Chitosan-coated polarization maintaining fibre for relative humidity sensing

• Main Author: Loh, Bi Ngoh.
• Other Authors: Chan Chi Chiu
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Science::Medicine::Biosensors
• Online Access: http://hdl.handle.net/10356/45151
• Institution: Nanyang Technological University

A fiber-optic-based humidity sensor has been fabricated using Polarization Maintaining (PM) fiber coated with Chitosan, a moisture-sensitive polymer [1]. The sensing concept exploits the inherent characteristics of the PM fiber and is examined based on different humidity level which induces changes to refractive index and stress induced birefringence through the swelling of the polymer coating. Chitosan films displayed swelling and permeability characteristics at different concentration. A strain effect on the fibers resulted from the water vapour absorption at different humidity level was observed by spectral phase shifts obtained from the detector. Experimental investigations were first conducted based on optical fiber’s response to changes in refractive index of the polymer coat, followed by examining the types of fiber -Single Mode and PM fibers, used for sensing. PM fibers revealed a higher sensitivity in comparison to the latter. Through the linear regression of derived data, the sensitivity of the sensor was observed to increase in response to decreased concentration of polymercoat,with 1% Chitosan-coat providing the best sensitivity. Further investigations by etching the cladding of fibers were done to analyze its sensing ability, and 1% Chitosan coat on etched PM fiber has proved to effect a higher sensitivity compared to un-treated fiber.