Ethanol measurements are performed in an ethanol/water solution utilizing an ethanol sensor based on a hetero-core structured optical fiber covered with a layer-by-layer thin film. The layer-by-layer (LbL) thin film was prepared using poly (allylamine hydrochloride) and poly styrene sulfonate. When the sensor was immersed in water, the propagating light intensity decreased with increasing ethanol concentration. This behavior suggested that the LbL film contracted due to the presence of ethanol, and the refractive index of the film increased, resulting in increasing propagating light leaks at the hetero-core of the fiber. The ethanol sensor was applied to a variety of spirits, and the propagating light intensity decreased with increasing ethanol concentration.
Keywords: ethanol sensor; hetero-core structured optical fiber; layer-by-layer thin film.