A series of ternary phosphate glass systems required for infrared (IR) photonic device fabrication is synthesized by the melt-quenching technique. The effect of replacing (divalent) ZnO with (monovalent) Na2O on optical properties of the glass systems is investigated. The dependence of the refractive index on composition is measured over a wavelength range of 1 to 2.5 μm; the second-order nonlinear refractive index is inferred. The different factors that play a role on controlling the glass refractive index, such as electronic polarizability, bridging and non-bridging oxygen, optical basicity, and ionic interaction parameter of oxides are discussed. IR vibrational spectroscopy is used as a structural probe of the nearest neighbor environment in the glass network. The present glasses are proper to be applied in C -band telecommunication systems around 1550 nm.