Low Cost Optical Avionics Data Networks (LOADNet)

Aircraft Technologies

Low Cost Optical Avionics Data Networks (LOADNet) Nicholas BROWNJOHN The LOADNet project focuses on the realisation of cost-effective European photonic network technology for next generation aircraft data communication systems, and the exploitation of the huge investment made by the commercial telecomms and datacomms sectors in fibre-optic technology.

t is the author's intention to provide an insight into some of the challenges associated with the development of a low through-life cost optical network infrastructure capable of supporting a wide range of applications on next generation aircraft.

Progression and constraint European citizens are witnessing an explosion in information technology. This is exemplified by the growth in electronic devices aimed at personal entertainment and communications, whether at home, in our cars or at the office. We can expect that next generation large aircraft figure 1 - (500 passengers or more) will need to satisfy' expectations for such services while at the same time delivering a wide range of avionics svstems with greater functionality, all of which will require ever increasing bandwidth and higher reliability from the on-board data communications network. The scale of this challenge is equivalent to providing information services for a small town! The delivery of sucln systems will place great demands on the communications infrastructure of fine aircraft, demands that will increasingly highlight current technology (i.e. copper) as becoming a constraint, in terms of bandwidth, reliability and maintainability. This problem has already been addressed and solved in other application domains by exploiting the tednnical benefits of fibre optics, e.g. in telecom-

Figure I. The Airbus 380,

munications. Indeed, much of tile world's communications infrastructure is underpinned by fibre optic technolo,w at least on the ground; but not so in the air... WHY?

Background The introduction of photonic technologies into airborne applications has long been seen as advantageous for reasons of operational performance as well as environmental robustness. To this end various fibre-optic links have been successfully implemented in production, mainly on military aircraft (in Europe and the USA) bu} also on some civil aircraft.

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Despite these technical successes, there have been only limited application,~ to date with unicjue technical/hardware solutions being generated for each relatively simple application. These are seen as significant steps forward, but they have highliglnted the lack of supporting infrastructure and standards for aerospace plnotonics, which has inhibited fine wider adoption of the technolog}. Thus, althougln these systems have in the main proved to b~, verx reliable (much more so tlnan equivalent electrical interconnects), they are prohibitively expensive to procure and maintain compared to copper. If we study the aerospace fibre optics market place we find a small, specialist,

Aircraft Technologies field that has evolved to satisfy a relatix ely limited range of requirements, in a unique way for each application. Each ~olution has been developed in isolation and has very rarely been based on a commercial (telecommunications) standard. This small market has been made even smaller by many pseudo-unique requirements, which in turn have restricted the possibility of exploiting commercial, offthe-shelf, (COTS) products. This approach has resulted in a market where too few 'players' exist for each of the developed aerospace solutions. Consequently, the full development costs have been born by each unique application, resulting in fibre optic solutions being prohibitively expensive compared to copper. A further complication in the aerospace fibre optics market is that the small volume requirement for each unique set of developed components is too small to sustain an effective supplier base. This has led to limited component availability, with single source being the norm. With little evidence of real market place competition coupled with supply chain instability (inability to support applications over a typical 25 years life cycle), it is understandable that aerospace manufacturers and operators have been reluctant to commit to fibre optic technology in a substantial way. Tile total market for aerospace equipment and components will alwavs be relatively small compared to other sectors, e.g. automotive, telecomms, etc. It will therefore be necessary to adopt a more co-ordinated approach to the development & delivery of solutions. One in which research and development activities are directed towards design for a broad range of related applications, rather than focused on specific implementations. While the current environment is characterised by design diversity it is clear that pragmatism and standardisation must drke future developments if fibre optics is to play a greater role in the aerospace arena.

LOADNet The European aerospace community

has recognised this need and has

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AVIONICS &

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embodied it into the Low cost Optical Avionics Data Networks (LOADNet) project. This is a 36 month activity, supported by the European Union as part of the Fifth Framework Programme aeronautics activity. The LOADNet partnership consists of partners from five different EU countries (table I), with expertise in all tile complementary areas (e.g. requirements capture; system design; component development and systems integration) necessary to achieve tile project objectives.

Project objective Tile LOADNet project aims to deliver the physical layer component technologies plus the supporting infrastructure necessary to enable tile cost effective application of fibre optic technology to commercial aircraft and other high integrity/harsh environment applications. This last point is important since it recognises tile need to greatly expand the application base ill order for the cost

of aerospace developed solutions to be driven down through higher volunles.

