The second phase of the TOmCAT (Terabit Optical Communication Adaptive Terminal) project will enable secure high-throughput laser communication between ground stations and satellites in space and is led by TNO Space & Scientific Instrumentation.
This phase of the project brings together Airbus Defence & Space Netherlands, FSO Instruments, Hittech Multin, Celestia-STS, MPB Communications and satellite operators Eutelsat and SES alongside ESA and the Canadian Space Agency.
The project has to develop technologies including high-bandwidth adaptive optics, thermally stable opto-mechanics, high-power photonics and high-throughput optical transceivers.
One of the key elements of TOmCAT is its ability to pre-correct the laser light with adaptive optics. When light moves between the surface of the Earth and space, it gets distorted due to the fluctuations in the atmosphere. TOmCAT measures the distortion of the received laser light from the satellite, and by applying the inverse of this distortion to the transmitted light, a robust communication link can be established. This requires high speed adaptive optics.
The system has to generate 650 W of optical power, levels that are high enough to burn any contamination on the mirrors and lenses that track the satellites 36 000 km away in orbit. The accuracy and stability of the moving mirrors satellites needs to be in the order of sub-micro-radian to provide the multiple wavelength multiplexed lasers, each generating 100 Gbit/s of throughput. An opto-mechanical system consisting of a bulk multiplexer, adaptive optics system and a 60 cm telescope are developed, each providing the required stability and accuracy while handling the high optical power levels.
The design, completed in the first phase of the project, uses a ‘digitally transparent’ architecture where RF signals will be sampled and modulated onto the optical domain by a digital signal processor. High power optical Amplifiers (EDFAs) boost the optical signals to high power levels in the order of 50 Watts per channel.