CN117434031A - Optical fiber gas molecular mass sensor and preparation method and mass measurement method thereof - Google Patents
Optical fiber gas molecular mass sensor and preparation method and mass measurement method thereof Download PDFInfo
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 127
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 238000000691 measurement method Methods 0.000 title abstract description 6
- 239000012528 membrane Substances 0.000 claims abstract description 59
- 230000003287 optical effect Effects 0.000 claims abstract description 48
- 239000000835 fiber Substances 0.000 claims abstract description 35
- 239000010408 film Substances 0.000 claims description 123
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 48
- 229910021389 graphene Inorganic materials 0.000 claims description 48
- 238000001514 detection method Methods 0.000 claims description 26
- 238000001228 spectrum Methods 0.000 claims description 24
- 238000009792 diffusion process Methods 0.000 claims description 20
- 230000005284 excitation Effects 0.000 claims description 20
- 239000011148 porous material Substances 0.000 claims description 17
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 16
- 239000011889 copper foil Substances 0.000 claims description 16
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 16
- 239000008367 deionised water Substances 0.000 claims description 11
- 229910021641 deionized water Inorganic materials 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 239000012080 ambient air Substances 0.000 claims description 6
- 238000005520 cutting process Methods 0.000 claims description 6
- 239000010409 thin film Substances 0.000 claims description 6
- 238000007740 vapor deposition Methods 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 4
- 238000007667 floating Methods 0.000 claims description 4
- 239000003570 air Substances 0.000 claims description 3
- 238000007865 diluting Methods 0.000 claims description 3
- 230000008878 coupling Effects 0.000 claims description 2
- 238000010168 coupling process Methods 0.000 claims description 2
- 238000005859 coupling reaction Methods 0.000 claims description 2
- 238000005530 etching Methods 0.000 claims description 2
- 238000003466 welding Methods 0.000 claims description 2
- 238000005516 engineering process Methods 0.000 abstract description 8
- 238000005259 measurement Methods 0.000 abstract description 4
- 239000007789 gas Substances 0.000 description 119
- 238000010586 diagram Methods 0.000 description 8
- 239000012466 permeate Substances 0.000 description 8
- 230000003993 interaction Effects 0.000 description 7
- 238000005253 cladding Methods 0.000 description 5
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- 238000012544 monitoring process Methods 0.000 description 4
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- 229910052737 gold Inorganic materials 0.000 description 3
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- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
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- 239000010410 layer Substances 0.000 description 2
- 238000001755 magnetron sputter deposition Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
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- 238000000746 purification Methods 0.000 description 2
- 238000009423 ventilation Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000005411 Van der Waals force Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
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- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012510 hollow fiber Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- -1 mass spectrometers Chemical compound 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 238000011897 real-time detection Methods 0.000 description 1
- 238000002310 reflectometry Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/25—Preparing the ends of light guides for coupling, e.g. cutting
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/255—Splicing of light guides, e.g. by fusion or bonding
- G02B6/2551—Splicing of light guides, e.g. by fusion or bonding using thermal methods, e.g. fusion welding by arc discharge, laser beam, plasma torch
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
- G01N2021/458—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods using interferential sensor, e.g. sensor fibre, possibly on optical waveguide
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Abstract
The invention discloses an optical fiber gas molecular mass sensor based on optical fiber sensing, which comprises a single-mode optical fiber, a hollow pipe and a porous membrane, wherein the hollow pipe is provided with an optical microcavity, a first port and a second port which are respectively communicated with two ends of the optical microcavity, the first port of the hollow pipe is connected with one end face of the single-mode optical fiber, and the second port of the hollow pipe is connected with the porous membrane; the end face of the single-mode fiber, the optical microcavity of the hollow tube and the porous permeable film together form an FP interferometer. The optical fiber gas molecular mass sensor based on optical fiber sensing is based on an optical fiber sensing technology, and can realize measurement of gas molecular mass. The invention also discloses a preparation method and a quality measurement method of the optical fiber gas molecular mass sensor.
Description
Technical Field
The invention relates to an optical fiber sensing technology, in particular to an optical fiber gas molecular mass sensor, a preparation method thereof and a mass measurement method.
Background
The gas molecular mass sensor is used for screening gas molecules with different masses, is widely applied in life, and can be used in gas molecular sieves, mass spectrometers, hydrogen purification, natural gas purification, air separation, carbon dioxide capture, organic steam separation and the like.
The traditional gas membrane separation technology based on the on-chip technology generally needs complex detection equipment in practical application, and although the preparation technology is mature and the cost is controllable, the application scene is limited by the electronic detection equipment, and the real-time detection is difficult to carry out in a closed gas chamber with high vacuum degree and serious electromagnetic interference.
