Interferometric determination of optical anisotropy in fibers III multilayer fibers

Abstract

Mathematical formulas are modified for the shape of two-beam interference fringes crossing a cylindrical multilayer fiber to determine the refractive indices and birefringence at the boundary of layers across the fiber diameter. An equation is also derived to calculate the parts of cross-sectional areas of the fiber layers. A polarizing interference microscope is used to determine the variation of refractive indices and birefringence at any point across the diameter of polyester and nylon fibers. Two fibers are used for each measurement. The first fiber is of known mean refractive index and dispersion properties. The other fiber is of unknown values of refractive indices of fiber layers. The calculations are carried out with both line and area methods using the derived mathematical formulas. Illustrations are given by microinterferograms.