Methane Optic Fiber Sensor Network Based on Infrared Spectrum Absorption in Coal Mine
WU Xiao-jun1，3,WANG Peng2*, WANG Zhi-bin1, 2, LI Xiao1, 2, TIAN Er-ming1, 2
1. Key Laboratory of Instrumentation Science & Dynamic Measurement (North University of China) Ministry of Education, North University of China, Taiyuan 030051, China 2. Engineering Technology Research Center of Shanxi Province for Optoelectronic Information and Instrument, North University of China, Taiyuan 030051, China 3. College of Mechanical and Electrical Engineering, North Uiversity of China, Taiyuan 030051, China
Abstract：Through analyzing the infrared absorption spectrum of methane, a multi-point optic fiber sensor network was designed based on the principle of light absorbing capability of gas which varies with gas concentration at its characteristic wavelength. A distributed feedback laser diode (DFB LD) was used as the light source and an InGaAs PIN as the photodetector which features high sensitivity and low noise. Sixteen methane sensors were multiplexed in this system with space division multiple access technology (SDMAT), and the faint signals were processed by the filtering and amplifying circuit. All signals were gathered by the PCI data acquisition card, and finally, the signals were analyzed by the fast Fourier transform with software. The results showed that the sensitivity of every sensor reached 200 ppm(μg·mL-1), long-time accuracy and stability of all sensors could meet the practical demands, the response time of each sensor was less than 2 seconds and the detecting period was less than 32 seconds. By theoretical analysis, all sensors could be put in the mine at least 20 km from the ground, and the instruments could be applied to multi-point measurement at real-time in multiple occasions.
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