Three-dimensional refractive index profile of a GRIN optical waveguide using multiple beam interference fringes

Multiple beam Fizeau fringes across a GRIN fiber immersed in a silvered liquid wedge have been used to obtain a three-dimensional refractive index profile of optical fiber core. An image processing system has been used to analyze the fringe shape across the fiber cross-section. A simple mathematical approach has been applied utilizing the resulting experimental data to estimate the fiber three-dimensional refractive index profile. The tomographic back projection technique has been applied.