An optical waveguide with a hypocycloidal core cross-section having a conducting sheath helical winding on the core-cladding boundary - A comparative modal dispersion study vis-a-vis a standard fiber with a sheath winding

Abstract

A simple analytical method using vector boundary conditions is proposed for the theoretical derivation of the modal characteristics equation for an unconventional optical waveguide having a hypocycloidal core cross-section with a conducting sheath helix winding on its core-cladding interface. Using this equation modal dispersion curves have been obtained for some particular values of pitch angles of the winding. Further, these obtained results are compared with those of a standard optical fiber loaded with a conducting sheath helix winding on its core-cladding interface. It is found that the cutoff values are somewhat lower for the hypocycloidal waveguide than those for the standard fiber. This is due to the fact that when a hypocycloid is distended from the inner side we get a circle and when a square is compressed from outside we get a hypocycloid. We also see that when a conducting sheath helical winding is added to the waveguides, their modal properties are modified. Among many new features, it is found that the hypocycloidal guide with a conducting helical winding supports fewer mode than the circular waveguide with a conducting helical winding, and this is relevant in the case of practical application.