Therefore, the development of the gas molecular mass sensor with an all-optical structure, electromagnetic interference resistance, microminiaturization, high sensitivity and real-time visual monitoring has very important significance.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides the optical fiber gas molecular mass sensor based on optical fiber sensing, which can realize measurement of gas molecular mass and has the advantages of electromagnetic interference resistance, microminiaturization, high sensitivity, real-time visual monitoring and the like.
The invention also provides a preparation method and a quality measurement method of the optical fiber gas molecular mass sensor.
The technical problems to be solved by the invention are realized by the following technical scheme:
the optical fiber gas molecular mass sensor based on optical fiber sensing comprises a single-mode optical fiber, a hollow tube and a porous membrane, wherein the hollow tube is provided with an optical microcavity, a first port and a second port which are respectively communicated with two ends of the optical microcavity, the first port of the hollow tube is connected with one end face of the single-mode optical fiber, and the second port of the hollow tube is connected with the porous membrane; the end face of the single-mode fiber, the optical microcavity of the hollow tube and the porous permeable film together form an FP interferometer.
Further, the porous membrane comprises an elastic membrane and a reflecting membrane which are laminated, wherein the elastic membrane is formed on the second port of the hollow tube, and the reflecting membrane is formed on one surface of the elastic membrane, which is opposite to the hollow tube; and the elastic film and the reflecting film are provided with a diffusion air hole array.
Further, the aperture D of the diffusion pore array satisfies the formula,
wherein k is Boltzmann constant, T is ambient temperature, d is molecular diameter of gas to be measured, and p is ambient air pressure.
A preparation method of an optical fiber gas molecular mass sensor based on optical fiber sensing comprises the following steps:
step 100: taking a section of hollow tube, wherein the hollow tube is provided with an optical microcavity, and a first port and a second port which are respectively communicated with two ends of the optical microcavity;
step 200: connecting a first port of the hollow tube with one end face of the single-mode optical fiber;
step 300: and forming a porous film on the second port of the hollow tube, so that the end face of the single-mode fiber, the optical microcavity of the hollow tube and the porous film form an FP interferometer.
Further, in step 200, the step of connecting the first port of the hollow tube to an end face of the single-mode optical fiber is as follows:
step 210: cutting the end face of the single-mode optical fiber and the first port of the hollow tube flat respectively;
step 220: welding the end face of the single-mode fiber cut flat with the first end opening of the hollow Guan Qie flat;
step 230: and cutting the hollow tube welded on the single-mode fiber to a preset length, so that the optical microcavity of the hollow tube forms a preset cavity length on the end face of the single-mode fiber.
Further, the porous film includes an elastic film and a reflective film laminated; in step 300, the step of forming the porous membrane on the second port of the hollow tube is as follows:
step 310: forming the elastic membrane on a second port of the hollow tube;
step 320: forming the reflecting film on the side of the elastic film, which is opposite to the hollow tube;
step 330: etching the elastic film and the reflective film to form a gas permeation hole array on the elastic film and the reflective film.
Further, the elastic film includes a graphene film, and in step 310, the step of forming the elastic film on the second port of the hollow tube is as follows:
step 311: forming the graphene film on the copper foil by growing through a vapor deposition method;
step 312: dissolving and corroding the copper foil by adopting a ferric trichloride solution, so that the graphene film on the copper foil is transferred into the ferric trichloride solution;
step 313: diluting and filtering the ferric trichloride solution transferred with the graphene film by adopting deionized water, so that the graphene film in the ferric trichloride solution is transferred and floated on the deionized water;
step 314: slowly approaching the second port of the hollow tube to the graphene film floating on the deionized water, and slowly pulling away the second port of the hollow tube after the second port of the hollow tube contacts the graphene film, so that the graphene film is transferred to the second port of the hollow tube;
step 315: and drying the graphene film on the hollow tube to suspend the graphene film on the hollow tube.
Further, the aperture D of the diffusion pore array satisfies the formula,
wherein k is Boltzmann constant, T is ambient temperature, d is molecular diameter of gas to be measured, and p is ambient air pressure.
A gas molecular mass measurement method based on optical fiber sensing comprises the following steps:
s1: placing the fiber optic gas molecular mass sensor of claim 1 in a vacuum chamber;
s2: coupling an excitation light signal with a first wavelength and a detection light signal with a second wavelength into the optical fiber gas molecular mass sensor together, so that the excitation light signal drives a porous permeable film in the optical fiber gas molecular mass sensor to generate simple harmonic vibration;
s3: acquiring a detection light signal reflected by the optical fiber gas molecular mass sensor to obtain a phase spectrum of the optical fiber gas molecular mass sensor;
s4: introducing the gas to be tested into the vacuum chamber;
s5: and calculating the gas molecular mass of the gas to be detected according to the frequency position of the permeation minimum value in the phase spectrum.
