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This paper addresses two related problems in the context of transparent optical networks. In the network design problem, the aim is to identify a set of fiber links to connect a given set of nodes. In the network upgrade problem, the aim is to identify a set of new fiber links to add to a given network topology. For a given fiber length budget, the aim in both problems is to maximize the network resilience to the simultaneous failure of its critical nodes. The resilience is evaluated by the average 2‐terminal reliability (A2TR) against a set of critical node failures and the critical nodes are the ones that minimize the A2TR of the network. So, the design/upgrade problem is a bi‐level max‐min optimization problem. Recently, a multi start greedy randomized heuristic was proposed for both problems. Here, we propose an alternative method based on a greedy deterministic algorithm and we provide computational results showing that the new method obtains better solutions. The results show that the resiliency difference between existing network topologies and the best network design solutions is very high but this difference can be significantly reduced by network upgrades with small fiber length budgets. published

In this dissertation a set of heuristic algorithms was developed, implemented and validated for the dimensioning of transparent optical networks. A generic platform was also created in order to allow the heuristics development and implementation, based on two main entities: a logical layer manager and a physical layer manager. The referred structure was designed in order to allow the test of a vast variety of heuristic algorithms. Within the scope of this dissertation were developed traffic scheduling algorithms based on the individual traffic quantity of each request. In addition, some routing, grooming and wavelength assignment algorithms were also developed. The main goal of these heuristics is is to dimension networks, while recurring to the minimum possible amount of resources, thus minimizing the CAPEX of the network, while also trying to guarantee the total traffic routing. For simplicity reasons only the case of networks without survivabilty was treated, although the platform is sufficiently generic to allow its inclusion in future work. Regarding the economic aspects, a detailed and comparative study was conducted, focusing on the networks CAPEX, in order to validate and assess the quality of the solutions provided by the heuristics developed based on the solutions given by an integer linear programming model. Finally, some conclusions and possible future work are discussed. Nesta dissertação foram desenvolvidas, implementadas e validadas heurísticas para o dimensionamento de redes óticas de transporte transparentes. Foi criada uma plataforma genérica para o desenvolvimento e a implementação das heurísticas baseada em duas entidades principais: um gestor de recursos da camada lógica e um gestor de recursos da camada física. Esta estrutura foi desenhada de modo a poder ser usada para testar uma grande variedade de heurísticas. No âmbito desta tese foram desenvolvidas heuristicas considerando o escalonamento dos pedidos baseados na quantidade de tráfego de cada pedido. Foram ainda desenvolvidos algoritmos para o encaminhamento, a atribuição de comprimentos de onda e agregação dos pedidos de tráfego. O objetivo das heurísticas passa pelo dimensionamento de uma rede, onde recorrendo-se a um mínimo possível de recursos, e portanto, minimizando o CAPEX da rede, se tenta garantir o encaminhamento total do tráfego. Por uma questão de simplificidade apenas foram consideradas redes sem sobrevivência, no entanto, a plataforma é suficientemente genérica para permitir a inclusão de sobrevivência. Tendo também em conta a referida vertente económica, foi elaborado um estudo detalhado e comparativo, tendo em foco o CAPEX da rede, com o objetivo de validar a qualidade das soluções fornecidas pelas heurísticas desenvolvidas tendo por base os valores obtidos através de um modelo baseado em programação linear inteira. Finalmente, são partilhadas e discutidas algumas conclusões e direções para o desenvolvimento de trabalho futuro. Mestrado em Engenharia Eletrónica e Telecomunicações

In this work, we assess the impact of several physical layer impairments (PLIs) on the performance of optical networks based on colorless, directionless and contentionless reconfigurable optical add/drop multiplexers (ROADMs), through Monte-Carlo simulation, and considering polarization division multiplexing 4 and 16 quadrature amplitude modulation (QAM) signals, at 28 GBaud, for 37.5 GHz optical channels. The PLIs taken into account are the amplified spontaneous emission noise, optical filtering, in-band crosstalk and nonlinear interference noise caused by Kerr effect. A detailed model of the ROADM node is built considering two typical ROADM architectures, broadcast and select (B&S) and route and select (R&S), and two different add/drop structures, multicast switches (MCSs) and wavelength selective switches (WSSs), resulting in four different ROADM node scenarios. Our results have shown that for 16QAM signals, the B&S ROADMs with WSSs-based add/drop structures is the scenario that has the best relation cost/performance, foreseeing its use in metro networks, while for 4QAM signals, the R&S ROADM with WSSs-based add/drop structure scenario allows a larger ROADM cascade at an expectable lower cost anticipating its implementation in long-haul networks.

Consider an existing Elastic Optical Network (EON) with a given topology composed by nodes and connecting fibers, each fiber with a given spectrum capacity. Consider an estimated set of demands to be supported and a routing, modulation and spectrum assignment (RMSA) policy adopted by the operator both for the regular state and for the failure states. First, we address the resilience evaluation of the EON to multiple node failures. We adopt a worst-case approach by identifying the nodes (named critical nodes) whose simultaneous failure maximally reduce the demand percentage that is supported by the network and we use this percentage as the resilience metric. Then, for the same estimated demands, the same RMSA policy and a fiber budget equal to the total fiber length of the existing network, we address the design problem aiming to determine a new EON maximizing the resilience metric imposed by its critical nodes. We use a multi-start greedy randomized method that generates multiple EONs and returns the best one, i.e., the EON with the highest resilience metric. We run the evaluation and design methods on known network topologies. The computational results let us (i) analyze the efficiency of the methods and (ii) assess how far the resilience of existing networks are from the best ones. This paper is based upon work from COST Action CA15127 (”Resilient communication services protecting end-user appli- cations from disaster-based failures – RECODIS”) supported by COST (European Cooperation in Science and Technology). The work was also supported by FCT, Portugal, through project ResNeD CENTRO-01-0145-FEDER-029312 and PhD grant SFRH/BD/132650/2017. Second and third authors were supported by FCT through projects UID/EEA/50008/2019 and UID/MAT/04106/2019, respectively. published

For a given graph representing a transparent optical network, a given weight associated to each node pair and a given positive integer c, the Critical Node Detection problem variant addressed here is the determination of the set of c nodes that, if removed from the graph, minimizes the total weight of the node pairs that remain connected. In the context of transparent optical networks, a node pair is considered connected only if the surviving network provides it with a shortest path not higher than a given positive value T representing the optical transparent reach of the network. Moreover, the length of a path depends both on the length of its links and on its number of intermediate nodes. A path-based Integer Linear Programming model is presented together with a row generation approach to solve it. We present computational results for a real-world network topology with 50 nodes and 88 links and for c=2 up to 6. The optimal results are compared with node centrality based heuristics showing that such approaches provide solutions which are far from optimal. published

International audience; Functionalizing the surface of chalcogenide films is of major interest due to the wide use of these materials in infrared integrated optics. A functionalization route via short peptides that has been already used for silicon, ZnSe and other semiconductors is applied to amorphous films of the ternary Ge-Se-Te system. The biotinylated 12-mer peptides LLADTTHHRPWT and SVSVGMKPSPRP were chosen and used to capture streptavidin. High-resolution atomic force microscopy images highlight that the 12-mer peptide LLADTTHHRPWT provides better interface layers for streptavidin molecule detection.

Consider the resilience of a network defined by the average 2-terminal reliability (A2TR) against a set of critical node failures. Consider an existing transparent optical network with a total fibre length L. The first goal of this paper is to assess the resiliency gap between the existing topology and a new network topology designed to maximize its resilience with the same fibre budget L. The resiliency gap gives us a measure of how good the resilience of existing network topologies are. Consider now that an existing network is upgraded with new links aiming to maximize its resiliency improvement with a fibre budget L'. The second goal of this paper is to assess how much the resiliency gap can be reduced between a good upgraded solution and a network topology designed to maximize its resiliency with the same fibre budget L + L'. The gap reduction gives us a measure of how close to the best resilience the upgraded solutions can get for different values of L'. To reach these goals, we first describe how the Critical Node Detection problem is defined and solved in the context of transparent optical networks. Then, we propose a multi-start greedy randomized method to generate network topologies, with a given fibre length budget, that are resilient to critical node failures. This method is also adapted to the upgrade of an existing network topology. At the end, we run the proposed methods on network topologies with public available information. The computational results show that the resiliency gap of existing topologies is significantly large but network upgrades with L' = 10%L can significantly reduce the resiliency gaps provided that such upgrades are aimed at maximizing the network resilience to multiple node failures. published

Space division multiplexing (SDM) has been proposed as the ultimate solution to address the capacity crunch of optical transport networks. The efficient utilization of SDM requires some forms of spatial integration which is expected to bring huge cost savings for the deployment of SDM-based optical networks. Spatially integrated components with different characteristics have been largely explored and demonstrated for the realization of SDM networks, including; transmission media, transceivers with sophisticated digital signal processing (DSP) units, amplifiers, and ultimately optical switching nodes which are the key elements for the realization of transparent optical networks exploiting SDM technologies. As a consequence, in contrast to the currently deployed optical networks based on standard single mode fibers (SSMF), the next generation of optical networks exploiting SDM technologies can be realized utilizing various kinds of transmission media and the other corresponding elements. However, due in part to the physical properties of different components, their complexity, and the technology limitations not all of them meet the economic feasibility and a desired level of network-wide performance. Therefore, careful analysis should be done revealing the most appropriate and cost-effective solutions. In this work, we review the recent developments and findings which pave the way for a simplified and efficient implementation of the spectrally and spatially flexible optical networks.

We review a novel, secure, highly distributed and ultra-dense fog computing infrastructure, which can be allocated at the extreme edge of a wired/wireless network for a Telecom Operator to provide multiple unified, cost-effective and new 5G services, such as Network Function Virtualization (NFV), Mobile Edge Computing (MEC), and services for third parties (e.g., smart cities, vertical industries or Internet of Things (IoT)). The distributed and programmable fog technologies are expected to strengthen the position of the Mobile Network and cloud markets; key benefits are the dynamic deployment of new distributed low-latency services. The architecture consists of three main building blocks: a) a scalable node, that is seamlessly integrated in the Telecom infrastructure; b) a controller, focused on service assurance, that is integrated in the management and orchestration architecture of the Telecom operator; and c) services running on top of the Telecom infrastructure.

Ultra Dense Wavelength Division Multiplexing (UDWDM) has been proposed for future Passive Optical Networks (PONs) to support the increase of access traffic, furnishing an improved capacity while introducing point-to-point logical connections with the Wavelength-To-The-User (WTTU) concept, enabled by low cost coherent transceivers with high sensitivity. Furthermore, considering wireless networks, a centralized processing in a Cloud-Radio Access Network (C-RAN) needs reconfigurable abilities to bring benefits to mobile systems with dynamic demands of huge bandwidth between Remote Radio Heads (RRHs) at base stations and Baseband Units (BBUs) at the central office. To achieve this goal in the access network, we propose a flexible architecture design of an UDWDM-PON, which adapts the available bandwidth to different users and classes of services and can reconfigure the connections between RRHs and BBUs. © 2018 IEEE.

