Optical Freespace Communications


 Transportalbe Optical Ground (TOGS)
zum Bild Transportalbe Optical Ground (TOGS)


For more than 20 years this group has been dealing with high sensitive coherent optical inter-satellite Communications. Since 1998 also atmospheric transmission scenarios are investigated. The advantage of this technology compared with directional RF-links lies mainly in the very narrow divergence of optical beams and according link budget improvements. Furthermore, very high datarates (multi-gigabit per second) only become possible with optical technologies. Further advantages are:

  • very low Tx-power and thus low overall power consumption 
  • small antennas, low terminal weight 
  • tap-proofness   
  • no interference between systems
  • no restrictions by regulation authorities

Challenges are among others the signal disturbances by atmospheric index-of-refraction turbulence, signal attenuation and blocking by clouds and the very precise pointing controle of the mobile terminals.

Application areas for this technology which are investigated by OCG are:

  • Aeronautical links between aircraft, UAV, and satellites; e.g. for disaster relieve, reconnaissance, and end user communications
  • direct links from space probes and satellites to optical ground stations; e.g. for high speed earth observation satellite downlinks
  • Links between future High Altitude Platforms (HAPS)
  • Near-ground links between ground-vehicles, and ships
  • High-precision optical frequency links can allow an increase of up to three orders of magnitude in time and position accuracy
  • The combination of optical free-space data links with quantum key distribution in one system will allow absolute security in future communication systems

Scientific subjects of OCG are among others:

  • Simulation of field propagation through turbulent media
  • Measurement of the atmospheric-optical transmission channel
  • Error protection coding for the atmospheric fading channel
  • Adaptive optics and diversity techniques for coherent receivers
  • Beam acquisition and -tracking under atmospheric conditions

The Group operates the Optical Ground Station Oberpfaffenhofen (OGS-OP) which has been used for successful communication trials with satellites (KIODO, TerraSAR-X-LCT), aircraft (VABENE, ARGOS, MINERVAA, ATENAA), and ground vehicles (project MOND).

From 2011 on a transportable Optical Ground Station (TOGS) will be available for global deployment and use in aeronautical and satellite link campaigns.



In 2009 the company “ViaLight Communications GmbH” was founded by three members of the institute. This spin-off aims at further developing and marketing of the institute’s technology in the optical domain towards commercial products. www.vialight.de

Christian Fuchs
German Aerospace Center

Institute of Communications and Navigation
, Satellite Networks
Tel: +49 8153 28-1547

Fax: +49 8153 28-2844

E-Mail: Christian.Fuchs@dlr.de
Dr. Ramon Mata Calvo
German Aerospace Center

Institute of Communications and Navigation
, Satellite Networks
Tel: +49 8153 28-3448

Fax: +49 8153 28-2844

E-Mail: Ramon.MataCalvo@dlr.de
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