A method of preparing a planar optical waveguide assembly, comprising the steps
of: (i) applying a silicone composition to a surface of a substrate to form a silicone
film; (ii) 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; (iii) removing
the non-exposed region of the partially exposed film with a developing solvent
to form a patterned film; and (iv) 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 C. for light having a wavelength of 589 nm; wherein
the substrate has a refractive index less than the refractive index of the silicone
core. A planar optical waveguide assembly prepared according to the method of the invention.
