基于可调谐激光二极管吸收光谱的乙炔在线检测系统

摘要

基于可调谐半导体激光吸收光谱技术，研制了一种近红外乙炔气体检测系统。通过分析近红外波段乙炔分子的吸收谱线特性，选择了1.534μm附近乙炔分子的吸收峰作为吸收谱线。该系统主要由分布反馈激光器、激光器驱动器、单光程对射式气室、光电探测模块及数字式锁相放大器构成。为了测试该检测系统的性能，配备了乙炔气体样品并开展了气体检测实验。实验结果显示，该系统的最小检测下限为0.02%；在体积分数为0.02%~1%范围内，二次谐波幅值与乙炔气体浓度呈现出良好的线性关系。通过长达20 h的稳定性实验测试了检测系统稳定性。鉴于近红外波段石英光纤传输损耗很小，可以将气室及光路部分与电路部分分离，从而可以进行远程气体检测，这是基于量子级联激光器、热光源的乙炔检测系统难以实现的。该系统采用了自主研制的分布反馈激光器驱动器和锁相放大器，结构简单，性价比高，便与集成，在工业现场乙炔浓度检测方面有着良好的应用前景。%Based on tunable diode laser absorption spectroscopy (TDLAS)technique,an acetylene (C2 H2 )online detection sys-tem was developed by using the absorption band at the wavelength of 1.534μm of C2 H2 molecule.The sensing system consists of four modules including a distributed feedback (DFB)laser,a DFB laser driver,a gas cell with single optical path and a data processing module.With the prepared standard C2 H2 gas sample,detailed measurements were carried out to study the detection performance of the system.Experimental results reveal that,the limit of the system (LOD)is about 0.02%;a good linear rela-tionship is observed between C2 H2 gas concentration and the amplitude of the 2f signal is within the range of 0.02%~1%.A long-term measurement lasting for 20 h on a 0.5% C2 H2 gas sample was carried out to test the stability of the system.Compared with the C2 H2 detection systems utilizing quantum cascaded lasers (QCLs)and wideband incandescence,this system has great advantage due to the capability of using long-distance and low-loss optical fiber for remote monitoring.With self-developed DFB laser driver and lock-in amplifier,the system has good prospects in industrial field because of its simple structure,low price and capability of easy to be integrated.