公开(公告)号：US11519817B2

公开(公告)日：2022-12-06

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：US11976962B2

公开(公告)日：2024-05-07

申请号：US15734211

申请日：2019-05-29

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yoshifumi Wakisaka ,  Daisuke Iida ,  Kunihiro Toge ,  Tetsuya Manabe

IPC: G01B17/04 ,  G01D5/353 ,  G01H9/00

CPC classification number: G01H9/004 ,  G01B17/04 ,  G01D5/35358

Abstract: An object is to provide an optical fiber path search method, an optical fiber path search system, a signal processor, and a program that can be operated free of the effects of walls, supporting members, and the like so that only a signal generated by an acoustic wave propagating through the air can be extracted. An optical fiber path search system according to the present invention utilizes DAS and includes: a vibration source 304 configured to provide an acoustic wave to a predetermined region; a light reflection measurement device 305 configured to be connected to one end of an optical fiber 302 and configured to measure vibration of a change in an optical path length from the other end of the optical fiber 302 to a point in the optical fiber 302 due to the acoustic wave provided by the vibration source 304; and a signal processor 313 configured to extract a signal component in a high frequency region higher than a preset cutoff frequency from a signal of the vibration of the change in the optical path length measured by the light reflection measurement device 305 and calculate a distance between the vibration source 304 and the point in the optical fiber 302 using the signal component.

公开(公告)号：US11300731B2

公开(公告)日：2022-04-12

申请号：US17254954

申请日：2019-06-26

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takui Uematsu ,  Hidenobu Hirota ,  Hiroyuki Iida ,  Tetsuya Manabe

IPC: G02B6/28

Abstract: An object is to provide a highly versatile optical fiber local-light detection apparatus capable of supporting various types of coated optical fibers. An optical fiber local-light detection apparatus according to the present invention includes: a first jig 11 including a recess portion 22 curved along a longitudinal direction with respect to a coated optical fiber 100 and a light input/output unit 14 configured to emit light to the coated optical fiber 100 that is bent and to receive light leaking from the coated optical fiber 100; a second jig 12 including at least one protrusion portion 23 that is curved along the longitudinal direction with respect to the coated optical fiber 100, the second jig configured to clamp the coated optical fiber 100 with the recess portion 22 of the first jig 11, in accordance with a type of the coated optical fiber 100; a pressing portion configured to apply pressing force in a direction in which the recess portion 22 of the first jig 11 and the at least one protrusion portion 23 of the second jig 12 mutually approach, to bend the coated optical fiber 100; and a switching mechanism configured to switch the at least one protrusion portion 23 to a protrusion portion corresponding to the type of the coated optical fiber 100.

公开(公告)号：US11280668B2

公开(公告)日：2022-03-22

申请号：US17256532

申请日：2019-06-19

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Kunihiro Toge ,  Daisuke Iida ,  Shingo Ono ,  Yoshifumi Wakisaka ,  Tetsuya Manabe

IPC: G01H9/00 ,  G02B6/35

Abstract: A distributed optical fiber vibration measurement device includes a phase constant difference computation unit causing the first backscattered light generated at the points of a plurality of optical fibers under test that are integrated to interfere with another light to obtain two AC components and determining a phase constant difference from the two AC components, a phase distribution data creation unit comparing amplitudes between the two AC components obtained by causing the first backscattered light generated at the points of the optical fibers under test to interfere with the other light and selecting, for each of the points, phase data regarding one of the two AC components having a larger amplitude to create phase distribution data with the phase data, and a vibration measurement unit identifying an optical path length difference between any two points of the optical fiber under test to measure vibration of the optical fiber under test.

公开(公告)号：US20210381925A1

公开(公告)日：2021-12-09

申请号：US17266038

申请日：2019-08-01

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroshi Takahashi ,  Kunihiro Toge ,  Tomokazu Oda ,  Tetsuya Manabe

IPC: G01M11/00

Abstract: An optical test system capable of accurately measuring a loss of each mode at each position of an optical fiber which propagates a plurality of modes is provided. An optical fiber loss measuring apparatus for measuring using an OTDR technique includes a crosstalk suppressing light input unit that inputs light of a different mode different from the predetermined mode, the different mode causing crosstalk to the probe light, to the target optical fiber to be measured through the near end as crosstalk suppressing light at a second frequency obtained by giving a frequency that is equivalent to a Brillouin frequency shift of the predetermined mode to a first frequency, a light separating unit that removes light of the second frequency from light that is output from the target optical fiber to be measured through the near end to separate light of the first frequency, and a propagation mode loss measuring unit that measures an intensity of the separated light to measure a loss of each propagation mode at each position of the target optical fiber to be measured.

