Temperature And Humidity Sensor Based On A Double D-Shaped Optical Fiber With Incorporated Toluene And Polyethylene

A double D-shaped optical fiber for simultaneous temperature and relative humidity (RH) sensing is described. The flat surfaces of the D-shaped optical fiber are coated with toluene as a thermally sensitive material and polyethylene as a humidity-sensitive material. Using the finite element method, the effects of the metal film thickness and polished depth of the D-shaped optical fiber on the sensing performance were analyzed and the optimal structural parameters were obtained. The temperature and humidity sensing properties were studied and show that temperature and humidity sensitivities of 1.02 nm/degrees C and 0.79 nm/% RH were obtained from 25 degrees C to 65 degrees C and 30% RH and 70% RH with maximum linearities of 0.996 and 0.997. The proposed optical fiber sensor demonstrates potential applications for dual-parameter detection.