Fiber optics for atmospheric mine monitoring

The authors describe work done to address methane, carbon monoxide, and distributed temperature monitoring. A review is made of the potential and problems of using fiber optics (FOs) for mine monitoring systems. Methane detection is based on differential absorption of infrared light. A methane monitor that can detect concentrations as low as 0.2% as far away as 2 km via FO cable is described. A carbon monoxide monitoring system that combines a low-powered electrochemical cell with fiber optic (FO) telemetry is described. Testing has shown that the system can operate maintenance free for several months. A distributed FO temperature-monitoring system is being investigated for possible application in mine fire detection. Performance of this system at the US Bureau of Mines' Lake Lynn Laboratory is reported. The sensor employs optical time domain reflectometry techniques that allow the entire length of fiber (up to 2 km) to function as a distributed temperature sensor. Distributed temperature sensors have considerable potential for monitoring areas such as conveyor beltways.< >