Further, the frequency position of the permeation minimum value in the phase spectrum of the optical fiber gas molecular mass sensor and the molecular mass of the gas to be detected satisfy the following formula:
f is the frequency position of the permeation minimum value in the phase spectrum, M is the molecular mass of the gas to be detected, T is the ambient temperature, V is the volume of the optical microcavity, A is the permeation total area of the porous permeation film, and R is the universal gas constant.
The invention has the following beneficial effects: the optical fiber based optical fiber sensor technology is used for jointly forming an FP interferometer for measuring the molecular mass of gas through the end face of the single-mode optical fiber, the optical microcavity of the hollow tube and the porous permeable film, when the aperture of the porous permeable film is smaller than the molecular mean free path of gas to be measured, the resistance of the gas to be measured when the gas to be measured permeates the porous permeable film mainly comes from the interaction force between molecules and the hole wall, at the moment, the molecular motion of the gas to be measured in the porous permeable film meets the Knudsen diffusion principle and the Graham permeation mechanism, the interaction force between gas molecules and the hole wall can change the built-in stress of the porous permeable film when the gas molecules permeate the porous permeable film, so that the resonance frequency of the porous permeable film is changed, the smaller the interaction force between the gas molecules with the hole wall is, the time for permeating the porous permeable film is also shorter, the permeation minima in the phase spectrum of the porous permeable film drifts towards the high-frequency direction, and the molecular mass of the gas to be measured can be obtained through demodulating the permeation value change of the porous permeable film, and the molecular mass of the gas to be measured is small, and the optical fiber based optical fiber sensor technology has the advantages of miniaturization, high sensitivity, real-time monitoring and the like.
Drawings
Fig. 1 is a schematic structural diagram of an optical fiber gas molecular mass sensor provided by the invention.
Fig. 2 is a schematic diagram of a diffusion pore array of a porous membrane in an optical fiber gas molecular mass sensor according to the present invention.
Fig. 3 is a block diagram of steps of a method for manufacturing an optical fiber gas molecular mass sensor according to the present invention.
Fig. 4 is a block diagram showing the steps 200 in the preparation method of the optical fiber gas molecular mass sensor according to the present invention.
Fig. 5 is a block diagram showing the steps 300 in the method for manufacturing an optical fiber gas molecular mass sensor according to the present invention.
Fig. 6 is a block diagram showing the steps of step 310 in the method for manufacturing an optical fiber gas molecular mass sensor according to the present invention.
Fig. 7 is a block diagram of steps of a method for measuring molecular mass of gas based on optical fiber sensing according to the present invention.
Fig. 8 is a system schematic diagram of a method for measuring molecular mass of gas based on optical fiber sensing according to the present invention.
Detailed Description
The present invention is described in detail below with reference to the drawings and the embodiments, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
In the description of the present invention, it should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the present invention and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", or a third "may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," "disposed," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, or can be communicated between two elements or the interaction relationship between the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
Example 1
As shown in fig. 1, an optical fiber gas molecular mass sensor based on optical fiber sensing comprises a single-mode optical fiber 13, a hollow tube 16 and a porous membrane 18, wherein the hollow tube 16 is provided with an optical microcavity 17 and a first port and a second port which are respectively communicated with two ends of the optical microcavity 17, the first port of the hollow tube 16 is connected with one end face of the single-mode optical fiber 13, and the second port of the hollow tube 16 is connected with the porous membrane 18; the end face of the single-mode fiber 13, the optical microcavity 17 of the hollow tube 16 and the porous membrane 18 together form an FP interferometer.
The patent is based on an optical fiber sensing technology, the optical microcavity 17 of the single-mode optical fiber 13 end face, the optical microcavity 17 of the hollow tube 16 and the porous membrane 18 jointly form an FP interferometer for measuring the molecular mass of gas, when the aperture of the porous membrane 18 is smaller than the molecular mean free path of the gas to be measured, the resistance of the gas to be measured when the gas to be measured permeates the porous membrane 18 mainly comes from the interaction force between molecules and pore walls, at the moment, the molecular motion of the gas to be measured in the porous membrane 18 meets the Knudsen diffusion principle and the Graham permeation mechanism, the interaction force between the gas molecules and the pore walls changes the built-in stress of the porous membrane 18 when the gas molecules permeate the porous membrane 18, so that the resonance frequency of the porous membrane 18 is changed, the smaller the interaction force between the gas molecules and the pore walls is smaller, the time of the gas molecules is shorter when the gas permeates the porous membrane 18 is shorter, the permeation time of the very small value in the phase spectrum of the porous membrane 18 is larger, the drift quantity of the gas to be measured in the high-frequency direction is larger, and the micro-scale electromagnetic interference resistance of the gas can be measured, and the micro-scale electromagnetic interference resistance is large, and the electromagnetic interference resistance can be obtained.
