CN101718693B - Nitrogen dioxide gas concentration measuring instrument of optical fiber with mismatched fiber core - Google Patents
Nitrogen dioxide gas concentration measuring instrument of optical fiber with mismatched fiber core Download PDFInfo
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- CN101718693B CN101718693B CN2009102289602A CN200910228960A CN101718693B CN 101718693 B CN101718693 B CN 101718693B CN 2009102289602 A CN2009102289602 A CN 2009102289602A CN 200910228960 A CN200910228960 A CN 200910228960A CN 101718693 B CN101718693 B CN 101718693B
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Abstract
The invention relates to a nitrogen dioxide gas concentration measuring instrument of an optical fiber with a mismatched fiber core, comprising an optical source, an optical divider, an optical fiber sensing element, an optical spectrum analyzer, a photoelectric detector and an optical fiber for connection, wherein the optical fiber sensing element is in a multi-module-single-module- multi-module structure and consists of two multi-module optical fibers and a naked single-module optical fiber positioned between the two multi-module optical fibers through fusion welding, and a nano compound film with zinc oxide and phthalocyanine is deposited on the naked single-module optical fiber; and the optical fiber sensing element is positioned in measured nitrogen dioxide gas. The invention has the advantages of simple structure, low cost and high reliability. The sensing element has the advantages of favorable optical properties, stable chemical performance, flexible design as well as favorable stability and high response speed. Adopting the optical-fiber sensing element, the invention also has the advantages of high temperature resistance, corrosion resistance, high measuring precision, miniaturization, electromagnetic interference resistance, good electric insulation, safety and reliability, remote transmission, easy repeated use, and the like, and is especially suitable for harsh environment and environment with serious pollution.
Description
Technical field
The invention belongs to the air-sensitive field of sensing technologies, a kind of optical fiber nitrogen dioxide gas concentration measuring instrument of fiber core mismatch particularly, it can be monitored and measure the nitrogen dioxide harmful gas concentration signal in industrial gaseous waste, food and the environment such as living environment, air pollution timely and accurately.
Background technology
Enforcement to harmful poisonous gas in the environment such as present many industrial circles, air pollution, mine safety is measured with control extremely important.Gas sensor than other electric weight, fiber gas sensor with optical fiber have that volume is little, bandwidth, low, the anti-electromagnetic interference (EMI) of loss is strong and the characteristics that contain much information of carrying, by its sensor that constitutes have anti-electromagnetic interference (EMI), electrical isolation, corrosion-resistant, highly sensitive, be convenient to multiplexing, become plurality of advantages such as net and extremely attention.
In the existing measuring technique, all be according to gas with various the absorbing state of certain specific wavelength to be carried out quantitatively or analyzed qualitatively gas, this sensor-based system complexity, cost are higher; Some adopt polishing fiber exposed fibre core surface and obtain conical fiber by corrosion, have all destroyed the structure of optical fiber to a certain extent, have reduced its physical strength.Adopt the method for the direct welding of optical fiber of different core diameters, can produce very strong evanscent field at sensitive zones, and with low cost, make simple, be easy to realize.The good characteristic of this set of sensors nano compound film and the advantage of optical fiber can realize distributed measurement, be easy to integrated and remote sensing in one, therefore have other sensor incomparable advantage.The sensor of environment sensitive characteristic that the characteristic of combining nano compound structure film and optical fiber evanscent field are not arranged at present as yet is to the scheme of signal sensing such as nitrogen dioxide gas concentration and analysis.
Summary of the invention
The objective of the invention is at above-mentioned existing problems, provide a kind of simple in structure, the response time short, the optical fiber nitrogen dioxide gas concentration measuring instrument of fiber core mismatch highly sensitive and easy to make, with low cost, easy to implement.
Technical scheme of the present invention:
A kind of optical fiber nitrogen dioxide gas concentration measuring instrument of fiber core mismatch comprises that light source, two optical branching device a, b, fiber sensing element, spectroanalysis instrument, two photodetector a, b use optical fiber with being connected; Light source is connected with optical branching device a by optical fiber, optical branching device a one end links to each other with photodetector a by optical fiber as the reference arm, the other end is connected in series with fiber sensing element and optical branching device b respectively by optical fiber, optical branching device b one end links to each other with spectroanalysis instrument, and the other end links to each other with photodetector b; Fiber sensing element is arranged in tested nitrogen dioxide gas.
