Abstract
M.Ing.
Fibre Bragg gratings (FBGs) have been manufactured for the first time in South Africa by
means of the phase mask method. It is possible to manufacture not only uniform FBGs,
but also chirped FBGs. The optical fibre that is used for imprinting the FBGs can also be
hydrogen loaded locally. FBGs with a reflectivity of 99.7% and higher can be written by
making use of the experimental setup presented in this thesis. It is possible to
manufacture a FBG with a centre wavelength that has any value between the Bragg
wavelength and approximately 6 nm lower than the Bragg wavelength. This is done by
stretching the optical fibre prior to the writing process.
FBGs have been simulated in MATLAB to get an idea of what one may expect during the
manufacturing process. The program makes it possible to simulate the effects of changes
in grating length, index modulation, pressure, temperature and strain on the centre
wavelength of an FBG.
Dispersion is explained in detail. Chromatic dispersion, which is part of dispersion as a
whole, can be cancelled by making use of an FBG. The different techniques for the
measurement of chromatic dispersion is explained. Some insight is given on dispersion
(the pulse broadening in the time domain due to the different velocities of different
wavelengths from the source's finite optical bandwidth) compensation. An FBG that was
manufactured locally has been tested as a dispersion compensator. It was found that an
FBG is effective in performing this function.