CN109406440B - Gas detection method based on chalcogenide glass suspension core optical fiber - Google Patents
Gas detection method based on chalcogenide glass suspension core optical fiber Download PDFInfo
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- CN109406440B CN109406440B CN201811380043.1A CN201811380043A CN109406440B CN 109406440 B CN109406440 B CN 109406440B CN 201811380043 A CN201811380043 A CN 201811380043A CN 109406440 B CN109406440 B CN 109406440B
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 144
- 239000005387 chalcogenide glass Substances 0.000 title claims abstract description 108
- 239000000725 suspension Substances 0.000 title claims abstract description 103
- 238000001514 detection method Methods 0.000 title claims abstract description 53
- 239000007789 gas Substances 0.000 claims abstract description 216
- 238000000411 transmission spectrum Methods 0.000 claims abstract description 38
- 230000003287 optical effect Effects 0.000 claims abstract description 18
- 239000011265 semifinished product Substances 0.000 claims description 37
- 239000000835 fiber Substances 0.000 claims description 18
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- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 10
- 238000012545 processing Methods 0.000 claims description 10
- 238000004080 punching Methods 0.000 claims description 9
- 125000006850 spacer group Chemical group 0.000 claims description 9
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- ZZIZZTHXZRDOFM-XFULWGLBSA-N tamsulosin hydrochloride Chemical group [H+].[Cl-].CCOC1=CC=CC=C1OCCN[C@H](C)CC1=CC=C(OC)C(S(N)(=O)=O)=C1 ZZIZZTHXZRDOFM-XFULWGLBSA-N 0.000 claims description 3
- 230000000149 penetrating effect Effects 0.000 claims description 2
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- 238000002835 absorbance Methods 0.000 description 1
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- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007084 catalytic combustion reaction Methods 0.000 description 1
- 238000004587 chromatography analysis Methods 0.000 description 1
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- 230000008025 crystallization Effects 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
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- 238000002834 transmittance Methods 0.000 description 1
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Classifications
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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
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
-
- 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
-
- 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
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N2021/3595—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using FTIR
Abstract
The invention discloses a gas detection method based on chalcogenide glass suspension core optical fiber, which realizes gas detection by building a special gas detection platform, wherein the gas detection platform has a simple structure and is easy to build; the gas detection platform is built on the basis of a chalcogenide glass suspension core optical fiber gas sensor, has high sensitivity for detecting optical signals, can detect tiny spectral change, and can express the change of a light transmission spectrum by an visualized curve image; the detection method can be used for qualitatively and quantitatively analyzing and detecting various gases including gas, and can be widely applied to the fields of coal mine gas monitoring and early warning, coal mine natural ignition monitoring and early warning, toxic and harmful gas or dangerous gas monitoring and early warning and the like.
Description
Technical Field
The invention relates to the technical field of gas sensing, in particular to a gas detection method based on chalcogenide glass suspension core optical fibers.
Background
Energy is an important material basis for human survival and development, and is related to national civilization and national safety. In the process of exploiting and utilizing energy, safe production becomes an important subject in economic development. In recent years, the nation gives great attention to safety production, the total number of accidents in safety production is in a descending trend, but serious accidents are frequent and serious in harm.
In the coal field of China, gas and natural ignition are two main disasters in coal mine safety production. Aiming at gas disasters, a gas monitoring system is a main means for monitoring and early warning. The main problems of the current coal mine monitoring system are that the used catalytic combustion type sensor has the problems of poor reliability, frequent calibration, short service life, small measuring range and the like. The prediction and early warning of the natural fire of the coal mine mainly adopts a gas index analysis and prediction method. The traditional trace gas detection equipment for natural ignition is mainly a chromatographic analysis system, has the problems of complex equipment, complex operation, low analysis speed, incapability of realizing on-line monitoring and the like, and limits the application range of the equipment. With the technical progress, the improved beam tube system adopts an infrared analyzer to replace a part of spectrum analyzers, so that the detection speed is accelerated, but the defects are that the types of the measured gas are few, and the trace gas detection of olefins with large cross interference cannot be realized. Therefore, the defects of the existing detection technology limit the development of the coal mine gas monitoring technology and the fire prediction technology.
In the middle and far infrared, a large number of molecular fingerprint areas exist, and the molecular fingerprint areas comprise strong absorption areas of gases such as methane with relatively high content in gas. For example, according to the mid-infrared light transmission spectrum of the gas, the wavelength of 3.3 to 3.6 μm corresponds to a strong absorption region of methane gas in the mid-infrared, wherein the absorption intensity at the wavelength of 3.31 μm is 1300 times of the absorption intensity at 1.33 μm and 160 times of the absorption intensity at 1.66 μm. At present, the optical fiber gas sensor is mainly designed by adopting a quartz optical fiber for the spectral absorption of gas substances in a near infrared region (the wavelength is less than 2 μm), the detection wavelength range is limited, and cross response among gases is possibly introduced, so that the application of the optical fiber gas sensor in detection is limited.
