Micro conical fiber bragg grating gas sensing device based on gas sensitive material and use method

Abstract

The invention belongs to the technical field of optical fiber gas sensing detection, and discloses a gas sensitive material-based micro-conical fiber bragg grating gas sensing device, which comprises a broadband light source, the generation end of the broadband light source is connected with a single-mode optical fiber, the outer side of the single-mode optical fiber is sequentially provided with a plurality of micro-conical fiber bragg gratings, the micro-conical fiber bragg gratings are arranged in a gas chamber, and the gas sensitive material-based micro-conical fiber bragg grating gas sensing device is arranged in the gas chamber. The other end of the single-mode fiber is connected with a spectrum analyzer, and the other end of the spectrum analyzer is connected with a computer. When the device is used, support of large-size equipment is not needed, carrying and use operation are convenient, and due to the fact that the structure of the micro-conical fiber bragg grating is highly sensitive to the surrounding environment, such as strain, bending, refractive index, temperature and humidity; the micro conical fiber bragg grating has quick response to the change of the refractive index of the coating and the stress change caused by the volume swelling of the coating. Functions of the micro conical fiber bragg grating, multi-component gas, mechanical synthesis and the like are integrated into a whole, and the device has the excellent characteristics of miniaturization, strong distinguishing capability and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber gas sensing detection, in particular to a micro-tapered optical fiber grating gas sensing device based on gas-sensitive materials and a use method thereof. Background Art

[0002] The astonishing industrial development in recent decades has exacerbated the problem of air pollution, as the levels of trace gases continue to increase, especially for the environment and human health. The concentration of carbon dioxide (CO2) in daily life is an important indicator of indoor air cleanliness. In view of the rapid growth of the natural gas economy, the main component of natural gas is methane, which is a colorless, highly flammable and explosive gas with an explosion limit of 4.3%-16.2%, and is very easy to explode in the air; therefore, the safe use of CH4 gas and the detection of CH4 leaks have become very important, and people need better technology to monitor CH4 emissions at every stage of the natural gas infrastructure. Therefore, the safe use of CO2 gas and the detection of CH4 leaks have become very important.

[0003] In recent years, sensitive materials based on changing the refractive index or changing the grating period have attracted more and more attention. Gas sensing technology mainly relies on the changes in physical and chemical properties when gases interact with other materials such as metal oxides and polymer composites. The coating of sensitive materials on fiber gratings will change the refractive index of the fiber core, ultimately resulting in a shift in the coupled resonance wavelength. The sensitive materials of fiber grating coatings mainly include metals, inorganic materials and polymers. The micro-tapered fiber grating (MT-FG) used in the present invention is of very high quality, with a grating extinction ratio of 30dB and a loss of less than 1dB, and has excellent sensitivity to changes in its own stress. The method for making the micro-tapered fiber grating has many advantages such as simple implementation, high grating repeatability, good controllability in manufacturing, and high grating quality. Fiber gas sensors are conducive to the smooth adsorption of the sensing surface, resulting in an effective interaction between the sensing surface and the gas species, and subsequently generating effective sensing signals to provide improved analytical performance. In view of this, fiber optic sensors have great potential in commercial installations for sensing and monitoring environments contaminated by many gases.

[0004] Existing technology uses different microstructured optical fibers to measure changes in the properties of light, and it is possible to infer the light signal sensed by the optical fiber sensor, thereby realizing the monitoring of gas concentration. However, evanescent wave optical fiber gas sensors and infrared spectrometers are relatively expensive, pressure can easily affect the vibration state of gas molecules, and absorption peaks easily overlap, making it difficult to detect multiple gas concentrations. Their manufacturing cost is relatively high, the optical structure is complex, and they are easily affected by changes in environmental parameters such as temperature and humidity, which can easily cause large errors. Summary of the invention

