Contraves Space AG is currently developing the OPTEL family of optical terminals for free-space optical communications. The optical terminals within the OPTEL family have been designed so as to be able to position Contraves Space for future opportunities open to this technology. These opportunities range from commercial optical satellite crosslinks between geostationary (GEO) satellites, deep space optical links between planetary probes and the Earth, as well as optical links between airborne platforms (either between the airborne platforms or between a platform and GEO satellite). This paper will present an overview of the space based and airborne system architectures that the Contraves Space family of OPTEL terminals have been designed to support, provide a description and performance summary of each OPTEL terminal and the key technologies that have been developed.
KEYWORDS: Transmitters, Scintillation, Receivers, Refraction, Signal attenuation, Data communications, Optical testing, Free space optics, Data transmission, Visibility
Within the frame of the FASOLT project the German Aerospace Center (DLR) performed channel measurements and optical data transmission tests on a 61 km near ground horizontal path. The transmitter was situated on a mountain top in the German Alps with the receiver placed on top of a building at the DLR site in Oberpfaffenhofen. Partners in the FASOLT project were Contraves Space, Switzerland and EADS Military Aircraft, Germany. During a period of several months various data sets of scintillation data were recorded in one and two laterally separated transmitter configurations and under different environmental conditions. A significant decrease of number and depth of fades was observed for the two transmitter setup. This paper presents an overview on the scintillation statistics of this particular optical channel. Also beam offsets due to refraction have been measured and results are presented here. As well as these measurements, data transmission tests at bit rates of 100 Mbps have been performed. A two transmitter configuration with a transmit power of 1 W per laser and a sensitive APD receiver front-end plugged in to a 75mm Rx telescope have been used. Despite severe scintillations, bit error rates (BER) below 1e-4 could be observed, though synchronization losses of the data and clock recovery affected the results. Tests at 155 Mbps (OC-3) and 270 Mbps (SMPTE 259M) were not successful due to high atmospheric attenuation. This paper gives an overview of the entire experimental setup, sums up the results of this long-haul data transmission experiment, and gives an outlook to further DLR activities in the field of free-space optics.
The presented paper reports on a conceptual design of a High Precision Optical Metrology (HPOM) system for SMART-2 with the emphasis of establishing and controlling the distance between the satellites. SMART-2 serves as a pre-cursor technology mission for DARWIN where critical technologies will be demonstrated. An overview about the DARWIN and SMART-2 mission and requirements is given. The HPOM system must take over from the Radio Frequency (RF) system at an inferometer arm difference of some cm and must establish and control an arm difference of smaller than 5nm at a 3dB bandwidth of 100Hz. A cascaded metrology system has been developed using different optical metrology methods such as time of flight, dual-wavelength and white light interferometry within one system to meet the ambitious requirement.
Conference Committee Involvement (3)
Optical Design and Engineering IV
6 September 2011 | Marseille, France
Optical Design and Engineering
2 September 2008 | Glasgow, Scotland, United Kingdom
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