The ring structure of self-focusing light in optical fibres

Abstract Self-focusing of picosecond pulses in a large-core silica fibre was investigated. A ring structure of self-focusing light field was observed. The ring structure was attributed to the intrinsic refractive index profile of the fibre used in the experiment. Numerical calculation was carried out based on a square-profile-ring-shaped local waveguide model, showing good agreement with experimental result.