Upgradable Photonic Slot Routing Architecture
The capacity offered by the B-PSR network is expected to be more than adequate for the near future. Nevertheless, with traffic continuing to grow, there will be a need to increase the network capacity at some point in time. One way to increase the network capacity is by increasing the number of wavelengths in the system (see Figure 3.14). Due to their wavelength-insensitivity, switching nodes do not need any modification in order to increase the number of wavelengths.1 Assuming that the capacity increase obtained in this way cannot cope with the traffic growth, the network can also be upgraded by adding fiber optic links between switching nodes, where needed. If no dark fiber is available, new cables have to be put in place. In addition, the number of input and output ports of the switching nodes involved need to be increased. The extremely high cost of this upgrade may be prohibitive. An alternative solution is explored in this chapter, which entails upgrading selected switching nodes to provide a more efficient switching technique. An upgraded node, labeled Individual Wavelength Switching (IWS) node, is able to switch data flows on each wavelength individually and independently from the data flows on the other wavelengths. Since IWS nodes will be more complex than PSR nodes, in the optical part as well as in the electronic control, they are expected to be more costly than the latter. In a mixed PSR-IWS network, a trade-off can thus be made between network capacity and cost. We will call such a mixed PSR-IWS network anUpgradable Photonic Slot Routingnetwork, or U-PSR network for short.
KeywordsTime Slot Network Capacity Frame Length Wavelength Channel Switching Node
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