Disclosure of Invention
The invention aims to solve the technical problem that the gas detection method based on the chalcogenide glass suspension core optical fiber can qualitatively and quantitatively analyze and detect various gases including gas, and can be widely applied to the fields of coal mine gas monitoring and early warning, coal mine natural ignition monitoring and early warning, toxic and harmful gas or dangerous gas monitoring and early warning and the like.
The technical scheme adopted by the invention for solving the technical problems is as follows: the gas detection method based on the chalcogenide glass suspension core optical fiber comprises the following steps:
(1) preparing a chalcogenide glass suspension core optical fiber, wherein the chalcogenide glass suspension core optical fiber comprises an outer tube, a suspension core and a plurality of spacers which are integrally arranged, the suspension core is suspended at the inner side of the outer tube, the suspension core is connected with the outer tube through the plurality of spacers, the plurality of spacers are positioned at the inner side of the outer tube and are arranged along the length direction of the outer tube, a plurality of rows of air holes are arranged on the tube wall of the outer tube, and each row of air holes are formed by a plurality of air holes which are arranged at intervals along the length direction of the outer tube;
(2) building a gas detection platform, wherein the gas detection platform comprises an FTIR spectrometer, a focusing lens, a first optical fiber clamp, a chalcogenide glass suspension core optical fiber, a gas chamber, a detector, an optical amplifier and a computer, the FTIR spectrometer, the focusing lens, the first optical fiber clamp, the gas chamber, the detector and the optical amplifier are sequentially built on the optical platform along the direction of a light path, the output end of the optical amplifier is connected with the FTIR spectrometer, the FTIR spectrometer is connected with the computer, the first optical fiber clamp is installed on a three-dimensional adjusting frame, then the chalcogenide glass suspension core optical fiber is fixed on the first optical fiber clamp, and the output end of the chalcogenide glass suspension core optical fiber passes through the gas chamber;
the gas chamber is of a hollow structure, the two sides of the gas chamber are respectively provided with an optical fiber inlet and an optical fiber outlet, the side wall of the gas chamber is provided with a plurality of gas inlets, the output end of the chalcogenide glass suspension core optical fiber passes through the optical fiber inlet and penetrates out of the optical fiber outlet, the input end of the chalcogenide glass suspension core optical fiber is over against the output end of the focusing lens, the output end of the chalcogenide glass suspension core optical fiber is over against the input end of the detector, and the computer is provided with LabVIEW software;
(3) vacuumizing the gas chamber, introducing a group of standard mixed gas into the gas chamber through the plurality of gas inlets, and sealing the gas chamber, wherein the group of standard mixed gas contains a plurality of gases with known concentrations and types; starting the gas detection platform, and recording the light transmission spectrums of various gases in the set of standard mixed gas by using LabVIEW software on the computer;
(4) repeating the step (3), and recording the light transmission spectrum of each gas in other groups of standard mixed gases by LabVIEW software, wherein the other groups of standard mixed gases contain the same type of gas but different concentrations of each gas in each group of standard mixed gases compared with the group of standard mixed gases in the step (3);
(5) LabVIEW software establishes standard transmission spectrums of different gases with different concentrations according to the light transmission spectrums of the various gases recorded in the steps (3) and (4);
(6) and (3) introducing the gas to be detected into the gas chamber through the plurality of gas inlets, recording the light transmission spectrum of the gas to be detected by LabVIEW software on the computer, and comparing the light transmission spectrum with the standard transmission spectrum established in the step (5) to obtain the type and concentration of the gas to be detected.
Preferably, the thickness of the tube wall of the outer tube of the chalcogenide glass suspended core optical fiber is 40 to 60 μm, the diameter of the air hole is 50 to 80 μm, and the distance between two adjacent air holes in the length direction of the outer tube is 10 to 40 μm.
Preferably, the tube wall of the outer tube of the chalcogenide glass suspension core optical fiber is provided with four rows of air holes, and the four rows of air holes are arranged at equal intervals along the circumferential direction of the outer tube.
Preferably, the gas chamber is connected with a vacuum extractor, rubber sealing rings are respectively arranged at an optical fiber inlet and an optical fiber outlet of the gas chamber, and the chalcogenide glass suspension core optical fiber is arranged on the two rubber sealing rings in a penetrating manner; rubber sealing plugs are respectively arranged at a plurality of gas inlets of the gas chamber. The rubber sealing ring and the rubber sealing plug can seal the gas chamber, a sealed gas environment is created for standard gas with known concentration in the detection environment, and the standard transmission spectrum is not easily interfered by the outside, so that the establishment of the standard transmission spectrum is facilitated.
