Characterization of optical fibers by two- and multiple-beam interferometry

Optical fibers have many advance and exciting applications, in particular optical telecommunication and sensing. These applications are depending basically on the fiber structure and on its index profile. Therefore precise and accurate determination of these profiles and their dispersion is needed. As a result, different methods and techniques for characterizing optical fiber structures and for determining their refractive indices have been developed. The most reliable and accurate technique for fiber investigations in the last three decades is the interferometric one. Thus through this review, the theoretical and experimental considerations of the transverse two- and multiple-beam Fizeau fringes techniques used to resolve and infer the structure and the index profiles of the optical fibers with high index and spatial resolution are discussed. The refractive index variation together with the deviation of many other fiber parameters in bent standard single-mode and graded-index fibers are discussed. Experimental observations and interferograms are presented.