基于多模激光吸收光谱的CO浓度高灵敏度测量
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摘要
为提高多模激光吸收光谱技术的探测灵敏度,采用1 570nm多模二极管激光器为光源,以程长为100m的离散镜片型多通池作为气体吸收池,将多模二极管激光关联光谱技术、波长调制技术和长程吸收技术相结合,建立了一套具有高检测灵敏度和高稳定性的气体分子光谱测量系统。实验中将多模激光分成两束,一束作为参考光通过已知目标气体浓度的参考池,另一束通过混有待测气体的测量池,测量光信号和参考光信号被同时探测和解调。通过计算待测气体和参考池气体之间二次谐波信号峰值高度之间的关系,反演出CO的浓度。利用该装置测量了CO气体在1 570nm附近的近红外吸收光谱。实验表明,CO浓度测量值与真实浓度值之间具有良好的线性关系,线性度为0.9995,平均偏差为1.19%,对CO的探测极限为37.3×10-6,对同一样品在30min内的30次连续测量的标准偏差为0.839%,表明了系统良好的稳定性。
A multi-mode laser absorption spectroscopy system with high detection sensitivity and high stability is built using an F-P multi-mode diode laser near 1570nm as the light source.In order to improve the detection limit of the system,a discrete lens-type multi-pass cell with path length of 100mis employed as the measurement absorption cell.The multi-mode diode laser correlation spectroscopy,wavelength modulation technology and long-path absorption spectroscopy are combined to improve the performance of the system.In the experiment,the laser beam is spitted into two parts,which pass through the reference cell and measurement cell,respectively.The measuring light and the reference light signals are detected simultaneously.The performance of the system is validated by measuring the concentration of carbon monoxide(CO).The CO concentrations are derived from the relationship between the normalized WMS-2fsignal peak heights of the measurement and reference signals which are selected based on high signal to noise ratio and correlation coefficient.The calculation results show that there is a highly linear relationship between the measured and actual CO concentrations,and the linearity is 0.999 5over the whole tested range.A detection limit of 37.3ppm is achieved.The standard deviation of 0.839%is obtained using 30successive measurements with each measurement time of~10sduring 30min,which demonstrates the good stability of the system.
A multi-mode laser absorption spectroscopy system with high detection sensitivity and high stability is built using an F-P multi-mode diode laser near 1570nm as the light source.In order to improve the detection limit of the system,a discrete lens-type multi-pass cell with path length of 100mis employed as the measurement absorption cell.The multi-mode diode laser correlation spectroscopy,wavelength modulation technology and long-path absorption spectroscopy are combined to improve the performance of the system.In the experiment,the laser beam is spitted into two parts,which pass through the reference cell and measurement cell,respectively.The measuring light and the reference light signals are detected simultaneously.The performance of the system is validated by measuring the concentration of carbon monoxide(CO).The CO concentrations are derived from the relationship between the normalized WMS-2fsignal peak heights of the measurement and reference signals which are selected based on high signal to noise ratio and correlation coefficient.The calculation results show that there is a highly linear relationship between the measured and actual CO concentrations,and the linearity is 0.999 5over the whole tested range.A detection limit of 37.3ppm is achieved.The standard deviation of 0.839%is obtained using 30successive measurements with each measurement time of~10sduring 30min,which demonstrates the good stability of the system.
引文
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[2]ZHANG Zhi-rong,DONG Feng-zhong,WU Bian,et al.Insuit measurement of HF gas in industrial situation based on TDLAS technology[J].Journal of Optoelectronics·Laser,2011,22(11):1691-1694.张志荣,董凤忠,吴边,等.基于TDLAS技术的工业环境中HF气体在线监测[J].光电子·激光,2011,22(11):1691-1694.
[3]JIANG Ning.Study a multi-channel distributed fiber optic gas monitoring system[J].Journal of Optoelectronics·Laser,2013,24(2):316-322.姜宁.多通道光纤可燃气体监测系统的研究[J].光电子·激光,2013,24(2):316-322.
[4]YE Wei-lin,ZHENG Chuan-tao,WANG Yi-ding.Experimental research on wavelet denoising in infrared humidity detection based on TDLAS technique[J].Journal of Optoelectronics·Laser,2013,24(1):104-111.叶玮琳,郑传涛,王一丁.基于TDLAS的红外湿度检测中的小波去噪实验研究[J].光电子·激光,2013,24(1):104-111.
