Elliptical and Circular Step-Index Fibers With Conducting Helical Windings on the Core-Cladding Boundaries for Different Winding Pitch Angles - A Comparative Modal Dispersion Analysis

Abstract

Abstract-The propagation characteristics of an elliptical step-index fiber with a conducting helical winding on the core-cladding boundary are investigated analytically and compared with those of a circular step index fiber with a conducting radial winding. Our optical waveguides are unconventional: in view of the existence of helical conducting windings on the core-cladding boundaries. Appropriate coordinate systems, circular cylindrical and elliptic cylindrical, are chosen for the circular and elliptical fibers. Applying the boundary conditions as modified by the presence of conducting helical windings, the characteristic equations are obtained for both the fibers. Dispersion curves are also obtained for two special values of the helical pitch angle ψ, namely, for ψ = 0 • and ψ = π 2 for each fiber and the results have been compared. It is found that the introduction of the helical winding has two main effects on the characteristics of both types of fibers. These are: (1) The helix introduces band gaps and (2) has the effect of splitting a mode into a pair of adjacent modes In the case of the elliptical helically clad waveguide we find two band gaps for V < 30 whereas for circular guide we have only one band gap in the same range of V -values, V being the normalized frequency parameter.

Towards the Characteristic Dispersion Relation for Step-Index Hyperbolic Waveguide With Conducting Helical Winding

“…Watkins himself cited the works of Brillouin [26], Kornhauser [27], Mathers and Kino [28]. Kumar and Singh [29][30][31] have also presented earlier the study of elliptical fibers with conducting helical windings, and it was reported that the effect of the helical pitch angle was almost negligible for the guides having small eccentricity values. Further, in that work the parameter related to the helical pitch angle was not present in all terms of the dispersion relation.…”

Technique for Inhomogeneous Profiles in the Cross-Section of the Helical Rectangular Waveguide

“…Fast-wave analysis of an inhomogeneously-loaded helix enclosed in a cylindrical waveguide has been published by Ghosh et al [12]. The characteristics of the propagation of an elliptical step-index fiber with a conducting helical winding on the core-cladding boundary are investigated analytically [13]. The core and the cladding regions are assumed to have constant real refractive indices n 1 and n 2 , where…”

Wave Propagation in a Helical Waveguide With Slab and Rectangular Dielectric Profiles, and Applications

“…The tape-helix model has been used which takes into account the effect of the space-harmonics, and is used particularly in the cases that the structure is operated at high voltages and for high helix pitch angles. The propagation characteristics of an elliptical step-index fiber with a conducting helical winding on the core-cladding boundary [12] are investigated analytically where the coordinate systems are chosen for the circular and elliptical fibers. In their waveguides the core and the cladding regions are assumed to have constant real refractive indices n 1 and n 2 , where n 1 > n 2 .…”