Tapered optical fiber hydrogen sensor and preparation method thereof

Abstract

The invention provides a tapering optical fiber hydrogen sensor and a preparation method thereof, and belongs to the field of hydrogen sensors. The sensing part is tightly arranged outside the tapering section in a sleeving manner; the light source inputs optical signals to the optical fiber; the spectrograph measures the characteristic peak position of the spectrum in the optical fiber; the sensing part comprises three layers of film structures from inside to outside, and the excitation layer excites the surface of the optical fiber to generate a plasma resonance effect; the reaction layer is made of a gas sensitive material and reacts with hydrogen; and the catalytic layer catalyzes the gas sensitive material to react with hydrogen. The optical fiber sensor is prepared by adopting a tapering method, the sensitivity of the sensor is greatly improved, a tungsten oxide and gold co-sputtering material is adopted as a gas-sensitive material, and compared with the gas-sensitive material only using tungsten oxide, the response time and the recovery time are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen sensors, and in particular to a tapered optical fiber hydrogen sensor and a preparation method thereof. Background Art

[0002] Hydrogen is one of the characteristic gases produced by battery thermal runaway. Its large amount of production in the battery may indicate the occurrence of thermal runaway. Therefore, detecting the hydrogen produced by the battery is a feasible method for early warning of battery thermal runaway. The types of fiber optic hydrogen sensors currently being studied include fiber grating type, interference type, evanescent field type, and surface plasmon resonance type.

[0003] However, these types of sensors still have sensitivity issues. For example, the sensitivity of fiber Bragg grating and interferometric sensors is usually in the range of hundreds of picometers to nanometers per percent hydrogen concentration, and the sensitivity of surface plasmon resonance sensors is usually in the range of several nanometers per percent hydrogen concentration, but the sensitivity is still relatively low. Summary of the invention

[0004] In view of this, the present invention proposes a tapered optical fiber hydrogen sensor and a preparation method thereof.

[0005] The technical solution of the present invention is implemented as follows: the present invention provides a tapered optical fiber hydrogen sensor, comprising an optical fiber, a tapered section is arranged in the middle of the optical fiber; a sensing part, which is tightly sleeved outside the tapered section; a light source, which is connected to one end of the optical fiber and inputs an optical signal into the optical fiber; a spectrometer, which is connected to the other end of the optical fiber and measures the characteristic peak position of the spectrum in the optical fiber; wherein the sensing part includes three layers of thin film structure from the inside to the outside, namely, an excitation layer, which excites the surface of the optical fiber to produce a plasma resonance effect; a reaction layer, which is made of a gas-sensitive material and reacts with hydrogen; and a catalytic layer, which catalyzes the reaction of the gas-sensitive material with hydrogen.

[0006] On the basis of the above technical scheme, preferably, the excitation layer is formed by single-element gold plating; the reaction layer is formed by co-sputtering tungsten oxide and single-element gold as gas-sensitive materials; and the catalytic layer is formed by single-element platinum plating.

[0007] More preferably, the thickness of the reaction layer is 15-60 nm.

[0008] More preferably, the thickness of the catalytic layer is no more than 1 nm.

[0009] More preferably, the mass percentage of gold element in the reaction layer is 9.4-45%.

[0010] On the basis of the above technical solution, preferably, the diameter of the tapered section is no more than 5 μm.

[0011] In the second aspect, the present invention also provides a method for preparing a tapered optical fiber hydrogen sensor, which is used to prepare the above-mentioned tapered optical fiber hydrogen sensor, including the following steps: step one, forming a tapered section on the optical fiber by melt taper; step two, coating the tapered section in sequence from the inside to the outside by magnetron sputtering to obtain an excitation layer, a reaction layer and a catalytic layer; step three, connecting the two ends of the optical fiber to a light source and a spectrometer respectively.

