Quasi-distributed sensing network based on coherence multiplexing and spatial division multiplexing for coal mine security monitoring

A low-cost fiber Bragg grating(FBG) sensing system for coal-mine security monitoring is proposed in this paper.Based on the coherence multiplexing(CM) and spatial division multiplexing(SDM) techniques,this hybrid sensing network can support more than 40 sensors for quasi-distributed detection.It is demonstrated experimentally that the multiplexed sensing signal of each sensor can be clearly distinguished by an optical low-coherence reflectometry(OLCR).Methane concentration is detected with maximum sensitivities of an intensity variation of 10.92% and a concentration variation of 1%,using a well-designed sensor structure.Strain and temperature are also detected by this system,which also exhibits good results in the experiment.