The goal of multimode graded-index fiber manufactures is to get a fiber refractive index profile as close as possible to ideal parabolic profile that theoretically provides the highest bandwidth. However, various index profile defects of fiber preform (center defects as tips and dips, deviation of power-law parameter alpha from 2, core/cladding interface defects, bulges, etc.) can significantly reduce the modal bandwidth and, hence, degrade its performance. The characteristics of multimode fiber links may vary greatly from one link to another.
In this example we demonstrate how ModeSYS can be applied to use this statistical approach based on so-called Cambridge 81- fibers model. The approach of Cambridge model is to consider a set of pre-determined index defects that are believed to be representative for installed base of multimode FDDI-grade fibers, and to calculate fiber characteristics for those different distorted index profiles.
Figure below demonstrates the index profile with different distortions: