sensing link and using a dual identification mechanism that combines unique spectral coding with optical temporal-spatial coding to achieve distributed online hydrogen monitoring technology that enables multi-node hydrogen concentration detection, node identification, and precise leak location on a single fiber optic link. Background Technology

[0003] Hydrogen, as a clean and efficient energy carrier, has wide applications in hydrogen fuel cells, hydrogen production, storage, transportation, and industrial manufacturing. However, hydrogen's small molecular weight, rapid diffusion, flammability, explosiveness, and low minimum ignition energy make it highly susceptible to leakage during production, storage, transportation, and use. When hydrogen mixes with air and reaches its explosive limit, it can easily ignite and explode upon contact with electrical sparks, static electricity, or high-temperature heat sources. Therefore, achieving rapid, accurate, and long-term online monitoring of hydrogen concentration for hydrogen energy applications is a core requirement for ensuring the safe operation of hydrogen energy equipment and mitigating the risks of leakage and explosion.

[0004] Currently, mainstream hydrogen detection technologies are mainly divided into three categories: electrochemical, semiconductor, and optical. Among them, electrochemical and semiconductor sensors rely on electrodes, heating elements, and active detection circuits to complete signal conversion, and the operation process involves heating and current transmission. In high-risk scenarios where hydrogen is flammable and explosive, these sensors must be equipped with explosion-proof housings and isolation devices, which not only increases system complexity and maintenance costs, but also has poor inherent safety, making them unsuitable for extremely dangerous, enclosed, and explosion-proof monitoring scenarios.

[0005] Fiber optic sensing technology uses optical signals as the transmission and detection carrier. The sensing area has no electrical connection and no risk of electric sparks. It has the advantages of inherent safety, resistance to electromagnetic interference, corrosion resistance, long-distance transmission, and adaptability to high-risk environments. It is the mainstream development direction for online monitoring of combustible gases, and is especially suitable for high-risk hydrogen energy scenarios such as petrochemical plants, hydrogen storage stations, and hydrogen transmission pipelines.

[0006] Existing fiber optic hydrogen sensing technologies mainly include fiber grating type, surface plasmon resonance type, interferometric type, and optical resonator type. Among them, fiber grating type and surface plasmon resonance type sensing technologies can be combined with hydrogen-sensitive materials to achieve hydrogen detection, and multi-point monitoring networks can be built through fiber multiplexing. However, existing commercial multi-point fiber optic hydrogen monitoring systems generally adopt a single spectral encoding method for node differentiation, relying solely on the center wavelength and spectral characteristic differences of the sensing unit to identify nodes.

[0007] In complex industrial settings such as large hydrogen storage tank areas, long-distance hydrogen pipelines, and hydrogen refueling stations, a large number of sensor nodes need to be deployed to achieve comprehensive monitoring. Existing single-spectral coding networking methods have significant technical shortcomings: as the number of nodes increases, spectral crosstalk and peak overlap problems easily arise. Furthermore, environmental interference such as temperature and mechanical stress further exacerbates node identification failures and reduces detection accuracy. In addition, traditional optical time-domain and optical frequency-domain distributed sensing technologies can only achieve spatial location positioning and cannot match the identity information of discrete optical resonant sensor nodes with hydrogen response characteristics, making it difficult to simultaneously complete node identification and accurate positioning.

[0008] In summary, existing fiber optic hydrogen sensing networking technologies suffer from drawbacks such as weak node differentiation capabilities, poor resistance to environmental interference, inability to simultaneously achieve identification and spatial positioning, and poor scalability for large-scale networking. There is an urgent need for a multi-node distributed fiber optic hydrogen sensing solution based on a dual-coding mechanism to overcome the current technological bottlenecks. Summary of the Invention

[0009] I. Purpose of the Invention

[0010] To address the shortcomings of existing fiber optic hydrogen sensing technologies, such as difficulties in node identification, easy spectral overlap, low leak location accuracy, weak network expansion capabilities, and poor explosion-proof and safety issues of traditional electrical sensors, this invention provides a multi-node distributed fiber optic hydrogen sensing detection system and method based on spectral-spatial dual coding.

