Optical fiber sensor, optical coupling and demodulation system and multi-parameter detection method

Abstract

This application relates to fiber optic sensors, optical coupling and demodulation systems, and a multi-parameter detection method for a single fiber. A biconical micro / nano fiber structure is segmented along its axial direction and covered with a gas-sensitive layer, with a temperature-compensated section at each end. The gas-sensitive layer includes a first gas-sensitive section, a second gas-sensitive section, and a third gas-sensitive section. The first gas-sensitive section adsorbs sulfur dioxide gas, the second gas-sensitive section adsorbs hydrogen sulfide gas, and the third gas-sensitive section adsorbs carbon monoxide gas. This method not only facilitates the detection of the concentrations of sulfur dioxide, hydrogen sulfide, and carbon monoxide gases but also reduces product size and enables spatially distributed monitoring, making it particularly suitable for the sealed environments of gas-insulated switchgear. While avoiding cross-interference, it improves the interaction sensitivity between the optical signal and external gases, thereby enhancing monitoring sensitivity and effectively compensating for environmental interference.

Description

Technical Field

[0001] This application relates to the field of power equipment condition monitoring, and in particular to fiber optic sensors, optical coupling and demodulation systems, and multi-parameter detection methods for a single fiber, also known as multi-sensitive coated micro-nano fiber optic sensors, optical coupling and demodulation systems, and multi-parameter detection methods for a single fiber. Background Technology

[0002] Gas-Insulated Switchgear (GIS), also known as gas-insulated combined equipment, relies primarily on electrochemical sensors or single-coated fiber optic sensors for gas monitoring in traditional technologies. However, these sensors are mainly designed for monitoring single gases and struggle to distinguish multiple decomposition products simultaneously. They are also susceptible to cross-interference, resulting in low detection accuracy. Furthermore, conventional fiber optic sensors exhibit low efficiency in interacting with gases through their evanescent fields, leading to weak responses to low-concentration gases (e.g., less than 5 ppm) and hindering high-sensitivity monitoring. Additionally, environmental factors such as temperature can interfere with long-term stability. Summary of the Invention

[0003] Therefore, it is necessary to provide an optical fiber sensor, an optical coupling and demodulation system, and a method for detecting multiple parameters on a single fiber.

[0004] One embodiment of this application is a multi-sensitive coating micro / nano fiber optic sensor, which includes a biconical micro / nano fiber optic structure and a gas-sensitive layer.

[0005] The gas-sensitive layer is segmented along the axial direction of the biconical micro-nano fiber structure, and a temperature compensation section is provided at the end of the biconical micro-nano fiber structure.

[0006] The gas-sensitive layer includes a first gas-sensitive segment, a second gas-sensitive segment, and a third gas-sensitive segment; wherein, the first gas-sensitive segment is used to adsorb a first gas, the second gas-sensitive segment is used to adsorb a second gas, and the third gas-sensitive segment is used to adsorb a third gas, and the first gas, the second gas, and the third gas are of different types.

[0007] The aforementioned multi-sensitive coated micro-nano fiber optic sensor, through the combination of a biconical micro-nano fiber optic structure and a gas-sensitive layer, overcomes the limitations of traditional electrochemical sensors or single-coated fiber optic sensors designed for a single gas and susceptible to cross-interference. A single fiber integrates the detection of three gases, facilitating the detection of various gas concentrations, reducing product size, and enabling spatially distributed monitoring, particularly suitable for the sealed environments of gas-insulated switchgear. Furthermore, compared to traditional fiber optic sensors, it has a higher proportion of evanescent field energy, thereby improving the interaction sensitivity between the optical signal and external gases while avoiding cross-interference, thus enhancing monitoring sensitivity. Additionally, the temperature compensation section combined with the segmented gas-sensitive layer design effectively compensates for environmental interference, ensuring the long-term stability of the multi-sensitive coated micro-nano fiber optic sensor for monitoring. Finally, it provides a highly selective, highly sensitive, and integrated online monitoring device, enabling simultaneous and accurate detection of multiple gases within gas-insulated switchgear, meeting the needs of equipment miniaturization and real-time early warning, without requiring equipment modification, making it easy to promote and apply. The overall beneficial effects include improving the operation and maintenance efficiency of power equipment and reducing faults and accidents.

[0008] In some embodiments, the first gas includes sulfur dioxide gas, the second gas includes hydrogen sulfide gas, and the third gas includes carbon monoxide gas.

[0009] In some embodiments, the first gas-sensitive segment, the second gas-sensitive segment, and the third gas-sensitive segment are arranged sequentially, and the third gas-sensitive segment is located between the second gas-sensitive segment and the temperature compensation segment.

[0010] In some embodiments, the first gas includes sulfur dioxide gas, the second gas includes hydrogen sulfide gas, and the third gas includes carbon monoxide gas; the first gas sensitive segment, the second gas sensitive segment, and the third gas sensitive segment are arranged in sequence, and the third gas sensitive segment is located between the second gas sensitive segment and the temperature compensation segment.

[0011] In some embodiments, a bare optical fiber segment is provided between the first gas-sensitive segment and the second gas-sensitive segment, and a bare optical fiber segment is provided between the second gas-sensitive segment and the third gas-sensitive segment.

[0012] In some embodiments, the lengths of the first gas-sensitive segment, the second gas-sensitive segment, and the third gas-sensitive segment are all 1cm to 2cm, and the interval between any two adjacent gas-sensitive segments is 0.3cm to 0.7cm.

