41 research outputs found

    Second IEEE/LEOS Benelux Chapter, November 26th, 1997, Eindhoven University of Technology, The Netherlands

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    Second IEEE/LEOS Benelux Chapter, November 26th, 1997, Eindhoven University of Technology, The Netherlands

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    Architectures and protocols for sub-wavelength optical networks: contributions to connectionless and connection-oriented data transport

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    La r脿pida evoluci贸 d鈥橧nternet i l鈥櫭爉plia gamma de noves aplicacions (per exemple, multim猫dia, videoconfer猫ncia, jocs en l铆nia, etc.) ha fomentat canvis revolucionaris en la manera com ens comuniquem. A m茅s, algunes d鈥檃questes aplicacions demanden grans quantitats de recursos d鈥檃mple de banda amb diversos requeriments de qualitat de servei (QoS). El desenvolupament de la multiplexaci贸 per divisi贸 de longitud d鈥檕na (WDM) en els anys noranta va fer molt rendible la disponibilitat d鈥檃mple de banda. Avui dia, les tecnologies de commutaci贸 貌ptica de circuits s贸n predominants en el nucli de la xarxa, les quals permeten la configuraci贸 de canals (lightpaths) a trav茅s de la xarxa. No obstant aix貌, la granularitat d鈥檃quests canals ocupa tota la longitud d鈥檕na, el que fa que siguin ineficients per a proveir canals de menor ample de banda (sub-longitud d鈥檕na). Segons la comunitat cient铆fica, 茅s necessari augmentar la transpar猫ncia dels protocols, aix铆 com millorar l鈥檃provisionament d鈥檃mple de banda de forma din脿mica. Per tal de fer aix貌 realitat, 茅s necessari desenvolupar noves arquitectures. La commutaci贸 貌ptica de r脿fegues i de paquets (OBS/OPS), s贸n dues de les tecnologies proposades. Aquesta tesi contribueix amb tres arquitectures de xarxa destinades a millorar el transport de dades sub-longitud d鈥檕na. En primer lloc, aprofundim en la naturalesa sense connexi贸 en OBS. En aquest cas, la xarxa incrementa el seu dinamisme a causa de les transmissions a r脿fega. A m茅s, les col路lisions entre r脿fegues degraden el rendiment de la xarxa fins i tot a c脿rregues molt baixes. Per fer front a aquestes col路lisions, es proposa un esquema de resoluci贸 de col路lisions pro actiu basat en un algorisme d鈥檈ncaminament i assignaci贸 de longitud d鈥檕na (RWA) que balanceja de forma autom脿tica i distribu茂da la c脿rrega en la xarxa. En aquest protocol, el RWA i la transmissi贸 de r脿fegues es basen en l鈥檈xplotaci贸 i exploraci贸 de regles de commutaci贸 que incorporen informaci贸 sobre contencions i encaminament. Per donar suport a aquesta arquitectura, s鈥檜tilitzen dos tipus de paquets de control per a l鈥檈ncaminament de les r脿fegues i l鈥檃ctualitzaci贸 de les regles de commutaci贸, respectivament. Per analitzar els beneficis del nou algorisme, s鈥檜tilitzen quatre topologies de xarxa diferents. Els resultats indiquen que el m猫tode proposat millora en diferents marges la resta d鈥檃lgorismes RWA en funci贸 de la topologia i sense penalitzar altres par脿metres com el retard extrem a extrem. La segona contribuci贸 proposa una arquitectura h铆brida sense i orientada a connexi贸 sobre la base d鈥檜n protocol de control d鈥檃cc茅s al medi (MAC) per a xarxes OBS (DAOBS). El MAC ofereix dos m猫todes d鈥檃cc茅s: arbitratge de cua (QA) per a la transmissi贸 de r脿fegues sense connexi贸, i pre-arbitratge (PA) per serveis TDM orientats a connexi贸. Aquesta arquitectura permet una 脿mplia gamma d鈥檃plicacions sensibles al retard i al bloqueig. Els resultats avaluats a trav茅s de simulacions mostren que en l鈥檃cc茅s QA, les r脿fegues de m茅s alta prioritat tenen garantides zero p猫rdues i lat猫ncies d鈥檃cc茅s molt baixes. Pel que fa a l鈥檃cc茅s PA, es reporta que la duplicaci贸 de la c脿rrega TDM augmenta en m茅s d鈥檜n ordre la probabilitat de bloqueig, per貌 sense afectar en la mateixa mesura les r脿fegues sense connexi贸. En aquest cap铆tol tamb茅 es tracten dos dels problemes relacionats amb l鈥檃rquitectura DAOBS i el seu funcionament. En primer lloc, es proposa un model matem脿tic per aproximar el retard d鈥檃cc茅s inferior i superior com a conseq眉猫ncia de l鈥檃cc茅s QA. En segon lloc, es formula matem脿ticament la generaci贸 i optimitzaci贸 de les topologies virtuals que suporten el protocol per a l鈥檈scenari amb tr脿fic est脿tic. Finalment, l鈥櫭簂tima contribuci贸 explora els beneficis d鈥檜na arquitectura de xarxa 貌ptica per temps compartit (TSON) basada en elements de c脿lcul de camins (PCE) centralitzats per tal d鈥檈vitar col路lisions en la xarxa. Aquesta arquitectura permet garantir l鈥檃provisionament orientat a connexi贸 de canals sub-longitud d鈥檕na. En aquest cap铆tol proposem i simulem tres arquitectures GMPLS/PCE/TSON. A causa del enfocament centralitzat, el rendiment de la xarxa dep猫n en gran mesura de l鈥檃ssignaci贸 i aprovisionament de les connexions. Amb aquesta finalitat, es proposen diferents algorismes d鈥檃ssignaci贸 de ranures temporals i es comparen amb les corresponents formulacions de programaci贸 lineal (ILP) per al cas est脿tic. Per al cas de tr脿fic din脿mic, proposem i avaluem mitjan莽ant simulaci贸 diferents heur铆stiques. Els resultats mostren els beneficis de proporcionar flexibilitat en els dominis temporal i freq眉encial a l鈥檋ora d鈥檃ssignar les ranures temporals.The rapid evolving Internet and the broad range of new data applications (e.g., multimedia, video-conference, online gaming, etc.) is fostering revolutionary changes in the way we communicate. In addition, some of these applications demand for unprecedented amounts of bandwidth resources with diverse quality of service (QoS). The development of wavelength division multiplexing (WDM) in the 90's made very cost-effective the availability of bandwidth. Nowadays, optical circuit switching technologies are predominant in the core enabling the set up of lightpaths across the network. However, full-wavelength lightpath granularity is too coarse, which results to be inefficient for provisioning sub-wavelength channels. As remarked by the research community, an open issue in optical networking is increasing the protocol transparency as well as provisioning true dynamic bandwidth allocation at the network level. To this end, new architectures are required. Optical burst/packet switching (OBS/OPS) are two such proposed technologies under investigation. This thesis contributes with three network architectures which aim at improving the sub-wavelength data transport from different perspectives. First, we gain insight into the connectionless nature of OBS. Here, the network dynamics are increased due to the short-lived burst transmissions. Moreover, burst contentions degrade the performance even at very low loads. To cope with them, we propose a proactive resolution scheme by means of a distributed auto load-balancing routing and wavelength assignment (RWA) algorithm for wavelength-continuity constraint networks. In this protocol, the RWA and burst forwarding is based on the exploitation and exploration of switching rule concentration values that incorporate contention and forwarding desirability information. To support such architecture, forward and backward control packets are used in the burst forwarding and updating rules, respectively. In order to analyze the benefits of the new algorithm, four different network topologies are used. Results indicate that the proposed method outperforms the rest of tested RWA algorithms at various margins depending on the topology without penalizing other parameters such as end-to-end delay. The second contribution proposes a hybrid connectionless and connection-oriented architecture based on a medium access control (MAC) protocol for OBS networks (DAOBS). The MAC provides two main access mechanisms: queue arbitrated (QA) for connectionless bursts and pre-arbitrated (PA) for TDM connection-oriented services. Such an architecture allows for a broad range of delay-sensitive applications or guaranteed services. Results evaluated through simulations show that in the QA access mode highest priority bursts are guaranteed zero losses and very low access latencies. Regarding the PA mode, we report that doubling the offered TDM traffic load increases in more than one order their connection blocking, slightly affecting the blocking of other connectionless bursts. In this chapter, we also tackle two of the issues related with the DAOBS architecture and its operation. Firstly, we model mathematically the lower and upper approximations of the access delay as a consequence of the connectionless queue arbitrated access. Secondly, we formulate the generation of the virtual light-tree overlay topology for the static traffic case.Postprint (published version

