Fabry-Perot cavity based on polymer FBG as refractive index sensor

The use of a polymer fiber as a refractive index sensor is proposed. A fiber Bragg grating is inscribed near the fiber tip and the fiber is cut shorter thus creating a Fabry-Perot cavity. The reflections between the fiber Bragg grating and the fiber end-face create a Fabry-Perot interferometer. The sensor was characterized to refractive index changes at constant temperature and to temperature at constant refractive index using a fast Fourier transform analysis of the interference signal. The sensor revealed a sensitivity of −1.94RIU−1 with a resolution of 1×10−3RIU and low sensitivity to temperature, with a cross sensitivity to temperature of 3.6×10−4RIU/°C.