中国激光, 2020, 47 (6): 0611001, 网络出版: 2020-06-03
基于波长调制光谱和小波去噪的激光甲烷遥测系统 
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Laser Methane Remote Sensor System Based on Wavelength Modulation Spectroscopy and Wavelet Denoising
图 & 表
图 1. 基于WMS与WD的激光甲烷遥测系统结构图
Fig. 1. Schematic of the laser methane remote sensor system based on WMS and WD
图 2. MATLAB模拟得到的体积分数为100×10-6的甲烷气体的吸收信号和二次谐波信号。(a)理想吸收信号;(b)理想二次谐波信号;(c)含噪吸收信号;(d)含噪二次谐波信号;(e)去噪吸收信号;(f)去噪二次谐波信号
Fig. 2. Absorption signal and second harmonic signal simulated by MATLAB for methane sample with concentration of 100×10-6. (a) Ideal absorption signal; (b) ideal second harmonic signal; (c) polluted absorption signal; (d) polluted second harmonic signal; (e) denoised absorption signal; (f) denoised second harmonic signal
图 3. 采用基于EMD的小波去噪方法得到的甲烷气体的吸收信号和二次谐波信号。(a)吸收信号;(b)二次谐波信号
Fig. 3. Absorption signal of CH4 and the second harmonic signal denoised by the EMD-based WD. (a) Absorption signal; (b) the second harmonic signal
图 4. 甲烷气体积分浓度为200×10-6 m时,利用正交锁相放大器程序提取的二次谐波信号。(a)不采用小波去噪算法提取的二次谐波信号;(b)采用小波去噪算法提取的二次谐波信号
Fig. 4. Under a concentration level of 200×10-6 m, the extracted second harmonic signal using the lock-in amplifier program. (a) Extracted second harmonic without WD; (b) extracted second harmonic with WD
图 5. 利用正交锁相放大器程序提取的二次谐波信号的幅值随标定时间的变化曲线(甲烷气体的积分浓度为(0~200)×10-6 m,步进为50×10-6 m)。(a)无小波去噪算法的标定结果;(b)加入小波去噪算法的标定结果
Fig. 5. Relation curve of amplitude of the second harmonic signal are extracted by using an orthogonal lock-in amplifier program(the integral concentration levels of methane is (0--200)×10-6 m with an increase of 50×10-6 m for each sample). (a) Calibration result without WD; (b) the calibration result with WD
图 6. 实验标定结果和拟合曲线。(a)无小波去噪算法;(b)加入小波去噪算法
Fig. 6. Experimental calibration results and fitting curve. (a) Without WD; (b) with WD
图 7. 在氮气环境下,通过实验测得的系统的Allan标准差曲线。(a)不采用小波去噪算法;(b)采用小波去噪算法
Fig. 7. In nitrogen atmosphere, the measured Allan deviation curves. (a) Without WD; (b) with WD
周言文, 苗澍茁, 姚丹, 董明, 郑传涛, 王一丁. 基于波长调制光谱和小波去噪的激光甲烷遥测系统[J]. 中国激光, 2020, 47(6): 0611001. Zhou Yanwen, Miao Shuzhuo, Yao Dan, Dong Ming, Zheng Chuantao, Wang Yiding. Laser Methane Remote Sensor System Based on Wavelength Modulation Spectroscopy and Wavelet Denoising[J]. Chinese Journal of Lasers, 2020, 47(6): 0611001.
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