Ultrasonic Vibration Sensing of Intrinsic Fabry-Perot Interferometer Sensor Array Based on Local Spectral Analysis

This paper presents a low-cost integrated intrinsic Fabry-Perot interferometer (IFPI) sensor array demodulation algorithm based on local spectral analysis, which exploits multiple local spectra instead of the entire spectrum to achieve ultrasonic vibration measurement well beyond the sweeping period of the tunable laser source. By balancing the demodulation range and the demodulation resolution of IFPIs, this paper divides the entire spectrum produced by a distributed feedback (DFB) laser into 152 local spectra by a sliding window for IFPIs demodulation respectively, thereby implementing up to 160 kHz vibration measurement. To reduce the load on the data acquisition system and simplifies the interrogation system, this paper adopts a nonlinear tuning error compensation method based on an in-line IFPI sensor. In addition, chirp Z-transform is used in this paper to replace the traditional zero-padding-based fast Fourier transform to achieve the local fineness of demodulated optical path difference (OPD) spectrum, so as to reduce the waste of computation caused by zero-padding.