Fig. 1. Absorption peaks of CO₂, C₂H₂, CH₄, and H₂O. (a) At 6330.82 cm^-1; (b) at 6534.36 cm^-1; (c) at 6046.95 cm^-1; (d) at 7181.15 cm^-1

Fig. 2. Structure diagram of multi-component gas detection system based on F-TDM technology

Fig. 3. Modulation and demodulation diagram of multi-component gas detection system based on F-TDM technology

Fig. 4. Experimental results of CO₂ and C₂H₂ in FDM detection. (a) Scanning signals of CO₂ and C₂H₂ and detector signals; (b) 2f measurement signals of CO₂ and C₂H₂

Fig. 5. Experimental results of CH₄ and H₂O in FDM detection. (a) Scanning signals of CH₄ and H₂O and detector signals; (b) 2f measurement signals of CH₄ and H₂O

Fig. 6. Signal variations of continuous measurements of CO₂ and C₂H₂ in the FDM detection

Fig. 7. Signal variations of continuous measurements of CH₄ and H₂O in the FDM detection

Fig. 8. R-channel signals for CO₂ and CH₄ in the TDM detection and the scanning signals

Fig. 9. R-channel signals for H₂O and C₂H₂ in the TDM detection and the scanning signals

Fig. 10. Signal variations of continuous measurements of CO₂ and CH₄ in the FDM detection

Fig. 11. Signal variations of continuous measurements of H₂O and C₂H₂ in the FDM detection

Fig. 12. R-channel measurement signals of CO₂, C₂H₂, CH₄, and H₂O by F-TDM and their fitting results. (a) CO₂ signal; (b) C₂H₂ signal; (c) CH₄ signal; (d) H₂O signal

Fig. 13. Experimental results of continuous measurements of CO₂, C₂H₂, CH₄, and H₂O by F-TDM