[0013] In some embodiments, the first gas sensing segment comprises a Pd-doped WO3 nanofilm, the second gas sensing segment comprises Au-modified MoS2 quantum dots, and the third gas sensing segment comprises a MOF-199 film.

[0014] In some embodiments, the temperature compensation section is a bare optical fiber; or,

[0015] The biconical micro / nano fiber structure is fabricated using a fused taper process, with the taper diameter ranging from 5 μm to 10 μm.

[0016] In some embodiments, the gas-sensitive layer is deposited on the biconical micro / nano fiber structure using a sol-gel method or chemical vapor deposition.

[0017] In some embodiments, an optical coupling and demodulation system includes a supercontinuum broadband light source, a three-port fiber optic circulator, and a spectrometer.

[0018] The supercontinuum broadband light source is used to emit optical signals in the 1520nm to 1620nm wavelength band;

[0019] The first port of the three-port fiber optic circulator is connected to the supercontinuum broadband light source, the second port is connected to the multi-sensitive coated micro / nano fiber optic sensor of any embodiment, and the third port is connected to the spectrometer.

[0020] In some embodiments, the optical coupling and demodulation system further includes the multi-sensitive coated micro / nano fiber optic sensor disposed in a gas-insulated switchgear; or,

[0021] The optical coupling and demodulation system further includes a host computer configured to connect the supercontinuum broadband light source and the spectrometer, respectively; or,

[0022] The spectrometer is a high-speed spectrometer based on FPGA.

[0023] In some embodiments, a method for detecting multiple parameters on a single fiber includes the following steps:

[0024] The multi-sensory coating micro-nano fiber optic sensor described in any embodiment is used to acquire the induced light information of sulfur dioxide gas, hydrogen sulfide gas, and carbon monoxide gas;

[0025] Demodulate the sensed light information to obtain a demodulated signal;

[0026] The demodulated signal was processed using a partial least squares regression algorithm to obtain the concentration values ​​of sulfur dioxide, hydrogen sulfide, and carbon monoxide.

[0027] An alarm signal will be issued when the concentration of any of the sulfur dioxide, hydrogen sulfide, and carbon monoxide gases exceeds a preset threshold. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of an embodiment of the multi-sensory coating micro / nano fiber optic sensor described in this application.

[0030] Figure 2 This is a connection diagram of an embodiment of the optical coupling and demodulation system described in this application.

[0031] Reference numerals: 100, Multi-sensory coating micro / nano fiber optic sensor; 110, Biconical micro / nano fiber optic structure; 111, Axial direction; 112, Temperature compensation section; 120, Gas-sensitive layer; 121, First gas-sensitive section; 122, Second gas-sensitive section; 123, Third gas-sensitive section; 200, Optical coupling and demodulation system; 210, Supercontinuum broadband light source; 220, Three-port fiber optic circulator; 230 Spectrometer; 240, Host computer; 300, Gas chamber. Detailed Implementation

[0032] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0033] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or there may be an intermediate component. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application's specification are for illustrative purposes only and do not represent the only possible implementation.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0035] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature and the second feature are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0037] This application discloses an optical fiber sensor, an optical coupling and demodulation system, and a method for detecting multiple parameters on a single fiber, which includes some or all of the technical features of the following embodiments. In one embodiment of this application, such as Figure 1 As shown, a multi-sensitive coating micro / nano fiber optic sensor 100 includes a biconical micro / nano fiber optic structure 110 and a gas-sensitive layer 120. The biconical micro / nano fiber optic structure 110 is segmented along the axial direction 111 and covered with the gas-sensitive layer 120, and the biconical micro / nano fiber optic structure 110 has a temperature compensation section 112 at its end. The gas-sensitive layer 120 includes a first gas-sensitive section 121, a second gas-sensitive section 122, and a third gas-sensitive section 123. The first gas-sensitive section is used to adsorb a first gas, the second gas-sensitive section is used to adsorb a second gas, and the third gas-sensitive section is used to adsorb a third gas. The first gas, the second gas, and the third gas are of different types.

[0038] This design, through the combination of a biconical micro-nano fiber structure and a gas-sensitive layer, overcomes the limitations of traditional electrochemical sensors or single-coated fiber sensors designed for a single gas and susceptible to cross-interference. A single fiber integrates the detection of three gases, facilitating the detection of various gas concentrations, reducing product size, and enabling spatially distributed monitoring, particularly suitable for the sealed environments of gas-insulated switchgear. Furthermore, compared to traditional fiber sensors, the higher proportion of evanescent field energy enhances the interaction sensitivity between the optical signal and external gases while avoiding cross-interference, thus improving monitoring sensitivity. Additionally, the temperature compensation section, combined with the segmented gas-sensitive layer design, effectively compensates for environmental interference, ensuring the long-term stability of the multi-sensitive coated micro-nano fiber sensor for monitoring. Finally, it provides a highly selective, highly sensitive, and integrated online monitoring device, enabling simultaneous and accurate detection of multiple gases within gas-insulated switchgear, meeting the needs of equipment miniaturization and real-time early warning. It requires no equipment modification, is easy to promote and apply, and its overall benefits include improved power equipment operation and maintenance efficiency and reduced failures.

