Performance analysis of humidity high-sensitivity tapered optical fiber sensor

high-sensitivity relative humidity optical fiber sensor based on an intermodal interference structure is proposed. In order to enhance the sensors’ sensitivity a tapered no-core fiber is coated with an RH-sensitive material. The material and geometrical parameters of the interferometric structure, as well as the refractive index of the coating material, have a strong influence on sensors’ response. Various coating materials for the pure silica and d-PMMA fibers are investigated, including agarose, porous silica, and SiO _2 nanoparticles. When the tapered section has no extension, the d-PMMA fiber with agarose coating presents the highest average sensitivity of 533.46 pm/