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Klinkowski M.,National Institute of Telecommunications | Walkowiak K.,Wroclaw University of Technology
IEEE Communications Letters | Year: 2011

A spectrum-sliced elastic optical path network (SLICE) architecture has been recently proposed as an efficient solution for a flexible bandwidth allocation in optical networks. In SLICE, the problem of Routing and Spectrum Assignment (RSA) emerges. In this letter, we both formulate RSA as an Integer Linear Programming (ILP) problem and propose an effective heuristic to be used if the solution of ILP is not attainable. © 2011 IEEE. Source

Klinkowski M.,National Institute of Telecommunications | Walkowiak K.,Wroclaw University of Technology
IEEE Network | Year: 2013

This article provides motivation for the elastic optical network (EON) approach, an efficient and cost-effective solution for provisioning of cloud computing traffic. As opposed to wavelength switched optical networks (WSONs), the capabilities of which are limited by the use of rigid frequency grids, EON architectures allow for both scalable bandwidth provisioning and flexible resource allocation. The deployment cost, energy consumption, and bandwidth usage for both EON and classical WSON transport networks are compared in pan-European and U.S. backbone networks for 2012¿2020 using Cisco traffic predictions. Results show that the EON concept significantly outperforms WSON in all examined criteria, and the gap between the two architectures increases in subsequent years. Moreover, potential advantages of anycast routing in transport networks with data center traffic are demonstrated. © 1986-2012 IEEE. Source

Jaroszewicz S.,National Institute of Telecommunications
Data Mining and Knowledge Discovery | Year: 2010

The paper presents a method of interactive construction of global Hidden Markov Models (HMMs) based on local sequence patterns discovered in data. The method is based on finding interesting sequences whose frequency in the database differs from that predicted by the model. The patterns are then presented to the user who updates the model using their intelligence and their understanding of the modelled domain. It is demonstrated that such an approach leads to more understandable models than automated approaches. Two variants of the problem are considered: mining patterns occurring only at the beginning of sequences and mining patterns occurring at any position; both practically meaningful. For each variant, algorithms have been developed allowing for efficient discovery of all sequences with given minimum interestingness. Applications to modelling webpage visitors behavior and to modelling protein secondary structure are presented, validating the proposed approach. © 2010 The Author(s). Source

Klinkowski M.,National Institute of Telecommunications
Advances in Intelligent Systems and Computing | Year: 2013

In this work we address the problem of static Routing and Spectrum Assignment (RSA) in a flexible grid optical network with dedicated path protection consideration. Since RSA is a difficult problem, we make use of the Genetic Algorithm (GA) metaheuristic to provide near-optimal solutions to the problem. We investigate the effectiveness of GA for a set of network scenarios. Evaluation results show that the proposed algorithm outperforms reference algorithms from the literature. © 2013 Springer-Verlag Berlin Heidelberg. Source

Osuch T.,National Institute of Telecommunications
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2016

The influence of the complex interference patterns created by a phase mask with variable diffraction efficiency in apodized fiber Bragg grating (FBGs) formation on their reflectance spectra is studied. The effect of the significant contributions of the zeroth and higher (m > ±1) diffraction orders on the Bragg wavelength peak and its harmonic components is analyzed numerically. The results obtained for Gaussian and tanh apodization profiles are compared with similar data calculated for a uniform grating. It is demonstrated that when an apodized FBG is written using a phase mask with variable diffraction efficiency, significant enhancement of the harmonic components and a reduction of the Bragg wavelength peak in the grating spectral response are observed. This is particularly noticeable for the Gaussian apodization profile due to the substantial contributions of phase mask sections with relatively small phase steps in the FBG formation. © 2016 Optical Society of America. Source

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