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4 November 2004 All-optical SOA latch fail-safe alarm system
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Emergency alarm systems, for example, that switch off critical processes in process plant, are vulnerable to deliberate or accidental sabotage through coupling of electromagnetic pulses (EMP) to wires and/or from sparks due to broken wires. A proposed system significantly reduces vulnerability by using a fast all-optical latch in conjunction with an optical sensor and optical fibers. Sparks cannot be created on breaking an optical beam and electromagnetic field transients have negligible effect on optical signals. The optical latch uses optical semiconductor amplifiers (SOAs) configured to form a flip-flop. The flip-flop latches after the occurrence of an intrusion that may be as short as a few nanoseconds, much faster than most environmental changes occur. Detection of an emergency or any break in connections causes the light to drop, triggering the alarm. Computer simulation shows that the all-optical latch is fast and effective.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Alastair D. McAulay "All-optical SOA latch fail-safe alarm system", Proc. SPIE 5556, Photonic Devices and Algorithms for Computing VI, (4 November 2004);

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