Described connection optical fiber is single-mode fiber or multimode optical fiber.
Described light source adopts scanned laser or wideband light source.
Described fiber sensing element is multi-mode-single mode-multi-mode structure, and it is made of by welding two sections multimode optical fibers, one section naked single-mode fiber middle with being positioned at two sections multimode optical fibers, deposits zinc paste and CuPc nano compound film on naked single-mode fiber.
The length of described naked single-mode fiber is 8mm-3cm.
In described zinc paste and the CuPc nano compound film, the thickness of zinc-oxide film is that the thickness of 5nm-10nm, phthalocyanine copper film is 30nm-100nm.
The preparation method of described fiber sensing element is: naked single-mode fiber and multimode optical fiber are cut and guarantee that fiber end face is smooth, then with optical fiber splicer with naked single-mode fiber two ends and multimode optical fiber welding; With rf magnetron sputtering growing film method first depositing zinc oxide nano thin-film on naked single-mode fiber, background pressure is set in the thin film deposition is (1-2) * 10
-3Pa, operating pressure are that (0.8-1.2) Pa, argon flow amount are that (18-25) sccm (ml/min), radio-frequency sputtering power are 150W ~ 190W; Is annealing in process 2 hours-4 hours under the 80-100 ℃ of condition with zinc-oxide film in temperature; With vacuum thermal evaporation coating method deposition CuPc nano thin-film on the single-mode fiber of depositing zinc oxide film, operating room's vacuum tightness is (1～3) * 10-3Pa, and evaporation current is (30-60) A, and the evaporation rate of CuPc film is (1-3) nm/s; With atomic force microscope film surface appearance is tested at last.
Test philosophy:
Multimode optical fiber, single-mode fiber and the multimode optical fiber structure according to multi-mode-single mode-multimode is welding together, because core diameter difference and cladding diameter is identical, therefore make fibre core core diameter mismatch, the core mode that originally in multimode optical fiber, transmits, when through single-mode fiber, part core mode will be coupled again with the cladding mode in the single-mode fiber, forms very strong evanscent field.
The evanscent field variations in refractive index of environment to external world has good susceptibility, after we partly deposit the sensitive thin film zinc paste-CuPc of composite nanostructure at single-mode fiber, be placed in the certain density nitrogen dioxide gas, because the effect of sensitive thin film and gas, to make the optical property of sensitive thin film change, thereby cause change of refractive.The environment refractive index that is the evanscent field place changes, and causes that evanscent field changes.
Change for the evanscent field intensity transmission, promptly cover being changed to of transmission power of the optical fiber of nano thin-film:
P
t＝P
0exp(-2rΔαL) (1)
Wherein, P
0Transmission power when not contacting gas.R=P
Evanscent field/ P
Whole light intensity, L is the length of sensing element single-mode fiber or the length that is deposited the optical fiber of film.Δ α=α '-α, α ' be with the gas effect after the absorption coefficient of film, α is not for making the absorption coefficient of the laminated film of time spent with gas.When sensor does not contact gas, Δ α=0, P
t=P
0Δ α is mainly relevant with the refractive index of thickness, refractive index and the external agency of sensitive thin film.
Membraneous material to the nitrogen dioxide gas sensitivity mainly is a CuPc, studies show that, the film with composite structure can better improve reaction time and concentration range, and can carry out flexible according to the requirement of sensor characteristic.Therefore can choose zinc paste and come compoundly together, the cost of material is low for these, easily obtain, easily growth.Adopt the laminated film of nanostructured, can effectively improve the response time.Adopt radio-frequency magnetron sputter method on the single-mode fiber that sensing is used, to deposit CuPc macromolecular material and zinc paste, the film that this method generates is a kind of nano composite structure that has, and can relatively regulating composition, thereby the sensitivity characteristic of optimization sensor according to the requirement of sensitivity characteristic.Optimized its thickness through a large amount of experimental studies and also well be improved its gas concentration susceptibility with the structure and morphology of its laminated film of transmission electron microscopy observation.Then, laminated film is heat-treated to improve its temperature stability, make this sensor not only can be used under general environment or the common hot environment, and can not be subjected to the influence that ambient temperature changes.Be expected to obtain the not nitrogen dioxide gas concentration measuring instrument of temperature influence like this.
