公开(公告)号：US20230400379A1

公开(公告)日：2023-12-14

申请号：US18034754

申请日：2020-11-02

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Tatsuya OKAMOTO ,  Daisuke IIDA ,  Yusuke KOSHIKIYA ,  Nazuki HONDA

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

CPC classification number: G01M11/02 ,  G01M11/3172 ,  H04B10/071

Abstract: The present disclosure relates to a frequency modulation amount measuring device that measures an optical spectral shift of scattered light at a position in an optical transmission line, and calculates a frequency modulation amount at the position, using the measured optical spectral shift.

公开(公告)号：US20250028078A1

公开(公告)日：2025-01-23

申请号：US18709686

申请日：2021-12-02

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Chihiro KITO ,  Yusuke KOSHIKIYA ,  Daisuke IIDA

IPC: G01W1/14

Abstract: Objects of the present invention are to provide a snow accumulation estimating system and a method for estimating a snow accumulation which enable a snow accumulation to be remotely measured accurately and economically.
A snow accumulation estimating system 301 according to the present invention includes: an optical fiber 50 that receives vibration from a random point on snow; a vibration measuring instrument 11 that measures the vibration received by the optical fiber 50 as a distribution in a longitudinal direction of the optical fiber 50; and an analysis processing unit 12 that has, as accumulated data, a relationship between a snow accumulation and the vibration received by the optical fiber 50, compares the distribution measured as measurement data by the vibration measuring instrument 11 with the accumulated data, and estimates a snow accumulation at the random point.

公开(公告)号：US20250003789A1

公开(公告)日：2025-01-02

申请号：US18693014

申请日：2021-09-29

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yoshifumi WAKISAKA ,  Daisuke IIDA ,  Yusuke KOSHIKIYA ,  Takahiro ISHIMARU

IPC: G01H9/00 ,  G01D5/353

Abstract: The present disclosure aims to reduce a strain of an observed waveform caused by a difference in proportional constant between responses of different optical frequencies of probe light resulting from vibration in a phase OTDR that uses different optical frequencies.
In order to achieve the above-described objective, the present disclosure relates to, in vibration measurement using a phase OTDR, including a compensation optical pulse with a predetermined compensation optical frequency different from an optical frequency in an optical pulse pair composed of optical pulses with different optical frequencies and making the optical pulse pair incident on a sensing fiber, calculating a phase value of the optical pulse pair based on a signal of the optical frequency from a scattered light signal based on the optical pulse pair and calculating a phase value of the compensation optical frequency based on a signal of the compensation optical frequency, plotting the phase values calculated from the scattered light signal on a two-dimensional, for each optical pulse pair plane, having the phase value of the compensation optical frequency represented by a horizontal axis and the phase value of the optical pulse pair represented by a vertical axis, obtaining a gradient and a vertical axis intercept of the approximate straight line calculated from the plotted data, and correcting the phase value of the optical pulse pair using the gradient and the vertical axis intercept.

公开(公告)号：US20240418601A1

公开(公告)日：2024-12-19

申请号：US18689785

申请日：2021-09-16

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Atsushi NAKAMURA ,  Tomokazu ODA ,  Yusuke KOSHIKIYA

IPC: G01M11/00

Abstract: In order to achieve the above object, the present invention individually inputs light pulses to a first core and a second core at one end of a non-coupled multicore fiber having a connection portion, and individually acquires OTDR waveforms regarding the first core and the second core, calculates ratios between backscattering intensity regarding the first core and backscattering intensity regarding the second core, at at least two points including one point on one end side with respect to the connection portion and one point on another end side with respect to the connection portion, based on the acquired OTDR waveforms, and calculates a ratio between the calculated ratio on the one end side and the calculated ratio on the another end side.

