Characterization of fiber optic evanescent wave sensor for water quality monitoring

Cheah, Wan Chen (2024) Characterization of fiber optic evanescent wave sensor for water quality monitoring. Project Report. Universiti Teknikal Malaysia Melaka, Melaka, Malaysia. (Submitted)

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Abstract

In this project, an evanescent wave fibre-optic sensor for detecting water quality is proposed and studied experimentally. The fiber is set up by tapered manually using a polishing method to a diameter of 0.6 mm and coated with zinc oxide (ZnO) nanorods. This project technique is divided into two parts: optical characterization and electrical characterization. The light source meter, POF sensor, and Output Power Meter are used in the Optical Characterization section to evaluate the water quality by measuring the output power loss of the water sample. The receiver circuit is built for the Electrical Characterization to sense the output voltage variation to the water quality level of the water sample. From this project, the experimental results revealed that the sensor has linear relationship with ammonia concentration ranging from 1 mg/L to 1.8 mg/L and pH levels ranging from 5 to 9. It has been found that the concentration is proportionally related to its refractive index where high refractive index will experience greater loss since the light rays tend to be refracted out of the fiber instead of being internally reflected. Upon completion, the highest sensitivity and linearity was achieved by fiber optic sensor with coated ZnO, with 0.0128 V/mg

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