CN100595572C - Manufacture method for double-humped resonance coating optical fiber grating gas-sensing sensor - Google Patents
Manufacture method for double-humped resonance coating optical fiber grating gas-sensing sensor Download PDFInfo
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- CN100595572C CN100595572C CN200710037525A CN200710037525A CN100595572C CN 100595572 C CN100595572 C CN 100595572C CN 200710037525 A CN200710037525 A CN 200710037525A CN 200710037525 A CN200710037525 A CN 200710037525A CN 100595572 C CN100595572 C CN 100595572C
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Abstract
This invention relates to one double peak vibration coating fiber and grating sensor method in sensor process technique field, which comprises the following steps: a, selecting fiber grating; b, determining coat film thickness; c, determining double peak center wave length; d, fiber grating cover coating; e, sensor probe processing; f, double peak signal testing. This invention provides one smallshaped, highly integrated and accurate film fiber and grating gas sensitive sensor process method.
Description
Technical field
The present invention relates to the manufacturing technology of gas sensor, particularly relate to a kind of manufacturing technology of double-humped resonance coating optical fiber grating gas-sensing sensor.
Background technology
(long-period fiber grating is that photic fiber core refractive index changes optical fibre device LPFG) to long period fiber grating.Compare with the Bragg fiber grating, LPFG is especially responsive to the variations in refractive index of covering surrounding medium, and resolution can reach 10
-5, therefore can be used as the environment index sensor.Be mainly used in solution concentration at present and measure, monitoring is used widely with detection in petroleum industry especially, and its detection resolution can be comparable with liquid chromatography(LC) instrument and ultraviolet spectrometer (UVS).
When the grating cycle is lacked (100 μ m), for the higher cladding mode of some number of times, in the grating ablation process, can observe two harmonic peaks, be called the double-humped resonance effect.There is opposite wave length shift characteristic at the double resonance peak when extraneous variations in refractive index, utilize this characteristic to make a kind of highly sensitive strength of fluid sensor, adopts LP
015The scheme that the spacing at mould double resonance peak is carried out the concentration sensing can improve 20 times than the grating sensing scheme sensitivity of adopting 400 μ m.
The LPFG of above-mentioned use is directly to be immersed in the external agencys such as liquid.Higher sensitivity is just arranged when having only the external environment condition refractive index to be less than or equal to the refractive index of fibre cladding, and this has just limited its application aspect chemical detection to a great extent.
Adopt Langmuir-Blodgeet technology (being called for short the LB technology), arrive a few hundred nano-scale LB films at LPFG surface-coated one layer thickness tens, the refractive index response characteristic of experimental result LPFG obtains very big improvement, eliminated chemical solution refractive index to be detected and must enlarge its sensing scope less than the restriction of cladding index.But, because organic (dyestuff) molecule has limited its detection to numerous gases to the specificity of gas molecule sensitivity; And, organic film molecule non-refractory, the therefore also application of incompatibility high temperature occasion.
Sol-gel technique is a kind of comparatively rapidly material preparation technology that can obtain to have various superior functions, be suitable for various specific (special) requirements of development in recent years, especially in the film preparation field, control, film have distinct advantages such as porous structure and specific surface area are big easily owing to mix, and make it cause that in air-sensitive sensing material preparation field people pay attention to greatly.
Metal oxide semiconductor has the good quick characteristic of phosgene (refractive index that is film changes with extraneous atmosphere), as SnO
2Behind the contact reducibility gas, light transmission changes with ambient gas character and concentration, and the selectivity by doping metals atom, rare earth oxide enhancing sense film can realize the detection to specific gas and concentration, can adapt to various application scenario.
Adopt sol-gel technique, with the metal oxide semiconductor thin film coated in the fiber grating cladding surface, not only can obtain the sensitivity of good optical air-sensitive, simultaneously, the modification of material, doping, the compound performance that can further improve air-sensitive film, thereby select this material to make sensitive thin film, have important universal significance.
If double-hump effect is applied on the plated film LPFG, then not only can utilize the LPFG refractive index highly sensitive but also can make full use of the susceptibility of film, enlarge the range of application of LPFG double-hump effect, measure, also can be used for gas concentration measurement except can be used for strength of fluid.The research of this respect does not at present appear in the newspapers as yet.
Summary of the invention
At the defective that exists in the above-mentioned prior art, but technical matters to be solved by this invention provides the manufacture method of a kind of miniaturization, high integrated remote measurement, high-sensitive double-humped resonance coating optical fiber grating gas-sensing sensor; Use this method manufactured sensor, detected gas is had very high sensitivity, can be to the Measurement Resolution of thin-film refractive index up to 10
-7, it has concentrated the advantage of thin film sensor and optical fiber grating structure, can extensively use in Optochemical sensor.
