Optische Zeitbereichsreflektometer mit vermindertem periodischen Rauschen

In an optical time domain reflectometer, an optical pulse output unit supplies optical pulses intermittently to an optical fiber to be measured in accordance with the input timing of a cyclic signal. In response to the intermittent supply of the optical pulses, a reflected light data sampling unit samples the signal obtained from the optical fiber while the optical pulses are being supplied, while a noise data sampling unit samples the signal obtained from the optical fiber when the optical pulses are not supplied. Each of two or more groups of reflected light data and noise data obtained by the above sampling operations is averaged. After the averaging operations, an waveform data operating unit subtracts the noise data from the reflected light data in the common mode components corresponding to each other in terms of time, and then transforms the resultant data logarithmically to thereby operate the waveform data thereof.