Free-Space Optical Communications

Free-Space Optical Communications

Space and atmospheric optical links

Free-space optical (FSO) links over long distances have been made possible by the development of different key technologies in the near-infrared: high-power lasers, high-speed components, high-sensitivity detectors, cost-efficient optics. In space or through the atmosphere, FSO links increase the capacity (> 1 Gbit/s) and the accessibility (no required license for spectrum usage) of data transmissions. Design issues include atmospheric perturbations, beam tracking and high geometric losses. To face the current FSO challenges, the Fraunhofer Heinrich Hertz Institute (HHI) develops techniques to increase the link reliability and exploits its know-how on fiber-based terrestrial networks.

Advantages compared to radio links

  • Larger bandwidth available
  • Smaller terminals and lower power consumption
  • No spectrum regulation

Application examples

  • Downlinks from Earth-observation satellite
  • Feeder link to telecommunication satellite in GEO orbit
  • Satellite and aircraft communications
  • Quantum key distribution from space

Challenges

  • Mitigation of atmospheric impairments (cloud, turbulence)
  • Supply of the very high data rates of fiber communications

Expertise of Fraunhofer HHI

  • Design and fabrication of 1550-nm components
  • Numerical optimization of transmitters and receivers (including optical amplifiers)
  • Design of WDM (wavelength multiplexing) transmissions
  • Design of atmospheric mitigation techniques (spatial diversity, adaptive systems)
  • Experimental validation of the whole design
  • Atmospheric transmission window around 1064 nm

  • Atmospheric transmission window around 1550 nm. The wavelength range of high power EDFAs is shown by the black filling of the horizontal bars

Partners:

  • DLR (Oberpfaffenhofen)
  • RUAG Space AG (Zürich)

Related Projects

Contact

Dr.-Ing. Nicolas Perlot

Dr.-Ing. Nicolas Perlot

Tel.
+49 30 31002-782
Fax
+49 30 31002-250