CN113589426A - Hollow optical fiber, gas detection system and method - Google Patents
Hollow optical fiber, gas detection system and method Download PDFInfo
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- 238000001514 detection method Methods 0.000 title claims abstract description 76
- 239000013307 optical fiber Substances 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title abstract description 15
- 239000000835 fiber Substances 0.000 claims abstract description 80
- 238000005253 cladding Methods 0.000 claims abstract description 63
- 238000010168 coupling process Methods 0.000 claims abstract description 35
- 238000005859 coupling reaction Methods 0.000 claims abstract description 33
- 230000008878 coupling Effects 0.000 claims abstract description 32
- 238000000862 absorption spectrum Methods 0.000 claims abstract description 24
- 230000010365 information processing Effects 0.000 claims abstract description 20
- 230000003595 spectral effect Effects 0.000 claims abstract description 14
- 230000005540 biological transmission Effects 0.000 claims abstract description 12
- 239000012466 permeate Substances 0.000 claims abstract description 12
- 238000001228 spectrum Methods 0.000 claims abstract description 9
- 238000004458 analytical method Methods 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims description 15
- 239000012510 hollow fiber Substances 0.000 claims description 7
- 229920000089 Cyclic olefin copolymer Polymers 0.000 claims description 6
- 229920000620 organic polymer Polymers 0.000 claims description 5
- -1 polyethylene Polymers 0.000 claims description 5
- 230000001681 protective effect Effects 0.000 claims description 5
- 229920001169 thermoplastic Polymers 0.000 claims description 4
- 239000004416 thermosoftening plastic Substances 0.000 claims description 4
- 239000004713 Cyclic olefin copolymer Substances 0.000 claims description 3
- 239000004698 Polyethylene Substances 0.000 claims description 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 125000004122 cyclic group Chemical group 0.000 claims description 2
- 239000004519 grease Substances 0.000 claims description 2
- 238000004891 communication Methods 0.000 claims 2
- 239000007789 gas Substances 0.000 description 107
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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
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02295—Microstructured optical fibre
- G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
- G02B6/02319—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by core or core-cladding interface features
- G02B6/02323—Core having lower refractive index than cladding, e.g. photonic band gap guiding
- G02B6/02328—Hollow or gas filled core
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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
- G01N21/17—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
- G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation
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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
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/02295—Microstructured optical fibre
- G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
- G02B6/02342—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by cladding features, i.e. light confining region
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
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Abstract
The invention provides a hollow optical fiber, a gas detection system and a method, wherein the gas detection system comprises: the terahertz wave detection device comprises a terahertz wave generating device, a terahertz wave detecting device, a coupling device, a spectrum information processing device and a hollow optical fiber; the terahertz wave generating device is used for generating terahertz waves to be incident into the coupling device; the coupling device is connected with one end of the hollow optical fiber and is used for coupling the terahertz waves and the gas to be detected into the fiber core and the cladding of the hollow optical fiber respectively so that the terahertz waves react with the gas to be detected which permeates into the fiber core from the cladding in the transmission process of the fiber core and are output from the other end of the fiber core; the terahertz wave detection device detects terahertz waves output from the fiber core, obtains an absorption spectrum of the gas to be detected and sends the absorption spectrum to the spectral information processing device; and the spectral information processing device is used for obtaining an analysis result according to the absorption spectrum of the gas to be detected. This scheme can reduce gaseous detecting system's volume and improve gaseous detection efficiency.
Description
Technical Field
The embodiment of the invention relates to the technical field of detection, in particular to a hollow optical fiber, a gas detection system and a gas detection method.
Background
In the prior art, methods for detecting gas components included in a mixed gas and the content of each gas component generally include colorimetry, chromatography, spectrophotometry, and the like. The gas components which can be detected by the existing detection method are single, and the detection system is large in size.
Disclosure of Invention
The embodiment of the invention provides a hollow optical fiber, a gas detection system and a method, which can reduce the volume of the gas detection system and improve the gas detection efficiency.
