26 November 2007 A novel fibre-optic system for methane detection
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Abstract
A novel fibre-optic methane detection system was proposed, which involved sampled fibre grating and improved differential absorption detection technique. By this method, near-infrared equal-spaced multi absorption line of methane was detected simultaneously, and that gas weak absorption detection theory was developed. Using the comb shaped filter characteristic of sampled fibre grating, R2, R3 and R4 line of molecule absorption spectrum in 2ν 3 overtone band around 1.66μm was measured at one time. Two sampled fibre gratings of same type were used to fulfill the task of difference absorption detection. One sampled grating worked as measure grating with its reflection spectrum corresponding to the absorption line. The other grating worked as reference grating with its reflection spectrum deviate from that of measure grating to some extent. Chirped fibre grating with its central wavelength around R3 was adopted as optical band-pass filter. The light power of the three absorption line and the three reference wavelength was detected alternately by PIN PD at the same time. So that difference absorption detection was achieved. The effect of light source instability was avoided by ratio treatment. The validity of the system was verified by experiments.
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Xijun Wu, Yutian Wang, Leilei Chen, Xinyan Huang, "A novel fibre-optic system for methane detection", Proc. SPIE 6830, Advanced Sensor Systems and Applications III, 68301B (26 November 2007); doi: 10.1117/12.756001; https://doi.org/10.1117/12.756001
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