[0012] Based on the above technical solution, preferably, in step 2, a reaction layer is formed by simultaneously magnetron sputtering a gold target and a tungsten target, wherein the deposition rate of gold is

[0013] On the basis of the above technical solution, preferably, in step 2, after the excitation layer is plated on the surface of the tapered section, the two ends of the optical fiber plated only with a gold film are respectively connected to a light source and a spectrometer, the light source is turned on, and the spectrometer is used to detect and record the spectral information at this time as a reference spectrum.

[0014] In the third aspect, the present invention also provides a method for using a tapered optical fiber hydrogen sensor, which is a tapered optical fiber hydrogen sensor made by the above-mentioned method for preparing a tapered optical fiber hydrogen sensor, comprising the following steps: step one, placing the sensor in an environment to be tested; step two, keeping the light source turned off, using a spectrometer to detect and record the spectral information at this time as a background spectrum; step three, turning on the light source switch, using a spectrometer to detect and record the spectral information at this time as a sample spectrum, and calculating the transmission spectrum of the sensor by combining the sample spectrum, the background spectrum and the reference spectrum.

[0015] Compared with the prior art, the tapered optical fiber hydrogen sensor and its preparation method of the present invention have the following advantages:

[0016] Beneficial effects:

[0017] (1) When the light emitted by the wide-spectrum light source of the present invention passes through the tapered section of the sensor, the presence of the gold film will produce a surface plasmon resonance effect, causing a characteristic absorption peak to appear in the sensor's transmission spectrum. The refractive index of the external material is calculated by the position of the characteristic peak, thereby accurately detecting the hydrogen concentration of the environment. The present invention uses a tapered method to prepare an optical fiber sensor, which greatly improves the sensitivity of the sensor. The co-sputtered material of tungsten oxide and gold is used as a gas-sensitive material, which greatly improves the response and recovery time compared to using only tungsten oxide as a gas-sensitive material.

[0018] (2) The present invention can adjust the response speed of the sensor in detecting hydrogen by limiting the thickness of the reaction layer and the catalytic layer; the present invention can adjust the shift amplitude of the spectral characteristic peak when the sensor detects hydrogen by limiting the mass percentage of the gold element in the reaction layer, thereby greatly improving the accuracy and sensitivity of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the test examples of the present invention or the technical solutions in the prior art, the drawings required for use in the test examples or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some test examples of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic structural diagram of the tapered optical fiber hydrogen sensor of the present invention;

[0021] Figure 2 A schematic diagram of a tapered portion of the present invention;

[0022] Figure 3 It is a gas response curve diagram of the tapered optical fiber hydrogen sensor of the present invention at a hydrogen concentration of 0.3%.

[0023] In the figure: 1. optical fiber; 11. tapered part; 2. sensing part; 21. excitation layer; 22. reaction layer; 23. catalytic layer; 3. light source; 4. spectrometer; 5. gas chamber to be tested; 6. gas storage tank; 7. gas mixing mechanism. DETAILED DESCRIPTION

[0024] The following will be combined with 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.

[0025] like Figure 1 As shown, combined Figure 2 A tapered optical fiber hydrogen sensor of the present invention comprises an optical fiber 1, a sensing part 2, a light source 3 and a spectrometer 4.

[0026] The optical fiber 1 is a multimode optical fiber with a double-tapered region, and thus a tapered section 11 is provided in the middle thereof. The presence of the tapered section 11 increases the surface area of ​​the optical fiber 1, thereby enhancing the interaction between light and surface plasmons, and helps to improve the sensitivity of the sensor.

[0027] The sensing part 2 is tightly sleeved outside the tapered section 11. The sensing part 2 includes a three-layer thin film structure from the inside to the outside, and the three thin films are an excitation layer 21, a reaction layer 22 and a catalytic layer 23. The excitation layer 21 excites the surface of the optical fiber 1 to produce a plasma resonance effect; the reaction layer 22 is made of a gas-sensitive material and reacts with hydrogen; and the catalytic layer 23 catalyzes the gas-sensitive material to react with hydrogen.

