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

Abstract

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.

Multiple-beam interference fringes applied to investigate the index profile of the optical fiber dip

“…The figure provides information about the core structure and the distinctive features of the index profile through the discontinuity in the core fringe. It reveals the existence of multi-layers of constant thickness and a step-pyramid-like index profile (Barakat et al 1988). The dopant GeO 2 concentration is increased towards the optical axis in equal steps from one layer to the next keeping the layer extension constant.…”

“…This technique has been used to determine the refractive index, birefringence and dispersion of natural, synthetic and optical fibers (Barakat and Hammza 1990;Barakat 1971;Saunder and Gardner 1977;Barakat et al 1985Barakat et al , 1988Hamza 1980;Brakat et al 1993Brakat et al , 1996. Also it has been applied to GRIN optical fibers to determine the fiber characteristics and examine their formation, neglecting the existence of the optical fiber dip (Barakat and Hammza 1990;Barakat et al 1985Barakat et al , 1988Hamza 1980;Brakat et al 1993Brakat et al , 1996. In this technique the optical fibers are considered as a phase objects that induce a phase shift to a light beam traveling through them.…”

“…Also using Eq. (20), the theoretical values of the fringe shift, in case of constant refractive index dip knowing n c (r d )(Barakat et al 1988) can be calculated.…”

Characterization of Optical Fibers by Multiple-Beam Interferometry

“…[92] The effect of the immersion liquid on the shape of the fringes crossing the core and the cladding has been dealt with to examine the fiber cladding and its index homogeneity, presenting a method to control the process of cladding production. [93] Barakat et al [94] studied also 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.…”

Applying multiple-beam Fizeau fringes for measuring the refractive indices of liquids

“…MBFFs formed across a fibre material when immersed in a silvered liquid wedge illuminated by a parallel beam of monochromatic light have been used to measure the refractive index and birefringence of natural and synthetic fibres [3][4][5][6][7]. These fringes have also been used to examine the layer structure of graded index fibre [8].…”