Simultaneous measurement of refractive index and temperature using an epoxy resin-based interferometer

A fiber-optics reflection probe based on fiber Fabry-Perot interference (FFPI) is proposed and experimentally demonstrated. The sensing structure comprises an epoxy resin (ER)-based cap on the end-face of the single-mode fiber. A well-defined interference spectrum is obtained by the reflective beams of two surfaces of the ER cap. The simultaneous measurements, including fringe contrast-referenced for the surrounding refractive index (SRI) and wavelength-referenced for temperature, have been achieved via selective interference dips monitoring. Experimental results indicate that the proposed FFPI presents an SRI sensitivity of 57.69 dB/RIU in the measurement range of 1.33-1.40 RIU and a temperature sensitivity of 0.98  pm·μm^-1·°C^-1 with per unit cavity length in the range of 30°C-70°C. The proposed sensor has advantages of being compact and robust, making it an alternative candidate as a smart sensor in chemical and biological applications.