In general, in one aspect, a method includes forming conductive layers on a wafer. A through cavity is formed in alignment with the conductive layers. The through cavity is to permit an optical signal from an optical waveguide within an optical connector to pass therethrough. Alignment holes are formed on each side of the through cavity to receive alignment pins. The wafer having the conductive layers, the through cavity in alignment with the conductive layers, and the alignment holes on each side of the through cavity forms an optical-electrical (O/E) interface. An O/E converter is mounted to the metal layers in alignment with the through cavity. The alignment pins and the alignment holes are used to passively align the optical waveguide and the O/E converter.