In this work we consider the problem of fault localization in transparent optical networks.We attempt to localize single-link failures by utilizing statistical machine learning techniques trained on data that describe the network state upon current and past failure incidents. In particular, a Gaussian process classifier is trained on historical data extracted from the examined network, with the goal of modeling and predicting the failure probability of each link therein. To limit the set of suspect links for every failure incident, the proposed approach is complemented by the utilization of a graph-based correlation heuristic. The proposed approach is tested on a number of datasets generated for an orthogonal frequency-division multiplexing-based optical network, and demonstrates that the approach achieves a high localization accuracy (91%–99%) that is insignificantly affected as the size of the historical dataset is reduced. The approach is also compared to a conventional fault localization method that is based on the utilization of monitoring information. It is shown that the conventional method significantly increases the network cost, as measured by the number of monitoring nodes required to achieve the same accuracy as that achieved by the proposed approach. The proposed scheme can be used by service providers to reduce the network cost related to the fault localization procedure. As the approach is generic and does not depend on specific network technologies, it can be applied to different network types, e.g., fixed-grid or space-division multiplexing elastic optical networks.

The main weakness of Elastic Optical Networks (EON) stems from spectrum fragmentation. An analysis of periodic defragmentation in EONs under dynamic traffic conditions is carried out. The effects of different defragmentation parameters on the EON performance are evaluated, and appropriate values, guaranteeing suitable network performance while keeping the network control complexity at a reasonable point, are obtained through simulations. Different network topologies as well as traffic conditions are simulated to assess the validity of the obtained results.

©2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. An ONU transmitter for UDWDM PONs based on direct phase modulated distributed feedback lasers (DFB) through digital beat signals is proposed and experimentally tested. The amplitude and duty cycle of the modulating signal are optimized for a DPKS signal. We achieved sensitivities of -50.5 dBm, and -45 dBm for bit rates of 2.5 Gb/s, and 5 Gb/s respectively at BER = 4×10-3 with an intradyne coherent receiver.

Network Function Virtualization (NFV) has recently become one of the most attractive technologies in telecommunication industry due to its ability to realize Network Services (NSs) on general-purpose hardware hence replacing traditional middleboxes. Therefore, NSs can be put on the market, maintained and upgraded more easily and timely which creates a great potential for increasing the usage value of network resources. This paper exploits this paradigm addressing the NFV architecture provisioning the huge computational capacity required in the NS to support the resource allocation strategy proposed for elastic optical networks (EONs) based on resources utilization optimization using a proposed and analyzed squatting-Kicking model (SKM) strategy.

In a previous work, the Virtual Network Topology Reconfiguration problem based on Traffic Prediction (VENTURE) was proposed as a means of efficiently adapting core virtual network topology (VNT) to the near-future traffic. Although the benefits obtained by the VENTURE algorithm compared to using a purely reactive VNT reconfiguration approach seems to be clear, margin for improvement still remain and alternative solving methods for the VENTURE problem need to be considered. In this paper, the original VENTURE algorithm is compared against two state-of-the-art metaheuristics for combinatorial network optimization. The two metaheuristics are first presented and then adapted for the VENTURE problem. Finally, the performance of the VENTURE algorithm and the two proposed metaheuristics is numerically evaluated using an exact solving method as reference. © 2018 IEEE.

This work considers the problem of fault localization in transparent optical networks. The aim is to localize singlelink failures by utilizing statistical machine learning techniques trained on data that describe the network state upon current and past failure incidents. In particular, a Gaussian Process (GP) classifier is trained on historical data extracted from the examined network, with the goal of modeling and predicting the failure probability of each link therein. To limit the set of suspect links for every failure incident, the proposed approach is complemented with the utilization of a Graph-Based Correlation heuristic. The proposed approach is tested on a dataset generated for an OFDM-based optical network, demonstrating that it achieves a high localization accuracy. The proposed scheme can be used by service providers for reducing the Mean-Time-To- Repair of the failure., © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. T. Panayiotou, S. P. Chatzis and G. Ellinas, "A probabilistic approach for failure localization," 2017 International Conference on Optical Network Design and Modeling (ONDM), Budapest, 2017, pp. 1-6.

Optical technologies play nowadays a crucial role in different network scenarios (e.g., data centres, metro and access networks), mainly due to their support for higher bandwidth and scalability in comparison to electronic-based opaque solutions. In this context, the deployment of the Software Defined Networking (SDN) paradigm over optical networks has gained interest from both industry and research communities, spawning several implementations over multiple well documented use cases. However, in Transparent Optical Networks (TONs), where nodes offer optical switching capabilities, neighbouring nodes adjacencies have to be manually configured at both data and control plane levels, which is a lengthy task that can potentially lead to misconfiguration. Alternative solutions rely on the use of supervisory networks or dedicated channels. Nevertheless, implementing these methods requires both effort and resources to provide adjacencies discovery, making the awareness of the correct underlying topology by the SDN controller a tedious and occasionally very complex process. In this paper, we present a novel SDN-based cost-effective topology discovery method, allowing TONs to automatically learn physical adjacencies between optical devices. In particular, this is achieved by means of a test-signal mechanism and the OpenFlow protocol. The SDN control plane and optical agent implementations, as well as the message exchange flow between the subsystems and the controller are described. Then, the proposed discovery mechanism is experimentally assessed over an emulated TON test-bed, analysing the average time required for the optical topology discovery in different network scenarios.

In this paper, we demonstrate an analytical model for computing the end-to-end packet delay of a converged optical/wireless 60 GHz Radio-over-Fiber (RoF) network operating under the medium-transparent MAC (MT-MAC) protocol. For the calculation of the cycle times, this model considers the protocol time consumed for contention and data exchange over both optical and wireless media, a feature of the MT-MAC that effectively enables it to provide direct and seamless interaction between the RoF Central Office and the end users. This new analytical model enables us to conduct an extensive delay performance analysis of the various performance aspects of hybrid RoF networks operating under the fixed service paradigm, such as various optical capacity availability scenarios, varying load conditions, optical network ranges, transmission window lengths, and data packet sizes. The derived theoretical results present an excellent match with the respective simulation findings, providing sub millisecond latency values for a plethora of network conditions, confirming that the MT-MAC scheme can effectively be incorporated into the upcoming mm-wave 5G era. © 2017 IEEE.

Compared to oxide based glasses, vitreous materials composed of chalcogen elements (S, Se, Te) show large transparency windows in the infrared. Indeed, chalcogenide glasses can be transparent from the visible up to 12 – 18 µm, depending on their compositions. In addition, chalcogenide glasses contain large polarisable atoms and external lone electron pairs which induce exceptional non-linear properties. Consequently, the non-linear properties can be 100 or 1000 times as high as the non-linearity of silica. An original way to obtain single-mode fibers is to design microstructured optical fibers (MOFs). These fibers present unique optical properties thanks to the high degree of freedom in the design of their geometrical structure. Our group has prepared various chalcogenide MOFs operating in the IR range in order to associate the high non-linear properties of these glasses and the original MOF properties. Indeed, chalcogenide MOFs might lead to new devices with unique optical properties in the mid-infrared domain like multimode or endlessly single-mode transmission of light, small or large mode area fibers, highly birefringent fibers and non-linear properties for wavelength conversion or generation of supercontinuum sources.

ABNO's OAM Handler is extended with big data analytics capabilities to anticipate traffic changes in volume and direction. Predicted traffic is used to trigger virtual network topology re-optimization. When the virtual topology needs to be reconfigured, predicted and current traffic matrices are used to find the optimal topology. A heuristic algorithm to adapt current virtual topology to meet both actual demands and expected traffic matrix is proposed. Experimental assessment is carried out on UPC's SYNERGY testbed.

Much effort has been devoted to the study of glasses that contain the chalcogen elements (sulfur, selenium and tellurium) for photonics' applications out to MIR wavelengths. In this paper we describe some techniques for determining the refractive index dispersion characteristics of these glasses. Knowledge of material dispersion is critical in delivering step-index fibres including with high numerical aperture for mid-infrared supercontinuum generation.

In this paper, we will demonstrate the possibility of opening a new telecommunications transmission window around the 2 μm wavelength, in order to exploit the potential low loss of hollow-core photonic bandgap fibers, with the benefits of significantly lower non-linearity and latency. We will show recent efforts developing a dense wavelength division multiplexing testbed at this waveband, with 100 GHz spacing wavelength channels and 105 Gbit/s total capacity achieved.

This paper investigates offline virtual topology design in transparent optical networks under a multi-hour traffic demand. The main problem variant addressed here designs a reconfigurable virtual topology which evolves over time to more efficiently utilize network resources (the MH-VTD-R problem). The case of designing a static non-reconfigurable virtual topology which can accommodate the time-varying traffic (the MH-VTD-NR problem) is also considered. The objectives are to minimize (i) the number of transceivers, which make up for the main network cost ; and, (ii) the frequency of reconfiguration (for MH-VTD-R), which incurs additional overhead and potential service disruption. We formulate this multi-objective problem as an exact MILP (Mixed Integer Linear Program). Due to its high complexity, we propose a very efficient heuristic algorithm called GARF (Greedy Approach with Reconfiguration Flattening). GARF not only solves both (non)reconfigurable problem variants, but it allows for tuning of the relative importance of the two objectives. Exhaustive experiments on real and synthetic traffic, and comparison with previous proposals and bounds, reveal the merits of GARF with respect to both solution quality and execution time. Furthermore, the obtained results indicate that the maximal transceiver cost savings achieved by the fully reconfigurable case may not be enough to justify the associated increase in reconfiguration cost. However, results show that an advantageous trade-off between transceiver cost savings and reconfiguration cost can be achieved by a allowing a small number of virtual topology reconfigurations over time.

Photonic crystals due to their angular bandgaps and quasi-bandgaps can provide spatial (angular) filtering of light. Two-dimensional photonic crystals (photonic structures modulated along the longitudinal and along one transverse dimension) can provide spatial filtering in one one-dimensional, decreasing the beam divergence in one quadrature. Three-dimensional crystals can provide two-dimensional filtering, with the shape of the filtering window corresponding to the symmetry of photonic crystal (e.g. forming a quadratic, or hexagonal shape beams). For many applications axisymmetric spatial filtering is required, in order to obtain diffraction limited axisymmetric Gaussian beams. For that purpose we developed and fabricated axisymmetric photonic crystal-like structures (periodic in longitudinal direction, but aperiodic in transverse direction). We overview the axisymmetric filtering: physical principles, simulations, fabrication, and experimental measurements

The paper illustrates the design of two pumping schemes for Mid-IR lasers based on photonic crystal fibers (PCFs) made of dysprosium doped chalcogenide glass Dy3+:Ga 5 Ge 20 Sb 10 S 65 . The simulation is performed by taking into account the spectroscopic parameters measured on the rare earth-doped glass sample in order to perform a realistic feasibility investigation. The first pump scheme provides an optical beam emission close to 4400 nm wavelength by employing two pump beams at the wavelengths close to 2800 nm and 4100 nm, respectively. The second pump scheme allows beam emission close to 4400 nm wavelength via a 1700 nm pump, its efficiency is increased by including a suitable optical amplifier after the laser cavity. The proposed light sources based on chalcogenide glass photonic crystal fibers (PCFs) doped with Dy3+ ions are investigated via a home-made numerical model based on the coupled mode theory and solving the rare earth rate equations. A number of promising applications in different areas such as satellite remote sensing and aerospace, biology, molecular spectroscopy and environmental monitoring are feasible.

