Patent ID: 8144314

Claim:
A spectral measurement apparatus measuring spectral changes of Brillouin scattered light generated within an optical fiber for being provided to an object, comprising: a light source outputting pumping light and probe light which are to be caused to enter in opposite directions to each end of the optical fiber; a probe light output-end for supplying the probe light outputted from said light source to one end of the optical fiber; a pumping light output-end for supplying the pumping light outputted from said light source to the other end of the optical fiber; an analysis section for analyzing a gain received by the probe light as a result of Brillouin scattering which is generated due to the propagation of the pumping light within the optical fiber; and a judgment section for judging the existence of a anomaly relating to a temperature or strain of the optical fiber on the basis of the analysis result of said analysis section, wherein a frequency difference between the pumping light and the probe light, propagating within the optical fiber, is in a range including a frequency difference at which a peak value of the reference gain spectrum of the gain received by the probe light is obtained when the temperature or strain of the optical fiber is in a reference state, and is set within a frequency difference setting range equal to or less than a line width of the reference gain spectrum.