Multi-point multi-component gas sensing by frequency-modulated continuous-wave interferometry

Accurate detection and quantification of gas mixtures are essential in various fields, but distinguishing multi-component gases in multi-point measurement scenarios faces substantial challenges. Here, we propose a multi-point multi-component gas sensing method based on frequency-modulated continuous-wave interferometry that can simultaneously achieve high spatial resolution for multi-point localization and high spectral resolution for multi-component gas analysis. As proof of concept, the method is experimentally demonstrated by four gas sensing nodes (including three single-pass gas cells and one multi-pass gas cell) to measure gas mixtures containing C₂H₂, C₂H₄, and CH₄. It simultaneously achieves cm-level sensing spatial resolution and sub-GHz spectral resolution. Using single-pass gas cells, the achieved sensitivities for C₂H₂, C₂H₄, and CH₄ are 0.63 ppm, 4.9 ppm, and 2.6 ppm, respectively; using the multi-pass gas cell, the sensitivities are improved to 8.6 ppb, 31 ppb, and 26 ppb, respectively. Possessing high spatial resolution, high spectral resolution and high sensitivity, the proposed method provides a powerful solution for analyzing gas mixtures placed in different locations.