All-Optical Remote Sensing Monitoring Technique of Methane Concentration Based on Tunable Diode Laser Absorption Spectroscopy

A novel all fiber optic sensing monitoring technique is researched for remotely detecting the concentration of methane gas. The triangular signal is used to modulate the light wavelength of the DFB laser. The narrow absorption line of the laser eliminates the cross sensitivity to moisture, ethane or other gases. With the use of the optical fiber links between monitor and sensor header, the system can provide remote and online monitor information. Since the sensor head is made without any active electrical components, it is intrinsically safe when used in the hazard environment such as coal mines. The results show that the monitoring technique has a great application in the methane extraction pipe-line, coal mines and the environment detection.