Performance analysis of humidity high-sensitivity tapered optical fiber sensor

• Published in: Optical and quantum electronics 2022-09, Vol.54 (9), Article 537
• Main Authors: de Carvalho, Pedro Vitor Taranto, Martinez, Maria Aparecida Gonçalves, Giraldi, Maria Thereza Rocco
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Coating; Computer Communication Networks; Electrical Engineering; Humidity; Intermodal; Lasers; Nanoparticles; Optical Devices; Optical fibers; Optics; Parameter sensitivity; Photonics; Physics; Physics and Astronomy; Polymethyl methacrylate; Protective coatings; Refractivity; Relative humidity; Sensitivity enhancement; Sensors; Silicon dioxide
• ISSN: 0306-8919; 1572-817X
• DOI: 10.1007/s11082-022-03952-w

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 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/%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 μ 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 μ m gives a rise in the sensitivity to 1,575.7 pm/%RH.