Quality Detection of Alcoholic Beverages Using Optical Fiber Tips

This paper presents the direct detection of the quality of alcoholic beverages by simultaneously measuring the refractive index and evaporation rate using an optical fiber tip. The fiber tip acts as a submicrometer axicon lens. The optical path difference between the glass tip and outside medium results in a focused spot with its intensity modulated by the refractive index (RI) of the medium. The intensity sensitivity is as high as 5000%/RI unit for 32° tapered angle. When the fiber tip is immersed in a drop (300 $\mu \text{L}$ ) of alcohol, the measured optical intensity is gradually decreased due to the evaporation of solvent. The evaporation rate and the refractive index are intrinsic properties for various alcoholic beverages. Both parameters can be used together to identify the quality with high sensitivity and specificity. We used the sensitive fiber to detect different wines, wine frauds with methanol and water. Clear differences for different ratios of the fake wines were observed from the initial RI and evaporation rate.