Opto-electrical exclusive or logic gates

An opto-electronic XOR gate includes a pair of diode type light sources connected back to back in parallel by a pair of input leads to which first and second electronic logic signals are applied. With only one logic signal in the high state, one of the diode-type light sources is forward biased while the other is reverse biased. With both logic signals high or low neither diode-type light source emits. A two to one fiber optic combiner (FOC) provides a single optical output which is on only when only one electrical signal is high. If an electronic output is desired, a single photodetector converts the output of the FOC to an electronic logic signal. For performing the exclusive OR operation on optical input signals, a pair of photodetectors and buffer amplifiers and connected to the input leads. For 10 to 12 GHz switching speeds laser diodes are used as the diode-type light sources. When lower switching speeds are satisfactory, light emitting diodes can be used as the diode-type light sources.