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Optimization of the optical path of the methane telemetry system based on TDLAS technology

Spectroscopic measurement of methane gas concentrations using absorption lines in the near infra-red (the 1.67 μm region) has been demonstrated by several research teams. In this paper, a methane telemetry system based on tunable diode laser absorption spectroscopy (TDLAS) is proposed and demonstrated. The center wavelength of the laser is locked to the methane absorption peak and the second harmonic detection technology is used to realize the real time monitoring of the methane gas concentration. To receive more signal light and enhance the signal to noise ratio, a lens and its focal length, the spot size of the reflecting surface and a filter plate are used to optimizing the optical path. The experimental results show that after optimizing methane telemetry system the minimum detection limit can be enhance from 20000 ppm to 5000 ppm in the distance of 20 meters.