Preferably, the detector is an MCT-A type HdCdTe detector manufactured by Thermo Scientific, USA.
Preferably, the LabVIEW software is OMNIC image processing software developed by Thermo Scientific, usa.
Preferably, the preparation process of the chalcogenide glass suspension core optical fiber comprises the following steps:
firstly, preparing a chalcogenide glass suspension core optical fiber semi-finished product by adopting an extrusion method for later use;
measuring and calculating the thickness of the outer tube wall of the chalcogenide glass suspension core optical fiber semi-finished product;
thirdly, an air hole processing platform is built, the air hole processing platform comprises a femtosecond laser, a half-wave plate, a Glan prism, an attenuation plate, an electronic shutter, a first small hole diaphragm, a dynamometer, a first beam splitter, a CCD (charge coupled device), a long tube eyepiece, a dichroic mirror, a illuminator, a second beam splitter, a second small hole diaphragm, a focusing objective lens, a second optical fiber clamp, a three-dimensional moving platform, a first bare fiber adapter, a second bare fiber adapter, a controller and a computer, the femtosecond laser, the half-wave plate, the Glan prism, the attenuation plate, the electronic shutter, the first small hole diaphragm, the first beam splitter, the dichroic mirror, the second beam splitter, the second small hole diaphragm, the focusing objective lens and the three-dimensional moving platform are built on the optical platform in sequence, the second optical fiber clamp is mounted on the three-dimensional moving platform, the electronic shutter is connected with the computer, and the three-dimensional moving platform is connected with the computer through the controller, simultaneously, the power meter is connected with the first beam splitter, the dichroic mirror is sequentially connected with the long tube ocular lens and the CCD, and the second beam splitter is connected with the illuminator;
fixing the chalcogenide glass suspension core optical fiber semi-finished product obtained by extrusion in the step one on the second optical fiber clamp, and then respectively connecting two ends of the chalcogenide glass suspension core optical fiber semi-finished product with the first bare fiber adapter and the second bare fiber adapter; adjusting the three-dimensional moving platform to enable the chalcogenide glass suspension core optical fiber semi-finished product to be in an aligned state, and then adjusting the pitching of the three-dimensional moving platform to enable the chalcogenide glass suspension core optical fiber semi-finished product to be on a flat surface, so as to ensure that the chalcogenide glass suspension core optical fiber semi-finished product can be clearly displayed on an imaging screen of the CCD; starting a femtosecond laser, adjusting a laser path, focusing a central light spot of the femtosecond laser by a focusing objective lens, vertically acting on the side wall of the chalcogenide glass suspension core optical fiber semi-finished product, simultaneously moving a three-dimensional moving platform up and down until the side wall of the chalcogenide glass suspension core optical fiber semi-finished product is perforated to obtain an air hole, then moving the three-dimensional moving platform left and right, and continuously perforating along the length direction of the side wall of the chalcogenide glass suspension core optical fiber semi-finished product to obtain a row of air holes; then, rotating the chalcogenide glass suspension core optical fiber semi-finished product by a certain angle, and repeatedly executing the punching operation to obtain another row of air holes; and repeating the rotating and punching operations until a finished chalcogenide glass suspension core optical fiber product is obtained.
The chalcogenide glass suspension core optical fiber used in the invention adopts the prior art As the material of chalcogenide glass raw material used for the semi-finished product, and the suspension core adopts high-purity chalcogenide glass such As As2S3、As2Se3Ge-As-Se, Ge-As-S and the like, the material of the outer tube can be the same As or different from that of the hanging core, but the requirement on the purity of the outer tube is relatively low, and the purification treatment can not be carried out in advance. The chalcogenide glass suspension core optical fiber semi-finished product is prepared by the existing extrusion method, so that impurities are not introduced, the crystallization phenomenon is not caused, the surface smoothness is high, and the scattering loss of the sensor can be effectively reduced. In the preparation process of the chalcogenide glass suspension core optical fiber,the punching operation of the air holes on the pipe wall of the outer pipe is realized by building an air hole processing platform. The air hole processing platform is simple in construction method, convenient to punch, free of other extra processing on the optical fiber during punching, and capable of accurately controlling the aperture, the row number and the interval of the air holes.
