27 research outputs found
Developing coherent optical wavelength conversion systems for reconfigurable photonic networks
In future optical networks that employ wavelength division multiplexing (WDM), the use of optical switching technologies on a burst or packet level, combined with advanced modulation formats would achieve greater spectral efficiency and utilize the existing bandwidth more efficiently. All-optical wavelength converters are expected to be one of the key components in these broadband networks. They can be used at the network nodes to avoid contention and to dynamically allocate wavelengths to ensure optimum use of fiber bandwidth.
In this work, a reconfigurable wavelength converter comprising of a Semiconductor Optical Amplifier (SOA) as the nonlinear element and a fast-switching sampled grating distributed Bragg reflector (SG-DBR) tunable laser as one of the pumps is developed. The wavelength conversion of 12.5-Gbaud quadrature phase shift keying (QPSK) and Pol-Mul QPSK signals with switching time of tens of nanoseconds is experimentally achieved. Although the tunable DBR lasers can achieve ns tuning time, they present relatively large phase noise. The phase noise transfer from the pump to the converted signal can have a deleterious effect on signal quality and cause a performance penalty with phase modulated signals. To overcome the phase noise transfer issue, a wavelength converter using tunable dual-correlated pumps provided by the combination of a single-section quantum dash passively mode-locked laser (QD-PMLL) and a programmable tunable optical filter is designed and the wavelength conversion of QPSK and 16-quadrature amplitude modulation (16-QAM) signals at 12.5 GBaud is experimentally investigated. Nonlinear distortion of the wavelength converted signal caused by gain saturation effects in the SOA can significantly degrade the signal quality and cause difficulties for the practical wavelength conversion of sig nal data with advanced modulation formats. In this work, the machine learning clustering based nonlinearity compensation method is proposed to improve the tolerance to nonlinear distortion in an
SOA based wavelength conversion system with 16 QAM and 64 QAM signals
Initialization Requirement in Developing of Mobile Learning 'Molearn' for Biology Students Using Inquiry-based learning
Inquiry-based learning is kind of learning activities that
involves studentsâ entire capabilities in exploring and investigating particular objects or phenomenon using critical
thinking skills. Recently, information technology tangibly contributes in any education aspects, including the existence of e-learning, a widely spreading learning model in the 21st
century education. This study aims at initializing needs of
developing mobile learning âMolearnâ based on inquiry-based
method. By cooperating with Biology teacher community in
senior high school, âMolearnâ provides IT-based medium in
Biology learning process
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Application priority framework for fixed mobile converged communication networks
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The current prospects in wired and wireless access networks, it is becoming increasingly important to address potential convergence in order to offer integrated broadband services. These systems will need to offer higher data transmission capacities and long battery life, which is the catalyst for an everincreasing variety of air interface technologies targeting local area to wide area connectivity. Current integrated industrial networks do not offer application aware context delivery and enhanced services for optimised networks. Application aware services provide value-added functionality to business applications by capturing, integrating, and consolidating intelligence about users and their endpoint devices from various points in the network. This thesis mainly intends to resolve the issues related to ubiquitous application aware service, fair allocation of radio access, reduced energy consumption and improved capacity. A technique that measures and evaluates the data rate demand to reduce application response time and queuing delay for multi radio interfaces is proposed. The technique overcomes the challenges of network integration, requiring no user intervention, saving battery life and selecting the radio access connection for the application requested by the end user. This study is split in two parts. The first contribution identifies some constraints of the services towards the application layer in terms of e.g. data rate and signal strength. The objectives are achieved by application controlled handover (ACH) mechanism in order to maintain acceptable data rate for real-time application services. It also looks into the impact of the radio link on the application and identifies elements and parameters like wireless link quality and handover that will influence the application type. It also identifies some enhanced traditional mechanisms such as distance controlled multihop and mesh topology required in order to support energy efficient multimedia applications. The second contribution unfolds an intelligent application priority assignment mechanism (IAPAM) for medical applications using wireless sensor networks. IAPAM proposes and evaluates a technique based on prioritising multiple virtual queues for the critical nature of medical data to improve instant transmission. Various mobility patterns (directed, controlled and random waypoint) has been investigated and compared by simulating IAPAM enabled mobile BWSN. The following topics have been studied, modelled, simulated and discussed in this thesis: 1. Application Controlled Handover (ACH) for multi radios over fibre 2. Power Controlled Scheme for mesh multi radios over fibre using ACH 3. IAPAM for Biomedical Wireless Sensor Networks (BWSN) and impact of mobility over IAPAM enabled BWSN. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in multi radios over fibre performance in terms of application response delay and power consumption by upto 75% and 15 % respectively, reduction in traffic loss by upto 53% and reduction in delay for real time application by more than 25% in some cases
