A method for producing an optical waveguide by: (a) depositing a first composition comprising: (i) a polysiloxane comprising epoxy and alkenyl groups, and (ii) a compound comprising an epoxy group, having molecular weight no greater than 1000 and a refractive index of at least 1.47 and (iii) a photo acid generator; and (iv) a hydrosilation catalyst (b) curing the first composition by exposure to ultraviolet light; (c) removing at least a part of the uncured portion of the first composition to produce a final patterned core layer; (d) depositing on the final patterned core layer a second composition comprising: (i) a polysiloxane comprising epoxy groups and alkenyl groups, and (ii) a compound comprising an epoxy group and a silicon-hydrogen bond, having molecular weight no greater than 1000 and a refractive index no greater than 1.45; (iii) a photo acid generator (e) heating at a temperature from 20 to 150° C. for 0.1 to 120 minutes; and (f) curing by exposure to ultraviolet light.