Fabry-Perot interference type hydrogen detection device and method

Abstract

The invention discloses a Fabry-Perot interference type hydrogen detection device and method. The Fabry-Perot interference type hydrogen detection device comprises a broadband light source, a spectrograph, an optical fiber coupler, a sensing probe, a test gas chamber and a reference probe, the sensing probe and the reference probe are provided with sensor structures based on an optical fiber Fabry-Perot cavity, and the optical fiber coupler outputs input light emitted by the broadband light source to the sensing probe and the reference probe through a port A, a port B and a port C; light reflected by the optical fiber Fabry-Perot cavities of the sensing probe and the reference probe is output to a spectrograph through a D port, so that an interference spectrum is demodulated; hydrogen to be detected is mixed with air, then enters the test gas chamber through the gas flow rate controller, and is discharged from the outlet; the sensing probe adopts an anodic aluminum oxide / palladium film as a terminal reflector of a Fabry-Perot cavity, and an interference spectrum is detected through a spectrograph to obtain hydrogen concentration information in the environment; the reference probe adopts two single-mode optical fiber end faces to align in a sleeve and form an air Fabry-Perot cavity, and the reference probe only provides a stable reference spectrum to realize a vernier effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber gas detection, and in particular relates to a Fabry-Perot interference type hydrogen detection device and method. Background Art

[0002] The closest technology currently available on the market is fiber-optic hydrogen sensing based on Fabry-Perot interferometry (FPI). For example, palladium-loaded tungsten trioxide (Pd / Wo3) is used as the sensitive material. The FPI is formed by fusion-splicing single-mode fiber, hollow-core fiber, and single-mode fiber. The reaction of hydrogen with Pd / Wo3 releases a large amount of hydrogen, causing the FPI's air cavity length to change. The hydrogen concentration is then demodulated using interferometry. Similarly, a graphene / palladium multilayer film is used as the hydrogen-sensitive material. The FPI is formed by fusion-splicing single-mode fiber to hollow-core fiber and then connecting graphene / palladium. Hydrogen contacts the palladium film, causing it to expand, causing the entire graphene / palladium film to bend inward or outward, ultimately changing the air cavity length. This change can be demodulated using interferometry.

[0003] The existing technology has the following shortcomings:

[0004] Disadvantages of the Pd / Wo3 material: Palladium-loaded tungsten trioxide is inherently sensitive to other gases in the environment (such as hydrogen sulfide), making the sensor's gas selectivity unreliable. Furthermore, tungsten trioxide is sensitive to ambient temperature and reacts to hydrogen to varying degrees at different temperatures, with its most complete reaction at high temperatures. This can lead to inaccurate measurements in actual environments.

[0005] The shortcomings of the "single-mode fiber-hollow-core fiber-single-mode fiber" structure: The direct fusion of single-mode fiber-hollow-core fiber-single-mode fiber into a closed Fabry-Perot cavity results in low sensor sensitivity. The sensing mechanism of this structure changes the parameters of the optical fiber structure itself (such as cavity length) through heat release or stress stretching of external materials. Since this closed optical fiber structure is relatively stable, the cavity length change is relatively small, which is not conducive to the detection of low-concentration hydrogen.