In a first aspect, an embodiment of the present invention provides a hollow core optical fiber, including: the optical fiber comprises a fiber core, a cladding surrounding the inner wall of the fiber core and a protective sleeve outside the cladding; the inner wall comprises a plurality of vent holes.
Preferably, the fiber core is hollow and filled with dry air.
Preferably, the cladding layer is made of a material having a refractive index greater than 1.
Preferably, a plurality of organic structure bodies are embedded in the cladding, and the material of the organic structure bodies is a thermoplastic organic polymer with low loss in the terahertz wave frequency band.
Preferably, the cross-sectional shape of the organic structure is at least one of a strip shape, a ring shape and a round shape; and/or the presence of a gas in the gas,
the material of the organic structure is at least one of polyethylene, cyclic olefin copolymer and polymer cyclic grease.
Preferably, gaps are arranged among the plurality of organic structures embedded in the cladding, and the gaps in the cladding are communicated with the fiber core through the vent holes in the inner wall.
Preferably, one end of the hollow core fiber comprises a core inlet and a cladding inlet; the other end of the hollow fiber comprises a fiber core outlet.
In a second aspect, an embodiment of the present invention provides a gas detection system, including a terahertz wave generating device, a terahertz wave detecting device, a coupling device, a spectral information processing device, and a hollow optical fiber as described in any one of the above;
the terahertz wave generating device is used for generating terahertz waves, and the generated terahertz waves are incident into the coupling device;
the coupling device is connected with one end of the hollow optical fiber and is used for coupling incident terahertz waves and collected gas to be detected into a fiber core and a cladding of the hollow optical fiber respectively so as to enable the terahertz waves to react with the gas to be detected which permeates into the fiber core from the cladding in the transmission process of the terahertz waves in the fiber core and to be output from the other end of the fiber core;
the terahertz wave detection device is used for detecting terahertz waves output from the fiber core to obtain an absorption spectrum of the gas to be detected and sending the absorption spectrum of the gas to be detected to the spectrum information processing device;
and the spectral information processing device is used for obtaining an analysis result according to the absorption spectrum of the gas to be detected.
Preferably, the coupling device includes an incident port for receiving the terahertz wave and an air suction port for receiving the gas to be measured, the incident port is communicated with a core inlet of the hollow optical fiber, and the air suction port is communicated with a cladding inlet of the hollow optical fiber.
In a third aspect, an embodiment of the present invention provides a gas detection method based on any one of the above gas detection systems, including:
generating terahertz waves by utilizing a terahertz generating device, and enabling the generated terahertz waves to be incident into a coupling device;
the terahertz wave and the gas to be detected are respectively coupled into the fiber core and the cladding of the hollow optical fiber by using the coupling device, so that the terahertz wave reacts with the gas to be detected which permeates into the fiber core from the cladding in the internal transmission process and is output from the other end of the fiber core;
detecting terahertz waves output from the fiber core by using a terahertz wave detection device to obtain an absorption spectrum of the gas to be detected, and sending the absorption spectrum of the gas to be detected to the spectrum information processing device;
and obtaining an analysis result by utilizing the spectral information processing device according to the absorption spectrum of the gas to be detected.
The embodiment of the invention provides a hollow optical fiber, a gas detection system and a gas detection method, wherein the hollow optical fiber is used as a reaction cavity for terahertz waves and gas to be detected, the terahertz waves can fully react with the gas to be detected in the transmission process of the hollow optical fiber, and the hollow optical fiber can be bent, so that even if the length of the hollow optical fiber is longer, the hollow optical fiber can occupy smaller space through bending, and the volume of the gas detection system can be reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of a hollow core optical fiber according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a gas detection system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another gas detection system according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a time delay line structure according to an embodiment of the present invention;
FIG. 5 is a flow chart of a gas detection method according to an embodiment of the present invention;
the reference signs are:
1-a fiber core; 11-inner wall; 2-a cladding layer; 21-a structure; 3-protecting the jacket; 201-a terahertz wave generating device; 202-a terahertz wave detection device; 203-coupling means; 204-spectral information processing means; 205-hollow fiber; 206-gas collection box; 207-gas circulation pump; 208-an alarm unit; 209-display; 2011-femtosecond laser; 2012-beam splitter; 2013-time delay line; 2014-polarization maintaining fiber; 2015-a photoconductive antenna; 2021-photoconductive detection antenna; a1 — pulse input port; A2-A4-reflector; a 5-pulse output port; a6-roller guide.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention, and based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the scope of the present invention.
