| The main task in
my Studienarbeit, was the implementation of a optical fiber modul
for the company PKI, which works under the simulation tool
DICSi (Digital Communication Systems
Simulation).
In the Studienarbeit
the most essential linear characteristics (attenuation and
dispersion) of optical fibres as well as the nonlinear
characteristics (self phase modulation) were
treated.
For the spreading of
optical signals in optical fibers a simplified spreading equation,
together with some analytical and approximative solutions, were
presented. As a simulation method for the spreading of optical
signals in a optical fiber, the Split-Step-Fourier method was
presented.
One of the most
difficult tasks of the fiber modul was the block processing of
signals. For this the "extended Overlap-Add" method was
used.
The simulation results
were checked with analytical and approximation solutions. Finally
two possibilities to improve the simulation times were
introduced:
- examination
of a step control in case of the Split-Step-Fourier method.
- results of a programming in "C"
|
|
|
| DiCSi is a
simulation tool under MATLAB with numerous modules, and is suitable
for simulation of digitals communication systems. A simulation
model can be created with several modules. Every simulation model
can be developed in a graphical window by a block diagram. The
needed modules are selected with the help of the keyboard or by
simple mouse click. The modules for DiCSi are usually MATLAB
functions but the user can program his own modules also in C or
FORTRAN. An essential advantage of DiCSi is that all predefined
MATLAB functions and the powerful graphical interface are
available. DiCSi modules can process arbitrary long
signals.
An example of a block
diagram produced with DiCSi:
|
|
|
| Fibre optics is
a branch of the optics, which handles with the transmission of
light by multiple total reflection into optical fibres. The optical
fibre consist of a core with a high refractive index, and a glass
coat with a smaller refractive index. While crossing the core, if
the light spot reach the boundary surface between core and coat,
with an angle of incidence which is greater as the critical corner,
than the light spot is reflected back without losses into the core.
In this way we can transmit the light about long distances, by
tousands reflections inside the fibre.
The simplest
application of glass fibres is the transmission of light to places
which are not easy to reach, how e.g. the drill of one dentist. The
fibers can be used for video transmissions. The video transmission
by optical fibres often becomes an important role at medical
instruments, for examinations inside the human
body.
Glass fibres are also
used in a variety of measurement instruments, in thermometers,
gyroskops. Glass fibres can prove as particularly useful, there
where electrical lines are useless or even dangerous. Glass fibres
are also developed for transmission of high powerful laser
radiations, for blading and drilling.
A growing application
of the glass fibre is the communication. Today many long distance
communication networks for transcontinental connections are already
in use. Also in regional networks the optical fibres are used. An
essential advantage of the glass fibre is, the possibility to
transmit optical signals with relatively low losses. Large
distances can be overbridged with only a few amplifiers. The
amplifiers are situated at the moment by about 100 km, in
comparison with 1,5 km for electrical transmission systems. The
development of electro-optical components and integrated glass
components still will enlarge the potential of the optical fibre
systems.
|
|
|
| Three variants
of the Split-Step-Fourier method were implemented:
1) Simple
Split-Step-Forier method
2) symetrical
Split-Step-Fourier method with midpoint formula
3) symetrical
Split-Step-Fourier method with trapezium
formula.
For the linear case
the simulation results of the impuls reaction of a soliton first
order are compared with the analytical solution. In the
illustration below the analytical impuls reaction of a soliton
first order and the reaction after the simulation are plotted in
same figure.
For the check of the
simulation results in the nonlinear case without attenuation
some analytical solutions for solitons
are used. For the three implemented variants the deviations from
the analytical solution for the soliton first order is presented in
the following figure.
For the check of the
simulation results in the nonlinear case with
attenuationan
approximation for solitons was consulted. In the figure below the
deviations of simulations from the approximative solution for a
soliton first order is represented.
|
|
|
|
|
|
1. Curriculum vitae
