Frequency response of distributed fiber-optic vibration sensor based on nonbalanced Mach-Zehnder interferometer

We set up the analytical model for the frequency response of a distributed fiber-optic vibration sensor based on the nonbalanced Mach-Zehnder interferometer, the frequency response of which is related to both of the length difference of the delay fibers and the location of the vibration. In addition, a series of null frequencies, in which the vibration cannot be detected, is also found. The distributed fiber-optic vibration sensor with the delay fiber of 25 km and the sensing fiber of 10 km is built experimentally. Two null frequencies of 8013 Hz and 5011 Hz, which are induced from the delay fibers and the location of vibration respectively, are obtained. The results can serve as an important guidance for designing the sensor.

► We model the frequency response of a fiber-optic vibration sensor.
► Null frequency of the sensor is related to vibration location.
► Null frequency of the sensor is related to the length of the delay fibers.
► The model is verified by the experiment.