The optical properties of ion-plating-deposited amorphous hydrogenated carbon layers are investigated. Experimental material is presented and discussed in terms of a dispersion model which considers polymer-like features of the spectra with methods taken from molecular spectroscopy (superposition of Lorentz lines) and the specifics of amorphous solids in terms of Sellmeier dispersion and Urbach absorption. The influence of nitrogen and oxygen incorporation on IR absorption has also been investigated.