355 research outputs found
Reconfigurable Reflectarrays and Array Lenses for Dynamic Antenna Beam Control: A Review
Advances in reflectarrays and array lenses with electronic beam-forming
capabilities are enabling a host of new possibilities for these
high-performance, low-cost antenna architectures. This paper reviews enabling
technologies and topologies of reconfigurable reflectarray and array lens
designs, and surveys a range of experimental implementations and achievements
that have been made in this area in recent years. The paper describes the
fundamental design approaches employed in realizing reconfigurable designs, and
explores advanced capabilities of these nascent architectures, such as
multi-band operation, polarization manipulation, frequency agility, and
amplification. Finally, the paper concludes by discussing future challenges and
possibilities for these antennas.Comment: 16 pages, 12 figure
Recommended from our members
Real-time Awareness and Fast Reconguration Capabilities for Agile Optical Networks
Ever-growing demand for speed and bandwidth coupled with increasing energy consumption in current networks are driving the need for intelligent, next-generation networking architectures that can overcome fundamental spectral and energy limitations. Metro-only internet traffic in particular is experiencing unprecedented growth rates and increasing twice as fast as long-haul traffic. The current quasi-static peak capacity pro- visioned network is ill-equipped to support this rise of unpredictable, high bandwidth but short-duration traffic flows. A promising solution to address the emerging networking challenges is agile optical networking. Agile optical networking leverages novel photonic devices and multi-layer switching capabilities along with network awareness and intelligence to allocate re- sources in accordance to changing traffic demands and network conditions. However, network agility requires changing the wavelength configuration in the optical layer in real-time to match the traffic demands. Rapidly changing the wavelength loading conditions in optical amplifiers result in debilitating power fluctuations that propagate through the network and can lead to network instability, a problem that is avoided in current networks by using long reconfiguration times encompassing many small adjustments. An agile optical network, once successfully implemented, will be characterized by unpredictable transmission impairments. Power levels along any path in an agile network is constantly fluctuating due to the continuously changing wavelength configuration; consequently, power dependent transmission impairments are also constantly fluctuating. Real-time knowledge of the state of the physical layer is thus critical for managing signal quality and reliability in an agile optical network, requiring the development of cost-effective, energy-efficient monitoring solutions that can support advanced modulation formats. This dissertation focuses on developing solutions for the two key requirements for a stable agile optical network. Techniques that allow wavelength reconguration on the order of seconds while maintaining stable network operation and minimal data loss are presented. Functionality of an existing advanced optical performance monitor is extended to include autonomous monitoring of both single and multiple channel systems, so that it can be used in agile optical network for real-time introspection of the physical layer
Q-Band Millimeter-Wave Antennas: An Enabling Technology for MultiGigabit Wireless Backhaul
[EN] The bandwidth demands in mobile communication systems are growing exponentially day by day as the number of users has increased drastically over the last five years. This mobile data explosion, together with the fixed service limitations, requires a new approach to support this increase in bandwidth demand. Solutions based on lower-frequency microwave wireless systems may be able to meet the bandwidth demand in a short term. However, with the small-cell mass deployment requiring total capacities of 1 Gb/s/km2, scalable, multigigabit backhaul systems are required. Millimeter-wave technology fits nicely into these new backhaul scenarios as it provides extended bandwidth for high-capacity links and adaptive throughput rate, which allows efficient and flexible deployment. Besides these advantages, millimeter-wave solutions become even more attractive when the cost of backhaul solutions and the cost of spectrum licenses are factored in. Compared to the cost of laying fiber to a cell base station, which is the only other scalable solution, the millimeter-wave solution becomes the most appropriate approach.The research leading to these results received funding from the European Commission's seventh Framework Programme under grant agreement 288267.Vilar Mateo, R.; Czarny, R.; Lee, ML.; Loiseaux, B.; Sypek, M.; Makowski, M.; Martel, C.... (2014). Q-Band Millimeter-Wave Antennas: An Enabling Technology for MultiGigabit Wireless Backhaul. IEEE Microwave Magazine. 15(4):121-130. https://doi.org/10.1109/MMM.2014.2308769S12113015
Wavelength tunable transmitters for future reconfigurable agile optical networks
Wavelength tuneable transmission is a requirement for future reconfigurable agile optical networks as it enables cost efficient bandwidth distribution and a greater degree of transparency. This thesis focuses on the development and characterisation of wavelength tuneable transmitters for the core, metro and access based WDM networks.
