Hybrid Wavelength Switched-TDMA High Port Count All-Optical Data Centre Switch

The physical layer, data plane design of an all-optical network switch capable of scaling to 1024 ports at 25 Gb/s per port is presented and experimentally evaluated. Fast tuning DSDBR lasers modulated with line-coded bipolar data allow combined wavelength switching and TDMA to provide packet switch-like functionality with over 2 Tb/s of total switch bandwidth. A passive fibre star coupler core with high sensitivity, DSP-free coherent receivers creates a low complexity, easily upgradeable building block for data centre networks

Parallel Star-coupler OCS Architectures using Distributed Hardware Schedulers

WDM/TDM star-coupler architectures have been proposed for building high-radix optical switches to enhance data centre network scalability. Here we propose a 1000-server star coupler network, which uses parallel OCS sub-stars to scale the network capacity to 256 Tbps. The harmony of distributed ns-timescale hardware schedulers and parallel OCS resource management achieves a throughput of 82.5% (200 Tbps) while incurring an average latency of 9.6 µs at 100% network load

Optical Switching for Scalable Data Centre Networks

This thesis explores the use of wavelength tuneable transmitters and control systems within the context of scalable, optically switched data centre networks. Modern data centres require innovative networking solutions to meet their growing power, bandwidth, and scalability requirements. Wavelength routed optical burst switching (WROBS) can meet these demands by applying agile wavelength tuneable transmitters at the edge of a passive network fabric. Through experimental investigation of an example WROBS network, the transmitter is shown to determine system performance, and must support ultra-fast switching as well as power efficient transmission. This thesis describes an intelligent optical transmitter capable of wideband sub-nanosecond wavelength switching and low-loss modulation. A regression optimiser is introduced that applies frequency-domain feedback to automatically enable fast tuneable laser reconfiguration. Through simulation and experiment, the optimised laser is shown to support 122×50 GHz channels, switching in less than 10 ns. The laser is deployed as a component within a new wavelength tuneable source (WTS) composed of two time-interleaved tuneable lasers and two semiconductor optical amplifiers. Switching over 6.05 THz is demonstrated, with stable switch times of 547 ps, a record result. The WTS scales well in terms of chip-space and bandwidth, constituting the first demonstration of scalable, sub-nanosecond optical switching. The power efficiency of the intelligent optical transmitter is further improved by introduction of a novel low-loss split-carrier modulator. The design is evaluated using 112 Gb/s/λ intensity modulated, direct-detection signals and a single-ended photodiode receiver. The split-carrier transmitter is shown to achieve hard decision forward error correction ready performance after 2 km of transmission using a laser output power of just 0 dBm; a 5.2 dB improvement over the conventional transmitter. The results achieved in the course of this research allow for ultra-fast, wideband, intelligent optical transmitters that can be applied in the design of all-optical data centres for power efficient, scalable networking

A High Speed Hardware Scheduler for 1000-port Optical Packet Switches to Enable Scalable Data Centers

Meeting the exponential increase in the global demand for bandwidth has become a major concern for today's data centers. The scalability of any data center is defined by the maximum capacity and port count of the switching devices it employs, limited by total pin bandwidth on current electronic switch ASICs. Optical switches can provide higher capacity and port counts, and hence, can be used to transform data center scalability. We have recently demonstrated a 1000-port star-coupler based wavelength division multiplexed (WDM) and time division multiplexed (TDM) optical switch architecture offering a bandwidth of 32 Tbit/s with the use of fast wavelength-tunable transmitters and high-sensitivity coherent receivers. However, the major challenge in deploying such an optical switch to replace current electronic switches lies in designing and implementing a scalable scheduler capable of operating on packet timescales. In this paper, we present a pipelined and highly parallel electronic scheduler that configures the high-radix (1000-port) optical packet switch. The scheduler can process requests from 1000 nodes and allocate timeslots across 320 wavelength channels and 4000 wavelength-tunable transceivers within a time constraint of 1μs. Using the Opencell NanGate 45nm standard cell library, we show that the complete 1000-port parallel scheduler algorithm occupies a circuit area of 52.7mm2, 4-8x smaller than that of a high-performance switch ASIC, with a clock period of less than 8ns, enabling 138 scheduling iterations to be performed in 1μs. The performance of the scheduling algorithm is evaluated in comparison to maximal matching from graph theory and conventional software-based wavelength allocation heuristics. The parallel hardware scheduler is shown to achieve similar matching performance and network throughput while being orders of magnitude faster

Reconfigurable optical star network architecture for multicast media production data centres

Passive optical star networks have attractive properties for multicast traffic in data centres, but are limited in transmission bandwidth per node due to sharing a finite total throughput capacity. By adding reconfigurable switching elements to the core of an optical star topology, simulations show that the expected transmission rate per node can be increased by 26–40% (at 90% and 70% network load respectively). The proposed architecture shows no loss of multicast functionality compared to a single passive optical star, and only 7.1% increase in power consumption. Network throughput is shown to be highly dependent on the network traffic pattern, with simulations of multicast zonal media production traffic showing 6 times greater throughput than random or hotspot traffic models

