Review on Optical Fiber Sensors for Hazardous-Gas Monitoring in Mines and Tunnels

Gas monitoring in mines and tunnels is the key to ensuring safe production. Nowadays, optical fiber gas sensors depend on the advantages of nonelectrical signal transmission, antielectromagnetic interference, corrosion resistance, and small size, which has aroused the interest of researchers. In this direction, this article reviews optical fiber sensors for monitoring common hazardous gases (nitrogen dioxide, hydrogen sulfide, carbon monoxide, ammonia, sulfur dioxide, methane, hydrogen, and carbon dioxide) in mines and tunnels. The adaptability of optical fiber sensors and the characteristics of different optical sensing principles (interferometers, fiber Bragg grating, long-period fiber grating, surface plasmon resonance, and evanescent field) are first discussed. As foundations, the characteristics and sources of various gases, as well as the sensing principles of optical fiber gas sensors, are summarized. Then, the application of optical fiber sensors in hazardous-gas monitoring is discussed. Finally, the current challenges and future trends of optical fiber gas sensors are concluded.