In the optical fiber gas molecular mass sensor, the end face of the single-mode optical fiber 13 and the porous film 18 together form two reflecting surfaces of the FP interferometer, when a detection optical signal passes through the end face of the single-mode optical fiber 13, primary reflection occurs, when the detection optical signal reaches the porous film 18, primary reflection occurs again, and the two reflected detection optical signals interfere due to an optical path difference. When the gas to be measured permeates the porous membrane 18, a minimum value appears in the phase spectrum output by the optical fiber gas molecular mass sensor, and the minimum value is a permeation minimum value corresponding to the gas to be measured (if the gas to be measured cannot permeate the porous membrane 18 or does not meet the knoop diffusion principle and the graham permeation mechanism, the minimum value does not exist), the frequency position of the permeation minimum value is related to the permeation time of the gas to be measured, and the shorter the permeation time of the gas to be measured is, the larger the drift amount of the permeation minimum value towards the high frequency direction is.
The single-mode optical fiber 13 comprises a fiber core 14 and a cladding 15, the cladding 15 is wrapped around the outer periphery of the fiber core 14, the refractive index of the fiber core 14 is different from that of the cladding 15, so that the optical signal can be totally reflected at the juncture of the fiber core 14 and the cladding 15 and further transmitted forwards in the fiber core 14.
The cladding 15 of the single-mode fiber 13 is connected with the wall of the hollow tube 16, and the fiber core 14 of the single-mode fiber 13 is connected with the optical microcavity 17 of the hollow tube 16, but the radial direction of the optical microcavity 17 should be larger than the diameter of the fiber core 14.
The porous film 18 includes an elastic film 19 and a reflective film 20 laminated, and the elastic film 19 has a thickness of 2-3nm and may include a single-layer, double-layer or multi-layer graphene film; the thickness of the reflective film 20 is about 12nm, and may include a nano-gold film.
The elastic film 19 is used for generating simple harmonic vibration to modulate the detection light signal, reducing the elastic modulus of the porous permeable film 18, improving the detection sensitivity of the FP interferometer, and the reflective film 20 is used for carrying out simple harmonic vibration along with the elastic film 19, reflecting the detection light signal, improving the reflectivity of the porous permeable film 18, and improving the detection range of the FP interferometer.
Wherein the elastic film 19 is formed on the second port of the hollow tube 16, and the reflective film 20 is formed on a surface of the elastic film 19 facing away from the hollow tube 16; as shown in fig. 2, the elastic film 19 and the reflective film 20 are formed with a diffusion pore array 23.
The diffusion pore array 23 has uniform and dense nano-scale diffusion pores, which allow gases of different molecular masses to pass therethrough, but according to the knoop diffusion principle, gases of different molecular masses have different permeabilities due to different average free path, and different resistances when diffusing in the nano-scale diffusion pores.
The aperture D of the diffusion pore array 23 satisfies the formula,
wherein k is Boltzmann constant, T is ambient temperature, d is the molecular diameter of the gas to be detected, and p is ambient air pressure.
According to the above formula, the corresponding aperture can be set for the diffusion pore array 23 in a matching manner for the molecular diameter of the specific gas, so that the optical fiber gas molecular mass sensor can detect whether the gas to be detected is the specific gas by measuring the molecular mass, or the aperture of the diffusion pore array 23 can be set as small as possible, so that the optical fiber gas molecular mass sensor is suitable for measuring the gases with different molecular massesThe optical fiber gas molecular mass sensor can be used for measuring N when the aperture of the diffusion pore array 23 is set to 50nm or less at normal temperature and pressure 2 、He、H 2 、CO 2 、Ar、O 2 Molecular mass of various gases; if the gas to be detected is a mixed gas, the optical fiber gas molecular mass sensor can also detect the specific gas mixed in the gas to be detected.
Example two
A preparation method of an optical fiber gas molecular mass sensor based on optical fiber sensing is used for preparing the optical fiber gas molecular mass sensor based on optical fiber sensing in the embodiment I.
