Low Loss Polycarbonate Polymer Optical Fiber for High Temperature FBG Humidity Sensing

We report the fabrication and characterization of a polycarbonate (PC) microstructured polymer optical fiber (mPOF) Bragg grating (FBG) humidity sensor that can operate beyond 100°C. The PC preform, from which the fiber was drawn, was produced using an improved casting approach to reduce the attenuation of the fiber. The fiber loss was found reduced by a factor of two compared to the latest reported PC mPOF [20], holding the low loss record in PC based fibers. PC mPOFBG was characterized to humidity and temperature, and a relative humidity (RH) sensitivity of 7.31± 0.13 pm/% RH in the range 10-90% RH at 100°C and a temperature sensitivity of 25.86±0.63 pm/°C in the range 20-100 °C at 90% RH were measured.