[0005] The purpose of the present invention is to provide a micro-tapered fiber grating gas sensing device based on gas-sensitive materials to solve the problems mentioned in the above background technology that the evanescent wave fiber optic gas sensor and infrared spectrometer are relatively expensive, the pressure can easily affect the vibration state of gas molecules, and the absorption peaks are easy to overlap, making it difficult to detect multiple gas concentrations, the manufacturing cost is relatively high, the optical structure is complex, and it is easily affected by changes in environmental parameters such as temperature and humidity, which can easily cause large errors.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive materials comprises a broadband light source, a generating end of the broadband light source is connected to a single-mode optical fiber, a plurality of micro-tapered fiber Bragg gratings are sequentially arranged on the outside of the single-mode optical fiber, the micro-tapered fiber Bragg gratings are arranged inside a gas chamber, the other end of the single-mode optical fiber is connected to a spectrum analyzer, and the other end of the spectrum analyzer is connected to a computer;

[0008] The micro-tapered fiber grating includes a second micro-tapered fiber grating, a third micro-tapered fiber grating and a first micro-tapered fiber grating, and the second micro-tapered fiber grating, the third micro-tapered fiber grating and the first micro-tapered fiber grating are all arranged inside the air chamber; and the surfaces of the second micro-tapered fiber grating, the third micro-tapered fiber grating and the first micro-tapered fiber grating are respectively coated with different gas-sensitive materials, coated with the same gas-sensitive material or not coated with gas-sensitive materials.

[0009] Further preferably, the air chamber includes an upper and lower part, and when an air cavity is provided inside the air chamber, an air inlet pipe and an air outlet pipe are provided at both ends of the upper half of the air cavity, a plurality of grooves are evenly provided inside the upper half of the air cavity, a plurality of protrusions are evenly provided inside the lower half of the air cavity, the grooves and protrusions are cooperatively connected, and an optical fiber stabilizer is also provided inside the air cavity.

[0010] Further preferably, the air chamber includes an upper and lower part, and when a plurality of air cavities are arranged inside the air chamber, an air inlet pipe and an air outlet pipe are respectively arranged at both ends of the upper half of each air cavity, a plurality of grooves are evenly arranged inside the upper half of each air cavity, a plurality of protrusions are evenly arranged inside the lower half of each air cavity, the grooves and protrusions are cooperatively connected, and an optical fiber stabilizer is also arranged inside each air cavity.

[0011] Further preferably, the optical fiber stabilizer comprises a through hole for connecting the single-mode optical fiber through, and a reserved groove is arranged on the top of the through hole.

[0012] Further preferably, a test hole is also provided through the surface of the air chamber.

[0013] Further preferably, optical fiber supporting grooves are provided at the connection between the two ends of the air chamber and the single-mode optical fiber, and optical fiber protective sleeves are provided at the connection between the single-mode optical fiber and the optical fiber supporting grooves, and the surfaces of the optical fiber supporting grooves and the optical fiber protective sleeves are evenly coated with silicone rubber.

[0014] Further preferably, the upper and lower parts of the air cavity and the groove and the protrusion are bonded together by silicone rubber.

[0015] The present invention also provides a technical solution, a method for using a micro-tapered fiber Bragg grating gas sensing device based on a gas-sensitive material, comprising the following steps:

[0016] Input the gas to be tested into the air chamber through the air inlet pipe to ensure that the gas to be tested fills the entire air chamber;

[0017] A broadband light source sends an optical signal through a single-mode optical fiber;

[0018] The optical signal then passes through the micro-tapered fiber gratings coated with different gas-sensitive materials, coated with the same gas-sensitive material, or not coated with gas-sensitive materials in the gas chamber in sequence;

[0019] The optical signal is finally transmitted by single-mode optical fiber to the spectrum analyzer and computer for data processing.