The invention has the beneficial effects as follows: sensing element adopts zinc paste and CuPc nano compound film, and its optical property is good, stable chemical performance, flexible design, good stability and response speed are fast; Adopt the optical-fiber type sensing element also have high temperature resistant, corrosion-resistant, but measuring accuracy is high, miniaturization, anti-electromagnetic interference (EMI), good, the safe and reliable long-distance transmissions of electrical insulation capability, easy advantage such as multiplexing, be particularly suitable under abominable and environmental pollution comparison serious environmental, working.The present invention is simple in structure, preparation cost is low, reliability is high, and fiber gas sensor is developed towards practicability, microminiaturized direction, has the potentiality of the detector that becomes distributed and distance measuring.
Description of drawings
Fig. 1 is a structural representation of the present invention.
Fig. 2 is the structural representation of fiber sensing element among the present invention.
Among the figure: 1. light source 2-I, 2-II. optical branching device a, b 3. fiber sensing element 4-I, 4-II. photodetector a, b 5. spectroanalysis instruments 6. connect with optical fiber 7. tested nitrogen dioxide gas 8. zinc paste and CuPc nano compound film 9. naked single-mode fiber 10. multimode optical fibers
Embodiment
The present invention is further described below in conjunction with drawings and Examples.
Embodiment:
A kind of optical fiber nitrogen dioxide gas concentration measuring instrument of fiber core mismatch comprises light source 1, two optical branching device a, b 2-I, 2-II. fiber sensing element 3, spectroanalysis instrument 5, two photodetector a, b4-I, 4-II and is connected with optical fiber 6; Light source 1 is connected with optical branching device a2-I by optical fiber 6, optical branching device a2-I one end links to each other with photodetector a4-I by optical fiber 6 as the reference arm, the other end is connected in series with fiber sensing element 3 and optical branching device b2-II respectively by optical fiber 6, optical branching device b4-II one end links to each other with spectroanalysis instrument 5, and the other end links to each other with photodetector b4-II; Fiber sensing element 3 is arranged in tested nitrogen dioxide gas 7.Among this embodiment, the service band of light source 1 is 1530-1570nm; Optical branching device 2-I, 2-II are photo-coupler; Connect the single-mode fiber that adopts the 1550nm wave band with optical fiber 6; Fiber sensing element is multi-mode-single mode-multi-mode structure, deposits zinc paste and CuPc nano compound film on naked single-mode fiber, and the length of naked single-mode fiber is 8mm, and the thickness of zinc-oxide film is that the thickness of 5nm-10nm, CuPc is 30nm-100nm; The preparation method of fiber sensing element is: naked single-mode fiber and multimode optical fiber are cut and guarantee that fiber end face is smooth, then with optical fiber splicer with naked single-mode fiber two ends and multimode optical fiber welding; With rf magnetron sputtering growing film method first depositing zinc oxide nano thin-film on naked single-mode fiber, background pressure is set in the thin film deposition is (1-2) * 10
-3Pa, operating pressure are that (0.8-1.2) Pa, argon flow amount are that (18-25) sccm (ml/min), radio-frequency sputtering power are 150W ~ 190W; Is annealing in process 3 hours under 100 ℃ of conditions with zinc-oxide film in temperature; With vacuum thermal evaporation coating method deposition CuPc nano thin-film on the single-mode fiber of depositing zinc oxide film, vacuum tightness is (1～3) * 10-3Pa, the evaporation boat evaporates boat with the molybdenum sheet of homemade wide (1-1.5) cm, evaporation current is (30-60) A, and the evaporation rate of CuPc film is about (1-3) nm/s; With atomic force microscope film surface appearance is tested at last.
During actual the use, monitor the variation of tested nitrogen dioxide gas concentration transmission spectrum of fiber optic sensing device when changing, calculate its transmitted light intensity, can realize detection thus gas concentration with photodetector with spectrometer.
Claims (6)
1. the optical fiber nitrogen dioxide gas concentration measuring instrument of a fiber core mismatch is characterized in that: comprise that light source, two optical branching device a, b, fiber sensing element, spectroanalysis instrument, two photodetector a, b use optical fiber with being connected; Light source is connected with optical branching device a by optical fiber, optical branching device a one end links to each other with photodetector a by optical fiber as the reference arm, the other end is connected in series with fiber sensing element and optical branching device b respectively by optical fiber, optical branching device b one end links to each other with spectroanalysis instrument, and the other end links to each other with photodetector b; Fiber sensing element is arranged in tested nitrogen dioxide gas, described fiber sensing element is multi-mode-single mode-multi-mode structure, it is made of by welding two sections multimode optical fibers, one section naked single-mode fiber middle with being positioned at two sections multimode optical fibers, deposits zinc paste and CuPc nano compound film on naked single-mode fiber.
