An apparatus includes one or more optoelectronic transducers, driving circuitry, one or more cooling elements, and a light coupling module. The optoelectronic transducers are configured to convert between optical signals conveyed over optical fibers and respective electrical signals. The driving circuitry is configured to process the electrical signals. The cooling elements are configured to remove heat that is produced at least by the driving circuitry. The light coupling module is configured to couple the optical signals between the optical fibers and the optoelectronic transducers, and additionally serves as a baseplate for the cooling elements.