Abstract
Cooperative up-conversion and excited state absorption are the main limiting factors of short cavity erbium-ytterbium doped fiber lasers like DFB fiber lasers. In this report we quantify the influence of these detrimental effect by numerical modelling. The results of our analysis demonstrate that cooperative upconversion account for almost 10% in reduction of the laser output power. In addition, laser threshold and slope efficiency of the laser are also strongly influenced by cooperative upconversion and excited state absorption.