As described above, the method of detecting the gas components included in the mixed gas and the contents of the respective gas components generally includes colorimetry, chromatography, spectrophotometry, and the like. Terahertz (THz for short) waves refer to electromagnetic waves with the frequency of 0.1-10THz and the wavelength of 0.03-3mm, the wave band is between microwave and far infrared, and the Terahertz (THz) waves are in the edge frequency spectrum region of traditional electronics and photonics research and are also transition regions from classical macroscopic theory to quantum microscopic theory. The terahertz wave band is in the range of the rotation frequency and the vibration energy level of most macromolecules, and the terahertz wave interacts with substances and can reflect abundant physical and chemical information of the substances, so that the terahertz wave has huge development prospect and application potential in the aspects of substance detection and identification. In recent years, with the development of scientific technology, terahertz waves have made important progress in the detection, identification, sensing and the like of harmful gases in the atmospheric environment. When the terahertz wave is used for detecting gas components, the gas to be detected is generally filled into a spherical reaction cavity, and the terahertz wave and the gas to be detected react in the spherical reaction cavity. But the reaction cavity has larger volume, and the existing gas detection system has poorer portability. Considering that the terahertz waves can be transmitted in the hollow optical fiber and can be freely bent and folded, if the gas to be detected can be filled into the hollow optical fiber, the terahertz waves react with the gas to be detected in the transmission process of the hollow optical fiber, namely the hollow optical fiber is used as a reaction cavity, and when the length of the hollow optical fiber is the same as the diameter of the existing reaction cavity, the hollow optical fiber is bent, so that the volume of the reaction cavity can be reduced, the volume of a gas detection system is further reduced, and the portability of the gas detection system is improved.
Specific implementations of the above concepts are described below.
Referring to fig. 1, an embodiment of the present invention provides a hollow core optical fiber, including a fiber core 1, a cladding 2 surrounding an inner wall 11 of the fiber core 1, and a protective jacket 3 outside the cladding 2; the inner wall 11 includes a plurality of vent holes.
In the embodiment of the invention, the fiber core is used for transmitting the terahertz waves, the gas to be detected can enter the hollow fiber through the cladding, then permeate into the fiber core through the vent hole on the inner wall, fully react with the gas to be detected permeating into the fiber core along with the increase of the transmission distance of the terahertz waves in the fiber core, and then output from the other end of the hollow fiber, so that the output terahertz waves can be detected by utilizing a terahertz wave detection device, and the detection of the components of the gas to be detected is realized.
In one embodiment of the invention, the protective sleeve not only can protect the hollow optical fiber, but also can block the gas to be detected, so that the gas to be detected can be filled into the cladding and can not be diffused to the outside of the hollow optical fiber, and the gas to be detected can permeate into the fiber core through the vent holes in the inner wall of the fiber core under the action of pressure.
In an embodiment of the present invention, when the terahertz wave is transmitted in the atmospheric environment, the terahertz wave is easily absorbed by the atmosphere due to the reason that the humidity of the atmospheric environment is high, and the like, so that in order to reduce the absorption of the terahertz wave by the atmosphere, dry air is filled in the fiber core, and when the terahertz wave is transmitted in the fiber core, the air in the fiber core is dry, so that compared with the terahertz wave transmitted in the atmospheric environment, the amount of absorption can be reduced, so that the accuracy of the spectral information of the terahertz wave detected by the terahertz wave detecting device at the other end of the hollow fiber is high, and the accuracy of the detection result is further improved.
