Optical amplifiers for WDM systems and networks

The emergence of practical fiber-amplifier chains has raised the prospect of transparent lightwave networks, in which signals travel from source to destination through a sequence of intermediate nodes without optoelectronic conversion. When such networks employ multiple wavelengths, however, some of the most substantial new research challenges are those posed by the amplifier chains themselves. Such networks suffer from accumulating inter-channel power-spread, from sensitivity to inter-amplifier loss variations, and from transient cross-saturation, as the network undergoes reconfiguration. The authors describe two different approaches to address these problems