In order to solve the problems of the technologies described above, the manufacture method of a kind of double-humped resonance coating optical fiber grating gas-sensing sensor provided by the present invention is characterized in that, comprises the steps:
1) selects fiber grating;
2) determine coating film thickness;
3) determine bimodal centre wavelength;
4) the fiber grating covering is filmed;
5) sensor head construction;
6) bimodal input.
In the manufacture method of described gas sensor, step 1) selects the concrete grammar of fiber grating to be: selection cycle 100 μ m-200 μ m, the amount of selling off are 10
-4-10
-3, length is the fiber grating of 1cm-2cm, this fiber grating have make easily, characteristics that physical strength is high.
In the manufacture method of described gas sensor, step 2) determine that the concrete grammar of coating film thickness is: a) calculate the double-humped resonance wavelength of given fiber grating, obtain the refractive index sensitivity S
n(being defined as the rate of change of double resonance peak center wavelength spacing and the ratio of film refractive index rate of change); B) describe sensitivity S
n(and the diagram of block between film refractive index and the thickness; C) sensitivity S of making according to diagram of block
nLevel line, determine sensitivity S
nBe higher than 10
2The refractive index of the air-sensitive film of filming that requires and the thickness range of film are chosen thickness according to the refractive index of institute's coated film.
In the manufacture method of described gas sensor, step 3) determines that the concrete grammar of bimodal centre wavelength is: a) utilize phase-matching condition to calculate and describe the cycle of the plated film long period fiber grating under the higher mode and the relation curve of each time cladding mode resonance wavelength; B) according to step 2) the selected parameter of filming, and the grating cycle of selecting, further provide the double-humped resonance wavelength by relation curve.
In the manufacture method of described gas sensor, the concrete grammar that step 4) fiber grating covering is filmed is: a) fiber grating of strip of paper used for sealing is removed in ultrasonic cleaning, and cleaning fluid is followed successively by hydrochloric acid, NaOH and absolute ethyl alcohol; After cleaning end, use deionized water rinsing, place baking oven to dry; B) preparing metal alkoxide solution places the flask of sealing, carries out the electric power stirring and reflux ageing under constant room temperature at last, the coated solution of acquisition homogeneous transparent under constant temperature; C) adopt czochralski method to prepare colloidal sol-gel film, the fiber grating that has cleaned is immersed coating liquid, at the uniform velocity the vertical-lift fiber grating makes the fiber grating covering adsorb one deck colloidal sol outward, forms one deck liquid film, obtains gel mould through evaporation; D) fiber grating of filming is placed a quartz ampoule that seals, put into tube type high-temperature furnace again and heat, heat up, room temperature is slowly reduced in insulation again, obtains to have porous structure, uniform sol gel air-sensitive film.
In the manufacture method of described gas sensor, the concrete grammar of step 5) sensor head construction is: adopt small tapered index lens, promptly GRIN Lens keeps two GRIN Lens separated by a distance, is fixed on behind the collimation on the aluminum strip, constitutes sensing head.
In the manufacture method of described gas sensor, the concrete grammar of the bimodal input of step 6) is: a) select two narrow band pass filters respectively according to the double-humped resonance wavelength; B) the detected signal in bimodal skew back is carried out differential ratio with initialize signal respectively; C) output signal to totalizer, trigger warning circuit through comparer after relatively with reference signal again.
Utilize the manufacture method of double-humped resonance coating optical fiber grating gas-sensing sensor provided by the invention, by outside fibre cladding, applying one deck film of atmosphere sensitivity (as colloidal sol-gel film) to external world, utilize the good gas sensing property of this film, and high-sensitive double-humped resonance effect, be used for detection, thereby enlarged the Application in Sensing scope specific gas.When this sensor contacts with ambient atmos, certain variation will take place in film refractive index, thereby cause the variation of long period fiber grating transmission spectrum, and the spacing at double resonance peak is skew thereupon also.
The beneficial effect that the present invention is compared with prior art had is: colloidal sol-gel film is owing to its porosity height, and corresponding specific surface area is also very big, and susceptibility and responsiveness height to gas are particularly suitable for doing gas sensitive.When the LPG sensor that will be coated with the metal oxide semiconductor film is exposed in the extraneous gas, the semiconductor surface energy state will change, and cause the minor alteration of thin-film refractive index.When the double-humped resonance effect took place, the centre wavelength of two attenuation peaks was along two opposite direction skews, and bimodal spacing changes greatly, therefore has very high refractive index sensitivity, is very suitable for high-sensitive air-sensitive and detects.