As shown in fig. 3, the preparation method comprises the following steps:
step 100: a length of hollow tube 16 is taken, and the hollow tube 16 is provided with an optical microcavity 17 and a first port and a second port which are respectively communicated with two ends of the optical microcavity 17.
In this step 100, the hollow tube 16 may be, but is not limited to, a capillary tube, a hollow core fiber, or the like.
Step 200: a first port of the hollow tube 16 is connected to an end face of the single mode fiber 13.
In this step 200, the hollow tube 16 and the single-mode optical fiber 13 may be placed in an optical fiber fusion splicer to be fused.
Specifically, as shown in fig. 4, in step 200, the step of connecting the first port of the hollow tube 16 with one end face of the single-mode optical fiber 13 is as follows:
step 210: the end face of the single-mode optical fiber 13 and the first end of the hollow tube 16 are each cut flat.
In this step 210, the lengths of the single-mode fiber 13 and the hollow tube 16 are not particularly limited, and the end face of the single-mode fiber 13 and the first port of the hollow tube 16 may be flattened by using an optical fiber cutter so that the end faces and the ports can be seamlessly abutted.
The hollow tube 16 may be a quartz capillary or a hollow fiber having an outer diameter identical to that of the single-mode fiber 13.
Step 220: the end face of the single-mode fiber 13 cut flat is welded with the first end face of the hollow tube 16 cut flat.
In this step 220, the end face of the single-mode fiber 13 cut flat and the second port of the hollow tube 16 cut flat are respectively placed on both ends of an optical fiber fusion splicer, and then the optical fiber fusion splicer is operated to align the end face of the single-mode fiber 13 with the second port of the hollow tube 16 and then discharge fusion splice.
Step 230: the hollow tube 16 fused to the single-mode optical fiber 13 is cut to a predetermined length so that the optical microcavity 17 of the hollow tube 16 forms a predetermined cavity length on the end face of the single-mode optical fiber 13.
In this step 230, the fused single-mode fiber 13 and the hollow tube 16 are placed on a two-dimensional moving platform, and the two-dimensional moving platform is controlled to drive the single-mode fiber 13 and the hollow tube 16 to move under the monitoring of the CCD, so as to adjust the relative position between the hollow tube 16 and the optical fiber cutter, and further move the predetermined cutting point on the hollow tube 16 to the position under the optical fiber cutter for cutting.
Step 300: a porous membrane 18 is formed on the second port of the hollow tube 16 such that the end face of the single mode fiber 13, the optical microcavity 17 of the hollow tube 16 and the porous membrane 18 form an FP interferometer.
In this step 300, the porous film 18 includes an elastic film 19 and a reflective film 20 stacked on each other, the elastic film 19 includes a graphene film having a thickness of 2-3nm, and the reflective film 20 includes a nano-gold film having a thickness of about 12 nm.
Specifically, as shown in fig. 5, in step 300, the step of forming the porous membrane 18 on the second port of the hollow tube 16 is as follows:
step 310: the elastic membrane 19 is formed on the second port of the hollow tube 16.
In this step 310, the elastic film 19 includes a graphene film formed on the second port of the hollow tube 16 by a wet transfer method, and has a thickness of between 2 and 3 nm.
Specifically, as shown in fig. 6, in step 310, the step of forming the elastic membrane 19 on the second port of the hollow tube 16 is as follows:
step 311: and growing and forming the graphene film on the copper foil by a vapor deposition method.
In the step 311, when the graphene film is formed on the copper foil by a vapor deposition method, the copper foil is fixed in a magnetron sputtering coating chamber of a deposition device, the surface of the copper foil is placed towards a graphene target, and the graphene target is bombarded by a high-energy ion beam, so that the graphene target is gasified and overflowed and is sputtered and attached on the surface of the copper foil, so that the graphene film with the thickness of 2-3nm is formed.
Step 312: and dissolving and corroding the copper foil by adopting a ferric trichloride solution, so that the graphene film on the copper foil is transferred into the ferric trichloride solution.
In this step 312, the concentration of the ferric trichloride solution is about 0.08g/ml, and only a small piece of copper foil is cut according to the second port size of the hollow tube 16, and is placed in the ferric trichloride solution for dissolution and corrosion, and the graphene film on the cut copper foil should be able to cover the second port of the hollow tube 16.
Step 313: and diluting and filtering the ferric trichloride solution transferred with the graphene film by adopting deionized water, so that the graphene film in the ferric trichloride solution is transferred and floated on the deionized water.
In step 313, deionized water is used to dilute and filter the ferric trichloride solution for the main purpose of cleaning the graphene film, avoiding copper foil and ferric trichloride remaining on the graphene film, and reducing the ph of the solution.