Compared with the prior art, the invention has the following advantages:
1. the chalcogenide glass suspension core optical fiber used by the gas detection method has a wide transmission spectrum of 1-20 mu m and ultrahigh nonlinearity, and can realize high-sensitivity detection on gas; the hanging core bare fiber of the chalcogenide glass hanging core optical fiber is protected by the outer tube, the reliability is good, and the air hole formed in the outer tube is beneficial to the gas to be detected to rapidly penetrate through the outer tube to be directly contacted with the bare fiber in the outer tube, so that the high sensitivity is ensured, and the accuracy of a detection result is ensured;
2. according to the gas detection method, the gas detection is realized by building a special gas detection platform, the built gas detection platform is simple in structure and easy to build, a special gas chamber is designed to effectively protect the chalcogenide glass suspension core optical fiber, and the type of the gas can be distinguished and the concentration can be measured according to different wavelength ranges corresponding to strong absorption areas corresponding to the gas to be detected; the gas detection platform is built on the basis of a chalcogenide glass suspension core optical fiber gas sensor, has high sensitivity for detecting optical signals, can detect tiny spectral change, and can express the change of a light transmission spectrum by an visualized curve image; the gas detection method can perform qualitative and quantitative analysis and detection on various gases including gas, and can be widely applied to the fields of coal mine gas monitoring and early warning, coal mine natural ignition monitoring and early warning, toxic and harmful gas or dangerous gas monitoring and early warning and the like.
Drawings
FIG. 1 is a schematic view showing the appearance of a chalcogenide glass suspension core optical fiber used in the examples;
FIG. 2 is a schematic cross-sectional view of a chalcogenide glass suspension core optical fiber used in the examples;
FIG. 3 is a schematic structural connection diagram of a gas detection platform constructed in the embodiment;
FIG. 4 is a schematic structural connection diagram of an air hole machining platform constructed in the embodiment;
FIG. 5 is a graph of the permeability of different concentrations of methane;
FIG. 6 is a graph showing the relationship between the transmittance and the methane concentration.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
The gas detection method based on the chalcogenide glass suspension core optical fiber of embodiment 1 includes the following steps:
(1) a chalcogenide glass suspension core optical fiber 1 is prepared, as shown in FIGS. 1 and 2, the chalcogenide glass suspension core optical fiber 1 comprises an outer tube 11, a suspension core 12 and four spacers 13, which are integrally arranged, in this embodiment 1, GeAs is used for the outer tube 1139Se60Chalcogenide glass, the hanging core 1212 is As40Se60Chalcogenide glass, the external diameter of the outer tube 11 is 320 μm, the wall thickness of the tube is 50 μm, the hanging core 12 is suspended inside the outer tube 11, the hanging core 12 is connected with the outer tube 11 through four spacers 13, the four spacers 13 are located inside the outer tube 11 and arranged along the length direction of the outer tube 11, four rows of air holes are arranged on the wall of the outer tube 11, the four rows of air holes are arranged along the circumference of the outer tube 11 at equal intervals, and each row of air holes is composed of a plurality of air holes 14 with the aperture of 50 μm arranged along the length direction of the outer tube 11 at equal intervals; the distance between two air holes 14 adjacent in the length direction of the outer tube 11 is 20 μm;
(2) a gas detection platform is set up, as shown in fig. 3, the gas detection platform comprises an FTIR spectrometer 61, a focusing lens 62, a first optical fiber clamp 63, a chalcogenide glass suspended core optical fiber 1, a gas chamber 7, a detector 81, an optical amplifier 82 and a computer 83, the FTIR spectrometer 61, the focusing lens 62, the first optical fiber clamp 63, the gas chamber 7, the detector 81 and the optical amplifier 82 are set up on the optical platform along the direction of an optical path in sequence, the output end of the optical amplifier 82 is connected with the FTIR spectrometer 61, the FTIR spectrometer 61 is connected with the computer 83, the first optical fiber clamp 63 is mounted on a three-dimensional adjusting frame 64, then the chalcogenide glass suspended core optical fiber 1 is fixed on the first optical fiber clamp 63, and the output end of the chalcogenide glass suspended core optical fiber 1 passes through the gas chamber 7;
the gas chamber 7 is a hollow structure, in this embodiment 1, the gas chamber 7 is a cylindrical structure with a length of 5cm and a cross-sectional diameter of 2cm, two sides of the gas chamber 7 are respectively provided with an optical fiber inlet 71 and an optical fiber outlet 72, a gas inlet a is formed in a side wall of the gas chamber 7, an output end of the chalcogenide glass suspension core optical fiber 1 passes through the optical fiber inlet 71 and penetrates out of the optical fiber outlet 72, an input end of the chalcogenide glass suspension core optical fiber 1 is opposite to an output end of the focusing lens 62, an output end of the chalcogenide glass suspension core optical fiber 1 is opposite to an input end of the detector 81, and the computer 83 is provided with LabVIEW software;
(3) vacuumizing the gas chamber 7, introducing a group of standard mixed gas into the gas chamber 7 through a gas inlet A, and sealing the gas chamber 7, wherein the group of standard mixed gas contains a plurality of gases with known concentrations and types; starting a gas detection platform, and recording the light transmission spectrums of various gases in the set of standard mixed gas by using LabVIEW software on a computer 83;
(4) repeating the step (3), and recording the light transmission spectrum of each gas in other groups of standard mixed gases by LabVIEW software, wherein the other groups of standard mixed gases contain the same type of gas but different concentrations of each gas in each group of standard mixed gases compared with the group of standard mixed gases in the step (3);
(5) LabVIEW software establishes standard transmission spectrums of different gases with different concentrations according to the light transmission spectrums of the various gases recorded in the steps (3) and (4);
(6) and (3) introducing the gas to be detected into the gas chamber 7 through the gas inlet A, recording the light transmission spectrum of the gas to be detected by LabVIEW software on the computer 83, and comparing the light transmission spectrum with the standard transmission spectrum established in the step (5) to obtain the type and concentration of the gas to be detected.