In one embodiment of the invention, the equivalent refractive index of the cladding is greater than the refractive index in the core. In order to prevent the terahertz waves from leaking to the outside of the fiber core in the transmission process, the equivalent refractive index of the cladding is larger than that of the fiber core, so that the terahertz waves can be limited in the fiber core.
When the gas in the core is air, then the refractive index in the core is 1. Thus, it is necessary to make the equivalent refractive index in the cladding larger than 1. I.e. the equivalent refractive index of the cladding material is greater than 1.
Considering that the cladding layer can also absorb the terahertz waves, in order to reduce the absorption amount of the cladding layer to the terahertz waves, the material of the cladding layer can be a thermoplastic organic polymer with low loss in the frequency band of the terahertz waves.
In addition, in consideration of the fact that if the cladding is filled with the cladding material, that is, the gap between the inner wall of the fiber core and the protective sleeve is filled with the cladding material, not only is the weight of the hollow optical fiber large, but also the absorption of the terahertz wave by more cladding materials is large, therefore, in order to further reduce the absorption of the terahertz wave by the cladding, in one embodiment of the present invention, a plurality of organic structures 21 are embedded in the cladding 2, and the material of the organic structures 21 is a thermoplastic organic polymer with low loss in the terahertz wave frequency band.
Because the refractive index of the organic polymer is larger than 1, the plurality of organic structures are embedded in the cladding, so that the equivalent refractive index in the cladding is larger than 1, namely larger than the refractive index of air in the fiber core, and the cladding can play a role in limiting terahertz waves.
In one embodiment of the present invention, the material of the organic structure may be at least one of polyethylene, cyclic olefin copolymer, and polymer cyclic ester. Further, for example, polytetrafluoroethylene, polycarbonate, polystyrene, or the like may be used.
In one embodiment of the present invention, the cross-sectional shape of the organic structure is at least one of a stripe shape, a ring shape, and a circular shape. Referring to fig. 1, the organic structure is a structure in which an elliptical ring is embedded in a ring, wherein the diameter of the ring of the organic structure is the difference between the radius of the protection sleeve and the radius of the fiber core, that is, one end of the ring is in contact with the inner wall of the fiber core, and the other end of the ring is in contact with the protection sleeve, so that the ring can be fixed between the fiber core and the protection sleeve. In addition, one end of the elliptical ring of the organic structure is in contact with the inner wall of the circular ring, so that the elliptical ring is fixedly arranged.
The cross-sectional shape of the organic structure shown in fig. 1 is a preferred embodiment of the present invention, and other shapes are possible, and it is sufficient that the clad functions as a hollow fiber.
In one embodiment of the invention, the plurality of organic structural bodies are uniformly arranged in the cladding, so that the terahertz waves are well localized in the fiber core.
In one embodiment of the present invention, since the organic structures have relatively poor air permeability, gaps are formed between the plurality of organic structures embedded in the cladding, and the gaps in the cladding are communicated with the fiber core through the vent holes on the inner wall. So that the gas to be measured filled in the cladding can permeate into the core through the vent hole. For example, in fig. 1, a gap is left between two adjacent organic structures, and the gas to be measured filled into the gap can permeate into the core through the vent hole on the inner wall.
In one embodiment of the present invention, in order to facilitate the hollow optical fiber to function as a reaction chamber, one end of the hollow optical fiber includes a core inlet and a cladding inlet; the other end of the hollow core fiber includes a core exit. Therefore, the hollow optical fiber can receive terahertz waves through the fiber core inlet, receive gas to be detected through the cladding inlet, and then output the terahertz waves after reaction with the gas to be detected from the fiber core outlet at the other end of the hollow optical fiber.