Step 314: and slowly approaching the second port of the hollow tube 16 to the graphene film floating on the deionized water, and slowly pulling away the second port of the hollow tube 16 after the second port contacts the graphene film, so that the graphene film is transferred to the second port of the hollow tube 16.
In this step 314, the second port of the hollow tube 16 should slowly approach the graphene film floating on the deionized water in parallel to the graphene film so that the second port of the hollow tube 16 can uniformly contact with the graphene film, thereby uniformly transferring and attaching the graphene film to the second port of the hollow tube 16.
Step 315: and drying the graphene film on the hollow tube 16 to suspend the graphene film on the hollow tube 16.
In this step 315, the graphene film is naturally dried at room temperature, and during the drying process, the graphene film has its peripheral region 21 attached to the reflective film 20 of the hollow tube 16 due to the van der waals force, and its central region 22 is suspended in front of the optical microcavity 17 of the hollow tube 16.
Step 320: the reflective film 20 is formed on the side of the elastic film 19 facing away from the hollow tube 16.
In this step 320, the reflective thin film includes a nano-gold thin film formed on the elastic thin film 19 by vapor deposition, and the thickness thereof is about 12 nm.
Specifically, when the reflective film 20 is formed on the elastic film 19 by vapor deposition, the hollow tube 16 is fixed in a magnetron sputtering coating chamber of a deposition device, the graphene film of the hollow tube 16 is placed towards a metal target, and the metal target is bombarded by a high-energy ion beam, so that the metal target is gasified and overflowed and sputtered to be attached to the graphene film of the hollow tube 16, so as to form the reflective film 20 with the thickness of about 12 nm.
Step 330: the elastic film 19 and the reflective film 20 are etched to form an array of gas permeation holes on the elastic film 19 and the reflective film 20.
In this step 330, the array of gas permeation holes is etched onto the elastic membrane 19 and the reflective membrane 20, preferably using a Focused Ion Beam (FIB).
Wherein the aperture D of the diffusion pore array 23 satisfies the formula,
wherein k is Boltzmann constant, T is ambient temperature, d is molecular diameter of gas to be measured, and p is ambient air pressure.
Example III
As shown in fig. 1 and 2, a method for measuring molecular mass of gas based on optical fiber sensing includes the following steps:
s1: the fiber optic gas molecular mass sensor of embodiment one is placed in a vacuum chamber.
In this step S1, a certain vacuum degree is set in the vacuum chamber, and under this vacuum degree, an initial phase spectrum of the porous permeable membrane 18 when it is acted by the excitation light signal is measured, and no permeation minimum value exists in the initial phase spectrum when the gas to be measured is not introduced.
S2: the excitation light signal with the first wavelength and the detection light signal with the second wavelength are coupled into the optical fiber gas molecular mass sensor together, so that the excitation light signal drives the porous permeable membrane 18 in the optical fiber gas molecular mass sensor to generate simple harmonic vibration.
In this step S2, an optical measurement system is used to measure the phase spectrum of the optical fiber gas molecular mass sensor, the optical measurement device includes an excitation laser 1, a signal generator 3, an electro-optical modulator 2, a detection laser 4, an optical fiber coupler 5, an optical fiber circulator 6, an optical isolator 7, a photodetector 8, and a vector network analyzer 9, the optical fiber coupler 5 has a first incident end, a second incident end, and an emitting end, the optical fiber circulator 6 has an incident end, a reflecting end, and a transmitting end, the excitation laser 1 is connected to the first incident end of the optical fiber coupler 5 through the electro-optical modulator 2, the detection laser 4 is connected to the second incident end of the optical fiber coupler 5, the emitting end of the optical fiber coupler 5 is connected to the incident end of the optical fiber circulator 6, the photodetector 8 is connected to the reflecting end of the optical fiber circulator 6 through the optical isolator 7, and the first end of the optical fiber 13 of the gas molecular mass sensor is connected to the transmitting end of the optical fiber circulator 6; the signal generator 3 is connected with and controls the electro-optical modulator 2, and the vector network analyzer 9 is connected with and controls the photoelectric detector 8.
The excitation laser 1 emits an excitation light signal with a first wavelength to the electro-optical modulator 2, the detection laser 4 emits a detection light signal with a second wavelength to the optical fiber coupler 5, and then the electro-optical modulator 2 modulates the light intensity of the excitation light signal under the periodic signal of the signal generator 3, so that the light intensity of the excitation light signal periodically changes to enter the optical fiber coupler 5, and the excitation light signal is coupled with the detection light signal and then enters the optical fiber gas molecular mass sensor.
