Simultaneous Measurement of External Refractive Index and Temperature by Using a Side-polished Fiber Bragg Grating with a Polymer Overlay

Abstract

A hybrid grating sensing device based on a side-polished fiber Bragg grating (FBG) with a polymer overlay is proposed for simultaneous measurement of external refractive index and temperature. The side-polished FBG, which is insensitive to ambient index change, is utilized for detecting temperature variation, and the polymer overlay is coated on the side-polished FBG for measurement of ambient index change. The temperature sensitivities of the side-polished FBG and the polymer overlay were measured to be 0.01 nm/℃ and-0.58 nm/℃, respectively, in a temperature range from 30℃ to 100℃. The ambient index sensitivities of the polymer overlay were measured to be 498.8 nm/RIU in an ambient index range from 1.33 to 1.