Hybrid Optical and Electrical Network Flows Scheduling in Cloud Data Centres

Hybrid intra-data centre networks, with optical and electrical capabilities, are attracting research interest in recent years. This is attributed to the emergence of new bandwidth greedy applications and novel computing paradigms. A key decision to make in networks of this type is the selection and placement of suitable flows for switching in circuit network. Here, we propose an efficient strategy for flow selection and placement suitable for hybrid Intra-cloud data centre networks. We further present techniques for investigating bottlenecks in a packet networks and for the selection of flows to switch in circuit network. The bottleneck technique is verified on a Software Defined Network (SDN) testbed. We also implemented the techniques presented here in a scalable simulation experiment to investigate the impact of flow selection on network performance. Results obtained from scalable simulation experiment indicate a considerable improvement on average throughput, lower configuration delay, and stability of offloaded flowsComment: 17 pages 11 figures, Journal pape

Plug&play fibre-coupled 73 kHz single-photon source operating in the telecom O-band

A user-friendly fibre-coupled single-photon source operating at telecom wavelengths is a key component of photonic quantum networks providing long-haul ultra-secure data exchange. To take full advantage of quantum-mechanical data protection and to maximize the transmission rate and distance, a true quantum source providing single-photons on demand is highly desirable. We tackle this great challenge by developing a ready to use semiconductor quantum dot (QD)-based device that launches single photons at a wavelength of 1.3 um directly into a single-mode optical fibre. In our approach the QD is deterministically integrated into a nanophotonic structure to ensure efficient on-chip coupling into a fibre. The whole arrangement is integrated into a 19" compatible housing to enable stand-alone operation by cooling via a compact Stirling cryocooler. The realized source delivers single photons with multiphoton events probability as low as 0.15 and single-photon emission rate up to 73 kHz into a standard telecom single-mode fibre.Comment: 20 pages, 3 figure

BER performance analysis of 100 and 200 Gbit/s all-optical OTDM node using symmetric Mach-Zehnder switches

New insight to the feasibility of all-optical ultra speed switching up to 200 Gb/s. The technique will reduce the dependency and bottleneck on the electronic-to-optical-to-electronic conversion. Current conversion speed is up to 40 Gb/s in laboratories. The novel clock extraction technique proposed shows the potential of an all-optical switch. The research results are directly relevant to the access technology where optical fibre and RF is competing to be the solution. The growing demands of bandwidth will exceed RF capability while the optical fibre will be the optimum solution. A PhD project (Le-Minh) funded by the University Studentship, completed in 2007

Relativistic quantum key distribution system with one-way quantum communication

Unambiguous state discrimination (USD) is one of the major obstacles for practical quantum key distribution (QKD). Often overlooked, it allows efficient eavesdropping in majority of practical systems, provided the overall channel loss is above a certain threshold. Thus, to remain secure all such systems must not only monitor the actual loss, but also possess a comprehensive information on the safe 'loss vs. BER' levels, which is often well beyond currently known security analyses. The more advanced the protocol the tougher it becomes to find and prove corresponding bounds. To get out of this vicious circle and solve the problem outright, we demonstrate a so called relativistic QKD system, which uses causality to become inherently immune to USD-based attacks. The system proves to be practical in metropolitan line-of-sight arrangements. At the same time it has a very basic structure that allows for a straightforward and comprehensive security analysis.Comment: 9 pages, 8 figure

A novel approach to quality-of-service provisioning in trusted relay Quantum Key Distribution networks

In recent years, noticeable progress has been made in the development of quantum equipment, reflected through the number of successful demonstrations of Quantum Key Distribution (QKD) technology. Although they showcase the great achievements of QKD, many practical difficulties still need to be resolved. Inspired by the significant similarity between mobile ad-hoc networks and QKD technology, we propose a novel quality of service (QoS) model including new metrics for determining the states of public and quantum channels as well as a comprehensive metric of the QKD link. We also propose a novel routing protocol to achieve high-level scalability and minimize consumption of cryptographic keys. Given the limited mobility of nodes in QKD networks, our routing protocol uses the geographical distance and calculated link states to determine the optimal route. It also benefits from a caching mechanism and detection of returning loops to provide effective forwarding while minimizing key consumption and achieving the desired utilization of network links. Simulation results are presented to demonstrate the validity and accuracy of the proposed solutions.Web of Science28118116

High speed all optical networks

An inherent problem of conventional point-to-point wide area network (WAN) architectures is that they cannot translate optical transmission bandwidth into comparable user available throughput due to the limiting electronic processing speed of the switching nodes. The first solution to wavelength division multiplexing (WDM) based WAN networks that overcomes this limitation is presented. The proposed Lightnet architecture takes into account the idiosyncrasies of WDM switching/transmission leading to an efficient and pragmatic solution. The Lightnet architecture trades the ample WDM bandwidth for a reduction in the number of processing stages and a simplification of each switching stage, leading to drastically increased effective network throughputs. The principle of the Lightnet architecture is the construction and use of virtual topology networks, embedded in the original network in the wavelength domain. For this construction Lightnets utilize the new concept of lightpaths which constitute the links of the virtual topology. Lightpaths are all-optical, multihop, paths in the network that allow data to be switched through intermediate nodes using high throughput passive optical switches. The use of the virtual topologies and the associated switching design introduce a number of new ideas, which are discussed in detail

