Optical fringes removal in TDLAS based on wavelet denoising

Abstract

Abstract: 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 limit of 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.

Key words: tunable diode laser absorption spectroscopy, signal processing, wavelet denoising

CLC Number:

FENG Shiling, CUI Qi, GUO Xinqian, QIU Xuanbing, GUO Guqing, HE Xiaohu, LI Chuanliang∗. Optical fringes removal in TDLAS based on wavelet denoising[J]. Journal of Atmospheric and Environmental Optics, 2022, 17(3): 328-335.

References 19

[1]	Du Z H, Zhai Y Q, Li J Y, et al. Techniques of on-line monitoring volatile organic compounds in ambient air with optical
	spectroscopy [J]. Spectroscopy and Spectral Analysis, 2009, 29(12): 3199-3203.
	杜振辉, 翟雅琼, 李金义, 等. 空气中挥发性有机物的光谱学在线监测技术 [J]. 光谱学与光谱分析, 2009, 29(12):
31	99-3203.
[2]	Zhang Z R, Dong F Z, Wu B, et al. In-situ 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]	Kan R F, Liu W Q, Zhang Y J, et al. Absorption measurements of ambient methane with tunable diode laser [J]. Acta Physica
	Sinica, 2005, 54(4): 1927-1930.
	阚瑞峰, 刘文清, 张玉钧, 等. 可调谐二极管激光吸收光谱法测量环境空气中的甲烷含量 [J]. 物理学报, 2005, 54(4):
19	27-1930.
[4]	Werle P. Accuracy and precision of laser spectrometers for trace gas sensing in the presence of optical fringes and atmospheric
	turbulence [J]. Applied Physics B, 2011, 102(2): 313-329.
[5]	Reid J, El-Sherbiny M, Garside B K, et al. Sensitivity limits of a tunable diode laser spectrometer, with application to the
	detection of NO2 at the 100-ppt level [J]. Applied Optics, 1980, 19(19): 3349-3353.
[6]	Webster C R. Brewster-plate spoiler: A novel method for reducing the amplitude of interference fringes that limit tunable-laser
	absorption sensitivities [J]. Journal of the Optical Society of America B, 1985, 2(9): 1464-1470.
[7]	Wu S Q, Kimishima T, Kuze H, et al. Efficient reduction of fringe noise in trace gas detection with diode laser multipass
	absorption spectroscopy [J]. Japanese Journal of Applied Physics, 2000, 39 (Part 1, No. 7A): 4034-4040.
[8]	Riris H, Carlisle C B, Warren R E, et al. Signal-to-noise ratio enhancement in frequency-modulation spectrometers by digital
	signal processing [J]. Optics Letters, 1994, 19(2): 144-146.
[9]	Guo X Q, Qiu X B, Ji W H, et al. Minimization of interference fringes in tunable diode laser absorption spectrum based on
	empirical mode decomposition [J]. Laser & Optoelectronics Progress, 2018, 55(11): 463-469.
	郭心骞, 邱选兵, 季文海, 等. 基于经验模态分解的可调谐半导体激光吸收光谱中干涉条纹的抑制 [J]. 激光与光电子学
	进展, 2018, 55(11): 463-469.
[10]	Tian G, Li J S. Tunable diode laser spectrometry signal de-noising using discrete wavelet transform for molecular spectroscopy
	study [J]. Optica Applicata, 2013, 43(4): 803-815.
[11]	Li H J. Near-Infrared Diode Laser Absorption Spectroscopy with Applications to Reactive Systems and Combustion Control
[D]	California: Stanford University, 2007.
[12]	Mappe-Fogaaing I, Joly L, Durry G, et al. Wavelet denoising for infrared laser spectroscopy and gas detection [J]. Applied
	Spectroscopy, 2012, 66(6): 700-710.
[13]	Zheng C T, Ye W L, Huang J Q, et al. Performance improvement of a near-infrared CH4 detection device using waveletdenoising-assisted wavelength modulation technique [J]. Sensors and Actuators B: Chemical, 2014, 190: 249-258.
[14]	Wang Z L, Chang J, Zhang S S, et al. An improved denoising method in RDTS based on wavelet transform modulus maxima
[J]	IEEE Sensors Journal, 2015, 15(2): 1061-1067.
[15]	Xu Y, Weaver J B, Healy D M, et al. Wavelet transform domain filters: A spatially selective noise filtration technique [J]. IEEE
	Transactions on Image Processing: A Publication of the IEEE Signal Processing Society, 1994, 3(6): 747-758.
[16]	Donoho D L. De-noising by soft-thresholding [J]. IEEE Transactions on Information Theory, 1995, 41(3): 613-627.
[17]	Rothman L S, Gordon I E, Babikov Y, et al. The HITRAN2012 molecular spectroscopic database [J]. Journal of Quantitative
	Spectroscopy and Radiative Transfer, 2013, 130: 4-50.
[18]	Nielsen M. On the construction and frequency localization of finite orthogonal quadrature filters [J]. Journal of Approximation
	Theory, 2001, 108(1): 36-52.
[19]	Qiu H, Lee J, Lin J, et al. Wavelet filter-based weak signature detection method and its application on rolling element bearing
	prognostics [J]. Journal of Sound and Vibration, 2006, 289(4-5): 1066-1090.