Optical fiber characteristics measurement apparatus and method of measuring optical fiber characteristics

An optical fiber characteristics measurement apparatus comprising:

• a first optical splitter configured to split a modulated light subjected to frequency modulation into a pump light and a reference light;
• a second optical splitter configured to cause the pump light to be incident on a fiber under test from one end and configured to extract Brillouin scattered light generated within the fiber under test;
• a modulator configured to change a frequency of at least one of the reference light and the pump light to a plurality of frequencies;
• and
• a circuit configured to detect a second harmonic component among frequency components of a signal yielded by homodyne detection of interference light between the Brillouin scattered light and the reference light at each frequency, and measure characteristics of the fiber under test based on the detected second harmonic component, the second harmonic component being a component having a frequency that is two times a modulation frequency of the modulated light.