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An optical fiber optic sensor for detecting land displacement is discussed in this paper. The sensor system consists of a
laser at wavelength 1.3 um, optical fiber coupler, optical fiber as sensor and light transmitting media, PIN photodiodedetector
system, data logger and personal computer. Sensor was made from a curved optical fiber with diameter 35 mm,
which will be changed into a heart-shape fiber if it is pulled. The heart-shape fiber sensor is the modification of the
earlier displacement fiber sensor model which was in an ellipse form. Light to and from the optical fiber sensor was
transmitted into a length of a multi core, single mode optical fiber cable. The scheme of the optical displacement sensor
system has been described here. Characterization in the laboratory has been done by applying a series of pulling
mechanism, on the heart-shape fiber sensor; which represents the land displacement process. Characterization in the
field was carried out by mounting the sensor system on a scaled-down model of a land slope and artificially reproducing
the landslide process using a steady-flow of artificial rainfall as the trigger. The voltage sensor output was recorded
during the artificial landslide process. The displacement occurence can be indicated from the declining of the sensor
signal received by the detector while the reference signal is steady. Characterization in the laboratory resulted in the
performance of the optical fiber land displacement, namely, sensitivity 0.027(mV/mV)/mm, resolution 0.37 mm and
measurement range 30 mm; compared with earlier optical fiber sensor performance with similar sensitivity and
resolution which works only in 8 mm displacement range. Based on the experiment of landslides simulation in the field,
we can define a critical condition in the real situation before landslides occurence to take any measures to prevent more
casualties and losses.
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