Performance of multi-gigabit/sec transmission systems using erbium doped fiber amplifiers

The results of a series of 11-Gb/s system experiments incorporating one or more erbium-doped fiber amplifiers are reported. These experiments employed 1550-nm directly modulated DFB (distributed feedback) lasers and an 11-Gb/s timing recovery circuit over span lengths as long as 260 km. Also discussed are various system-degrading effects which can adversely affect lightwave systems employing fiber amplifiers, including the effects of signal-spontaneous beat noise and the recently discovered multiple reflection effects involving Rayleigh backscattering and Brillouin scattering in the presence of optical amplifiers. It is found that the incorporation of optical isolators in fiber amplifiers operating with high gain or high output power will be required in order to ensure reliable system performance