In this mutexample 1, the probe 81 is an MCT-a type HdCdTe probe manufactured by Thermo Scientific, usa, the LabVIEW software is OMNIC image processing software developed by Thermo Scientific, usa, and the focusing lens 62 is a ZnS focusing lens.
The chalcogenide glass suspension core optical fiber 1 used in this example 1 was prepared by the following steps:
firstly, preparing a chalcogenide glass suspension core optical fiber semi-finished product 10 by adopting an extrusion method for later use;
measuring and calculating the thickness of the tube wall of the outer tube 11 of the chalcogenide glass suspension core optical fiber semi-finished product 10;
thirdly, an air hole 14 processing platform is set up, as shown in fig. 4, the air hole 14 processing platform comprises a femtosecond laser 2, a half-wave plate 31, a glan prism 32, an attenuation plate 33, an electronic shutter 34, a first small hole diaphragm 35, a dynamometer 37, a first beam splitter 36, a CCD 43, a long tube eyepiece 42, a dichroic mirror 41, an illuminator 45, a second beam splitter 44, a second small hole diaphragm 46, a focusing objective 47, a second optical fiber clamp 51, a three-dimensional moving platform 5, a first bare fiber adapter 52, a second bare fiber adapter 53, a controller 54 and a computer 55, the femtosecond laser 2, the half-wave plate 31, the glan prism 32, the attenuation plate 33, the electronic shutter 34, the first small hole diaphragm 35, the first beam splitter 36, the dichroic mirror 41, the second beam splitter 44, the second small hole diaphragm 46, the focusing objective 47 and the three-dimensional moving platform 5 are set up on the optical platform in turn, the second optical fiber clamp 51 is set up on the three-dimensional moving platform 5, connecting the electronic shutter 34 with a computer 55, connecting the three-dimensional mobile platform 5 with the computer 55 through a controller 54, simultaneously connecting a power meter 37 with a first beam splitter 36, sequentially connecting a dichroic mirror 41 with a long-tube ocular lens 42 and a CCD 43, and connecting a second beam splitter 44 with an illuminator 45;
fixing the chalcogenide glass suspension core optical fiber semi-finished product 10 obtained by extrusion in the step (I) on a second optical fiber clamp 51, and then respectively connecting two ends of the chalcogenide glass suspension core optical fiber semi-finished product 10 with a first bare fiber adapter 52 and a second bare fiber adapter 53; adjusting the three-dimensional moving platform 5 to enable the chalcogenide glass suspension core optical fiber semi-finished product 10 to be in a collimation state, and then adjusting the pitching of the three-dimensional moving platform 5 to enable the chalcogenide glass suspension core optical fiber semi-finished product 10 to be on a flat surface, so as to ensure that the chalcogenide glass suspension core optical fiber semi-finished product 10 can be clearly displayed on an imaging screen of the CCD 43; starting a femtosecond laser 2, adjusting a laser light path, focusing a central light spot of the femtosecond laser 2 through a focusing objective lens 47, vertically acting on the side wall of the chalcogenide glass suspension core optical fiber semi-finished product 10, simultaneously moving a three-dimensional moving platform 5 up and down until the side wall of the chalcogenide glass suspension core optical fiber semi-finished product 10 is perforated to obtain an air hole 14, then moving the three-dimensional moving platform 5 left and right, and continuously perforating every 20 micrometers along the length direction of the side wall of the chalcogenide glass suspension core optical fiber semi-finished product 10 to obtain a row of air holes; then, rotating the chalcogenide glass suspension core optical fiber semi-finished product 10 by 90 degrees, and repeatedly executing the punching operation to obtain another row of air holes; the rotation and punching operations are repeated until a finished chalcogenide glass suspended core optical fiber 1 is obtained, the appearance schematic diagram of which is shown in figure 1, and the cross-sectional schematic diagram of which is shown in figure 2.
