Characterization of a polyimide-coated humidity sensor in a hybrid fibre grating configuration

摘要

A Relative Humidity (RH) sensor incorporating a Long Period Grating (LPG) and a Fibre Bragg Grating (FBG) in a series configuration was developed and evaluated. The LPG was coated with polyimide allowing it to respond to humidity changes while the FBG is used for temperature compensation. The hybrid sensor was then tested over the change in RH from 20-95 % and temperature of 20-80 °C. The sensitivity of the hybrid sensor to temperature and RH were determined to be 9 pm/°C and 0.23 nm/%RH, with negligible hysteresis (＜1% RH), showing the value of the dual LPG/FBG approach to optimize sensitivity.