Multi-gases Optical Fiber Sensing System.

摘要

Absorption of light radiation in the near-infrared spectra is widely used to detect the existence and the concentration of gaseous specimen for its simplicity and insensitivity to the environmental conditions of the absorbing species. Optical fiber gas sensors based on absorption of light by the vibrational-rotational energy levels of gas molecules at near-infrared (1--1.8microm) have attracted considerable attention recently. The advantages of fiber sensor are remote capability, safety in hazardous environments, immunity to electromagnetic fields, and etc. The possible gases that can be detected are methane, acetylene, hydrogen sulphide, carbon dioxide, carbon monoxide, and etc.;In this dissertation, a particular optical fiber based multi gas real time monitoring system which can be deployed in mining complexes has been demonstrated. The system can detect methane and carbon monoxide. A customize designed double pass gas cell and a multi pass White cell have been demonstrated to detect methane and carbon monoxide, respectively. By wavelength modulation with the DFB laser, EDFA light source with tunable filter, a self-designed processing circuit, and data processing software, the system reaches sensitivity 138ppm for methane and 290ppm for carbon monoxide. The response time of the system is less than 6 seconds. Extensive tests have been carried out and comparisons made with existing conventional gas detection systems, it is shown that the performance of the optical fiber sensor system is generally better than conventional system.