The optical properties and structural characteristics of copper doped SiO2 coatings, prepared using the sol-gel method, were determined from spectroscopy ellipsometry, optical transmission and x-ray diffraction measurements. Coatings with 8 and 25 at. wt % of copper were analyzed. The samples were heat treated in air and under a CO atmosphere at various temperatures. The x-ray data show that samples thermally treated, in air have an amorphous structure. In the coatings with 25 wt % of copper and annealed in the reducing atmosphere, there is precipitation of copper particles with nanometer sizes. The effective complex index of refraction of the coatings is deduced from the ellipsometric data using the Forouhi-Bloomer and Maxwell-Garnett expressions for samples with amorphous and composite structures, respectively. The optical transmission measurements indicate that Cu2+ ions are present in oxidized samples. The optical density spectra from reduced samples were analyzed with the Mie theory. There is a good agreement between the results from the different measurements.