Applications of High Frequency Linear Fiber-Optic Links in Defense Systems

Abstract

Military aircrafts venturing into harm ways are subjected to missile and antiaircraft artillery attacks guided by RF interrogations from radars on the ground, on intercepting combat aircrafts and on the seeker head of homing missiles. To protect aircrafts against these threats, electronic countermeasures are deployed – in essence detecting and processing of the interrogating radar signals to generate a false return signal that overwhelms the actual return signal from the radar cross section of the aircraft itself. It is preferable that the false return signal be radiated from a high power amplified source located at a substantial physical distance away from the aircraft, to avoid the chance of an accidental acquisition and lock of the radar return from the aircraft. One such system in production is the AN/ALE-55 offered by BAE Systems [228], an aerospace defense company headquartered in the UK. Figure G.1 shows a schematic diagram of this system. Detected interrogating or homing radar signals are processed by countermeasure electronics on board the aircraft where false radar return RF signals are generated, which are then transmitted via a linear fiber-optic link to a decoy towed at a substantial distance behind the aircraft. The received RF-modulated optical signal inside the decoy is then amplified by a high-power RF amplifier and broadcasted. The high radiated RF power from the decoy makes it the preferred target for homing threats.