[0028] The light source 3 is a broad-spectrum light source, specifically a laser transmitter or a photoelectric converter, which is connected to one end of the optical fiber 1 and inputs an optical signal to the optical fiber 1 .

[0029] The spectrometer 4 is connected to the other end of the optical fiber 1 and measures the characteristic peak position of the spectrum in the optical fiber 1. The end of the optical fiber 1 is fused with the light source 3 or the spectrometer 4.

[0030] The principle of the present invention is: when the light emitted by the wide-spectrum light source 5 passes through the tapered section 11 of the optical fiber 1, the optical fiber 1 will produce a surface plasmon resonance effect due to the existence of the excitation layer 21, so a characteristic absorption peak will appear in the transmission spectrum of the sensor, and the position of the characteristic peak is related to the refractive index of the external material, and the external material can be hydrogen in the external environment. When the gas-sensitive material of the reaction layer 22 reacts with hydrogen under the catalytic action of the catalytic layer 23 and produces a change in the refractive index, the position of the characteristic peak will also change accordingly, so that the concentration of the gas in the external environment and its change can be accurately detected.

[0031] exist Figure 2 In a preferred test example shown, the excitation layer 21 is formed by gold plating; the reaction layer 22 is formed by co-sputtering tungsten oxide and gold as gas-sensitive materials, and the catalytic layer 23 is formed by platinum plating. The excitation layer 21 is a gold film, which is used to excite the plasma resonance effect on the surface of the tapered optical fiber, so that a characteristic peak that can detect the change in the refractive index of the outer layer appears in the transmission spectrum of the sensor; the reaction layer 22 is a tungsten oxide and gold co-sputtering layer, which acts as a gas-sensitive material to react with hydrogen and produce a change in the refractive index; the catalytic layer 23 is a platinum film, and only under the condition of the presence of the platinum film can hydrogen be catalyzed to react with the co-sputtering layer of tungsten oxide and gold, so it plays a catalytic role.

[0032] exist Figure 2 In a preferred test example shown, the thickness of the reaction layer 22 is 15-60nm. The thickness of the reaction layer 22 directly affects the reaction ability of the gas-sensitive material: a reaction layer 22 that is too thin may not be enough to provide a sufficient reaction area, resulting in insufficient contact between the gas and the material, reducing the sensitivity of the sensor to hydrogen, and may even cause incomplete reaction; a reaction layer 22 that is too thick may cause the gas to be unable to diffuse effectively in the reaction layer, and the reaction becomes slow or uneven, affecting the response time and stability of the sensor. An appropriate thickness of the reaction layer 22 can improve the gas detection sensitivity of the sensor. In particular, in the range of 15-60nm, the reaction layer 22 can minimize the impact of signal noise while responding to changes in gas concentration, thereby improving the selectivity of the sensor. In addition, this thickness can also optimize the changes in the spectral peak position during the reaction with hydrogen, so that changes in gas concentration can be accurately and clearly detected.

[0033] In addition, the thickness of the reaction layer 22 needs to be considered together with the catalyst layer 23 and the excitation layer 21. The catalyst layer 23 helps to accelerate the reaction of hydrogen with the reaction layer, and the excitation layer 21 improves the response sensitivity of the sensor by providing a surface plasmon resonance (SPR) effect. Therefore, the thickness of the reaction layer 22 can be coordinated with the thickness of other layers to jointly optimize the working performance of the entire sensor and avoid affecting the efficiency and stability of the sensor due to mismatched layer thickness.

