Pulse propagation in optical fibres

This note describes the simulation exercise of the course 34130 Introduction to Optical Communication on group velocity dispersion and self-phase modulation in optical fibres. After introducing a general optical communication system, the propagation of optical pulses in a dispersive fibre will be described with special emphasis on the simple case of a Gaussian pulse, followed by a brief introduction to optical fibre nonlinearities, in particular self-phase modulation. The three exercises, making use of the VPIplayer environment, will then be introduced. The main goals of the exercises are: 1) to introduce the relation between the time and frequency domain descriptions of a signal, 2) to observe and calculate the time domain pulse broadening due to dispersion, and 3) to address the power dependence of the fibre behaviour due to the power dependent refractive index

SLA-based management of software licenses as web service resources in distributed computing infrastructures

Until recently the use of applications requiring a software license for execution was quite limited in distributed environments. Due to the mandatory centralised control of license usage at application runtime, e.g. heartbeat control by the license server running at the home site of a user, traditional software licensing practices are not suitable especially when the distributed computing infrastructure stretches across administrative domains. In this paper we present a novel approach for managing software licenses as web service resources in distributed service oriented environments. Licenses become mobile objects, which may travel to the environment where required to authorise the execution of a license protected application. A first implementation has been realised for dynamic Grid environments in the European SmartLM project co-funded by the European Commission. The SmartLM solution decouples authorisation for license usage from authorisation for application execution. All authorisations are expressed as and guaranteed by Service Level Agreements. We will present the core technology, discuss various security aspects and how they are addressed in the SmartLM prototype, and present the evaluation of the prototype through a number of usage scenarios. Finally, we will give an outlook on specific issues and current work extending the solution to Clouds and service based systems in general. (C) 2011 Elsevier B.V. All rights reserved

elasticLM: A novel approach for software licensing in distributed computing infrastructures

A recent survey of the 451group on Cloud usage highlights software licensing as one of the top five obstacles for Cloud computing, quite similar to what has been observed in the Grid already a couple of years. The reasons are the same: the current praxis of software licensing, both in terms of business models and licensing technology. As a consequence, using commercial applications that require access to a license server for authorisation at run-time has been quite limited until recently in distributed computing environments, especially when the environment stretches across administrative domains like it is the case for public Clouds. In this paper we present a novel approach for managing software licenses as web service resources in distributed service oriented environments. Licenses become mobile objects, which may move to the environment where required to authorise the execution of a license protected application