Aggregation networks: Cost comparison of WDM ring vs. double star topology

Due to the increasing demand for higher transmission capacity, originated from upcoming Triple-Play services, network operators are forced to increase the transmission capacity in the backbone and aggregation networks and drive down the costs per bit/s. Many concepts have been presented, optimizing backbone network and increasing the network capacity by introducing higher data rates or channel count. In this paper we focus on aggregation network architectures investigating appropriate architectures for the aggregation of broadband services for an incumbent European network operator. These architectures have to be cost effective and ensure high service availability. These requirements can be met by either aggregating via star topology, using several stages of Ethernet aggregation nodes, by a ring topology using cost effective optical add/drop multiplexers (OADM), or furthermore a mixture of star and ring topologies. The right choice depends on the traffic load, the traffic forecast, distribution of the traffic matrix and underlying fiber graph.