The wavelength tuneable RZ transmitter is a fundamental component for the core network as the RZ coding scheme is favoured over the conventional NRZ format as the line rate increases. The combination of a widely tuneable SG DBR laser and an EAM is a propitious technique employed to generate wavelength tuneable pulses at high repetition
rates (40 GHz). As the EAM is inherently wavelength dependant an accurate characterisation of the generated pulses is carried out using the linear spectrogram
measurement technique. Performance issues associated with the transmitter are investigated by employing the generated pulses in a 1500 km 42.7 Gb/s circulating loop
system. It is demonstrated that non-optimisation of the EAM drive conditions at each operating wavelength can lead to a 33 % degradation in system performance. To achieve
consistent operation over a wide waveband the drive conditions of the EAM must be altered at each operating wavelength.
The metro network spans relatively small distances in comparison to the core and therefore must utilise more cost efficient solutions to transmit data, while also
maintaining high reconfigurable functionality. Due to the shorter transmission distances, directly modulated sources can be utilised, as less precise wavelength and chirp control can be tolerated. Therefore a gain-switched FP laser provides an ideal source for wavelength tuneable pulse generation at high data rates (10 Gb/s). A self-seeding scheme that generates single mode pulses with high SMSR (> 30 dB) and small pulse duration is demonstrated. A FBG with a very large group delay disperses the generated pulses and subsequently uses this CW like signal to re-inject the laser diode negating the need to tune the repetition rate for optimum gain-switching operation.
The access network provides the last communication link between the customerâs premises and the first switching node in the network. FTTH systems should take advantage of directly modulated sources; therefore the direct modulation of a SG DBR tuneable laser is investigated. Although a directly modulated TL is ideal for reconfigurable access based networks, the modulation itself leads to a drift in operating frequency which may result in cross channel interference in a WDM network. This effect is investigated and also a possible solution to compensate the frequency drift through simultaneous modulation of the lasers phase section is examined
Recommended from our members
24 [1Ă12] Wavelength Selective Switches Integrated on a Single 4k LCoS Device
This article demonstrates the design, assembly, optimisation, and characterisation of 24 [1 Ă 12] wavelength selective switches (WSSs) based on a single set of optics and a 4k liquid crystal on silicon (LCoS) device. The average insertion loss was measured to be 8.4 dB with an average crosstalk level of 26.9 dB. To our knowledge, this module with 312 fibre ports is the highest-capacity WSS demonstrated so far. The module can be flexibly reconfigured into different switches and port counts for advanced reconfigurable optical add/drop multiplexer (ROADM) applications
Experimental demonstration of flexible bandwidth networking with real-time impairment awareness
We demonstrate a flexible-bandwidth network testbed with a real-time, adaptive control plane that adjusts modulation format and spectrum-positioning to maintain quality of service (QoS) and high spectral efficiency. Here, low-speed supervisory channels and field-programmable gate arrays (FPGAs) enabled real-time impairment detection of high-speed flexible bandwidth channels (flexpaths). Using premeasured correlation data between the supervisory channel quality of transmission (QoT) and flexpath QoT, the control plane adapted flexpath spectral efficiency and spectral location based on link quality. Experimental demonstrations show a back-to-back link with a 360-Gb/s flexpath in which the control plane adapts to varying link optical signal to noise ratio (OSNR) by adjusting the flexpath's spectral efficiency (i.e., changing the flexpath modulation format) between binary phase-shift keying (BPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK). This enables maintaining the data rate while using only the minimum necessary bandwidth and extending the OSNR range over which the bit error rate in the flexpath meets the quality of service (QoS) requirement (e. g. the forward error correction (FEC) limit). Further experimental demonstrations with two flexpaths show a control plane adapting to changes in OSNR on one link by changing the modulation format of the affected flexpath (220 Gb/s), and adjusting the spectral location of the other flexpath (120 Gb/s) to maintain a defragmented spectrum. (C) 2011 Optical Society of Americ
Planification et dimensionnement des réseaux optiques de longues distances
Le projet de recherche porte sur l'Ă©tude des problĂšmes de conception et de planification d'un rĂ©seau optique de longue distance, aussi appelĂ© rĂ©seau de coeur (OWAN-Optical Wide Area Network en anglais). Il s'agit d'un rĂ©seau qui transporte des flots agrĂ©gĂ©s en mode commutation de circuits. Un rĂ©seau OWAN relie diffĂ©rents sites Ă l'aide de fibres optiques connectĂ©es par des commutateurs/routeurs optiques et/ou Ă©lectriques. Un rĂ©seau OWAN est maillĂ© Ă l'Ă©chelle d'un pays ou dâun continent et permet le transit des donnĂ©es Ă trĂšs haut dĂ©bit. Dans une premiĂšre partie du projet de thĂšse, nous nous intĂ©ressons au problĂšme de conception de rĂ©seaux optiques agiles. Le problĂšme d'agilitĂ© est motivĂ© par la croissance de la demande en bande passante et par la nature dynamique du trafic. Les Ă©quipements dĂ©ployĂ©s par les opĂ©rateurs de rĂ©seaux doivent disposer d'outils de configuration plus performants et plus flexibles pour gĂ©rer au mieux la complexitĂ© des connexions entre les clients et tenir compte de la nature Ă©volutive du trafic. Souvent, le problĂšme de conception
d'un réseau consiste à prévoir la bande passante nécessaire pour écouler un trafic
donné. Ici, nous cherchons en plus à choisir la meilleure configuration nodale ayant un niveau d'agilité capable de garantir une affectation optimale des ressources du réseau.
