Patent ID: 9726573
Date: 2017-08-08
CPC Classifications: G01B,G01L,G01M,G02B

Claim:
1. An optical frequency domain reflectometry method comprising: a step of generating measurement light and reference light having the same wavelength sweep characteristic as wavelength swept light from wavelength swept light which is swept in a wavelength continuously in a predetermined range; a step of outputting the measurement light to a measurement-target optical fiber having a fiber Bragg grating with a chirped grating interval; a step of receiving the reference light and generating polarization multiplexed reference light by multiplexing a first reference light and a second reference light resulting from splitting the reference light into a first split reference light and a second split reference light, and applying polarization orthogonality and a predetermined time difference between the first split reference light and the second split reference light, wherein the predetermined time difference is shorter than a time during which a light reciprocates the fiber Bragg grating; a step of receiving reflected light from the measurement-target optical fiber with respect to the measurement light, combining and inputting the reflected light and the polarization multiplexed reference light to a photodetector, and outputting a beat produced by interference of the reflected light and the polarization multiplexed reference light as an electrical signal; a step of converting the electrical signal to a digital signal; a step of dividing a time domain of the digital signal by a single wavelength sweep into a plurality of periods during which a beat frequency produced by interference of the reflected light and the first reference light included in the polarization multiplexed reference light and a beat frequency produced by interference of the reflected light and the second reference light included in the polarization multiplexed reference light do not overlap each other and performing Fourier transform processing on the digital signal; and a step of synthesizing Fourier transform results obtained for the plurality of periods on a distance axis to obtain a measurement result of two orthogonal polarization components of the reflected light.