The effects of Er2O3 (0-8 mol%) doping and Er2O3 and Yb2O3 codoping (total 1-7 mol%) on the absorption cross-section, PL, and upconversion intensities of the SnO-P2O5 glass have been investigated. Precipitation of ErPO4 and the (Yb, Er)PO4 crystalline phase in the SnO-P2O5 glass matrix when the total rare-earth oxide content is >4 mol% plays an important role in determining the absorption cross-section, PL, and upconversion intensities. For Er3+-doped glass, the variation of the PL characteristic with the Er2O3 content is obviously different from that for general rare-earth-doped glasses. This result is explained in terms of the light-scattering effect caused by the ErPO4 crystals and the constant Er-Er distance in ErPO4 crystals with increasing Er2O3 content. After codoping with Yb2O3, the PL intensity of the glass is enhanced by about 14.7 times at the optimum Yb2O3 content of 6 mol% (similar to 1.81 x 10(21) ions/cm(3)). Further increase in the Yb2O3 content results in the reduction of PL intensity, which can be explained in terms of the APTE upconversion effect.