[0006] The shortcomings of "graphene / palladium" materials: Using graphene materials as a flexible substrate for palladium can improve sensitivity to a certain extent, but the Young's modulus of graphene materials is very high and usually only tens of nanometers thick, while the thickness of palladium is only a few nanometers. The smaller thickness of palladium leads to a small detection range of hydrogen concentration, and when carrying a thicker palladium film, the sensor response speed is reduced, and graphene has the risk of stretching and cracking. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a Fabry-Perot interference type hydrogen detection device and method.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A Fabry-Perot interference type hydrogen detection device comprises: a broadband light source, a spectrometer, a fiber coupler, a sensing probe, a test gas chamber, and a reference probe. The sensing probe and the reference probe have a sensor structure based on a fiber Fabry-Perot cavity. The fiber coupler has four ports A, B, C, and D. The fiber coupler transmits input light emitted by the broadband light source through port A and outputs it to the sensing probe and the reference probe through ports B and C. Light reflected back by the fiber Fabry-Perot cavities of the sensing probe and the reference probe is then output to the spectrometer through port D, thereby demodulating an interference spectrum. The hydrogen to be detected and air are mixed and then enter the test gas chamber through a gas flow rate controller and are discharged from an outlet. The sensing probe is located in the test gas chamber, while the reference probe is not located in the test gas chamber. The sensing probe uses an anodic aluminum oxide / palladium thin film as a terminal reflector of the Fabry-Perot cavity and obtains hydrogen concentration information in the environment by detecting the interference spectrum through the spectrometer. The reference probe uses two single-mode optical fiber end faces aligned in a sleeve to form an air Fabry-Perot cavity.

[0010] Preferably, the sensor structure of the sensing probe based on the optical fiber Fabry-Perot cavity includes: a single-mode optical fiber, an optical fiber sleeve, and an anodized aluminum / palladium film connected in sequence; wherein, an anodized aluminum film and a palladium composite film are used as sensitive elements, and the single-mode optical fiber and the optical fiber sleeve are connected and an air cavity is reserved, and the sleeve is connected to the composite film to form a Fabry-Perot interference cavity.

[0011] Preferably, the diameter of the single-mode optical fiber is 125 μm, the inner diameter of the optical fiber sleeve is 126 μm, the thickness of the anodized aluminum film is 130 nm, the nanopore diameter is 80 nm, and the pore period is 125 nm.

[0012] Preferably, the anodized aluminum oxide film is attached to the polymethyl methacrylate layer, the polymethyl methacrylate layer is first dissolved by an acetone solution, and then the anodized aluminum oxide layer is transferred to deionized water for washing, and the optical fiber sleeve directly contacts the anodized aluminum oxide in water and is transferred to the end face of the sleeve; palladium is attached to the outer surface of the anodized aluminum oxide by magnetron sputtering.

[0013] The present invention also provides a Fabry-Perot interference type hydrogen detection method, comprising:

[0014] Step S1: The fiber coupler transmits input light from a broadband light source through port A to a sensing probe and a reference probe through ports B and C. The light reflected by the sensing probe and the reference probe is then output to a spectrometer through port D, thereby demodulating the interference spectrum. The sensing probe and the reference probe have a sensor structure based on a fiber Fabry-Perot cavity. The sensing probe is located in a test chamber, while the reference probe is not located in the test chamber. The hydrogen gas to be tested is mixed with air and then enters the test chamber through a gas flow controller.

[0015] Step S2: The sensing probe uses an anodic aluminum oxide / palladium film as the terminal reflector of the Fabry-Perot cavity and detects the interference spectrum through a spectrometer to obtain the hydrogen concentration information in the environment; the reference probe uses two single-mode optical fiber end faces aligned in a sleeve to form an air Fabry-Perot cavity, and the reference probe only provides a stable reference spectrum.

[0016] Preferably, the sensor structure of the sensing probe based on the optical fiber Fabry-Perot cavity includes: a single-mode optical fiber, an optical fiber sleeve, and an anodized aluminum / palladium film connected in sequence; wherein, an anodized aluminum film and a palladium composite film are used as sensitive elements, and the single-mode optical fiber and the optical fiber sleeve are connected and an air cavity is reserved, and the sleeve is connected to the composite film to form a Fabry-Perot interference cavity.

[0017] Preferably, the diameter of the single-mode optical fiber is 125 μm, the inner diameter of the optical fiber sleeve is 126 μm, the thickness of the anodized aluminum film is 130 nm, the nanopore diameter is 80 nm, and the pore period is 125 nm.