Referring to fig. 2, in order to implement the detection of the gas component to be detected by using the hollow optical fiber, an embodiment of the present invention provides a gas detection system, including: a terahertz wave generating device 201, a terahertz wave detecting device 202, a coupling device 203, a spectral information processing device 204, and a hollow optical fiber 205 as described in any one of the above embodiments;
the terahertz wave generating device is used for generating terahertz waves, and the generated terahertz waves are incident into the coupling device;
the coupling device is connected with one end of the hollow optical fiber and is used for coupling incident terahertz waves and collected gas to be detected into a fiber core and a cladding of the hollow optical fiber respectively so as to enable the terahertz waves to react with the gas to be detected which permeates into the fiber core from the cladding in the transmission process of the terahertz waves in the fiber core and to be output from the other end of the fiber core;
the terahertz wave detection device is used for detecting terahertz waves output from the fiber core to obtain an absorption spectrum of the gas to be detected and sending the absorption spectrum of the gas to be detected to the spectrum information processing device;
and the spectral information processing device is used for obtaining an analysis result according to the absorption spectrum of the gas to be detected.
In the embodiment of the invention, the hollow optical fiber can be bent and folded, and the hollow optical fiber is used as a reaction cavity for the terahertz waves and the gas to be detected, so that the reaction cavity is smaller in volume and small in occupied space, the volume of the gas detection system can be reduced, and the portability of the gas detection system is improved.
In an embodiment of the present invention, in order to ensure that the coupling processes are not affected when the terahertz wave and the gas to be measured are coupled into the hollow optical fiber at the same time, the coupling device may include an incident port for receiving the terahertz wave and an air suction port for receiving the gas to be measured, the incident port is communicated with a fiber core inlet of the hollow optical fiber, and the air suction port is communicated with a cladding inlet of the hollow optical fiber. Therefore, the coupling device can receive the terahertz waves from the incident port and couple the terahertz waves into the fiber core through the fiber core inlet of the hollow optical fiber, and the coupling device receives the gas to be detected from the air suction port and couples the gas to be detected into the cladding through the cladding inlet of the hollow optical fiber, so that the terahertz waves and the gas to be detected can be independently coupled, and the mutual influence of the terahertz waves and the gas to be detected in the coupling process is reduced.
Next, each component in the gas detection system will be described by taking the gas detection shown in fig. 3 as an example.
First, the terahertz-wave generating device 201 may include a femtosecond laser 2011, a beam splitter 2012, a time delay line 2013, a polarization maintaining fiber 2014, and a photoconductive antenna 2015.
Laser pulses output by the femtosecond laser are divided into pumping pulses and detection pulses by the beam splitter. The terahertz wave is generated by the pump pulse which is incident on the photoconduction generation antenna through the polarization maintaining fiber; the detection pulse is delayed by a time delay line and then is incident on the terahertz detection device through a polarization maintaining optical fiber.
Wherein, compact, miniaturized femto second laser instrument is as the pumping source, and its parameter can be: the center wavelength is 1550nm, the pulse width is 80fs, the repetition frequency is 80MHz, and the maximum output power is 50 mW. The ultrashort laser pulse output by the femtosecond laser can be divided into 1: the 1 proportion is divided into two beams, one beam is a pumping pulse, and the other beam is a detection pulse. When a pumping pulse is incident on a photoconductive generation antenna through a polarization maintaining fiber, because the single photon energy of the pumping pulse is larger than the energy gap width of a semiconductor material on the photoconductive antenna, electron hole pairs are generated on the surface of the semiconductor material, under the action of an externally applied 70V bias voltage, the electron hole pairs move directionally to form a photo-generated current which changes instantly, and terahertz waves with the frequency range of 0.1-2.5THz are radiated outwards. The detection pulse is delayed by a time delay line and then is incident on the terahertz detection device 202 through a polarization maintaining fiber. Preferably, the photoconductive detection antenna 2021 may be selected as the terahertz detection device 202 because the photoconductive detection antenna has a small volume.
