Er3+ and Er3+/Yb3+ co-doped tellurite glasses, suitable for developing optical fiber laser and amplifier, have been elaborated from the conventional melt-quenching method. Results of differential scanning calorimetry (DSC) measurements indicate a good thermal stability of tellurite glasses. The DSC measurements show an improvement of thermal stability of glass hosts after adding P2O5. Absorption spectrum from near infrared to visible was obtained and the Judd-Ofelt (J-O) intensity parameters (Omega(2), Omega(4), and Omega(6)) were determined. Spontaneous emission probabilities of some relevant transitions, branching ratio, and radiative lifetimes of several excited states of Er3+ have been predicted using intensity J-O parameters. Absorption cross-section and calculated emission cross-section, using the McCumber method, for the I-4(13/2)-> I-4(15/2) transition, were determined and compared for the doped and co-doped glasses. Energy transfer (ET) and effect of changing concentration of P2O5 and Yb3+ ions on spectroscopic properties were investigated. It was found that the addition of P2O5 can increase the symmetry of the Er3+ ion. As a consequence, PL lifetime becomes more longer. The spectroscopic properties and the efficient infrared luminescence indicate that Er3+ doped TeO2-ZnO-Na2O-Er2O3 (TZNE) is a promising laser and amplifier materials and may be a potentially useful material for developing upconversion fiber optical devices. (C) 2010 Elsevier B.V. All rights reserved.