Guided propagation in a step-index, multi-mode fiber: effect of index difference variation on allowable TM propagation constants

The effect of variation of core and cladding index difference, Δn=ncore−ncladding, on allowable values for the guided mode transverse magnetic propagation constants within a step-index, multi-mode optical fiber is investigated. We use a iterative computational technique to calculate the propagation constants for modes inside and outside the core that satisfy the boundary conditions contained within the characteristic eigen-equation for the TM field components. Evidence of a strong dependence of the allowable propagation constants on changes of Δn is shown.