ZnO thin films have been prepared by the dip coating sol gel method. Zinc acetate dihydrate, 2-methoxyethanol and monoethanolamine (MEA) were used as precursor, solvent and stabilizer respectively. The synthesized sample was coated on glass substrate as the molarity of the solution was kept constant at 0.1 M. The structural properties and surface morphologies of ZnO thin film were characterized by XRD and FESEM. The optical properties such as transmittance, absorbance, reflectance and refractive index were studied by using UV-Vis. The functional group of the synthesized sample were verified by using FTIR. Average crystallite sizes of the samples were calculated by using Debye-Scherrer's formula. Next, ZnO is coated on POF in order to examine the reaction towards UV light.

An optimized study of tapered polymer optical fiber (POF) for measurement of different concentration of ethanol in deionized water (0.5%-3.5%) is proposed and demonstrated. This sensor operated based on evanescent wave absorption principle. The cladding of PMMA based POF is removed using organic solvents which can be used to create tapered POF. The unclad length around 1 cm and 3 cm as well as the waist diameters of POF in the range of 5 mm and 8 mm were compared for their efficiency as an ethanol sensor based on power output ratio values. Tapered POF with smaller waist diameter and longer tapered length showed higher sensitivity as ethanol sensor. Therefore, by tailoring the length and tapered diameter of POF, high sensitivity of ethanol sensor can be fabricated.