Optical fibre – cleared for take off … ?

Citation

(2009), "Optical fibre – cleared for take off … ?", Aircraft Engineering and Aerospace Technology, Vol. 81 No. 2. https://doi.org/10.1108/aeat.2009.12781baf.001

Optical fibre – cleared for take off … ?

Article Type: Features From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 81, Issue 2

Geoff Andrews, Commercial Director at fibre-optic design tool vendor trace technologies, discusses the use of fibre-optic technology in the aerospace arena and examines future challenges for the technology.

The demands of modern aerospace avionics systems require both an increased use of networking technologies, as well as an increase in the capacity of such networks. These days, it is not unusual to find links of 1 Gbps or higher being incorporated into new aircraft designs.

However, at these data rates, the transmission medium of preference is usually fibre optic cable – partly because traditional copper media tends to perform poorly at such rates and partly because copper suffers from significant performance loss over distances greater than a few metres. There is also a considerable weight saving through the use of fibre optic cable – an increasingly important issue with todays (and tomorrow’s) high performance and energy-efficient aircraft.

But, while fibre-optic technology in aerospace use expands and develops in a number of interesting ways, in other ways it remains firmly stuck in the past. Specifically, the way optical fibre links are designed and the way problems are diagnosed has more in common with the “trial and error” development principles of the Wright Brothers than with any modern and efficient approach to fibre-optic network systems design.

Combine that with the fact that troubleshooting a fibre-optic link generally requires the intervention of a skilled technician using sophisticated diagnostic equipment and it becomes easy to understand why the use of fibre-optic systems is not more widespread. The biggest problem is that there has not been a design tool available that enables engineers to “prove” the integrity and performance of fibre-optic links before time, money and effort is invested in their construction. But all that is about to change.

Historically, the main users of optical fibre technologies have been the military, with applications having been designed and used since the mid-1980s. With the advent of increased bandwidth and data rate requirements for systems utilising real time video, the commercial aircraft industry tentatively moved into the fibre-optic world, initially with the Taxi Aid Camera System on the Airbus A340-600 and subsequently the IFE, HUD and ETACS systems on the Airbus A380.

Boeing was the first to implement fibre onto the early Boeing 777, with its Avionics Local Area network, but this was an in-house development using their own designed transmitters and receivers and using the established standard fibre distributed data interface as the data carrier. Ironically, this system is now obsolete and not used on current build B777s. Boeing is now installing fibre-optic systems onto the B787 Dreamliner, including IFE (in flight entertainment) and partial integration into the aircraft’s AFDX avionics backbone.

In the past two years, there has been increasing interest in using fibre-optic technology as a data carrier from a far wider range of aircraft manufacturers including Lockheed Martin, Airbus, Boeing, Northrop Grumman, Gulfstream, Bombardier, Embraer, Agusta Westland and Eurocopter – in other words, a good majority of the world’s current aircraft builders.

Furthermore, a number of military providers are updating existing platforms to capitalise on the use of fibre-optic technology, with Northrop Grumman playing a particularly high-profile role in this sector, with its E-2D Hawkeye upgrade programme for the US Navy. Currently the aircraft is using Singlemode fibre but the next programme of updates will also incorporate multimode fibre for the majority of onboard systems including comms, navigation, electronic warfare, mission processing, core computing, all sensors, displays and cabin systems.

Within the commercial aircraft industry areas that are being evaluated for implementation of fibre-optic technology include cabin communication with video (internal/external), IFE and communications over a common fibre-optic network.

The final area of growth is in the business jet market. Many aircraft manufacturers are now looking at how to provide the maximum amount of information and entertainment to their customers, using the latest technologies, without incurring additional weight penalties. Optical fibre provides these benefits.

Clearly an advanced fibre-optic systems design tool has a place in all of these areas and can provide immense benefits during the communications link design phase. One example where this has recently proved clearly evident was the case of a well-known aircraft manufacturer that designed a point-to-point system using “traditional” manual calculations of optical power availability against the expected losses of the physical layer (cable/connectors).

Upon building the bench design, the system did not work because the physical layer losses were lower than calculated and the receiver was saturated. This required a major redesign and review of the calculations, which in turn led to additional labour and time costs incurred.

Using a tool like Trace’s “PISD” would have enabled the design to have been drawn and tested within hours, and would have provided the design engineers with the relevant information in a very short period of time, eliminating the need to purchase costly parts, time to build and test the design and the subsequent costs incurred because of the redesign and recalculation of the system operating parameters.

Clearly, the opportunities for optical fibre communications technologies within the aerospace industry are self-evident – but the efficiencies and cost benefit potential offered by fibre are currently obviated by out-dated and – in some cases – down right inaccurate design methodologies. This needs to change before the true potential of high-performance optical fibre can be realised.