[0018] Preferably, the anodized aluminum oxide film is attached to the polymethyl methacrylate layer, the polymethyl methacrylate layer is first dissolved by an acetone solution, and then the anodized aluminum oxide layer is transferred to deionized water for washing, and the optical fiber sleeve directly contacts the anodized aluminum oxide in water and is transferred to the end face of the sleeve; palladium is attached to the outer surface of the anodized aluminum oxide by magnetron sputtering.

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] 1. The larger the suspended diameter of the hydrogen-sensitive film, the greater the deformation and bending deflection after reacting with hydrogen. The use of an optical fiber sleeve (inner diameter 126μm) instead of a hollow-core optical fiber (inner diameter of tens of microns) improves the sensor response sensitivity. Its relatively simple preparation also greatly reduces the process cost.

[0021] 2. The anodized aluminum / palladium film is suspended on the end face of the optical fiber sleeve, serving as both a terminal reflector and a hydrogen-sensitive material, making the sensor structure more compact. At the same time, the deformation of the film directly affects the cavity length and thus changes the optical path difference of the interference structure, making the interference spectrum respond more quickly to changes in hydrogen concentration.

[0022] 3. Using anodized aluminum as the palladium substrate, the composite film exhibits a rough, porous nanostructure after sputtering. Mechanical analysis shows that this porous structure has a lower Young's modulus and higher hydrogen response sensitivity. The film also has a larger specific surface area, which increases the hydrogen adsorption rate.

[0023] 4. The vernier effect generated by the parallel dual FPI structure is used to amplify the sensor sensitivity. The cavity lengths of the two FPIs are similar and the amplification factor is adjustable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0025] Figure 1 This is a schematic structural diagram of a Fabry-Perot interferometer hydrogen detection device according to an embodiment of the present invention;

[0026] Figure 2 Schematic diagram of hydrogen response spectrum of the sensor probe;

[0027] Figure 3 Schematic diagram of hydrogen response spectrum of the vernier effect;

[0028] Figure 4 It is a schematic diagram of the sensor probe structure;

[0029] Figure 5 Schematic diagram of the hydrogen-induced strain principle of the suspended membrane;

[0030] Figure 6 Schematic diagram of the effect of different nanopore radii on the deflection of anodized aluminum oxide films. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1:

[0034] like Figure 1As shown, an embodiment of the present invention provides a Fabry-Perot interferometer hydrogen detection device, comprising: a broadband light source 4, a spectrometer 5, a fiber coupler 6, a sensor probe 7, a test gas chamber 8, and a reference probe 9; wherein the sensor probe 7 and the reference probe 9 have a sensor structure based on a fiber Fabry-Perot cavity, and the fiber coupler 6 has four ports A, B, C, and D. The fiber coupler 6 outputs the input light emitted by the broadband light source 4 to the sensor probe 7 (through port B) and the reference probe 9 (through port C) through port A, and the reflected input light is then transmitted through port D. The output port is output to the spectrometer 5, thereby demodulating the interference spectrum; the light reflected back from the optical fiber Fabry-Perot cavity of the sensor probe and the reference probe is then output to the spectrometer through the D port, thereby demodulating the interference spectrum; the hydrogen to be detected is mixed with air and then passes through the gas flow rate controller into the test chamber and discharged from the outlet; the sensor probe is located in the test chamber, and the reference probe is not located in the test chamber, wherein the sensor probe uses anodized aluminum / palladium film as the terminal reflector of the Fabry-Perot cavity and detects the interference spectrum through the spectrometer to obtain the hydrogen concentration information in the environment. The reference probe uses two single-mode optical fiber end faces to align in the sleeve and form an air Fabry-Perot cavity. The reference probe only provides a stable reference spectrum to achieve the cursor effect. The optical fiber Fabry-Perot uses two parallel high-reflectivity planes to form a resonant cavity. After multiple reflections in the cavity, interference is generated. The interaction between hydrogen and the sensitive material changes the optical properties of the resonant cavity, which leads to changes in the interference spectrum and then demodulates the changes in the hydrogen concentration in the environment. The relationship between the interference spectrum and the hydrogen concentration demodulated without adding the reference probe 9 is as follows Figure 2 The vernier effect spectrum demodulated by adding reference probe 9 is shown as Figure 3 shown.