Fig. 4 is a schematic structural diagram of a time delay line according to an embodiment of the invention. The dotted line in the figure is the optical path of the detection pulse, wherein a1 is a pulse input port, a 2-a 4 are reflectors, a5 is a pulse output port, a6 is a roller-sliding guide rail, and the roller-sliding guide rail a6 can adjust the horizontal position of the reflector A3, so that the delay time of the detection pulse can be adjusted.
It should be noted that the time delay line needs to ensure that the phases of the detection pulse and the terahertz wave when they reach the photoconductive detection antenna are consistent.
Then, with respect to the coupling device 203, an incident port thereof corresponds to a direction in which the photoconductive antenna 2015 emits the terahertz waves, and the emitted terahertz waves can directly enter the coupling device through the incident port.
In order to be able to input the gas to be tested to the suction port of the coupling device 203, the gas detection system may further include a gas collection tank 206 for collecting the gas to be tested and a gas circulation pump 207 through which the gas to be tested in the gas collection tank is then input to the suction port of the coupling device.
The coupling device couples the terahertz waves into the fiber core through the fiber core inlet of the hollow optical fiber and into the cladding through the cladding inlet of the hollow optical fiber. The gas to be detected coupled into the cladding permeates into the fiber core through the vent holes in the inner wall of the fiber core, and fully reacts with the gas to be detected along with the increase of the transmission distance of the terahertz waves, so that the gas to be detected is output from the other end of the hollow optical fiber.
Next, for the terahertz detection device 202, the photoconductive detection antenna 2021 detects terahertz wave radiation based on the photoconductive sampling principle, and when a detection pulse is incident on the photoconductive detection antenna, because the single photon energy of the ultrashort laser pulse is greater than the energy gap width of the semiconductor material, an electron-hole pair is excited on the photoconductive surface, and the electron-hole pair randomly moves and is rapidly recombined and annihilated without the action of an external electric field. However, when the detection pulse and the terahertz wave radiation electric field exist simultaneously, the electron hole pairs can directionally move under the driving of the terahertz wave radiation electric field to form a photo-generated current, and the size of the photocurrent is in direct proportion to the size of the terahertz wave radiation electric field, so that the terahertz wave output from the other end of the hollow optical fiber can be detected and obtained, and the absorption spectrum of the gas to be detected is obtained.
Finally, for the spectral information processing device 204, the positions and intensities of the spectral absorption peaks of different gases in the terahertz wave frequency band can be obtained in advance as references, and then the positions of the absorption peaks of the absorption spectrum corresponding to the various spectra are analyzed according to the absorption spectrum of the gas to be detected obtained by the terahertz wave detection device, and then compared with the positions of the absorption peaks corresponding to the reference gas, so that the gas components contained in the gas to be detected can be obtained, and the concentrations of the gas components can be calculated according to the intensities of the absorption peaks.
In an embodiment of the present invention, in order to obtain the detection result in time, the gas detection system may further include an alarm unit 208 and a display 209, and if the concentration of the detected gas exceeds the standard, the alarm unit is used to alarm, and each gas component detected in the gas to be detected and the corresponding concentration are displayed on the display, so as to implement digital presentation of data.
Referring to fig. 5, an embodiment of the present invention further provides a gas detection method based on any one of the gas detection systems described above, including:
step 501: generating terahertz waves by utilizing a terahertz generating device, and enabling the generated terahertz waves to be incident into a coupling device;
step 502: the terahertz wave and the gas to be detected are respectively coupled into the fiber core and the cladding of the hollow optical fiber by using the coupling device, so that the terahertz wave reacts with the gas to be detected which permeates into the fiber core from the cladding in the transmission process of the terahertz wave in the fiber core and is output from the other end of the fiber core;
step 503: detecting terahertz waves output from the fiber core by using a terahertz wave detection device to obtain an absorption spectrum of the gas to be detected, and sending the absorption spectrum of the gas to be detected to the spectrum information processing device;
step 504: and obtaining an analysis result by utilizing the spectral information processing device according to the absorption spectrum of the gas to be detected.