When the air hole processing platform works, the power of laser pulse energy is firstly adjusted through a half-wave plate 31, a Glan prism 32 and an attenuation plate 33, and the power of the laser pulse is adjusted to 24 MW; then, the light enters an electronic shutter 34, the exposure time is controlled, and stray light in a light path is removed through a first aperture diaphragm 35, so that the beam quality is improved; then the femtosecond laser is divided into reflected light and transmitted light by a first beam splitter 36, wherein the reflected light enters a power meter 37, the power meter 37 detects the power of the femtosecond laser, the transmitted light is transmitted to a dichroic mirror 41, the femtosecond laser is reflected to a second beam splitter 44 by the dichroic mirror 41, meanwhile, the light of an illuminator 45 is also irradiated on the second beam splitter 44, the femtosecond laser and the illumination light are respectively divided into two beams by the second beam splitter 44, namely a downward beam and an upward beam transmitted through the second beam splitter 44, wherein the downward beam further improves the beam quality through a second small aperture diaphragm 46, and is acted on the side wall of the chalcogenide glass suspension core fiber semi-finished product 10 arranged on the three-dimensional moving platform 5 through a focusing objective 47 to perform punching operation, and the light reflected by the chalcogenide glass suspension core fiber semi-finished product 10 enters a CCD 43 through the dichroic mirror 41 and a long tube 42 together with the upward beam transmitted through the second beam splitter 44 The drilling process of the femtosecond laser is monitored by the CCD 43 in real time.
In the working process of the gas detection platform, a broadband infrared light source emitted by the FTIR spectrometer 61 is coupled through the ZnS focusing lens 62 in a focusing manner, and the broadband infrared light output by the ZnS focusing lens 62 is collimated and input into the chalcogenide glass suspension core optical fiber 1. The gas to be detected permeates into the chalcogenide glass suspension core optical fiber 1 through the air hole 14 on the chalcogenide glass suspension core optical fiber 1, the gas to be detected generates absorption with specific wavelength on the light transmitted in the optical fiber 1, the light output from the output end of the chalcogenide glass suspension core optical fiber 1 is detected by the detector 81, the detection signal is amplified and returns to the FTIR spectrometer 61, and LabVIEW software on the computer 83 records the light transmission spectrum.
The wavelength ranges corresponding to the strong absorption areas corresponding to each gas to be detected are different, so that the gas detection method can distinguish the gas types, and in addition, the gas concentrations are different, the absorbance of light is different, so that the gas detection method can realize high-sensitivity measurement of the gas concentrations. The gas detection method can qualitatively and quantitatively analyze and detect various gases including gas, and can be widely applied to the fields of coal mine gas monitoring and early warning, coal mine natural ignition monitoring and early warning, toxic and harmful gas or dangerous gas monitoring and early warning and the like.
The difference between the method for detecting gas based on a chalcogenide glass suspended core optical fiber in example 2 and example 1 is that in example 2, a vacuum pumping device (for example, a vacuum pump, not shown) is connected to the gas chamber 7, rubber sealing rings (not shown) are respectively installed at the optical fiber inlet 71 and the optical fiber outlet 72 of the gas chamber 7, the chalcogenide glass suspended core optical fiber 1 is inserted into the two rubber sealing rings, and a rubber sealing plug 73 is installed at the gas inlet a of the gas chamber 7. The gas chamber 7 can be sealed by the rubber sealing ring and the rubber sealing plug 73, a sealed gas environment is created for standard gas with known concentration in the detection environment, and the standard transmission spectrum is not easily interfered by the outside, so that the establishment of the standard transmission spectrum is facilitated. In the step (3) and the step (4), after the gas chamber 7 is vacuumized by the vacuumizing device, the standard mixed gas is introduced into the gas chamber 7 through the gas inlet a, and the gas inlet a is closed by the rubber sealing plug 73. It should be noted that the gas chamber 7 is closed only after the standard mixed gas is introduced into the gas chamber 7 during the process of establishing the standard transmission spectrum of different gases with different concentrations. In the actual detection process (i.e. in step (6)), the gas chamber 7 is not required to be closed, but the chalcogenide glass suspension core optical fiber is directly exposed to the detection environment, so that the gas to be detected directly enters the gas chamber and permeates into the chalcogenide glass suspension core optical fiber through air holes on the chalcogenide glass suspension core optical fiber, the gas to be detected can absorb light transmitted in the chalcogenide glass suspension core optical fiber with a specific wavelength, the light output by the output end of the chalcogenide glass suspension core optical fiber is detected by a detector, a detection signal is amplified and returns to an FTIR spectrometer, LabVIEW software on a computer records a light transmission spectrum, and the type and the concentration of the gas to be detected are obtained by comparing the light transmission spectrum with pre-established standard transmission spectra of gases with different concentrations.
