Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer

A novel and compact temperature and relative humidity (RH) simultaneously measurement sensor based on compact Mach-Zehnder interferometer (MZI) and Fabry-Perot interferometer (FPI) is proposed and experimental implemented. The sensing structure is made by splicing a 200 μm single mode fiber (SMF) between two 10 cm SMFs with large core-offset. The core-offset distance is 62.8 μm coated with RH sensitive material graphene quantum dots and polyvinyl alcohol (GQDs-PVA). The transmitted structure acts as MZI, and the reflected structure acts as FPI, then the simultaneous detection of temperature and RH can be achieved by monitoring the spectrums of FPI and MZI, respectively. The sensitivity to RH is −0.132 nm/%RH with resolution of 0.15 %RH, and the sensitivity to temperature is 0.37 nm/°C with the resolution of 0.05 °C. The proposed sensor is compact, high sensitivity, simple making and low cost.