Vol. 62, n° 5-6, May-June 2007
Content available on Springerlink
Jean-Louis de Bougrenet de la Tocnaye, GET/ENST Bretagne, France
Ioannis Tomkos, Athens Information Technology Center, Greece
Michel Joindot, France Télécom R&D, France
Jean-Louis de Bougrenet de la Tocnaye, Ioannis Tomkos, Michel Joindot
WDM transmissions exploiting optical phase conjugation
Xuefeng TANG, Zongyan WU
GET/ENST Bretagne, UMR CNRS6082-Foton, Optics Department, CS 83818, 29238 Brest, France
Abstract Due to the frequency shift occurring in the process of optical phase conjugation (OPC) generation, the application of OPC in multiple-channel transmission is limited severely by the third-order dispersion. In this paper, taking into account the influence of the frequency shift and the compensation of nonlinear effects, we present an effective method to optimize the dispersion map for broad-band transmissions using optical phase conjugation. The numerical simulation results show that high efficiency wavelength-division-multiplexing (WDM) transmissions can be achieved by using the combination of OPC with an optimized dispersion map.
Keywords Optical communication, Wavelength division multiplexing, Light dispersion, Non linear effect, Optical phase conjugaison, Optical fiber transmission, Optimization, Compensation, Simulation.
Impact of chromatic dispersion on DPSK and DQPSK direct-detection optical systems
Pierluigi POGGIOLINI, Gabriella BOSCO
Dipartimento di Elettronica, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129, Torino, Italy
Abstract Chromatic dispersion (CD) limitations for binary and quaternary phase-modulated systems using direct detection receivers are analyzed by numerical simulation, comparing the results with intensity-modulated systems, considering both IMDD (Intensity-Modulation Direct-Detection) and Duobinary formats. Three different receiver structures are assumed and many transmitter and receiver filter bandwidths are spanned, to find out how much CD penalty varies depending on such alternative solutions. Penalty was assessed by means of a very accurate performance estimation semi-analytical technique based on Karhunen-Loève series, which theoretically converges to the exact bit-error rate for direct detection optical systems in the presence of both ASE noise and inter-symbol interference. The results show that DQPSK is the most resilient format to CD, as expected, but it is also the less sensitive format to filter bandwidth variations.
Keywords Optical fiber transmission, Light dispersion, Phase shift keying, Quadrature modulation, Differential modulation, Direct detection, Comparative study, Modulation, Electric filter, Optical filter, Numerical simulation, Karhunen Loeve transformation.
Impact of cascaded filters-based OADMs in an all optical backbone network
Irène JOINDOT, Michel JOINDOT
The authors were with France Télécom, division R&D – Technopole Anticipa, 22307 Lannion, France up to 12/31/2006. The contact address is now michel.joindot at enssat.fr
Abstract In all optical backbone networks, the introduction of Ultra Long Haul (ULH) optical systems associated with Optical Add Drop Multiplexers (OADM) gives rise to new network architectures and also to new engineering constraints, because signals suffer effects which do not exist in networks today. The purpose of this paper is to study, through numerical simulations, the impact on the signal brought by the concatenation of OADMs. It is usually predicted that the transmission quality is severely degraded by filtering effects. However, the simulations show that by introducing for example a small amount of non-linearities, degradations do not obligatorily happen. So as to highlight the effects of some parameters, we have built, in the simulation tool, different components having particular properties to vary amplitude, frequency and phase of filter group delay ripple. We show how in some circumstances, the eye widens due to cross phase modulation reduction or due to the interplay between chromatic dispersion and non-linear effects.
Keywords Optical communication,Wide area network, Optical multiplexer, Cascade arrangement, Numerical simulation, Non linear effect,Wavelength division multiplexing, Binary modulation, Group delay, Optical filter, All optical technology.
Benefits of the use of impairment constraint routing in optical networks
Ioannis TOMKOS, Anna TZANAKAKI, Prasad KULKARNI, George MARKIDIS, Carmen MAS MACHUCA
Athens Information Technology (AIT) – P.O.Box 68, Markopoulo Ave., 19002 Peania/Athens, Greece
Abstract In transparent optical networks, the optical signal accumulates the effects of all physical impairments present along the path it traverses. The conventional selection of signal paths based on e.g. shortest path routing without considering the signal quality and its association with the physical impairments does not always provide the optimum solution in terms of network performance such as blocking and resource utilization. This paper proposes an impairment constraint based routing algorithm to achieve an optimal combination of physical and networking performance taking into account all physical linear impairments including noise, chromatic and polarization mode dispersion, crosstalk and filter concatenation effects in an integrated approach. The performance of a typical metropolitan area network is examined and the improvement achieved when using the proposed approach compared to the conventional shortest path routing is demonstrated.