Ultra-Dense Wavelength Division Multiplexing (UDWDM) has been proposed for the optical access Passive Optical Network (PON) in the COst-effective COhereNt Ultra-dense-WDM-PON for lambda-To-the-user access (COCONUT) project, introducing the wavelength-to-the-user concept. A low-cost high sensitivity coherent detection technique furnishes high splitting ratios and long-reach extension. ONU coherent transceivers employ lasers with wavelengths randomly distributed and densely spaced in the optical band, but owning limited tunability. The wavelength channels are allocated using heuristic Dynamic Wavelength Assignment (DWA) algorithms. These schemes are applied not only in activation processes, but also during operation under environmental conditions, adapting the laser tuning to provide the required assigned channel. The laser tuning is achieved by heating or cooling control, and the power consumption varies depending on the wavelength position in a tuning window. We evaluate and compare the power consumption of the developed DWA schemes in the network, as energy efficiency is important to reduce the green-house gas emissions. © 2016 IEEE.

Made available in DSpace on 2016-04-04T18:31:45Z (GMT). No. of bitstreams: 1 RICARDO VICENTE FAVERO.pdf: 1635235 bytes, checksum: d51f441103ff9f2ad94576b0bdd11b9f (MD5) Previous issue date: 2015-11-13 The wavelength division multiplexing (WDM) optical network accommodates traffic load in 100, 50 and 25 GHz fixed-grid channel. This fixed-grid condition limits the number of lightpath for each optical fiber (80 channels in c-band) and doesn t allow bit rates with bandwidth over 50 GHz. To improve these factors, the flexibly grid elastic optical network (EON) was proposed, aiming accommodate adequately bit rates demand by customers. This proposal allows efficiency bandwidth and also expands bit rates supported by network. The EON bandwidth efficiency is obtained by routing and spectrum assignment (RSA) algorithm which acts to maximize the bandwidth utilization. Even with RSA, EON still show fragmentation rates substantial. In this context, this work proposes a new elastic optical network defragmentation strategy. This defragmentation strategy selects the lightpaths from the most fragmented link. The defragmentation process is based on RSA (DF-RSA). The DF-RSA determines the new position to reallocate the connection selected and performs. Using computer simulation of EON operation, were submitted several bit rates demands with different modulations format and traffic load between 45 and 100 erlang. Two simulation scenarios were proposed. The first one, compare the performance of RSA algorithm first-fit (FF) with and without defragmentation. It was considered as defragmentation process beginning point (trigger), the number of release connections. This scenario had until 48% of relative gain on minimizing blocking probability. The second scenario compared the performance of the follows RSA algorithms: FF, Maximize Path Spectrum Consecutiveness (MPSC) and Fragmentation Aware (FA). The FF was evaluated with and without defragmentation process and the others just with defragmentation process. The trigger employed was eventual connection blocked. The second scenario reached over the 80% blocking probability relative gain in 50 erlang traffic load. We conclude that the new elastic optical network defragmentation offers substantial gain bandwidth utilization and consequently blocking probability reduction. As redes ?pticas de multiplexa??o por divis?o de comprimento de onda (WDM) acomodam o tr?fego em canais fixos de 100, 50 e 25 GHz. Esta condi??o de grade fixa limita o n?mero de conex?es por fibra ?ptica (80 canais na banda C), e n?o permite taxas de transmiss?o com ocupa??o espectral acima de 50 GHz. Para melhorar estes fatores, foram propostas as redes ?pticas el?sticas (EON) com canais flex?veis, visando acomodar adequadamente as taxas de transmiss?o demandas pelos usu?rios. Esta proposta possibilita maior efici?ncia espectral e tamb?m amplia as taxas de transmiss?o suportadas pela rede. A efici?ncia espectral nas EONs ? obtida com os algoritmos de roteamento e atribui??o espectral (Routing and Spectrum Assignment, RSA), que atuam para maximizar seu uso espectral. Mesmo com o uso de RSAs, as EONs ainda apresentam ?ndices de fragmenta??o consider?veis. Neste contexto, este trabalho prop?e uma nova estrat?gia de desfragmenta??o espectral para EONs. Esta proposta de desfragmenta??o seleciona as conex?es do enlace mais fragmentado, para o processo de desfragmenta??o. A desfragmenta??o baseia seu processo de realoca??o de conex?es por RSA, denominado DF-RSA. O DF-RSA determina a nova posi??o e realiza a realoca??o das conex?es. Com o uso de simula??o computacional da opera??o de funcionamento da EON, foram submetidas v?rias demandas de taxas de transmiss?o com diferentes modula??es e cargas de tr?fego entre 45 e 100 erlang. Foram propostos dois cen?rios de simula??o. No primeiro, foi comparado o desempenho do algoritmo RSA First-Fit (FF) com e sem o processo de desfragmenta??o. Considerou-se como ponto de inicio das desfragmenta??es (gatilho), o n?mero de conex?es liberadas da rede. Neste cen?rio obteve-se at? 48% de ganho relativo na minimiza??o da probabilidade de bloqueio. No segundo cen?rio, foram comparados os desempenhos dos seguintes algoritmos RSAs: FF, Maximize Path Spectrum Consecutiveness (MPSC) e Fragmentation Aware (FA). O FF foi avaliado com e sem desfragmenta??o e os demais somente com desfragmenta??o. Empregou-se como gatilho o eventual bloqueio de conex?o. O segundo cen?rio alcan?ou mais de 80% de ganho relativo de probabilidade de bloqueio para carga de tr?fego de 50 erlang. Conclui-se que a nova estrat?gia de desfragmenta??o para EONs oferece ganhos consider?veis na utiliza??o espectral e, consequentemente, redu??o na probabilidade de bloqueio.

Future optical networks call for flexible, high performance and low cost coherent optical receivers. We present here several advances towards such receivers, including integrated optical couplers with ultra-broad bandwidth, as well as novel reception techniques and architectures that will enable high performance coherent reception without filtering and polarization splitting elements., 17th International Conference on Transparent Optical Networks, ICTON 2015, 5 July 2015 through 9 July 2015

Este trabalho tem por objetivo a obtenção de um modelo matemático para a determinação da taxa de ocupação de ambientes internos baseado na intensidade de sinal de uma Rede de Sensores sem Fio em 915 MHz utilizando quatro links rádio no ambiente. Foi montada uma rede com uma base e quatro nós sensores em um laboratório como intuito de coletar a RSSI (Received Signal Strenght Indication) de cada link para cada diferente ocupação do espaço para cada grupo de pessoas. Com base nos dados coletados, foram calculados a média, desvio padrão e variância de cada link e cada grupo de pessoas. Esses dados foram utilizados como entrada em modelos matemáticos para a determinação da taxa de ocupação do ambiente. Foram propostos três modelos matemáticos para tal estimação. Os três modelos se mostraram aptos a estimar o número de pessoas utilizando a média geral dos links. Os resultados iniciais mostraram que a tendência é de diminuição da RSSI e o aumento do desvio padrão quanto maior o número de pessoas no ambiente. Alguns links analisados de forma individual se mostraram com uma variação grande e não seguindo inteiramente a tendência mencionada, mas apesar disso a média geral dos links segue essa tendência, ou seja, apesar de um link demonstrar uma grande variação, os outros links tenderam a compensar essa variação. Com a média geral é possível chegar a um erro pequeno entre o número real de pessoas e o número estimado de pessoas. Para a escolha do melhor modelo foi utilizado o RAM (Resíduo Absoluto Médio) e para a média geral dos links o modelo de segunda ordem foi o que se mostrou melhor com um resíduo abaixo de meia pessoa. Por fim os resultados obtidos com multilink foram comparados com resultados obtidos em um trabalho em que foi utilizado single-link para a obtenção da taxa de ocupação em um ambiente interno. Multilink, com um RAM de aproximadamente 0,5 pessoas, se mostrou com um erro menor comparado com o single-link, que obteve um erro de aproximadamente duas pessoas. This work aims to obtain a mathematical model to determinate the occupancy rate in indoor environment based on signal strength of a wireless sensor network (WSN) in 915 MHz using four links at the environment. It was set a network with one sink and four node sensors in a laboratory in order to collect the RSSI (Received Signal Strength Indication) of each individual link for every different space occupation for each group of people. Based on the data collected, it was calculated the mean, standard deviation and the variance of each individual link and the overall average of links for each group of people. The data was used as input in mathematical models to determine the occupancy rate of the environment. Three mathematical models have been proposed to estimate the occupancy rate. All of them proved capable to estimate the number of people using the overall average of links. The results showed that the tendency is to decrease the RSSI and increase the standard deviation the greater the number of people in the environment. Some links analyzed individually showed a large variation and not following entirely the tendency mentioned. Nevertheless the overall average of links follows this tendency showing that despite a link shows a great variation, the other links tended to compensate this variation and with the overall average of links is possible to get a small error between the real number of people and the estimated number of people. To choose the best model it was used the MAE (Mean Absolute Error). The second order model was the best model with a MAE slightly below of a half people. The results obtained using multilink were compared with a work that used single-link to predict the number of people in a indoor environment. Multilink had a smaller error compared with single-link, which obtained an error of about two people.

Processing of high-frequency, wide-band signals is conveniently performed in the optical domain due to availability of optical filters which intrinsically have a wide-band response. On the other end, there are several application scenarios where very sharp pass-band filtering is required. In these cases, realizing the processing in the optical domain might not be technically simple, although filters of extremely high Q-factor have been demonstrated. This paper presents the feasibility of signal processing based on very sharp electrical filtering (< 1 GHz around 193 THz) assisted by optical down-conversion, i.e., by means of optical coherent detection. In particular, we show experimentally two applications where the filtering capability is exploited to perform signal processing: the demodulation of phase-modulated optical signals and the implementation of a chirp-managed transmission link. Other possible applications of this technique will be also discussed at the presentation.

