Granularity in all-optical WDM networks

Granularity is a key issue in the design of an optical layer of a transport network. In fact, the choices of the number of wavelength division multipl exing channels and of the bit rate of each channel have a significant impac t on the design of the network nodes and influence both the network managem ent and the transmission performance. As a matter of fact, the selection of the channel bit rate that allows the best tradeoff to be reached is a comp lex task. In this paper, we analyze, for three different routing strategies (according to the fact that wavelength conversion is achieved in any node for all the channels, or just partially for some channels, or el en not at all, respectively), the impact of transmission performance taking into cons ideration two technologies that allow wavelength conversion to be accomplis hed, and considering three relevant transmission hierarchies: 622 Mb/s, 2.5 Gb/s, and 10 Gb/s. The analysis highlights that the transmission performan ce has to be investigated to find the best choices.