The optical transmission spectra of amorphous Ge-Se films of chemical composition GeSe3r prepared by thermal evaporation, are measured over the 300 nm to 2500 nm spectral region. A simple, straightforward procedure suggested by Swanepoel, which is based on the use of interference fringes, has been applied in order to derive the real and imaginary parts of the complex refractive index, and also the film thickness. Furthermore, thickness measurements made by a surface-profiling stylus are also carried out to cross-check the results obtained by the present optical method, employing only T(lambda). The dispersion of n is discussed in terms of the single-oscillator Wemple and DiDomenico model, and the optical band gap E(g)(opt) has been determined from the absorption coefficient values, using the Tauc procedure.