Abstract Er3+ doped germanate glasses modified by Y2O3 and Nb2O5 have been prepared. A detailed discussion of J–O parameters has been carried out based on absorption spectra and Judd–Ofelt theory. Mid-infrared transmittance spectra and 2.7μm emission properties have been investigated. To understand 2.7μm fluorescence behaviors, 1.53μm emission spectra, radiative lifetimes, non-radiative relaxation rate constants of the 4I11/2→4I13/2 transition and energy transfer coefficients of 4I13/2 level have been obtained and discussed. As a result, the investigated samples with excellent spectroscopic properties might be appropriate optical materials for mid-infrared laser and amplifier applications.