Relative humidity sensor based on Vernier effect with GQDs-PVA un-fully filled in hollow core fiber

A new relative humidity (RH) sensor based on two cascaded Fabry-Perot interferometers (FPIs) and Vernier effect is proposed and developed. The two cascade FPIs are constructed by splicing a section of photonic crystal fiber (PCF) between a section of single mode fiber and a section of hollow core fiber (HCF), where the length of PCF is 281.43 mu m and the length of HCF is 490.83 mu m. The hollow core fiber is un-fully filled with Graphene quantum dots and polyvinyl alcohol. By adjusting the filling time, FPIs with different free spectral ranges are got. We study the three sensors whose filling time are 5 min, 10 min and 15 min, respectively. Among them, the FPI with 15mins' filling has the highest sensitivity, which is 0.456 nm/%RH with RH changing from 19.63%RH to 78.86%RH. In addition, the experimental results indicate it has good reversibility and stability. What's more, the sensitivity is about 4.8 times higher than that of our previous work. In brief, the compact configuration, easy fabrication, high sensitivity and good RH resolution imply the proposed sensor has good potential for RH measurement application. (C) 2018 Elsevier B.V. All rights reserved.