The photochemistry thin film sensor is compared with traditional electricity type block sensor, has the advantage that anti-electromagnetic interference (EMI), dynamic range are big, highly sensitive, response is fast; Do not electrically contact owing to have, it is particularly suitable for detecting inflammable, explosive gas.Particularly at petrochemical system, mine, occasions such as large power plant: need to detect oxygen, hydrocarbon, gases such as carbon monoxide adopt electrical sensor not only not reach permissible accuracy, more seriously can cause security incident.And the chemical optical fibre thin film sensor that combines with optical fiber technology, it is good to have electrical insulation capability, transport information capacity is big, energy loss is low, good in anti-interference performance, and environmental suitability is strong, high temperature resistant, anticorrosion, in light weight, softness is good, can be along path transmitting optical signal, the low cost and other advantages of bending.
Therefore this sensor that both are combined has excellent performance, can realize remote remote measurement, online in real time monitoring, and can make the high miniaturized device of the ratio of performance to price.This set of sensors has suffered the advantage of thin film sensor and Fibre Optical Sensor, is expected to become the high sensitivity Optochemical sensor of a new generation.
Description of drawings
Fig. 1 is film refractive index, the thickness scope synoptic diagram of the sensitivity level line correspondence of drawing in the embodiment of the invention;
Fig. 2 is the synoptic diagram that concerns in double-humped resonance wavelength under the different thickness of drawing in the embodiment of the invention and grating cycle;
Fig. 3 is embodiment of the invention fiber grating CH
4Gas sensor detection system block diagram.
Embodiment
Below in conjunction with description of drawings embodiments of the invention are described in further detail, but present embodiment is not limited to the present invention, every employing similarity method of the present invention and similar variation thereof all should be listed protection scope of the present invention in.
For the variation with the bimodal spacing of transmission spectrum shows to greatest extent, must select suitable sense film optical parametric and grating parameter, to improve the sensitivity of sensor.Therefore, need a kind of novel long-period fiber grating thin film sensor manufacture method.The optical thin film sensor is compared with traditional electricity type block sensor, and it has the advantages that anti-electromagnetic interference (EMI), dynamic range are big, highly sensitive, response is fast; Do not electrically contact owing to have, it is particularly suitable for detecting inflammable, explosive gas.Utilize the many-sided adaptability of fiber grating geometric configuration, can make the sensor and the sensor array of arbitrary shape, make the Multifunction Sensor of sensing different physical quantities.Further match, can realize telemeasurement and control with the fiber optic remote technology.Because it has concentrated the advantage of thin film sensor and fiber-optic grating sensor, is expected to be widely used in Optochemical sensor.
The manufacture method of a kind of double-humped resonance coating optical fiber grating gas-sensing sensor that the embodiment of the invention provided, its step is as follows:
1) select fiber grating, its concrete grammar is: selection cycle 100 μ m-200 μ m, the amount of selling off are 10
-4-10
-3, length is the fiber grating of 1cm-2cm, this fiber grating have make easily, characteristics that physical strength is high;
2) determine coating film thickness, its concrete grammar is:
A) given optical fiber grating structure parameter (cycle, length and the amount of selling off) and film refractive index and thickness, choose the continually varying wavelength value, the phase-matching condition of substitution long period fiber grating cladding mode coupling then can satisfy the wavelength of this condition, is called resonance wavelength.When the cladding mode number of times is higher, two wavelength may occur and satisfy phase-matching condition simultaneously, then these two wavelength value are double-humped resonance centre wavelength.
After trying to achieve double-humped resonance centre wavelength by aforementioned calculation, further obtain refractive index sensitivity (rate of change of double-humped resonance centre wavelength spacing and the ratio of film refractive index rate of change), depict sensitivity S
nAnd the diagram of block between Film Optics parameter refractive index and the thickness;
B) make sensitivity S according to diagram of block
nLevel line determines to meet highly sensitive (S
nBe higher than 10
2) film refractive index and the coating thickness scope that require, choose thickness according to the refractive index of institute's coated film.
3) determine bimodal centre wavelength, its concrete grammar is: a) utilize phase-matching condition to calculate and describe the cycle of the plated film long period fiber grating under the higher mode and the relation curve of each time cladding mode resonance wavelength; B) by 2) in the thin film parameter determined, in the grating cycle according to selecting, further provide the double-humped resonance wavelength by relation curve.
