Optical fiber characteristic measurement device and optical fiber characteristic measurement method

An optical fiber characteristic measurement method comprising:

• detecting, by a photodetector, Brillouin scattered light obtained by causing light to be incident on an optical fiber;
• acquiring, by an intensity acquisitor, a signal intensity at a prescribed reference frequency from a detection signal output from the photodetector;
• measuring, by a measurer, characteristics of the optical fiber by obtaining a peak frequency of a Brillouin gain spectrum, which is a spectrum of the Brillouin scattered light, from the signal intensity at the reference frequency acquired by the intensity acquisitor;
• outputting, by a light source, frequency-modulated continuous light;
• branching, by a first optical branching part, the continuous light into pump light and reference light;
• causing, by a second optical branching part, the pump light to be incident on one end of the optical fiber;
• and
• outputting, by the second optical branching part, the Brillouin scattered light generated in the optical fiber;
• wherein the photodetector comprises a first separation element, a second separation element, a first detector, and a second detector, and
• wherein the optical fiber characteristic measurement method further comprises:
• separating, by the first separation element, the reference light into first reference light and second reference light whose polarization directions are perpendicular to each other;
• separating, by the second separation element, Brillouin scattered light into first scattered light whose polarization direction is the same as that of the first reference light and second scattered light whose polarization direction is the same as that of the second reference light;
• detecting, by the first detector, interference light between the first scattered light and the first reference light;
• and
• detecting, by the second detector, interference light between the second scattered light and the second reference light.