CN101936878B - Photo-acoustic spectrum gas detecting system based on distributed feedback optical fiber laser - Google Patents
Photo-acoustic spectrum gas detecting system based on distributed feedback optical fiber laser Download PDFInfo
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- CN101936878B CN101936878B CN2010102386179A CN201010238617A CN101936878B CN 101936878 B CN101936878 B CN 101936878B CN 2010102386179 A CN2010102386179 A CN 2010102386179A CN 201010238617 A CN201010238617 A CN 201010238617A CN 101936878 B CN101936878 B CN 101936878B
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Abstract
The invention discloses a photo-acoustic spectrum gas detecting system based on a distributed feedback optical fiber laser, belonging to the gas detection technologies. The photo-acoustic spectrum gas detecting system comprises a coherent light source, a distributed feedback optical fiber laser and the like, wherein the coherent light source is connected with a modulator through a self-supplied tail fiber, and the modulator is connected to a photoacoustic cell through a common optical fiber to form a sound signal excitation optical path; a 980 pump semiconductor laser is connected with a 980nm end of a wavelength division multiplexer through the tail fiber to form a detection optical path with a subsequent optical path. The invention is characterized in that the distributed feedback optical fiber laser is used as a sensor for probing sound and fixed in the photoacoustic cell, and one end thereof is connected to a common end of the wavelength division multiplexer through the common optical fiber; an 1550nm end of the wavelength division multiplexer is connected with an isolator; an output end of the isolator is connected with a wavelength demodulation system of the far end through the common optical fiber. The photo-acoustic spectrum gas detecting system can be normally used in the environment of strong electromagnet and radioactivity, can be used for detecting a special gas environment, and is convenient for forming a network by multiplexing a plurality of the systems so as to realize remote monitoring of multiple points.
Description
Technical field
The present invention relates to a kind of optoacoustic spectroscopy gas detecting system based on distributed feedback optical fiber laser (DFB-FL) of full optics, specifically is a kind of system that utilizes distributed feedback optical fiber laser to carry out the optoacoustic spectroscopy gas detection as the optics microphone.
Background technology
Optoacoustic effect is based on the effect that inspires sound wave after the material absorbing light modulated by radiationless hot relaxation heat release, has just found optoacoustic effect as far back as Bell in 1880 etc.Carry out in the absorption spectroscopy that gas concentration detects many, optoacoustic spectroscopy has the following advantages: test specification is wide.Photoacoustic technique is the light energy signal that detection material directly absorbs by radiationless transition, rather than the light energy signal of sample is crossed in the measurement transmission, sample is to reflection of incident light like this, scattering can not have influence on measurement result, the sample of fully opaque and high scattering is energy measurement also, measurement range almost spreads all over all states of sample, such as: gas, liquid, Gu, gel, powder, film, colloid etc., but early stage because optoacoustic effect too a little less than, unanimity does not obtain paying attention to, up to the 20 actual seventies, development along with laser technology and feeble signal Detection Techniques, particularly Kreuzer in 1971 utilizes tunable laser to do light source, record the gas absorption spectrum that concentration is low to moderate 10-7 μ g/L, and analyzed the use LASER Light Source theoretically and high sensitivity feeble signal detector can reach 10 to the gas optoacoustic spectroscopy detection limit order of magnitude
-13, after this, photoacoustic spectroscopy is developed rapidly.Another advantage is exactly: photoacoustic signal intensity is directly proportional with incident intensity under the situation that absorption of sample luminous energy does not reach capacity, and along with the development of laser technology, the energy that improves incident light becomes relatively easy to increase detection sensitivity.
