Lumped versus distributed description of mode-locked fiber lasers

We present an analytical derivation of the distributed model from the experimentally well confirmed lumped approach for the description of light propagation in mode-locked fiber lasers operating in the scalar regime where the dynamics is mainly governed by the propagation of a single field component. As a limiting case of the distributed model we identify the complex cubic-quintic Ginzburg-Landau equation (CQGLE). One important result consists of deriving explicit relations between the coefficients of the distributed models to the realistic laser parameters. We numerically demonstrate that the results obtained by using the general distributed model are in very good agreement with those of the lumped model, whereas results of the CQGLE can significantly deviate for a certain range of parameters. Moreover, we demonstrate that the validity of the CQGLE approach strongly depends on the operation regime of the saturable absorber. (C) 2010 Optical Society of America