Abstract
A distributed fiber-optic sensor system is proposed and demonstrated for
long-distance intrusion-detection, which employs the hybrid time/wavelength division
multiplexing architecture. The sensing elements are single-mode telecommunication fiber
which can be hanged on the fence and hedge or buried along the monitored perimeter. The
pulsed light generated by the superluminescent diode was filtered by the filter which
has multichannel (m = 6), and then amplified by erbium-doped fiber amplifiers. A
1 × (n+1) (n=20) splitter of which every port has a fiber delay coil except
the first port splits the amplified light. The fiber delay coils have different lengths,
which generate different delay time and produce n time zones. By utilizing the m channel
dense wave-length division multiplexing modules, every fiber sensing unit (OSU)-based
unbalance Mach–Zehnder Sagnac interferometer technology occupy a time zone and a
wavelength. By utilizing 20 time zones and 6 wavelengths, the system contains up to 120
OSUs, of which the distributed sensing distance is from 0 to 500 m. So, the whole
sensing distance of this system could reach 60 km. The system has been demonstrated to
stably run over six months with the false alarm rate of less than 4%.
© 2011 IEEE
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