Because outstanding advantages such as the high sensitivity that the photoacoustic spectroscopy instrument has, great dynamic range, detection in real time, make people very big interest be arranged to the optoacoustic spectroscopy detection technique, continually develop new light sources, research sound sensing technology and Detection of Weak Signals technology, improve the optoacoustic spectroscopy theory, making analyser various aspects of performance based on optoacoustic spectroscopy have significantly improves, in recent years, on industrial and agricultural production, environmental monitoring, military battlefield, many gas-detecting devices based on optoacoustic spectroscopy had been developed in minimum gas monitoring field in succession.The optoacoustic spectroscopy gas analyzer mainly is made up of six parts: monochromatic source, modulator, photoacoustic cell, sonic transducer, signal amplify and detect data recording and transmission.The photo-acoustic spectrometer of commercial typing seldom generally need design voluntarily according to research object and breadboard condition in actual applications and build.The photoacoustic signal that optoacoustic effect excites is surveyed by highly sensitive sonic transducer, uses electret formula capacitor microphone usually.Its monochromatic source of photo-acoustic spectrometer of general design, the amplification and the detection system of signal are positioned at the scene, but at some special occasions, as 1) strong magnetoelectricity and radioactive environment, because physical characteristics is restricting the operation of common microphone, the influence of outside strong-electromagnetic field can cause the forfeiture of these functions of the equipments even destroy them.Traditional microphone comprises capacitor, electret and dynamic microphone, uses to rely on the electronic circuit that contains capacitor or coil.These electronic packages in microphone are highstrung to interference electronics or electromagnetism; 2) gas environment is such as in the colliery excavation site.Electric spark is forbidden occurring in the scene, this means exciting of coherent source to be placed on long-rangely, with the long-range placement of light source, imports in the photoacoustic cell by optical fiber, and there is the hidden danger of safety in the microphone that also just means electronics; 3) detect in the application in environmental contaminants monitoring and battlefield surroundings toxicity, because gas detection equipment dispersed placement, the scene often can not provide power supply, this just need provide on-the-spot passive, structure is small and exquisite, integrated level and the high photoacoustic cell of high sensitivity, and is convenient with what realize detecting.
＜Proceedings of the CSEE〉2008,28 (34): p40～46. authors are Yun Yuxin, Chen Weigen, Sun Caixin, Pan's Chong, name is called in " the optoacoustic spectroscopy detection method of methane gas in the transformer oil " article and has proposed a kind of novel micro gas detection technology based on optoacoustic effect, have highly sensitive, selectivity is good, advantages such as dynamic detection range is big, but this detection technique is subject to measurement environment, when having outside electromagnetic field, badly influence measuring accuracy, even the function of checkout equipment can be lost.
Summary of the invention
In order to overcome defective and the deficiency that prior art exists, the present invention proposes a kind of optoacoustic spectroscopy gas detecting system of full optics based on distributed feedback optical fiber laser (DFB-FL).
Technical scheme of the present invention realizes in the following manner:
A kind of optoacoustic spectroscopy gas detecting system based on distributed feedback optical fiber laser, comprise coherent source, modulator, photoacoustic cell, 980 pumping semiconductor lasers (LD), wavelength division multiplexer (WDM), distributed feedback optical fiber laser (DFB-FL), isolator (ISO) and Wavelength demodulation system, coherent source is connected to modulator by carrying tail optical fiber, modulator is connected to the photoacoustic cell of gaseous environment by long ordinary optic fibre, the periodically variable monochromatic light of light intensity acts on gas to be measured, produce small sound, form the voice signal excitation light path; 980 pumping semiconductor lasers are connected and subsequent optical path composition detection light path by the 980nm end of tail optical fiber and wavelength division multiplexer, it is characterized in that distributed feedback optical fiber laser is fixed in the photoacoustic cell as the sensor of surveying sound, the one end is connected on the common port of wavelength division multiplexer through ordinary optic fibre; The 1550nm end of wavelength division multiplexer is connected with isolator, and the isolator output terminal is connected through the Wavelength demodulation system of ordinary optic fibre and far-end.
Described Wavelength demodulation system is general wavelength demodulation device, and the model of producing as U.S. Optiphase company is the wavelength demodulation device of OPD-4000.
