Professor Jürg Leuthold of the Helmholtz Association of German Research Centres. Credit: Photo: Gabi Zachmann |
Scientists
of Karlsruhe Institute of Technology (KIT) have suc-ceeded in encoding
data at a rate of 26 terabits per second on a single laser beam,
transmitting them over a distance of 50 km, and decoding them
successfully. This is the largest data volume ever transported on a
laser beam. The process developed by KIT allows to transmit the contents
of 700 DVDs in one second only. The journal Nature Photonics reports about this success in its latest issue.
With
this experiment, the KIT scientists in the team of Professor Jürg
Leuthold beat their own record in high-speed data transmission of 2010,
when they exceeded the magic limit of 10 terabits per sec-ond, i.e. a
data rate of 10,000 billion bits per second. This success of the group
is due to a new data decoding process. The opto-electric decoding method
is based on initially purely optical calculation at highest data rates
in order to break down the high data rate to smaller bit rates that can
then be processed electrically. The initially optical reduction of the
bit rates is required, as no electronic processing methods are available
for a data rate of 26 terabits per second.
The
team of Leuthold applies the so-called orthogonal frequency division
multiplexing (OFDM) for record data encoding. For many years, this
process has been used successfully in mobile communi-cations. It is
based on mathematical routines (Fast Fourier Trans-formation).
“The
challenge was to increase the process speed not only by a factor of
1000, but by a factor of nearly a million for data processing at 26
terabits per second,” explains Leuthold who is heading the Institutes of
Photonics and Quantum Electronics and Microstructure Technology at KIT.
“The decisive innovative idea was optical implementation of the
mathematical routine.” Calculation in the optical range turned out to be
not only extremely fast, but also highly energy-efficient, because
energy is required for the laser and a few process steps only.
“Our
result shows that physical limits are not yet exceeded even at
extremely high data rates”, Leuthold says while having in mind the
constantly growing data volume on the internet. In the opinion of
Leuthold, transmission of 26 terabits per second confirms that even high
data rates can be handled today, while energy consumption is minimized.
The so-called orthogonal frequency division multiplexing (OFDM) for record data encoding (right) is compared to other typical forms of multiplexing. |
“A
few years ago, data rates of 26 terabits per second were deemed utopian
even for systems with many lasers.” Leuthold adds, “and there would not
have been any applications. With 26 terabits per second, it would have
been possible to transmit up to 400 million telephone calls at the same
time. Nobody needed this at that time. Today, the situation is
different.”
Video
transmissions predominate on the internet and require extremely high
bit rates. The need is growing constantly. In communication networks,
first lines with channel data rates of 100 gigabits per second
(corresponding to 0.1 terabit per second) have already been taken into
operation. Re-search now concentrates on developing systems for
transmission lines in the range of 400 Gigabits/s to 1 Tbit/s. Hence,
the Karlsruhe invention is ahead of the ongoing development. Companies
and scientists from all over Europe were involved in the experimental
implementation of ultra-rapid data transmission at KIT. Among them were
members of the staff of Agilent and Micram Deutschland, Time-Bandwidth
Switzerland, Finisar Israel, and the University of Southampton in Great
Britain.