[0020] Further preferably, when the optical signal passes through the micro-conical fiber grating coated with different gas-sensitive materials, coated with the same gas-sensitive material or not coated with gas-sensitive material inside the air chamber in turn, the test holes on the surface of the air chamber serve as passages for the temperature sensor, humidity sensor and pressure sensor, and the air cavity is bonded with silicone rubber, and the remaining pores are sealed with glue.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses a micro-conical fiber Bragg grating with higher sensitivity to environmental variables such as stress, torsion, and bending, which can achieve selective gas concentration measurement at the ppm level and is universal for gases that absorb in the near-infrared band. When in use, the device of the present invention does not require the support of large-volume equipment and is easy to carry and operate. Since the structure of the micro-conical fiber Bragg grating is highly sensitive to the surrounding environment, such as strain, bending, refractive index, temperature, and humidity, the micro-conical fiber Bragg grating has a rapid response to changes in the refractive index of the coating and stress changes caused by the volume swelling of the coating. The functions of micro-conical fiber Bragg grating, multi-component gas, and mechanical synthesis are integrated into one, aiming to measure the concentration of greenhouse gases. It has excellent characteristics such as miniaturization, strong differentiation ability, and rapid response. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the overall structure of a micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive materials in Example 1 of the present invention;

[0024] Figure 2 It is a schematic diagram of the internal structure of the air chamber of the present invention;

[0025] Figure 3 It is a schematic diagram of the connection structure between the air chamber and the optical fiber protective cover of the present invention;

[0026] Figure 4 It is a schematic diagram of the structure of the optical fiber stabilizer of the present invention;

[0027] Figure 5 It is a partial schematic diagram of the micro-tapered fiber Bragg grating of the present invention;

[0028] Figure 6 Schematic diagram of a micro-tapered fiber Bragg grating in Example 1 of the present invention;

[0029] Figure 7 Schematic diagram of the overall structure of a micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive materials in Example 2 of the present invention;

[0030] In the figure: 1. broadband light source; 2. single-mode optical fiber; 3. air chamber; 4. first micro-conical fiber Bragg grating; 5. air inlet pipe; 6. air outlet pipe; 7. second micro-conical fiber Bragg grating; 8. third micro-conical fiber Bragg grating; 9. spectrum analyzer; 10. computer; 12. optical fiber supporting groove; 13. air cavity; 14. protrusion; 15. groove; 16. test hole; 17. optical fiber protective cover; 18. optical fiber stabilizer; 18-1. insertion hole; 18-2. reserved groove. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] See also Figure 1-Figure 7 , the present invention provides a technical solution:

[0033] A micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive materials comprises a broadband light source 1, a generating end of the broadband light source 1 is connected to a single-mode optical fiber 2, a plurality of micro-tapered fiber Bragg gratings are sequentially arranged on the outside of the single-mode optical fiber 2, the micro-tapered fiber Bragg gratings are arranged inside a gas chamber 3, the other end of the single-mode optical fiber 2 is connected to a spectrum analyzer 9, and the other end of the spectrum analyzer 9 is connected to a computer 10;

[0034] The micro-tapered fiber grating includes a second micro-tapered fiber grating 7, a third micro-tapered fiber grating 8 and a first micro-tapered fiber grating 4, and the second micro-tapered fiber grating 7, the third micro-tapered fiber grating 8 and the first micro-tapered fiber grating 4 are all arranged inside the air chamber 3; and the surfaces of the second micro-tapered fiber grating 7, the third micro-tapered fiber grating 8 and the first micro-tapered fiber grating 4 are respectively coated with different gas-sensitive materials, coated with the same gas-sensitive material or not coated with gas-sensitive materials.

[0035] In the present invention, the air chamber 3 is composed of an upper and lower part. When an air cavity 13 is provided inside the air chamber 3, an air inlet pipe 5 and an air outlet pipe 6 are provided at both ends of the upper half of the air cavity 13, and a plurality of grooves 15 are evenly provided inside the upper half of the air cavity 13. A plurality of protrusions 14 are evenly provided inside the lower half of the air cavity 13. The grooves 15 and the protrusions 14 are connected with each other in a coordinated manner. An optical fiber stabilizer 18 is also provided inside the air cavity 13.