Doutoramento em Engenharia Eletrotécnica Submitted by Patrícia Correia (patriciacorreia@ua.pt) on 2015-05-19T15:59:38Z No. of bitstreams: 1 amplificadores de fibra em redes ópticas transparentes e dinâmicas.pdf: 6937016 bytes, checksum: dac8ceebe1ee2f2aa65706d2592e9534 (MD5) Made available in DSpace on 2015-05-19T15:59:38Z (GMT). No. of bitstreams: 1 amplificadores de fibra em redes ópticas transparentes e dinâmicas.pdf: 6937016 bytes, checksum: dac8ceebe1ee2f2aa65706d2592e9534 (MD5) Previous issue date: 2015

Doutoramento em Engenharia Eletrotécnica In this thesis a study of optical fiber amplifiers in the context of transparent and dynamic optical networks is performed. We propose and validate a simplified model to estimate the gain profile and amplified spontaneous emission (ASE) noise of broadband counterpumped Raman fiber amplifiers (RFAs). The proposed model requires very low computational resources and it is suitable to be used in network planning tools. Based on the proposed model, we also present an algorithm to design flat gain counter-pumped RFAs for the extended C-band with low computational requirements. We experimentally verify that the pump-reflecting RFA presents a higher transient response due to channels add/drop, when compared to the conventional counter-pumped RFA. This makes this amplifier configuration unsuitable for transparent and dynamic optical networks. To mitigate the transient response due to channel add/drop, a pumpcontrolled gain-locked system based on the monitorization of the reflected pump power is proposed and validated numerically and experimentally. Following this approach, an efficient low-cost RFA suitable for dynamic optical networks is proposed. The dependence of the dynamical response of erbium-doped fiber amplifiers (EDFAs) on the pump wavelength, pump power, and temperature due to spectral hole burning (SHB) and site dependent pumping (SDP) is experimentally investigated. A dependence of the dynamic response on the pump wavelength, for amplifiers pumped around 1480 nm, is shown. In order to explain this dependence, the impact of SDP on the performance of EDFAs pumped at wavelengths around 1480 nm is investigated, both experimentally and numerically. As a result, an improved model incorporating the SDP effect for twolevel EDFAs is derived and experimentally validated. Nesta tese é feito um estudo sobre amplificadores de fibra ótica no contexto de redes óticas transparentes e dinâmicas. Propomos e validamos um modelo simplificado para estimar o perfil do ganho e do ruído de emissão espontânea amplificada (ASE), para amplificadores de Raman (RFAs) contra propagantes. O modelo proposto requer baixos recursos computacionais e é adequado para ser usado em ferramentas de planeamento da rede. Com base no modelo proposto, apresentamos também um algoritmo com requisitos computacionais baixos para desenhar RFAs contra propagantes com ganho constante para a banda C estendida. Verificamos experimentalmente que um RFA contra propagante com reflexo da potência da bomba devido à adição/remoção de canais apresenta uma resposta transiente mais elevada, quando comparado com um RFA contra propagante convencional. Isto torna esta configuração inadequada para redes óticas transparentes e dinâmicas. Para mitigar a resposta transitória devido à adição/remoção de canais, um sistema de controlo do ganho baseado na monitorização da potência da bomba refletida é proposto e validado numérica e experimentalmente. Seguindo esta abordagem, um RFA contra propagante eficiente e de baixo custo adequado para redes óticas dinâmicas é proposto. A dependência da resposta dinâmica dos amplificadores de fibra dopada com érbio (EDFAs) em função do comprimento de onda da bomba, da potência da bomba e da temperatura devido ao spectral hole burning (SHB) e site dependent pumping (SDP) é investigada experimentalmente. Nos resultados obtidos é mostrada a dependência da resposta dinâmica em função do comprimento de onda da bomba, para amplificadores bombeados em torno de 1480 nm. Para explicar esta dependência, o impacto do SDP no desempenho de EDFAs bombeados em comprimentos de onda em torno de 1480 nm é investigado, tanto experimental como numericamente. Como resultado, um modelo mais completo, incorporando o efeito SDP para EDFAs de dois níveis é derivado e validado experimentalmente.

Date of Conference: 2-7 February 2013 Conference name: Proceedings of SPIE, Photonic and Phononic Properties of Engineered Nanostructures III Plasmonics mainly deals with light-matter interactions in metallic nanostructures. It has gathered interest since its discovery due to the benefits it provides when compared with photonics and electronics. It owes its popularity to the tremendous number of applications it serves for. In this paper, we review how plasmonic nanoparticles can be utilized in applications such as localized surface plasmon resonance based biosensing and enhancing performance of photodetectors. © 2013 SPIE.

Recently the beam focusing in reflection from chirped dielectric mirror has been proposed and demonstrated, where the negative (anomalous) diffraction is responsible for this flat mirror focusing. For a strong focusing performance (large focal distance), a wide angular range of strong (negative) angular dispersion is required. We show that a defect layer in the dielectric mirror (one layer is of a double size), can increase the angular dispersion, and thus improve the focusing performance. By introducing a defect layer in the chirped mirror, the focal distances can be increase from 12 µm up to 22 µm in a specific, calculated, structure, as our numerical integration show.

Subwavelength grating structures with a pitch smaller than the Bragg resonance length can be used for engineering the refractive index in silicon photonic waveguides. We discuss the principles, design, fabrication and applications of subwavelength nanostructures in silicon photonics and review our recent results on fiber-chip coupling structures, surface grating couplers, waveguide crossings, and athermal waveguides with a polymersilicon hybrid core., 16th International Conference on Transparent Optical Networks, ICTON 2014, 6 July 2014 through 10 July 2014, Graz

Novas redes ópticas de multiplexação por divisão de comprimento de onda (Wavelength Division Multiplexing, WDM) podem utilizar vários canais com taxas diferentes de bits. Além disso, cada um dos canais individuais pode transportar mais de 200 Gb/s e ocupar uma largura de banda que excede a grade fixa de 50 GHz da rede WDM. Neste cenário, a eficiência espectral torna-se uma questão importante e novos esquemas de alocação de canais precisam ser considerados. Uma solução atrativa para este problema é a utilização de uma rede WDM com espaçamento de canal variável, na abordagem chamada rede óptica elástica (EON). O principal objetivo do presente trabalho é propor algoritmos para resolver a questão da eficiência espectral em redes ópticas WDM emergentes. Tais propostas são divididas em duas classes. A primeira consiste em alocar diferentes blocos de espectro para canais com diferentes taxas de bits, o que é apontado como esquema de divisão de blocos de espectro (Spectrum Block Division, SBD). A segunda classe é baseada em esquemas de EON. Neste caso, não só o aperfeiçoamento de um algoritmo previamente descrito por WANG (2012), o algoritmo Maximize Total Link Spectrum Consecutiveness (MTLSC), é considerado, mas também um novo algoritmo, o Shortest Path with Maximum number of Free Frequency Slot Units (SPMFF) é proposto. Outra contribuição deste trabalho é o desenvolvimento de um simulador de EON, chamado EONSim, com base na linguagem de programação JAVA. Este simulador foi devidamente testado e foram reproduzidos os resultados de WANG (2012) dentro de uma precisão muito boa. Todos os resultados foram obtidos com a ajuda de EONSim e sugerem que os algoritmos propostos produzem um ganho de ocupação de banda, que varia de 7 a 18% mais elevada do que a fornecida pelo tradicional algoritmo First Fit (FF). Tais algoritmos também proporcionam uma probabilidade de bloqueio, que é de 2 a 8% mais baixa do que na estratégia FF. Por outro lado, verifica-se que os algoritmos de melhor ocupação espectral utilizam um número médio de saltos até 16% mais elevado do que os necessários para os algoritmos de menor caminho, que não levam em conta a largura de banda de atribuição de canal. New optical wavelength division multiplexing (WDM) networks are expected to utilize multiple bit rate channels. Moreover, each individual channels may carry over 200 Gb/s and occupy a bandwidth that exceeds the 50-GHz WDM fixed grid. In this scenario, spectral efficiency becomes an important issue and new channel allocation schemes need to be considered. An attractive solution for this problem is the utilization of a WDM grid with variable channel spacing, in the so-called elastic optical network (EON) approach. The main goal of this work is to propose algorithms to solve the spectral efficiency issue in emerging optical WDM networks. Such proposals are divided in two classes. The first one consists of allocating different spectral blocks for channels with different bit rates; this is named as the spectrum block division (SBD) scheme. The second class of our proposals is based on EON schemes. In this case, not only the enhancement of a previously reported algorithm, the Maximize Total Link Spectrum Consecutiveness (MTLSC) algorithm, is considered but also a new algorithm, the Shortest Path with Maximum number of Free Frequency Slot Units (SPMFF) is proposed. Another contribution of this work is the development of an EON simulator, called EONSim, based on JAVA programming language. This simulator was properly tested and reproduced the results of literature papers within a very good accuracy. All of our results were obtained with the aid of EONSim and suggest that the proposed algorithms yield a bandwidth occupation gain that varies from 7 to 18% higher than the one provided by traditional first-fit (FF) algorithms. Such algorithms also provide a blocking probability that is 2 to 8% lower than in FF strategy. On the other hand, it is found that algorithms with higher spectral efficiency use an average number of hops that is up to 16% higher than those necessary for algorithms that do not take bandwidth into account in channel allocation.

Made available in DSpace on 2016-04-04T18:31:40Z (GMT). No. of bitstreams: 1 Paulo Cesar Barreto da Silva.pdf: 3934588 bytes, checksum: cbbb71074cd6c370e06fd00f5d3eabce (MD5) Previous issue date: 2014-02-05 New optical wavelength division multiplexing (WDM) networks are expected to utilize multiple bit rate channels. Moreover, each individual channels may carry over 200 Gb/s and occupy a bandwidth that exceeds the 50-GHz WDM fixed grid. In this scenario, spectral efficiency becomes an important issue and new channel allocation schemes need to be considered. An attractive solution for this problem is the utilization of a WDM grid with variable channel spacing, in the so-called elastic optical network (EON) approach. The main goal of this work is to propose algorithms to solve the spectral efficiency issue in emerging optical WDM networks. Such proposals are divided in two classes. The first one consists of allocating different spectral blocks for channels with different bit rates; this is named as the spectrum block division (SBD) scheme. The second class of our proposals is based on EON schemes. In this case, not only the enhancement of a previously reported algorithm, the Maximize Total Link Spectrum Consecutiveness (MTLSC) algorithm, is considered but also a new algorithm, the Shortest Path with Maximum number of Free Frequency Slot Units (SPMFF) is proposed. Another contribution of this work is the development of an EON simulator, called EONSim, based on JAVA programming language. This simulator was properly tested and reproduced the results of literature papers within a very good accuracy. All of our results were obtained with the aid of EONSim and suggest that the proposed algorithms yield a bandwidth occupation gain that varies from 7 to 18% higher than the one provided by traditional first-fit (FF) algorithms. Such algorithms also provide a blocking probability that is 2 to 8% lower than in FF strategy. On the other hand, it is found that algorithms with higher spectral efficiency use an average number of hops that is up to 16% higher than those necessary for algorithms that do not take bandwidth into account in channel allocation. Novas redes ?pticas de multiplexa??o por divis?o de comprimento de onda (Wavelength Division Multiplexing, WDM) podem utilizar v?rios canais com taxas diferentes de bits. Al?m disso, cada um dos canais individuais pode transportar mais de 200 Gb/s e ocupar uma largura de banda que excede a grade fixa de 50 GHz da rede WDM. Neste cen?rio, a efici?ncia espectral torna-se uma quest?o importante e novos esquemas de aloca??o de canais precisam ser considerados. Uma solu??o atrativa para este problema ? a utiliza??o de uma rede WDM com espa?amento de canal vari?vel, na abordagem chamada rede ?ptica el?stica (EON). O principal objetivo do presente trabalho ? propor algoritmos para resolver a quest?o da efici?ncia espectral em redes ?pticas WDM emergentes. Tais propostas s?o divididas em duas classes. A primeira consiste em alocar diferentes blocos de espectro para canais com diferentes taxas de bits, o que ? apontado como esquema de divis?o de blocos de espectro (Spectrum Block Division, SBD). A segunda classe ? baseada em esquemas de EON. Neste caso, n?o s? o aperfei?oamento de um algoritmo previamente descrito por WANG (2012), o algoritmo Maximize Total Link Spectrum Consecutiveness (MTLSC), ? considerado, mas tamb?m um novo algoritmo, o Shortest Path with Maximum number of Free Frequency Slot Units (SPMFF) ? proposto. Outra contribui??o deste trabalho ? o desenvolvimento de um simulador de EON, chamado EONSim, com base na linguagem de programa??o JAVA. Este simulador foi devidamente testado e foram reproduzidos os resultados de WANG (2012) dentro de uma precis?o muito boa. Todos os resultados foram obtidos com a ajuda de EONSim e sugerem que os algoritmos propostos produzem um ganho de ocupa??o de banda, que varia de 7 a 18% mais elevada do que a fornecida pelo tradicional algoritmo First Fit (FF). Tais algoritmos tamb?m proporcionam uma probabilidade de bloqueio, que ? de 2 a 8% mais baixa do que na estrat?gia FF. Por outro lado, verifica-se que os algoritmos de melhor ocupa??o espectral utilizam um n?mero m?dio de saltos at? 16% mais elevado do que os necess?rios para os algoritmos de menor caminho, que n?o levam em conta a largura de banda de atribui??o de canal.

