A design of SPR based fiber optic ethanol biosensor is presented by using enzyme alcohol dehydrogenase and nicotinic
acid. The sensing probe is fabricated with the coating of 40 nm thin film of silver metal and immobilization of alcohol
dehydrogenase and nicotinic acid by gel entrapment method over unclad core of a multimode optical fiber. The SPR
spectra of ethanol samples of concentrations ranging from 0 mM to 10 mM prepared in buffer have been recorded. The
sensor works on the spectral interrogation technique and operates in the visible range of the spectrum. The SPR curves
are blue shifted with the increasing concentration of ethanol and the sensitivity of the sensor decreases with the
increasing concentration of ethanol. The sensor has many advantages such as fast response, stability, small probe size,
low cost and can be used for remote/online monitoring.