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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.


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.


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.


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.


Pedroso P.,Polytechnic University of Catalonia | Perello J.,Polytechnic University of Catalonia | Careglio D.,Polytechnic University of Catalonia | Klinkowski M.,National Institute of Telecommunications NIT | Spadaro S.,Polytechnic University of Catalonia
Journal of Optical Communications and Networking | Year: 2012

Over the past decade, the scientific community has thrown itself into assessing optical burst switching (OBS) as the switching technology for next-generation all-optical networks. In this regard, a significant amount of work has concentrated on providing OBS with the required carrier-class features. During this process, however, little attention has been paid to fundamental questions on the interoperability and interworking issues that OBS will have to face in a heterogeneous network scenario such as the future Internet. This article introduces a generalized multi-protocol label switching (GMPLS)-based control plane architecture for future OBS networks. This GMPLS/OBS control plane solution leverages on the GMPLS interoperability to enable seamless vertical and horizontal OBS integration with different switching layers under a common control plane. The burst label switched path (b-LSP) entity has been introduced to accomplish this purpose, as well as to guarantee end-users quality of service (QoS) requirements to effectively support emerging data applications. The establishment of a b-LSP does not entail explicit resource reservation, but the addition of new entries in the OBS node forwarding tables with the resources available for that b-LSP. Hence, by making a resource available to multiple b-LSPs, the statistical multiplexing nature of OBS is preserved. A mixed integer linear programing formulation has been presented to get the most out of the available resources given the expected traffic demands and their QoS requirements. Moreover, in the network operation phase, GMPLS-driven b-LSP capacity reconfigurations are dynamically triggered whenever unfavorable network conditions are detected. An exhaustive simulation campaign assesses the performance of the proposed GMPLS/OBS network architecture on different network scenarios. Finally, future research lines on the topic are outlined. © 2012 Optical Society of America.


Borzycki K.,National Institute of Telecommunications NIT | Kobelke J.,Institute fur Photonische Technologien E.V. IPHT | Mergo P.,Maria Curie Sklodowska University | Schuster K.,Institute fur Photonische Technologien E.V. IPHT
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

We present experience with photonic crystal fiber (PCF) characterization during COST Action 299, focusing on phenomena causing errors and ways to mitigate them. PCFs developed at IPHT Jena (Germany) and UMCS Lublin (Poland), designed for single mode operation were coupled to test instruments by fusion splicing to intermediate lengths of telecom single mode fibers (SMF). PCF samples were short (0.5-100 m), with 20-70 dB/km attenuation at 1310 nm and 1550 nm. Optical Time Domain Reflectometer (OTDR) was best for measuring loss as most PCFs produced strong backscattering, while variable splice losses and difficulties with PCF cleaving for optical power measurements made cutback and insertion loss measurements inaccurate. Experience with PCF handling and cleaving is also reviewed. Quality of splices to fiber under test was critical. Excitation of higher order modes produced strong "noise" during measurements of polarization parameters like PMD or PDL. Multimode propagation and vibration-induced interference precluded testing of fine dependence of PMD on temperature or strain, causing random variations comparable to true changes of PMD. OTDR measurements were not affected, but testing of short fiber sections with very different backscattering intensities puts special demands on instrument performance. Temperature testing of liquid-infiltrated PCF was time-consuming, as settling of parameters after temperature change took up to 40 minutes. PCFs were fragile, breaking below 2% linear expansion, sometimes in unusual way when twisted. © 2011 SPIE.


Borzycki K.,National Institute of Telecommunications NIT | Kobelke J.,Institute of Photonic Technology | Schuster K.,Institute of Photonic Technology | Wojcik J.,Maria Curie Sklodowska University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Coupling a photonic crystal fiber (PCF) to measuring instruments or optical subsystems is often done by splicing it to short lengths of single mode fiber (SMF) used for interconnections, as SMF is standardized, widely available and compatible with most fiber optic components and measuring instruments. This paper presents procedures and results of loss measurements during fusion splicing of five PCFs tested at NIT laboratory within activities of COST Action 299 "FIDES". Investigated silica-based fibers had 80-200 μm cladding diameter and were designed as single mode. A standard splicing machine designed for telecom fibers was used, but splicing procedure and arc power were tailored to each PCF. Splice loss varied between 0.7 and 2.8 dB at 1550 nm. Splices protected with heat-shrinkable sleeves served well for gripping fibers during mechanical tests and survived temperature cycling from -30°C to +70°C with stable loss. Collapse of holes in the PCF was limited by reducing fusion time to 0.2-0.5 s; additional measures included reduction of discharge power and shifting SMF-PCF contact point away from the axis of electrodes. Unfortunately, short fusion time sometimes precluded proper smoothing of glass surface, leading to a trade-off between splice loss and strength. © 2010 SPIE.


Borzycki K.,National Institute of Telecommunications NIT | Kobelke J.,Institute of Photonic Technology | Schuster K.,Institute of Photonic Technology | Wojcik J.,Maria Curie Sklodowska University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Six photonic crystal fibers (PCFs) were characterized at NIT laboratory participating in COST Action 299 "FIDES", allowing for comparisons of properties and their dependence on fiber design. Samples tested included three nonlinear fibers with germanium doped core, two fibers with un-doped core and honeycomb photonic structure, and a "PANDAlike" PCF with a pair of large holes along an un-doped core. Tests included optical time domain reflectometer (OTDR) measurements, spectral loss, polarization mode dispersion (PMD) and its variations with temperature, fiber twist and axial strain. Elastooptic coefficient was measured for 2 fibers. Most samples exhibited high PMD, up to 3 ps/m. PMD was usually reduced by twisting the fiber, but twist sensitivity varied widely. The "PANDA-like" PCF, however, had PMD virtually unaffected by both twist and tensile strain; the latter property made it different from true PANDA fiber tested for comparison. Intensity of backscattering in each PCF was stronger compared to a standard telecom single mode fiber (SMF), by a factor up to 110x. © 2010 SPIE.


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.


Borzycki K.,National Institute of Telecommunications NIT | Schuster K.,Institute of Photonic Technology
Springer Series in Optical Sciences | Year: 2016

Several techniques for characterization of photonic crystal fibers (PCFs) are reviewed, focusing on measurements of attenuation, optical uniformity, selected polarization parameters, and effects of temperature and mechanical strain applied to the fiber. PCF properties often radically differ from those of conventional fibers used in communications networks, and available lengths are generally short, therefore different approach to characterization is required. Comparisons of alternative methods for selected tests are made, and examples of errors in PCF handling and testing are discussed. Examples of results obtained for silica single-mode PCFs with GeO2-doped core are also presented, accompanied by geometrical and compositional fiber data. © Springer Science+Business Media Dordrecht 2016.

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