The present disclosure aims to reduce crosstalk between different optical frequency components, and reduce erroneous detection of vibration and distortion of a vibrational waveform.
The present disclosure relates to a vibration measuring instrument that repeatedly injects a plurality of light pulses with different optical frequencies into an optical fiber, and performs distributed acoustic sensing-phase (DAS-P). In the vibration measuring instrument, light pulses having a waveform with a spectral side lobe smaller than a side lobe of a rectangular wave are used as the plurality of light pulses.