COHERENT COMBINING OF RF SIGNALS IN A TRAVELING-WAVE PHOTODETECTOR ARRAY

Analog fiber-optic links are used in a variety of microwave applicatio ns, The RF insertion loss and RF output power available from these lin ks is currently limited by photodetector optical power handling, Using traveling-wave concepts similar to those in distributed amplifiers, w e have demonstrated traveling-wave detector arrays (TWDA's) in which p hotodetectors are embedded within an artificial transmission line. By feeding this network with suitably time-delayed optical signals, this arrangement coherently combines the RF photocurrents from two detector s, yielding a 6-dB improvement in insertion loss and RF output power, while retaining 12 GHz of operating bandwidth.