Leakage-Waveguide-Type Plastic Optical Fiber Humidity Sensor Using Dye-Doped Swellable Polymers as Cladding

Abstract

We fabricated Plastic Optical Fiber (POF) humidity sensors using a humidity-swelling polymer as the cladding. This sensor changes from the leakage to waveguide mode at a certain humidity. The purpose of this study is to develop a POF humidity sensor that can measure low humidity using the leakage mode. In the leakage mode, the core is susceptible to bending and distortion, and an ideally straight core is required to obtain the transmitted light intensity changes that can be used for measurements. Therefore, to enable measurements in the leakage mode, we fabricated a sensor using a core with the POF distortion removed by heating and stretching and a dye-doped polyvinylpyrrolidone (PVP) : PolyVinylidene DiFluoride (PVDF) mixture solution as the cladding. From the experimental results, we note that the developed POF humidity sensor has high sensitivity and can be used for measurements at 0% relative humidity.