Optical fiber distributed vibration sensor based on dual Mach-Zehnder interferometer using an improved phase generated carrier algorithm

Abstract

Optical fiber distributed vibration sensor based on dual Mach-Zehnder interferometer (DMZI) has been extensively studied for vibration detections. Whereas the accurate signal demodulation technique is still a challenging task for some particular detections, especially for those dynamic vibration sensing with high frequency. In this work, we propose an ameliorated phase generated carrier (PGC) demodulation algorithm for the dynamic vibration sensing in the DMZI based vibration sensing system. A piezoelectric stretcher is firstly cascaded with the reference arm of the DMZI structure. Then a dynamic strain would be produced to change the phase difference of the DMZI structure when the carrier signal and the measured vibration signal are applied on the stretcher and the sensing arm of the DMZI, respectively. Finally, the applied vibration signal can be accurately demodulated by using the improved PGC demodulation algorithm. Theoretical analysis and derivation of the proposed vibration sensing approach are given in detail. Simulation analysis and vibration experiments with different vibration patterns have been implemented to demonstrate the effectiveness of the proposed sensing approach. Experimental results show that the relation between the applied signal and the demodulated signal is approximately linear. Moreover, the high-order harmonic effect and the intensity fluctuation of the demodulated signals have been effectively suppressed in the proposed DMZI based vibration sensing system.