CONDUCTING SHEATH HELICAL WINDING ON THE CORE-CLADDING INTERFACE OF A LIGHTGUIDE HAVING A PIET HEIN SUPER ELLIPTICAL CORE CROSS-SECTION AND A STANDARD OPTICAL FIBER OF CIRCULAR CROSS-SECTION-A COMPARATIVE MODAL ANALYSIS

In this article, a theoretical and computational analysis has been made to obtain the modal dispersion characteristics of an unconventional optical waveguide with a Piet Hein core cross section having a conducting sheath helix winding on its core-cladding boundary. A simple analytical method using the vector boundary conditions has been utilized to get the modal eigen value equation. From this equation dispersion curves are obtained and plotted for some particular values of the pitch angles of the winding. Next, these predicted results are compared with those of a new optical fiber having a conducting sheath helix winding on its core-cladding boundary. It is seen that the cutoff values are somewhat lower for the Piet Hein lightguide than those for the circular guide. This is not unexpected since the Piet Hein curve approaches the shape of a square. The