基于多光程吸收池的可调谐半导体激光吸收光谱 (TDLAS) 系统在检测过程中容易出现噪声干扰, 影响着其实际检测性能。针对这种干扰的特征进行分析, 提出利用小波降噪法来改善 TDLAS 系统的探测性能。首先依据理论研究结果选择合适的小波函数和分解层数, 然后通过这种小波对叠加干扰的仿真信号进行滤波, 结果表明这种降噪技术具有良好的去噪效果。最后利用小波降噪技术处理了实验采集的不同浓度气体的直接吸收光谱 (DAS) 和二次谐波信号, 相比于原信号, 降噪后信号的信噪比从 0.4 增加到 259, 系统的检测限也达到 7×10-6, 表明小波降噪方法在气体光谱检测中具有较高的应用价值。

The TDLAS system combined with multi-path absorption cell is prone to interference noise in practical application, which has a very adverse impact on its detection performance. In this work, the causes of this interference are analyzed, and a wavelet denoising method is proposed to improve the detection performance of the system. Firstly, the appropriate wavelet function and decomposition layers are selected according to the theoretical research results, and then the simulation signal with superimposed interference is filtered through this wavelet. The results show that this noise reduction technology has good application performance. Finally, the direct absorption spectrum (DAS) and second harmonic signal of each carbon dioxide concentration collected in the experiment are processed by wavelet denoising technology. Compared with the original signal, the signal-to-noise ratio of the denoised signal is increased from 0.4 to 259, and the detection limitof the system reaches 7×10-6, which indicates that the proposed small wave noise reduction method has high application value in the detection of ambient gases.