Fiber optic technology is progressing rapidly, including the development of fiber optic sensors for a wide variety of applications. These sensors have the advantage of high sensitivity, light weight, small size, high bandwidth, and freedom from electromagnetic influences. The U.S. Bureau of Mines is investigating the application of fiber optic technology to monitoring mine atmospheres. This paper describes work done to address methane, carbon monoxide, and distributed temperature monitoring. A review is made of the potential and problems of using fiber optics for mine monitoring systems. Methane detection is based on differential absorption of infrared light. A methane monitor is described that can detect concentrations as low as 0.2 pct as far away as 2 km via fiber optic cable. The upper range is 100 vol pct methane. Since the system requires no electrical power within the mine, it is intrinsically safe. A carbon monoxide monitoring system is described that combines a low-powered electrochemical cell with fiber optic telemetry. Testing has shown the system can operate maintenance-free for several months. Finally, a distributed fiber optic temperature-monitoring system is being investigated for possible application in mine fire detection. Performance of this system at the Bureau's Lake Lynn Laboratory is reported.