Simulation and experimental studies of an extrinsic fiber optic sensor for liquid refractometry

The working of a fiber optic sensor for sensing of refractive index of liquids based on intensity modulation is studied in detail. Mathematical modeling and simulation for the intensity of light collected by parallel, flat-tipped, dual fiber probe immersed in liquids of different refractive index are carried out. The model consists of transmitting fiber, receiving fiber, reflector and liquid medium of different refractive index. A cone of light emerges out of the transmitting fiber gets reflected in the form of cone of light toward receiving fiber. This cone of angle gets modified in accordance with refractive index of the liquid medium. The output intensity may be determined by considering the overlap area between the receiving fiber core and cross-section of reflected cone emitted by the image of a transmitting fiber. The proposed model takes into account various effects such as numerical aperture of fiber, change of refractive index of liquid medium, and scattering effect. Finally experimental results are compared with simulated ones. (C) 2012 Elsevier GmbH. All rights reserved.