CN1793850A - Gas concentration detection method and equipment based on ring-shaped optical fiber laser - Google Patents
Gas concentration detection method and equipment based on ring-shaped optical fiber laser Download PDFInfo
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- CN1793850A CN1793850A CN 200510097004 CN200510097004A CN1793850A CN 1793850 A CN1793850 A CN 1793850A CN 200510097004 CN200510097004 CN 200510097004 CN 200510097004 A CN200510097004 A CN 200510097004A CN 1793850 A CN1793850 A CN 1793850A
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Abstract
A method for detecting concentration of gas based on circular optical fiber laser includes applying conical optical fiber, raising measurement accuracy by utilizing laser resonance to increase effective action length based on evanescent wave absorption in optical fiber laser cavity and realizing concentration measurement of different gas by applying tunable filter.
Description
Technical field
The invention belongs to technical field of optical fiber sensing, particularly a kind of gas concentration detection method and equipment that absorbs based on evanescent wave in the annular optical fiber laser chamber.
Background technology
Along with human civilization advance, atmosphere resource and all gases become the people's attention point.On the one hand, atmospheric pollution has become one of problem that people pay close attention to the most, presses for the effective monitoring to various harmful, poisonous, inflammable, the explosive gas that produces in industry, the transportation; On the other hand, when utilizing all gases, such as the gas system of using in the exploitation of various rock gases, coal gas, liquefied gas and use or the space industry, it is indispensable that the concentration of all gases is detected.
(compact conformation, be easy to make system, anti-electromagnetic interference (EMI) with fiber optic network) is subject to people's attention fiber gas sensor day by day because its many-sided advantage.Therefore, recent two decades comes Fibre Optical Sensor to emerge a lot of application schemes aspect gas sensing, as utilizes the fiber spectrum absorption process of Lambert-Beer law and improved chamber internal absorbent method on this principle.Said method often need to utilize the method for geometrical optics increase light in gas to be measured stroke or the device that adopts non-optical fiber compatibility improving measuring accuracy, this is integrated and encapsulation is very unfavorable to sensor.
Summary of the invention
The present invention is directed to the deficiencies in the prior art, proposed a kind of gas concentration detection method and equipment that is easy to integrated and encapsulation based on evanescent wave absorption in the annular optical fiber laser chamber.
Method of the present invention may further comprise the steps:
(1) general single mode fiber is added hot-stretch, obtain one section cross-sectional diameter D and be 1～3 micron, length L and be 5～15 centimetres tapered fiber; Tapered fiber is installed in the air chamber, and the outside is stayed at the two ends of tapered fiber.
(2) according to the spectral absorption peak of gas to be measured, select fiber amplifier, tunable optic filter, isolator, coupling mechanism, the photo-detector of forming annular optical fiber laser for use, the bandwidth of operation of the gain bandwidth (GB) of fiber amplifier, adjustable filter tuning range, isolator and coupling mechanism and photo-detector covers an absorption peak of gas to be measured at least, coupling mechanism coupling ratio scope is 99: 1～999: 1, and the coupling arm of coupling mechanism small component is as laser output.
(3) when the bandwidth of operation of gain bandwidth (GB), adjustable filter tuning range, isolator and the coupling mechanism and the photo-detector of fiber amplifier covers absorption peak of gas to be measured, open fiber amplifier, regulate tunable optic filter, make laser output wavelength drop on the absorption peak of gas to be measured.During fiber laser work, flashlight is concussion back and forth in resonator cavity, during through tapered fiber, the evanescent wave hangover is exposed in the gas to be measured, because signal light wavelength just in time drops on the gas absorption peak, luminous energy is by gas absorption loss to be measured, and the loss equation satisfies the Lambert-Beer law:
I＝I
0exp(-arnL)，(1)
Wherein, I is the emergent light light intensity, I
0Be the incident light light intensity, a is an absorption coefficient, and r is that the evanescent wave hangover accounts for total luminous energy ratio, and n is a gas concentration, and L is effective light path of flashlight process in gas to be measured.From formula (1) as can be seen, laser chamber internal loss coefficient and gas concentration are linear.Because it is relevant with the laser chamber damage that laser instrument goes out luminous power, so the luminous power size has reflected the gas concentration size.
(4) in air chamber, charge into the sample gas under study of different concentration known, detect corresponding laser output intensity, determine concentration and laser output intensity relation; Consider measurement for light concentration gas, can think the linear of gas concentration and Output optical power.Utilize the gas sample of normal concentration, measure the output laser power of each gas concentration correspondence, the data that record are carried out linear fit, obtain linear relationship:
I＝An+B，(2)
Wherein, I is a laser output power, and n is a gas concentration.According to formula (2), the laser optical power that is measured by photo-detector can obtain corresponding gas concentration.
