There is provided an adapter device for connecting and interfacing a transceiver module in conformance with first mechanical specifications and first connector specifications into a host socket adapted to receive transceiver modules in conformance with second mechanical specifications and second connector specifications. The adapter device comprises: a rigid-flex circuit board having first and second levels of rigid circuit board portions and a flexible circuit board portion interconnecting the two levels to convey high-speed electrical signals therebetween, the two levels being integral with said flexible circuit board portion; a first connector mounted on the first level of rigid circuit board and in conformance with the first connector specifications, for electrically connecting the transceiver module to the adapter device to convey high-speed signals; and a second connector mounted on the second level of rigid circuit board and in conformance with the second connector specifications, for electrically connecting the adapter device into the host socket to convey high-speed signals.