One-gigabit per second free-space optical interconnection

A simple and efficient board-to-board optical interconnection consisting of only a laser, two lenses, and a detector demonstrates the direct free-space interconnection of digital circuits. No external laser driver, detector preamplifier, or other interface circuitry was required because of the high efficiency of the link. A differential electrical-to-electrical current efficiency as high as 19% was measured. The interconnection operates at clock rates of 1 GHz.