In example 2, the process of establishing the standard transmission spectrum from step (3) to step (5) is exemplified by methane, for example: gas with methane volume concentration of 1.5% is introduced into the gas chamber 7 through the gas inlet A, the gas inlet A is sealed with the rubber sealing plug 73, the time is 10 minutes, and the light transmission spectrum at the methane concentration is recorded by LabVIEW software on the computer 83. The above operations are repeated, and the light transmission spectra under other different methane concentrations (the methane volume concentrations in the gas are respectively 6%, 10% and 14%) are respectively detected and recorded. The standard transmission spectra at different methane concentrations are shown in fig. 5 and fig. 6, wherein fig. 5 is a transmission curve of methane at different concentrations, and fig. 6 is a graph of transmission rate and methane concentration. In fig. 6, the volume concentrations of methane corresponding to five curves from top to bottom are 0, 1.5%, 6%, 10%, and 14%, respectively.
Claims (7)
1. The gas detection method based on the chalcogenide glass suspension core optical fiber is characterized by comprising the following steps of:
(1) preparing a chalcogenide glass suspension core optical fiber, wherein the chalcogenide glass suspension core optical fiber comprises an outer tube, a suspension core and a plurality of spacers which are integrally arranged, the suspension core is suspended at the inner side of the outer tube, the suspension core is connected with the outer tube through the plurality of spacers, the plurality of spacers are positioned at the inner side of the outer tube and are arranged along the length direction of the outer tube, a plurality of rows of air holes are arranged on the tube wall of the outer tube, and each row of air holes are formed by a plurality of air holes which are arranged at intervals along the length direction of the outer tube;
(2) building a gas detection platform, wherein the gas detection platform comprises an FTIR spectrometer, a focusing lens, a first optical fiber clamp, a chalcogenide glass suspension core optical fiber, a gas chamber, a detector, an optical amplifier and a computer, the FTIR spectrometer, the focusing lens, the first optical fiber clamp, the gas chamber, the detector and the optical amplifier are sequentially built on the optical platform along the direction of a light path, the output end of the optical amplifier is connected with the FTIR spectrometer, the FTIR spectrometer is connected with the computer, the first optical fiber clamp is installed on a three-dimensional adjusting frame, then the chalcogenide glass suspension core optical fiber is fixed on the first optical fiber clamp, and the output end of the chalcogenide glass suspension core optical fiber passes through the gas chamber;
the gas chamber is of a hollow structure, the two sides of the gas chamber are respectively provided with an optical fiber inlet and an optical fiber outlet, the side wall of the gas chamber is provided with a plurality of gas inlets, the output end of the chalcogenide glass suspension core optical fiber passes through the optical fiber inlet and penetrates out of the optical fiber outlet, the input end of the chalcogenide glass suspension core optical fiber is over against the output end of the focusing lens, the output end of the chalcogenide glass suspension core optical fiber is over against the input end of the detector, and the computer is provided with LabVIEW software;
(3) vacuumizing the gas chamber, introducing a group of standard mixed gas into the gas chamber through the plurality of gas inlets, and sealing the gas chamber, wherein the group of standard mixed gas contains a plurality of gases with known concentrations and types; starting the gas detection platform, and recording the light transmission spectrums of various gases in the set of standard mixed gas by using LabVIEW software on the computer;
(4) repeating the step (3), and recording the light transmission spectrum of each gas in other groups of standard mixed gases by LabVIEW software, wherein the other groups of standard mixed gases contain the same type of gas but different concentrations of each gas in each group of standard mixed gases compared with the group of standard mixed gases in the step (3);
(5) LabVIEW software establishes standard transmission spectrums of different gases with different concentrations according to the light transmission spectrums of the various gases recorded in the steps (3) and (4);
(6) and (3) introducing the gas to be detected into the gas chamber through the plurality of gas inlets, recording the light transmission spectrum of the gas to be detected by LabVIEW software on the computer, and comparing the light transmission spectrum with the standard transmission spectrum established in the step (5) to obtain the type and concentration of the gas to be detected.
