Effect of Helix Pitch Angle on the Modal Dispersion Characteristic of Step-Index Optical Fiber

Ashish Kumar Mishra,Deepak Kumar,Onkar Nanth Singh

doi:10.4236/jemaa.2012.47038

Abstract

The general characteristic equation is derived for the helically cladded step-index optical fiber. The dispersion curves are drawn for the different pitch angles Ψ and mode order ν = 1. The effect of helix pitch angle on the dispersion characteristics and also on the modal cut-off condition is examined. Except for the lowest order mode, all the modes appear in pairs. The lowest order mode displays the negative dispersion for the some value of normalized frequency V and depends on the helix pitch angle Ψ.

Highlights

Optical waveguides have been investigated extensively since past few decades considering the different crosssectional geometry and different refractive index profiles [1,2,3,4,5,6,7,8,9,10]
The basic difference between a metallic and a dielectric waveguide lies in the way of confinement and guidance of electromagnetic waves—the waves are guided by the reflection from a conducting boundary in the former case while in the later case, the wave guidance is achieved by the total internal reflection phenomenon (TIR)
The general characteristic equation, which is valid for any mode order ν and helix pitch angle ψ, is derived by employing the helical boundary condition

Summary

Introduction

Optical waveguides have been investigated extensively since past few decades considering the different crosssectional geometry and different refractive index profiles [1,2,3,4,5,6,7,8,9,10]. A concise method for the designation of modes, which is valid for the waveguides of arbitrary refractive index profile, arbitrary number of. Though the introduction of helix over the core displays a complex structure of the optical fiber, still it has the technological importance in the field of travelling wave tubes (TWTs). The comprehensive and elaborative study of the dispersion characteristic of helically cladded step-index optical fiber is presented assuming the winding spacing to be uniform (i.e. the number of turns per unit length of the fiber) throughout for all the pitch angles (0 ̊ - 90 ̊). The general characteristic equation, which is valid for any mode order ν and helix pitch angle ψ, is derived by employing the helical boundary condition. The central idea behind the study of such a complex waveguide germinates from the fact that it will find great technological importance in the field of optical communication

Theoretical Analysis

Results and Discussion

Conclusion