Self-correlation algorithm in optical frequency domain for cavity length interrogation of fiber-optic Fabry–Perot sensors

Abstract

A novel self-correlation algorithm is proposed to obtain accurately the cavity lengths of fiber-optic Fabry–Perot (FP) sensors from their white-light reflection spectrum. The reflection spectrum was first transformed into an optical frequency domain, which was then continuously translated with different frequency values and self-correlated with the untranslated values to obtain the self-correlation function of the translation frequency. The cavity length could be determined with high resolution by determining its period using the golden section method. The feasibility and performances of the proposed method were verified by both simulation and experiment. A high resolution of 14 nm could be obtained for a fiber-optic air-gap FP sensor with a cavity length of 200.888 μm.