Transparent optical networks are sensitive to high-power jamming which can degrade legitimate user signals via out-of-band effects in optical fibers and amplifiers, and in-band crosstalk in optical switches. Jamming signals can be inserted in the network either deliberately as an attack, with the intention to deteriorate service, or accidentally, due to component miscon-figuration. This type of attack/failure can potentially propagate through the network causing high data and revenue losses, requiring tailored survivability approaches which take these harmful effects into consideration. Namely, conventional network survivability approaches which protect transmission in case of component faults might not provide adequate protection from jamming since the working and backup paths of a connection may both be within reach of the same jamming signal, even if they are link/node disjoint. Previously, we proposed the concept of an Attack Group (AG) of an all-optical connection (referred to as a lightpath), comprised of all other lightpaths which potentially can affect it in case they carry a high-power jamming signal. Furthermore, we developed a jamming attack-aware dedicated path protection algorithm which establishes AG-disjoint working and backup paths for each connection. Herein, we extend this work by proposing an approach for Jamming-Aware Shared Path Protection (JA-SPP) to achieve survivability in the presence of jamming signals in a more resource-efficient way. We formulate the JA-SPP problem as an Integer Linear Problem (ILP) to obtain optimal solutions for smaller network instances. Comparison with standard SPP for single component faults (without jamming-awareness) shows that JA-SPP obtains solutions which offer protection from high-power jamming, in addition to single component faults, while using the same amount of resources (in terms of link and wavelength usage) as the standard SPP.

We report a spatial heterodyne Fourier-transform spectrometer consisting of an array of Mach-Zehnder interferometers (MZI) implemented in silicon microphotonics. Optical path differences between the MZI arms increase linearly along the array, generating a wavelength-dependent interferogram which enables the retrieval of the source spectrum with a single measurement. Optical delays were implemented with Si-wire waveguides arranged in tightly coiled spirals to achieve a high resolution in a reduced footprint. Our spectral retrieval algorithm compensates phase and amplitude errors arising from fabrication imperfections by using a transformation matrix based on the calibration data. A wavelength resolution of 40 pm within a free spectral range of 0.75 nm is demonstrated., 15th International Conference on Transparent Optical Networks, ICTON 2013, June 23-27, 2013, Cartagena, Spain, Series: International Conference on Transparent Optical Networks : [proceedings]

Includes bibliography (p. 215-232). Number of sources in the bibliography: 238 Thesis (Ph. D.) -- University of Cyprus, Faculty of Engineering, Department of Electrical and Computer Engineering, 2013. The University of Cyprus Library holds the printed form of the thesis. Τα οπτικά δίκτυα επόμενης γενιάς αναμένεται ότι θα μπορούν να υποστηρίζουν ταυτόχρονα εφαρμογές που χρειάζονται μονοσημειακές αλλά και πολυσημειακές συνδέσεις. Μερικές πρόσφατες εφαρμογές που χρειάζονται μεγάλη χωρητικότητα και θα μπορούσαν να υποστηριχτούν καλύτερα από πολυσημειακές συνδέσεις είναι η ταυτόχρονη διανομή βίντεο σε πολλούς χρήστες, η εκπαίδευση εξ’ αποστάσεως και η εκπαίδευση μέσω βίντεο, οι εφαρμογές τηλεπαρουσίας και τηλεϊατρικής, η αναμετάδοση ταινιών σε πολλούς χρήστες, τα διαδικτυακά παιχνίδια, καθώς και οι εφαρμογές υπολογιστικού πλέγματος. Παράλληλα με την ανάπτυξη των πολυσημειακών εφαρμογών, τα οπτικά δίκτυα επόμενης γενιάς εξελίσσονται από μη-αμιγώς δίκτυα, σε δίκτυα με αμιγώς οπτικές περιοχές, και τελικά σε εξ’ ολοκλήρου αμιγώς οπτικά δίκτυα. Τα αμιγώς οπτικά δίκτυα είναι επιθυμητά αφού μπορούν να παρέχουν διαφάνεια στους ρυθμούς μετάδοσης, στα πρωτόκολλα επικοινωνίας, και στην διαμόρφωση του σήματος. Αυτά τα δίκτυα μπορούν να προσφέρουν καλύτερες λύσεις όσο αφορά την αρχιτεκτονική των οπτικών δικτύων, αφού το κόστος υλοποίησης τους ελαχιστοποιείται, χρειάζονται λιγότερη ισχύ, καθώς και λιγότερο χώρο για την εγκατάσταση του εξοπλισμού του δικτύου, αφού πλέον δεν χρειάζονται οι επιπλέον πομποί και δέκτες που χρειάζονται για την λειτουργία ενός μη-αμιγώς οπτικού δικτύου. Επιπλέον, αυτές οι αρχιτεκτονικές πρέπει να μπορούν να υποστηρίξουν αποδοτικά εφαρμογές διάφορων τύπων συνδέσεων, συμπεριλαμβανομένων και των πολυσημεικών συνδέσεων, που είτε χρειάζονται ολόκληρη την χωρητικότητα που μπορεί να προσφέρει ένα μήκος κύματος είτε χρειάζονται μόνο ένα μέρος αυτής της χωρητικότητας. Στα τηλεπικοινωνιακά δίκτυα, είναι επίσης σημαντική η απρόσκοπτη παροχή υπηρεσιών μέσω τεχνικών αποκατάστασης βλαβών για την προστασία του δικτύου. Οι πολυσημειακές συνδέσεις που στέλνουν πληροφορίες σε πολλούς προορισμούς ταυτόχρονα είναι περισσότερο επιρρεπείς στις βλάβες στο δίκτυο, αφού μια και μόνο βλάβη στο δίκτυο μπορεί να οδηγήσει στην απώλεια πληροφορίας που προορίζεται για ένα μεγάλο αριθμό χρηστών. Γι’ αυτό και οι τεχνικές προστασίας βλαβών που αφορούν πολυσημειακές συνδέσεις είναι εξαιρετικά σημαντικές στα οπτικά δίκτυα επόμενης γενιάς. Στόχος αυτής της διατριβής είναι η διερεύνηση προβλημάτων που σχετίζονται με πολυσημειακές συνδέσεις σε μητροπολιτικά οπτικά δίκτυα τυχαίων τοπολογιών, όταν οι επιδράσεις του φυσικού στρώματος λαμβάνονται υπόψη κατά τον σχεδιασμό και την υλοποίηση αλγορίθμων δρομολόγησης για την εγκατάσταση και προστασία των συνδέσεων. Η κύρια συμβολή αυτής της διατριβής αφορά τον σχεδιασμό και την υλοποίηση αλγορίθμων δρομολόγησης για την εγκατάσταση και προστασία των πολυσημειακών συνδέσεων, σε αμιγώς οπτικά δίκτυα, λαμβάνοντας υπόψη τις επιδράσεις του φυσικού στρώματος. Αυτή η διατριβή γεμίζει ένα κενό που υπάρχει στην έρευνα, αναπτύσσοντας αποδοτικές λύσεις για αυτά τα προβλήματα σε μητροπολιτικά οπτικά δίκτυα με τοπολογία πλέγματος. Όλες οι τεχνικές που αναπτύχθηκαν για την δρομολόγηση, πολυπλεξία, και προστασία των πολυσημειακών συνδέσεων, σχεδιάστηκαν λαμβάνοντας υπόψιν τους περιορισμούς του φυσικού στρώματος και παρουσιάζουν σημαντική βελτίωση στην απόδοσή τους σε σχέση με τις προηγούμενες τεχνικές που έχουν αναπτυχθεί μέχρι τώρα. Σε αυτή την διατριβή παρουσιάζεται μια ολοκληρωμένη λύση για την εγκατάσταση και προστασία πολυσημειακών συνδέσεων σε αμιγώς οπτικά δίκτυα, μέσω της ανάπτυξης ενός μοντέλου για τον υπολογισμό των επιδράσεων του φυσικού στρώματος, της ανάπτυξης και σχεδιασμού κατάλληλων αρχιτεκτονικών κόμβων, καθώς και μέσω της ανάπτυξης και εκτίμησης ενός μεγάλου αριθμού ευριστικών αλγορίθμων που μπορούν να αυξήσουν την απόδοση αυτών των δικτύων. Ενώ αυτή η διατριβή επικεντρώνεται σε μητροπολιτικά οπτικά δίκτυα, οι μέθοδοι και τεχνικές που αναπτύσσονται σε αυτή την διατριβή μπορούν να εφαρμοστούν και σε άλλους τύπους δικτύων, δεδομένου ότι οι επιδράσεις του φυσικού στρώματος που σχετίζονται με αυτά τα δίκτυα λαμβάνονται υπόψη στην μοντελοποίηση του φυσικού στρώματος. Next-generation optical networks are expected to support traffic that will be heterogeneous in nature with both unicast, as well as multicast/groupcast applications. Recent bandwidth-intensive applications that are driving the use of optical multicasting include telepresence, grid computing, telemedicine, software and video distribution for residential customers, movie broadcasts, interactive distance learning and video training, and distributed games amongst others. In parallel to the emergence of high-bandwidth multicast applications, the trend is for next-generation mesh optical networks that are evolving from opaque to translucent, and eventually to transparent optical networks. These transparent networks are extremely desirable as they provide bit-rate, protocol, and modulation format transparency, thus providing better solutions in the implementation of the network architecture by minimizing the extra cost, power, and footprint associated with the additional transceivers present in an opaque architecture. These architectures must now also have the capability and build-in intelligence to efficiently support all types of traffic and all kinds of applications, including both unicast as well as multicast/groupcast applications that require either the entire or a fraction of the wavelength bandwidth. In telecommunications networks, it is also essential that services are provided in an uninterrupted manner, leveraging fault recovery techniques and intelligent switching nodes to protect the network against failures. Multicast applications that carry traffic to multiple destinations are even more susceptible to failures as a single failure can result in the loss of information destined to a large number of users. Thus, providing failure recovery techniques for the multicast applications is of paramount importance in next-generation optical networks. The objective of this dissertation is to investigate problems related to impairment-aware multicasting/groupcasting in metropolitan area mesh optical networks, when the physical layer impairments are also taken into consideration when designing and implementing the appropriate provisioning and protection techniques. The main contributions of this dissertation are in the design and implementation of provisioning and protection techniques for the impairment-aware support of multicast and groupcast applications in transparent optical networks. This dissertation fills an existing void in that area by formulating and developing efficient solutions for these problems in metropolitan area optical networks with mesh topologies. All techniques developed for wavelength routing, subrate grooming, and fault protection for multicast and groupcast applications in these networks were designed while taking into consideration the physical layer constraints, and by doing so they exhibited improved performance compared to all the rest of the previously developed techniques. This dissertation presents a complete treatment to the impairment-aware multicast and groupcast provisioning and fault recovery problem by investigating the physical layer system model, node architectures and network engineering, as well as designing and evaluating a large number of heuristic algorithms that can provide these network control functions in a simple and efficient manner. While this work focuses on metropolitan area networks, these methods and techniques can also be readily applicable to other types of networks as well, provided that the network-specific physical layer impairments are accounted for in the physical layer system model.

