An optical fiber relative humidity sensor based on hollow-core fiber and hydroxypropyl methylcellulose hydrogel film

Abstract Hydroxypropyl methylcellulose (HPMC) is a kind of water-soluble polymer material. The hydrogel formed by HPMC swelling in water is a polymer network system with a netlike cross-linked structure and it can absorb lots of water if it exposed to the water environment. Therefore, an optical fiber Fabry-Perot interferometer (FPI) relative humidity (RH) sensor based on hollow-core fiber (HCF) and HPMC hydrogel film is proposed and demonstrated. The experimental results show that the proposed sensor has a binomial humidity response and 2.25 s response time in the range of 40%-99%RH. The HPMC hydrogel with hydrophilicity, natural grid-like nanostructure and biocompatibility is an effective humidity-sensitive material for optical fiber RH sensor and has great application potential in various fields.