A Study on Multifiber WDM Network Architecture

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In our study, we consider a design principle of metro core ring, where traffic volume far exceeds the capacity of a single WDM fiber, and thus multiple fibers are required. Some people may use multiple WDM fibers and ultra high-capacity routers in every core node, although they know the primitive design is very expensive due to OEO conversion and inflated router capacity needed at every node. Some advanced people will prefer multiple WDM ring networks in a stack. However, they also find that many OADMs are necessary in every node. As a consequence, we see that no conventional design principle gives a cost-effective solution for high-capacity metro WDM core networks.We believe that the multifiber WDM networks (MWN), which has been proposed by the authors, offer a new opportunity. However, MWNs require a more number of fibers than that of those two designs, while MWNs need simple and economic OADMs. In our study, we developed a basic design concept of the bidirectional multifiber WDM networks for the first time. We showed that bidirectional transmission techniques can halve the number of fibers necessary for multifiber WDM ring networks. Our design uses no WDM interleaver unlike conventional bidirectional techniques. Instead, we used two identical sets of wavelengths for opposite directions on a single fiber, which gives the best possible performance, but has long been believed to be impractical.We theoretically analyzed the effect of Rayleigh back scattering noise. Our numerical analysis showed that optical power penalty due to Rayleigh backscattering can be reduced less than 1 dB with simple edge filters. We also investigated some advanced design alternatives. We believe that there is no feasible bidirectional design using two identical sets of wavelengths ever before. Finally, we'd like to stress that the results make multifiber WDM networks more attractive for high-capacity WDM networks for metro areas