Detection of SF6 gas decomposition component H2S based on fiber-optic photoacoustic sensing

Abstract

A high-sensitivity fiber-optic Fabry-Perot (F-P) photoacoustic gas detection system with properties of anti-electromagnetic interference and intrinsically safe was presented for quantitative analysis of SF6 decomposition component H2S. Erbium-doped fiber amplification was combined with acoustic resonance amplification to enhance the photoacoustic signal. A fiber-optic cantilever acoustic sensor (FOCAS) was used to sense weak photoacoustic signals. To enhance the sensitivity and stability of photoacoustic signals detection, the effect of SF6 gas on the responses of FOCAS and photoacoustic cell (PAC) was investigated. When SF6 is the background gas, the resonance frequency of the PAC will be greatly reduced and the sensitivity of the FOCAS will be improved. With the excitation light power of 1 W and an averaging time was 200 s, the minimum detection limit (MDL) of H2S gas in the SF6 background reached 14 ppb, and the normalized noise equivalence absorption (NNEA) was calculated to be 3.14 × 10−9 cm−1·W·Hz−1/2. The combination of excitation enhancement and detection enhancement of the photoacoustic signal solves the problem that the traditional sensor is difficult to improve the detection sensitivity due to the low absorption coefficient of H2S gas in the near-infrared region.