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.
- Cascaded long-period gratings (LPGs)
- Optical fiber sensors
- Relative humidity (RH)
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering