Performance analysis of humidity high-sensitivity tapered optical fiber sensor

A 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 SiO2 nanoparticles. When the tapered section has no extension, the d-PMMA fiber with agarose coating presents the highest average sensitivity of 533.46 pm/%RH in the 0% to 60% RH range. Furthermore, variations in the structure's dimensions are investigated, demonstrating that we can tune the sensitivity based on the taper extension length and radius. An extension of the tapered section up to 4000 mu m gives an improvement in the average sensitivity to 1,214.9 pm/%RH. Moreover, a reduction of the tapered radius from 15 to 1.5 mu m gives a rise in the sensitivity to 1,575.7 pm/%RH.

Automated summary

A high-sensitivity relative humidity optical fiber sensor based on an intermodal interference structure is proposed, with a tapered no-core fiber coated with an RH-sensitive material. Investigating various coating materials and dimensions, it is found that the sensitivity of the sensor can be tuned by adjusting the parameters.