Wavelet-denoising technique detection based on tunable in near-infrared methane diode laser absorption spectroscopy

• Published in: 光电子快报：英文版 no. 4; pp. 299 - 303
• Main Author: 高宗丽 叶玮琳 郑传涛 王一丁
• Format: Journal Article
• Language: English
• Published: 2014
• Subjects: 分布反馈激光器; 半导体激光; 可调谐二极管激光吸收光谱; 基础; 小波消噪; 技术检测; 甲烷浓度; 近红外
• ISSN: 1673-1905; 1993-5013

A novel wavelet denoising （WD） assisted wavelength modulation technique is proposed for improving near-infrared de- tection performance on methane concentration based on tunable diode laser absorption spectroscopy （TDLAS）. Due to the ability of multi-level analytical resolutions both in time- and frequency-domains, the noise contained in the differen- tial signal is greatly suppressed. Sensor mechanical part, optical part and electrical part are integrated, and a portable detection device is finally developed. Theory and formulations of the WD-assisted wavelength modulation technique are presented, and experiments are carried out to prove the normal function on the extraction of the second harmonic （2j） signal from severely polluted differential signal by using the technique. By virtue of WD＇s suppression on noises, the sensing characteristics on CH4 concentration are improved, and the limit of detection （LOD） is decreased from 4× 10-6 （without WD processing） to 10-6. The proposed technique can also be used for the measurement on the concentration of other gases with corresponding near-infrared distributed feedback lasers.