A planar optical waveguide assembly prepared by a method comprising the steps of (i) applying a curable polymer composition to a surface of a substrate to form a polymer film; (ii) curing the polymer film to form a lower clad layer; (iii) applying a silicone composition to the lower clad layer to form a silicone film; (iv) exposing at least one selected region of the silicone film to radiation having a wavelength of from 150 to 800 nm to produce a partially exposed film having at least one exposed region and at least one non-exposed region; (v) removing the non-exposed region of the partially exposed film with a developing solvent to form a patterned film; and (vi) heating the patterned film for an amount of time sufficient to form at least one silicone core having a refractive index of from 1.3 to 1.7 at 23.degree. C. for light having a wavelength of 589 nm; wherein the lower clad layer has a refractive index less than the refractive index of the silicone core.