Numerical simulation of DBR erbium-doped fiber lasers

It is aim of this paper to present the results of the simulation of DBR fiber lasers throughout a model based on the rate equations for pump and signal power and for the population of the upper laser level. The DBR laser cavity has been considered with two equal fiber gratings; the model considers the effect of the transversal overlap between the pump mode profile, the signal mode profile and the population inversion, the mode competition among longitudinal modes and the up-conversion process due to the formation of clusters of Er ions because of the high dopant concentration. The mode competition has been considered through the saturation effect on the population inversion due to the standing wave of the lasing cavity mode. The overlap integral along the cavity between the saturated population inversion and the nonlasing longitudinal modes with different standing wave pattern allows to determine their threshold condition. Simulations have been performed in order to determine the monomodality region for different value of the peak reflectivity of the Bragg reflector and different cavity length. The threshold of the fundamental and of the adjacent longitudinal mode in presence of the lasing mode, have been determined for two different values of the Er maximum concentration.