公开(公告)号：US20220221314A1

公开(公告)日：2022-07-14

申请号：US17595065

申请日：2019-05-21

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yoshifumi WAKISAKA ,  Daisuke IIDA ,  Keiji OKAMOTO ,  Hiroyuki OSHIDA

IPC: G01D5/353 ,  G01H9/00

Abstract: It is intended to provide a phase measurement method and a signal processing device that are capable of reducing influence of noise of a measuring device without increasing the peak intensity of an incident light pulse when measuring the phase of scattered light in DAS-P.
A phase measurement method according to the present invention causes wavelength-multiplexed pulse 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.

公开(公告)号：US20210356357A1

公开(公告)日：2021-11-18

申请号：US17280971

申请日：2019-09-18

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Keiji OKAMOTO ,  Atsushi NAKAMURA ,  Hiroyuki OSHIDA

IPC: G01M11/00 ,  H01S3/091 ,  H01S3/30 ,  H04B10/071

Abstract: The present invention is to provide a backscattered light amplification device, an optical pulse test apparatus, a backscattered light amplification method, and an optical pulse test method for amplifying a desired propagation mode of Rayleigh backscattered light with a desired gain by stimulated Raman scattering in a fiber under test having the plurality of propagation modes. The backscattered light amplification device according to the present invention is configured to control individually power, incident timing, and pulse width of a pump pulse for each propagation mode when the pump pulse is incident in a plurality of propagation modes after the probe pulse is input to the fiber under test in any propagation mode.

公开(公告)号：US20220128395A1

公开(公告)日：2022-04-28

申请号：US17427792

申请日：2020-01-22

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yoshifumi WAKISAKA ,  Daisuke IIDA ,  Keiji OKAMOTO ,  Hiroyuki OSHIDA

IPC: G01H9/00

Abstract: The present invention aims to provide a vibration detection method, a signal processing device, and a program according to which it is possible to accurately detect vibration physically applied to an optical fiber, using a simple determination reference. In a vibration detection method according to the present invention, scattered light of a given target segment of a measurement target fiber is indicated by vectors of an in-phase component and a quadrature component, and a triangular shape constituted by a near-end-side vector of the target segment and a far-end-side vector is used as a physical amount to be tracked. That is, it is determined whether or not there is vibration based on a change in shape of the triangular shape with respect to a reference state. This is a detection method in which DAS-I and DAS-P are combined, a simple determination reference such as shape change of a triangular shape is employed, and overlooking of vibration detection can be reduced.

公开(公告)号：US20220120635A1

公开(公告)日：2022-04-21

申请号：US17426631

申请日：2019-09-04

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Atsushi NAKAMURA ,  Nazuki HONDA ,  Daisuke IIDA ,  Hiroyuki OSHIDA ,  Keiji OKAMOTO

IPC: G01M11/00 ,  G02B5/09

Abstract: An object of the present invention is to provide an optical pulse test apparatus and an optical pulse test method that are capable of determining a change in state of an optical fiber connection portion without the need for reference and without being affected by changes in gap interval before and after the change in state. The optical pulse test apparatus according to the present invention is configured to perform an OTDR measurement by using test optical pulses having spectral widths of from several nm to several hundred nm arranged at intervals of several ten nm to several hundred nm, calculate a reflection peak value caused by the Fresnel reflection at the connection portion from the obtained OTDR waveform, and determine a state such as water immersion of the optical fiber connection portion based on the value.

公开(公告)号：US20220065744A1

公开(公告)日：2022-03-03

申请号：US17413880

申请日：2019-12-03

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Atsushi NAKAMURA ,  Keiji OKAMOTO ,  Hiroyuki OSHIDA

IPC: G01M11/00

Abstract: An object is to provide an optical pulse test method and an optical pulse test device with which it is possible to measure transmission losses of a basic mode and a first higher-order mode at a connection point at which two-mode optical fibers are connected in series, without switching the mode of input test light.
An optical pulse test device according to the present invention inputs a test optical pulse in a basic mode (or a first higher-order mode) from one end of an optical fiber under test, the test optical pulse having such a wavelength that the test optical pulse can propagate in the basic mode and the first higher-order mode, measures intensity distributions of a basic mode component and a first higher-order mode component of return light of the test optical pulse relative to the distance from the one end, finds, from the intensity distributions, losses of the basic mode component and the first higher-order mode component of the return light at a desired connection point of the optical fiber under test, and calculates transmission losses of the basic mode and the first higher-order mode at the connection point based on expressions (8) (or expressions (9)).

公开(公告)号：US20220244137A1

公开(公告)日：2022-08-04

申请号：US17596368

申请日：2019-06-11

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Atsushi NAKAMURA ,  Keiji OKAMOTO ,  Hiroyuki OSHIDA

IPC: G01M11/00

Abstract: The purpose of this invention is to provide an optical pulse testing method and optical pulse testing device capable of measuring the loss at an end farther than an axially misaligned connection point at which inter-mode crosstalk occurs independently from the crosstalk value at the point. In this optical pulse testing method, a matrix (loss and crosstalk) representing the mode coupling at a near-end connection point is calculated, and an OTDR waveform having the effects of crosstalk eliminated therefrom is obtained by numerical processing using the calculated matrix representing the mode coupling.