In this embodiment, the optical fiber coupler 5 is a 90:10 coupler 5, i.e. when coupled, the excitation optical signal accounts for 90% of the total optical signal, and the detection optical signal accounts for 10% of the total optical signal.
When the excitation light signal coupled into the optical fiber gas molecular mass sensor acts on the porous membrane 18, the porous membrane 18 is irradiated by the excitation light signal with periodically changing light intensity, so that periodically changing thermal expansion or contraction is generated, and the periodic thermal expansion or contraction is forced to form simple harmonic vibration.
After the detection light signal coupled into the optical fiber gas molecular mass sensor is modulated and reflected by the porous membrane 18, the detection light signal carries the resonance frequency information of the porous membrane 18.
S3: and obtaining a detection light signal reflected by the optical fiber gas molecular mass sensor to obtain a phase spectrum of the optical fiber gas molecular mass sensor.
In this step S3, the detection light signal reflected by the optical fiber gas molecular mass sensor reenters the optical fiber circulator 6, and is then captured by the photodetector 8 through the optical isolator 7 from the reflection end of the optical fiber circulator 6. The photodetector 8 converts the reflected detection light signal into a corresponding electrical signal and provides the corresponding electrical signal to the vector network analyzer 9, and the vector network analyzer 9 outputs a corresponding phase spectrum.
The optical isolator 7 is used for filtering the doped excitation light signal in the detection light signal.
Before the vacuum chamber is not filled with the gas to be measured, a certain vacuum degree is set in the vacuum chamber, and under the vacuum degree, an initial phase spectrum of the porous permeable membrane 18 under the action of the excitation light signal is measured, and no permeation minimum value exists in the initial phase spectrum.
S4: and introducing the gas to be tested into the vacuum chamber.
In the step S4, a ventilation device is used to introduce the gas to be measured into the vacuum chamber. The ventilation device comprises a gas cylinder 12 and a flow controller 11, one end of the flow controller 11 is communicated with the gas cylinder 12, and the other end is communicated with the vacuum chamber; the gas cylinder 12 is used for loading the gas to be measured, and the flow controller 11 is used for controlling the flow rate of the gas to be measured into the vacuum chamber.
After the gas to be tested is introduced into the vacuum chamber, due to the permeation effect of the porous permeable membrane 18, part of the gas to be tested in the vacuum chamber permeates through the porous permeable membrane 18, so that the built-in stress of the porous permeable membrane 18 is changed, and the resonance frequency of the porous permeable membrane 18 when the porous permeable membrane is subjected to the action of the excitation light signal is changed and reflected to be a permeation minimum value on the phase spectrum.
S5: and calculating the gas molecular mass of the gas to be detected according to the frequency position of the permeation minimum value in the phase spectrum.
In the step S5, the frequency position of the permeation minimum in the phase spectrum is related to the permeation time of the gas to be measured through the porous permeable membrane 18, and the permeation time of the gas to be measured is related to the molecular mass thereof, so that the molecular mass of the gas to be measured can be calculated from the frequency position of the permeation minimum in the phase spectrum.
The permeation minimum value in the phase spectrum and the molecular mass of the gas to be detected satisfy the following formula:
f is the frequency position of the permeation minimum in the phase spectrum, M is the molecular mass of the gas to be measured, T is the ambient temperature, V is the volume of the optical microcavity 17, a is the total permeation area of the porous permeable membrane 18, and R is the universal gas constant.
Finally, it should be noted that the foregoing embodiments are merely for illustrating the technical solution of the embodiments of the present invention and are not intended to limit the embodiments of the present invention, and although the embodiments of the present invention have been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the embodiments of the present invention may be modified or replaced with the same, and the modified or replaced technical solution may not deviate from the scope of the technical solution of the embodiments of the present invention.
Claims (10)
1. The optical fiber gas molecular mass sensor based on optical fiber sensing is characterized by comprising a single-mode optical fiber, a hollow tube and a porous membrane, wherein the hollow tube is provided with an optical microcavity, a first port and a second port which are respectively communicated with two ends of the optical microcavity, the first port of the hollow tube is connected with one end face of the single-mode optical fiber, and the second port of the hollow tube is connected with the porous membrane; the end face of the single-mode fiber, the optical microcavity of the hollow tube and the porous permeable film together form an FP interferometer.
2. The optical fiber gas molecular mass sensor based on optical fiber sensing according to claim 1, wherein the porous permeable membrane comprises an elastic membrane and a reflective membrane which are laminated, the elastic membrane is formed on the second port of the hollow tube, and the reflective membrane is formed on the side of the elastic membrane facing away from the hollow tube; and the elastic film and the reflecting film are provided with a diffusion air hole array.
