A connector assembly is provided that mates on one side with an optical transceiver module holder and that electrically connects on the opposite side with an external system circuit board. When the connector assembly is mated with an optical transceiver module holder, a base of a parallel optical transceiver module held in the holder mates with a socket of the connector assembly such that respective arrays of electrical contacts disposed on the base and in the socket come into contact with one another. At least one gearbox IC for performing data rate conversion is mounted on the assembly circuit board. A lower surface of the assembly circuit board has an array of electrical contacts on it that are in contact with an array of electrical contacts disposed on the surface of the external system circuit board on which the connector assembly is mounted.