Nonlinear profile dispersion aids optimisation of graded-index fibres

The bandwidth of graded-index fibres is limited not only by distortions of the refractive profile, but also by nonlinear profile dispersion caused by the dependence of the profile shape on wavelength. An efficient method is presented here, which helps to understand the interaction of both effects, shows a new way to minimise total dispersion by matching the two effects and simplifies the calculation of pulse broadening in imperfect real fibres.