[0035] like Figure 4 As shown, the sensor probe's fiber-optic Fabry-Perot cavity-based sensor structure comprises: a single-mode optical fiber 1, an optical fiber sleeve 2, and an anodized aluminum oxide / palladium film 3, connected in sequence. The anodized aluminum oxide film and a palladium composite film (AAO / Pd) serve as the sensitive element. The single-mode optical fiber and the optical fiber sleeve are connected, leaving an air cavity. The sleeve is then connected to the composite film to create a Fabry-Perot interferometer cavity. The single-mode optical fiber has a diameter of 125 μm, the inner diameter of the optical fiber sleeve is 126 μm, the thickness of the anodized aluminum oxide film is 130 nm, the nanopore size is 80 nm, and the pore period is 125 nm. The anodized aluminum oxide film is attached to a polymethyl methacrylate layer. The polymethyl methacrylate layer is first dissolved in acetone, then transferred to deionized water for washing. The optical fiber sleeve can be directly exposed to the anodized aluminum oxide in water, thereby transferring the palladium to the sleeve end face. Palladium is deposited on the outer surface of the anodized aluminum oxide by magnetron sputtering, with a thickness controlled to between tens and hundreds of nanometers.

[0036] like Figure 5 As shown in the figure, the fiber end face and the film form two reflection surfaces. The incident light is reflected multiple times at the two interfaces. When the reflectivity is relatively low, only the first two reflected beams can be considered. Assuming that the reflectivities of the two reflection surfaces are R1 and R2, the interference reflection spectrum intensity I of the two double beams can be approximately expressed as:

[0037]

[0038] Among them, I1=R1 is the light intensity after reflection from the first reflective surface, I2=(1-R1) 2 R2 is the intensity of light reflected by the second reflective surface, n is the refractive index of the medium in the FP cavity, and L is the length of the FP cavity. When the anodic aluminum oxide / palladium composite film is exposed to the H2 environment, the Pd surface adsorbs H2 molecules and dissociates them into hydrogen atoms, which occupy the metal lattice of Pd through diffusion and form palladium hydride (PdH x ), which causes the Pd lattice to expand and stretch the composite film outward, ultimately leading to a slight change in the FP cavity length. The cavity length change Δh can be expressed as:

[0039]

[0040] Where R0 is the effective radius of the Pd / AAO composite film, K is the sievert coefficient p (torr) is the hydrogen partial pressure. The relationship between p and hydrogen concentration C is expressed as E Pd and E AAO are the Young's modulus of Pd film and AAO film, T Pd and T AAO are the thicknesses of Pd and AAO, respectively. By tracking the wavelength shift (Δλ) of the interference spectrum, the change in FP cavity length (Δh) can be easily measured, where Δλ = λΔh / h, h and λ are the initial cavity length and the wavelength of the interference peak, respectively. Since Pd and hydrogen are reversible reactions, when the hydrogen concentration in the environment decreases, the spectrum in the formula gradually returns to its initial position, thereby achieving repeated detection of hydrogen. Since the AAO film is a special alumina material with a uniform array of nanopores, its Young's modulus is different from that of flat and dense alumina. The COMSOL multi-physics field analysis software was used to simulate the effect of its nanopore radius on the bending deflection of the film under stress, as shown below: Figure 6 As shown, it can be seen that within the radius range of 10-60nm, the degree of bending deformation of the film under force is positively correlated with the radius of the nanopore. The larger the nanopore radius, the higher the sensing sensitivity.

[0041] The present invention has the following innovative features:

[0042] 1. Application of anodized aluminum oxide film: It is proposed to use anodized aluminum oxide film as a support layer for palladium. After the double-layer composite film is exposed to hydrogen, the response speed is faster and the hydrogen-induced strain is obvious, which can achieve more sensitive gas detection while having a compact structure.

