Comparison of single-hop WDM architectures for local and metropolitan area networks

Single-hop WDM networks have attracted a great deal of attention as an architecture for LAN and MAN applications because of their simple operation and reduced network cost. Two kinds of passive optical devices have been considered for the hub node of single-hop WDM networks: a star coupler (SC) and an arrayed-waveguide grating (AWG). In particular, AWG-based single-hop WDM networks can achieve high throughput with reduced cost because of the periodic wavelength-routing property of the AWG. Unfortu- nately, scalability is a significant problem in an AWG-based single-hop WDM network because the number of transceivers required at each node is equal to the total number of nodes. This problem can be solved by installing optical couplers between the AWG and the nodes and by aggregating multiple nodes before connecting them to the AWG. In this case, however, packet collisions at the couplers will significantly increase the packet delay like in the SC-based single-hop WDM networks. Therefore, we have proposed a novel AWG-based single-hop WDM network in which an autonomic collision avoidance mechanism is introduced in the couplers. In this paper, we describe the optimum network design methods, and numerically compare five single-hop WDM architectures, SC, SCCA, AWG, AWG-CP, and AWG-CCA networks, to determine which network architecture is most desirable for the LAN environment and which for the MAN environment. We conclude that the AWG-CCA network has the smallest cost when the network scale is large in both LANs and MANs, the SC or SCCA networks have the smallest cost when applied to small-scale LANs, and the AWG network has the smallest cost in small-scale MANs.