[0011] This invention innovatively constructs a dual identification mechanism combining spectral coding and spatial location coding. Multiple independent hydrogen sensing nodes are reused on a single optical fiber link, with all nodes sharing the same light source and demodulation module. Node identities are distinguished by unique spectral characteristics, and their spatial locations are determined by optical temporal delay characteristics. The fusion of dual-coding information enables high-precision node identification, leak location, and quantitative detection of hydrogen concentration. Simultaneously, the all-optical-path passive sensing structure possesses inherent safety characteristics, making it suitable for various flammable and explosive hydrogen energy monitoring scenarios.

[0012] II. Technical Solution

[0013] To achieve the above objectives, the present invention adopts the following technical solution: a multi-node distributed optical fiber hydrogen sensing and detection system based on spectral-spatial dual coding, comprising a light source module, a sensing optical fiber, a multi-node hydrogen sensing module, an optical signal demodulation module, and a data processing module.

[0014] The light source module is configured to output a stable detection optical signal and couple the detection optical signal into the sensing optical fiber; the sensing optical fiber is at least one optical fiber, and multiple hydrogen sensing modules are arranged at intervals along the axial direction of the sensing optical fiber and coupled to the sensing optical fiber through an optical fiber multiplexing optical path, so that multiple detection nodes can share the same optical transmission link.

[0015] The hydrogen sensing module includes a gas diffusion structure, an optical resonant sensing chip, and an optical fiber coupling structure. The gas diffusion structure covers the outside of the optical resonant sensing chip and is used to guide the diffusion of ambient hydrogen molecules to the sensing area of ​​the chip. The optical resonant sensing chip consists of a dielectric substrate and a palladium metal micro-nano structure array disposed on the surface of the substrate. The two together constitute a metal-dielectric composite optical resonant sensing structure.

[0016] Multiple hydrogen sensing modules employ spectral encoding for unique identification. By adjusting the structural parameters of each optical resonant sensing chip, different sensing nodes can be equipped with distinct initial resonant center wavelengths. These adjustable structural parameters include at least one of the following: palladium metal micro / nano structure unit size, array period, metal layer thickness, and dielectric substrate material parameters. This ensures the unique spectral characteristics of each node and enables crosstalk-free node differentiation.

[0017] Multiple hydrogen sensing modules are fixed on the sensing optical fiber at a preset axial spacing to form a spatial position code; the data processing module can calculate the axial distance of each sensing node relative to the input end of the optical fiber based on the round-trip propagation time of the returned optical signal, the speed of light, and the effective refractive index of the sensing optical fiber, so as to accurately locate the hydrogen leakage area.

[0018] Multiple hydrogen sensing modules can be coupled to sensing fibers using a series, main fiber branch parallel, or bypass coupling optical multiplexing optical path. In the series structure, each sensing module is connected in series to the same optical fiber link. In the bypass coupling structure, each sensing module is connected to the main fiber through an optical fiber coupler. All sensing modules share the same light source module and optical signal demodulation module.

[0019] The optical signal demodulation module integrates an optical circulator, a spectral analysis unit, and a photoelectric conversion unit sequentially along the optical path; the optical circulator isolates the incident detection optical path from the return signal optical path, and the spectral analysis unit is used to extract the resonant peak wavelength characteristic parameters in the return optical signal.

[0020] The data processing module has a built-in storage unit that pre-stores the spectral coding identity information, initial resonant wavelength, axial installation position, and hydrogen concentration calibration parameters of each sensing node. During the detection process, the data processing module obtains the wavelength offset by the difference between the real-time resonant wavelength and the initial resonant wavelength, and calculates the real-time hydrogen concentration by combining it with the pre-calibrated hydrogen concentration-wavelength offset correspondence. At the same time, it integrates spectral coding and spatial coding information to accurately match the identity of the response node with the spatial location of the leak.

