Coupling effects from source to optical fibre or from fibre to fibre
are very important in the design of communication systems using such
fibres, since both the amount of guided power and the output pulse
shape depend on them.
This work is an investigation into such effects.
Various fibre imhomogeneities have been studied analytically. Internally,
these are the refractive index difference A, the core ellipticity and the
difference in numerical apertures; externally, the factors considered
are fibre separation, offset and tilt. The problem is treated using geometrical optics and is applied to
various profiles of different refractive index exponent (a). Fibres
produced currently by the (MCVD) technique normally have a dip in the
refractive index profile at the centre of the core. This dip in the
refractive profile affects the launching efficiency and causes pulse
broadening in multimode graded index fibres and birefringence in single
mode graded index elliptical fibres.
parameters has been investigated.
The effect of the dip on these
Finally experiments have been carried out to test the validity of some
of the theoretical derivations.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.