| Summary: | A multi-gas sensing system was developed based on the detection principle of the non-dispersive infrared (NDIR) method, which used a broad-spectra light source, a tunable Fabry–Pérot (FP) filter detector, and a flexible low-loss infrared waveguide as an absorption cell. CH<sub>4</sub>, C<sub>2</sub>H<sub>6</sub>, and CO<sub>2</sub> gases were detected by the system. The concentration of CO<sub>2</sub> could be detected directly, and the concentrations of CH<sub>4</sub> and C<sub>2</sub>H<sub>6</sub> were detected using a PCA-BP neural network algorithm because of the interference of CH<sub>4</sub> and C<sub>2</sub>H<sub>6</sub>. The detection limits were achieved to be 2.59 ppm, 926 ppb, and 114 ppb for CH<sub>4</sub>, C<sub>2</sub>H<sub>6</sub>, and CO<sub>2</sub> with an averaging time of 429 s, 462 s, and 297 s, respectively. The root mean square error of prediction (RMSEP) of CH<sub>4</sub> and C<sub>2</sub>H<sub>6</sub> were 10.97 ppm and 2.00 ppm, respectively. The proposed system and method take full advantage of the multi-component gas measurement capability of the mid-infrared broadband source and achieve a compromise between performance and system cost.
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