Fig. 1. Absorption line strength of CH₄, CO₂ and H₂O at 1653.72 nm

Fig. 2. Structure of laser methane sensor probe

Fig. 3. Circuit structure block diagram

Fig. 4. Background noise of optical path

Fig. 5. Measurement results of methane sensor probe in full range

Fig. 6. Measurement results of 1.2% standard CH₄/N₂ mixture before and after temperature compensation

Fig. 7. Measurement results of 20% standard CH₄/N₂ mixture before and after temperature compensation

Fig. 8. Measurement results of 1000 ppm standard CH₄/N₂ mixture