Experimental analysis of SnO2 coated LMR based fiber optic sensor for ethanol detection

In the recent years, there has been an increasing demand for effective ethanol sensor in the pharmaceutical and food industries where there is a need to constantly monitor and maintain the permissible level of ethanol. In this study, we report the development of a fiber optic sensor based on Lossy Mode Resonance (LMR) technique using tin oxide (SnO2) thin film over the unclad core of the optical fiber as the sensing layer for measuring the ethanol concentration in an aqueous solution. Two sensor probes (SP1 and SP2) comprised of 600 mu m core with 120 nm SnO2 layer (SP1) and 400 mu m core with 250 nm SnO2 layer (SP2) were selected for measurement of ethanol concentration in the range of 0-100 vol% after optimizing eight sensor probes coated with SnO2 layers of different thicknesses. The ethanol sensing performance was characterized by a shift in the peak LMR wavelength for varying concentrations of ethanol. The sensor probe SP2 exhibits better sensitivity of 3.40 nm/vol% with a maximum sensor response of 13.3% for an ethanol concentration of 80%. The sensor probes exhibit good repeatability with a deviation of 0.26% and 0.12% for probes SP1 and SP2, respectively.