Phase measuring method and signal processing device

Patent metadata

Field	Value
Publication number	US-12345555-B2
Application number	US-201917595065-A
Country	US
Kind code	B2
Filing date	May 21, 2019
Priority date	May 21, 2019
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

A phase measurement method is presented which causes wavelength-multiplexed pulsed light to be incident on a measurement target optical fiber, produces a scattered light vector obtained by plotting scattered light from the measurement target optical fiber for each wavelength onto a two-dimensional plane having the in-phase component thereof on the horizontal axis and the orthogonal component thereof on the vertical axis, rotates the produced scattered light vector for each wavelength at each place in the measurement target optical fiber to align the directions of the vectors, generates a new vector by calculating the arithmetic average of the vectors having the aligned directions, and calculates the phase by using the values of the in-phase and orthogonal components of the generated new vector.

First claim

The invention claimed is:

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.

2. The phase measurement method according to claim 1 , further comprising:
measuring distribution D (Pi) of intensity Pi of the scattered light of a wavelength i at an arbitrary time and an arbitrary position in the measurement target optical fiber, and a noise level Noise at acquisition of the two-dimensional vector constituted by an in-phase component and an orthogonal component of the scattered light;
randomly generating, by a calculator, X (X is an arbitrary positive integer) lengths |r(x, i)| (x=1, . . . , X) of the two-dimensional vector of the scattered light of the wavelength i so that a squared value of each length |r(x, i) | obeys the distribution D (Pi);
sorting the lengths |r(x, i) | in descending order, calculating an average value |r′ (x, p′) | of the longest p′ lengths |r(x, i)|;
calculating a phase detection sensitivity of each average value |r′ (x, p′) | that satisfies Expression B1 by using Expression B2;
comparing an average value ε(p′) of the phase detection sensitivities with an arbitrary reference sensitivity ε; and
setting the predetermined number p to be a minimum p′ that satisfies ε≥ε(p′)

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3. A phase measurement method comprising:
generating and directing, by a measurement device, a stream of light pulses into a measurement target optical fiber

Assignees

• Nippon Telegraph & Telephone

Inventors

• Wakisaka Yoshifumi
• Iida Daisuke
• Okamoto Keiji
• Oshida Hiroyuki

Classifications

• G01H9/004 Primary

  using fibre optic sensors (light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125) · CPC title

• G01D5/35358

  using backscattering to detect the measured quantity · CPC title

• G01D5/35361 Primary

  using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering · CPC title