Laser & Optoelectronics Progress, Volume. 58, Issue 7, 0730001(2021)
Denoising of Digital Filtering Based on Wavelength Modulation Spectroscopy
Due to its lower concentration limit, wavelength modulation spectroscopy has been widely used for gas concentration detection based on laser absorption spectroscopy. Various background noises and optical fringes can decrease the accuracy of concentration measurement and increase the lower limit of concentration measurement. To reduce the background noise and improve the signal-to-noise ratio of the measurement system, the absorption spectral lines at 2.25 μm were used to measure the NH3 concentration in the experiment and theoretically analyze. In signal processing, wavelet and Gabor transform techniques were used to reduce the noise in harmonic signal. The results show that Gabor and wavelet transforms can effectively remove the influence of various noises while preserving the integrity of the harmonic signal with the optimal control parameters. Wavelet transform has better denoising ability than the Gabor transform for harmonic signals mainly containing white noise and optical fringes, and can improve the signal-to-noise ratio and the smoothness of the signal curve. The lower limit of NH3 concentration after denoising is reduced from 0.36 mg/m3 to 34.45×10-3 mg/m3.
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Lifang Zhang, Fei Wang, Hao Wei, Jing Wang, Haibin Cui, Guanjia Zhao. Denoising of Digital Filtering Based on Wavelength Modulation Spectroscopy[J]. Laser & Optoelectronics Progress, 2021, 58(7): 0730001
Category: Spectroscopy
Received: Oct. 9, 2020
Accepted: Nov. 18, 2020
Published Online: Apr. 25, 2021
The Author Email: Zhang Lifang (21227023@zju.edu.cn)