Optical fiber humidity sensor based on a hollow core fiber filled with BPQDs-PVA

An optical fiber Fabry–Perot (FP) interferometric humidity sensor based on black phosphorus quantum dots (BPQDs) and polyvinyl alcohol (PVA) is proposed for the first time, to the best of our knowledge, and experimentally verified. The sensor is constructed by splicing a brief hollow core fiber (HCF) with a single-mode fiber (SMF) and filling the BPQDs-PVA compound into the HCF. When the proposed humidity sensor is placed in a humidity environment, BPQDs-PVA adsorbs water molecules in the air with increasing humidity, which changes the length of the FP cavity, as well as the refractive index of BPQDs-PVA, resulting in a spectral blueshift. The influence of the mixing ratio on humidity response properties has been experimentally investigated. A linear enhanced sensitivity of − 0.7525 n m / % R H within the humidity range of 45-75 %RH has been achieved. The maximum instability is 0.07 %RH in a long-term stability test, whereas the response and recovery times are 1.44 and 1.48 s, respectively.