(5) will need the gas to be measured of detectable concentration to charge into air chamber,, determine gas concentration to be measured by measuring laser output intensity according to step (4) calibration result.
When the bandwidth of operation of the gain bandwidth (GB) of described fiber amplifier, adjustable filter tuning range, isolator and coupling mechanism and photo-detector also can cover a plurality of absorption peak of gas to be measured, determine the gas concentration to be measured and the laser output intensity relation of corresponding each absorption peak according to step (4), to need the gas to be measured of detectable concentration to charge into air chamber again, determine gas concentration to be measured by measuring laser output intensity, can obtain accurate more result.
The equipment of realizing such scheme comprises fiber amplifier, tunable optic filter, isolator, coupling mechanism, is installed in tapered fiber, photo-detector in the air chamber.The output terminal of fiber amplifier is connected with an end light of adjustable filter, and an end light of the tapered fiber that the other end of adjustable filter is interior with being installed in air chamber is connected.The other end of tapered fiber is connected with the input end light of isolator, and the output terminal of isolator is connected with the input end light of coupling mechanism, and the coupling arm of the big component of coupling mechanism is connected with the input end light of fiber amplifier.So far fiber amplifier, adjustable filter, tapered fiber, isolator, coupling mechanism looping fiber laser, the coupling arm of coupling mechanism small component is connected with light detector as laser output.
The present invention mainly is applicable to the high-acruracy survey that low concentration (volume ratio 1～5%) gas at spectral absorption peak is arranged at optical communicating waveband.The present invention has adopted the equipment of optical fiber compatibility, and compact conformation is easy to integratedly, can do remote sensing; Use tapered fiber, made that the horizontal xsect overlapping area of evanescent wave and gas is big as far as possible, helped improving sensing accuracy; Adopt in the laser chamber to absorb, increased effective absorption length greatly, improved sensing accuracy; In laser instrument, adopt the wavelength tuning technology, can measure the different absorption peaks of same gas, help improving precision, also can measure the concentration of gas with various.Simultaneously, the present invention is also with advantages such as anti-electromagnetic interference capability are strong.
Description of drawings
Fig. 1 is an one-piece construction synoptic diagram of the present invention;
Fig. 2 is the partial enlarged drawing of Fig. 1.
Embodiment
As illustrated in fig. 1 and 2, the output terminal of fiber amplifier 5 is connected with an end light of adjustable filter 4, the other end of adjustable filter 4 is connected with an end light of tapered fiber 3 in being installed in air chamber 2, the other end of tapered fiber 3 is connected with the input end light of isolator 1, the output terminal of isolator 1 is connected with the input end light of coupling mechanism 7, the coupling arm of coupling mechanism 1 big component is connected with the input end light of fiber amplifier, so far fiber amplifier 5, adjustable filter 4, tapered fiber 3, isolator 1, coupling mechanism 7 looping fiber lasers.The coupling arm of coupling mechanism 1 small component is connected with photo-detector 6 light as laser output.The diameter of tapered fiber is that 2 microns, length are 10 centimetres.
Gas to be measured is carbon dioxide, a corresponding spectral absorption peak is 1.538 microns, and selecting Erbium-Doped Fiber Amplifier (EDFA) (gain bandwidth (GB) is 1.525～1.58 microns), tuning bandwidth for use is that isolator, coupling mechanism, the photo-detector that 1.525～1.58 microns tunable optic filter and bandwidth of operation are 1.5～1.6 microns formed the gas concentration lwevel checkout equipment.
At first in the laboratory, the gas concentration lwevel checkout equipment is calibrated.Open fiber amplifier, fiber laser begins bright dipping, regulates wave filter and makes laser output wavelength drop on 1.538 microns absorption peaks of gas to be measured.In air chamber, charge into the gas of various normal concentrations, the corresponding laser power that the recording light detector records.The data that record are carried out linear fit, obtain coefficient A and B in the formula (2), determine the corresponding relation curve of laser output power and gas concentration.So far calibration is finished.
Pick-up unit is installed in mine, tunnel, gas station etc. measures the place, ambient atmos is charged into air chamber, measure optical power value with photo-detector, the formula (2) that utilizes above-mentioned match to calibrate obtains the gas concentration of tested gas.