    Control plane routing in photonic networks

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    The work described in the thesis investigates the features of control plane functionality for routing wavelength paths to serve a set of sub-wavelength demands. The work takes account of routing problems only found in physical network layers, notably analogue transmission impairments. Much work exists on routing connections for dynamic Wavelength-Routed Optical Networks (WRON) and to demonstrate their advantages over static photonic networks. However, the question of how agile the WRON should be has not been addressed quantitatively. A categorization of switching speeds is extended, and compared with the reasons for requiring network agility. The increase of effective network capacity achieved with increased agility is quantified through new simulations. It is demonstrated that this benefit only occurs within a certain window of network fill; achievement of significant gain from a more-agile network may be prevented by the operator鈥檚 chosen tolerable blocking probability. The Wavelength Path Sharing (WPS) scheme uses semi-static wavelengths to form unidirectional photonic shared buses, reducing the need for photonic agility. Making WPS more practical, novel improved routing algorithms are proposed and evaluated for both execution time and performance, offering significant benefit in speed at modest cost in efficiency. Photonic viability is the question of whether a path that the control plane can configure will work with an acceptable bit error rate (BER) despite the physical transmission impairments encountered. It is shown that, although there is no single approach that is simple, quick to execute and generally applicable at this time, under stated conditions approximations may be made to achieve a general solution that will be fast enough to enable some applications of agility. The presented algorithms, analysis of optimal network agility and viability assessment approaches can be applied in the analysis and design of future photonic control planes and network architectures

