Mode coupling in graded-index optical fibres due to microbending

The effects of microbending on mode coupling in graded-index optical fibres are investigated through a ray-optics approach and the standard Fokker-Planck theory. This model can be applied to any kind of index profile and statistics of the perturbation. In particular, for a parabolic index fibre and for a perturbation with microscopic correlation, a closed form expression of the optical power steady-state distribution is derived.