[0039] An evanescent field is an electromagnetic field that, when light waves undergo total internal reflection at the interface of two media with different refractive indices, still penetrates to the side with the lower refractive index and attenuates exponentially in the vertical direction. This application utilizes this characteristic in its various embodiments. In some embodiments, the biconical micro / nano fiber structure is fabricated using a fused taper process, with the taper diameter ranging from 5 μm to 10 μm. The biconical micro / nano fiber structure is created by fused tapering ordinary optical fibers to form a biconical structure that is thicker at both ends and thinner in the middle. The core diameter of the taper region can be reduced to the micrometer or even nanometer scale, which is close to or smaller than the wavelength of the transmitted light. In this state, the guiding mode constraint capability of the fiber is significantly weakened, and a large amount of optical energy penetrates into the cladding or air medium outside the fiber, forming a strong evanescent field. Therefore, through the direct interaction between the evanescent field and the medium surrounding the fiber, changes in parameters such as the refractive index and concentration of the medium will cause changes in the phase and intensity of the evanescent field. By detecting changes in the optical signal, a sensing function can be achieved, thereby enabling applications such as biomolecule detection and environmental gas concentration monitoring. As an example, the cone diameter of the biconical micro / nano fiber structure is 5 μm or 6 μm. In various embodiments, the biconical micro / nano fiber structure has a temperature compensation section at its end; in some embodiments, the temperature compensation section is a bare fiber, i.e., an uncovered fiber. As an example, the temperature compensation section is covered with a temperature-sensitive protective layer. As an example, the protective layer is a polyimide (PI) film. For the embodiments with a first gas-sensitive section, a second gas-sensitive section, and a third gas-sensitive section described below, as an example, the fiber segment between the first gas-sensitive section and the second gas-sensitive section, and the fiber segment between the second gas-sensitive section and the third gas-sensitive section, are all covered with the protective layer. As an example, the protective layer is applied first, and then the first gas-sensitive section, the second gas-sensitive section, and the third gas-sensitive section are formed.

[0040] This design leverages the maturity and reliability of the fused ablation process, allowing for precise control of the cone diameter. This size range maximizes the evanescent field energy ratio, further enhancing the interaction between the optical signal and the target gas compared to traditional fiber optic sensor cone designs. While retaining the advantage of non-interference in multi-gas detection, it significantly improves detection sensitivity, ensuring accurate capture even of low-concentration gases and providing reliable support for early warning of minute leaks within gas-insulated switchgear. Furthermore, the precisely controllable micro-nano-scale cone size combined with a simple structure further compresses the sensor's volume, making it more suitable for confined, sealed equipment interiors. It allows for convenient deployment without modifying existing equipment, enhancing integration advantages and reducing on-site installation difficulty, perfectly meeting the core requirements of equipment miniaturization and real-time monitoring. Finally, the temperature compensation section employs a flexible design using either bare fiber or a temperature-sensitive protective layer: the bare fiber solution is simple in structure and cost-effective, while the temperature-sensitive protective layer achieves more precise temperature drift compensation. Both designs effectively avoid interference from temperature fluctuations on the detection signal, adapting to more complex operating conditions compared to traditional single compensation methods, further ensuring long-term operational stability and data accuracy. On the other hand, the mature fused taper process facilitates mass production, and the consistency of the taper diameter ensures the uniformity of product performance, reducing the cost of large-scale application. At the same time, the simplified structure reduces potential faults. Combined with the advantages of high sensitivity and high selectivity, it further improves the operation and maintenance efficiency of power equipment, reduces faults caused by gas leaks, and helps to promote the intelligent and efficient operation and maintenance of power equipment, making it easy to promote and apply on a large scale.

[0041] In various embodiments, the biconical micro / nano fiber structure is segmented along the axial direction and covered with the gas-sensitive layer to facilitate simultaneous and accurate detection of multiple gases within the GIS, meeting the requirements for equipment miniaturization and real-time early warning. Alternatively, it can be understood that the biconical micro / nano fiber structure is segmented along the axial direction and has the gas-sensitive layer formed thereon. As an example, the gas-sensitive layer is sensitive to the decomposition products of sulfur hexafluoride inside gas-insulated switchgear, and can adsorb these decomposition products, including sulfur dioxide, hydrogen sulfide, and carbon monoxide gases. In some embodiments, the gas-sensitive layer is deposited on the biconical micro / nano fiber structure using a sol-gel method or chemical vapor deposition (CVD).

[0042] This design, on the one hand, utilizes a biconical micro-nano fiber structure with segmented gas-sensitive layers along the axial direction. Each sensitive segment precisely corresponds to the decomposition products of sulfur hexafluoride, enabling targeted adsorption and detection. This completely overcomes the cross-interference problem inherent in traditional sensors that detect multiple gases. It ensures the accuracy of simultaneous detection of the three decomposition products while achieving multi-dimensional detection functionality within a single sensor, eliminating the need for multiple additional detection devices and significantly optimizing the layout of the GIS internal detection system. On the other hand, the gas-sensitive layers are prepared using either a sol-gel method or chemical vapor deposition. Both processes offer advantages such as maturity, controllability, and high coating uniformity, ensuring a tight fit between the sensitive layer and the biconical micro-nano fiber structure. This avoids disrupting the energy distribution of the fiber's evanescent field and maximizes the contact area between the sensitive layer and the gas, significantly improving the interaction efficiency between the optical signal and the target gas. This allows the sensor to respond quickly even to trace amounts of sulfur hexafluoride decomposition products, further enhancing detection sensitivity. On the other hand, the segmented coverage structure design eliminates the need for additional sensor axial dimensions. Combined with the compact form of the biconical micro-nano optical fiber, this further solidifies the equipment's miniaturization advantage, perfectly fitting the confined internal space of GIS equipment. Furthermore, it can be deployed directly without structural modifications to existing equipment, fully meeting the core requirement of real-time early warning and significantly reducing implementation costs in the field. On another front, the targeted detection of sulfur hexafluoride decomposition products directly addresses the core need for insulation fault early warning in GIS equipment. Mature manufacturing processes ensure the stability and consistency of mass production. Combined with high selectivity and high sensitivity detection performance, it can promptly capture early fault signals within the equipment, providing accurate data support for power equipment operation and maintenance, effectively improving maintenance efficiency and reducing accidents. It also possesses strong practicality and promotional value, contributing to the improvement of the intelligent monitoring system for GIS equipment.