[0043] 2. Use a fiber optic sleeve to align the end faces of two single-mode optical fibers to make a reference Fabry-Perot cavity. Use a 2×2 3dB coupler to connect the reference probe and the sensor probe in parallel to the optical path to achieve vernier effect to enhance the sensitivity of the sensor.

[0044] 3. Bonding the film to the optical fiber sleeve: The prepared anodized aluminum film is attached to the polymethyl methacrylate layer. The polymethyl methacrylate layer is first dissolved in acetone solution. The anodized aluminum film is then transferred to deionized water for washing through a glass slide. The end face of the optical fiber sleeve is then brought into perpendicular contact with the film in the deionized water. The film and sleeve are bonded using van der Waals forces. Finally, palladium is bonded to the outer surface of the anodized aluminum using magnetron sputtering.

[0045] Example 2:

[0046] An embodiment of the present invention further provides a Fabry-Perot interferometry hydrogen detection method, comprising:

[0047] Step S1: The fiber coupler transmits input light from a broadband light source through port A to a sensing probe and a reference probe through ports B and C. The light reflected by the sensing probe and the reference probe is then output to a spectrometer through port D, thereby demodulating the interference spectrum. The sensing probe and the reference probe have a sensor structure based on a fiber Fabry-Perot cavity. The sensing probe is located in a test chamber, while the reference probe is not located in the test chamber. The hydrogen gas to be tested is mixed with air and then enters the test chamber through a gas flow controller.

[0048] Step S2: The sensing probe uses an anodic aluminum oxide / palladium film as the terminal reflector of the Fabry-Perot cavity and detects the interference spectrum through a spectrometer to obtain the hydrogen concentration information in the environment; the reference probe uses two single-mode optical fiber end faces aligned in a sleeve to form an air Fabry-Perot cavity, and the reference probe only provides a stable reference spectrum.

[0049] As an implementation method of an embodiment of the present invention, the sensor structure of the sensing probe based on the optical fiber Fabry-Perot cavity includes: a single-mode optical fiber, an optical fiber sleeve, and an anodized aluminum / palladium film connected in sequence; wherein, an anodized aluminum film and a palladium composite film are used as sensitive elements, and the single-mode optical fiber and the optical fiber sleeve are connected and an air cavity is reserved, and the sleeve is connected to the composite film to form a Fabry-Perot interference cavity.

[0050] As an implementation of an embodiment of the present invention, the diameter of the single-mode optical fiber is 125 μm, the inner diameter of the optical fiber sleeve is 126 μm, the thickness of the anodized aluminum film is 130 nm, the nanopore diameter is 80 nm, and the pore period is 125 nm.

[0051] As an implementation method of an embodiment of the present invention, an anodized aluminum oxide film is attached to a polymethyl methacrylate layer. The polymethyl methacrylate layer is first dissolved by an acetone solution, and then the anodized aluminum oxide layer is transferred to deionized water for washing. The optical fiber sleeve directly contacts the anodized aluminum oxide in water and is thereby transferred to the end face of the sleeve; palladium is attached to the outer surface of the anodized aluminum oxide by magnetron sputtering.

[0052] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A Fabry-Perot interferometer type hydrogen detection device, characterized in that: include: Broadband light source, spectrometer, fiber coupler, sensor probe, test chamber, reference probe; The sensing probe and reference probe have a sensor structure based on a fiber Fabry-Perot cavity. The fiber coupler has four ports, A, B, C, and D. The fiber coupler transmits input light emitted by a broadband light source through port A and outputs it to the sensing probe and reference probe through ports B and C. The light reflected back from the fiber Fabry-Perot cavity of the sensing probe and reference probe is then output to the spectrometer through port D, thereby demodulating the interference spectrum. The hydrogen gas to be detected and air are mixed and then enter the test gas chamber through a gas flow controller and discharged from the outlet. The sensing probe is located in the test gas chamber, while the reference probe is not located in the test gas chamber. The sensing probe uses an anodized aluminum / palladium thin film as the terminal reflector of the Fabry-Perot cavity and uses a spectrometer to detect the interference spectrum to obtain hydrogen concentration information in the environment. The reference probe uses two single-mode optical fiber end faces aligned in a sleeve to form an air Fabry-Perot cavity.