Includes bibliography (p. 215-232). Number of sources in the bibliography: 238 Thesis (Ph. D.) -- University of Cyprus, Faculty of Engineering, Department of Electrical and Computer Engineering, 2013. The University of Cyprus Library holds the printed form of the thesis. Τα οπτικά δίκτυα επόμενης γενιάς αναμένεται ότι θα μπορούν να υποστηρίζουν ταυτόχρονα εφαρμογές που χρειάζονται μονοσημειακές αλλά και πολυσημειακές συνδέσεις. Μερικές πρόσφατες εφαρμογές που χρειάζονται μεγάλη χωρητικότητα και θα μπορούσαν να υποστηριχτούν καλύτερα από πολυσημειακές συνδέσεις είναι η ταυτόχρονη διανομή βίντεο σε πολλούς χρήστες, η εκπαίδευση εξ’ αποστάσεως και η εκπαίδευση μέσω βίντεο, οι εφαρμογές τηλεπαρουσίας και τηλεϊατρικής, η αναμετάδοση ταινιών σε πολλούς χρήστες, τα διαδικτυακά παιχνίδια, καθώς και οι εφαρμογές υπολογιστικού πλέγματος. Παράλληλα με την ανάπτυξη των πολυσημειακών εφαρμογών, τα οπτικά δίκτυα επόμενης γενιάς εξελίσσονται από μη-αμιγώς δίκτυα, σε δίκτυα με αμιγώς οπτικές περιοχές, και τελικά σε εξ’ ολοκλήρου αμιγώς οπτικά δίκτυα. Τα αμιγώς οπτικά δίκτυα είναι επιθυμητά αφού μπορούν να παρέχουν διαφάνεια στους ρυθμούς μετάδοσης, στα πρωτόκολλα επικοινωνίας, και στην διαμόρφωση του σήματος. Αυτά τα δίκτυα μπορούν να προσφέρουν καλύτερες λύσεις όσο αφορά την αρχιτεκτονική των οπτικών δικτύων, αφού το κόστος υλοποίησης τους ελαχιστοποιείται, χρειάζονται λιγότερη ισχύ, καθώς και λιγότερο χώρο για την εγκατάσταση του εξοπλισμού του δικτύου, αφού πλέον δεν χρειάζονται οι επιπλέον πομποί και δέκτες που χρειάζονται για την λειτουργία ενός μη-αμιγώς οπτικού δικτύου. Επιπλέον, αυτές οι αρχιτεκτονικές πρέπει να μπορούν να υποστηρίξουν αποδοτικά εφαρμογές διάφορων τύπων συνδέσεων, συμπεριλαμβανομένων και των πολυσημεικών συνδέσεων, που είτε χρειάζονται ολόκληρη την χωρητικότητα που μπορεί να προσφέρει ένα μήκος κύματος είτε χρειάζονται μόνο ένα μέρος αυτής της χωρητικότητας. Στα τηλεπικοινωνιακά δίκτυα, είναι επίσης σημαντική η απρόσκοπτη παροχή υπηρεσιών μέσω τεχνικών αποκατάστασης βλαβών για την προστασία του δικτύου. Οι πολυσημειακές συνδέσεις που στέλνουν πληροφορίες σε πολλούς προορισμούς ταυτόχρονα είναι περισσότερο επιρρεπείς στις βλάβες στο δίκτυο, αφού μια και μόνο βλάβη στο δίκτυο μπορεί να οδηγήσει στην απώλεια πληροφορίας που προορίζεται για ένα μεγάλο αριθμό χρηστών. Γι’ αυτό και οι τεχνικές προστασίας βλαβών που αφορούν πολυσημειακές συνδέσεις είναι εξαιρετικά σημαντικές στα οπτικά δίκτυα επόμενης γενιάς. Στόχος αυτής της διατριβής είναι η διερεύνηση προβλημάτων που σχετίζονται με πολυσημειακές συνδέσεις σε μητροπολιτικά οπτικά δίκτυα τυχαίων τοπολογιών, όταν οι επιδράσεις του φυσικού στρώματος λαμβάνονται υπόψη κατά τον σχεδιασμό και την υλοποίηση αλγορίθμων δρομολόγησης για την εγκατάσταση και προστασία των συνδέσεων. Η κύρια συμβολή αυτής της διατριβής αφορά τον σχεδιασμό και την υλοποίηση αλγορίθμων δρομολόγησης για την εγκατάσταση και προστασία των πολυσημειακών συνδέσεων, σε αμιγώς οπτικά δίκτυα, λαμβάνοντας υπόψη τις επιδράσεις του φυσικού στρώματος. Αυτή η διατριβή γεμίζει ένα κενό που υπάρχει στην έρευνα, αναπτύσσοντας αποδοτικές λύσεις για αυτά τα προβλήματα σε μητροπολιτικά οπτικά δίκτυα με τοπολογία πλέγματος. Όλες οι τεχνικές που αναπτύχθηκαν για την δρομολόγηση, πολυπλεξία, και προστασία των πολυσημειακών συνδέσεων, σχεδιάστηκαν λαμβάνοντας υπόψιν τους περιορισμούς του φυσικού στρώματος και παρουσιάζουν σημαντική βελτίωση στην απόδοσή τους σε σχέση με τις προηγούμενες τεχνικές που έχουν αναπτυχθεί μέχρι τώρα. Σε αυτή την διατριβή παρουσιάζεται μια ολοκληρωμένη λύση για την εγκατάσταση και προστασία πολυσημειακών συνδέσεων σε αμιγώς οπτικά δίκτυα, μέσω της ανάπτυξης ενός μοντέλου για τον υπολογισμό των επιδράσεων του φυσικού στρώματος, της ανάπτυξης και σχεδιασμού κατάλληλων αρχιτεκτονικών κόμβων, καθώς και μέσω της ανάπτυξης και εκτίμησης ενός μεγάλου αριθμού ευριστικών αλγορίθμων που μπορούν να αυξήσουν την απόδοση αυτών των δικτύων. Ενώ αυτή η διατριβή επικεντρώνεται σε μητροπολιτικά οπτικά δίκτυα, οι μέθοδοι και τεχνικές που αναπτύσσονται σε αυτή την διατριβή μπορούν να εφαρμοστούν και σε άλλους τύπους δικτύων, δεδομένου ότι οι επιδράσεις του φυσικού στρώματος που σχετίζονται με αυτά τα δίκτυα λαμβάνονται υπόψη στην μοντελοποίηση του φυσικού στρώματος. Next-generation optical networks are expected to support traffic that will be heterogeneous in nature with both unicast, as well as multicast/groupcast applications. Recent bandwidth-intensive applications that are driving the use of optical multicasting include telepresence, grid computing, telemedicine, software and video distribution for residential customers, movie broadcasts, interactive distance learning and video training, and distributed games amongst others. In parallel to the emergence of high-bandwidth multicast applications, the trend is for next-generation mesh optical networks that are evolving from opaque to translucent, and eventually to transparent optical networks. These transparent networks are extremely desirable as they provide bit-rate, protocol, and modulation format transparency, thus providing better solutions in the implementation of the network architecture by minimizing the extra cost, power, and footprint associated with the additional transceivers present in an opaque architecture. These architectures must now also have the capability and build-in intelligence to efficiently support all types of traffic and all kinds of applications, including both unicast as well as multicast/groupcast applications that require either the entire or a fraction of the wavelength bandwidth. In telecommunications networks, it is also essential that services are provided in an uninterrupted manner, leveraging fault recovery techniques and intelligent switching nodes to protect the network against failures. Multicast applications that carry traffic to multiple destinations are even more susceptible to failures as a single failure can result in the loss of information destined to a large number of users. Thus, providing failure recovery techniques for the multicast applications is of paramount importance in next-generation optical networks. The objective of this dissertation is to investigate problems related to impairment-aware multicasting/groupcasting in metropolitan area mesh optical networks, when the physical layer impairments are also taken into consideration when designing and implementing the appropriate provisioning and protection techniques. The main contributions of this dissertation are in the design and implementation of provisioning and protection techniques for the impairment-aware support of multicast and groupcast applications in transparent optical networks. This dissertation fills an existing void in that area by formulating and developing efficient solutions for these problems in metropolitan area optical networks with mesh topologies. All techniques developed for wavelength routing, subrate grooming, and fault protection for multicast and groupcast applications in these networks were designed while taking into consideration the physical layer constraints, and by doing so they exhibited improved performance compared to all the rest of the previously developed techniques. This dissertation presents a complete treatment to the impairment-aware multicast and groupcast provisioning and fault recovery problem by investigating the physical layer system model, node architectures and network engineering, as well as designing and evaluating a large number of heuristic algorithms that can provide these network control functions in a simple and efficient manner. While this work focuses on metropolitan area networks, these methods and techniques can also be readily applicable to other types of networks as well, provided that the network-specific physical layer impairments are accounted for in the physical layer system model.

Graphene is a perfect two-dimensional (2D) carbon sheet in honeycomb lattice with unique, multi-faceted properties. Very recently plasmons have been identified in graphene thus opening a new research field called “graphene plasmonics” which provides a suitable alternative to noble-metal plasmonics, since the associated surface plasmons (SPs) exhibit much larger light confinement abilities and relatively long propagation distances, with the advantage of being highly tunable via electrostatic gating. Moreover graphene can be efficiently integrated in photonic nanostructures in order to increase the optical absorption in the visible and infrared regions (graphene photonics). In this paper we will illustrate some applications of graphene plasmonics and graphene photonics, reported in literature, in different research fields and we will review our recent numerical and experimental results concerning the linear and nonlinear optical response of graphene plasmonic and photonic nanostructures emphasizing their interaction in terms of absorption and optical resonances.