[0043] In various embodiments, the gas-sensitive layer includes a first gas-sensitive segment, a second gas-sensitive segment, and a third gas-sensitive segment. In some embodiments, the first gas includes sulfur dioxide gas, the second gas includes hydrogen sulfide gas, and the third gas includes carbon monoxide gas. As an example, the first gas-sensitive segment is used to adsorb sulfur dioxide gas, the second gas-sensitive segment is used to adsorb hydrogen sulfide gas, and the third gas-sensitive segment is used to adsorb carbon monoxide gas. As an example, the first, second, and third gas-sensitive segments are fabricated using a segmented coating process. In some embodiments, the first gas-sensitive segment includes a Pd-doped WO3 nanofilm, the second gas-sensitive segment includes Au-modified MoS2 quantum dots, and the third gas-sensitive segment includes a MOF-199 film. As an example, the third gas-sensitive segment includes a metal-organic framework MOF-199 film to create gaps in the microlayer.

[0044] This design, on the one hand, clearly defines the first, second, and third gas sensitive sections and assigns them specific functions for adsorbing sulfur dioxide, hydrogen sulfide, and carbon monoxide gases. Leveraging the highly specific adsorption properties of each sensitive material for the target gases, it fundamentally eliminates cross-interference issues during multi-gas detection. Compared to traditional single-function or non-specific coating sensors, the detection accuracy is significantly improved, accurately capturing minute changes in sulfur hexafluoride decomposition products inside gas-insulated switchgear, providing precise data support for equipment fault early warning. On the other hand, the segmented coating process ensures that the coating of each sensitive section is uniform, dense, and has clear boundaries. This avoids mutual interference between different sensitive materials and allows each sensitive layer to be tightly bonded to the biconical micro / nano fiber structure, fully utilizing the high proportion of evanescent field energy in the fiber to maximize the interaction efficiency between the optical signal and the target gas. On the one hand, Pd-doped WO3 nanofilms, Au-modified MoS2 quantum dots, and MOF-199 films all possess high specific surface area and high gas adsorption activity. Combined with a segmented coating process, this further shortens the gas response time, enabling rapid and simultaneous detection of three gases and meeting real-time early warning requirements. On the other hand, the segmented coating process is mature and controllable, allowing for adjustments to the length and thickness of each sensitive segment according to actual detection needs, adapting to different specifications of gas-insulated switchgear. Furthermore, the chemical stability of each sensitive material is excellent, making it less prone to aging and failure in the sealed environment of the equipment. Combined with the design of a temperature compensation segment, it effectively resists the impact of environmental factors on detection performance, significantly improving the long-term operational stability of the multi-sensitive coated micro-nano fiber optic sensor and reducing maintenance and replacement costs. Moreover, a single sensor integrates the detection functions of three highly specific gases, eliminating the need for multiple additional detection devices, significantly reducing the overall size of the detection system. It perfectly fits the confined internal space of gas-insulated switchgear and can be easily installed and deployed without structural modifications to existing equipment. Therefore, it is easy to promote and apply.

[0045] In some embodiments, the first gas sensing segment, the second gas sensing segment, and the third gas sensing segment are arranged sequentially, and the third gas sensing segment is located between the second gas sensing segment and the temperature compensation segment. In some embodiments, the first gas includes sulfur dioxide gas, the second gas includes hydrogen sulfide gas, and the third gas includes carbon monoxide gas; the first gas sensing segment, the second gas sensing segment, and the third gas sensing segment are arranged sequentially, and the third gas sensing segment is located between the second gas sensing segment and the temperature compensation segment; other embodiments follow the same pattern and will not be described in detail. In some embodiments, there is a bare optical fiber segment between the first gas sensing segment and the second gas sensing segment, and there is also a bare optical fiber segment between the second gas sensing segment and the third gas sensing segment; that is, the first gas sensing segment and the second gas sensing segment are discontinuous, i.e., not in contact, and the second gas sensing segment and the third gas sensing segment are discontinuous, i.e., not in contact, so as to separate the first gas sensing segment, the second gas sensing segment, and the third gas sensing segment from each other.