[5]WANG Ren-bao,FENG Hong-yan.Laser absorption spectrome-ter methane detection system based on digital processor[J].Journal of Optoelectronics·Laser,2010,21(1):38-41.王仁宝,冯红艳.基于数字信号处理的激光光谱瓦斯监测系统[J].光电子·激光,2010,21(1):38-41.
[6]Lin X,Yu X L,Li F,et al.CO concentration and temperature measurements in a shock tube for Martian mixtures by coupling OES and TDLAS[J].Applied Physics B,2013,110(3):401-409.
[7]Grant Richard H,Boehm Matthew T,Lawrence A F,et al.Ammonia emissions from anaerobic treatment lagoons at sow and finishing farms in Oklahoma[J].Agricultural and Forest Meteorology,2013,180(10):203-210.
[8]SONG Fang,LI Guo-lin,SONG Nan,et al.Design and implementation of differential mid-infrared carbon monoxide detector[J].Optoelectronics Letters,2013,9(5):385-388.
[9]Somesfalean G,Sjoholm M,Persson L,et al.Temporal correlation scheme for spectroscopic gas analysis using multimode diode lasers[J].Applied Physics Letters,2005,86(18):184102-184103.
[10]Lou X T,Somesfalean G,Chen B,et al.Oxygen measurement by multimode diode lasers employing gas correlation spectroscopy[J].Applied Optics,2009,48(5):990-997.
[11]Hamilton M L,Ritchie G A D,Arita Y,et al.Multi-mode absorption spectroscopy,MUMAS,using wavelength modulation and cavity enhancement techniques[J].Applied Physics B,2010,100(8):665-673.
[12]Vargas-Rodrígueza E,Ruttb H N.Design of CO,CO2and CH4gas sensors based on correlation spectroscopy using a Fabry-Perot interferometer[J].Sensors and Actuators B:Chemical,2009,137(2):410-419.
[13]Thomas B,Miffre A,Dabid G,et al.Remote sensing of trace gases with optical correlation spectroscopy and lidar:theoretical and numerical approach[J].Applied Physics B,2012,108(3):689-702.
[14]Wang B,Somesfalean G,Mei L,et al.Detection of gas concentration by correlation spectroscopy using a multiwavelength fiber laser[J].Progress In Electromagnetics Research,2011,114(3):469-479.
[15]Lou X T,Somesfalean G,Xu F,et al.Gas sensing by tunable multimode diode laser using correlation spectroscopy[J].Applied Physics B,2008,93(2-3):671-676.
[16]Lou X T,Somesfalean G,Chen B,et al.Simultaneous detection of multiple-gas species by correlation spectroscopy using a multimode diode laser[J].Optics Letters,2010,35(11):1749-1751.
[17]Stewart George,Johnstone Walter,Bain James R P,et al.Recovery of absolute gas absorption line shapes using tunable diode laser spectroscopy with wavelength modulation—part I:Theoretical analysis[J].Journal of Lightwave Technology,2011,29(6):811-821.
[18]PENG Zhin-min,DING Yan-jun,JIA Jun-wei,et al.First harmonic with wavelength modulation spectroscopy to measure integrated absorbance under low absorption[J].Optics Express,2013,21(20):23724-23735.
[19]Krzempek K,Lewicki R,N¨ahle L,et al.Continuous wave,distributed feedback diode laser based sensor for tracegas detection of ethane[J].Applied Physics B,2012,106(2):251-255.
[20]Li D J,Yang G L,Chen F,et al.Stimulated rotational roman scattering at multiwavelength under TEA CO2laser pumping with a multiple-pass cell[J].Laser Physics,2012,22(15):937-940.
[21]Manninen A,Tuzson B,Looser H,et al.Versatile multipass cell for laser spectroscopic trace gas analysis[J].Applied Physics B,2012,109(3):461-466.
[22]Lou X T,Xu C,Svanberg S,et al.Multimode diode laser correlation spectroscopy using gas-filled porous materials for pathlength enhancement[J].Applied Physics B,2012,109(3):453-460.
[23]Northern J H,Thompson A W J,Hamilton M L,et al.Multispecies detection using multi-mode absorption spectroscopy(MUMAS)[J].Applied Physics B,2013,111(6):627-635.