[0034] exist Figure 2 In a preferred test example shown, the thickness of the catalyst layer 23 is not greater than 1 nm. A thin catalyst layer 23 can maintain a high density of catalytic active sites and maximize the catalytic reaction surface area, thereby more effectively catalyzing the reaction of hydrogen; while a catalyst layer 23 that is too thick will result in unnecessary additional thickness, which may affect the transmission of optical signals, especially in sensors based on surface plasmon resonance (SPR) or other optical principles. A catalyst layer 23 that is too thick will cause changes in the light propagation mode, reducing the sensitivity and response speed of the sensor. Therefore, controlling the thickness of the catalyst layer 23 can effectively avoid such unnecessary optical interference.

[0035] exist Figure 2 In a preferred test example shown, the mass percentage of gold in the reaction layer 22 is 9.4-45%. The mass percentage of gold is directly proportional to the deposition rate of gold in the reaction layer 22 process.

[0036] exist Figure 2 In a preferred test example shown, the diameter of the tapered section 11 is not greater than 5 μm. When the diameter of the tapered section 11 is small, the mode field of the optical fiber 1 will change and concentrate on the surface area of ​​the optical fiber 1, so that the interaction between the surface of the optical fiber 1 and the surrounding gas or liquid medium becomes more significant. For the SPR sensor, the propagation of the surface plasma wave and the reflection and transmission effects of the surface of the optical fiber 1 directly affect the performance of the sensor. A smaller diameter of the optical fiber 1 helps to enhance this interaction, thereby improving the sensitivity and detection accuracy of the sensor.

[0037] like Figure 1 As shown, combined Figure 2 The method for preparing a tapered optical fiber hydrogen sensor of the present invention is used to prepare a tapered optical fiber hydrogen sensor of any of the above test examples, comprising the following steps:

[0038] Step 1, a tapered section 11 is made on the optical fiber 1 by melting and taper. Specifically, a 62.5 / 125 multimode optical fiber is used as the raw material, and the tapered section 11 is made on it by melting and tapering the middle part of the optical fiber 1. Before tapering, remove 20 mm of the coating layer on the optical fiber 1 and clean it with anhydrous ethanol. The stretched length of the optical fiber after tapering is 17000 μm, and the waist diameter is 5 μm. The stretched length of the tapered section 11 in the optical fiber 1 obtained after tapering is 17000 μm, and its waist diameter is 5 μm.

[0039] Step 2: The excitation layer 21, the reaction layer 22 and the catalyst layer 23 are sequentially coated on the tapered section 11 from the inside to the outside by magnetron sputtering.

[0040] Specifically, the excitation layer 21 is firstly plated on the surface of the tapered section 11 by DC magnetron sputtering of a gold target, and the deposition thickness of the excitation layer 21 is 30 nm. During the magnetron sputtering, the technical parameters are set as follows: the deposition temperature is 25°C; the nitrogen flow rate is 14 sccm; the gold deposition rate is

[0041] Then, the reaction layer 22 is plated, which is prepared by magnetron sputtering gold target and tungsten target at the same time, wherein tungsten oxide is RF sputtered and gold is DC sputtered, and the deposition thickness of the reaction layer 22 is 30nm; the technical parameters of the magnetron sputtering are set as follows: the deposition temperature is 25°C; the nitrogen flow rate is 13sccm; the oxygen flow rate is 6.5sccm; the tungsten oxide deposition rate is The gold deposition rate is

[0042] Finally, the catalyst layer 23 is plated, which is prepared by DC sputtering of a platinum target, and the deposition thickness of the catalyst layer 23 is 0.5 nm; the magnetron sputtering technical parameters are set as follows: the deposition temperature is 25°C; the nitrogen flow rate is 14 sccm; the platinum deposition rate is

[0043] Step three, connect the two ends of the optical fiber 1 to the light source 3 and the spectrometer 4 respectively by means of fusion splicing.

[0044] exist Figure 2 In a preferred experimental example shown in FIG. 1 , in step 2, a reaction layer 22 is formed by magnetron sputtering a gold target and a tungsten target simultaneously, wherein the deposition rate of gold is When the deposition rate of tungsten oxide remains unchanged, a change in the deposition rate of gold will change the mass percentage of the gold element in the reaction layer 22, thereby changing the movement amplitude of the spectral characteristic peak when the sensor detects hydrogen, thereby adjusting the sensor accuracy and sensitivity.