2. The method according to claim 1, wherein the chalcogenide glass suspension core optical fiber has an outer tube with a wall thickness of 40 to 60 μm, the air holes have a diameter of 50 to 80 μm, and the distance between two adjacent air holes in the longitudinal direction of the outer tube is 10 to 40 μm.
3. The method according to claim 1, wherein four rows of air holes are formed in the wall of the outer tube of the chalcogenide glass suspension core optical fiber, and the four rows of air holes are arranged at equal intervals along the circumferential direction of the outer tube.
4. The gas detection method based on the chalcogenide glass suspension core optical fiber as claimed in claim 1, wherein the gas chamber is connected with a vacuum pumping device, rubber sealing rings are respectively installed at the optical fiber inlet and the optical fiber outlet of the gas chamber, and the chalcogenide glass suspension core optical fiber is arranged on the two rubber sealing rings in a penetrating manner; rubber sealing plugs are respectively arranged at a plurality of gas inlets of the gas chamber.
5. The chalcogenide glass suspended core fiber-based gas detection method according to claim 1, wherein the detector is an MCT-a type HdCdTe detector manufactured by Thermo Scientific, usa.
6. The chalcogenide glass suspension core fiber-based gas detection method according to claim 1, wherein the LabVIEW software is OMNIC image processing software developed by Thermo Scientific, usa.
7. The gas detection method based on the chalcogenide glass suspension core optical fiber according to claim 1, characterized in that the chalcogenide glass suspension core optical fiber is prepared by the following steps:
firstly, preparing a chalcogenide glass suspension core optical fiber semi-finished product by adopting an extrusion method for later use;
measuring and calculating the thickness of the outer tube wall of the chalcogenide glass suspension core optical fiber semi-finished product;
thirdly, an air hole processing platform is built, the air hole processing platform comprises a femtosecond laser, a half-wave plate, a Glan prism, an attenuation plate, an electronic shutter, a first small hole diaphragm, a dynamometer, a first beam splitter, a CCD (charge coupled device), a long tube eyepiece, a dichroic mirror, a illuminator, a second beam splitter, a second small hole diaphragm, a focusing objective lens, a second optical fiber clamp, a three-dimensional moving platform, a first bare fiber adapter, a second bare fiber adapter, a controller and a computer, the femtosecond laser, the half-wave plate, the Glan prism, the attenuation plate, the electronic shutter, the first small hole diaphragm, the first beam splitter, the dichroic mirror, the second beam splitter, the second small hole diaphragm, the focusing objective lens and the three-dimensional moving platform are built on the optical platform in sequence, the second optical fiber clamp is mounted on the three-dimensional moving platform, the electronic shutter is connected with the computer, and the three-dimensional moving platform is connected with the computer through the controller, simultaneously, the power meter is connected with the first beam splitter, the dichroic mirror is sequentially connected with the long tube ocular lens and the CCD, and the second beam splitter is connected with the illuminator;
fixing the chalcogenide glass suspension core optical fiber semi-finished product obtained by extrusion in the step one on the second optical fiber clamp, and then respectively connecting two ends of the chalcogenide glass suspension core optical fiber semi-finished product with the first bare fiber adapter and the second bare fiber adapter; adjusting the three-dimensional moving platform to enable the chalcogenide glass suspension core optical fiber semi-finished product to be in an aligned state, and then adjusting the pitching of the three-dimensional moving platform to enable the chalcogenide glass suspension core optical fiber semi-finished product to be on a flat surface, so as to ensure that the chalcogenide glass suspension core optical fiber semi-finished product can be clearly displayed on an imaging screen of the CCD; starting a femtosecond laser, adjusting a laser path, focusing a central light spot of the femtosecond laser by a focusing objective lens, vertically acting on the side wall of the chalcogenide glass suspension core optical fiber semi-finished product, simultaneously moving a three-dimensional moving platform up and down until the side wall of the chalcogenide glass suspension core optical fiber semi-finished product is perforated to obtain an air hole, then moving the three-dimensional moving platform left and right, and continuously perforating along the length direction of the side wall of the chalcogenide glass suspension core optical fiber semi-finished product to obtain a row of air holes; then, rotating the chalcogenide glass suspension core optical fiber semi-finished product by a certain angle, and repeatedly executing the punching operation to obtain another row of air holes; and repeating the rotating and punching operations until a finished chalcogenide glass suspension core optical fiber product is obtained.
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| CN202957448U (en) * | 2012-09-14 | 2013-05-29 | 北京工业大学 | Middle and far-infrared super-continuum spectrum fiber laser |
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| CN105552699B (en) * | 2016-01-15 | 2018-10-02 | 宁波大学 | A kind of production method of far infrared super continuous spectrums |
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