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

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 char-acteristics 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 de-pends on the helix pitch angle Ψ