[0021] This invention also discloses a multi-node distributed optical fiber hydrogen sensing and detection method based on spectral-spatial dual coding, comprising the following steps:

[0022] S0. Pre-calibrate the initial resonant wavelength of each hydrogen sensing module, establish a corresponding model between hydrogen concentration and resonant wavelength offset, and input the initial resonant wavelength and fiber optic axial installation position information of each sensing node into the storage unit to construct a node data mapping database.

[0023] S1. The light source module transmits a detection light signal to the sensing optical fiber that is equipped with multiple hydrogen sensing modules. The detection light is transmitted along the optical fiber and acts on each hydrogen sensing module.

[0024] S2. When hydrogen is present in the environment, the resonant parameters of the optical resonant sensing chip of the hydrogen sensing module change, generating a return light signal carrying the spectral characteristics of the node.

[0025] S3. The optical signal demodulation module collects all returned optical signals and extracts the real-time resonant wavelength parameters corresponding to each signal.

[0026] S4. Retrieve the pre-stored initial resonant wavelength data of the nodes and identify the target sensing nodes that have responded through spectral coding matching;

[0027] S5. Calculate the axial spatial position of the target sensing node on the sensing fiber based on the round-trip propagation time of the returned optical signal.

[0028] S6. By fusing spectral coding identity information and spatial location information, the hydrogen leak point is accurately located. The hydrogen concentration at the corresponding location is calculated by combining the pre-calibrated model and wavelength offset, and the detection results are output.

[0029] III. Beneficial Effects

[0030] Compared with the prior art, the present invention has the following significant advantages:

[0031] (1) The present invention adopts a single fiber link multi-node multiplexing networking structure, with multiple detection nodes sharing a set of light source and demodulation equipment, which greatly simplifies the wiring structure of the monitoring system, improves the system integration, and reduces the equipment and maintenance costs of large-scale networking.

[0032] (2) The present invention adopts a unique spectral coding mechanism. Through differentiated micro-nano structure design, each sensing node has independent spectral characteristics, which completely solves the problems of spectral overlap and node identification confusion in traditional single spectral coding network and improves the identification accuracy of multi-node network.

[0033] (3) The present invention introduces an optical temporal spatial coding mechanism, which relies on the propagation delay of optical signals to achieve precise positioning of the axial position of the sensing node, thereby achieving precise locking of the hydrogen leakage area and making up for the shortcomings of traditional spectral detection in spatial positioning.

[0034] 4) This invention adopts a spectral-spatial dual-coding joint identification mechanism and dual-verification to locate sensor nodes. Compared with a single detection mechanism, it greatly improves the anti-interference capability, identification reliability and positioning accuracy of multi-node sensor networks in complex industrial environments.

[0035] 5) The entire sensing link of this invention adopts a passive optical structure. There are no electrical components, no heat generation when powered on, and no risk of electric sparks in the sensing area. It has the characteristics of intrinsic safety, resistance to electromagnetic interference, and corrosion resistance, and is fully suitable for high-risk monitoring scenarios of flammable and explosive hydrogen energy.

[0036] 6) This invention has strong network scalability. It can quickly adapt to different application needs such as small-scale single-point monitoring and large-scale full-domain network monitoring by increasing or decreasing the number of sensor nodes and adjusting the node deployment spacing. It has extremely strong versatility and adaptability. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the overall structure of a multi-node distributed optical fiber hydrogen sensing and detection system based on spectral-spatial dual coding according to the present invention.

[0038] Figure 2 This is a schematic diagram of the layout structure of multiple hydrogen sensing nodes distributed along the optical fiber axis according to the present invention.

