Digital optical logic using optically switching directional couplers

A novel optical logic gate with all-optical data signals is described. Control circuitry converts 100 MHz, -25 dBm square-wave optical pulses at lambda =1.3 mu m into electrical signals sufficient to switch the exchange state of LiNbO₃ 2*2 directional couplers in order to route similar optical pulses. Such optically-controlled directional couplers function as three-input, two-output logically complete gates for digital optical logic. Several digital optical circuits using these gates have been constructed and demonstrated.