Key words Optical communication, Network routing, Transmission performance, Background noise, Light dispersion, Crosstalk, Quality factor, All optical technology, Degradation, MAN, Numerical simulation, Optical amplifier.
A simulation study of adaptive burst assembly algorithms in optical burst switched networks with self-similar traffic sources
Siamak AZODOLMOLKY, Anna TZANAKAKI, Ioannis TOMKOS
Athens Information Technology (AIT), P.O.Box 68, Markopoulo Ave., 19002 Peania-Athens, Greece
Abstract It has been extensively demonstrated that the traffic pattern in today’s Internet is Self- Similar. Burst assembly algorithms utilized in optical burst switched (OBS) edge routers can be used to reduce the degree of self-similarity. This work investigates the impact of time and size-based burst assembly algorithms utilized in OBS edge routers, on the self-similarity level of the output traffic. Both static and adaptive algorithms are examined. Our study is based on the OPNET simulation tool focusing on the characteristics of the output traffic in the presence of self-similar input traffic. To estimate the Hurst parameter of the aggregated input and output traffic streams, we have applied various Hurst parameter estimators. The performance impact of the burst assembly algorithms in terms of burst assembly delay and its jitter is also assessed. Our study has shown that the burst assembly mechanism at the OBS edge router reduces the self-similarity level of the output traffic and that this reduction depends on the parameters of the algorithm. Our results reveal that the proposed adaptive burst assembly algorithm performs better comparing to its non-adaptive counterpart.
Keywords Optical telecommunication, Internet, Optical switching, Similitude, Modeling, Numerical simulation, Burst switching, Traffic control, Traffic burstiness.
Performance evaluation of a WDM metropolitan network: A virtual prototyping approach
Jérémie JAUFFRIT*, Bruno FRACASSO*, Michel MORVAN*, Daniel BETOULE**
* GET/ENST Bretagne, UMR CNRS6082-Foton, Optics department – Technopôle de Brest-Iroise, 29285 Brest cedex, France.
** SAGEM S.A. – 5 avenue Pierre Marzin, 22300 Lannion, France.
Abstract We present a generic low-cost and flexible metropolitan area network optical ring architecture and evaluate its performance using optical transmission simulation software. We describe a specific design method that can be used to extract relevant parameters, such as the BER and OSNR for different channels at any ring network node. We show the possibility offered by a personal computer in the physical modeling of a complex system consisting of numerous components with many parameters. The design method that we describe can be considered as an efficient virtual prototyping method, offering cost and timesavings to network planners
Keywords Optical telecommunication, Metropolitan area network, Numerical simulation, Ring network, Network architecture, Performance evaluation, Error rate, Signal to noise ratio.
nOBS: an ns2 based simulation tool for performance evaluation of TCP traffic in OBS networks
Guray GUREL*, Onur ALPARSLAN**, Ezhan KARASAN*
* Department of Electrical and Electronics Engineering, Bilkent University – 06800 Ankara, Turkey
** Graduate School of Information Science and Technology, Osaka University – 1-5 Yamadagaoka, Suita, Osaka
Abstract Performance evaluation of TCP traffic in OBS networks has been under intensive study, since TCP constitutes the majority of Internet traffic. As a reliable and publicly available simulator, ns2 has been widely used for studying TCP/IP networks; however ns2 lacks many of the components for simulating optical burst switching networks. In this paper, an ns2 based OBS simulation tool (nOBS), which is built for studying burst assembly, scheduling and contention resolution algorithms in OBS networks is presented. The node and link objects in OBS are extended in nOBS for developing optical nodes and optical links. The ingress, core and egress node functionalities are combined into a common optical node architecture, which comprises agents responsible for burstification, routing and scheduling. The effects of burstification parameters, e.g., burstification timeout, burst size and number of burstification buffers per egress node, on TCP performance are investigated using nOBS for different TCP versions and different network topologies.
Keywords Optical telecommunication, Optical switching, Burst switching, Simulator program, Numerical simulation, Internet, TCP/IP, Performance evaluation, Wavelength division multiplexing.