Nous étudierons également deux autres types de problÚmes auxquels un opérateur de
réseau est confronté. Le premier problÚme est l'affectation de ressources du réseau. Une fois que l'architecture du réseau en termes d'équipements est choisie, la question qui reste est de savoir : comment dimensionner et optimiser cette architecture pour qu'elle rencontre le meilleur niveau possible d'agilité pour satisfaire toute la demande. La définition
de la topologie de routage est un problĂšme d'optimisation complexe. Elle consiste
à définir un ensemble de chemins optiques logiques, choisir les routes physiques suivies par ces derniers, ainsi que les longueurs d'onde qu'ils utilisent, de maniÚre à optimiser la qualité de la solution obtenue par rapport à un ensemble de métriques pour mesurer la performance du réseau. De plus, nous devons définir la meilleure stratégie de dimensionnement
du réseau de façon à ce qu'elle soit adaptée à la nature dynamique du trafic. Le second problÚme est celui d'optimiser les coûts d'investissement en capital(CAPEX) et d'opération (OPEX) de l'architecture de transport proposée. Dans le cas du type d'architecture de dimensionnement considérée dans cette thÚse, le CAPEX inclut
les coûts de routage, d'installation et de mise en service de tous les équipements de type réseau installés aux extrémités des connexions et dans les noeuds intermédiaires. Les coûts d'opération OPEX correspondent à tous les frais liés à l'exploitation du réseau de transport.
Ătant donnĂ© la nature symĂ©trique et le nombre exponentiel de variables dans la plupart des formulations mathĂ©matiques dĂ©veloppĂ©es pour ces types de problĂšmes, nous avons particuliĂšrement explorĂ© des approches de rĂ©solution de type gĂ©nĂ©ration de colonnes et algorithme glouton qui s'adaptent bien Ă la rĂ©solution des grands problĂšmes d'optimisation.
Une Ă©tude comparative de plusieurs stratĂ©gies d'allocation de ressources et d'algorithmes de rĂ©solution, sur diffĂ©rents jeux de donnĂ©es et de rĂ©seaux de transport de type OWAN dĂ©montre que le meilleur coĂ»t rĂ©seau est obtenu dans deux cas : une stratĂ©gie de dimensionnement anticipative combinĂ©e avec une mĂ©thode de rĂ©solution de type gĂ©nĂ©ration de colonnes dans les cas oĂč nous autorisons/interdisons le dĂ©rangement des connexions dĂ©jĂ Ă©tablies. Aussi, une bonne rĂ©partition de l'utilisation des ressources du rĂ©seau est observĂ©e avec les scĂ©narios utilisant une stratĂ©gie de dimensionnement myope combinĂ©e Ă une approche d'allocation de ressources avec une rĂ©solution utilisant les techniques de gĂ©nĂ©ration de colonnes.
Les résultats obtenus à l'issue de ces travaux ont également démontré que des gains
considĂ©rables sont possibles pour les coĂ»ts d'investissement en capital et d'opĂ©ration. En effet, une rĂ©partition intelligente et hĂ©tĂ©rogĂšne de ressources dâun rĂ©seau sur l'ensemble des noeuds permet de rĂ©aliser une rĂ©duction substantielle des coĂ»ts du rĂ©seau par rapport Ă une solution d'allocation de ressources classique qui adopte une architecture homogĂšne utilisant la mĂȘme configuration nodale dans tous les noeuds. En effet, nous avons dĂ©montrĂ© qu'il est possible de rĂ©duire le nombre de commutateurs photoniques tout en
satisfaisant la demande de trafic et en gardant le coût global d'allocation de ressources de réseau inchangé par rapport à l'architecture classique. Cela implique une réduction substantielle des coûts CAPEX et OPEX. Dans nos expériences de calcul, les résultats démontrent que la réduction de coûts peut atteindre jusqu'à 65% dans certaines jeux de données et de réseau.The research project focuses on the design and planning problems of long distance optical networks also called OWANs (Optical Wide Area Networks) or "backbone". These
are networks that carry aggregate flows in circuit switching mode. OWAN networks connect sites with optical fibers, cross-connected by optical and/or electric switches/routers. OWAN networks are meshed throughout a country or continent and allow the transit of data at very high speed.
