Modulated pulses based distributed vibration sensing with high frequency response and spatial resolution.

A distributed optical fiber sensing system merged Mach-Zehnder interferometer and phase sensitive optical time domain reflectometer (φ-OTDR) system for vibration measurement with high-frequency response and high spatial resolution is demonstrated, where modulated pulses are proposed to be used as sensing source. Frequency response and location information are obtained by Mach-Zehnder interferometer and φ-OTDR technology, respectively. In order to simulate high-frequency vibration of crack of cable and civil structure, experiments on detection of piezoelectric transducer and pencil-break are carried out. Spatial resolution of 5 m and the maximum frequency response of ~3 MHz are achieved in 1064 m fiber link when the narrow pulse width is 50 ns.