Soliton propagation in optical fibers 

     Thomas Binhammer

Abstract: 

Motivation:
Optical fibers play an important role in modern communication systems
They provide the advantage of high bandwidth and low losses. The development of
cheap semiconductor lasers and the enormous improvements of optical
properties of the fibers opened the door for a widespread use for information
transmission.  Nonlinearity in the system normally produces undesired effects
like crosstalk, i.e. the interaction of waves of different frequencies. But
there are also very interesting phenomena developping out of nonlinear effects
One of them is the possible propagation of solitons in optical fibers
These special pulse-like waveforms have unusual physical properties like
enormous stability. Its shape is kept over long distances without broadening, even
after interaction with other solitons.  Objects like this would be suitable
to provide the basic unit of information, an optical bit. 

Basic topics:
The first part of my talk is focussed on the fiber itself. Different types
of fibers and their physical properties are shortly presented. Then I will
sum up the main features of wave propagation in these media, among them
issues like possible modes or  absorption properties. An important topic is the
dispersion during the propagation because it is of major impact for any
application in information technology and moreover for the forming of solitons.
Another essential notion is concerned with the nonlinear effects that can
occur in the media. I will give some ideas on these phenomena, especially on
the Kerr-effect. After this, the interplay of nonlinearity and dispersion
in optical fibers is outlined, leading to the nonlinear Schroedinger
equation. 
As a special solution of this equation the solitons are introduced. I will
try to give a basic idea what this solution looks like and outline some
important properties.  A short overview of solitons in physics and their
applications leads back to solitons in fiber optics communication. The end of my
presentation gives some possible applications of this phenomenon especially
in optical information processing.