A multimode fiber refractive index sensor

We present a simple refractive index sensor based on multimode fibers realized by stripping three different lengths of cladding. We theoretically explain and experimentally validate three mechanisms occurring in the multimode fiber for sensing surrounding refractive index. This sensor has been demonstrated at 1550 nm for a wide range of refractive index variation from 1.3164 to 1.608. Our sensor is very sensitive for measuring refractive index values lower than but close to the refractive index value of the fiber core.