Optical fiber distortion measuring device and optical fiber distortion measuring method

摘要

PROBLEM TO BE SOLVED: To provide an optical fiber strain measurement device that measures a change in the frequency of Brillouin backscattering light from a beat signal phase difference by coherent detection and removes a transmission loss and an offset due to transient response.SOLUTION: The optical fiber strain measurement device comprises a light source unit 10, a branch unit 42, a delay unit 48, a combining unit 50, and a subtraction circuit 76, the light source unit generating a probe light. The probe light is entered into an optical fiber 100 to be measured. The branch unit branches Brillouin backscattering light occurring in the optical fiber to be measured by the probe light into a first optical path and a second optical path. The delay unit, provided in either the first optical path or the second optical path, gives a difference in delay time between lights propagating down the first optical path and the second optical path. The combining unit combines the lights propagating down the first optical path and the second optical path and generates a combined light. The subtraction circuit calculates a difference between a phase difference signal obtained from the Stokes light of Brillouin backscattering light and a phase difference signal obtained from the anti-Stokes light of Brillouin backscattering light.SELECTED DRAWING: Figure 3