Benoit Benazet

Microwave photonics cross-connect repeater for telecommunication satellites

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.

Optimized Optical Links for High Spectral Purity Ku-band Signal Distribution

Optical fibers constitute an attractive alternative to conventional wiring for the distribution of high spectral purity microwave signals. The main application here investigated is the remote synchronization and control in Ku-band of the elements of an onboard active antenna. The emphasis is put on the receiver which is realized using a synchronized oscillator

Applications of Optical Techniques in Future Communication Payloads

Optics and photonics bring unusual but attractive and performing solutions for implementing functions in communication payload. For the time being, these techniques have been mostly put aside for various reasons, but the technical world changing very fast, it is advisable to check if they could be competitive alternatives. Moreover, new functions will appear in the next generation of broadband satellites in response to the increasing needs for bandwidth, connectivity and flexibility. Optical techniques should be both viable solutions to enhance existing functions and the only solutions to create the new functions of broadband satellites to come. Alcatel Space research department has identified functions and equipment where optical techniques could be either a significant and necessary breakthrough or simply a technical and cost improvement. For mid term, Alcatel Space has selected and studied three functions where optics is particularly attractive for performances, mass saving and cost. First application is backplane interconnections. This technology allows gigabit connections required inside onboard large digital processors. A second application is the transport and distribution of microwaves onto optical fibers. Fibers are an interesting substitution for coaxial harness in payloads. Associated with the emerging Optical Micro-Electro-Mechanical Systems (OMEMS), this technique will extend the routing capability of payloads. A third application is intrasatellite data link. Optic fibers or wireless infrared links are promising choices to build onboard data handling system. In the long term, optical techniques could change the very aspect of repeaters and antennas of communication payloads. However, the introduction of optics for space applications is neither easy nor rapid. This paper summarizes Alcatel Space research effort and the main results in this domain. I. Optics in broadband payloads In the next five to ten years, satellite operators are anticipating the creation of a new market for satellite: broadband communications. Typically, broadband systems should offer high data rate connections to very large numbers of low price terminals. The present generation of satellite is not really suited for broadband missions involving millions of end users. Ku and C bands are too congested to offer sufficient room for growth. Receive performances of the satellite are not sized for the use of small and power limited terminals. Multiple access schemes are not adapted, as there are, for managing tens of thousand simultaneous links. A new family of satellite shall be designed to cope with these unusual requirements. Lastly, to be economically viable, communication price shall be as low as possible. Only satellites with very large capacity in term of bandwidth or number of circuits would achieve low communication price. Several techniques are investigated to increase significantly the satellite capacity [1]. Broadband payloads will have complex multi-beam antennae, hundreds of channels to receive, to route and to transmit, large onboard processors for regenerating and switching digital signals... Optics and photonics bring unusual but attractive and performing solutions for implementing these functions. Optical techniques should be viable solutions to enhance existing functions in mid term. In the long term, optical techniques will be the only solution to create the new functions of the broadband satellites to come. II. Mid term utilization of optical techniques In mid term, optical techniques could complete or replace existing functions in communication payloads: digital intra-satellite links (Onboard Data Handling System), microwaves on optical fibers, gigabit backplane interconnections in high throughput On-Board Processor (OBP), high speed data packet switching, inter-satellite and inter-orbit links, pyrotechnic harness, signal interfaces of cryogenic electronic units... 21st International Communications Satellite Systems Conference and Exhibit AIAA 2003-2297 Copyright

Optical distribution of local oscillators in future telecommunication satellite payloads

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.

Advanced Microwave Optical Links for LO Distribution in Satellite Payloads

Microwave optical links can replace electrical cables and harnesses for master oscillator distribution. This paper presents optical links designed and optimized for transmission of Ku-band LO signals with high performance: the transmitter is based on the DSB-CS modulation technique, and the receiver consists in an injection locked photo-oscillator. Such a sub-system is well suited for the optical distribution of high spectral purity microwave signals to numerous receivers, as required in satellite payloads

A low phase noise optical link for reference oscillator signal distribution

Various circuits dedicated to high spectral purity signal transmission over fiber optics are presented. The main application investigated is the 10 MHz reference frequency distribution in various subsystems of a satellite payload. Our work has been focused on the receiver and more particularly on the RF signal conditioning at the receiver level, in order to minimize the phase noise degradation due to the optoelectronics elements. The advantage of the photo-oscillator solution has been emphasized.

Optically synchronized oscillators for low phase noise microwave and RF frequency distribution

Various circuits dedicated tohigh spectral purity signal transmission using fiber optics are presented. Three application types are investigated : reference frequency distribution at 10 MHz, IF distribution at 800 MHz and microwave synthesized signals at 3.5 GHz. The reception 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.

A flexible telecom satellite repeater based on microwave photonic technologies

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.

Assessment of commercial optical amplifiers for potential use in space applications

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.

Low phase noise optical links for microwave and RF frequency distribution

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