SATNAC 2007 Conference Papers

Outside Plant & Transmission Issues

Title:                   Broad-Pulse Fibre Laser for Incoherent Distance Measurement

Authors:              Jan Du Plessis (University of Johannesburg),
Diethelm Schmieder (University of Johannesburg), Andre Booysen (University of Johannesburg)

Abstract:             We describe a 'Figure-of-Eight' fibre laser in the NALM (Nonlinear Amplifying Loop Mirror) configuration for use in a laser distance measurement device. By varying the length of the NALM loop we produce a variety of long pulses in the nanosecond range. The length of the pulses depend on the length of the NALM loop and the pump power. A low autocorrelated binary sequence is modulated onto one of these long pulses and sent to a target. After reflection, the signal is detected and cross-correlated to obtain the time of flight for the pulse.


Title:                   Simulation of a Proton Exchange Membrane Fuel Cell Stack Using an Electronic Equivalent Circuit Model

Authors:              Johannes Du Toit (Vaal University of Technology),
Hendrik Pienaar (Vaal Unniversity of Technology) 

Abstract:             This paper describes the method used to calculate the parameters of an electronic circuit equivalent model of a PEMFC stack. The model is based on that of Yu and Yuvarajan, but very little detail is given by them on how to calculate the component values of the circuit model based on experimental data of a fuel cell (FC) or FC stack. Here, a method will be established in which the performance data of small FC stacks can be used to simulate the behaviour of much larger stacks under the same operating conditions. It is crucial to be able to simulate a FC stack using an electronic circuit equivalent model when designing power converters for FCs, since the FC stack can then be simulated together with a power converter or any other electronic circuitry. First, a mathematical model of a small, two cell, proton exchange membrane FC (PEMFC) was calculated based on experimental data. This model was then adapted to describe the characteristics of a much larger, 100 W, FC stack. Finally, the mathematical model was used to calculate the needed parameters for an electronic circuit model by establishing a clear relationship between the two models.


Title:                   Optical Add/drop Multiplexing Performed Using Broadband Transmission Filters and a Narrowband Reflection Filter

Authors:              Ronnie Kritzinger (University of Johannesburg),
Pieter Swart (University of Johannesburg), Andre Booysen (University of Johannesburg)

Abstract:             We propose and demonstrate the concept of an optical add/drop multiplexing (OADM) device utilising a pair of broadband transmission filters and a narrowband reflection filter. Numerical simulations are used to illustrate transmission filter performance using the classical grating analysis approach, and a discrete inverse scattering grating synthesis technique. We also investigate the power coupling in a cladding-mode coupler device using different chemical compounds as a coupling medium between optical fibres.


Title:                   Modeling of Rain Attenuation for Terrestrial LOS Radio Link Systems in South Africa

Authors:              Modupe Odedina (University of KwaZulu-Natal),
Thomas Afullo (University of KwaZulu-Natal) 

Abstract:             This paper presents the cumulative distributions of rainfall rate for four different climatic rain zones in South Africa. These climatic rain zones N, M, P and Q has been proposed from a 5-year (2000-2004) locally observed rain rate data in South Africa as against the ITU-R zones of C, D, E, K and N in a previous paper. The cumulative distributions of rain which is specified on a percentage of time basis, that is, the percent of time rain rate exceeds or equals a specific value is used in the rain attenuation prediction. Using the ITU-R rain attenuation prediction model, the cumulative distributions of rain attenuation at different percentages of time for an average of five years at 19.5 GHz for the four different rain zones are determined in South Africa. Using signal level measurements taken in Durban (in the P climatic rain zone in South Africa) over a period of one year (2004) at 19.5 GHz on a 6.73-km link, an empirical model for predicting rain attenuation for terrestrial radio link systems is proposed for each month in the year. This is then compared with other established attenuation models: ITU-R model, Crane Global model and Moupfouma model. These predicted attenuation models for each month are then analysed and tested using different statistical tools.


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