[0039] Figure 3 This is a schematic diagram of the overall assembly structure of the hydrogen sensing module of the present invention;

[0040] Figure 4 This is a schematic diagram illustrating the principle of spectral-spatial dual-coding node identification and positioning in this invention;

[0041] Figure 5 This is a schematic diagram of the hydrogen sensing and detection method based on spectral-spatial dual encoding of the present invention. Detailed Implementation

[0042] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Equivalent substitutions, improvements and optimizations made by those skilled in the art without departing from the core technical concept of the present invention are all within the protection scope of the present invention.

[0043] Example 1: A multi-node distributed optical fiber hydrogen sensing and detection system based on spectral-spatial dual coding

[0044] like Figure 1 As shown, this embodiment provides a multi-node distributed optical fiber hydrogen sensing and detection system based on spectral-spatial dual coding, including a light source module 1, a sensing optical fiber 2, multiple hydrogen sensing modules 3, an optical signal demodulation module 4, and a data processing module 5.

[0045] The light source module 1 is used to generate a detection light signal and input the detection light signal into the sensing optical fiber 2.

[0046] The sensing fiber 2 is a single fiber structure, and multiple hydrogen sensing modules 3 are distributed along the length of the sensing fiber 2 and connected to the same sensing fiber 2 through a fiber multiplexing structure, so that hydrogen detection nodes in multiple spatial locations share the same optical signal transmission link.

[0047] like Figure 2 As shown, the multiple hydrogen sensing modules include a first hydrogen sensing module 31, a second hydrogen sensing module 32, a third hydrogen sensing module 33, and so on, up to an nth hydrogen sensing module 3n. Each hydrogen sensing module is positioned at a different location on the sensing fiber 2 and corresponds to a different spatial coordinate.

[0048] , , , ,

[0049] The optical signal demodulation module 4 is used to receive the optical response signals returned by each hydrogen sensing module 3, and extract the spectral change information and propagation time information contained therein.

[0050] The data processing module 5 is used to analyze and process the data output by the optical signal demodulation module 4. By establishing the correspondence between the spectral characteristics of the sensing node and its spatial location, it can realize the identification of hydrogen sensing nodes, the location of leaks, and the calculation of hydrogen concentration.

[0051] In this embodiment, multiple hydrogen sensing modules 3 are excited and detected only by optical signals. The detection area does not need to be equipped with power lines or electronic devices, avoiding the risk of electric sparks and local heating. Therefore, it has intrinsic safety and explosion-proof characteristics and is suitable for flammable and explosive environments such as hydrogen.

[0052] Example 2: Hydrogen Sensing Node Structure and Spectral-Spatial Dual Encoding Implementation

[0053] like Figure 3 As shown, the hydrogen sensing module 3 in this embodiment includes a gas diffusion structure 301, an optical resonant sensing chip 302, an optical fiber coupling structure 303, and a packaging structure 304.

[0054] Among them, the gas diffusion structure 301 is used to allow hydrogen molecules from the external environment to enter the optical detection area;

[0055] The optical resonant sensor chip 302 includes a dielectric substrate 3021 and a palladium metal micro / nano structure array 3022 disposed on the surface of the dielectric substrate 3021.

[0056] The palladium metal micro / nano structure array 3022 and the dielectric substrate 3021 together form a metal-dielectric composite optical resonant structure.

[0057] When hydrogen gas is present in the environment, hydrogen molecules enter the region where the palladium metal micro / nano structure array 3022 is located through the gas diffusion structure 301, and undergo a reversible adsorption reaction with palladium metal:

[0058]

[0059] The hydrogenation process of palladium metal causes changes in the complex dielectric parameters of the material, which alters the optical resonance conditions, thereby causing changes in the resonant wavelength, reflected light intensity, or spectral characteristics of the output optical signal.

[0060] In order to achieve identification of different sensing nodes, this embodiment adopts a differentiated design for the optical resonant sensing chip 302 in different hydrogen sensing modules.

[0061] By adjusting the size of the palladium metal micro / nano structure units, the array period, the thickness of the metal layer, the dielectric substrate material, or the structural parameters of the resonant region, different sensing nodes can be made to have different initial resonant wavelengths.