4) the fiber grating covering is filmed, and its concrete grammar is:
A) fiber grating of strip of paper used for sealing is removed in ultrasonic cleaning, and cleaning fluid is followed successively by hydrochloric acid, NaOH and absolute ethyl alcohol; After cleaning end, use deionized water rinsing, place baking oven to dry;
B) by certain molar concentration rate, the preparing metal alkoxide solution places the flask of sealing, carries out electric power and stir and reflux under constant temperature, and ageing reasonable time under constant room temperature at last obtains the coated solution of homogeneous transparent;
C) adopt czochralski method to prepare colloidal sol-gel film.To immerse coating liquid through the good fiber grating of cleaning, drying, with certain speed vertical-lift fiber grating equably; The fiber grating covering that relative motion is adsorbing one deck colloidal sol outward, forms one deck liquid film, and liquid film obtains gel mould through solvent and evaporation of water;
D) fiber grating of filming is placed the quartz ampoule of a sealing, puts into tube type high-temperature furnace again and heat, control certain temperature rise rate, reach certain temperature after, be incubated appropriate time, again with certain rate of temperature fall, slowly reduce to room temperature; After heat treatment, promptly obtain to have porous structure, uniform sol gel air-sensitive film; By the viscosity and the rate of pulling of control colloidal sol, can obtain the film of different-thickness.If need obtain thick film, then adopt the mode that repeatedly lifts.Between adjacent film for twice, need the oven dry of last time filming is handled;
5) sensor head construction, its concrete grammar is: adopt small tapered index lens, promptly GRIN Lens keeps two GRIN Lens separated by a distance, is fixed on behind the collimation on the aluminum strip, constitutes sensing head.This structure has not only overcome problems such as temperature stability, anti-seismic performance be not good, because GRIN Lens matches with optical fiber, and Transmission Fibers and the directly welding of lens tail optical fiber have improved the stability that is coupled greatly simultaneously;
6) bimodal input, its concrete grammar is: a) select two narrow band pass filters respectively according to the double-humped resonance wavelength; B) after sensing head and the gas effect to be measured, will cause that bimodal centre wavelength is offset in opposite direction, this moment, detected signal behind optical filter (skew) carried out differential ratio with initialize signal respectively; C) output signal to totalizer, trigger warning circuit through comparer after relatively with reference signal again.
One of specific embodiments of the invention are:
1. the making of sensor
Rate σ=2 * 10 are sold off in selection
-4, periods lambda=206 μ m, the fiber grating of length L=1.0cm;
Draw the three-dimensional plot of sensitivity and film refractive index, thickness, making sensitivity is 10
2Level line as follows, thereby in can be from Fig. 1 (film refractive index of sensitivity level line correspondence, thickness scope) the given zone, the film refractive index of selection and thickness one section belt-like zone in 1.71-1.74 and 190-220nm.
The ethanolic solution of preparation stannous chloride.Electric power stirs and refluxed 2 hours under 80 ℃ of constant temperature, and ageing 24 hours under 30 ℃ of constant temperature again obtains the coated solution of homogeneous transparent.
Lift thin films, the rate of pulling is 6cm/min.Lift once more after the oven dry, after 2 times, become gel mould repeatedly through drying.Insert in the high temperature furnace, be incubated 30 minutes down, reduce to room temperature again, obtain heat treated film sample at 500 ℃.Through compare test, film refractive index, thickness (1.73,200nm) near.Further can determine about 1380nm of double-humped resonance wavelength and 2020nm, with this centre wavelength as two narrow band pass filters in the detection system according to Fig. 2.
Utilize assembling sensing heads such as above-mentioned film coating optical fibre grating and GRIN Lens.
2. sensor implementation
With the fiber grating methane gas sensor is example, illustrates that novel sensor detects methane gas in mine.
The detection system structure is chosen the LED wideband light source as shown in Figure 3 as test light source.In order to carry out synchronous detection, LED by dutycycle be 50%, repetition frequency is the current impulse modulation of 110Hz, the input of modulating pulse simultaneously lock-in amplifier, lock-in amplifier amplifies the signal that comes from photodetector.Adopt InGaAs and PbS infrared eye respectively the double resonance peak to be surveyed in the photodetector.Make device constant temperature with attemperating unit, to eliminate the influence that light source and environmental temperature fluctuation are brought.
Sensing head is placed the air chamber of making by copper pipe.Air chamber has air intake opening, gas outlet and gauge outfit interface.Air intake opening is by the gas flow of noticeable degree notes people air chamber, and the gas outlet is connected to vacuum pump, and air chamber is vacuumized.Air chamber keeps constant temperature by attemperating unit.
