A numerical analysis for erbium-doped tellurite-based fiber amplifiers (EDFA) is presented for the first time in the literature. Modal and propagation equations are solved using the finite element method and a Runge-Kutta algorithm, respectively, and applied to a homogeneous four level erbium-doped fiber pumped at 1480nm. Energy transfer due to cooperative up-conversion, cross relaxation and excited state absorption is here considered. Comparisons with published experimental data confirm the present theoretical results.