Six 1.0 mol% Er2O3-doped lead fluoride zinc borotellurite glasses comprising different alkali metal oxides and fluorides (K2O, Na2O, Li2O, KF, NaF, and LiF) have been synthesized via melting and quick-quench approach and structural, thermal, optical, chromatic, upconversion, and NIR (near-infrared) emission features and fluorescence decay times were explored. Main structural units BO3 and BO4, as well as TeO4 and TeO3, are affirmed in all glasses networks by Fourier transform infrared and Raman spectroscopy. For transition 4I13/2 →4I15/2, σemi (emission cross-section) has been assessed by applying Füchtbauer–Ladenburg and McCumber's theories. For Li2O and NaF constituting glasses, acquired peak absorption cross-section (4I15/2→4I13/2) values are 0.999 × 10−20 cm2 and 1.093 × 10−20 cm2, while σemiM (4I13/2→4I15/2) values are 1.064 × 10−20 cm2 and 1.174 × 10−20 cm2 individually. At various P (population inversion) values, calculated gain spectra revealed the C- band amplification from P = 40%.