A sandwich fiber sensor for simultaneous measurement of RI and temperature

A simple and compact all-fiber sensor based on a sandwich fiber structure for simultaneous measurement of refractive index and temperature is proposed and demonstrated. The sensing element was made by cascading two core-offset attenuators with a fiber Bragg grating (FBG) in between. The two core-offset attenuators make up a Mach-Zehnder interferometer. The transmission spectrum would shift with the variation of the ambient refractive index (RI) and/or temperature. The experimental results show that the RI sensitivity and the temperature sensitivity for the sensor are 35.9611 nm/RIU (refractive index unit) and 0.0501 nm/°C, respectively.