According to the present invention, a spatially-selective Brillouin distributed optical fiber sensor comprises: a test optical fiber; a light source unit using a main modulation signal with a first frequency and a sub modulation signal with a second frequency to generate a double-modulated laser beam; an optical modulation unit using the laser beam of the light source unit to generate a pump optical signal and a probe optical signal and apply the pump and probe optical signals to the test optical fiber from a direction different from each other; and an optical detection unit to detect Brillouin scattering light generated by the pump optical signal and the probe optical signal in a relation point located on the test optical fiber. The optical modulation unit uses a gating signal of a pulse type having a third frequency to time-gate the pump and probe optical signals. According to the present invention, the a spatially-selective Brillouin distributed optical fiber sensor applies optical time-gating and frequency double modulation; thus providing an advantage capable of remarkably increasing the number of effective measurement points in comparison with an existing sensor device.
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