Practical design considerations for optical transmission systems using cascaded semiconductor amplifiers

It has long been realised that optical amplifiers give the potential to produce ultra long-span unregenerated optical communication systems. Not only has there been theoretical work demonstrating that the amplifier characteristics will allow multi Gbit/s transmission over hundreds of kilometres, but more recently the necessary experimental confirmation is being provided. In this paper, the description of one such experiment is followed by a discussion of some of the practical design rules which need to be considered if one of these systems is to be implemented in the field.