Gain and numerical modelling of rare-earth doped fiber devices

We compute the evolution of a signal, pump, backward and forward ASE in a fibre laser in a model that takes into account the modal shape of the radiation fields, the spectral shape of cross sections and of forward and backward propagation ASE, pump power depletion, and saturations due to ASE and or signal. The model can be easily extended to different rare-earth fibre lasers configurations subject to some constrains, since the physics remains the same in many cases. Some spectroscopy data of important fibre fabrication companies and published papers are then used to calculate the amplification, and gain. Three different rare earth doped fibres (namely ytterbium, neodymium, and thulium) were objects of this analysis. Finally, the numerical calculations showed to be in good agreement with reported experimental results (slope efficiency, etc).