System including backplane, and first and second circuit boards. First circuit board is attached to backplane and has first optical signal transmitter. Second circuit board is attached to backplane and has first optical signal receiver. First optical signal transmitter and first optical signal receiver are separated by free space and form optical communication link configured for circuit board test signal communication from first circuit board to second circuit board through the free space. Method includes providing backplane and first and second circuit boards, where first circuit board is attached to backplane and has first optical signal transmitter, and second circuit board is attached to backplane and has first optical signal receiver. First optical signal transmitter and first optical signal receiver are separated by free space, and form optical communication link. Method additionally includes transmitting circuit board test signal from first circuit board to second circuit board through the free space.