<title>Profile refractometry of optical fibers by using double-refracting microinterferometry</title>

Abstract

ABSTRACTWavefront shear microinterferometric techniques are discussed as far as they apply to the determination of refractive index profiles of optical GRIN fibers. Special emphasis, however, is placed on a double-refracting microinterferometer with variable wavefront shear developed by the author of this paper more than 30years ago and then used by a number of researchers for profile refractometry of both fiber and planar lightguides. The microinterferometer incorporates birefringent prisms of Wollaston's type which are capable of giving both fringe-field and uniform-field interference patterns with various wavefront shear. The basic (patented) feature of this system is a combination of two simultaneously acting birefringent prisms localized in the image space of the microscope objective. Recently this instrument was used to phase-steppingtransverse interferometry of GRIN fibers and planar waveguides and professionally computerized in its commercial version. Keywords: wavefront shear interferometry, double-refracting microinterferometer, refractive index profile,gradient-index optical fibers