[0045] exist Figure 2In a preferred test example shown, in step 2, after the excitation layer 21 is plated on the surface of the tapered section 11, the two ends of the optical fiber 1 plated only with a gold film are respectively connected to the light source 3 and the spectrometer 4, the light source 3 is turned on, and the spectrometer 4 is used to detect and record the spectral information at this time as a reference spectrum.

[0046] like Figure 1 As shown, combined Figure 3 The method for using a tapered optical fiber hydrogen sensor of the present invention is a tapered optical fiber hydrogen sensor made by the method for preparing a tapered optical fiber hydrogen sensor of the above test example, comprising the following steps:

[0047] Step 1, place the sensor in the environment to be tested. Specifically, a simulation experiment can be carried out, in which the tapered section 11 and the sensing part 2 of the sensor are placed in a closed gas chamber 5 to be tested, and the light source 3 and the spectrometer 4 are located in the gas chamber 5 to be tested; multiple gas storage tanks 6 are set, in which hydrogen, nitrogen and air are stored respectively, and the multiple gas storage tanks 6 are connected to the gas mixing mechanism 7, and the gas mixing mechanism 7 is connected to the gas chamber 5 to be tested. Nitrogen and hydrogen are mixed in a certain proportion by the gas mixing mechanism 7 to produce a mixed gas with different concentrations of hydrogen; the mixed gas is passed into the gas chamber 5 to be tested, and the characteristic peak position of the sensor spectrum is measured by the spectrometer 4, so that the hydrogen concentration in the current gas chamber 5 to be tested can be detected.

[0048] In addition, when conducting the test, nitrogen is first introduced into the test chamber 5 for 10,000 seconds; after the transmission spectrum is stabilized, a nitrogen mixture with a concentration of 0.3% is introduced for 1,800 seconds; then air is introduced as a recovery gas for 1,800 seconds.

[0049] Step 2: Keep the light source 3 off, and use the spectrometer 4 to detect and record the spectrum information at this time as the background spectrum.

[0050] Step 3, turn on the light source 3, use the spectrometer 4 to detect and record the spectrum information at this time as the sample spectrum, and calculate the transmission spectrum of the sensor by combining the sample spectrum, background spectrum and reference spectrum. The calculation formula of the transmission spectrum is T = (SD) / (LD), where T is the transmission spectrum of the sensor, S is the sample spectrum of the sensor when the light source is turned on, D is the background spectrum of the sensor, and L is the reference spectrum of the sensor.

[0051] The present invention designs test examples 1 to 10 to simulate the process of detecting hydrogen concentration by a tapered optical fiber hydrogen sensor, and respectively uses the above detection method to measure the spectral characteristic peak position and response time of the sensor of each test example. Specifically, each test example is as follows:

[0052] Test Example 1

[0053] The optical fiber 1 is a 62.5 / 125 multimode optical fiber, the stretched length of the tapered section 11 is 17000 μm, and the waist diameter is 5 μm.

[0054] The deposition thickness of the excitation layer 21 is 30 nm. During magnetron sputtering, the technical parameters are set as follows: the deposition temperature is 25°C; the nitrogen flow rate is 14 sccm; the gold deposition rate is The deposition thickness of the reaction layer 22 is 30 nm. The technical parameters of the magnetron sputtering are set as follows: the deposition temperature is 25°C; the nitrogen flow rate is 13 sccm; the oxygen flow rate is 6.5 sccm; the tungsten oxide deposition rate is The gold deposition rate is At this time, the mass percentage of gold in the reaction layer 22 is 29%. The deposition thickness of the catalyst layer 23 is 0.5 nm; the magnetron sputtering technical parameters are set as follows: the deposition temperature is 25°C; the nitrogen flow rate is 14 sccm; the platinum deposition rate is

[0055] In the simulation test, the hydrogen concentration in the gas chamber 5 to be tested is 0.3%.

