Effect of dipping number of polyvinyl alcohol (PVA) -coated on optical Fiber for Humidity Sensor

Abstract Optical Fiber Humidity Sensors (OFHSs) have attracted significant research interest due to their several advantages including small size, high durability and can withstand the extreme environment regardless of high temperature, high pressure and high electromagnetic radiation. In this study, the proposed sensors were built from standard single-mode silica fibers working at telecommunication wavelengths and exhibited very good humidity sensing characteristics. Single-mode optical fibers were coated with different dipping numbers (2, 4, 6 8, and 10 times) of polyvinyl alcohol (PVA) solution using a dip coating method. The sensing performance of uncoated and PVA-coated optical fiber sensors in terms of its sensitivity for various relative humidity (RH) percentages ranging from 40 to 90 % RH was monitored using Ocean Optics spectrometer. The intensity peaks of PVA-coated optical fibers were increased linearly with dipping numbers. The optimum sensing performance was observed for 10 times dipping number of PVA solution with the highest intensity of 4100 counts at 60 % RH and exhibits good repeatability with precision error values in the range of 0 to 2 %. Furthermore, the gap difference between intensity counts due to % RH changes could be clearly observed for 10 times dipping numbers. These reported results are important to enhance the performance of humidity sensor for sensing and monitoring purposes.