High sensitivity refractive index sensor based on optical fiber ultra-weak Fabry-Perot interferometer

Abstract

We propose and demonstrate a novel refractive index (RI) sensor based on an ultra-weak intrinsic fiber Fabry-Perot interferometer (FPI), which is simply fabricated by splicing a tiny section of thin-core fiber (TCF) to a standard single-mode fiber (SMF). The fusion interface (SMF/TCF) and the well cleaved TCF end face form a low fringe contrast FPI in the air. It exhibits an average RI sensitivity of 240dB/RIU over a wide RI range of 1.3326-1.4305, with a maximum sensitivity of 1110.7dB/RIU at the RI of 1.4305.