1997 Research Reports: NASA/ASEE Summer Faculty Fellowship Program
This document is a collection of technical reports on research conducted by the participants in the 1997 NASA/ASEE Summer Faculty Fellowship Program at the Kennedy Space Center (KSC). This was the 13th year that a NASA/ASEE program has been conducted at KSC. The 1997 program was administered by the University of Central Florida in cooperation with KSC. The program was operated under the auspices of the American Society for Engineering Education (ASEE) with sponsorship and funding from the Education Division, NASA Headquarters, Washington, D.C., and KSC. The KSC Program was one of nine such Aeronautics and Space Research Programs funded by NASA in 1997. The NASA/ASEE Program is intended to be a two-year program to allow in-depth research by the university faculty member. The editors of this document were responsible for selecting appropriately qualified faculty to address some of the many problems of current interest to NASA/KSC
Aplicação de Sistemas Baseados em Regras Fuzzy para o Roteamento em Redes Ăpticas
Em uma rede Ăłptica transparente sem equipamentos para conversĂŁo de comprimentos de onda, o atendimento de uma requisição de conexĂŁo entre dois nĂłs exige a determinação de uma entre as possĂveis rotas que os interligam e a atribuição de um comprimento de onda especĂfico, em que a informação serĂĄ transmitida do nĂł origem ao nĂł destino. O processo de determinação de uma rota Ă© importante, pois a escolha da rota influencia a eficiĂȘncia na utilização de recursos e, consequentemente, o desempenho da rede. Nesse processo, geralmente Ă© levado em consideração apenas um critĂ©rio, quase sempre o nĂșmero de enlaces das rotas. O uso de critĂ©rios adicionais, desde que adequadamente combinados, pode levar a uma melhoria no desempenho da rede. Para combinar critĂ©rios no processo de decisĂŁo de uma rota, Ă© implementado neste trabalho um sistema baseado em regras fuzzy. Os resultados apresentados foram obtidos com um sistema fuzzy, que leva em consideração, alĂ©m do nĂșmero de enlaces das rotas, a quantidade de comprimentos de onda contĂnuos disponĂveis em cada rota no momento em que ocorre uma requisição de conexĂŁo. Ă feita uma anĂĄlise de desempenho de duas redes com topologias distintas: uma rede em malha regular com 16 nĂłs e 32 enlaces e uma rede em malha irregular com 14 nĂłs e 20 enlaces. Os parĂąmetros adotados nesta anĂĄlise sĂŁo a probabilidade de bloqueio de requisiçÔes de conexĂŁo e a utilização de recursos da rede
Architecture and algorithm for reliable 5G network design
This Ph.D. thesis investigates the resilient and cost-efficient design of both C-RAN and Xhaul architectures. Minimization of network resources as well as reuse of already deployed infrastructure, either based on fiber, wavelength, bandwidth or Processing Units (PU), is investigated and shown to be effective to reduce the overall cost. Moreover, the design of a survivable network against a single node (Baseband Unit hotel (BBU), Centralized/Distributed Unit (CU/DU) or link failure proposed. The novel function location algorithm, which adopts dynamic function chaining in relation to the evolution of the traffic estimation also proposed and showed remarkable improvement in terms of bandwidth saving and multiplexing gain with respect to conventional C-RAN. Finally, the adoption of Ethernet-based fronthaul and the introduction of hybrid switches is pursued to further decrease network cost by increasing optical resource usage
Optics for AI and AI for Optics
Artificial intelligence is deeply involved in our daily lives via reinforcing the digital transformation of modern economies and infrastructure. It relies on powerful computing clusters, which face bottlenecks of power consumption for both data transmission and intensive computing. Meanwhile, optics (especially optical communications, which underpin todayâs telecommunications) is penetrating short-reach connections down to the chip level, thus meeting with AI technology and creating numerous opportunities. This book is about the marriage of optics and AI and how each part can benefit from the other. Optics facilitates on-chip neural networks based on fast optical computing and energy-efficient interconnects and communications. On the other hand, AI enables efficient tools to address the challenges of todayâs optical communication networks, which behave in an increasingly complex manner. The book collects contributions from pioneering researchers from both academy and industry to discuss the challenges and solutions in each of the respective fields