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    Optical pulse reflectometer and optical pulse reflectometry
    21.
    发明授权
    Optical pulse reflectometer and optical pulse reflectometry 有权

    公开(公告)号：US11467060B2

    公开(公告)日：2022-10-11

    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.

    Permittivity measuring device and thickness measuring device
    22.
    发明授权
    Permittivity measuring device and thickness measuring device 有权

    公开(公告)号：US12117285B2

    公开(公告)日：2024-10-15

    申请号：US17918950

    申请日：2020-04-22

    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

    Inventor： Masaki Nakamori ,  Yukihiro Goto ,  Hiroyuki Oshida

    IPC: G01B11/06 ,  G01N21/3563 ,  G01N21/3581

    CPC classification number: G01B11/06 ,  G01N21/3563 ,  G01N21/3581

    Abstract: An object permittivity measurement apparatus according to the present disclosure includes: a light wave distance measurement device configured to measure reciprocating time t of a light wave with which an object is irradiated and that is reflected and returned from the object, and calculate a distance L to the object using the following equation (1),

    L=ct/2  (1)



    c: light speed;
    an electromagnetic wave phase measurement device configured to measure a rotated phase φ of an electromagnetic wave having a frequency f with which the object is irradiated and that is reflected and returned from the object; and
    a permittivity calculation circuit configured to calculate permittivity ε of a foreign material on an object surface using the following equation (2),

    φ=4πLf/c+4π(ε)1/2df/c  (2)

    d: a thickness of the foreign material on the object surface.

    Fiber optic test methods, fiber optic test equipment, and programs
    23.
    发明授权
    Fiber optic test methods, fiber optic test equipment, and programs 有权

    公开(公告)号：US12007298B2

    公开(公告)日：2024-06-11

    申请号：US17636093

    申请日：2019-08-23

    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

    Inventor： Nazuki Honda ,  Kazutaka Noto ,  Hiroyuki Oshida

    IPC: G01M11/00 ,  G01M11/02 ,  H04B10/071

    CPC classification number: G01M11/3145 ,  G01M11/0242 ,  G01M11/3163 ,  H04B10/071

    Abstract: An object of the present invention is to provide an optical fiber test method, an optical fiber test apparatus, and a program, capable of detecting a boundary of an optical fiber line facility regardless of a change in a noise amount. A change amount (a differential value) of an OTDR waveform increases toward a distal end due to noise effects, making it difficult to determine a boundary of the optical fiber using the change amount. Therefore, in the present invention, a dispersion of the OTDR waveform, which increases toward a distal end due to noise effects, is also used to determine the boundary of the optical fiber. In other words, in the present invention, the noise amount is expressed by the dispersion, and the dispersion is compared with the change amount such as a differential value as a threshold, to determine the boundary of the optical fiber. For this reason, when noise increases, the threshold increases together with an increase in the change amount, and therefore, the boundary of the optical fiber can be determined regardless of noise.

    Phase measurement method and signal processing device
    24.
    发明授权
    Phase measurement method and signal processing device 有权

    公开(公告)号：US11867555B2

    公开(公告)日：2024-01-09

    申请号：US17440514

    申请日：2020-03-19

    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

    Inventor： Yoshifumi Wakisaka ,  Daisuke Iida ,  Kunihiro Toge ,  Hiroyuki Oshida

    IPC: G01H9/00 ,  G01D5/353

    CPC classification number: G01H9/004 ,  G01D5/35383

    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.

    Vibration detection method with improved signal processing
    25.
    发明授权
    Vibration detection method with improved signal processing 有权

    公开(公告)号：US11860028B2

    公开(公告)日：2024-01-02

    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

    CPC classification number: G01H9/004

    Abstract: A vibration detection method is presented to accurately detect vibration physically applied to an optical fiber, using a simple determination reference. In a vibration detection method, 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.

    Phase measurement method, signal processing device, and program
    29.
    发明授权
    Phase measurement method, signal processing device, and program 有权

    公开(公告)号：US11522606B2

    公开(公告)日：2022-12-06

    申请号：US17285719

    申请日：2019-11-14

    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

    Inventor： Yoshifumi Wakisaka ,  Daisuke Iida ,  Keiji Okamoto ,  Hiroyuki Oshida

    IPC: H04B10/07 ,  H04B10/071

    Abstract: It is an object to enable offline measurement with a high SN ratio of the phase of scattered light of an optical fiber to be measured in an optical receiving system for real-time measurement (direct measurement). The phase measurement method according to the present invention performs coherent detection of scattered light using a 90-degree optical hybrid, obtains an estimated quadrature component value by averaging a measured quadrature component value that is directly measured and a calculated quadrature component value obtained by Hilbert transforming a measured in-phase component value that is directly measured, obtains an estimated in-phase component value by averaging the measured in-phase component value and a calculated in-phase component value obtained by inverse Hilbert transforming the measured quadrature component value, and calculates the phase of scattered light based on the estimated quadrature component value and the estimated in-phase component value.

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