A circuit substrate, which supports optically and electrically conveyed signals, and method for forming the same are provided. The circuit substrate includes a substrate upon which one or more electrically conductive traces are formed, where the electrically conductive traces have areas of isolation between adjacent ones of the electrically conductive traces. The circuit substrate further includes one or more optical waveguides, where the one or more optical waveguides are in the same plane as the one or more electrically conductive traces. The optical waveguides are formed using an optically transmissive material, which is deposited in the areas of isolation between the electrical traces.