Gas detecting system of the present invention in use, photoacoustic cell in the system of the present invention placed the gaseous environment that need to detect or with gas extraction to photoacoustic cell, utilize the microphone of the distributed feedback optical fiber laser of full optical fiber as small sound transducer replacement electronics, when monochromatic light enters photoacoustic cell, behind the gas absorption light to be measured, produce small sound, acoustic pressure causes the drift of DFB-FL wavelength, thereby determine acoustic pressure by the drift that detects wavelength, and then release the concentration of gas.Specifically be after coherent source produces monochromatic light, by modulator, light intensity produces periodic the variation, by be connected to the photoacoustic cell of far-end than long ordinary optic fibre, injects photoacoustic cell, with gas effect to be measured, produces sound.The semiconductor laser of 980nm is connected with the 980nm end of WDM, and the common port output from WDM is connected to DFB-FL by long ordinary optic fibre, and 1550 ends of WDM are linked on the isolator, and the isolator output terminal is connected to Wavelength demodulation system.
The used optoacoustic spectroscopy gas detection principle of prior art is shown in figure (1), coherent source gives off can be by the monochromatic light of gas absorption to be measured, become the monochromatic light of light intensity periodically-varied through the modulation of modulator, enter photoacoustic cell, behind the gas absorption monochromatic light, cause its radiationless relaxation of periodicity, show as the cyclical variation of pressure on the macroscopic view, promptly form sound wave; Sonic transducer changes it into electric signal after detecting pressure wave, and this electric signal is detected by lock-in amplifier or Boxcar integrator, and notes, and also can give remote computer analyzing and processing or deposit.
Concrete action principle of the present invention is as follows: the semiconductor laser of 980nm, produce the laser of 980nm, enter DFB-FL by WDM, as pump light, excite DFB-FL, produce near the laser of the narrow linewidth of 1550nm, when sound affacts on the DFB-FL, the wavelength shift of DFB-FL, the monochromatic light of the be detected gas absorption that coherent source produces, the laser of formation light intensity periodically-varied after ovennodulation, after entering photoacoustic cell, by gas absorption, produce sound wave, be subjected to the influence of acoustic pressure, the wavelength of packaged DFB-FL is the change of generating period also, because the filter action of WDM, the DFB-FL light of forward direction only enters isolator (ISO), enters Wavelength demodulation system again, we can come out the wavelength change demodulation, wavelength change has been reacted the intensity of acoustic pressure like this, and the concentration of the intensity of acoustic pressure and gas has direct relation, can express the concentration of gas by suitable algorithm.
The present invention has following advantage: have the highly sensitive while of optoacoustic spectroscopy method, no electronic package is connected on the fibre-optical probe, and any electro permanent magnetic or electrostatic interference are inoperative to microphone, can normally use in forceful electric power magnetic, radioactive environment; The sound-detection system of full optical fiber does not have an effect with flammable explosive gas such as gas, can be used for the detection of special gas environment; Based on the system of optical fiber, be convenient to a plurality of multiplexingly, form network, realize the remote monitor of multiple spot.
Description of drawings
Fig. 1 is the structural representation of prior art optoacoustic spectroscopy gas detection.
Wherein: 1, coherent source, 2, modulator, 3, photoacoustic cell, 4, microphone, 5, signal amplify and the test section, and 6, data recording and hop.
Fig. 2 is the structural representation of gas detecting system of the present invention.
Wherein: 7, coherent source, 8, modulator, 9, ordinary optic fibre, 10, photoacoustic cell, 11,980nm diode-end-pumped, 12, wavelength division multiplexer (WDM), 13, ordinary optic fibre, 14, distributed feedback optical fiber laser (DFB-FL), 15, isolator (ISO), 16, Wavelength demodulation system.
Embodiment
The present invention will be further described below in conjunction with drawings and Examples, but be not limited thereto.
