The index-profile characterization of fiber preforms and drawn fibers

The information carrying capacity of multimode optical fibers is mainly determined by the quality of the refractive index distribution of their cores which, in turn, is determined by the distribution existing in the fiber's parent--the preform. This paper reviews methods that can be used to measure the index profiles of preforms--both multi-mode and single mode. Attention is also given to the effects of profile perturbations and means of eliminating them, as well as to applications of the techniques to fiber profiling.