The pulse widening in fiber communications causes a significant restriction of bit rate. The intermodal dispersion occurs not only in grade-index multimode fibers but also in the two-core single-mode fiber. The Goos–Hänchen (GH) shift is not considered in the conventional analysis based on geometric optics. The GH shift is calculated in the step-index fiber in this paper. The analytic expression is derived for calculating the pulse widening from intermodal dispersion in the multimode fiber. The analytic and numerical results show that GH shift has an important effect on the intermodal dispersion. The positive GH shift can decrease the pulse widening. The maximum transmission distance of a multimode fiber can be greatly increased when light propagates near the maximum critical propagation angle.

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