Refractive Index Measurements of Ethanol–Water Binary Liquid Solutions Using a Graded-Index Fiber Tip Sensor

The refractometric analysis of ethanol–water mixtures is hampered because this type of binary solution does not present a linear behavior. In this letter, a multimode graded-index fiber (GIF) tip sensor for the measurement of ethanol in binary liquid solutions of ethanol–water is proposed. The proof is fabricated by the fusion–splicing of a 500 μm GIF to a single-mode fiber (SMF), and it operates as a refractometric sensor in reflection. To evaluate the prove potential to detected ethanol variations, samples of ethanol–water mixtures were measured at different temperatures (20 °C–60 °C). The samples have different %(v/v) of ethanol, in a range between 0% and 100%.