Transparent glasses 40Sb(2)O(3)-20ZnF(2)-(40 - x)GeO2:xCuO, and 40Bi(2)O(3)-20ZnF(2)-(40 - y)GeO2:yCuO with x=0, 0.6 and 0 <= y <= 1 wt% were prepared by melt quenching technique and were characterized by XRD and differential thermal analysis. Spectroscopic studies like optical absorption, FTIR, Raman, EPR and dielectric parameters (such as epsilon', loss(tan delta), and sigma(ac)) were carried out to examine the modifier and dopant effect on zinc germanate glass network. Optical absorption and EPR data have revealed that the environment of Cu2+ ions is more ionic in bismuth series rather than antimony glasses. Reduced bismuth ions have been found in pure and at lower concentration of dopant in Bi2O3 mixed glasses, which are useful for IR amplifications. FUR and Raman spectra have indicated the conversion of GeO4 to GeO6 structural units by forming cross linking bonds like Bi-O-Ge, Ge-O-Cu, etc., and open the glass network with integration of Bi2O3 and CuO doping. It is also confirmed by decreasing T-g and E-g values. The temperature dependence of dielectric parameters at different frequencies was interpreted in terms of structural changes in the glass network. (C) 2012 Elsevier B.V. All rights reserved.