OPTICAL FREQUENCY DOMAIN REFLECTOMETRY, OPTICAL FREQUENCY DOMAIN REFLECTOMETER, AND DEVICE FOR MEASURING POSITION OR SHAPE USING THE SAME

摘要

To eliminate a need for polarization adjustment, to simplify a configuration, and to make a configuration at low cost. Wavelength swept light is provided to a measurement-target optical fiber having an FBG with a chirped grating interval. A polarization multiplexing unit generates polarization multiplexed reference light by multiplexing first reference light and second reference light, which are swept in a wavelength in the same manner as wavelength swept light and have polarizations orthogonal to each other. Polarization multiplexed reference light is input to combine means along with reflected light from measurement-target optical fiber and is made to interfere with reflected light. A signal processing unit performs Fourier transform processing on the digital signal by dividing a time domain into a plurality of periods, and synthesizes the Fourier transform results on a distance axis to obtain a measurement result of orthogonal polarization components of reflected light.

主权项

1. An optical frequency domain reflectometry 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 first reference light and second reference light having polarizations orthogonal to each other with a predetermined time difference shorter than a time during which 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.