Transparency in optical amplifier repeaters

Transmission links with optical amplifier repeaters are potentially transparent to system upgrades such as increased bit rate or the addition of wavelength division multiplexed (WDM) channels. The potential ease of upgrade in the capacity of an optically amplified transmission link, from a single channel to one hundred channels, is demonstrated in a 300 km 622 Mb/s coherent transmission experiment. The authors consider the limitations imposed by amplifier noise and discuss the degree of transparency that can be achieved with currently available optical amplifiers.<<ETX>>