Multiple-beam interference fringes applied to GRIN optical waveguides to determine fiber characteristics

Abstract

A mathematical expression is derived for the shape of multiple-beam Fizeau fringes crossing a graded-index optical fiber inserted in a silvered liquid wedge. Formulas are obtained for calculating both α and Δn from fringe shifts. A formula is deduced for step-index fiber. Experimental results have been obtained from microinterferograms.