Advanced Fiber-Optic Relative Humidity Sensor Based on Graphene Quantum Dots Doped Polyimide Coating

Novel fiber Bragg grating (FBG) relative humidity (RH) sensors based on polyimide (PI) doped with graphene quantum dots (GQDs) are proposed and experimentally demonstrated. The effects of GQDs doping on the sensor performance were investigated. The sensitivity of the humidity sensor could be increased by 96.36% when the doping mass fraction of GQDs was optimized at 0.2%. The FBG humidity sensor based on PI-doped GQDs exhibited good linearity at different operating temperatures in the RH range of 10–90%. Moreover, the excellent linearity of the temperature sensitivity facilitates the temperature compensation of these sensors. GQDs-doped PI is an excellent moisture-sensitive material that significantly improves the sensitivity of FBG humidity sensors, making it a promising candidate for humidity sensing in various applications.