[0062] , , ,

[0063] This forms spectral encoded information.

[0064] like Figure 4 As shown, each sensor node also possesses spatial coding information determined by its installation location:

[0065] , , , ,

[0066] When a certain sensing node responds with hydrogen, the data processing module 5 determines the spectral code of the corresponding node based on the spectral information in the returned light signal, and determines the spatial code based on the propagation time of the returned light.

[0067] Further approval:

[0068]

[0069] Achieve joint matching of spectral coding and spatial coding to determine the identity and spatial location of the response sensing node.

[0070] Simultaneously, the data processing module 5 can establish a sensor node information database, which includes:

[0071] 1) Node number;

[0072] 2) Initial resonant wavelength;

[0073] 3) Installation location;

[0074] 4) Hydrogen concentration calibration parameters.

[0075] To improve the recognition accuracy in multi-node detection environments.

[0076] Example 3: Hydrogen Sensing and Detection Method Based on Spectral-Spatial Dual Encoding

[0077] like Figure 5 As shown, this embodiment provides a multi-node distributed optical fiber hydrogen sensing and detection method based on spectral-spatial dual coding, including the following steps:

[0078] Step S0: Complete node calibration in advance, input the initial wavelength and installation position of each node, and establish a concentration-wavelength drift calibration curve.

[0079] Step S1: Input the detection light signal into the sensing optical fiber 2 that connects multiple hydrogen sensing modules 3 through the light source module 1.

[0080] Step S2: The detection optical signal is transmitted to each hydrogen sensing module 3 via the sensing optical fiber 2. When hydrogen is present in the environment, the hydrogen sensing module 3 generates a corresponding optical response signal and returns it to the optical signal demodulation module 4 via the sensing optical fiber 2.

[0081] Step S3: The optical signal demodulation module 4 acquires the spectral change information in the returned optical signal, based on the change in resonant wavelength:

[0082]

[0083] Obtain the hydrogen response information of the corresponding sensing node.

[0084] Step S4: Determine the spatial location of the sensing node based on the propagation time of the returned optical signal.

[0085]

[0086] Where L is the distance between the sensing node and the optical fiber input end, t is the optical signal propagation time, and n is the effective refractive index of the optical fiber.

[0087] Step S5: Data processing module 5 fuses spectral coding information and spatial coding information to identify and locate the response sensing nodes.

[0088] Step S6: Based on the pre-established calibration relationship between hydrogen concentration and resonant wavelength shift:

[0089]

[0090] Calculate the hydrogen concentration at the corresponding location and output the detection results.

[0091] In this embodiment, the detection method can be applied to hydrogen storage devices, hydrogen transmission pipelines, hydrogen refueling stations, fuel cell systems, and other industrial environments with hydrogen leakage risks, enabling online monitoring of hydrogen leakage in multiple areas.

Claims

1. A multi-node distributed optical fiber hydrogen sensing and detection system based on spectral-spatial dual coding, comprising a light source module, a sensing optical fiber, a multi-node hydrogen sensing module, an optical signal demodulation module, and a data processing module; characterized in that: The sensing fiber is at least one fiber, and multiple hydrogen sensing modules are arranged at intervals along the axial direction of the sensing fiber and coupled to the sensing fiber through an optical multiplexing path. Each hydrogen sensing module is configured with a unique resonant wavelength as a spectral code identifier. The optical signal demodulation module collects the resonant optical signals returned by each hydrogen sensing module. The data processing module calculates the axial position of the corresponding sensing node by combining the spectral code corresponding to the resonant optical signal and the round-trip time of light, and outputs the hydrogen concentration detection result of the corresponding node.

2. The detection system according to claim 1, characterized in that: The hydrogen sensing module includes a gas diffusion structure, an optical resonant sensing chip, and an optical fiber coupling structure; the gas diffusion structure covers the outside of the optical resonant sensing chip; the optical resonant sensing chip includes a dielectric substrate and a palladium metal micro / nano structure array disposed on the surface of the dielectric substrate, the palladium metal micro / nano structure array and the dielectric substrate forming a metal-dielectric composite optical resonant sensing structure.

