Baseline-free wavelength modulation spectroscopy based on cepstral analysis

作者：Zhenhai Wang, Ning Hua Zhu, Weitian Wang, Xing Chao · 发表于：Optics Express · 年份：2025 · DOI：10.1364/oe.558143 · 被引用次数：4 · 研究领域：Spectroscopy and Laser Applications、Photonic Crystal and Fiber Optics、Advanced Fiber Laser Technologies

This paper demonstrates what we believe to be a new WMS m-FID technique based on cepstral analysis, incorporating wavelength modulation spectroscopy (WMS) with a modified form of the time-domain molecular free-induction decay (m-FID) signal. Detailed theoretical framework of the WMS m-FID technique, as well as the fitting routine, has been investigated. The proposed WMS m-FID technique is first validated through a static CO gas cell experiment using the CO R (9) absorption line near 2179.7719 cm −1 . The fitting error between the measured and best-fit m-FID signals is less than 1.0 %, with integrated absorbance area of relative uncertainty 0.17 %. Time-resolved measurements of CO over a 6-second purge period demonstrate the reliability and robustness of the proposed WMS m-FID approach in comparison with direct absorption spectroscopy (DAS) and WMS-2 f /1 f techniques. The demonstration of the proposed WMS m-FID approach is further carried out in a premixed CH 4 /Air laminar flame of a flat-flame burner. The relative fitting residuals between the measured and best-fit m-FID signals remain below 4.0 %, yielding T = 1763 K and X H 2 O =16.58 % at HAB = 7 mm, with a temperature uncertainty of 30 K and absolute H 2 O concentration uncertainty of 0.65 %. The average temperature difference between the WMS m-FID and WMS-2 f /1 f techniques is within 18.0 K (<1.0 % relative), and the H 2 O concentration difference is within 0.4 % (<2.6 % relative). Additionally, the proposed WMS...