公开(公告)号：US11644347B2

公开(公告)日：2023-05-09

申请号：US17275327

申请日：2019-09-12

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Tatsuya Okamoto ,  Daisuke Iida ,  Hiroyuki Oshida ,  Tetsuya Manabe

IPC: G01D5/353 ,  E02D29/14 ,  G01H9/00

CPC classification number: G01D5/35306 ,  E02D29/14 ,  G01D5/35358 ,  G01H9/004

Abstract: A manhole position identification method of the present invention includes: measuring, from an end of an optical fiber, a temporal variation in scattering light from the optical fiber when an impact blow is applied to a cover of a manhole located on a path of the optical fiber, so as to obtain temporal variations in a scattering light intensity distribution in a longitudinal direction of the optical fiber; determining an occurrence of vibration due to the impact blow based on the temporal variations at positions in the scattering light intensity distribution, so as to identify an impact blow position on the optical fiber; and associating the impact blow position on the optical fiber with a map position of the manhole whose cover has received the impact blow, so as to identify a position of the manhole expressed in terms of optical fiber length from the end.

公开(公告)号：US11575981B2

公开(公告)日：2023-02-07

申请号：US17271390

申请日：2019-08-23

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Takui Uematsu ,  Tetsuya Manabe ,  Hidenobu Hirota ,  Hiroyuki Iida

IPC: H04B10/079 ,  H04Q11/00 ,  H04L12/46

Abstract: The present disclosure intends to provide an optical signal from an ONU according to a desired service usage state without using the ONU and an OLT. A simulated signal light generation apparatus 10 according to the present disclosure is a simulated signal light generation apparatus 10 for simulating an uplink signal light generated in an optical network unit (ONU) in a passive optical network (PON), and the apparatus includes a usage state control unit 11 that sets a service usage state of the ONU, a signal generation unit 12 that generates an uplink signal frame according to the usage state set by the usage state control unit 11, and an electrical/optical conversion unit 13 that converts an electrical signal from the signal generation unit 12 into an optical signal, and the optical signal from the electrical/optical conversion unit 13 is repeatedly transmitted to an optical fiber core 22.

公开(公告)号：US11378489B2

公开(公告)日：2022-07-05

申请号：US16975821

申请日：2019-02-26

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroshi Takahashi ,  Tomokazu Oda ,  Kunihiro Toge ,  Tetsuya Manabe

IPC: G01M11/02 ,  G01M11/00 ,  H04B10/2581

Abstract: An object is to provide a propagation property analyzing apparatus that can alleviate the influence of an error caused by crosstalk, and accurately evaluate a few-mode optical fiber that multiplexes a plurality of modes, in a distributional and non-destructive manner. Provided is a propagation property analyzing apparatus that analyzes propagation properties of a few-mode optical fiber that multiplexes a plurality of modes, which is an optical fiber under test, in a lengthwise direction thereof, through Brillouin time domain analysis, the propagation property analyzing apparatus including: means for inputting probe light in a desired mode from a distal end of the optical fiber under test; means for inputting a light pulse that is in the desired mode and that has a frequency difference equivalent to a Brillouin frequency shift in the desired mode, relative to the probe light, from a proximal end of the optical fiber under test, as pump light corresponding to the probe light; and means for inputting a light pulse that is in another mode different from the desired mode and that has a frequency difference equivalent to a Brillouin frequency shift in the other mode, relative to the probe light, as secondary probe light corresponding to the probe light, from the proximal end of the optical fiber under test.

公开(公告)号：US20210310897A1

公开(公告)日：2021-10-07

申请号：US17269151

申请日：2019-08-14

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Tomokazu Oda ,  Hiroshi Takahashi ,  Kunihiro Toge ,  Tetsuya Manabe

IPC: G01M11/00 ,  G01M11/02

Abstract: An optical fiber loss measurement device includes a unit configured to input pump light at a first frequency in a predetermined mode to a measurement target optical fiber in which a plurality of modes propagate from a first end, and input probe light at a second frequency to which a Brillouin frequency shift is applied to a second end, a Brillouin gain acquisition unit configured to measure an intensity of light output from the first end to acquire Brillouin gains in a longitudinal direction of the measurement target optical fiber using a BOTDA method, and a unit configured to measure a loss in the predetermined mode of the measurement target optical fiber, and the probe light is in a mode in which an electric field distribution in a cross section of the measurement target optical fiber is axisymmetric.

公开(公告)号：US11112332B2

公开(公告)日：2021-09-07

申请号：US16977882

申请日：2019-03-05

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yusuke Koshikiya ,  Atsushi Nakamura ,  Kazutaka Noto ,  Tetsuya Manabe

IPC: G01M11/00 ,  H04B10/071 ,  G01D5/353

Abstract: An object of the present disclosure is to provide an optical fiber cable monitoring method and an optical fiber cable monitoring system capable of linking information obtained from a measurement result with information stored in a DB and accurately specifying a loss occurrence location on an optical fiber cable. The optical fiber cable monitoring method according to the present disclosure uses two types of optical fiber measurement techniques having different sensitivities. Each of closure locations on the optical fiber cable is acquired with a high-sensitivity measurement technique, and geographical location information and the closure locations on the optical fiber are linked in an arrangement order of the closures. Thus, an operator can recognize an actual location (geographical location information) of a closure that is linked to a location of a point of abnormality on the optical fiber cable when an abnormality in the closure is detected with a low-sensitivity measurement technique.