Temperature-compensated refractive index sensor based on bent-fiber interference

In this letter, we present a hybrid single-mode fiber (SMF) structure for refractive index (RI) measurement with the temperature compensation capability. The interferometer has simple structure, consisting of a bare fiber semicircular bending region (SBR) and a fiber Bragg grating (FBG). The section of SBR serves as a refractometer with a temperature compensator using a simple FBG. The sensing mechanism of this device has been investigated and experimentally demonstrated. The FBG structure is insensitive towards the change in the ambient RI but is sensitive towards the changes in the ambient temperature whereas the SBR structure is sensitive towards both of RI and temperature. In the RI range of 1.3288-1.3730, the corresponding RI sensitivity for the bare fiber bending region is 160 nm/RIU (refractive index unit) and the RI resolution is about 8.5 × 10−5 RIU.