[0046] This design, on the one hand, separates the first, second, and third gas sensitive sections with bare optical fiber segments, completely eliminating material interference and cross-contamination issues caused by direct contact between different sensitive sections. This allows each sensitive layer to independently and accurately perform adsorption and detection of the target gas. Compared to a design without gaps, this further improves the specificity and data accuracy of simultaneous multi-gas detection, providing more reliable gas concentration data support for internal fault diagnosis of gas-insulated switchgear. On the other hand, the sequential arrangement of the three sensitive sections, with the third gas sensitive section adjacent to the temperature compensation section, allows the temperature compensation effect to more directly cover the third sensitive section at the end. Simultaneously, the buffering effect of the bare optical fiber segments ensures that the temperature compensation effect is evenly radiated throughout the sensitive area, effectively offsetting the impact of ambient temperature fluctuations on the detection signals of each sensitive section. Combined with the core function of the temperature compensation section, this further enhances the long-term operational stability of the multi-sensitive coated micro-nano fiber optic sensor, adapting to temperature variation conditions in GIS sealed environments. On the other hand, the bare fiber spacing design does not increase the radial dimension of the sensor, and the sequential axial layout perfectly matches the biconical micro / nano fiber structure. This maintains the sensor's compactness while reserving independent gas contact and optical signal interaction space for each sensitive segment, ensuring that the evanescent field energy can fully play its role in each sensitive segment. This avoids optical signal attenuation caused by the superposition of sensitive layers, ensuring high sensitivity while continuing to meet the needs of device miniaturization and spatially distributed monitoring. Furthermore, the independent spacing design not only reduces performance interference between different sensitive materials but also facilitates precise parameter adjustment for the detection needs of each sensitive segment. Moreover, if a sensitive segment needs maintenance or replacement in the future, there is no need to disassemble the entire sensor, reducing maintenance difficulty and cost.

[0047] In some embodiments, the lengths of the first, second, and third gas-sensitive segments are all 1 cm to 2 cm, and the interval between any two adjacent gas-sensitive segments is 0.3 cm to 0.7 cm. As an example, the lengths of the first, second, and third gas-sensitive segments are all between 1 cm and 2 cm, and the interval between them is between 0.3 cm and 0.7 cm. As an example, the lengths of the first, second, and third gas-sensitive segments are all 1.5 cm, and the interval between them is 0.5 cm. Other embodiments follow the same principle and will not be elaborated further.

[0048] This design offers several advantages. First, the length of the sensitive section ensures sufficient gas adsorption area for each segment, fully leveraging the adsorption activity of materials such as Pd-doped WO3 nanofilms, while avoiding light signal attenuation due to excessive length. The 0.3cm to 0.7cm interval further enhances the independent isolation of each sensitive section, completely eliminating cross-interference during gas adsorption and ensuring accurate detection of sulfur dioxide, hydrogen sulfide, and carbon monoxide. Second, the standardized size range facilitates mass production, ensuring consistent product performance and reducing the cost of large-scale applications. The reasonable size combination also allows for a more compact sensor structure, perfectly fitting the confined space of gas-insulated switchgear and meeting the miniaturization requirements. Third, flexible size selection adapts to different gas concentration detection scenarios, optimizing response efficiency without adjusting the overall structure. Combined with the temperature compensation section design, this further enhances the sensor's environmental adaptability and long-term stability.

[0049] As an example, the multi-sensitivity coated micro / nano fiber optic sensor is the core unit of the detection design presented in this paper. Its fabrication process employs a fused taper process to draw a standard single-mode fiber into a biconical structure, with the taper diameter precisely controlled within the range of 5-10 μm to maximize the evanescent field energy ratio, thereby enhancing the interaction sensitivity between the optical signal and the external gas. Along the axial direction of the micro / nano optical fiber, three specific gas-sensitive materials are sequentially coated in segments: the SO2 sensitive segment uses a Pd-doped WO3 nanofilm with a thickness controlled at 50-100 nm. The Pd catalyst enhances the chemisorption reaction of SO2 by WO3, leading to a local refractive index change and thus a spectral shift at the characteristic wavelength of 1550 nm. The H2S sensitive segment uses Au-modified MoS2 quantum dots with a particle size of 5-10 nm. The coordination between Au nanoparticles and H2S induces a change in the light absorption characteristics in the 1580 nm band, enabling power attenuation detection. The CO sensitive segment is coated with a metal-organic framework (MOF-199) film. Through its unique pore size sieving effect (approximately 1.2 nm), it selectively adsorbs CO molecules, modulating the transmitted light intensity in the 1600 nm band. Each sensitive segment is 1-2 cm long, spaced 0.5 cm apart to prevent signal crosstalk. The coating process employs sol-gel or chemical vapor deposition to ensure coating uniformity exceeding 95%. Based on the spectral response characteristics of the sensitive material, non-overlapping characteristic wavelengths are selected to achieve spectral separation. Furthermore, a section of bare fiber without the sensitive material is placed at the end of the optical fiber as a temperature compensation section. This section is used to monitor in real time the interference of ambient temperature on optical transmission characteristics, such as baseline drift caused by thermal expansion, thereby providing an interference correction reference.