In the embodiment of the invention, the method can realize the detection of various gas components and concentrations, and effectively improve the gas detection efficiency.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an …" does not exclude the presence of other similar elements in a process, method, article, or apparatus that comprises the element.
Those of ordinary skill in the art will understand that: all or part of the steps for realizing the method embodiments can be completed by hardware related to program instructions, the program can be stored in a computer readable storage medium, and the program executes the steps comprising the method embodiments when executed; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A hollow core optical fiber comprising a core, a cladding surrounding an inner wall of said core, and a protective jacket outside said cladding; the inner wall comprises a plurality of vent holes.
2. The hollow optical fiber according to claim 1, wherein the core is hollow and filled with dry air.
3. The hollow core optical fiber according to claim 2, wherein the cladding is made of a material having a refractive index of more than 1.
4. The hollow optical fiber according to claim 3, wherein a plurality of organic structures are embedded in the cladding, and the organic structures are made of thermoplastic organic polymers with low loss in the terahertz wave frequency band.
5. The hollow optical fiber according to claim 4,
the cross section of the organic structure body is at least one of a strip shape, an annular shape and a round shape; and/or the presence of a gas in the gas,
the material of the organic structure is at least one of polyethylene, cyclic olefin copolymer and polymer cyclic grease.
6. The hollow optical fiber according to claim 4, wherein gaps are provided between the plurality of organic structures embedded in the cladding, and the gaps in the cladding communicate with the core through the vent holes in the inner wall.
7. The hollow core fiber according to any of claims 1-6, wherein one end of the hollow core fiber comprises a core inlet and a cladding inlet; the other end of the hollow fiber comprises a fiber core outlet.
8. A gas detection system comprising a terahertz-wave generating device, a terahertz-wave detecting device, a coupling device, a spectral information processing device, and the hollow optical fiber according to any one of claims 1 to 7;
the terahertz wave generating device is used for generating terahertz waves, and the generated terahertz waves are incident into the coupling device;
the coupling device is connected with one end of the hollow optical fiber and is used for coupling incident terahertz waves and collected gas to be detected into a fiber core and a cladding of the hollow optical fiber respectively so as to enable the terahertz waves to react with the gas to be detected which permeates into the fiber core from the cladding in the transmission process of the terahertz waves in the fiber core and to be output from the other end of the fiber core;
the terahertz wave detection device is used for detecting terahertz waves output from the fiber core to obtain an absorption spectrum of the gas to be detected and sending the absorption spectrum of the gas to be detected to the spectrum information processing device;
and the spectral information processing device is used for obtaining an analysis result according to the absorption spectrum of the gas to be detected.
9. The gas detection system of claim 8, wherein the coupling device comprises an incident port for receiving terahertz waves and a suction port for receiving a gas to be measured, the incident port being in communication with a core inlet of the hollow optical fiber, the suction port being in communication with a cladding inlet of the hollow optical fiber.
10. A gas detection method based on the gas detection system according to claim 8 or 9, comprising:
generating terahertz waves by utilizing a terahertz generating device, and enabling the generated terahertz waves to be incident into a coupling device;
the terahertz wave and the gas to be detected are respectively coupled into the fiber core and the cladding of the hollow optical fiber by using the coupling device, so that the terahertz wave reacts with the gas to be detected which permeates into the fiber core from the cladding in the transmission process of the terahertz wave in the fiber core and is output from the other end of the fiber core;
detecting terahertz waves output from the fiber core by using a terahertz wave detection device to obtain an absorption spectrum of the gas to be detected, and sending the absorption spectrum of the gas to be detected to the spectrum information processing device;
and obtaining an analysis result by utilizing the spectral information processing device according to the absorption spectrum of the gas to be detected.
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