49 research outputs found

    Optical Switching for Scalable Data Centre Networks

    Get PDF
    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

    Advances in Optical Amplifiers

    Get PDF
    Optical amplifiers play a central role in all categories of fibre communications systems and networks. By compensating for the losses exerted by the transmission medium and the components through which the signals pass, they reduce the need for expensive and slow optical-electrical-optical conversion. The photonic gain media, which are normally based on glass- or semiconductor-based waveguides, can amplify many high speed wavelength division multiplexed channels simultaneously. Recent research has also concentrated on wavelength conversion, switching, demultiplexing in the time domain and other enhanced functions. Advances in Optical Amplifiers presents up to date results on amplifier performance, along with explanations of their relevance, from leading researchers in the field. Its chapters cover amplifiers based on rare earth doped fibres and waveguides, stimulated Raman scattering, nonlinear parametric processes and semiconductor media. Wavelength conversion and other enhanced signal processing functions are also considered in depth. This book is targeted at research, development and design engineers from teams in manufacturing industry, academia and telecommunications service operators

    Waveguide acousto-optical modulators for integrated quantum photonics

    Get PDF
    En el trabajo presentado se desarrollaron dispositivos de fotónica cuántica integrada que buscan avanzar conceptos prácticos y de aplicación universal en su área de tecnología. Se presentan interruptores ópticos aprovechando la modulación acusto-optica posible en la plataforma de material de (Al,Ga)As para crear diseños robustos, compactos y con modulaciones rápidas mejorando tecnología de telecomunicaciones de estado de arte. Para aquello el desarrollo completo abarcando la modelación, el diseño y la calculación y simulación de los dispositivos se explica en amplio detalle. Por la parte experimental se demuestran la fabricación y la medición compleja de los dispositivos. Por último el extenso análisis e interpretación de los datos experimentales demuestra el funcionamiento efectivo de las muestras. Los dispositivos investigados se basan en diseños compactos del tipo de interferómetro Mach-Zehnder que se puede utilizar a base de acopladores de interferencia multimodo (MMI). Usando transductores interdigitados (IDT) para crear ondas acústicas con frecuencias e intensidades determinadas el flujo de luz por el circuito óptico puede ser controlado en tiempo real. Entre los dispositivos investigados se desarrolló un complejo y dinámicamente modulable circuito de fotónica cuántica integrada a base de puntos cuánticos. Los experimentos realizados con el dispositivo suponen un gran paso adelante para su campo de investigación ya que es la primera vez que se mostró la modulación espectral de fotones únicos que se acoplan a las guías de onda, se propagan por distancias largas y encima se dejan guiar por el circuito de manera determinada. Con los conceptos demostrados se abren muchas puertas hacia dispositivos más complejos y con aplicaciones prácticas en campos como la computación cuántica y el procesamiento de información cuántica. Su funcionamiento puede ser adaptado fácilmente a otras plataformas de material, tales como el silicio o fosfuro de indio y se dejan juntar con otros tipos de modulación típico en telecomunicaciones como la interacción termo-óptica y electro-óptica.The (quantum) optical waveguide structures presented in this thesis are novel and versatile devices for future integrated photonic circuits that need to be small, cost-effective, robust and that can be fabricated with high production tolerances in place. This work seeks to exploit the interaction between light and sound waves in dimensions down to the quantum emitter level in order to lead the way toward highly dynamical telecommunication systems. To this end, acoustically tuned optical switches on a monolithical (Al,Ga)As platform that enable robust, compact and fast responding systems improving on recently demonstrated technology are analysed. The presented work covers the full development process of modelling, designing, calculating and simulating the devices from the ground up. The detailed experimental sections show the fabrication steps as well as the complex measurements undertaken to characterise the samples. A comprehensive analysis and interpretation of the achieved experimental data brings the thorough study of the devices to a conclusive end. The devices’ fundamental functionality relies on multimode interference based Mach-Zehnder interferometer switches. The devices are tuned by surface acoustic wave (SAW) beams working in the low GHz range. In this way, the refractive index profile over a narrow modulation region can be modulated and thus real time control over the optical switching behaviour is gained via the applied SAW intensity and frequency. Using SAWs allows for a non-destructive manipulation of such a system’s optical responses. The here presented device category involves integrated quantum photonics wherein single photon sources are combined with complex and dynamic optical circuitry. Therefore, the acoustic modulation of the signal emitters and photons plays a key role for the realisation of state-of-the-art chip-based integrated photonic circuits. Novel acoustically tuned optical switches on an (Al,Ga)As platform that enable low-loss, small footprint and high signal fidelity systems using the on-chip generation of single photons are presented. As such a light source single quantum dots embedded in the waveguide structures are used. Modulation of the quantum dots by a surface acoustic wave grants control over the photon emission wavelength. The integrated optical circuit through which the photons travel consists of a Mach-Zehnder interferometer based on two multimode interference devices which are dynamically tuned by a second surface acoustic wave. The photons can be routed between multiple outputs by controlling the intensity and frequency of this surface acoustic wave. With the presented results it is shown how these complex modulation mechanisms can be combined and how they can be readily applied for wavelength modulation and fast signal routing in future quantum optical networking systems for secure quantum communication

