Modelling of the pattern formation in microstructured fiber with active core

A new variant of localized function method is used for the simulation of beam propagation in photonic crystal fiber. The method based on the field approximation in terms of orthogonal Laguerre-Gaussian functions. Effect of the gain saturation on the formation of the beam structure in nonlinear photonic crystal fiber is investigated. For few-mode fiber the resulting beam structure depends strongly from initial conditions. The endlessly single-mode photonic crystal fiber operates at fundamental mode for a wide active region and large gain.