Embodiment:
The embodiment of the invention as shown in Figure 2, comprise coherent source 7, modulator 8, photoacoustic cell 10,980 pumping semiconductor lasers (LD) 11, wavelength division multiplexer (WDM) 12, distributed feedback optical fiber laser (DFB-FL) 14, isolator (ISO) 15 and Wavelength demodulation system 16, coherent source 7 is connected with modulator 8 by carrying tail optical fiber, modulator 8 is connected to the photoacoustic cell 10 of far-end by longer ordinary optic fibre 9, the periodically variable laser action of light intensity of output is in gas to be measured, produce small sound, form the voice signal excitation light path; 980 pumping semiconductor laser (LD) 11 are connected and subsequent optical path composition detection light path by the 980nm end of tail optical fiber and wavelength division multiplexer (WDM) 12, it is characterized in that distributed feedback optical fiber laser (DFB-FL) 14 is fixed on 10 li of photoacoustic cells as the sensor of surveying sound, on the common port of the wavelength division multiplexer (WDM) 12 of one end through be connected to far-end than long ordinary optic fibre 13; The 1550nm end of wavelength division multiplexer (WDM) 12 is connected with isolator (ISO) 15, and isolator (ISO) 15 output terminals are connected with Wavelength demodulation system 16 through ordinary optic fibre.
Claims (1)
1. optoacoustic spectroscopy gas detecting system based on distributed feedback optical fiber laser, comprise coherent source, modulator, photoacoustic cell, 980 pumping semiconductor lasers, wavelength division multiplexer, distributed feedback optical fiber laser, isolator and Wavelength demodulation system, coherent source is connected to modulator by the tail optical fiber that carries, modulator is connected to photoacoustic cell in the gaseous environment by ordinary optic fibre, the periodically variable monochromatic light of light intensity acts on gas to be measured, produce small sound, form the voice signal excitation light path; 980 pumping semiconductor lasers are connected by the 980nm end of tail optical fiber and wavelength division multiplexer, form the detection light path with distributed feedback optical fiber laser, isolator and the Wavelength demodulation system of rear end, it is characterized in that distributed feedback optical fiber laser is fixed in the photoacoustic cell as the sensor of surveying sound, the one end is connected on the common port of wavelength division multiplexer through ordinary optic fibre; The 1550nm end of wavelength division multiplexer is connected with isolator, and the isolator output terminal is connected through the Wavelength demodulation system of ordinary optic fibre and far-end.
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| CN102175614A (en) * | 2011-01-28 | 2011-09-07 | 华南理工大学 | Optical fiber coupled optoacoustic integrated detecting probe |
| CN102175615A (en) * | 2011-01-28 | 2011-09-07 | 华南理工大学 | Optical fiber coupling photoaccoustic detection probe and positioning method of target to be measured thereof |
| CN103472002B (en) * | 2013-09-27 | 2016-03-02 | 山东大学 | Photoacoustic spectroscopy gas detecting system in a kind of fiber laser cavity |
| CN107543794A (en) * | 2017-09-11 | 2018-01-05 | 山东大学 | Photoacoustic spectroscopy gas detecting system based on double grating Q adjusting optical fiber laser |
| CN110470630B (en) * | 2018-05-11 | 2021-12-28 | 西安电子科技大学 | Distributed optical fiber gas sensor based on differential mode |
| CN113252572B (en) * | 2021-05-10 | 2022-05-13 | 大连理工大学 | Optical fiber tip type photoacoustic gas sensing system and method |
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| US6188341B1 (en) * | 1996-11-11 | 2001-02-13 | Fanuc Ltd. | Encoder interpolation circuit which corrects an interpolation angle between a received sine-wave encoder signal and a cosine-wave encoder signal |
| EP1308713A1 (en) * | 2001-11-02 | 2003-05-07 | Qmet ApS | A method of determining the content of SO2 in a beverage product |
| CN1928531A (en) * | 2006-09-12 | 2007-03-14 | 西南科技大学 | Method for detecting methane gas concentration with opto-acoustic spectroscopic method |
| CN101738382B (en) * | 2008-11-14 | 2013-09-18 | 香港理工大学 | Transformer failure gas monitoring system and method |
| CN101487818B (en) * | 2009-02-20 | 2012-06-27 | 国网电力科学研究院 | On-line monitoring method and system for gas content in transformer oil |
| CN201749080U (en) * | 2010-07-28 | 2011-02-16 | 山东大学 | Photoacoustic spectroscopy gas detection system based on distributed feedback fiber laser |
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