Made available in DSpace on 2016-04-04T18:31:36Z (GMT). No. of bitstreams: 1 Rodrigo Frandsen da Silva.pdf: 3782928 bytes, checksum: cd013447a70916926978a2ddc8e42dbb (MD5) Previous issue date: 2012-12-19 Pontif?cia Universidade Cat?lica de Campinas In this dissertation we evaluate a new technique that performs optical encryption of signals travelling through transparent optical networks (TON). It is, thus, intended to prevent eavesdroppers to capture and retrieve optical signals. The technique consists in dividing an optical signal into several spectral slices and applying different attenuation and delays to each of them. After this process the signal is again multiplexed and transmitted through the considered TON. At this point the signal is ideally unintelligible to any receiver who does not know the encryption key, i.e. the set of utilized attenuations and delays. To evaluate the strength of such key, we measure the bit error rate (Bit Error Rate, BER) of the encoded signal, BERC. Generally speaking, the higher BERC, the lower is the chance of the encrypted signal being decoded by an eavesdropper. At the authorized receiver side, signal is again divided into spectral slices which are subjected to a set of attenuations and delays that are complementary to the ones utilized as the encryption key. All slices are again multiplexed and, as a result, at the output of the decoder the original encoder input signal is ideally reconstructed. The quality of the decoded signal is measured by evaluating the BER of the decoded signal, BERd, which should be low enough to allow proper reception of the signal transmitted by the TON. Simulations with the software VPITransmissionMaker, VPIPhotonics Company Inc., were used to investigate the performance of the technique for different gains and delays. For the operation of spectral slicing, the profiles of the utilized filters were adjusted to represent the ones of state-of-the-art off-the-shelf equipment. Results indicate that BERC may reach values of up to 42% and 32% for non-return to zero (NRZ) and differential quadrature phase shift keying (DQPSK) signals, respectively. In both of these cases it was possible to find results of BERd lower than 10-12, after properly adjusting the spacing between the filters; this was observed even for propagation over amplified standard fiber links with lengths as long as 400 km. To the best of our knowledge, this is the first time that such analyses are presented. Neste trabalho avaliamos uma t?cnica para realizar a criptografia totalmente ?ptica em redes ?pticas transparentes. Dessa maneira, pretende-se impedir que um intruso consiga capturar e analisar o sinal ?ptico. A t?cnica consiste em dividir um sinal ?ptico em diversas fatias espectrais e aplicar diferentes atenua??es e atrasos a cada uma delas. Ap?s este processo o sinal ? novamente multiplexado e transmitido por uma rede ?ptica transparente. Neste ponto o sinal est? idealmente inintelig?vel para qualquer receptor que n?o conhe?a a chave criptogr?fica (conjunto de atenua??es e atrasos) utilizada. Para avaliar a for?a da chave criptogr?fica, mede-se a taxa de erros de bit (Bit Error Rate, BER) do sinal codificado, BERC. De forma geral, quanto maior BERC, menor ? a chance de o sinal ser decodificado por um receptor n?o autorizado. Na decodifica??o o sinal ? novamente dividido em fatias espectrais, e para todas as fatias s?o aplicados valores distintos de atenua??o e atraso de forma a reconstituir o sinal de entrada. Na sa?da do decodificador, avalia-se a BER do sinal decodificado BERD, que deve ser suficientemente baixa para permitir a recep??o do sinal transmitido pela TON. Simula??es com o software VPITransmissionMaker, da empresa VPIPhotonics Inc, foram utilizadas para investigar o desempenho da t?cnica para diferentes ganhos e atrasos. Para a opera??o de fatiamento espectral, os perfis dos filtros usados foram ajustados para representar equipamentos de mercado. Resultados indicam que BERC pode atingir valores de at? 42% e 32% para sinais com modula??o non return to zero - on-off keying (NRZ-OOK) e por deslocamento de fase diferencial em quadratura (differential quadrature phase shift keying, DQPSK), respectivamente. Em ambos os casos foi poss?vel encontrar resultados de BERd inferiores a 10-12, mediante ajuste adequado do espa?amento entre os filtros, mesmo ap?s 400 km de propaga??o por enlaces de fibra padr?o. No melhor de nosso conhecimento, esta ? a primeira vez que tais an?lises s?o apresentadas.

In transparent optical networks (TONs), all-optical channels, called lightpaths, are established between end nodes and transmission takes place without opto-electronic conversions or even signal interpretation at intermediate nodes. This makes TONs vulnerable to deliberate attacks targeting the physical layer, particularly high-power jamming. Jamming attacks are realized by injecting a high-power signal into the network with the objective to disrupt service on legitimate lightpaths via increased in-band crosstalk in switches, out-of-band crosstalk in fibers and/or gain competition in amplifiers. Such attacks can propagate through the network, potentially causing network-wide damage. Thwarting attack propagation or preventing their occurrence would require deployment of expensive specialized equipment, which might be economically unviable for the network operators. Since the spreading of attacks depends on the logical topology of the network, setting up lightpaths in an intelligent, attack-aware manner can increase network security from attacks. In order to enhance network security in the presence of jamming attacks and reduce the maximum potential damage in the network without using additional resources, in this thesis we propose new objective criteria and heuristic algorithms for preventive, attack-aware routing and wavelength assignment (RWA). In general, RWA consists of assigning a physical route and a wavelength to each lightpath and is most commonly aimed at minimizing resource, i.e., wavelength usage, which is kept as an additional objective in our proposed approach to be cost-effective. We first focus on the in-band effects of jamming signals in optical switches and develop wavelength assignment heuristics which consider limited and unlimited attack propagation. We then propose RWA heuristics which consider the compound in-band and out-of-band effects of jamming signals. Finally, we propose heuristic algorithms for network survivability in the presence of component faults and attacks by modeling attack relations among lightpaths via so-called attack groups and ensuring that the working and backup paths of each connection are attack group-disjoint. Compared to the existing RWA approaches from the literature, simulation results show that our proposed approaches significantly reduce the maximum potential damage from jamming attacks and improve physical-layer security while maintaining efficient resource utilization. U transparentnim optičkim mrezama zasnovanim na multipleksiranju s valnom podjelom komunikacija izmedu krajnjih čvorova odvija se putem sveoptičkih kanala, zvanih svjetlosnim putevima. Zbog odsutstva opto-elektroničke konverzije, a time i interpretacije signala u međučvorovima, takve su mreže ranjive na napade usmjerene na nedostatke fizičkog sloja mreže. Jedna od najopasnijih metoda napada je unošenje signala visoke snage u mrežu s ciljem degradacije kvalitete i/ili ometanja usluge na legitimnim signalima. Štetni efekti takvih signala uključuju pojačano unutarpojasno preslušavanje u optičkim prospojnicima, izvanpojasno preslušavanje u optičkim nitima te takozvano natjecanje pojačavanja između napadačkog i legitimnih signala unutar optičkih pojačala. Napadi koji iskorištavaju pojavu unutarpojasnog preslušavanja u prospojnicima posebno su štetni zbog mogućnosti prijenosa napadačkih svojstava s izvornog napadača na napadnute svjetlosne puteve. Razmjeri štete od ovakvih napada uvelike ovise o arhitekturi mrežnih čvorova te fizičkoj i logičkoj topologiji mreže. Zbog niske učestalosti napada, operatori nisu spremni na velika ulaganja u specijaliziranu opremu kako bi povećali mrežnu sigurnost, no ovakvi napadi, ako se dogode, mogu izazvati ogromne gubitke. U ovom radu stoga predlažemo nove sigurnosne optimizacijske kriterije te ih, s ciljem povećanja mrežne sigurnosti spram napada na fizičkom sloju, ugrađujemo u jedan od najvažnijih problema mrežnog planiranja, problem usmjeravanja i dodjeljivanja valnih duljina. Taj se problem sastoji od pronalaska puta i dodjele valne duljine svakom zahtjevu za svjetlosnim putem. Najčešće je usmjeren na minimizaciju količine korištenih resursa, poput broja valnih duljina, a njegova se dva potproblema zbog svoje kompleksnosti često rješavaju slijedno. Radi smanjenja štete od unutarpojasnog preslušavanja u prospojnicima, najprije predlažemo heurističke algoritme za sigurnosno dodjeljivanje valnih duljina. Usmjereni su na minimizaciju kriterija koji mjeri broj konekcija koje svaka konekcija može napasti te razmatraju slučajeve ograničenog i neograničenog širenja napada. Potom predlažemo algoritme za sigurnosno usmjeravanje i dodjelu valnih duljina uz minimizaciju kriterija koji razmatra združene unutarpojasne i izvanpojasne efekte signala ometanja. Konačno, kako bismo osigurali preživljavanje u mreži u slučaju napada, predlažemo modeliranje mogućnosti međusobnih napada putem takozvanih grupa napada te algoritme za zaštitno usmjeravanje i/ili dodjelu valnih duljina koji za svaki radni put pronalaze zaštitni na način da su im grupe napada disjunktne. Sve heuristike u ovom radu, uz ograničavanje broja konekcija koje svaka konekcija može napasti, zadržavaju standardni cilj rješavanja problema usmjeravanja i dodjele valnih duljina, tj. minimiziraju broj korištenih valnih duljina kao sekundarni cilj. Navedeni algoritmi su implementirani u obliku programskog alata te evaluirani pomoću simulacija na različitim prometnim instancama europskih i američkih mrežnih topologija. Usporedbe s postojećim algoritmima pokazuju da predloženi heuristički algoritmi povećavaju sigurnost mreže spram napada usmjerenih na fizički sloj na ekonomičan način.

