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A distributed optical fiber disturbance detection system consisted of a Sagnac interferometer and a Mach-Zehnder interferometer
is demonstrated. Two interferometers outputs are connected to an electric band-pass filter via a detector respectively. The central frequencies of the two filters are selected adaptively according to the disturbance
frequency. The disturbance frequency is obtained by either frequency spectrum of the two interferometers outputs. An alarm
is given out only when the Sagnac interferometer output is changed. A disturbance position is determined by calculating a
time difference with a cross-correlation method between the filter output connected to the Sagnac interferometer and derivative
of the filter output connected to the Mach-Zehnder interferometer. The frequency spectrum, derivative and cross-correlation
are obtained by a signal processing system. Theory analysis and simulation results are presented. They show that the system
structure and location method are effective, accurate, and immune to environmental variations. 相似文献
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