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Velasco L.,Polytechnic University of Catalonia | Klinkowski M.,National Institute of Telecommunications NIT | Ruiz M.,Polytechnic University of Catalonia | Comellas J.,Polytechnic University of Catalonia
Photonic Network Communications | Year: 2012

Flexgrid optical networks are attracting huge interest due to their higher spectrum efficiency and flexibility in comparison with traditional wavelength switched optical networks based on the wavelength division multiplexing technology. To properly analyze, design, plan, and operate flexible and elastic networks, efficient methods are required for the routing and spectrum allocation (RSA) problem. Specifically, the allocated spectral resources must be, in absence of spectrum converters, the same along the links in the route (the continuity constraint) and contiguous in the spectrum (the contiguity constraint). In light of the fact that the contiguity constraint adds huge complexity to the RSA problem, we introduce the concept of channels for the representation of contiguous spectral resources. In this paper, we show that the use of a pre-computed set of channels allows considerably reducing the problem complexity. In our study, we address an off-line RSA problem in which enough spectrum needs to be allocated for each demand of a given traffic matrix. To this end, we present novel integer lineal programming (ILP) formulations of RSA that are based on the assignment of channels. The evaluation results reveal that the proposed approach allows solving the RSA problem much more efficiently than previously proposed ILP-based methods and it can be applied even for realistic problem instances, contrary to previous ILP formulations. © Springer Science+Business Media, LLC 2012. Source


Perello J.,Polytechnic University of Catalonia | Walkowiak K.,Wroclaw University of Technology | Klinkowski M.,National Institute of Telecommunications NIT | Spadaro S.,Polytechnic University of Catalonia | Careglio D.,Polytechnic University of Catalonia
Computer Communications | Year: 2016

In this work, we address the problem of jointly deciding the placement of the contents delivered by a Content Distribution Network (CDN) among the available data centers, together with the allocation of the lightpaths required to serve the anycast demands initiated by the CDN network users, assuming an underlying high-capacity Elastic Optical Network (EON). We firstly present an Integer Linear Programming (ILP) formulation to optimally solve the targeted problem. This ILP formulation is of high complexity, though, and cannot be used to solve realistically sized problem instances. Hence, we also introduce a novel heuristic called CPRMSA-PD, which decomposes the problem into three sub-problems and applies greedy heuristics and simulated annealing meta-heuristic techniques to yield accurate solutions with practical execution times. We validate the performance of our CPRMSA-PD heuristic in medium-sized problem instances by comparing its results to the ones of the optimal ILP formulation. Next, we use it to give extensive insights into the effects of different key parameters identified in large CDN over EON backbone networks. © 2015 Elsevier B.V. All rights reserved. Source


Azodolmolky S.,Polytechnic University of Catalonia | Azodolmolky S.,Athens Information Technology | Klinkowski M.,National Institute of Telecommunications NIT | Pointurier Y.,Athens Information Technology | And 5 more authors.
Journal of Lightwave Technology | Year: 2010

Physical layer impairments accumulate as light propagates through a lightpath in the transparent optical networks. Therefore, it is possible to provision a lightpath, while its quality of transmission (QoT) does not meet the required threshold. Considering the physical layer impairments in the network planning phase gives rise to a set of offline Impairments Aware Routing and Wavelength Assignment (IA-RWA) algorithms. There are very few offline IA-RWA algorithms that consider dedicated path protection demands. In this work we propose a novel offline IA-RWA algorithm, called Rahyab and perform a comparative performance evaluation study, which considers two enhanced algorithms from the literature. Simulation results indicates that demand pre-processing, diverse routing, and adaptive wavelength assignment are the main reasons of lower blocking rate of Rahyab algorithm compared to the selected algorithms. © 2010 IEEE. Source


Pedrola O.,Polytechnic University of Catalonia | Careglio D.,Polytechnic University of Catalonia | Klinkowski M.,National Institute of Telecommunications NIT | Sole-Pareta J.,Polytechnic University of Catalonia
16th European Conference on Networks and Optical Communications, NOC 2011 | Year: 2011

The deployment of translucent optical networks is considered the most promising short term solution to decrease costs and energy consumption in optical backbone networks. Indeed, due to the technological maturity of translucent wavelength switched optical network (WSON) architectures, they have already caught close attention from the research community. Moreover, recent advances and enhancements in optical devices are now (re-)fostering research interest in sub-wavelength technologies like, among others, optical burst switching (OBS) and optical packet switching (OPS). Hence, in this paper, we evaluate and compare two novel node architectures for a translucent OBS (T-OBS) network. To be precise, we study nodes with both dedicated and shared wavelength converter resources (i.e., DWC and SWC). To this end, we consider the impact of the main physical layer impairments (PLIs) and make use of a routing and regenerator placement and dimensioning (RRPD) algorithm to minimize the number of optical-electrical-optical (O/E/O) regenerators deployed in the network whilst, at the same time, guaranteeing a target quality of transmission (QoT) network performance. The results presented prove the feasibility and the significant savings, in terms of the number of wavelength converters (WCs), that can be achieved by considering a network with shared wavelength converter resources. © 2011 IEEE. Source


Borzycki K.,National Institute of Telecommunications NIT | Schuster K.,Institute of Photonic Technology
Proceedings of the International Conference on Advanced Optoelectronics and Lasers, CAOL | Year: 2013

Characterization of two single mode silica photonic crystal fibers strongly doped with GeO2 included also arc fusion splicing to standard single mode fibers for connections to test instruments, made successfully with machine designed for telecom fibers. Tested with OTDR, both fibers exhibited very strong backscattering and fairly high attenuation: 45-70 dB/km at 1310 nm and 1550 nm. Despite very similar design, their polarization mode dispersion (PMD) differed significantly (1127 ps/km and 118 ps/km) and was apparently produced by different mechanisms, as suggested by dependence on temperature and fiber twist. © 2013 IEEE. Source

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