    Control Plane Hardware Design for Optical Packet Switched Data Centre Networks

    Get PDF
    Optical packet switching for intra-data centre networks is key to addressing traffic requirements. Photonic integration and wavelength division multiplexing (WDM) can overcome bandwidth limits in switching systems. A promising technology to build a nanosecond-reconfigurable photonic-integrated switch, compatible with WDM, is the semiconductor optical amplifier (SOA). SOAs are typically used as gating elements in a broadcast-and-select (B\&S) configuration, to build an optical crossbar switch. For larger-size switching, a three-stage Clos network, based on crossbar nodes, is a viable architecture. However, the design of the switch control plane, is one of the barriers to packet switching; it should run on packet timescales, which becomes increasingly challenging as line rates get higher. The scheduler, used for the allocation of switch paths, limits control clock speed. To this end, the research contribution was the design of highly parallel hardware schedulers for crossbar and Clos network switches. On a field-programmable gate array (FPGA), the minimum scheduler clock period achieved was 5.0~ns and 5.4~ns, for a 32-port crossbar and Clos switch, respectively. By using parallel path allocation modules, one per Clos node, a minimum clock period of 7.0~ns was achieved, for a 256-port switch. For scheduler application-specific integrated circuit (ASIC) synthesis, this reduces to 2.0~ns; a record result enabling scalable packet switching. Furthermore, the control plane was demonstrated experimentally. Moreover, a cycle-accurate network emulator was developed to evaluate switch performance. Results showed a switch saturation throughput at a traffic load 60\% of capacity, with sub-microsecond packet latency, for a 256-port Clos switch, outperforming state-of-the-art optical packet switches

    Optical Technologies and Control Methods for Scalable Data Centre Networks

    Get PDF
    Attributing to the increasing adoption of cloud services, video services and associated machine learning applications, the traffic demand inside data centers is increasing exponentially, which necessitates an innovated networking infrastructure with high scalability and cost-efficiency. As a promising candidate to provide high capacity, low latency, cost-effective and scalable interconnections, optical technologies have been introduced to data center networks (DCNs) for approximately a decade. To further improve the DCN performance to meet the increasing traffic demand by using photonic technologies, two current trends are a)increasing the bandwidth density of the transmission links and b) maximizing IT and network resources utilization through disaggregated topologies and architectures. Therefore, this PhD thesis focuses on introducing and applying advanced and efficient technologies in these two fields to DCNs to improve their performance. On the one hand, at the link level, since the traditional single-mode fiber (SMF) solutions based on wavelength division multiplexing (WDM) over C+L band may fall short in satisfying the capacity, front panel density, power consumption, and cost requirements of high-performance DCNs, a space division multiplexing (SDM) based DCN using homogeneous multi-core fibers (MCFs) is proposed.With the exploited bi-directional model and proposed spectrum allocation algorithms, the proposed DCN shows great benefits over the SMF solution in terms of network capacity and spatial efficiency. In the meanwhile, it is found that the inter-core crosstalk (IC-XT) between the adjacent cores inside the MCF is dynamic rather than static, therefore, the behaviour of the IC-XT is experimentally investigated under different transmission conditions. On the other hand, an optically disaggregated DCN is developed and to ensure the performance of it, different architectures, topologies, resource routing and allocation algorithms are proposed and compared. Compared to the traditional server-based DCN, the resource utilization, scalability and the cost-efficiency are significantly improved

    Parallel Modular Scheduler Design for Clos Switches in Optical Data Center Networks

    Get PDF
    As data centers enter the exascale computing era, the traffic exchanged between internal network nodes, increases exponentially. Optical networking is an attractive solution to deliver the high capacity, low latency, and scalable interconnection needed. Among other switching methods, packet switching is particularly interesting as it can be widely deployed in the network to handle rapidly-changing traffic of arbitrary size. Nanosecond-reconfigurable photonic integrated switch fabrics, built as multi-stage architectures such as the Clos network, are key enablers to scalable packet switching. However, the accompanying control plane needs to also operate on packet timescales. Designing a central scheduler, to control an optical packet switch in nanoseconds, presents a challenge especially as the switch size increases. To this end, we present a highly-parallel, modular scheduler design for Clos switches along with a proposed routing scheme to enable nanosecond scalable scheduling. We synthesize our scheduler as an application-specific integrated circuit (ASIC) and demonstrate scaling to a 256 × 256 size with an ultra-low scheduling delay of only 6.0 ns. In a cycle-accurate rack-scale network emulation, for this switch size, we show a minimum end-to-end latency of 30.8 ns and maintain nanosecond average latency up to 80% of input traffic load. We achieve zero packet loss and short-tailed packet latency distributions for all traffic loads and switch sizes. Our work is compared to state-of-the-art optical switches, in terms of scheduling delay, packet latency, and switch throughput

    Dynamic Optical Networks for Data Centres and Media Production

    Get PDF
    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
    corecore