2. The Fabry-Perot interference type hydrogen gas detection device according to claim 1, wherein: The sensor structure of the sensor probe based on the optical fiber Fabry-Perot cavity includes: a single-mode optical fiber, an optical fiber sleeve, and an anodized aluminum / palladium film connected in sequence; among them, the anodized aluminum film and the palladium composite film are used as sensitive elements, and the single-mode optical fiber and the optical fiber sleeve are connected and an air cavity is reserved, and the sleeve is connected to the composite film to form a Fabry-Perot interference cavity.

3. The Fabry-Perot interference type hydrogen gas detection device according to claim 1, wherein: The diameter of the single-mode optical fiber is 125 μm, the inner diameter of the optical fiber sleeve is 126 μm, the thickness of the anodized aluminum film is 130 nm, the nanopore diameter is 80 nm, and the pore period is 125 nm.

4. The Fabry-Perot interference type hydrogen gas detection device according to claim 3, wherein: The anodized aluminum film is attached to the polymethyl methacrylate layer. The polymethyl methacrylate layer is first dissolved in acetone solution, and then the anodized aluminum layer is transferred to deionized water for washing. The optical fiber sleeve directly contacts the anodized aluminum in water and is transferred to the sleeve end face. Palladium is deposited on the outer surface of anodized aluminum by magnetron sputtering.

5. A Fabry-Perot interferometry hydrogen detection method, characterized in that: include: Step S1: The fiber coupler transmits input light from a broadband light source through port A to a sensing probe and a reference probe through ports B and C. The light reflected by the sensing probe and the reference probe is then output to a spectrometer through port D, thereby demodulating the interference spectrum. The sensing probe and the reference probe have a sensor structure based on a fiber Fabry-Perot cavity. The sensing probe is located in a test chamber, while the reference probe is not located in the test chamber. The hydrogen gas to be tested is mixed with air and then enters the test chamber through a gas flow controller. Step S2: The sensor probe uses an anodic aluminum oxide / palladium film as the terminal reflector of the Fabry-Perot cavity and detects the interference spectrum through a spectrometer to obtain hydrogen concentration information in the environment; The reference probe uses two single-mode optical fiber end faces aligned in a sleeve to form an air Fabry-Perot cavity. The reference probe only provides a stable reference spectrum.

6. The Fabry-Perot interferometry hydrogen detection method according to claim 5, wherein: The sensor structure of the sensor probe based on the optical fiber Fabry-Perot cavity includes: a single-mode optical fiber, an optical fiber sleeve, and an anodized aluminum / palladium film connected in sequence; among them, the anodized aluminum film and the palladium composite film are used as sensitive elements, and the single-mode optical fiber and the optical fiber sleeve are connected and an air cavity is reserved, and the sleeve is connected to the composite film to form a Fabry-Perot interference cavity.

7. The Fabry-Perot interferometry hydrogen detection method according to claim 6, wherein: The diameter of the single-mode optical fiber is 125 μm, the inner diameter of the optical fiber sleeve is 126 μm, the thickness of the anodized aluminum film is 130 nm, the nanopore diameter is 80 nm, and the pore period is 125 nm.

8. The Fabry-Perot interferometry hydrogen detection method according to claim 7, wherein: The anodized aluminum film is attached to the polymethyl methacrylate layer. The polymethyl methacrylate layer is first dissolved in acetone solution, and then the anodized aluminum layer is transferred to deionized water for washing. The optical fiber sleeve directly contacts the anodized aluminum in water and is transferred to the sleeve end face. Palladium is deposited on the outer surface of anodized aluminum by magnetron sputtering.

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