A circuit board assembly includes a circuit board, a first optical transceiver electrically connected to the circuit board, a first transparent shell optically coupled with the first optical transceiver, a second optical transceiver electrically connected to the circuit board, a second transparent shell optically coupled with the second optical transceiver, and a plurality of light wave guides optically coupled with the first transparent shell and the second transparent shell. The first optical transceiver sends first light signals. The first light signals are transmitted through the first transparent shell, the light wave guides, and the second transparent shell and are received by the second optical transceiver. The second optical transceiver sends second light signals. The second light signals are transmitted through the second transparent shell, the light wave guides, and the first transparent shell and are received by first optical transceiver.