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Near-infrared fiber optics gas sensor for remote sensing of CH4 gas in coal mines

In this paper, a particular equipment, one-channel optical-fiber-based methane gas real-time monitoring system, will be demonstrated. The system is designed especially for the mining complexes and residential area. A long-distance silica fiber link with a self-design optical gas sensor head have been employed in conjunction with a wavelength-tunable InGaAsP DFB laser diode at 1.64μm (around R(6) absorption peak of methane)1 to realize highly sensitive remote interrogation of CH4. By wavelength modulation with the DFB laser diode and a self-design processing circuit, sensitivities of less than 0.1 % (volume) have been achieved with the response time of less than 5 seconds.