Optical properties of porous silicon superlattices are investigated using variable angle spectroscopic ellipsometry. Different phenomena such as in-depth inhomogeneities and interface transition regions are resolved and studied using various optical models. The optical properties of the samples are modified irreversibly by thermal oxidation yielding a blueshift of the reflectance. A reversible redshift of the spectra is obtained by vapor adsorption and liquid penetration into the superlattice. Moreover, existence of different specific internal surface areas and pore size distributions in the low and high index sublayers of the material is proposed.