A web-based user friendly simulator of optical fiber communication systems
Mustapha RAZZAK, Habib HAMAM
Université de Moncton, Campus de Moncton, Dept of Elect. Eng., Moncton, NB, Canada E1A 3E9
Abstract A simulation tool in optical networks design and evaluation is suggested. This user friendly software, baptized “SystemBuild”, is a powerful tool to simulate optical fiber communication systems and can be easily used for both educational and research purposes. People modeling optical networks can use it to investigate the usefulness and the accuracy of their model as well as the performances of the system they intend to implement. This Webbased software needs neither a license nor an installation. Merely, a conventional Internet browser supporting Java plug-in is necessary. Moreover, the software can run in all platforms that include the Java Virtual Machine (JVM). Signals and values can be directly checked by moving the mouse pointer over the component’s connectors allowing an easy debugging and assistance to the users to build a complex system. The quality of collaboration is offered thanks to the free code access to the platform.
Keywords Optical telecommunication, Metropolitan area network, Numerical simulation, Simulator program, Computer assisting teaching, Optical fiber transmission.
Simulation of integrated optic devices based on BPM
Lara PELLEGRINO1,2, Teresa VIEIRA1, Antonio TEIXEIRA3,4 Paulo ANDRÉ2,3, Paulo MONTEIRO1,3,4
1. Siemens SA, R. Irmãos Siemens – 1, Alfragide, 2720-093 Amadora, Portugal
2. Departamento de Física, Universidade de Aveiro – Campus de Santiago, 3810-193 Aveiro, Portugal
3. Instituto de Telecomunicações – Campus de Santiago, 3810-193 Aveiro, Portugal
4. Departamento de Electrónica, Telecomunicações e Informática, Universidade de Aveiro – Campus de Santiago, 3810-193 Aveiro, Portugal
Abstract The present work shows how to simulate the propagation of optical fields in integrated optics devices, using the Beam Propagation Method, presenting also some results. Finite difference discretization was performed through a Crank-Nicholson algorithm on isotropic media and the software was developed within the Matlab® environment. Structures like ridge waveguide, Y-junctions and parallel waveguides, are simulated and the results are validated through comparison with previously published ones.
Key words: Optical component, Integrated optics, Wave propagation, Numerical simulation, Finite difference method, Optical waveguide, Optical beam, Wave equation, Simulator program.
Dielectric leaky-wave antenna analysis of arbitrary metallic shape
Zahéra MEKKIOUI*, Henri BAUDRAND**
* Department of Physics, Faculty of Sciences, University of Tlemcen – P. Box 119, 13000 Tlemcen, Algeria ;
** Len7, ENSEEIHT – 2 Rue Charles Camichel, P. Box 7122, 31071 Toulouse Cedex 7, France ;
Abstract In this article, the resolution of a dielectric leaky-wave antenna problem of arbitrary metallic strips is presented. This is suggested with an aim of highlighting the influence of the form of the metallic parts, and their transverse surface on the radiating characteristics and to compare the advantages and disadvantages of the non regular forms with those of regular form (rectangular strip). Another challenge which finds its application in several fields, is the possibility of conforming the radiating pattern and performing the characteristics of radiation.
Keywords Dielectric antenna, Leaky wave, Printed antenna, Periodic structure, Metallic part, Geometrical shape, Radiation pattern, Discontinuity, Resonance.
What about the “dissipation of computation” question? A return to Bennett
GET/Télécom Paris, UMR CNRS5141, 46, rue Barrault, 75013 Paris, France.
Abstract In an electronic computing circuit, all the energy delivered by the electric power supply is converted into heat (dissipation). A result from Bennett in 1973 showed that the minimal amount of dissipated energy is not linked with the time-complexity of the computation, but rather with the size of the result, which can be very low. However, real chips are dissipating proportionally to the time-complexity, and this is the major problem challenging the increase of performance and the miniaturization of mobile devices. Why are we confronted to this contradiction ? We return to the reading of Bennett’s paper in order to look for a renewal of fundamental questions it can rise. We suggest a link with the nature of time and with synchronization in distributed systems. This text is a transcript of the talk given at the MIR seminar (Mathématiques pour l’Informatique et les Réseaux) in ENST, the March 9th 2006.
Keywords Computer theory, Thermal dissipation, Computing complexity, Finite automation, Deterministic automation, Reversibility.