US 12,345,555 B2
Phase measuring method and signal processing device
Yoshifumi Wakisaka, Musashino (JP); Daisuke Iida, Musashino (JP); Keiji Okamoto, Musashino (JP); and Hiroyuki Oshida, Musashino (JP)
Assigned to NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
Appl. No. 17/595,065
Filed by NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo (JP)
PCT Filed May 21, 2019, PCT No. PCT/JP2019/020070
§ 371(c)(1), (2) Date Nov. 8, 2021,
PCT Pub. No. WO2020/234989, PCT Pub. Date Nov. 26, 2020.
Prior Publication US 2022/0221314 A1, Jul. 14, 2022
Int. Cl. G01D 5/353 (2006.01); G01H 9/00 (2006.01); G01J 9/00 (2006.01); G01M 11/00 (2006.01); G01V 8/16 (2006.01)
CPC G01D 5/35361 (2013.01) [G01H 9/004 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A phase measurement method comprising:
generating and directing, by a measurement device, a stream of light pulses into a measurement target optical fiber, where the stream of light pulses having N wavelengths multiplexed together therein and N is an integer equal to or larger than two;
measuring, by the measurement device, an in-phase component and an orthogonal component of scattered light from the measurement target optical fiber;
a selection procedure of sorting rays of the scattered light measured through the measurement procedure in descending order of light intensity, the rays corresponding to the respective wavelengths, and selecting a predetermined number p (p is an integer between 1 and N inclusive) of rays of the scattered light having the highest light intensities;
a vector acquisition procedure of acquiring, for each of the p wavelengths selected through the selection procedure, a two-dimensional vector constituted by an in-phase component and an orthogonal component at an arbitrary time and an arbitrary position in the measurement target optical fiber among the in-phase and orthogonal components of the scattered light;
a vector rotation procedure of rotating the two-dimensional vector acquired through the vector acquisition procedure for each wavelength at a reference time by a reference rotational amount for the wavelength so that the two-dimensional vector becomes aligned with a reference direction, and rotating the two-dimensional vector acquired through the vector acquisition procedure for each wavelength at other time different from the reference time by a reference rotational amount for the wavelength;
a calculation procedure of calculating a synthesis reference vector as an arithmetic average of the two-dimensional vector for each wavelength at the reference time, which is rotated through the vector rotation procedure, calculating a synthesis vector as an arithmetic average of the two-dimensional vector for each wavelength at the other time, which is rotated through the vector rotation procedure, and calculating a phase change amount of the scattered light based on an angle between the synthesis reference vector and the synthesis vector; and
outputting the phase change amount of the scattered light as the vibration of the measurement target fiber.