公开(公告)号：US20220113220A1

公开(公告)日：2022-04-14

申请号：US17268113

申请日：2019-08-16

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Atsushi NAKAMURA ,  Keiji OKAMOTO ,  Tetsuya MANABE

IPC: G01M11/00

Abstract: An object of the present invention is to provide a Raman gain efficiency distribution testing method and a Raman gain efficiency distribution testing apparatus for measuring a Raman gain efficiency distribution of a fundamental mode and a first high-order mode in a few-mode fiber. The Raman gain efficiency distribution testing method and the Raman gain efficiency distribution testing apparatus according to the present invention compute a Raman gain coefficient of a tested optical fiber from a Raman gain coefficient of a pure quartz core optical fiber at an excitation wavelength of 1 μm, a wavelength of excitation light, and a relative refractive index difference between a core and a clad at an arbitrary position z, compute electric field distribution overlap integrals at an arbitrary position z, between modes, of a mode field diameter of each mode at a wavelength of signal light, and a mode field diameter of each mode at a wavelength of excitation light; and compute the product of the Raman gain coefficient and the electric field distribution overlap integrals, and acquire Raman gain efficiencies, between modes, of the signal light and the excitation light at the arbitrary position z.

公开(公告)号：US20210396626A1

公开(公告)日：2021-12-23

申请号：US17281186

申请日：2019-09-18

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Keiji OKAMOTO ,  Atsushi NAKAMURA ,  Hiroyuki OSHIDA

IPC: G01M11/02 ,  H01S3/30 ,  H04B10/071 ,  H04B10/2537

Abstract: The present invention is to provide a backscattered light amplification device, an optical pulse test apparatus, a backscattered light amplification method, and an optical pulse test method for amplifying a desired propagation mode of Rayleigh backscattered light with a desired gain by stimulated Brillouin scattering in a fiber under test having the plurality of propagation modes. The backscattered light amplification device according to the present invention is configured to control individually power, incident timing, and pulse width of a pump pulse for each propagation mode when the pump pulse is incident in a plurality of propagation modes after the probe pulse is input to the fiber under test in any propagation mode.

公开(公告)号：US20210356358A1

公开(公告)日：2021-11-18

申请号：US17286605

申请日：2019-06-06

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Atsushi NAKAMURA ,  Keiji OKAMOTO ,  Hiroyuki OSHIDA

IPC: G01M11/00

Abstract: An optical pulse test apparatus according to the present disclosure includes a light generation unit configured to generate an optical pulse for generating backscattered light beams in an optical fiber under test and generate first light having an optical frequency for amplifying backscattered light in an LP11 mode out of the backscattered light beams in two LP modes through stimulated Brillouin scattering, and second light having an optical frequency for attenuating backscattered light in an LP01 mode out of the backscattered light beams in the two LP modes through stimulated Brillouin scattering, a mode demultiplexing unit configured to input the optical pulse, the first light, and the second light generated by the light generation unit into the optical fiber under test in the LP01 mode and separate, out of the backscattered light beams generated by the optical pulse, the backscattered light in the LP11 mode, a local oscillation light generation unit configured to generate local oscillation light by which the backscattered light separated by the mode demultiplexing unit is heterodyne-detected, a light reception unit configured to multiplex the backscattered light in the LP11 mode separated by the mode demultiplexing unit and the local oscillation light generated by the local oscillation light generation unit and photoelectrically convert the multiplexed light into an electrical signal, and an arithmetic processing unit configured to calculate a time-intensity distribution of the electrical signal obtained by the light reception unit photoelectrically converting the backscattered light in the LP11 mode.

公开(公告)号：US20220364846A1

公开(公告)日：2022-11-17

申请号：US17636941

申请日：2019-09-03

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Daisuke IIDA ,  Keiji OKAMOTO ,  Hiroyuki OSHIDA

IPC: G01B11/16

Abstract: The present invention intends to provide an optical fiber cable sensing apparatus capable of measuring longitudinal directional distribution of curvature and torsion, without using a specially structured optical fiber sensor. This apparatus includes means for inputting data of longitudinal directional distribution of distortion (bending loss, polarization variation) measured for each optical fiber accommodated in an optical fiber cable to be measured and data indicating the position of each measurement object optical fiber on a cable cross section, means for calculating curvature vector κ of the optical fiber cable to be measured, at the same spot, based on the distortion (bending loss, polarization variation) of each optical fiber at the spot and the position of the optical fiber on the cable cross section, and means for calculating torsion τ of the optical fiber cable to be measured at the spot from the calculated curvature vector κ.