[0036] In the present invention, the air chamber 3 is composed of an upper and lower part. When a plurality of air cavities 13 are arranged inside the air chamber 3, an air inlet pipe 5 and an air outlet pipe 6 are arranged at both ends of the upper half of each air cavity 13, a plurality of grooves 15 are evenly arranged inside the upper half of each air cavity 13, a plurality of protrusions 14 are evenly arranged inside the lower half of each air cavity 13, the grooves 15 and the protrusions 14 are matched and connected with each other, and an optical fiber stabilizer 18 is also arranged inside each air cavity 13.

[0037] In the present invention, the optical fiber stabilizer 18 includes a through hole 18-1 for the single-mode optical fiber 2 to penetrate and connect, and a reserved groove 18-2 is arranged on the top of the through hole 18-1. The positions of the air inlet pipe 5 and the air outlet pipe 6 and the placement of the air chamber 3 can be reasonably adjusted according to the experimental environment. The length of the air chamber 3 is related to the length of the micro-conical fiber grating used. Generally, the length of the micro-conical fiber grating is about 30-50mm, and the distance between the cascaded micro-conical fiber gratings is about 20mm-80mm. The optical fiber stabilizer 18 is 20-25mm away from the end of the micro-conical fiber grating. The two ends of the air chamber 3 are connected to the single-mode optical fiber 2 with optical fiber support grooves 12, and the single-mode optical fiber 2 is connected to the optical fiber support groove 12. The optical fiber protective cover 17 is also provided at the connection. The surface of the optical fiber support groove 12 and the optical fiber protective cover 17 is evenly coated with silicone rubber. In order to cope with the influence of environmental disturbance on the micro-conical fiber Bragg grating, a fiber protective cover 17, a fiber supporting groove 12 and an optical fiber stabilizer 18 are designed to stabilize the single-mode optical fiber 2 during use and reduce the vibration caused by air flow. The single-mode optical fiber 2 can be placed in the insertion hole 18-1 of the optical fiber stabilizer 18, and the reserved groove 18-2 is designed to avoid radial jitter of the single-mode optical fiber 2 caused by airflow during use. Since the air chamber 3 is detachable, it is easy to select a single or multiple optical fiber stabilizers 18 to be placed in the air cavity 13 according to the different types of micro-conical fiber Bragg gratings used. The insertion hole 18-1 with a special shape and size can perfectly adapt to the optical fiber stabilizer 18 of the gas monitoring device. Its uniform texture enables it to effectively support and stabilize the micro-conical fiber Bragg grating, and it can remain stable even when the gas monitoring device is subjected to special movement and rotation.

[0038] In the present invention, the surface of the air chamber 3 is also provided with a test hole 16. The entire air chamber 3 is made of acrylic material and does not involve absorption of the gas to be tested, thereby ensuring the accuracy and reliability of monitoring.

[0039] In the present invention, the upper and lower parts of the air cavity 3 and the groove 15 and the protrusion 14 are bonded together by silicone rubber.

[0040] The present invention uses fiber Bragg gratings with higher sensitivity to environmental variables such as stress, torsion, and bending, which can achieve selective gas concentration measurement at the ppm level and is universal for gases that absorb in the near-infrared band. The principle is as follows:

[0041] LPFG (Long Period Fiber Grating) has a large grating period in both the core and cladding modes. When light reaches the grating, the basic core mode of the LPFG couples with the discrete forward propagating cladding mode, and a portion of the wavelength propagates out of the fiber. A series of attenuation bands will be generated in the transmission spectrum at the coupling wavelength. The resonant wavelength of the mth cladding mode that meets the phase matching condition is:

[0042]

[0043] in is the resonant wavelength, is the effective refractive index of the fiber core, is the effective refractive index of the m-th order cladding mode, and Λ is the period of the refractive index modulation of the micro-tapered fiber grating.

