Overview
The necessity of finding a practical solution for onboard detection of atmospheric hazards such as wake vortices, wind shear, and clear air turbulence is a well-established need, and has been the subject of intense European research in programmes such as MFLAME and now I-Wake. LIDAR has been shown to be an optimal tool for on-board detection of hazards. LIDAR systems used so far have been based on solid-state laser technology, which does not meet commercial aircraft requirements for onboard implementation due to power consumption, size, weight, reliability and high life cycle cost.
The purpose of this programme was to introduce the next logical step in wake vortex detection by developing a unique fibre laser technology (1.5 micron wavelength) geared for the aerospace industry requirements, enabling on-board realisation of a LIDAR atmospheric hazard detection system. The goals of this programme meet the Sixth Framework Programme strategic objectives including 'Improving Aircraft Safety and Security' and 'Increasing the Operation Capacity of the Air Transport System'. The numerous aerospace applications require both a high-level coherence and high energy per pulse, an issue which has not been addressed in the telecommunications and industrial laser technologies, hence the essential need to bridge this technological gap in fibre laser systems for aerospace applications. The fibre laser-based LiDAR to be developed in this programme will enable a major technological breakthrough attainable only at a European level with participation of the major European laser and aeronautics companies. The synergy with other EU programmes will enable the technological breakthrough essential in realising a feasible on-board aircraft safety system.
The expectations of the project include the realisation of a LiDAR system capable of accurately measuring the wake vortices and geared for on-board implementation. The fibre laser technologies will enable the leap forward to on-board implementation. The system will be designed so that solutions to the various on-board restraints, including power consumption, footprint, heat dissipation, environmental robustness, flexibility, etc. will be taken into consideration. The signal processing developed during FIDELIO will enable the move to real-time processing, demonstrating further convergence towards an on-board system.
The development of the fibre laser-based Lidar system was a challenging task. Hence, the programme has been structured in a manner that enables risk reduction in order to reach the desired goals. The Work Packages were broken down into the following topics:
- Programme coordination and management (lead by ELOP),
- System Specification and LiDAR Modelling (lead by ONERA),
- Laser Architecture and Modelling (lead by Thales Research & Technology),
- Fibre Development and Fabrication (lead by IPHT),
- Laser System Integration (lead by ELOP),
- LiDAR System Realisation (lead by ONERA), and
- Exploitation (lead by Thales Avionics).
The system specification was based upon previous EC programmes and would be geared specifically to the onboard requirements (size, power consumption, etc.). The fibre laser development was very challenging and includes high-energy requirements, single mode operation, single frequency, polarisation maintaining, and more. In order to reduce the risks in the programme, the initial stages of laser development would focus on three possible fibre laser architectures, each with their own advantages and disadvantages. It was envisaged, after 18 months, the leading laser architecture to be decided upon and that architecture to be implemented in the final laser-engineering prototype. The fibres themselves were a critical building block in the system and hence much effort would be placed in the development of fibres able to meet all of the demanding requirements (single mode, high energy, polarisation maintenance, etc.). The engineering fibre laser prototype would be implemented in the LiDAR system where particular attention will be placed to the (real-time) signal processing and system testing.
The testing included ground testing at the end of a runway to measure the wake vortices. Although, due to budgetary limitations, the testing was envisaged to be performed on the ground and the system developed so that the move to on-board implementation would be as smooth as possible. Exploitation would be a constant theme in the course of the programme, where a Users Club has been established (members include Dassault) to provide input to the relevant market and end-user needs. The I-Wake programme, which was in its final phases, would also be a source of input to the needs and requirements of the on-board system and so a synergistic use of the EC-funded projects would be seen.
Funding
Results
FIDELIO project has generated important advances in research and development on fiber laser technology:
- An innovative high brightness pulsed 1.5μm laser source has been built, based on a MOPFA architecture with a large core fiber. The beam quality is excellent (M2=1.3). Achieved pulsed energy is 120μJ with a pulse repetition frequency of 12kHz and a pulse duration of 800ns. With a further amplification stage, 750μJ pulses were obtained in the lab at 5kHz and 1μs with excellent beam quality.
- A Doppler heterodyne LIDAR has been developed based on the 120μJ laser source with a high isolation free space circulator. The LIDAR includes a real time display of the wind field. Wind velocity dispersion is post-processed.
- Field tests were carried out at Orly airport in April 2008. Axial aircraft wake vortex signatures have been successfully observed and acquired at a range of 1.2km with axial resolution of 75m for the first time with fiber laser source.