Plastic optical fiber sensor for temperature-independent high-sensitivity detection of humidity

A simple U-shaped plastic optical fiber evanescent-wave sensor was fabricated for temperature-independent highly sensitive detection of humidity. The sensing region of the sensor was subjected to five cycles of heating–cooling to improve temperature independence. The effects of the polyimide (PI) coating thickness, number of graphene oxide (GO) coating layers, and alternate PI–GO coating sequence were investigated to optimize sensitivity. The fabricated sensor exhibited high-temperature independence and good sensitivity of 0.17 × 10 − 2 (% relative h u m i d i t y ) − 1 in the temperature range of 10°C to 70°C.