No. 1 (2009)
Published:
2009-03-30
ARTICLES FROM THIS ISSUE
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DiffServ Aware MPLS Traffic Engineering for ISP Networks: State of the Art and New Trends
Abstract
In the recent ten years, with the development of new applications through Internet such as multimedia or networked control applications, users need more and more quality of service (QoS). However, the requested QoS is not the same depending on the application. Most of the new models to manage internet traffic are based on specific QoS criteria which should be optimized. This paper presents main multiprotocol label switching (MPLS) approaches such as MPLS adaptive traffic engineering (MATE), load distribution in MPLS (LDM) and load balancing over widest disjoints paths (LBWDP) that are new models for traffic engineering. It also introduces periodic multi-step (PEMS) algorithm that adapts the offered quality depending on the class of the routed traffic.
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100/1000 Gbit/s Ethernet and beyond
Abstract
100 Gbit/s Ethernet is foreseen in metro and access by 2014, while 1 Tbit/s Ethernet is forecasted for trunk links before 1020. This paper reviews the advantages and constraints of the optical networking and discusses how they meet the 100 Gbit/s Ethernet needs.
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All-Optical Techniques Enabling Packet Switching with Label Processing and Label Rewriting
Abstract
Scalability of packet switched cross-connects that utilize all-optical signal processing is a crucial issue that eventually determines the future role of photonic signal processing in optical networks. After reviewing several labeling techniques, we discuss label stacking and label swapping techniques and their benefits for scalable optical packet switched nodes. All-optical devices for implementing the packet switch based on the labeling techniques will be described. Finally, we present a 1×4 all-optical packet switch based on label swapping technique that utilizes a scalable and asynchronous label processor and label rewriter. Error-free operation indicates a potential utilization of the swapping technique in a multihop packet-switched network.
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Features of Formation of Radar-Tracking and Optical Images in a Mobile Test Stand of Radio-Vision Systems of a Car
Abstract
In the report the features of formation of radar images (RI) and optical images (OI) in the mobile test stand of radiovision systems (RVS) of a car are presented. The radiovision system of a car (CRVS) of the millimeter-wavelength with frequency modulation is considered. Features of formation and processing of the radar-tracking image in CRVS are discussed, in particular: the sizes of the image, system of coordinates, primary and secondary processing of RI, requirements for speeds of transfer of figures in real time of processing, for subsystem of display of RI and synchronization. The structure of the mobile test stand of CRVS is described. This stand consists of: CRVS, a video camera, the module of formation, recording and display of RI and of optical images, the module of control of a stand, the power supply unit. Features of formation and display OI are considered, in particular: the coordination of scale and shortening of images, creation of time synchronization at display and records of OI, and questions of synchronous fusion of RI and OI also.
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Setting an Upper-Wavelength Limit to the Supercontinuum Generated in a Photonic Crystal Fibre
Abstract
We report about a novel kind of supercontinuum generation in a photonic crystal fibre in which the spectral broadening occurs only on the blue side of the pump wavelength. As a consequence a limit to the extent of the supercontinuum is set and thus a way for tailoring the broadened spectrum according to a peculiar application is provided. We present a theoretical explanation along with experimental data which are supported by the results of a set of numerical simulations.
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RoFnet – Reconfigurable Radio over Fiber Network Architecture Overview
Abstract
This paper introduces the basic operational concepts of the RoFnet – reconfigurable radio over fiber network, which is a project supported by the Portuguese Foundation forScience and Technology. This project proposes an innovative radio over fiber optical access network architecture, which combines a low cost base station (BS) design, incorporating reflective semiconductor optical amplifiers, with fiber dispersion mitigation provided by optical single sideband modulation techniques. Optical wavelength division multiplexing (WDM) techniques are used to simplify the access network architecture allowing for different BSs to be fed by a common fiber. Different wavelength channels can be allocated to different BSs depending on user requirements. Additionally, in order to improve radio coverage within a cell, it is considered a sectorized antenna interface. The combination of subcarrier multiplexing with WDM, further simplifies the network architecture, by using a specific wavelength channel to feed an individual BS and different subcarriers to drive the individual antenna sectors within the BS.
