LAUSR

Abstract For the problems of light source fluctuation noises, zero drift and other problems of H 2 S gas concentration sensor in optic-fiber evanescent-wave absorption spectroscopy, double-light-path absorption system was designed to theoretically analyze the relationship between evanescent-wave power and gas concentration as well as detection sensitivity. Moreover, the relationship between evanescent-wave power and optical-fiber residual diameter in the optic fiber corrosion process was also studied. The sensing probes with different evanescent-wave power ratios were used to detect experiments of H2S gas concentration. The experimental results show that the sensitivity is up to 0.169 μw/ppm when the evanescent-wave power ratio of sensing probe is 10%, detected minimum H 2 S gas concentration is 5.1 ppm, the detection repeatability is good and the response time is only 2.03s. Due to low production cost, high sensitivity and short response time, the optic-fiber evanescent-wave sensor can be used for real-time on-line measurement of H 2 S gas in the area of the hydrocarbon exploration and development.