Densely spaced FDM optical coherent system with near quantum-limited sensitivity and computer-controlled random access channel selection

An FDM coherent optical network consisting of six 200 Mbit/s-FSK channels spaced by 2.2 GHz, is reported. Receiver sensitivity of 74photons/bit for a BER of 10−9 is obtained. The channels are randomly accessed by computer control. The system has the potential to provide a throughput of 2000 Gbit/s.