Optical characteristics of the prepared glasses of composition 55 P₂O₅ – (45-x) Na₂O – x Li₂O were ( 0 ≤ x ≤ 35 mol% ) have been investigated by X-Ray diffraction (XRD), differential thermal analysis (DTA), density (ρ), molar volume (V_m), optical packing density (OPD), UV spectroscopy and Fourier transform infrared (FTIR). The FTIR studies revealed the vibrational modes of prepared glass samples. Absorbance of investigated glasses was measured and used to estimate their optical absorption coefficient and optical energy gap. The optical studies revealed that the indirect optical band gap (E_opt) increases from 3.2-3.5 eV and the Urbach energy decreases from 1.133-0.838 eV with increase of Li₂O content from zero up to 35 mol% Li₂O.