Title :
Relative Humidity Sensor Based on Cascaded Long-Period Gratings With Hydrogel Coatings and Fourier Demodulation
Author :
Yu, Xiujuan ; Childs, Paul ; Zhang, Min ; Liao, Yanbiao ; Ju, Jian ; Jin, Wei
Author_Institution :
Dept. of Electron. Eng., Tsinghua Univ., Beijing, China
Abstract :
A Mach-Zehnder interferometer based on cascaded long-period gratings with a hydrogel thin-film coating is developed for monitoring the relative humidity (RH). The visibility of fringes and phase shift of the fringes are measured using Fourier analysis. The sensors show good linearity using the visibility of fringes from 60%RH to 100%RH with the ability to measure below 60% at reduced accuracy using the phase shift. An RH accuracy of 0.4% is achieved.
Keywords :
Fourier analysis; Mach-Zehnder interferometers; diffraction gratings; humidity sensors; hydrogels; Fourier analysis; Fourier demodulation; Mach-Zehnder interferometer; cascaded long period grating; fringe phase shift; hydrogel thin film coating; relative humidity sensor; Cascaded long-period gratings (LPGs); hydrogel; optical fiber sensors; relative humidity (RH);
Journal_Title :
Photonics Technology Letters, IEEE
DOI :
10.1109/LPT.2009.2034620
