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This paper demonstrates the recent achievements in the field of distributed optical fiber sensor (DOFS). A novel type
of distributed optic fiber vibration sensor is presented to detect and locate a time-varying disturbance along the whole
fiber length. It measures the first simultaneous information by using Mach-Zehnder Interferometer(MZI). The sensor
consists of a MZI where two directional optical signals are simultaneously traveling. We discuss the principles of
distributed optic fiber vibration sensor based on long-length MZI, and present the preliminary results on the application
of distributed optic fiber sensor for the measurements of distributed signals in long-distance region. The sensor is
illuminated by one continuous-wave laser, which is different from the conventional scheme. The phase shift caused by
any disturbance around the fiber is detected and converted to the information on the perturbation position and amplitude,
which can be determined by combining two phase signals from the above device. In addition, we adopt a new technique
by using optical delay effect to improve the spatial resolution of distributed optic fiber sensor. It is completely different
from the spatial-resolution technique of optical time-domain reflectometry (OTDR). The system has capability for cross-correlation
algorithm and fast Fourier transform (FFT) analysis of the detected disturbance signals. For the sake of
determining the disturbance position and type, high speed digital processing (DSP) technology is used in the sensor
system, which can carry out all operations in real time and promote the resolution of localization. The hardware design
of the sensor is completed and the experimental results are obtained. This type of optic fiber sensor has better sensitivity
and resolution than the others. It achieves a 100Hz-20KHz frequency of vibration resolution, with 100-m practical
spatial resolution, over a sensing length of 8 km. At the time of writing, the system is only partially completed; therefore
the content of this paper will focus on the principle of distributed optical fiber sensor. The results mainly are presented in
laboratory.
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