OPTICAL FIBER TEMPERATURE DISTRIBUTION MEASUREMENT DEVICE AND METHOD OF MEASURING OPTICAL FIBER TEMPERATURE DISTRIBUTION

An optical fiber temperature distribution measurement device configured to receive Raman back scattering lights obtained by inputting a pulsed light into an optical fiber and to measure a temperature distribution along a longitudinal direction of the optical fiber is provided. The device includes a first filter device. The first filter device includes: a threshold value setting circuit configured to set a threshold value in accordance with a change in an amount of noise overlapped with a measured signal, the measured signal indicating one of an intensity distribution and a temperature distribution of the Raman back scattering lights along the longitudinal direction of the optical fiber; a filter configured to eliminate a frequency component of the measured signal, the frequency component being larger than a predetermined first frequency; a determination circuit configured to determine if the measured signal is over the threshold value; a synthesizing circuit configured to select and synthesize one of the measured signal processed by the filter and the measured signal unprocessed by the filter in accordance with a determination result from the determination circuit.