Multiple-beam interference fringes applied to GRIN optical waveguides to examine fiber formation.

Multiple-beam Fizeau fringes revealed the existence of successive layers forming a graded-index fiber core.Both thickness and approximate refractive index graded from one layer to another have been estimated. The fiber is found to be formed from a succession of step-index layers, n(r), which remains constant over the thickness Deltar, yet follows the known function relating n(r) with r in terms of n(r = 0) and alpha. The index profile for graded-index fibers showing such microinterferograms.