Tapered plastic optical fiber sensor for detection of ethanol concentration in H2O

This paper presents the preparation and characteristics of an intensity-based tapered plastic optical fiber (POF) coated with a mixture of poly-vinyl alcohol (PVA) and SiO₂ for sensing ethanol concentration in H₂O. The 1.0 mm-diameter POF was tapered to a diameter of about 730 μm using tensile tester with thermostatic chamber and the total tapered length was 5.0 cm. The tapered section was coated with a sensing element comprising of a mixture of PVA polymer and SiO₂ with a ratio of 9.0v%:1.0v%. A thin layer of protective coating was applied on this sensing element after it was thermally cured at 80°C. More light was guided into the core of the POF at sensing area with increasing concentration of ethanol. This effect is depicted from linear increase of light intensity within 630 nm to 644 nm wavelength region. The POF ethanol sensor has shown to exhibit repeatable results for measurement of 2.0% to 10.0% and 0.2% to 1.0% concentration of ethanol in water with the sensor sensitivity measured up to 35.67 per wt% of ethanol concentration.