None of data communication systems is absolutely reliable in practice because of noise, distortions, interferences, or other forms of impairments. Therefore, the systems need error control strategies in order to detect or to correct errors occurring in the transmission process. Controlling transmission errors in data communication systems can be performed by using either automatic-repeat-reques...

For secure and high capacity optical fiber communications, WDM transmission experiment of 100-Gbit/s quantum stream cipher is demonstrated by Y-00 protocol with 64-level intensity modulation. Error-free transmission (bit-error rate < 10-9) in an 120-km amplifier repeated fiber link is successfully achieved.