[0050] This design, on the one hand, utilizes a mature and reliable fused taper process to fabricate a biconical micro / nano fiber structure, precisely controlling the diameter of the taper region to maximize the evanescent field energy ratio, laying the foundation for efficient interaction between optical signals and gases. Simultaneously, it selectively employs three specific sensitive materials, combining their unique chemical adsorption, coordination, and pore size sieving effects, along with non-overlapping characteristic wavelengths such as 1550nm, 1580nm, and 1600nm to achieve spectral separation. This completely overcomes the cross-interference problem of traditional multi-gas detection, enabling simultaneous and precise capture of minute changes in SO2, H2S, and CO gases, significantly improving detection specificity and accuracy, and providing accurate data support for early warning of internal faults in gas-insulated switchgear (GIS). On the other hand, precise parameter control of each gas-sensitive segment, combined with the over 95% coating uniformity achieved through sol-gel or chemical vapor deposition processes, ensures both the adsorption activity and response efficiency of the sensitive materials while avoiding signal fluctuations caused by uneven coating, significantly shortening the gas detection response time and lowering the detection limit. Even when facing trace amounts of sulfur hexafluoride decomposition products within GIS, it can respond quickly, perfectly meeting the needs of real-time early warning. On the other hand, the design of the sensitive section length and spacing ensures sufficient gas adsorption area for each sensitive section while further eliminating signal crosstalk through physical isolation. The temperature compensation section of the bare optical fiber at the end corrects for environmental interference such as baseline drift caused by thermal expansion in real time. With this dual protection, the sensor can maintain long-term stable operation in complex working conditions such as temperature fluctuations in the GIS sealed environment, effectively reducing the risk of data deviation. Furthermore, the single multi-sensory coating micro-nano fiber optic sensor integrates three gas detection functions, eliminating the need for additional multiple sets of devices. Combined with the micro-nano-level structural design, it significantly reduces the size of the detection system, making it perfectly suited for the confined space of GIS sealed environments.

[0051] In some of these embodiments, such as Figure 2 As shown, an optical coupling and demodulation system 200 includes a supercontinuum broadband light source 210, a three-port fiber optic circulator 220, and a spectrometer 230. The supercontinuum broadband light source 210 is used to emit optical signals in the 1520nm to 1620nm wavelength band. The first port of the three-port fiber optic circulator 220 is connected to the supercontinuum broadband light source, the second port is connected to the multi-sensitive coated micro / nano fiber optic sensor 100 described in any embodiment, and the third port is connected to the spectrometer 230. In an application example, such as... Figure 2In the illustrated embodiment, the multi-sensitive coated micro / nano fiber optic sensor 100 is disposed within the gas chamber 300 of the gas-insulated switchgear. It is understood that, since the multi-sensitive coated micro / nano fiber optic sensor described in any embodiment is used, the optical coupling and demodulation system also possesses the beneficial technical effects of the multi-sensitive coated micro / nano fiber optic sensor, which will not be elaborated upon here. Furthermore, the optical coupling and demodulation system employing the multi-sensitive coated micro / nano fiber optic sensor can perform online monitoring, and therefore can also be referred to as a multi-component gas online monitoring device based on segmented functionalized micro / nano fibers.

[0052] As an example, the optical coupling and demodulation system is a device that utilizes micro-nano fiber optic sensors to achieve online monitoring of multiple gases inside gas-insulated switchgear. It can be directly applied to the safety monitoring and fault diagnosis of high-voltage electrical equipment, and is suitable for core equipment in power systems such as substations, new energy power plants, and rail transit. The optical coupling and demodulation system has the advantages of high selectivity, high sensitivity, and integration. Through optical sensing principles, it performs real-time detection of SF6 gas and its decomposition products, thereby improving equipment operational reliability and environmental safety. The optical coupling and demodulation system combines fiber optic sensing, spectral analysis, and materials science, which helps to overcome the limitations of traditional monitoring methods, thus promoting the development of smart grids.

[0053] In some embodiments, the optical coupling and demodulation system further includes the multi-sensitive coated micro / nano fiber optic sensor disposed in a gas-insulated switchgear. In some embodiments, the spectrometer is an FPGA-based high-speed spectrometer. In some embodiments, such as Figure 2 As shown, the optical coupling and demodulation system 200 further includes a host computer 240 connected to the spectrometer 230; in other embodiments, the host computer is connected to both the supercontinuum broadband light source and the spectrometer. As an example, the host computer is used to control the supercontinuum broadband light source and / or the spectrometer. As an example, the host computer is configured to process the demodulated signal based on a partial least squares regression (PLSR) algorithm to obtain the concentration values ​​of sulfur dioxide, hydrogen sulfide, and carbon monoxide; and to issue an alarm signal when any one of the concentration values ​​of sulfur dioxide, hydrogen sulfide, and carbon monoxide exceeds a preset threshold.

[0054] This design integrates a multi-sensitive coated micro / nano fiber optic sensor into an optical coupling and demodulation system deployed within a gas-insulated switchgear. Paired with an FPGA-based high-speed spectrometer, the high-speed data processing capabilities of the FPGA significantly improve the efficiency of demodulated signal acquisition and analysis, overcoming the response lag issues of traditional spectrometers. This synergy with the sensor's high sensitivity enables rapid and synchronous demodulation of sulfur dioxide, hydrogen sulfide, and carbon monoxide gases, ensuring timely detection of even trace gas concentration changes and providing core technical support for real-time monitoring. Furthermore, the host computer provides unified control of the supercontinuum broadband light source and / or spectrometer, simplifying system operation and avoiding the cumbersome and error-prone nature of independent multi-device control. The application of the PLSR algorithm, compared to traditional data processing algorithms, more accurately extracts effective information from complex demodulated signals, effectively reducing noise interference and significantly improving the calculation accuracy of the three gas concentration values, thus solving the problem of errors easily occurring in multi-component gas concentration inversion. On the other hand, the threshold alarm function of the host computer forms a closed-loop monitoring system. When the concentration of any gas exceeds the preset threshold, an alarm signal is issued immediately, completely changing the limitation of traditional manual inspections in terms of real-time early warning. It can quickly trigger maintenance response, avoid GIS equipment insulation failures caused by gas leaks in advance, and minimize accident losses, perfectly meeting the core requirement of real-time equipment early warning. Furthermore, the entire system achieves full-process integration of detection, demodulation, analysis, control, and alarm. It can be easily deployed without structural modifications to the original GIS equipment, adapting to the needs of equipment miniaturization. Mature hardware and software co-design and precise empowerment of the PLSR algorithm further ensure the reliability of monitoring data and the stability of system operation, significantly reducing manual maintenance costs, effectively improving the intelligence level and efficiency of power equipment maintenance, reducing the incidence of failures and accidents, and possessing strong practical value and broad application prospects.