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Methods of Step-Size Distribution Optimization Used in S-SSFM Simulations of WDM Systems
Abstract
Brief review of methods used for simulation of signal propagation in wavelength division multiplexed (WDM)links is presented. We propose two novel methods of stepsize distribution optimization used to improve symmetrized split step Fourier method (S-SSFM) numerical efficiency: presimulated local error S-SSFM (PsLE S-SSFM) and modified logarithmic (ML S-SSFM). The PsLE S-SSFM contains two stages: in the initial stage step-size distribution optimization is carried out by combining local error method and presimulation with signal spectrum averaging; in the second stage conventional SSFM is used by applying optimal step-size distribution obtained in the initial stage. The ML S-SSFMis generalization of logarithmic method proposed to suppress spurious FWM tones, in which a slope of logarithmic step-size distribution is optimized. Overall time savings exceed 50%, depending of a simulated system scenario.
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Spectroscopic Ellipsometry Analysis of Rapid Thermal Annealing Effect on MBE Grown GaAs1−x−Nx
Abstract
We report on the effect of rapid thermal annealing (RTA) on GaAs1−x−Nx layers, grown by molecular beam epitaxy (MBE), using room temperature spectroscopic ellipsometry (SE). A comparative study was carried out on a set of GaAs1−x−Nx as-grown and the RTA samples with small nitrogen content (x = 0.1%, 0.5% and 1.5%). Thanks to the standard critical point model parameterization of the GaAs1−x−Nx extracted dielectric functions, we have determined the RTA effect, and its nitrogen dependence. We have found that RTA affects more samples with high nitrogen content. In addition, RTA is found to decrease the E1 energy nitrogen blueshift and increase the broadening parameters of E1, E1+Δ1, E′0 and E2 critical points.
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Control Mechanism for All-Optical Components
Abstract
In this article, we give a brief overview of security and management issues that arise in all-optical networks (AONs). Then we present an outline of the multiple attack localization and identification (MALI) algorithm that can participate in some of the tasks for fault management in AONs. Consequently, we discuss a hardware-based control unit that can be embedded in AON nodes to accelerate the performance of the MALI algorithm. We conclude the article with a discussion concerning the applicability and implementation of this device in AON management systems.
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Fault Tolerant Dense Wavelength Division Multiplexing Optical Transport Networks
Abstract
Design of fault tolerant dense wavelength division multiplexing (DWDM) backbones is a major issue for service provision in the presence of failures. The problem is an NP-hard problem. This paper presents a genetic algorithm based approach for designing fault tolerant DWDM optical networks in the presence of a single link failure. The working and spare lightpaths are encoded into variable length chromosomes. Then the best lightpaths are found by use of a fitness function and these are assigned the minimum number of wavelengths according to the problem constraints using first-fit (FF) algorithm. The proposed approach has been evaluated for dedicated path protection architecture. The results, obtained from the ARPA2 test bench network, show that the method is well suited to tackling this complex and multi-constraint problem.
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Network Topology Effect on QoS Delivering in Survivable DWDM Optical Networks
Abstract
The quality of service (QoS) is an important and considerable issue in designing survivable dense wavelength division multiplexing (DWDM) backbones for IP networks. This paper investigates the effect of network topology on QoS delivering in survivable DWDM optical transport networks using bandwidth/load ratio and design flexibility metrics. The dedicated path protection architecture is employed to establish diverse working and spare lightpaths between each node pair in demand matrix for covering a single link failure model. The simulation results, obtained for the Pan-European and ARPA2 test bench networks, demonstrate that the network topology has a great influence on QoS delivering by network at optical layer for different applications. The Pan-European network, a more connected network, displays better performance than ARPA2 network for both bandwidth/load ratio and design flexibility metrics.
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Fusion Splicing and Testing of Photonic Crystal Fibers
Abstract
Properties of two different photonic crystal fibers (PCF) were characterized, enabling comparisons. Properties investigated included spectral attenuation, polarization mode dispersion (PMD), optical time domain reflectometer characteristics, elastooptic factor describing transmission delay induced by axial strain plus effects of temperature cycling and fiber twist on PMD and loss. In particular, temperature and twist dependence of PMD was different for each fiber tested. For optical measurements, fibers were fusion spliced to pigtails with standard telecom single mode fibers. PCF splicing procedures and solutions adopted to minimize collapse of holes during arc fusion and splice loss are presented. It was found that fusion splicing procedure must be individually tailored to each combination of fibers.