Claims (3)
1,, it is characterized in that this method may further comprise the steps based on the gas concentration detection method of annular optical fiber laser:
(1) general single mode fiber is added hot-stretch, obtain one section cross-sectional diameter D and be 1～3 micron, length L and be 5～15 centimetres tapered fiber; Tapered fiber is installed in the air chamber, and the outside is stayed at the two ends of tapered fiber;
(2) according to the spectral absorption peak of gas to be measured, select fiber amplifier, tunable optic filter, isolator, coupling mechanism, the photo-detector of forming annular optical fiber laser for use, the bandwidth of operation of the gain bandwidth (GB) of fiber amplifier, adjustable filter tuning range, isolator and coupling mechanism and photo-detector covers an absorption peak of gas to be measured at least, and the coupling arm of coupling mechanism small component is as laser output;
(3) when the bandwidth of operation of gain bandwidth (GB), adjustable filter tuning range, isolator and the coupling mechanism and the photo-detector of fiber amplifier covers absorption peak of gas to be measured, regulate tunable optic filter, make laser output wavelength drop on the absorption peak of gas to be measured;
(4) in air chamber, charge into the sample gas under study of different concentration known, detect corresponding laser output intensity, determine concentration and laser output intensity relation;
(5) will need the gas to be measured of detectable concentration to charge into air chamber,, determine gas concentration to be measured by measuring laser output intensity according to (4) calibration result.
2, the gas concentration detection method based on annular optical fiber laser as claimed in claim 1, when the bandwidth of operation that it is characterized in that gain bandwidth (GB), adjustable filter tuning range, isolator and the coupling mechanism and the photo-detector of described fiber amplifier covers a plurality of absorption peak of gas to be measured, determine the gas concentration to be measured and the laser output intensity relation of corresponding each absorption peak according to step (4), to need the gas to be measured of detectable concentration to charge into air chamber again, determine gas concentration to be measured by measuring laser output intensity.
3, adopt claim 1 or the employed equipment of 2 methods, the output terminal that it is characterized in that fiber amplifier is connected with an end light of adjustable filter, one end light of the tapered fiber that the other end of adjustable filter is interior with being installed in air chamber is connected, the other end of tapered fiber is connected with the input end light of isolator, and the output terminal of isolator is connected with the input end light of coupling mechanism; The coupling arm of the big component of coupling mechanism is connected with the input end light of fiber amplifier, and the coupling arm of coupling mechanism small component is connected with light detector as laser output; Described tapered fiber diameter D is that 1～3 micron, length L are 5～15 centimetres.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 200510097004 CN1793850A (en) | 2005-12-31 | 2005-12-31 | Gas concentration detection method and equipment based on ring-shaped optical fiber laser |
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| CN 200510097004 CN1793850A (en) | 2005-12-31 | 2005-12-31 | Gas concentration detection method and equipment based on ring-shaped optical fiber laser |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101871879A (en) * | 2010-07-16 | 2010-10-27 | 中南大学 | Trace gas detection method based on micro resonance loop array spectrum-dividing technology and detector |
| CN103457674A (en) * | 2013-08-22 | 2013-12-18 | 暨南大学 | Infinite impulse response microwave photon filter and filtering method |
| WO2018119671A1 (en) * | 2016-12-27 | 2018-07-05 | 深圳大学 | Measurement device and measurement method for concentration of contaminants in water |
| CN113029957A (en) * | 2021-03-31 | 2021-06-25 | 中国科学院长春光学精密机械与物理研究所 | Gas sensor based on evanescent wave |
-
2005
- 2005-12-31 CN CN 200510097004 patent/CN1793850A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101871879A (en) * | 2010-07-16 | 2010-10-27 | 中南大学 | Trace gas detection method based on micro resonance loop array spectrum-dividing technology and detector |
| CN103457674A (en) * | 2013-08-22 | 2013-12-18 | 暨南大学 | Infinite impulse response microwave photon filter and filtering method |
| CN103457674B (en) * | 2013-08-22 | 2017-03-01 | 暨南大学 | A kind of infinite impulse response microwave photon filter and filtering method |
| WO2018119671A1 (en) * | 2016-12-27 | 2018-07-05 | 深圳大学 | Measurement device and measurement method for concentration of contaminants in water |
| US10502681B2 (en) | 2016-12-27 | 2019-12-10 | Shenzhen University | Apparatus and method for measuring concentration of pollutants in water |
| CN113029957A (en) * | 2021-03-31 | 2021-06-25 | 中国科学院长春光学精密机械与物理研究所 | Gas sensor based on evanescent wave |
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