Future telecom satellite based on geo-stationary Earth orbit (GEO) will require advanced payloads in Kaband so as to receive, route and re-transmit hundreds of microwave channels over multiple antenna beams.
We report on the proof-of-concept demonstration of a analogue repeater making use of microwave photonic technologies for supporting broadband, transparent, and flexible cross-connectivity. It has microwave input and output sections, and features a photonic core for LO distribution, frequency down-conversion, and cross-connection of RF channels.
With benefits such as transparency to RF frequency, infinite RF isolation, mass and volume savings, such a microwave photonic cross-connect would compare favourably with microwave implementations, and based on optical MEMS switches could grow up to large port counts.
This paper describes the activities and results of an ESA-funded project concerned with the assessment of optical amplifier technologies and products for applications in fiber optic subsystems of future satellite payloads.
On-board applications are briefly introduced, together with associated system-level requirements. Optical amplifier technologies, research achievements and products are reviewed. They are compared in terms of current performance, perspectives and suitability for the target space applications. Optical fibre amplifiers, not limited to Erbium-doped amplifiers, Erbium-doped waveguide amplifiers and Semiconductor Optical Amplifiers are covered. The review includes analysis and trade-off of all performance parameters including saturation output power, noise figure, polarisation maintaining capability, wall-plug efficiency, and mass and size.
A selection of optical amplifier products for further evaluation and testing is presented. Results of extensive testing covering both functional performance and environmental behaviour (mechanical, thermal vacuum, radiations) aspects are reported. Most of the work has been completed, but an extension has been proposed for checking and comparing the behaviour of doped fibers under gamma radiation.
The distribution of high spectral purity reference signals over optical fibre in future telecommunication satellite payloads is presented. Several types of applications are considered, including the distribution of a reference frequency at 10 MHz (Ultra-Stable Reference Oscillator) as well as the distribution of a radiofrequency oscillator around 800 MHz (Master Local Oscillator). The results of both experimental and theoretical studies are reported. In order to meet phase noise requirements for the USRO distribution, the use of an optimised receiver circuit based on an optically synchronised oscillator is investigated. Finally, the optical distribution of microwave local oscillators at frequencies exceeding 20 GHz is described. Such a scheme paves the way to more advanced sub-systems involving optical frequency-mixing and optical transmission of microwave signals, with applications to multiple-beam active antennas.
Since several years, perspectives and assets offered by photonic technologies compared with their traditional RF counterparts (mass and volume reduction, transparency to RF frequency, RF isolation), make them particularly attractive for space applications  and, in particular, telecommunication satellites . However, the development of photonic payload concepts have concurrently risen and made the problem of the ability of optoelectronic components to withstand space environment more and more pressing. Indeed, photonic components used in such photonic payloads architectures come from terrestrial networks applications in order to benefit from research and development in this field.
This paper presents some results obtained in the frame of an ESA-funded project, carried out by Thales Alenia Space France, as prime contractor, and Alter Technology Group Spain (ATG) and Universidad Politecnica de Madrid (UPM), as subcontractors, one objective of which was to assess commercial high frequency optical intensity modulators for space use through a functional and environmental test campaign. Their potential applications in microwave photonic sub-systems of telecom satellite payloads are identified and related requirements are presented. Optical modulator technologies are reviewed and compared through, but not limited to, a specific figure of merit, taking into account two key features of these components : optical insertion loss and RF half-wave voltage. Some conclusions on these different technologies are given, on the basis of the test results, and their suitability for the targeted applications and environment is highlighted.
Thales Alenia Space has elaborated innovative telecom payload concepts taking benefit from the capabilities of photonics and so-called microwave photonics. The latter consists in transferring RF/microwave signals on optical carriers and performing processing in the optical domain so as to benefit from specific attributes such as wavelength-division multiplexing or switching capabilities.
In the last decade, Thales Alenia Space has put significant research effort in photonic technologies for satellite applications, with the objective to provide telecom payload systems with enhanced functionality, higher performance and lower costs.
The proof-of-concept demonstration of an microwave photonics cross-connect for telecom satellite repeaters is reported. The system includes optical distribution of a high-purity local oscillator at 26 GHz, frequency down-conversion from 30 to 4 GHz, and optical cross-connection of microwave signals.
Various circuits dedicated to high spectral purity signal transmission using fiber optics are presented. Three application types are investigated: signal transmission of ultra stable oscillators at 10 MHz, IF distribution at 874 MHz and microwave synthesized signals at 3.5 GHz. The receiver circuit is an optically synchronized oscillator, which provides a good signal conditioning far from the carrier while maintaining the high input signal quality close to the carrier