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 the Runge-Kutta algorithm, respectively, and are applied to a homogeneous four-level erbium-doped fiber pumped at 1480 nm. Energy transfer due to cooperative up-conversion, cross relaxation, and excited state absorption is considered here. Comparisons with published experimental data confirm the present theoretical results.