In the first part of the thesis, we are interested in the design problem of agile optical networks. The problem of agility is motivated by the growing of bandwidth demand and by the dynamic pattern of client traffic. Equipment deployed by network operators must allow greater reconfigurability and scalability to manage the complexity of connections among clients and deal with a dynamic traffic pattern. Often, the problem of network design is to provide the required bandwidth to grant a given traffic pattern. Here, we seek to choose the best nodal configuration with the agility level that can guarantee the
optimal network resource provisioning.
We will also study two other types of problems that can face a network operator.
The first problem is the network resource provisioning. Once the network architecture
design is chosen, the remaining question is : How to resize and optimize the architecture to meet the agility level required to grant any demand. The definition of the network provisioning scheme is a complex optimization problem. It consists of defining a set of optical paths, choosing the routes followed by them, and their assigned wavelengths,
so as to optimize the solution quality with respect to some network metrics. Moreover,
we need to define the best design strategy adapted to the dynamic traffic pattern. The
second problem is to optimize the capital investment cost (CAPEX) and the operational
expenses (OPEX) of the selected optical transport architecture. In the case of the design architecture considered in this thesis, the CAPEX includes the routing cost, the installation cost and the commissioning service cost for all required network equipment in end connections and intermediate nodes. OPEX correspond to expenses related to the operation of the transport network. Given the symmetrical nature and the exponential number of variables in most mathematical formulations developed for these types of problems, we particularly explored solving approaches based on a column generation algorithm and greedy heuristics which adapt well to these types of modeling and large scale mathematical models.
A comparative study of several provisioning strategies and solution algorithms on
different traffic and OWAN network instances show that the minimum network cost is obtained in two cases : An anticipative dimensioning strategy combined with a column generation solution combined with a rounding off heuristic in the context of no disturbance or possible disturbance of previously granted connections. Also, a good repartition
of used network resources (MSPPs, PXC and wavelengths) is observed with the scenarios using a myopic strategy and a column generation solution approach.
The results obtained from this thesis also show that a considerable saving in CAPEX
and OPEX costs are possible in the case of an intelligent allocation and heteregenous
distribution of network resources through network nodes compared with the classical
architecture that adopts a uniform architecture using the same configuration in all nodes.
Indeed, we demonstrated that it is possible to reduce the number of PXCs (Photonic
Switches) while satisfying the traffic matrix and keeping the overall cost of provisioning network unchanged compared to what is happening in a classic architecture. This implies a substantial reduction in network CAPEX and OPEX costs. In our experiments with various network and traffic instances, we show that a careful dimensioning and location of the nodal equipment can save up to 65% of network expenses
Control plane routing in photonic networks
The work described in the thesis investigates the features of control plane functionality for routing wavelength paths to serve a set of sub-wavelength demands. The work takes account of routing problems only found in physical network layers, notably analogue transmission impairments. Much work exists on routing connections for dynamic Wavelength-Routed Optical Networks (WRON) and to demonstrate their advantages over static photonic networks. However, the question of how agile the WRON should be has not been addressed quantitatively. A categorization of switching speeds is extended, and compared with the reasons for requiring network agility. The increase of effective network capacity achieved with increased agility is quantified through new simulations. It is demonstrated that this benefit only occurs within a certain window of network fill; achievement of significant gain from a more-agile network may be prevented by the operatorâs chosen tolerable blocking probability. The Wavelength Path Sharing (WPS) scheme uses semi-static wavelengths to form unidirectional photonic shared buses, reducing the need for photonic agility. Making WPS more practical, novel improved routing algorithms are proposed and evaluated for both execution time and performance, offering significant benefit in speed at modest cost in efficiency. Photonic viability is the question of whether a path that the control plane can configure will work with an acceptable bit error rate (BER) despite the physical transmission impairments encountered. It is shown that, although there is no single approach that is simple, quick to execute and generally applicable at this time, under stated conditions approximations may be made to achieve a general solution that will be fast enough to enable some applications of agility. The presented algorithms, analysis of optimal network agility and viability assessment approaches can be applied in the analysis and design of future photonic control planes and network architectures
- âŠ