2. according to the optical fiber nitrogen dioxide gas concentration measuring instrument of the described fiber core mismatch of claim 1, it is characterized in that: described connection optical fiber is single-mode fiber or multimode optical fiber.
3. according to the optical fiber nitrogen dioxide gas concentration measuring instrument of the described fiber core mismatch of claim 1, it is characterized in that: described light source adopts scanned laser or wideband light source.
4. according to the optical fiber nitrogen dioxide gas concentration measuring instrument of the described fiber core mismatch of claim 1, it is characterized in that: the length of described naked single-mode fiber is 8mm-3cm.
5. according to the optical fiber nitrogen dioxide gas concentration measuring instrument of the described fiber core mismatch of claim 1, it is characterized in that: in described zinc paste and the CuPc nano compound film, the thickness of zinc-oxide film is that the thickness of 5nm-10nm, phthalocyanine copper film is 30nm-100nm.
6. according to the optical fiber nitrogen dioxide gas concentration measuring instrument of the described fiber core mismatch of claim 1, it is characterized in that: the preparation method of described fiber sensing element is: naked single-mode fiber and multimode optical fiber are cut and guarantee that fiber end face is smooth, then with optical fiber splicer with naked single-mode fiber two ends and multimode optical fiber welding; With rf magnetron sputtering growing film method first depositing zinc oxide nano thin-film on naked single-mode fiber, background pressure is set in the thin film deposition is (1-2) * 10
-3Pa, operating pressure are that (0.8-1.2) Pa, argon flow amount are that (18-25) sccm, radio-frequency sputtering power are 150W～190W; Is annealing in process 2 hours-4 hours under the 80-100 ℃ of condition with zinc-oxide film in temperature; With vacuum thermal evaporation coating method deposition CuPc nano thin-film on the single-mode fiber of depositing zinc oxide film, operating room's vacuum tightness is (1-3) * 10
-3Pa, evaporation current is (30-60) A, the evaporation rate of CuPc film is (1-3) nm/s; With atomic force microscope film surface appearance is tested at last.
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| CN102052130A (en) * | 2011-01-11 | 2011-05-11 | 无锡市凯龙汽车设备制造有限公司 | Tail gas processing system of diesel engine based on nitrogen oxide sensor |
| CN103163110A (en) * | 2013-02-25 | 2013-06-19 | 东南大学 | Optical fiber gas array sensor and preparation method thereof |
| CN109709074B (en) * | 2019-01-21 | 2021-06-01 | 哈尔滨理工大学 | Optical fiber ammonia gas sensor based on Ag-doped ZnO nanoflower and manufacturing method thereof |
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| US5747348A (en) * | 1995-07-05 | 1998-05-05 | The Aerospace Corporation | Diode laser interrogated fiber optic hydrazine-fuel sensor |
| CN1766569A (en) * | 2005-11-02 | 2006-05-03 | 哈尔滨工业大学 | Nitrogen dioxide gas concentration monitoring system and monitoring method thereof |
| CN101105446A (en) * | 2007-01-19 | 2008-01-16 | 华南理工大学 | Differential optical absorption spectroscopy air quality detection system |
| CN101299020A (en) * | 2008-06-16 | 2008-11-05 | 浙江大学 | Optical gas sensor based on single polymer nano-wire |
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Patent Citations (4)
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|---|---|---|---|---|
| US5747348A (en) * | 1995-07-05 | 1998-05-05 | The Aerospace Corporation | Diode laser interrogated fiber optic hydrazine-fuel sensor |
| CN1766569A (en) * | 2005-11-02 | 2006-05-03 | 哈尔滨工业大学 | Nitrogen dioxide gas concentration monitoring system and monitoring method thereof |
| CN101105446A (en) * | 2007-01-19 | 2008-01-16 | 华南理工大学 | Differential optical absorption spectroscopy air quality detection system |
| CN101299020A (en) * | 2008-06-16 | 2008-11-05 | 浙江大学 | Optical gas sensor based on single polymer nano-wire |
Non-Patent Citations (1)
| Title |
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| 金兴良等.溶胶-凝胶薄膜光纤传感器法测定空气中二氧化氮.《分析化学》.2005,第33卷(第9期),1215-1218. * |
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