The role of the Advanced Air Transportation Technologies program undertaken at the NASA Glenn Research Centers has been focused mainly on the improvement of air transportation safety, with particular emphasis on air transportation communication systems in on-board aircraft. The conventional solutions for digital optical communications systems specifically designed for local/metro area networks are, unfortunately, not capable of transporting the microwave and millimeter RF signals used in avionics systems. Optical networks capable of transporting RF signals are substantially different from the standard digital optical communications systems. The objective of this paper is to identify a number of different communication link architectures for RF/fiber optic transmission using a single backbone fiber for carrying VHF and UHF RF signals in the aircraft.
To support these architectures, two approaches derived from both hybrid RF-optical and all-optical processing methodologies are discussed with single and multiple antennas for explicitly transporting VHF and UHF signals, while the relative merits and demerits of each architecture are also addressed. Furthermore, the experimental results of wavelength division multiplexing (WDM) link architecture from our test-bed platform, configured for aircraft environment to support simultaneous transmission of multiple RF signals over a single optical fiber, exhibit no appreciable signal degradation at wavelengths of both 1330 and 1550 nm, respectively. Our measurements of signal to noise ratio carried out for the transmission of FM and AM analog modulated signals at these wavelengths indicate that WDM is a fiber optic technology which is potentially suitable for avionics applications.
KEYWORDS: Control systems, Telecommunications, Switching, Antennas, Local area networks, Optical fibers, Control systems design, RF communications, Actuators
In this paper, we present the findings of a study on the radio frequency (RF) signal switching and distribution techniques in a civil aviation aircraft. Using the Boeing Aircraft 777 as a model, method and mode of RF signal switching and distribution were investigated. The aim is to evaluate system performance and if possible determine methods of improvement. The performance of the system was measured in terms of savings in system parameters such as weight, size and length of the associated components. Instead of using coaxial cables or twisted pair wire for routing the RF signals, optical fibers cables were suggested as a method of improvement. During this study, the difficulty of achieving this objective became obvious due to the complexity of the problem. However, suggestions were made on possible methods of improvements.
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