Abstract: In view of problem of communication interruption due to power outages when gas explosions, water inrush and other disasters occurred in underground coal mines, an optical fiber sensing emergency communication system based on existing optical cables in underground coal mines was designed to realize collection, transmission and processing of sound information of trapped personnel in underground coal mines without electricity after mine disater. The system includes two parts: the optical fiber sound sensing subsystem and the hardware demodulation subsystem. The optical fiber sound sensing subsystem is constructed by adding optical fiber probes to the optical cables laid in underground roadway to monitor sound signals of the shouts and knocks of trapped people in the roadway. The hardware demodulation subsystem is placed on the ground to extract and restore the audio information loaded in the optical signal. The optical fiber sound sensing subsystem uses ASE broadband light source as the detection light, and solves measurement blind area problem through the delay fiber, and underground sound information collection is realized according to the relationship between the phase and light intensity changes of the detection light and the acoustic signal. The hardware demodulation subsystem adopts photoelectric conversion module and audio processing module to demodulate the collected sound signal, extract and amplify the weak signal. Experimental results show that within test distance of 10 km, the system can detect and extract sound signals with frequency range of 0.3 -3.4 kHz and 0 -5 m away from the fiber optic probe, with an accuracy of ±0.5 Hz.