High Performance Photonic Avionics Networking using WDM Robert D. Gardner, Ivan Andonovic, David K. Hunter [r.gardner, i.andonovic, d.hunter]@eee.strath.ac.uk Optoelectronics Division, Department of Electronic and Electrical Engineering, University of Strathclyde, Royal College Bldg, George St., Glasgow G1 1XW, UK. Andrew J. McLaughlin, J. Stewart Aitchison, John H. Marsh [A.McLaughlin, JSA, J.Marsh]@elec.gla.ac.uk Optoelectronics Research Group, Department of Electronics and Electrical Engineering, University of Glasgow Rankine Building, Oakfield Avenue, Glasgow G12 8QQ, UK. Abstract—Photonic networking technologies have the potential to revolutionise future military aircraft data communications, delivering substantial improvements in networking performance, reliability, cost and security. More particularly, wavelength division multiplexing (WDM) can provide a huge bandwidth-to-weight ratio as well as enhanced routing flexibility, connectivity and network survivability. In this paper, the envisaged functional and operational requirements of next-generation avionics communications architectures are first discussed. Then a suitable high performance, high connectivity photonic network architecture is proposed, which, for the first time, uses a novel adaptation of Wavelength Division Multiplexing (WDM) to enable operation in the hostile aerospace environment without additional environmental conditioning. COTS compliance, protocol support and the relative performance of various operating modes are also examined. 1. INTRODUCTION Overview Photonic networking has the potential to revolutionise next- generation civil and military avionics communications systems. The high bandwidth-to-weight ratio, performance and routing flexibility offered by the combination of single mode optical fibre and wavelength division multiplexing (WDM) are among the prime attractions justifying the photonic network approach to on-board avionics communications systems. The proven reliability and robustness of optical networks in the telecommunications industry, chemical inertness and the increased immunity to electromagnetic interference provide further justification. Furthermore, there are growing pressures in the aerospace industry nowadays towards the use of commercial off-the- shelf (COTS) technologies and components [2,4,5], which are becoming increasingly readily and cheaply available. Together with an integrated modular approach to system design and interconnection, where possible, the use of open, COTS technologies aims to allow significantly reduced system development, deployment and life-cycle costs. However, stringent aerospace requirements and the unique restrictions imposed by the hostile operating environment, dictate that a direct mapping of techniques and technology from the maturing telecommunications sector is not possible. This paper outlines work carried out under the PHONAV (Photonic Networks for Avionics) project whose aim is to identify mainstream optical networking concepts applicable to avionics and define suitable network architectures and protocols for a global optical bus, using devices that can operate under hostile aerospace operating conditions. In Section 2, a brief overview of the requirements and design constraints of an avionics network capable of functioning in the aerospace environment is given. Sections 3 to 5 describe work carried out towards the development of a next- generation fibre-optic architecture for avionics communications that uses a novel adaptation of WDM, enabling operation in the harsh environment without environmental conditioning. Other features of the network are fault tolerance, application-oriented operating modes and open support for common transport protocols. 2. REQUIREMENTS OF A MILITARY AVIONICS DATABUS The requirements of an avionics databus can be broadly grouped into the categories physical, functional, environmental and cost/life-cycle. Physical Requirements The physical requirements specify the size, weight and power constraints of the networking equipment, as well as safety considerations relating to its operation and maintenance [1]. Hazards include eye damage from accidental viewing of coherent light sources (outside the visible spectrum), electrocution, small diameter fibres leading to puncturing of the skin, toxicity and flammability of materials and of chemicals required/released during maintenance procedures. Use of WDM technology offers a significant weight and size advantage over copper cabling and even spatially multiplexed optical systems because of the resulting decrease in the number of optical fibres and, consequently, fibre connectors required. The electronic bottleneck associated with TDM systems is also alleviated. However, in common with medium to long-distance, optical fibre-based communications systems, the use of coherent laser sources poses a potential eye hazard. This can be avoided by using low-power optical sources with amplification stages provided in the network. On the toxicity and flammability question, optical fibre cables manufactured for aerospace applications use non- flammable, noncorrosive materials such as glass yarn strength members and fluoropolymer buffer sheaths. The fluoropolymer materials are very stable at high temperatures and generate very little smoke when burning. These materials 0-7803-5538-5/99/$10.00 (c) 1999 IEEE