Design and fabrication of humidity sensor based on the growth of micro/nano rods of ZnO on the tapered optical fiber

In this paper not expensive and sensitive humidity optical sensor was fabricated based on the growth of nano and micro rods of ZnO on the optical fiber through hydrothermal method. If fiber optic sensors that work based on evanescent waves covered with nanostructures would significantly enhance the sensitivity of sensros. Nano and micro rods of ZnO was formed densly and uniformly on the optical fiber. With exserting the humidity the refractive index around the fiber will change which leads to the variation of the external light intensity. Variations of light intensity which corresponds to the humidity concentration were recorded by spectrophotometer. Response time and recover time of sensor were measured and demonstrated that the ability of sensing humidity in acceptable level (10%-100%). Also the effect of two differet light source (laser He-Ne and white LED) on the sensitivity of sensors were investigated. The structure and morphology of ZnO nano rods were studied through XRD and SEM analysis.