[0044] The center wavelength of the resonance band is sensitive to changes in the surrounding environment, such as temperature or external refractive index. Although the LP0m cladding modes are based on the weak guiding approximation of the cladding mode, they allow relatively accurate and fast modeling of the phase matching curve and transmission spectrum of the LPFG (compared to the HEnm mode). This approximation is not applicable to the case where there is a large RI difference between the core and the cladding, that is, the case of strong guidance in the optical fiber. It can be seen that the refractive index of the surrounding medium determines the position of the resonance peak in the transmission spectrum. Therefore, when the presence of the measured gas triggers the sensitive material to exhibit volume expansion, the generated stress is transmitted to the grating, resulting in changes in the grating period and refractive index, or the refractive index of the surrounding medium changes, the center wavelength of the resonance band will shift, thereby realizing the sensing function. Common CO2 polymer coatings are as follows: polystyrene, polyformamide, polyethersulfone, polypyrrole, etc.; CH4 polymer coatings are: metal organic framework (ZIF-8), graphene oxide, cryptophane A, and the polymer coating film thickness is about 10-150μm.

[0045] The fiber grating of the present invention can be selected from a variety of sources, such as Bragg grating, tilted grating, long period fiber grating, the gas chamber 3 can be selected to be contained in one grating or multiple gratings, and the gas sensitive material can be selected according to the experimental purpose.

[0046] The present invention also provides a technical solution, a method for using a micro-tapered fiber Bragg grating gas sensing device based on a gas-sensitive material, characterized in that it comprises the following steps:

[0047] The gas to be tested is input into the gas chamber 3 through the air inlet pipe 5. The gas to be tested includes nitrogen, carbon dioxide, and methane standard gas cylinders. These standard gases enter the gas chamber 3 through the air inlet pipe 5 after being balanced with N2, ensuring that the gas to be tested fills the entire gas chamber 3;

[0048] Broadband light source 1 emits an optical signal through single-mode optical fiber 2;

[0049] The optical signal then passes through the micro-tapered fiber gratings coated with different gas-sensitive materials, coated with the same gas-sensitive material, or not coated with gas-sensitive materials inside the gas chamber 3 in sequence;

[0050] The optical signal is finally transmitted by the single-mode optical fiber 2 to the spectrum analyzer 9 and the computer 10 for data processing. The spectrum analyzer 9 shows that the spectrum of each micro-tapered fiber grating also has the change of the central wavelength of the corresponding resonance band to achieve the purpose of gas detection.

[0051] In the present invention, when the optical signal passes through the micro-tapered fiber grating coated with different gas-sensitive materials, coated with the same gas-sensitive material or not coated with gas-sensitive material inside the air chamber 3 in turn, the test hole 16 on the surface of the air chamber 3 serves as a passage for the temperature sensor, humidity sensor and pressure sensor, and the air cavity 3 is bonded with silicone rubber, and the remaining pores are sealed with glue.

[0052] Example 1: Figure 1-Figure 6 As shown, a self-made micro-cone fiber Bragg grating with a diameter of 62.5 μm, a tapered waist of 50 μm and a refractive index modulation period of 400 μm is used. The second micro-cone fiber Bragg grating 7 coated with CO2 gas-sensitive material and the third micro-cone fiber Bragg grating 8 coated with CH4 gas-sensitive material are coated with polystyrene (molecular weight 280,000 g / mol) and graphene oxide as gas-sensitive materials for CO2 and CH4 respectively by dip coating technology.

[0053] After the micro-cone fiber Bragg grating is coated with the material and left to stand for 12 hours, the micro-cone fiber Bragg grating is enclosed in an air chamber 3 and the optical fiber stabilizer 18 is used to securely fix the micro-cone fiber Bragg grating on both sides. In order to reduce the impact of gas flow on experimental measurements, the overall design of the air chamber 3 ensures that the micro-cone fiber Bragg grating can be stretched freely in the axial direction. A gas passage is established to connect the gas cylinder and the air cavity 13, and the gas flow is accurately controlled by the gas flowmeter. The test hole 16 located in the center of the air cavity 13 and running through the surface of the air chamber 3 is convenient for monitoring the temperature and humidity levels in the chamber through the temperature and humidity sensor probe. The gases used in the experiment are nitrogen, carbon dioxide, and methane standard gas cylinders. These standard gases enter the air chamber 3 through the air inlet pipe 5 after being balanced with N2. In this embodiment, the side of the protrusion 14 is glued and bonded to the pores of the groove 15, and the optical fiber protection cover 17 and the optical fiber supporting groove 12 are coated with silicone rubber. Depending on the specific experimental conditions, whether the air chamber 3 is selected to reserve a test hole 16 is determined. In this embodiment, test holes 16 are cut on both sides of the air cavity 3 by a CNC machine tool as passages for sensors such as temperature, humidity, and pressure, and the air cavity is bonded with silicone rubber. The remaining pores are sealed with glue to ensure airtightness during the experiment.

