An anti-noise composite optical fiber vibration sensing System

Abstract In order to eliminate strong ambient noise affecting the detection performance of optical fiber vibration sensing system, a composite system is proposed in this paper, which merges Michelson interferometer (MI) structure, Mach-Zehnder interferometer (MZI) structure and phase-sensitive optical time domain reflector (Φ-OTDR) structure by optical path coupling and wavelength division multiplexing. The MI structure is used to detect remote vibration signal, the MZI structure is used to detect the information of local ambient noise at the sensing fiber entrance, and the Φ-OTDR is used to locate vibration position. Experimental results show that the composite system can filter out frequency components of the ambient noise, restore and locate the vibration signal up to 20 kHz with single frequency noise of 1 kHz. Moreover, the vibration signal of 5 kHz could be located and restored at the length of about 4 km with the local ambient disturbance of percussion noise.