[Application in methane extraction of fiber methane monitoring system based on spectral absorption]

An optical fiber distributed multi-point methane real-time monitoring system based on the methane spectral absorption characteristic is researched, and it's application in methane extraction is presented. An 1665 nm distributed feedback (DFB) laser is used as the light source by taking the triangular signal to modulate the light frequency of the DFB laser. Using the combination of single-chip computer C8051F410, A/D transform circuit, communication circuit, display circuit, etc, the concentration of methane can be monitored and displayed on the screen. And the function of sounding the alarm bell and communication are achieved. The laser wavelength shift is carried out with adaptive adjustment by the built-in gas calibration pond so as to realize the locking of a methane absorption line. Several field tests have been founded at home and abroad. The results show that the system has good performance in stability and sensitivity. The distributed multi-point methane concentration monitoring is realized in the range of 0%-100%. A sensitivity of ppm order of magnitude has been achieved. It possesses of wide application in methane extraction.