[0055] As an example, the optical coupling and demodulation system includes a multi-sensor coated micro / nano fiber optic sensor, a supercontinuum broadband light source, a three-port fiber optic circulator, a spectrometer, and a host computer. The micro / nano fiber is fabricated using a fused taper process, with a taper diameter of 5 μm to 10 μm. Along the axial direction, it is segmented with Pd-doped WO3 nanofilms as SO2-sensitive segments, with a thickness of 50 nm to 100 nm; Au-modified MoS2 quantum dots (Au-MoS2 QDs) as H2S-sensitive segments, with a particle size of 5 nm to 10 nm; and MOF-199 films as CO-sensitive segments. A bare fiber temperature compensation segment is provided at the end. The light source is a 1520 nm to 1620 nm broadband light. The signal is coupled via a circulator, and the spectral shift Δλ and power attenuation ΔP are acquired. The concentration is calculated using a partial least squares regression algorithm.

[0056]

[0057] in, This represents the temperature interference gain coefficient. This embodiment effectively improves sensitivity by enhancing the evanescent field effect, enabling multi-parameter detection on a single fiber, and can be used as a multi-parameter detection method on a single fiber.

[0058] The above embodiments, through the combination of multi-sensitive coatings and micro / nano fiber structures, are applied to optical coupling and demodulation systems. Compared with traditional single-fiber technology, actual measurements show that the evanescent field energy ratio is increased by more than 30%, the sensitivity is increased by 10 to 100 times, and simultaneous detection of SO2, H2S, and CO is achieved, with cross-interference reduced by 95%. The single-fiber integrated design reduces the volume by 30%, thereby reducing costs by 20%. The real-time monitoring response time is less than 30 seconds, and it supports GIS flange interface implantation without the need for equipment modification. The overall beneficial effects are improved operation and maintenance efficiency of power equipment, reduced failures and accidents, significant economic benefits, and reduced greenhouse gas leakage.

[0059] As an example, the optical coupling and demodulation system is responsible for the injection, transmission, and analysis of optical signals. This system includes a supercontinuum broadband light source covering the 1520nm to 1620nm wavelength band, a three-port fiber optic circulator, and a high-speed spectral analyzer based on an FPGA. The working principle is as follows: the optical signal emitted by the broadband light source is input through the first port of the circulator and coupled to a micro / nano fiber optic sensor through the second port. Inside the GIS monitoring cavity, the optical signal undergoes specific interactions with the target gas, such as SO2, H2S, or CO, and the reflected spectral signal is directionally transmitted to the spectral demodulation module through the third port. This module acquires the transmission spectral shift Δλ and optical power attenuation ΔP in real time for different sensitive segments, with a sampling rate of up to 100Hz, ensuring real-time dynamic monitoring. To further enhance anti-interference capabilities, the system also integrates a humidity compensation function, monitoring signal drift caused by humidity through an additional bare fiber segment and correcting it using a temperature compensation mechanism. It can also work with a host computer for data processing and user interaction. The demodulated signal is received via an Ethernet interface, and the host computer runs a multi-parameter coupling model based on the PLSR algorithm to achieve accurate inversion of gas concentration.

[0060] As an example, the PLSR model establishes a regression relationship between X and gas concentration Y by extracting principal components as follows.

[0061]

[0062] Wherein, the independent variable matrix X represents the input spectral signal matrix, the dependent variable matrix Y represents the gas concentration matrix, and F* is the residual matrix.

[0063]

[0064] W represents the weight matrix, used to extract principal components; P and Q represent the loading matrices, describing the relationship between the variables and the principal components; and B represents the diagonal matrix of internal regression coefficients. The original signal for the sensitive segment is:

[0065]

[0066] Where S gas For a pure gas response signal, S temp For temperature interference, S noise Since it is noise, the signal for the compensation section is:

[0067]

[0068] Where α represents the temperature interference gain coefficient.

[0069]

[0070] Where β represents the sensitivity correction factor to ensure the stability of the input spectral signal.

[0071] Ignoring noise, the pure gas signal is:

[0072]

[0073] The system calculates and outputs the concentration values ​​of SO2, H2S, and CO, and displays the curves in real time. When the concentration exceeds the preset threshold, such as SO2 > 5 ppm, an audible and visual alarm is triggered, thus realizing fault early warning.