[0056] The gas response curve of the sensor is as follows: Figure 3 As shown, it can be seen that the sensor produces a characteristic peak position shift of 7.6nm at a hydrogen concentration of 0.3%, and the response time exceeds 174 seconds. It can be found that in this test example, the spectral characteristic peak of the sensor is very significant, and the response time of the sensor is also very short.

[0057] Test Example 2

[0058] When the reaction layer 22 is plated, the deposition rate of gold is set to The other parameters were kept the same as those in Experimental Example 1, and a reaction layer 22 of tungsten oxide and gold co-sputtered with a low gold content was obtained; at this time, the mass percentage of the gold element in the reaction layer 22 was 9.4%.

[0059] The same test method as in Test Example 1 was used to detect that the sensor produced a 6nm characteristic peak position shift at a hydrogen concentration of 0.3%, and the response time exceeded 1800 seconds.

[0060] Test Example 3

[0061] When the reaction layer 22 is plated, the deposition rate of gold is set to The other parameters were kept the same as those in Experimental Example 1, and a reaction layer 22 of tungsten oxide and gold co-sputtered with a high gold content was obtained; at this time, the mass percentage of the gold element in the reaction layer 22 was 49%.

[0062] The same test method as in Test Example 1 was used to detect that the sensor produced a characteristic peak position shift of 6.9 nm at a hydrogen concentration of 0.3%, and the response time exceeded 1590 seconds.

[0063] By comparing the detection structures of Experimental Examples 2 and 3 with Experimental Example 1, it can be seen that if the mass ratio of the gold element in the reaction layer 22 is too high or too low, the response speed of the sensor will be seriously affected.

[0064] Test Example 4

[0065] When the reaction layer 22 is plated, the deposition thickness of the reaction layer 22 is set to 15 nm, and other parameters are kept consistent with those in Experimental Example 1, thereby obtaining a reaction layer 22 of low thickness co-sputtered tungsten oxide and gold.

[0066] The same test method as in Test Example 1 was used to detect that the sensor produced a 6nm characteristic peak position shift at a hydrogen concentration of 0.3%, and the response time exceeded 1800 seconds.

[0067] Test Example 5

[0068] When the reaction layer 22 is plated, the deposition thickness of the reaction layer 22 is set to 60 nm, and other parameters are kept consistent with those in Experimental Example 1, thereby obtaining a high-thickness reaction layer 22 of co-sputtered tungsten oxide and gold.

[0069] The same test method as in Test Example 1 was used to detect that the sensor produced a 6nm characteristic peak position shift at a hydrogen concentration of 0.3%, and the response time exceeded 1800 seconds.

[0070] By comparing the detection structures of Experimental Examples 4 and 5 with Experimental Example 1, it can be seen that if the deposition thickness of the reaction layer 22 is too high or too low, the response speed of the sensor will be seriously affected.

[0071] Test Example 6

[0072] The catalytic layer 23 is not plated outside the reaction layer 22 , that is, the deposition thickness of the catalytic layer 23 is set to 0 nm, and other parameters remain consistent with those in Experimental Example 1.

[0073] The same test method as in Test Example 1 was used, and it was found that the sensor did not produce a hydrogen response at a hydrogen concentration of 0.3%. It can be seen that if a platinum layer is not plated on the outside of the tungsten oxide and gold co-sputtered layer as a catalyst, the tungsten oxide and gold co-sputtered layer will not react with hydrogen, and thus no spectral characteristic peaks will be generated.

[0074] Test Example 7

[0075] When the catalyst layer 23 is plated, the deposition thickness of the catalyst layer 23 is set to 1 nm, and other parameters are kept consistent with those in Experimental Example 1, thereby obtaining a high-thickness platinum-sputtered catalyst layer 23 .

