Abstract: An optical interface including a base with molded optical waveguides and overmolded electrical conductors, with a keyway formed therein. A keyway mating portion molded around the ends of a plurality of optical fibers to expose the ends of the fibers. With the keyway mating portion engaged in the keyway, openings in a surface of the keyway communicate light to/from the fibers, through the optical waveguides, from/to semiconductor devices on the base. The keyway accurately aligns the mating portion which aligns the ends of the fibers with the openings and, hence, the optical waveguides. Two different waveguide molding techniques are used and diffraction gratings are used to introduce and/or receive light from the ends or mid-points of the waveguides.