[0054] like Figure 1As shown, it is a schematic diagram of the structure for detecting a mixed state of CO2 and CH4 gases under a specific environment. The gas chamber 3 respectively stores a second micro-conical fiber grating 7 coated with a CO2 gas-sensitive material, a third micro-conical fiber grating 8 coated with a CH4 gas-sensitive material, and a first micro-conical fiber grating 4 not coated with a gas-sensitive material. After the measured gas is introduced into each gas chamber 3, through the change of gas concentration, the spectrum analyzer 9 displays that the spectrum of each micro-conical fiber grating also has the change of the corresponding resonance band center wavelength to achieve the purpose of gas detection.

[0055] Embodiment 2: Figure 7 This is another structural diagram provided by Example 2 of the present invention. The method of use is the same as that of Example 1.

[0056] The difference is: the micro-cone fiber Bragg grating in this embodiment needs to be fixed on the shaft of the rotating motor before use, and the other end needs to be wrapped with a weight to maintain vertical stability. The motor speed is set to 300r / min; the polyethersulfone solution (49000g / mol) is injected into the MT-LPFG using a syringe, and the translation stage of the injection device is adjusted to keep it 15 cm away from the micro-cone fiber Bragg grating; the electric field strength is set to 18.5kV, and the forward speed of the injection device is set to 0.0015mm / s. After starting the rotating motor and ensuring that the micro-cone fiber Bragg grating rotates stably, the polyethersulfone solution is electrospun into nanofibers and wrapped in the grating area, and the metal organic framework material (ZIF-8) is grown at another grating area of ​​the micro-cone fiber Bragg grating using a layer-by-layer technique.

[0057] Since the micro-cone fiber Bragg grating used is more suitable for multiple separate air chambers 3, the length of the air cavity 13 is increased to 30 mm. The sensor can use the method in Example 1 to detect the presence of a single concentration of gas in different environments.

[0058] The air chamber 3 in this embodiment is more suitable for simultaneous detection of multiple mixed gases. The air chamber 3 is processed by a CNC machine tool according to the mechanical design, and is made of polymethyl methacrylate material. The length can be selected according to the type of gas to be tested. The design of the air inlet pipe 5 and the air outlet pipe 6 allows the gas to be tested to be completely filled in the air chamber 3. When different gases are introduced, the micro-conical fiber grating area can fully interact with the gas to be tested.

[0059] The sensor integrates micro-conical fiber Bragg grating, multi-component gas and mechanical synthesis functions to measure greenhouse gas concentrations. It has excellent characteristics such as miniaturization, strong discrimination ability and fast response.

[0060] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0061] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A micro-tapered fiber Bragg grating gas sensing device based on a gas-sensitive material, comprising a broadband light source (1), characterized in that: The generating end of the broadband light source (1) is connected to a single-mode optical fiber (2), a plurality of micro-conical optical fiber gratings are sequentially arranged outside the single-mode optical fiber (2), and the micro-conical optical fiber gratings are arranged inside the air chamber (3); the other end of the single-mode optical fiber (2) is connected to a spectrum analyzer (9), and the other end of the spectrum analyzer (9) is connected to a computer (10); The micro-tapered fiber Bragg grating comprises a second micro-tapered fiber Bragg grating (7), a third micro-tapered fiber Bragg grating (8) and a first micro-tapered fiber Bragg grating (4), and the second micro-tapered fiber Bragg grating (7), the third micro-tapered fiber Bragg grating (8) and the first micro-tapered fiber Bragg grating (4) are all arranged inside the gas chamber (3); and the surfaces of the second micro-tapered fiber Bragg grating (7), the third micro-tapered fiber Bragg grating (8) and the first micro-tapered fiber Bragg grating (4) are respectively coated with different gas-sensitive materials, coated with the same gas-sensitive material or not coated with gas-sensitive materials.

