Objective
Main Objective
The primary objective of the project is to analyse and to realise a complete optical transmission link able to work in the space environment with a minimum bit rate of 2.4 Gbit/s. Satellite networks will play a key role in the development of world-wide communications. They can offer a wide range of Mobile Satellite Services (MSS) and Fixed Satellite Services (FSS). Low Earth Orbit (LEO) constellation systems will provide real time communication and data transmission services. Major future networks are :
-Celestri:data rate 4.5 Gbit/s (FSS)
-Iridium 2:data rate 25 Mbit/s (MSS)
-Teledesic:data rate 2.5 Gbit/s (FSS)
The objective of the project is to demonstrate a complete transmission link able to be used in the future constellations. Main decisions, such as wavelength selection, will be evaluated at the beginning of the project to make the right technological trade-offs.
Technical Approach
The Demonstrator realised in the OSC project is based on the preliminary specifications coming from mission specifications (such as the SILEX project). The main aspect of the space environment conditions (especially thermal aspects and the radiation environment) will be analysed in detail and applied to the existing terrestrial components used for STM16 transmission at 1.55 µm (DFB laser modules, fibre amplifiers, etc.). Specification of Laser and Communication Electronics (LCE) will be added to demonstrate a complete LCE system, as well as Beacon and active alignment devices (necessary between the telescope and the single mode fibre link input).
Intersatellite optical link power budget is in the range 68 to 71 dB and implies the use of a fibre booster amplifier on the transmitter side and a fibre amplifier (used as a preamplifier) on the receiver side. The demonstration will be focused only on a booster amplifier realisation able to work under space radiation.
The work is divided in four parts :
-A system aspect with system consolidation, system performance evaluation and simulation;
-The architecture and design with the development of the Transmitter module, Receiver module and LCE;
-Functional tests implementation;
-Technology validation with the main developments of:
a. optical booster fibre amplifier with the associated 980 nm pump lasers,
b. radiation test,
c. a breadboard of an active alignment devices.
Summary of Trial
A key aspect of the project is the development of demonstration hardware to implement a " complete " intersatellite link in terms of optical power budget, including all the main heating circuits, in order to evaluate the over-all environment conditions, such as thermal and irradiation aspects, on the complete demonstrator. To minimise the technical developments, only one fibre amplifier will be included in the demonstrator; the preamplifier will be mounted as a part of the optical path, placed here to simulate the optical attenuation. The above equipment will be implemented in such a manner as to be transportable, mainly for performance of the irradiation tests.
Expected Achievements
Demonstration of a complete intersatellite optical link at 2488 Mbit/s requiring a large optical budget, using fibre amplifiers (one booster amplifier, one pre-amplifier) and able to be used under an irradiation level of 100 krad. Breadboarding of an active alignment device demonstrating that single mode fibre pigtails can be used also on the pre-amplifier side.
Expected Impact
Realisation of a complete LCE demonstrator, including the main optical components or materials able to work in the space environment with evolutionary bit-rate capability (more than one wavelength could be used). All the main technologies will be available for future real space development of high bit rate LCE equipment.
Main contributions to the programme objectives:
Main deliverables
A communication box built from existing components available for terrestrial links and adapted to the specificities of Optical Space Communication where mass power consumption and radiation hardness are key parameters
Contribution to the programme
Contributes to the development of the optical part of the next generation of Intersatellite transmission links by 2002 or 2003
Key Issues
Key issues are first to analyse the system aspects to select the best wavelength window for the intersatellite optical link, correlated to maximum bit rate capability, number of channels (if wavelength-division-multiplexing, WDM, is used), optical power budget, mass and volume of a complete LCE.
The advantage of inter-operability between any terminals has been recognised and implemented in MMS patented design. Two separate telescopes associated with a suitable implementation of sources and detectors allows this requirement to be complied with. Instead of adding complexity, this elegant concept offers many advantages:
-all terminals fully identical
-no flip flops necessary (avoiding also co-alignment issues)
-no duplication of communication transmit and receive hardware.
Concerning the optical head architecture, the adaptation consists of implementing accurate reception alignment for efficient coupling into the reception pre-amplifier (single mode fibre). The fibre core centre alignment accuracy (around 5 µrad) requires an active alignment device.
One of the key technological aspects is a the fibre amplifier able to work under radiation, which is not the case of standard erbium doped fibres. The booster amplifier realisation with the associated laser pumps is one of the key points of the system.
The Transmitter and the Receiver modules are based on terrestrial optical components adapted to or selected for the space environmental requirements. The development of these two boards will take into account the space rules necessary for that kind of development.
The beacon circuits will use laser modules available on the market with specific electronic circuits developed also in the same spirit and rules as above. The complete LCE demonstrator will consequently be close to the space requirements, except for mechanical aspects, mass and size.
Fields of science (EuroSciVoc)
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques. See: The European Science Vocabulary.
- natural sciences chemical sciences inorganic chemistry transition metals
- engineering and technology mechanical engineering vehicle engineering aerospace engineering satellite technology
- natural sciences physical sciences optics laser physics
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Coordinator
91401 Orsay
France
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