Abstract
M.Ing.
Long distance optical communication systems experience a large degree
of attenuation due to fibre losses, necessitating signal amplification.
Erbium Doped Fibre Amplifiers (EDFAs) have found widespread
use as all-fibre optical amplifiers, but exhibit unequal amplification of
different wavelengths. Since the gain spectrum is signal-power and
pump-power dependent, each EDFA spectrum may differ considerably,
and a tuneable gain equalizer is required. A tuneable long-period grating
(LPG) can be implemented as a gain equalizer for EDFAs.
This dissertation deals with the design of an integrated optic version
of the tuneable equalizing filter. The various components of which
the device comprises, including optical couplers, Mach-Zehnder interferometers
and an LPG, are investigated. The integrated optics designs
of these components are then done using the BeamPROP software
package. The use and optical properties of germania-doped silica
as photosensitive waveguide material is studied. The production
of the films for the gain equalizer, using electron-cyclotron resonance
plasma-enhanced chemical vapour deposition, is discussed. Characterization
of these films was carried out using spectroscopic ellipsometry
and infrared spectroscopy. The optical constants, thickness, germania
content and hydroxyl absorption was calculated using these measurements.