Made available in DSpace on 2016-04-04T18:31:33Z (GMT). No. of bitstreams: 1 Luiz Antonio Fossaluzza junior.pdf: 4580835 bytes, checksum: 4fdd68a1c6733e08c016db3e5dd34d0b (MD5) Previous issue date: 2012-11-23 This work investigates a technique to encrypt the optical signal for Transparent Optical Network, TON, in order to safeguard the confidentiality and guarantee the security of informations that are transmitted through the Telecommunications Network. The technique is assessed on the physical layer of the reference model for open systems interconnection, OSI, and consists of slicing spectrally optical signal and to apply various attenuations and delays to each of the slices spectral considered. These slices are multiplexed and the resulting signal, which will be propagated by an optical network transparent, it will be ideally unintelligible to eavesdropper who try to steals it. At this point is possible to evaluate the quality of the encryption used by measuring the output of the encoder the bit error rate, BER, the encrypted signal, BERC. In principle, as highest BERC,it will be lowest the probability of an eavesdropper decode the signal. To get to your destination, the signal is received in the decoder circuit, which has the same physical structure of the circuit which encoded the original signal. The application of the factors of attenuation and delay in this distorted signal is adjusted for the reconstruction of optical signal generated by the transmitter. On the output of decoder, performs the measurement of BER of signal decoded, the BERD. Ideally, BERD must be the lowest possible. For technique evaluation, it was simulated, with the version 8.7 of the software VPITransmissionMaker, of company VPIPhotonics Inc, the operation of the devices of cryptography, propagation and the elements of decoded signal. All simulations considered that the spectral slicing was carried out by means of filters with ideal profile. The results indicates that the BERC may reach up to 42% and 24%, to encrypted signals with modulation on-off Keying non return to zero (NRZ-OOK) and differential quadrature phase shift keying (DQPSK) respectively, and that both are free of errors (BERD< 10-15 for the signal NRZ-OOK and BERD< 10-6 for DQPSK modulation) when decoded. Este trabalho aborda uma t?cnica para criptografar o sinal ?ptico em redes ?pticas transparentes (Transparent Optical Network, TON), de modo a salvaguardar o sigilo e garantir a seguran?a das informa??es que s?o transmitidas atrav?s da Rede de Telecomunica??es. A t?cnica avaliada ? relativa ? camada f?sica do modelo de refer?ncia para interconex?o de sistemas abertos (open systems interconnection, OSI) e consiste em dividir espectralmente um sinal ?ptico e em aplicar diferentes atenua??es e atrasos a cada uma das fatias espectrais consideradas. A seguir essas fatias s?o multiplexadas e o sinal resultante, que ser? propagado por uma rede ?ptica transparente, estar? idealmente inintelig?vel para intrusos que tentem furt?-lo. Nesse ponto ? poss?vel avaliar a qualidade da criptografia utilizada, medindo-se na sa?da do codificador a taxa de erro de bit (bit error rate, BER) do sinal criptografado, BERC. Em princ?pio, quanto maior BERC, menor a probabilidade de um intruso decodificar o sinal. Ao chegar ao seu destino, o sinal ? recebido no circuito decodificador, que possui a mesma estrutura f?sica do circuito que codificou o sinal original. A aplica??o dos fatores de atenua??o e atraso neste sinal distorcido ? ajustada para a reconstru??o do sinal ?ptico gerado pelo transmissor. Na sa?da do decodificador, efetua-se a medi??o da BER do sinal decodificado, BERD. Idealmente, BERD deve ser a menor poss?vel. Para avalia??o da t?cnica, simulou-se, com a vers?o 8.7 do software VPITransmissionMaker, da empresa VPIPhotonics Inc, a opera??o dos dispositivos de criptografia, da propaga??o e dos elementos de decriptografia do sinal. Todas as simula??es consideraram que o fatiamento espectral foi realizado por meio de filtros com perfil ideal. Os resultados indicam que a BERC pode atingir at? 42% e 24%, para sinais codificados com modula??o n?o retorno ao zero com chaveamento on-off (non return to zero on-off keying, NRZ-OOK) e por deslocamento de fase diferencial em quadratura (differential quadrature phase shift keying, DQPSK) respectivamente, e que ambos n?o apresentam erros (BERD< 10-15 para o sinal NRZ-OOK e BERD< 10-6 para a modula??o DQPSK) quando decodificados.

The continuous growth of traffic demand driven by the brisk increase in number of Internet users and emerging online services creates new challenges for communication networks. The latest advances in Wavelength Division Multiplexing (WDM) technology make it possible to build Transparent Optical Networks (TONs) which are expected to be able to satisfy this rapidly growing capacity demand. Moreover, with the ability of TONs to transparently carry the optical signal from source to destination, electronic processing of the tremendous amount of data can be avoided and optical-to-electrical-to-optical (O/E/O) conversion at intermediate nodes can be eliminated. Consequently, transparent WDM networks consume relatively low power, compared to their electronic-based IP network counterpart. Furthermore, TONs bring also additional benefits in terms of bit rate, signal format, and protocol transparency. However, the absence of O/E/O processing at intermediate nodes in TONs has also some drawbacks. Without regeneration, the quality of the optical signal transmitted from a source to a destination might be degraded due to the effect of physical-layer impairments induced by the transmission through optical fibers and network components. For this reason, routing approaches specifically tailored to account for the effect of physical-layer impairments are needed to avoid setting up connections that don’t satisfy required signal quality at the receiver. Transparency also makes TONs highly vulnerable to deliberate physical-layer attacks. Malicious attacking signals can cause a severe impact on the traffic and for this reason proactive mechanisms, e.g., network design strategies, able to limit their effect are required. Finally, even though energy consumption of transparent WDM networks is lower than in the case of networks processing the traffic at the nodes in the electronic domain, they have the potential to consume even less power. This can be accomplished by targeting the inefficiencies of the current provisioning strategies applied in WDM networks. The work in this thesis addresses the three important aspects mentioned above. In particular, this thesis focuses on routing and wavelength assignment (RWA) strategies specifically devised to target: (i) the lightpath transmission quality, (ii) the network security (i.e., in terms of vulnerability to physical-layer attacks), and (iii) the reduction of the network energy consumption. Our contributions are summarized below. A number of Impairment Constraint Based Routing (ICBR) algorithms have been proposed in the literature to consider physical-layer impairments during the connection provisioning phase. Their objective is to prevent the selection of optical connections (referred to as lightpaths) with poor signal quality. These ICBR approaches always assign each connection request the least impaired lightpath and support only a single threshold of transmission quality, used for all connection requests. However, next generation networks are expected to support a variety of services with disparate requirements for transmission quality. To address this issue, in this thesis we propose an ICBR algorithm supporting differentiation of services at the Bit Error Rate (BER) level, referred to as ICBR-Diff. Our approach takes into account the effect of physical-layer impairments during the connection provisioning phase where various BER thresholds are considered for accepting/blocking connection requests, depending on the signal quality requirements of the connection requests. We tested the proposed ICBR-Diff approach in different network scenarios, including also a fiber heterogeneity. It is shown that it can achieve a significant improvement of network performance in terms of connection blocking, compared to previously published non-differentiated RWA and ICBR algorithms. Another important challenge to be considered in TONs is their vulnerability to physical-layer attacks. Deliberate attacking signals, e.g., high-power jamming, can cause severe service disruption or even service denial, due to their ability to propagate in the network. Detecting and locating the source of such attacks is difficult, since monitoring must be done in the optical domain, and it is also very expensive. Several attack-aware RWA algorithms have been proposed in the literature to proactively reduce the disruption caused by high-power jamming attacks. However, even with attack-aware network planning mechanisms, the uncontrollable propagation of the attack still remains an issue. To address this problem, we propose the use of power equalizers inside the network nodes in order to limit the propagation of high-power jamming attacks. Because of the high cost of such equipment, we develop a series of heuristics (incl. Greedy Randomized Adaptive Search Procedure (GRASP)) aiming at minimizing the number of power equalizers needed to reduce the network attack vulnerability to a desired level by optimizing the location of the equalizers. Our simulation results show that the equalizer placement obtained by the proposed GRASP approach allows for 50% reduction of the sites with the power equalizers while offering the same level of attack propagation limitation as it is possible to achieve with all nodes having this additional equipment installed. In turn, this potentially yields a significant cost saving. Energy consumption in TONs has been the target of several studies focusing on the energy-aware and survivable network design problem for both dedicated and shared path protection. However, survivability and energy efficiency in a dynamic provisioning scenario has not been addressed. To fill this gap, in this thesis we focus on the power consumption of survivable WDM network with dynamically provisioned 1:1 dedicated path protected connections. We first investigate the potential energy savings that are achievable by setting all unused protection resources into a lower-power, stand-by state (or sleep mode) during normal network operations. It is shown that in this way the network power consumption can be significantly reduced. Thus, to optimize the energy savings, we propose and evaluate a series of energy-efficient strategies, specifically tailored around the sleep mode functionality. The performance evaluation results reveal the existence of a trade-off between energy saving and connection blocking. Nonetheless, they also show that with the right provisioning strategy it is possible to save a considerable amount of energy with a negligible impact on the connection blocking probability. In order to evaluate the performance of our proposed ICBR-Diff and energy-aware RWA algorithms, we develop two custom-made discrete-event simulators. In addition, the Matlab program of GRASP approach for power equalization placement problem is implemented. QC 20120508

We review our advances in diffractive and subwavelength grating coupler structures for microphotonic waveguides. We present a subwavelength grating fiber-chip edge coupler with a loss as low as 0.9 dB and with minimal wavelength dependence over a broad wavelength range exceeding 200 nm. We also present fiber-to-chip surface grating couplers based on subwavelength effective medium. The effective medium refractive index is engineered to control the strength of the grating and thereby maximize coupling efficiency, while mitigating back reflections at the same time. We analyze the fabrication tolerances of the coupler, which are of particular relevance for large scale photonic fabrication. Furthermore, we present the first grating coupler for micrometric silicon rib waveguides, which is particularly challenging since the coupler waveguide region is multimode. We experimentally demonstrate grating couplers in 1.5 μm thick silicon ridge waveguides with a coupling efficiency of 2.2 dB and a 3 dB bandwidth of 40 nm. An inverse taper is used to match the fundamental mode of the interconnection waveguide with the optimum grating coupler excitation field, with negligible higher order mode excitation. The coupler was fabricated using i-line stepper lithography and single etch step. © 2012 IEEE., 14th International Conference on Transparent Optical Networks, ICTON 2012, 2 July 2012 through 5 July 2012, Coventry

When an optical signal propagates through optical fibers, the quality of the signal degrades due to a number of physical phenomena. Traditional Routing and Wavelength Assignment (RWA) approaches assume an ideal physical layer medium and ignore the effects of physical layer impairments on the lightpath feasibility. In the last few years investigators have started taking into account the fact that the quality of transmission (QoT) of an optical signal propagating through an optical network degrades, due to physical layer considerations. To measure the extent of this degradation due to physical layer impairments (PLI), metrics such as the Bit Error Rate (BER) used. In a translucent network, when the quality of a signal is reduced sufficiently, the signal has to be regenerated. In a transparent network, regenerators are not allowed so that lightpaths with high bit error rates are disallowed. A number of heuristic approaches for impairment aware RWA have been proposed for transparent and for translucent networks. As a result of this investigation a test-bed ahs been developed for Impairment Aware Static Route and Wavelength Assignment (IA-RWA) in transparent networks. This includes a tool for computing BER values and allows the user to run a new heuristic for IA-RWA and study its performance against a number of existing heuristics for IA-RWA.

We present the development of a compact planar waveguide Fourier-transform spectrometer for high-resolution and high-throughput spectroscopy. The prototype device is designed to monitor the water vapor absorption band near λ= 1364 nm in the atmosphere from an Earth-orbiting satellite. The instrument is fully static (i.e. no moving parts) and it is based on a unique slab waveguide Fourier-transform spectrometer concept implemented with silicon-on-insulator (SOI) technology. The spectrometer input is formed by an array of N independent waveguide apertures, thereby significantly (Nx) increasing light gathering capability (étendue) compared to conventional single-aperture devices. We also discuss a practical implementation of the multi-aperture concept based on an array of surface grating couplers. © 2011 IEEE., 2011 13th International Conference on Transparent Optical Networks, ICTON 2011, 26 June 2011 through 30 June 2011, Stockholm

Summary form only given. Transparent optical networks (TONs) based on Wavelength Division Multiplexing (WDM) are the only viable future-proof solution for supporting rapidly growing traffic demands. In TONs, optical signals are propagated transparently between edge nodes without any O/E/O conversion. In this way, it is possible to reduce cost and energy consumption in the network, as well as obtain transparency to signal bit rates, modulation formats and protocols. However, the absence of O/E/O conversion makes it easier for erroneous signals to propagate through the network and affect existing traffic.