Intensity-modulated refractive index sensor based on the side modes of fiber Bragg grating

Abstract

An intensity-modulated side mode-based fiber Bragg grating (FBG) refractive index (RI) sensor is demonstrated. The feasibility is based on Fresnel reflection from the end-face of fiber-tip. Theoretically, the forming of asymmetrical irregular side mode fringes is firstly explained and simulated, the feasibility of this sensor for RI measurement is proved. As a result, the proposed intensity-modulated side mode-based FBG RI sensor exhibits a high sensitivity of −590.625 dB/RIU at the RI of 1.466, which is the highest RI sensitivity among the previous reported fiber-tip based RI sensors. The intensity fluctuations of this sensor are less than 0.824 dB. Moreover, remote RI monitoring using this sensor is studied. As a result, maximum RI sensitivity of the remote sensing system is −134.174 dB/RIU at the RI of 1.466, with the intensity fluctuations less than 0.201 dB.