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Basic Concept
The basic idea to use guided light
for data communication was first published in 1939 by H.
Buchholz in his paper „Die Quasioptik der Ultrakurzwellenleiter“
(translated “quasi optical behaviour of ultra short wave
guides”). However, it took more than 20 years to develop the
first realistic technical solutions; mainly encouraged by the
first available diode lasers in 1962. These new light sources
are ideally suited as transmitters because of their ability to
be modulated and in addition, as we know today, they can be
produced in large numbers at low prices.
Nowadays, world-wide communication is based on fibre optics
combined with laser diodes and the development in this area
belongs to the most exciting ones in this century. However, for
realisation a lot of technical problems had to be solved. In the
fibres mainly used in communication, the light is guided within
a „glass tunnel“ with a diameter of only 9 µm. The necessary
mechanical components as well as the production process of the
fibres themselves were the subject of comprehensive
developments.
The field of fibre optics is still expanding and is of high
common interest. Therefore, this experiment is a valuable
contribution for students entering this exciting technology.
The tremendous success of optical fibre communication, combined
with high mass production, makes it possible to make use of
sophisticated components even for single mode devices and fibres.
Consequently, this experiment makes comprehensive use of
commercial parts reducing or even completely removing difficult
alignment tasks. Within this experiment, no alignment is
required; all connections are done with fibre patch cables.
Experimental Set-up
The laser diode slot-in module provides an optical output for
the laser radiation. A variety of measurements concerning the
diode laser itself are performed by connecting the output to the
rotational stage. For experiments with optical fibres, a slot-in
module comprises in total of 5 km of either mono-or single mode
fibre. By modulating the diode laser, time resolved measurements
are carried out allowing to measure e.g. the speed of light
inside the fibre. Due to the arrangement of 5 segments, the
attenuation of the fibre can now be measured without the need to
cut the fibre. A photodetector slot-in module provides accurate
results. Although it is fibre coupled, it can be used for
external measurements using the provided fibre telescope. |