[0076] The same test method as in Experiment 1 was used, and it was found that the sensor produced a characteristic peak position shift of 8.6nm at a hydrogen concentration of 0.3%, and the response time exceeded 490 seconds. It can be seen that the shift amplitude of the characteristic peak is larger than that of Experiment 1, but the improvement of the sensor's responsiveness is small.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A tapered optical fiber hydrogen sensor, characterized in that: include: An optical fiber (1), wherein a tapered section (11) is provided at the middle thereof; The sensing part (2) is tightly sleeved outside the tapered section (11); A light source (3) connected to one end of the optical fiber (1) and inputting an optical signal into the optical fiber (1); A spectrometer (4) connected to the other end of the optical fiber (1) and measuring the characteristic peak position of the spectrum in the optical fiber (1); The sensing part (2) comprises three layers of thin film structures from the inside to the outside, namely: An excitation layer (21) for exciting the surface of the optical fiber (1) to produce a plasma resonance effect; A reaction layer (22) is made of a gas-sensitive material and reacts with hydrogen; The catalytic layer (23) catalyzes the reaction between the gas-sensitive material and hydrogen.

2. A tapered optical fiber hydrogen sensor according to claim 1, characterized in that: The excitation layer (21) is formed by single-element gold plating; the reaction layer (22) is formed by co-sputtering tungsten oxide and single-element gold as gas-sensitive materials; and the catalytic layer (23) is formed by single-element platinum plating.

3. A tapered optical fiber hydrogen sensor according to claim 2, characterized in that: The reaction layer (22) has a thickness of 15-60 nm.

4. A tapered optical fiber hydrogen sensor according to claim 2, characterized in that: The thickness of the catalytic layer (23) is no greater than 1 nm.

5. The tapered optical fiber hydrogen sensor according to claim 2, characterized in that: The mass percentage of gold element in the reaction layer (22) is 9.4-45%.

6. The tapered optical fiber hydrogen sensor according to claim 1, characterized in that: The diameter of the tapered section (11) is no greater than 5 μm.

7. A method for preparing a tapered optical fiber hydrogen sensor, characterized in that: The method for preparing a tapered optical fiber hydrogen sensor according to any one of claims 2 to 5 comprises the following steps: Step 1, forming a tapered section (11) on the optical fiber (1) by melt tapering; Step 2: coating the tapered section (11) from the inside out in sequence by magnetron sputtering to obtain an excitation layer (21), a reaction layer (22) and a catalytic layer (23); Step three, connecting the two ends of the optical fiber (1) to the light source (3) and the spectrometer (4) respectively.

8. The method for preparing a tapered optical fiber hydrogen sensor according to claim 7, characterized in that: In the step 2, a reaction layer (22) is formed by magnetron sputtering a gold target and a tungsten target simultaneously, wherein the deposition rate of gold is 9. The method for preparing a tapered optical fiber hydrogen sensor according to claim 7, characterized in that: In the second step, after the excitation layer (21) is plated on the surface of the tapered section (11), the two ends of the optical fiber (1) plated only with a gold film are connected to a light source (3) and a spectrometer (4) respectively, the light source (3) is turned on, and the spectrometer (4) is used to detect and record the spectral information at this time as a reference spectrum.

10. A method for using a tapered optical fiber hydrogen sensor, characterized in that: A tapered optical fiber hydrogen sensor manufactured by the method for preparing a tapered optical fiber hydrogen sensor according to claim 9 comprises the following steps: Step 1, placing the sensor into the environment to be tested; Step 2, keeping the light source (3) turned off, using the spectrometer (4) to detect and record the spectrum information at this time as the background spectrum; Step three, turning on the light source (3) switch, using the spectrometer (4) to detect and record the spectral information at this time as the sample spectrum, and combining the sample spectrum, the background spectrum and the reference spectrum to calculate the transmission spectrum of the sensor.

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