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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