A Comparison of Bit-Parallel and Bit-Serial Architectures for WDM Networks

Wavelength division multiplexing (WDM) is emerging as a viable solution to reduce the electronic processing bottleneck in very high-speed optical networks. A set of parallel and independent channels are created on a single fiber using this technique. Parallel communication utilizing the WDM channels may be accomplished in two ways: (i) bit serial, where each source-destination pair communicates using one wavelength and data are sent serially on this wavelength; and (ii) bit parallel, where each source-destination pair communicates using a subset of channels and data are sent in multiple-bit words. Three architectures are studied in the paper: single-hop bit-serial star, single-hop bit-parallel star, and multi-hop bit-parallel shufflenet. The objective of this paper is to evaluate these architectures with respect to average packet delay, network utilization, and link throughput. It is shown that the Shufflenet offers the lowest latency but suffers from high cost and low link throughput. The star topology with bit-parallel access offers lower latency than the bit-serial star, but is more expensive to implement.