3. The optical fiber gas molecular mass sensor based on optical fiber sensing according to claim 2, wherein the aperture D of the diffusion pore array satisfies the formula,
wherein k is Boltzmann constant, T is ambient temperature, d is molecular diameter of gas to be measured, and p is ambient air pressure.
4. The preparation method of the optical fiber gas molecular mass sensor based on optical fiber sensing is characterized by comprising the following steps of:
step 100: taking a section of hollow tube, wherein the hollow tube is provided with an optical microcavity, and a first port and a second port which are respectively communicated with two ends of the optical microcavity;
step 200: connecting a first port of the hollow tube with one end face of the single-mode optical fiber;
step 300: and forming a porous film on the second port of the hollow tube, so that the end face of the single-mode fiber, the optical microcavity of the hollow tube and the porous film form an FP interferometer.
5. The method for manufacturing an optical fiber gas molecular mass sensor based on optical fiber sensing according to claim 4, wherein in step 200, the step of connecting the first port of the hollow tube with one end face of the single mode optical fiber is as follows:
step 210: cutting the end face of the single-mode optical fiber and the first port of the hollow tube flat respectively;
step 220: welding the end face of the single-mode fiber cut flat with the first end opening of the hollow Guan Qie flat;
step 230: and cutting the hollow tube welded on the single-mode fiber to a preset length, so that the optical microcavity of the hollow tube forms a preset cavity length on the end face of the single-mode fiber.
6. The method for manufacturing an optical fiber gas molecular mass sensor based on optical fiber sensing according to claim 4, wherein the porous permeable film comprises an elastic film and a reflective film laminated; in step 300, the step of forming the porous membrane on the second port of the hollow tube is as follows:
step 310: forming the elastic membrane on a second port of the hollow tube;
step 320: forming the reflecting film on the side of the elastic film, which is opposite to the hollow tube;
step 330: etching the elastic film and the reflective film to form a gas permeation hole array on the elastic film and the reflective film.
7. The method of manufacturing an optical fiber gas molecular mass sensor based on optical fiber sensing according to claim 6, wherein the elastic thin film comprises a graphene thin film, and the step of forming the elastic thin film on the second port of the hollow tube in step 310 comprises the steps of:
step 311: forming the graphene film on the copper foil by growing through a vapor deposition method;
step 312: dissolving and corroding the copper foil by adopting a ferric trichloride solution, so that the graphene film on the copper foil is transferred into the ferric trichloride solution;
step 313: diluting and filtering the ferric trichloride solution transferred with the graphene film by adopting deionized water, so that the graphene film in the ferric trichloride solution is transferred and floated on the deionized water;
step 314: slowly approaching the second port of the hollow tube to the graphene film floating on the deionized water, and slowly pulling away the second port of the hollow tube after the second port of the hollow tube contacts the graphene film, so that the graphene film is transferred to the second port of the hollow tube;
step 315: and drying the graphene film on the hollow tube to suspend the graphene film on the hollow tube.
8. The method for manufacturing an optical fiber gas molecular mass sensor based on optical fiber sensing according to claim 6, wherein the aperture D of the diffusion pore array satisfies the formula,
wherein k is Boltzmann constant, T is ambient temperature, d is molecular diameter of gas to be measured, and p is ambient air pressure.
9. The method for measuring the molecular mass of the gas based on the optical fiber sensing is characterized by comprising the following steps of:
s1: placing the fiber optic gas molecular mass sensor of claim 1 in a vacuum chamber;
s2: coupling an excitation light signal with a first wavelength and a detection light signal with a second wavelength into the optical fiber gas molecular mass sensor together, so that the excitation light signal drives a porous permeable film in the optical fiber gas molecular mass sensor to generate simple harmonic vibration;
s3: acquiring a detection light signal reflected by the optical fiber gas molecular mass sensor to obtain a phase spectrum of the optical fiber gas molecular mass sensor;
s4: introducing the gas to be tested into the vacuum chamber;
s5: and calculating the gas molecular mass of the gas to be detected according to the frequency position of the permeation minimum value in the phase spectrum.
10. The method for measuring the molecular mass of a gas based on optical fiber sensing according to claim 9, wherein the frequency position of the permeation minimum value in the phase spectrum of the optical fiber gas molecular mass sensor and the molecular mass of the gas to be measured satisfy the following formula:
f is the frequency position of the permeation minimum value in the phase spectrum, M is the molecular mass of the gas to be detected, T is the ambient temperature, V is the volume of the optical microcavity, A is the permeation total area of the porous permeation film, and R is the universal gas constant.
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