FIBER OPTIC SENSOR FOR THE MEASUREMENT OF CONCENTRATION AND REFRACTIVE INDEX OF LIQUIDS BASED ON INTENSITY MODULATION

Abstract

This paper reports the use of fiber optic sensor consists of two-fiber probe and reflector for the measurement of concentration and refractive index of liquids based on the reflective intensity modulation. Conventionally such a sensor is used for measuring micro-displacement of fiber tip with reference to the reflector. In one of the previously reported work we have established that if the separation between fiber tips and reflector is maintained constant the same arrangement can be directly used for sensing refractive index changes of medium. The liquid under test fills the gap between probe and reflector. Depending upon the refractive index of liquid, angle of emittance will change which will decide the received output power by receiving fiber. Apart from pure solvents which have different refractive indices, there are mixtures of various types which also alter the refractive index of a given medium. The developed sensor is used to detect the concentration of the alcohols like methanol & ethylene glycol in mixture with water.