New nodal real time gas concentration monitoring method and sensor

The new type nodal real-time gas densitymonitoring method and sensor has one near infrared DFB semiconductor laser and operates on the characteristic absorption of methane in the near infrared spectrum region. One monomode fiber power coupler is used in separating the laser beam into several beams led through fibers to fiber gas absorption cells in mine, and the laser beams through the absorbed gas are then led through fiber to the input optical switch. The selected signal through the calibrating cell is projected to the laser detector. By means of wavelength modulating technology and second harmonic detecting technology, the present invention realizes gas density measurement in high sensitivity, high resolution, no gas interference and fast response. Background light strength signal fitting method is adopted to eliminate the influence of light strength fluctuation on the measurement.