Deflection Routing Strategies for Optical Burst Switching Networks: Contemporary Affirmation of the Recent Literature

A promising option to raising busty interchange in system communication could be Optical Burst Switched (OBS) networks among scalable and support routing effective. The routing schemes with disputation resolution got much interest, because the OBS network is buffer less in character. Because the deflection steering can use limited optical buffering or actually no buffering thus the choice or deflection routing techniques can be critical. Within this paper we investigate the affirmation of the current literature on alternate (deflection) routing strategies accessible for OBS networks

Optically-Connected Memory: Architectures and Experimental Characterizations

Growing demands on future data centers and high-performance computing systems are driving the development of processor-memory interconnects with greater performance and flexibility than can be provided by existing electronic interconnects. A redesign of the systems' memory devices and architectures will be essential to enabling high-bandwidth, low-latency, resilient, energy-efficient memory systems that can meet the challenges of exascale systems and beyond. By leveraging an optics-based approach, this thesis presents the design and implementation of an optically-connected memory system that exploits both the bandwidth density and distance-independent energy dissipation of photonic transceivers, in combination with the flexibility and scalability offered by optical networks. By replacing the electronic memory bus with an optical interconnection network, novel memory architectures can be created that are otherwise infeasible. With remote optically-connected memory nodes accessible to processors as if they are local, programming models can be designed to utilize and efficiently share greater amounts of data. Processors that would otherwise be idle, being starved for data while waiting for scarce memory resources, can instead operate at high utilizations, leading to drastic improvements in the overall system performance. This work presents a prototype optically-connected memory module and a custom processor-based optical-network-aware memory controller that communicate transparently and all-optically across an optical interconnection network. The memory modules and controller are optimized to facilitate memory accesses across the optical network using a packet-switched, circuit-switched, or hybrid packet-and-circuit-switched approach. The novel memory controller is experimentally demonstrated to be compatible with existing processor-memory access protocols, with the memory controller acting as the optics-computing interface to render the optical network transparent. Additionally, the flexibility of the optical network enables additional performance benefits including increased memory bandwidth through optical multicasting. This optically-connected architecture can further enable more resilient memory system realizations by expanding on current error dectection and correction memory protocols. The integration of optics with memory technology constitutes a critical step for both optics and computing. The scalability challenges facing main memory systems today, especially concerning bandwidth and power consumption, complement well with the strengths of optical communications-based systems. Additionally, ongoing efforts focused on developing low-cost optical components and subsystems that are suitable for computing environments may benefit from the high-volume memory market. This work therefore takes the first step in merging the areas of optics and memory, developing the necessary architectures and protocols to interface the two technologies, and demonstrating potential benefits while identifying areas for future work. Future computing systems will undoubtedly benefit from this work through the deployment of high-performance, flexible, energy-efficient optically-connected memory architectures

Electromagnetically Induced Transparency of On-demand Single Photons in a Hybrid Quantum Network

Long range quantum communication and quantum information processing require the development of light-matter interfaces for distributed quantum networks. Even though photons are ideal candidates for network links to transfer quantum information, the system of choice for the realization of quantum nodes has not been identified yet. Ideally, one strives for a hybrid network architecture, which will consist of different quantum systems, combining the strengths of each system. However, interfacing different quantum systems via photonic channels remains a major challenge because a detailed understanding of the underlying light-matter interaction is missing. Here, we show the coherent manipulation of single photons generated on-demand from a semiconductor quantum dot using a rubidium vapor quantum memory, forming a hybrid quantum network. We demonstrate the engineering of the photons' temporal wave function using four-level atoms and the creation of a new type of electromagnetic induced transparency for quantum dot photons on resonance with rubidium transitions. Given the short lifetime of our quantum dot transition the observed dynamics cannot be explained in the established steady-state picture. Our results play a pivotal role in understanding quantum light-matter interactions at short time scales. These findings demonstrate a fundamental active node to construct future large-scale hybrid quantum networks.Comment: 16 pages, 5 figure

Heuristic performance model of optical buffers for variable length packets

Optical switching (optical packet switching, optical burst switching, and others) provides alternatives to the current switching in backbone networks. To switch optically, also packet buffering is to be done optically, by means of fiber delay lines (FDLs). Characteristic of the resulting optical buffer is the quantization of possible delays: Only delays equal to the length of one of the FDLs can be realized. An important design challenge is the optimization of the delay line lengths for minimal packet loss. To this end, we propose a heuristic based on two existing queueing models: one with quantization and one with impatience. Combined, these models yield an accurate performance modeling heuristic. A key advantage of this heuristic is that it translates the optical buffer problem into two well-known queueing problems, with accurate performance expressions available in the literature. This paper presents the heuristic in detail, together with several figures, comparing the heuristic's output to existing approaches, validating its high accuracy