Investigations on the Signal Recovery From the Non-Absorption Transmission Loss in Wavelength Modulation Spectroscopy

In practical applications, the signal-to-noise ratio (SNR), reliability, and the long-term stability of wavelength modulation spectroscopy (WMS) system is limited by the non-absorption transmission loss. In this investigation, we report on a signal recovery method to remove the impact of non-absorption transmission loss based on an automatic gain closed-loop control. The deviation of the WMS system with the introduced signal recovery method has been observed to be below 4.27% under the non-absorption transmission loss which varied from 0 dB to -6.02 dB, and is about 13 times lower than the ordinary system. The proposed method is suitable for promoting the reliability and stability of WMS system under rigorous circumstances. Besides, it has the potential value in the multi-point detection or to achieve a higher SNR.