Traffic grooming in WDM optical packet rings

The present paper considers a WDM optical packet ring in which multiple wavelengths are operated in a synchronous manner. This architecture attempts to blend packet switching techniques with optical transparency in order to offer a flexible MAN architecture able to accommodate large amounts of traffic demands. This architecture also performs traffic ldquogroomingrdquo (aggregation between different flows) but does not necessitate Optical-Electrical-Optical conversion in transit nodes. In each time slot, a station can send a single packet, selecting the wavelength on a per-slot basis. Once inserted on the ring, the packet is transmitted transparently to its destination. We consider 2 cases regarding receivers: in the non-WDM case, a station can only receive packets on a single wavelength whereas in the second case, a station can receive packets on all the wavelengths used in the network. In both cases, wavelengths can be shared between the stations. We address both network dimensioning and network capacity issues. The use of optical packet switching is first shown to greatly simplify the network configuration compared to any circuit-switched solution. We also show that with WDM receivers, a simple strategy of load balancing on all the wavelengths used in the network allows to increase the capacity of the network, with the same number of wavelengths, or even allows to dimension the ring with a smaller number of wavelengths. This shows that, in terms of traffic grooming, the system under study behaves similarly to non-transparent optical packet ring architectures that rely on Optical-Electrical-Optical conversion in transit nodes. On the other hand, it is expected to outperform those architectures in terms of node complexity and power consumption.