When containing CH
4Gas when the air chamber, originally the centre wavelength of two of transmission spectrum attenuation peaks will be drifted about, simultaneously marked change also takes place near the transmitance the former centre wavelength, obviously weakens through the light signal of optical filter, and the amplitude that weakens and bimodal side-play amount are similar to linear.The size of side-play amount is with CH
4Gas concentration increase and increase.The signal of two-way output is being sent into totalizer through differential ratio after, and output signal is delivered to warning circuit.In case CH
4Gas concentration exceeds the limiting concentration of permission, then triggers and reports to the police.
Claims (1)
1, a kind of manufacture method of double-humped resonance film coating optical fibre grating gas sensor is characterized in that, comprises the steps:
1) select fiber grating:
Select the concrete grammar of fiber grating to be: selection cycle 100 μ m-200 μ m, the amount of selling off are 10
-4-10
-3, length is the fiber grating of 1cm-2cm;
2) determine coating thickness and definite double-humped resonance wavelength:
The concrete grammar of determining coating thickness is: a) calculate the double-humped resonance wavelength of given fiber grating, obtain the refractive index sensitivity S of the ratio of the rate of change that is defined as double-humped resonance wavelength spacing and film refractive index rate of change
nB) describe sensitivity S
nAnd the diagram of block between Film Optics parameter refractive index and the thickness; C) make sensitivity S according to diagram of block
nLevel line, determine highly sensitive in 10
2Desired refractive index and the coating thickness scope of filming further chosen thickness by the refractive index of institute's coated film;
The concrete grammar that calculates the double-humped resonance wavelength is: a) utilize phase-matching condition, by calculating, depict the cycle of the film coating optical fibre grating under the higher mode and the relation curve of cladding mode resonance wavelength; B), provide the difference double-humped resonance wavelength under the parameter of filming by relation curve according to the grating cycle of selecting;
According to the grating cycle of above-mentioned selection and the refractive index and the thickness of institute's coated film, determine the double-humped resonance wavelength by the above-mentioned relation curve;
3) the fiber grating covering is filmed:
The concrete grammar that the fiber grating covering is filmed is: a) fiber grating of strip of paper used for sealing is removed in ultrasonic cleaning, and cleaning fluid is followed successively by hydrochloric acid, sodium hydroxide solution and absolute ethyl alcohol; After cleaning end, use deionized water rinsing, place baking oven to dry; B) preparing metal alkoxide solution places the flask of sealing, carries out the electric power stirring and reflux ageing under constant room temperature at last, the coating solution of acquisition homogeneous transparent under constant temperature; C) adopt czochralski method to prepare colloidal sol-gel film, the fiber grating that has cleaned is immersed coating liquid, at the uniform velocity the vertical-lift fiber grating makes the fiber grating covering adsorb one deck colloidal sol outward, forms one deck liquid film, obtains gel mould through evaporation; D) fiber grating of filming is placed a quartz ampoule that seals, put into tube type high-temperature furnace again and heat, heat up, room temperature is slowly reduced in insulation again, obtains to have porous structure, uniform sol gel air-sensitive film;
4) sensor head construction:
The concrete grammar of sensor head construction is: adopt small tapered index lens, promptly GRIN Lens keeps two GRIN Lens separated by a distance, is fixed on behind the collimation on the aluminum strip, constitutes sensing head;
5) bimodal input:
The concrete grammar of bimodal input is: after a) selecting two narrow band pass filters to place sensing head respectively according to the double-humped resonance wavelength; B) sensing head carries out differential ratio with initialize signal with after gas contacts respectively with the detected signal in bimodal skew back; C) signal of differential ratio after exports totalizer to, again with reference signal through comparer back triggering warning circuit relatively.
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| CN102183487B (en) * | 2011-02-11 | 2013-01-23 | 上海理工大学 | Manufacturing method of metal film plated double-humped resonance liquid sensor based on SPR (Surface Plasmon Resonance) |
| CN108333076A (en) * | 2017-12-25 | 2018-07-27 | 兰州空间技术物理研究所 | A kind of room atmosphere surface density detection sensor and preparation method thereof |
| CN116571099A (en) * | 2023-06-09 | 2023-08-11 | 中国科学院赣江创新研究院 | Carbon molecular sieve membrane and preparation method and application thereof |
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| 镀膜长周期光纤光栅的双峰谐振效应与应用. 顾铮先，徐艳平.中国光学学会2006年学术大会论文摘要集. 2006 |
| 镀膜长周期光纤光栅的双峰谐振效应与应用. 顾铮先，徐艳平.中国光学学会2006年学术大会论文摘要集. 2006 * |
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