3. The detection system according to claim 1, characterized in that: Different hydrogen sensing modules correspond to different initial resonant center wavelengths to achieve node identity spectral encoding; the initial resonant center wavelength of the corresponding sensing module is changed by adjusting the structural parameters of the optical resonant sensing chip, wherein the structural parameters are selected from at least one of the following: palladium metal micro / nano structure unit size, array period, metal layer thickness, and dielectric substrate material parameters.

4. The detection system according to claim 1, characterized in that: Each hydrogen sensing module is fixed on the sensing fiber according to a preset axial spacing to form a spatial position code; the data processing module calculates the axial distance between the hydrogen sensing module and the fiber input end based on the round-trip propagation time of the returned light signal, the speed of light, and the effective refractive index of the sensing fiber, and locks the corresponding area of ​​hydrogen leakage based on the calculated axial distance.

5. The detection system according to claim 1, characterized in that: Multiple hydrogen sensing modules are connected to the sensing fiber using a series, main fiber branch parallel, or bypass coupling optical multiplexing optical path. In the series optical path, each hydrogen sensing module is connected in series on the same optical fiber link. In the bypass coupling optical path, each hydrogen sensing module is connected to the main sensing fiber via an optical fiber coupler. All hydrogen sensing modules share the same light source module and the same optical signal demodulation module.

6. The detection system according to claim 1, characterized in that: The optical signal demodulation module is provided with an optical circulator, a spectral analysis unit, and a photoelectric conversion unit along the optical path in sequence; the optical circulator isolates the incident light path and the returned light output light path; the spectral analysis unit extracts the wavelength parameters of the resonant peaks in the returned light signal; the data processing module calculates the difference between the real-time detected resonant wavelength and the preset initial resonant wavelength of each node to obtain the wavelength offset, and outputs the hydrogen concentration value according to the pre-calibrated hydrogen concentration-wavelength offset correspondence.

7. The detection system according to claim 1, characterized in that: The data processing module has a built-in storage unit containing a data mapping relationship. This data mapping relationship includes the spectral encoding identity information of each hydrogen sensing module, the corresponding initial resonant wavelength, and the axial installation position of the optical fiber. The data processing module matches the detected resonant wavelength change information to lock the corresponding sensing node, determines the node's axial position by combining the light round-trip propagation time, and outputs the hydrogen leak location and corresponding hydrogen concentration by fusing spectral encoding and spatial position encoding.

8. A multi-node distributed optical fiber hydrogen sensing and detection method based on spectral-spatial dual coding, characterized in that, Includes the following steps: S0. Pre-calibrate the initial resonant wavelength of each hydrogen sensing module, establish a corresponding model between hydrogen concentration and resonant wavelength offset, and store the initial resonant wavelength of each sensing module and the fiber optic installation location information to form a mapping database. S1. The light source module emits detection light into the sensing optical fiber that is equipped with multiple hydrogen sensing modules, and the detection light is transmitted to each hydrogen sensing module. S2. When the optical resonant sensing chip in the hydrogen sensing module comes into contact with hydrogen, the resonant wavelength parameter changes and a return light signal carrying the resonant characteristics is generated. S3. The optical signal demodulation module collects all returned optical signals and extracts the real-time resonant wavelength corresponding to each signal. S4. Retrieve the pre-stored initial resonant wavelengths of each sensor module and identify the sensor nodes that respond through spectral coding matching; S5. Calculate the axial position of the corresponding sensing node on the sensing fiber based on the round-trip propagation time of the returned optical signal. S6. The hydrogen leak point is determined by the identity of the sensor node obtained through joint matching and the calculated axial position. The hydrogen concentration at the leak point is calculated by combining the resonant wavelength offset and the pre-calibration model.

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