S.P. Ferguson

Bio: S.P. Ferguson is an academic researcher from Coventry Health Care. The author has contributed to research in topics: Transmission delay & Packet switching. The author has an hindex of 1, co-authored 1 publications receiving 139 citations.

Packet loss and delay performance of feedback and feed-forward arrayed-waveguide gratings-based optical packet switches with WDM inputs-outputs

Abstract: This paper analyzes the packet loss and delay performance of an arrayed-waveguide-grating-based (AWG) optical packet switch developed within the EPSRC-funded project WASPNET (wavelength switched packet network). Two node designs are proposed based on feedback and feed-forward strategies, using sharing among multiple wavelengths to assist in contention resolution. The feedback configuration allows packet priority routing at the expense of using a larger AWG. An analytical framework has been established to compute the packet loss probability and delay under Bernoulli traffic, justified by simulation. A packet loss probability of less than 10/sup -9/ was obtained with a buffer depth per wavelength of 10 for a switch size of 16 inputs-outputs, four wavelengths per input at a uniform Bernoulli traffic load of 0.8 per wavelength. The mean delay is less than 0.5 timeslots at the same buffer depth per wavelength.

DOS: a scalable optical switch for datacenters

Abstract: This paper discusses the architecture and performance studies of Datacenter Optical Switch (DOS) designed for scalable and high-throughput interconnections within a data center. DOS exploits wavelength routing characteristics of a switch fabric based on an Arrayed Waveguide Grating Router (AWGR) that allows contention resolution in the wavelength domain. Simulation results indicate that DOS exhibits lower latency and higher throughput even at high input loads compared with electronic switches or previously proposed optical switch architectures such as OSMOSIS [4, 5] and Data Vortex [6, 7]. Such characteristics, together with very high port count on a single switch fabric make DOS attractive for data center applications where the traffic patterns are known to be bursty with high temporary peaks [13]. DOS exploits the unique characteristics of the AWGR fabric to reduce the delay and complexity of arbitration. We present a detailed analysis of DOS using a cycle-accurate network simulator. The results show that the latency of DOS is almost independent of the number of input ports and does not saturate even at very high (approx 90%) input load. Furthermore, we show that even with 2 to 4 wavelengths, the performance of DOS is significantly better than an electrical switch network based on state-of-the-art flattened butterfly topology.

The Role of Optics and Electronics in High-Capacity Routers

Abstract: This paper examines the role of optical and electronic technologies in future high-capacity routers. In particular, optical and electronic technologies for use in the key router functions of buffering and switching are compared. The comparison is based on aggressive but plausible estimates of buffer and switch performance projected out to around 2020. The analysis of buffer technologies uses a new model of power dissipation in optical-delay-line buffers using optical fiber and planar waveguides, including slow-light waveguides. Using this model together with models of storage capacity in ideal and nonideal slow-light delay lines, the power dissipation and scaling characteristics of optical and electronic buffers are compared. The author concludes that planar integrated optical buffers occupy larger chip area than electronic buffers, dissipate more power than electronic buffers, and are limited in capacity to, at most, a few IP packets. Optical fiber-based buffers have lower power dissipation but are bulky. The author also concludes that electronic buffering will remain the technology of choice in future high-capacity routers. The power dissipation of high-capacity optical and electronic cross connects for a number of cross connect architectures is compared. The author shows that optical and electronic cross connects dissipate similar power and require a similar chip area. Optical technologies show a potential for inclusion in high-capacity routers, especially as the basis for arrayed-waveguide-grating-based cross connects and as components in E/O/E interconnects. A major challenge in large cross connects, both optical and electronic, will be to efficiently manage the very large number of interconnects between chips and boards. The general conclusion is that electronic technologies are likely to remain as integral components in the signal transmission path of future high-capacity routers. There does not appear to be a compelling case for replacing electronic routers with optically transparent optical packet switches

Shared fiber delay line buffers in asynchronous optical packet switches

Abstract: Packet contention is a major issue in asynchronous optical packet switching networks. Optical buffering, which is implemented by fiber delay lines (FDLs), is fundamental to many optical switch implementations for resolving contention. Most existing optical buffering implementations are output-based and require a huge amount of FDLs as well as larger switch sizes, which impose extra cost on the overall system. In this paper, we consider a shared optical buffering architecture which can reduce the buffer size at a switch. We propose an analytical model to evaluate the packet loss probability and the average delay For shared buffers at a single switch. We then compare the performance of output buffers to shared buffers under different granularities of FDLs. We observe that, by choosing an appropriate granularity, the shared buffering scheme can significantly reduce packet loss with much smaller switch sizes and fewer FDLs than the output buffering architecture. The accuracy of the analytical model is also confirmed by extensive simulation

Integrated optical router

Abstract: An optical router integrated in an InP-based substrate bonded to a single thermo-electric cooler for packet-based networks utilizing wavelength-division multiplexing (WDM) on silica fibers. Input and output arrayed waveguide gratings (AWGs) respectively demultiplex and multiplex the WDM signals to and from multiple transmission fibers. Input and output wavelength converters are connected between the input and outputs AWGs and a switching AWG. The output converts may include a tunable laser and interferometer formed in the same substrate. The header information is preferably carried out-of-channel from the WDM data signals, either in the same fiber band or a different one. Photodetectors and laser diodes are formed in the same substrate. Fast RF electronics are formed in GaAs chips and slower electronics formed in a silicon chip are bonded to the InP wafer

A Scalable, Low-Latency, High-Throughput, Optical Interconnect Architecture Based on Arrayed Waveguide Grating Routers

Abstract: This paper proposes, simulates, and experimentally demonstrates an optical interconnect architecture for large-scale computing systems. The proposed architecture, Hierarchical Lightwave Optical Interconnect Network (H-LION), leverages wavelength routing in arrayed waveguide grating routers (AWGRs), and computing nodes (or servers) with embedded routers and wavelength-specific optical I/Os. Within the racks and clusters, the interconnect topology is hierarchical all-to-all exploiting passive AWGRs. For the intercluster communication, the proposed architecture exploits a flat and distributed Thin-CLOS topology based on AWGR-based optical switches. H-LION can scale beyond 100 000 nodes while guaranteeing up to 1.83×saving in number of inter-rack cables, and up to 1.5×saving in number of inter-rack switches, when compared with a legacy three-tier Fat Tree network. Network simulation results show a system-wide network throughput reaching as high as 90% of the total possible capacity in case of synthetic traffic with uniform random distribution. Experiments show 97% intracluster throughput for uniform random traffic, and error-free intercluster communication at 10 Gb/s.