LOADNet goals LOADNet aims to exploit tile cost benefits associated with using standardised photonics components, both passive and active, derived where possible from con> mercial telecommunications products. One important implication of this strategy is that future aerospace fibre optic cables are likely to contain silica fibre with an outside diameter of 125t_ml, (whether multi-nlode or single-mode) in file majority of applications. The technical challenge is then to pro\ide a cable structure that can support single-mode or multi-mode fibres over the harsh operating conditions without adverse effects on fibre performance due to cable packaging construction. Furthernlore, for a fibre optic cable to be useful it must be compatible with connectors/terminals. In tile past, independently de\eloped cable and connectors have often been difficult to ternlinate. LOADNet will adopt a holistic approach and develop all optimised fibreoptic interconnect solution.

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EQUIPMENT

Table I. LOADNet Partners Airbus UK (Coordinator) BAE SYSTEMS CERT, ONERA DaimlerChrysler AG EADS Airbus GmbH EADS Airbus SA Framatome Connectors International

Institut fQr Mikrotechnik Mainz GmbH Nexans Harnesses Sistemas y Redes Telematicas - SIRE S.L. Smiths Industries University of Madrid University of Strathclyde

UK UK F D D F F D B E UK E UK

For the active components, generic high-speed transceivers need to be developed, which are capable of supporting multiple protocols in multiple applications, oxer tile foreseeable future, ideally also based on a re-packaged COTS d'evice(s).

LOADNet strategy The strategy for the project is based on maximish G tile take up of COTS ted> nologies across as wide all application base as possible within tile aerospace industry and beyond. Tlnis will mmimise physical laver costs and where non-COTS solutions have to be adopted will spread non recurring expenditure across an expanded market. As for any network, procurement of tile hardware is only one element of tile life cycle cost. Understanding tile throughlife implications of deploying all optical physical laver and minimising the associated costs will be critical ill ensuring affordabilitv and maximising uptake of the teclmol{Gy. An important component of the network's life-cvcle~cost is incurred during upfront design. LOADNet will reduce optical network perfornlance uncertainties and associated development costs b} providing enhanced modelling tools.

AIR & SPACE EUROPE o VOL. 3 • No 3/4

2001

LOADNET The final element to the strategy is to promote International Standards for the hardware and threugh-life support processes. Tlnis will help broaden the uptake of LOADNet solutions across the global market.

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The network pt3ysical layer devdopn3ents to be undertaken during LOADNet will clearly be strongly influenced by future avionic datacomms requirements. The project partners hax'e already compiled this information and arc in the process of correlating it with commercially available network standards. The main candidates at this stage are: • Fibre Channel; • Fast Ett~ernet 100Base FX, switched, full duplex; • Oigabit P]tJlelllt't; • ATM. This process will identify the likeh' netx~ark topologies and physical laver requirements for the future. Based on tt~cse network requirements, the fundamental elements of an optical datacomms system will be realised under LOADNet, e.g. cable, connectors, transmitters and recei\ers, in line with the core strategy.', where possible, these will be based on COTS technology. It is recognised, howe\'er, that significant repackaging and some aerospace specific development will be necessary. In parallel to the photonichardware devdopments, a modelling tool is being generated far the optical pt~ysical la\'er, (see t7
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Lmv cost hardware that incurs high cost oi: ownership is unacceptable. Techniques, method and tools to support optical networks from manufacturing through to in-service maintenance will be adopted from commercial practises, where possible. Because of the shorthaul nature of the networks and the diffictl]t operating environments, some specific adaptation and development will be necessary. In order to validate the COTS derived technologies and procedures, a number of aircraft datacomms system demonstrations will be built and tested later in the protect. The LOADNet strategy discussed earlier i> reliant on specifications fer the validated physical layer components and procedures being adopted by' relevant international standardisafion bodies. Those initially targeted include AECMA, ARINC, and the SAE.

Conclusions Past attempts at fibre optic network development have not delivered con> merciallv sustainable solutions te-date.

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In contrast, the LOADNet protect ha~, a robust strategy for the developnlent ota cost-effective infrastructure to support tile exploitation of optical datacomms networks on future civil aircraft programmes. Furthermore, the pragmatic approach adopted b\ I OAI)Net ufll ensure that the technology should find wider application across sectors such a defence, transport and industrial pro tess control. The earh findings of the project confirm thatthis is a viable approach. •

About the author: Nicholas Brownjohn is currently Engineering Team Leader within the Research Centre at Airbus UK,

and is responsiblefor overall management of the LOADNet project nicholas.brownjohn@baesystems,com