Dynamic Optical Networks for Data Centres and Media Production

This thesis explores all-optical networks for data centres, with a particular focus on network designs for live media production. A design for an all-optical data centre network is presented, with experimental verification of the feasibility of the network data plane. The design uses fast tunable (< 200 ns) lasers and coherent receivers across a passive optical star coupler core, forming a network capable of reaching over 1000 nodes. Experimental transmission of 25 Gb/s data across the network core, with combined wavelength switching and time division multiplexing (WS-TDM), is demonstrated. Enhancements to laser tuning time via current pre-emphasis are discussed, including experimental demonstration of fast wavelength switching (< 35 ns) of a single laser between all combinations of 96 wavelengths spaced at 50 GHz over a range wider than the optical C-band. Methods of increasing the overall network throughput by using a higher complexity modulation format are also described, along with designs for line codes to enable pulse amplitude modulation across the WS-TDM network core. The construction of an optical star coupler network core is investigated, by evaluating methods of constructing large star couplers from smaller optical coupler components. By using optical circuit switches to rearrange star coupler connectivity, the network can be partitioned, creating independent reserves of bandwidth and resulting in increased overall network throughput. Several topologies for constructing a star from optical couplers are compared, and algorithms for optimum construction methods are presented. All of the designs target strict criteria for the flexible and dynamic creation of multicast groups, which will enable future live media production workflows in data centres. The data throughput performance of the network designs is simulated under synthetic and practical media production traffic scenarios, showing improved throughput when reconfigurable star couplers are used compared to a single large star. An energy consumption evaluation shows reduced network power consumption compared to incumbent and other proposed data centre network technologies

Application of advanced on-board processing concepts to future satellite communications systems

An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development

Customer premise service study for 30/20 GHz satellite system

Satellite systems in which the space segment operates in the 30/20 GHz frequency band are defined and compared as to their potential for providing various types of communications services to customer premises and the economic and technical feasibility of doing so. Technical tasks performed include: market postulation, definition of the ground segment, definition of the space segment, definition of the integrated satellite system, service costs for satellite systems, sensitivity analysis, and critical technology. Based on an analysis of market data, a sufficiently large market for services is projected so as to make the system economically viable. A large market, and hence a high capacity satellite system, is found to be necessary to minimize service costs, i.e., economy of scale is found to hold. The wide bandwidth expected to be available in the 30/20 GHz band, along with frequency reuse which further increases the effective system bandwidth, makes possible the high capacity system. Extensive ground networking is required in most systems to both connect users into the system and to interconnect Earth stations to provide spatial diversity. Earth station spatial diversity is found to be a cost effective means of compensating the large fading encountered in the 30/20 GHz operating band

On-board processing for future satellite communications systems: Satellite-Routed FDMA

A frequency division multiple access (FDMA) 30/20 GHz satellite communications architecture without on-board baseband processing is investigated. Conceptual system designs are suggested for domestic traffic models totaling 4 Gb/s of customer premises service (CPS) traffic and 6 Gb/s of trunking traffic. Emphasis is given to the CPS portion of the system which includes thousands of earth terminals with digital traffic ranging from a single 64 kb/s voice channel to hundreds of channels of voice, data, and video with an aggregate data rate of 33 Mb/s. A unique regional design concept that effectively smooths the non-uniform traffic distribution and greatly simplifies the satellite design is employed. The satellite antenna system forms thirty-two 0.33 deg beam on both the uplinks and the downlinks in one design. In another design matched to a traffic model with more dispersed users, there are twenty-four 0.33 deg beams and twenty-one 0.7 deg beams. Detailed system design techniques show that a single satellite producing approximately 5 kW of dc power is capable of handling at least 75% of the postulated traffic. A detailed cost model of the ground segment and estimated system costs based on current information from manufacturers are presented

Towards a Network Marketplace in a Cloud

Abstract Virtually all public clouds today are run by single providers, and this creates near-monopolies, inefficient markets, and hinders innovation at the infrastructure level. There are current proposals to change this, by creating open architectures that allow providers of computing and storage resources to compete for tenant services at multiple levels, all the way down to the bare metal. Networking, however, is not part of this, and is viewed as a commodity much like power or cooling. In this paper we borrow ideas from the Internet architecture, and propose to structure the cloud datacenter network as a marketplace where multiple service providers can offer connectivity services to tenants. Our marketplace, NetEx, divides the network into independently managed pods of resources, interconnected with multiple providers through special programmable switches that play a role analogous to that of an IXP. We demonstrate the feasibility of such an architecture by a prototype in Mininet, and argue that this can be a way to provide innovation, competition, and efficiency in future cloud datacenter networks