2. The micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive materials according to claim 1, characterized in that: The air chamber (3) is composed of an upper and lower part. When an air cavity (13) is arranged inside the air chamber (3), an air inlet pipe (5) and an air outlet pipe (6) are arranged at both ends of the upper half of the air cavity (13), a plurality of grooves (15) are evenly arranged inside the upper half of the air cavity (13), and a plurality of protrusions (14) are evenly arranged inside the lower half of the air cavity (13). The grooves (15) and the protrusions (14) are connected to each other in a coordinated manner. An optical fiber stabilizer (18) is also arranged inside the air cavity (13).

3. The micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive material according to claim 1, characterized in that: The air chamber (3) is composed of an upper and lower part. When a plurality of air cavities (13) are arranged inside the air chamber (3), an air inlet pipe (5) and an air outlet pipe (6) are arranged at both ends of the upper half of each air cavity (13), a plurality of grooves (15) are evenly arranged inside the upper half of each air cavity (13), and a plurality of protrusions (14) are evenly arranged inside the lower half of each air cavity (13). The grooves (15) and the protrusions (14) are connected to each other in a coordinated manner. An optical fiber stabilizer (18) is also arranged inside each air cavity (13).

4. The micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive material according to claim 2 or 3, characterized in that: The optical fiber stabilizer (18) comprises a through hole (18-1) for connecting the single-mode optical fiber (2) through, and a reserved groove (18-2) is arranged at the top of the through hole (18-1).

5. The micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive material according to claim 2 or 3, characterized in that: A testing hole (16) is also provided through the surface of the air chamber (3).

6. The micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive materials according to claim 1, characterized in that: Optical fiber support grooves (12) are also provided at the connection points between the two ends of the air chamber (3) and the single-mode optical fiber (2), and optical fiber protection sleeves (17) are also provided at the connection points between the single-mode optical fiber (2) and the optical fiber support grooves (12), and the surfaces of the optical fiber support grooves (12) and the optical fiber protection sleeves (17) are evenly coated with silicone rubber.

7. The micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive material according to claim 2 or 3, characterized in that: The upper and lower parts of the air cavity (3) and the groove (15) and the protrusion (14) are bonded together by silicone rubber.

8. The method for using the micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive materials according to any one of claims 1 to 6, characterized in that: The following steps are involved: Inputting the gas to be tested into the interior of the gas chamber (3) through the gas inlet pipe (5) to ensure that the gas to be tested fills the entire gas chamber (3); A broadband light source (1) emits an optical signal through a single-mode optical fiber (2); The optical signal then passes through the micro-tapered fiber gratings coated with different gas-sensitive materials, coated with the same gas-sensitive material, or not coated with a gas-sensitive material inside the gas chamber (3) in sequence; The optical signal is finally transmitted by the single-mode optical fiber (2) to the optical spectrum analyzer (9) and the computer (10) for data processing.

9. The method for using the micro-tapered fiber Bragg grating gas sensing device based on gas-sensitive materials according to claim 8, characterized in that: When the optical signal passes through the micro-tapered optical fiber gratings coated with different gas-sensitive materials, coated with the same gas-sensitive material, or not coated with gas-sensitive materials in the air chamber (3), the test hole (16) on the surface of the air chamber (3) serves as a passage for the temperature sensor, the humidity sensor, and the pressure sensor, and the air cavity (3) is bonded with silicone rubber, and the remaining pores are sealed with glue.

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