[Laser] 144km 10 Mbit/sec laser link acheived

[Ed]

is this a new terrestrial record?

-ed


http://www.oerlikon.com/ecomaXL/index.php?site=SPACE_EN_press_releases_detail&udtx_id=5060

Oerlikon Space demonstrates laser data link across a distance of 1.5 
million kilometres

07 Nov 2007

November 2007 - On the Canary Islands last week, a team from Oerlikon Space
demonstrated the feasibility of a laser link across a distance of 1.5
million kilometres for the first time ever. In the future, laser links like
this one will be able to transmit data across huge distances through the
universe far more rapidly and efficiently than is possible using
conventional radio links today.

To prove that data transmission across the vast distance of 1.5 million
kilometres is really feasible, the Oerlikon engineers had devised a special
experiment in which they set up a laser link between the islands of La Palma
and Tenerife. The transmission unit was modified in such a way that the
conditions on the 144-kilometre stretch between the islands exactly
reflected those that would prevail on a 1.5 million kilometre link through
space. This was achieved primarily by reducing the emission aperture of the
laser to a diameter of less than half a millimetre in order to weaken the
light signal.

The Oerlikon team installed the transmission unit in a container beside the
Nordic Optical Telescope at an altitude of 2400 metres on Roque de los
Muchachos, the highest mountain on La Palma in the Canary Islands. Because
of the unusually clear air, this is an ideal location for optical
experiments. The receiver terminal was situated in the Optical Ground
Station (OGS) of the European Space Agency ESA on Tenerife.

Although the optical experiment was hampered by unfavourable weather
conditions with unusually high cloud and strong winds during the first few
days, a breakthrough was achieved at noon on Wednesday. The experts from
Oerlikon Space succeeded in establishing a laser link between La Palma and
Tenerife. In the course of the experiment, they achieved transmission rates
of over 10 Mbit/sec. At this speed, it would take a mere two seconds to
transmit the entire text of the Bible. The data rate would also be
sufficient to transmit three digital television programmes simultaneously.

Laser-based data transmission has several advantages over conventional radio
links. Because of the shorter wavelength, lasers can transmit more data than
radio signals in the same period of time. Lasers can also be far more
accurately aligned with the receiver than radio waves, and therefore require
less power for data transmission.

These advantages are particularly useful in space applications, for instance
when large quantities of data need to be transmitted rapidly back and forth
between satellites. When data have to be transmitted across vast distances,
too, laser communication will be the medium of choice in future. The
distance of 1.5 million kilometres that was simulated on the Canary Islands
is equivalent to the distance between the Earth and Lagrange points L1 and
L2. These mark specific positions in space at which it is particularly
advantageous to place space telescopes. Equipped with laser terminals,
telescopes such as these will in future be able to transmit far greater
quantities of observation data to Earth than is possible by radio today.
Laser communication could also be used for transmitting data to Earth during
future missions to the moon.