    Electro-Optical Bunch Length Measurements at the ANKA Storage Ring

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    In the framework of this thesis, a setup for single-shot bunch profile measurements was designed, successfully installed into the vacuum chamber of ANKA and commissioned. It allows single-shot bunch profile measurements with a sub-ps resolution

    Optical flow switched networks

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 253-279).In the four decades since optical fiber was introduced as a communications medium, optical networking has revolutionized the telecommunications landscape. It has enabled the Internet as we know it today, and is central to the realization of Network-Centric Warfare in the defense world. Sustained exponential growth in communications bandwidth demand, however, is requiring that the nexus of innovation in optical networking continue, in order to ensure cost-effective communications in the future. In this thesis, we present Optical Flow Switching (OFS) as a key enabler of scalable future optical networks. The general idea behind OFS-agile, end-to-end, all-optical connections-is decades old, if not as old as the field of optical networking itself. However, owing to the absence of an application for it, OFS remained an underdeveloped idea-bereft of how it could be implemented, how well it would perform, and how much it would cost relative to other architectures. The contributions of this thesis are in providing partial answers to these three broad questions. With respect to implementation, we address the physical layer design of OFS in the metro-area and access, and develop sensible scheduling algorithms for OFS communication. Our performance study comprises a comparative capacity analysis for the wide-area, as well as an analytical approximation of the throughput-delay tradeoff offered by OFS for inter-MAN communication. Lastly, with regard to the economics of OFS, we employ an approximate capital expenditure model, which enables a throughput-cost comparison of OFS with other prominent candidate architectures. Our conclusions point to the fact that OFS offers significant advantage over other architectures in economic scalability.(cont.) In particular, for sufficiently heavy traffic, OFS handles large transactions at far lower cost than other optical network architectures. In light of the increasing importance of large transactions in both commercial and defense networks, we conclude that OFS may be crucial to the future viability of optical networking.by Guy E. Weichenberg.Ph.D

    Imaging Based Beam Steering for Optical Communication and Lidar Applications

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    Optical beam steering is a key component in any application that requires dynamic (i.e. realtime control) of beam propagation through free-space. Example applications include remote sensing, spectroscopy, laser machining, targeting, Lidar, optical wireless communications (OWC) and more. The pointing control requirements for many of these applications can be met by traditional mechanical steering techniques; however, these solutions tend to be bulky, slow, expensive, power hungry and prone to mechanical failures leading to short component lifetimes. Two emerging applications, Lidar imaging and OWC, truly need improved beam-steering capabilities to flourish and support the advancement of self-driving cars or relieve the congestion in radio-frequency wireless networks, respectively. We consider the novel requirements of these applications during development of a new beam-steering technology. We introduce imaging-based beam steering (IBBS) that uses an imaging transform between spatial and directional domains to implement a new method of electronic beam-steering. We introduce this concept while focusing on transmitters (Tx) for OWC but the pointing control mechanism is bi-directional supporting both transmit and receive functionality, even out of the same aperture; likewise, features that make this solution compelling for OWC are also great for Lidar imaging. In IBBS, an array of high-speed sources are positioned at the focal plane of a lens and the lens passively collects, collimates and steers the beam into a conjugate direction. Steering is accomplished by selecting which source to use for an OWC link. This gives a coarse, pixelated beam-steering control that is well-suited for short-range OWC such as indoor communications and we present a prototype bulb for this application. Notably, multiple sources can be utilized at once with each steered into its conjugate directions and this presents the first beam-steering technology that supports multiple beams out of a single aperture; this feature uniquely supports multiplexed communications and fast, high-resolution Lidar imaging

    Laser Pulses

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    This book discusses aspects of laser pulses generation, characterization, and practical applications. Some new achievements in theory, experiments, and design are demonstrated. The introductive chapter shortly overviews the physical principles of pulsed lasers operation with pulse durations from seconds to yoctoseconds. A theory of mode-locking, based on the optical noise concept, is discussed. With this approximation, all paradoxes of ultrashort laser pulse formation have been explained. The book includes examples of very delicate laser operation in biomedical areas and extremely high power systems used for material processing and water purification. We hope this book will be useful for engineers and managers, for professors and students, and for those who are interested in laser science and technologies
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