Sensitivity and Accuracy Enhanced Wavelength Modulation Spectroscopy Based on PSD Analysis

This letter proposes a novel method to implement calibration-free wavelength modulation spectroscopy (CF-WMS) with enhanced sensing sensitivity and accuracy. Compared with traditional 1f-normalized CF-WMS implementation, the proposed method is derived, for the first time, from the power spectral density (PSD) spectrum of transmitted laser. This novel derivation enables estimation of noise power, thus enhancing of sensing sensitivity and retrieval accuracy of gas parameters, particularly in noisy environment. The proposed method is validated by both numerical simulation and condition-controlled experiment, indicating improvement of the detection limit of gas parameters by a factor of 2.64 compared to the traditional method.