[0074] In some embodiments, a single-fiber multi-parameter detection method includes the following steps: acquiring induced light information of sulfur dioxide gas, hydrogen sulfide gas, and carbon monoxide gas using a multi-sensitive coated micro / nano fiber optic sensor as described in any embodiment; demodulating the induced light information to obtain a demodulated signal; processing the demodulated signal using a partial least squares regression algorithm to obtain the concentration values ​​of sulfur dioxide gas, hydrogen sulfide gas, and carbon monoxide gas; and issuing an alarm signal when any one of the concentration values ​​of sulfur dioxide gas, hydrogen sulfide gas, and carbon monoxide gas exceeds a preset threshold. It is understood that, since the multi-sensitive coated micro / nano fiber optic sensor as described in any embodiment is used, the single-fiber multi-parameter detection method also possesses the beneficial technical effects of the multi-sensitive coated micro / nano fiber optic sensor, which will not be elaborated upon here.

[0075] This design ensures high selectivity and interference resistance as much as possible. The coating material selection is based on the specific reaction between gas molecules and nanostructures, the fiber taper design optimizes the light field distribution, and the algorithm handles multivariate coupling to achieve high concentration reflectivity accuracy. In prototype product testing, the detection limit is below 1 ppm, the response time is below 30 seconds, and the cross-interference is below 2%. Compared with traditional fiber optic equipment, the size is reduced by 30% and the cost is reduced by 20%. When applied to GIS, based on the failure rate percentage, it can reduce GIS power outage losses by at least 5 million yuan annually.

[0076] It should be noted that other embodiments of this application also include multi-sensitive coated micro / nano fiber optic sensors, optical coupling and demodulation systems, and multi-parameter detection methods formed by combining the technical features of the above embodiments.

[0077] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the patent protection scope of this application should be determined by the appended claims.

Claims

1. A multi-sensory coated micro / nano fiber optic sensor, characterized in that, Including a biconical micro / nano fiber structure and a gas-sensitive layer; The gas-sensitive layer is segmented along the axial direction of the biconical micro-nano fiber structure, and a temperature compensation section is provided at the end of the biconical micro-nano fiber structure. The gas-sensitive layer includes a first gas-sensitive segment, a second gas-sensitive segment, and a third gas-sensitive segment; wherein, the first gas-sensitive segment is used to adsorb a first gas, the second gas-sensitive segment is used to adsorb a second gas, and the third gas-sensitive segment is used to adsorb a third gas, and the first gas, the second gas, and the third gas are of different types.

2. The multi-sensory coating micro / nano fiber optic sensor according to claim 1, characterized in that, The first gas includes sulfur dioxide gas, the second gas includes hydrogen sulfide gas, and the third gas includes carbon monoxide gas; The first gas-sensitive segment, the second gas-sensitive segment, and the third gas-sensitive segment are arranged in sequence, and the third gas-sensitive segment is located between the second gas-sensitive segment and the temperature compensation segment.

3. The multi-sensory coating micro / nano fiber optic sensor according to claim 2, characterized in that, There is a bare optical fiber segment between the first gas-sensitive segment and the second gas-sensitive segment, and there is a bare optical fiber segment between the second gas-sensitive segment and the third gas-sensitive segment.

4. The multi-sensory coating micro / nano fiber optic sensor according to claim 3, characterized in that, The lengths of the first gas-sensitive segment, the second gas-sensitive segment, and the third gas-sensitive segment are all 1cm to 2cm, and the interval between any two adjacent gas-sensitive segments is 0.3cm to 0.7cm.

5. The multi-sensory coating micro / nano fiber optic sensor according to claim 1, characterized in that, The first gas-sensitive segment includes a Pd-doped WO3 nanofilm, the second gas-sensitive segment includes Au-modified MoS2 quantum dots, and the third gas-sensitive segment includes a MOF-199 film.

6. The multi-sensory coating micro / nano fiber optic sensor according to claim 1, characterized in that, The temperature compensation section is a bare optical fiber; or... The biconical micro / nano fiber structure is fabricated using a fused taper process, with the taper diameter ranging from 5 μm to 10 μm.

7. The multi-sensory coated micro / nano fiber optic sensor according to any one of claims 1 to 6, characterized in that, The gas-sensitive layer is deposited on the biconical micro / nano fiber structure using a sol-gel method or chemical vapor deposition.

8. An optical coupling and demodulation system, characterized in that, This includes a supercontinuum broadband light source, a three-port fiber optic circulator, and a spectrometer; The supercontinuum broadband light source is used to emit optical signals in the 1520nm to 1620nm wavelength band; The first port of the three-port fiber optic circulator is connected to the supercontinuum broadband light source, the second port is connected to the multi-sensitive coated micro / nano fiber optic sensor as described in any one of claims 1 to 7, and the third port is connected to the spectrometer.

9. The optical coupling and demodulation system according to claim 8, characterized in that, The optical coupling and demodulation system further includes the multi-sensitive coated micro / nano fiber optic sensor disposed in a gas-insulated switchgear; or... The optical coupling and demodulation system further includes a host computer configured to connect the supercontinuum broadband light source and the spectrometer, respectively; or, The spectrometer is a high-speed spectrometer based on FPGA.

10. A method for detecting multiple parameters in a single fiber, characterized in that, Including the following steps: The multi-sensory coating micro-nano fiber optic sensor as described in any one of claims 1 to 7 is used to acquire the induced light information of sulfur dioxide gas, hydrogen sulfide gas and carbon monoxide gas; Demodulate the sensed light information to obtain a demodulated signal; The demodulated signal was processed using a partial least squares regression algorithm to obtain the concentration values ​​of sulfur dioxide, hydrogen sulfide, and carbon monoxide. An alarm signal will be issued when the concentration of any of the sulfur dioxide, hydrogen sulfide, and carbon monoxide gases exceeds a preset threshold.

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