公开(公告)号：US20240377282A1

公开(公告)日：2024-11-14

申请号：US18689806

申请日：2021-09-29

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Tomokazu ODA ,  Atsushi NAKAMURA ,  Yusuke KOSHIKIYA

IPC: G01M11/00 ,  G01M11/02

Abstract: The present disclosure includes a light injecting unit that injects a frequency-swept probe light into one end of an optical fiber targeted for measurement, injects a pump light into the other end of the optical fiber targeted for measurement, with respect to the probe light, and thereby amplifies the probe light in the optical fiber targeted for measurement, a light receiving unit that receives a multiplexed light obtained by multiplexing a local light with the probe light, an interference waveform measurement unit that measures an interference waveform between the probe light and the local light, a fundamental mode time waveform analysis unit that acquires a fundamental mode time waveform of the probe light, based on the interference waveform, and a control calculation unit that calculates losses and crosstalk at loss and crosstalk occurrence points of the optical fiber targeted for measurement, based on the fundamental mode time waveform.

公开(公告)号：US20240377281A1

公开(公告)日：2024-11-14

申请号：US18692981

申请日：2021-10-08

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Tomokazu ODA ,  Atsushi NAKAMURA ,  Yusuke KOSHIKIYA

IPC: G01M11/02 ,  G01M11/00

Abstract: The present disclosure relates to a method for measuring inter-core crosstalk of an optical fiber having a plurality of cores, the method including: injecting light into one core of the optical fiber; converting light emitted from each of the cores provided in the optical fiber into parallel light with an angle difference; measuring an intensity distribution of an interference waveform of the parallel light; independently obtaining an interference component between the one core and any core, different from the one core, provided in the optical fiber and a DC component other than the interference component using the interference waveform of the parallel light; and obtaining crosstalk from the one core to any core, different from the one core, using the interference component and the DC component.

公开(公告)号：US20240271971A1

公开(公告)日：2024-08-15

申请号：US18682212

申请日：2021-08-16

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Tatsuya OKAMOTO ,  Daisuke IIDA ,  Yusuke KOSHIKIYA ,  Nazuki HONDA

IPC: G01D5/353

CPC classification number: G01D5/35361

Abstract: An object of the present invention is to provide a sensing system, a sensing method, and an analyzing device using OFDR in which a sensing range of strain/temperature is less likely to be limited by a frequency sweep width.
In the sensing method using OFDR, the sensing system according to the present invention employs sequential update, per measurement by one frequency sweep of the probe light, for setting the reference spectrum to the spectrum of an immediately preceding measurement, by which a spectral shift between an n-th measurement and an (n−1)th measurement is obtained, and the spectral shifts individually obtained between the measurements are integrated.

公开(公告)号：US20240183746A1

公开(公告)日：2024-06-06

申请号：US18285709

申请日：2021-04-14

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Atsushi NAKAMURA ,  Yusuke KOSHIKIYA ,  Nazuki HONDA

IPC: G01M11/00

CPC classification number: G01M11/332

Abstract: The present invention has an object to provide a mode field diameter measurement method enabling easily measuring a mode field diameter in an optical fiber, which is capable of propagating a fundamental mode (LP01 mode) and a first higher order mode (LP11 mode), without using a mode multiplexer, and a measurement device of the mode field diameter measurement method.
In a mode field diameter measurement method according to the present invention, an intensity ratio between an LP01 mode and an LP11 mode output from an optical fiber to be tested is changed, a mode field diameter is measured by a variable aperture (VA) method for each intensity ratio, and each mode field diameter is calculated.

公开(公告)号：US20240175726A1

公开(公告)日：2024-05-30

申请号：US18283498

申请日：2021-03-25

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Tatsuya OKAMOTO ,  Daisuke IIDA ,  Yusuke KOSHIKIYA ,  Nazuki HONDA

IPC: G01D5/353 ,  G01K11/32 ,  G01L1/24

CPC classification number: G01D5/35358 ,  G01K11/32 ,  G01L1/242

Abstract: The present disclosure generates an optical spectrogram, representing a temporal change in frequency characteristics, using a plurality of spectral data measured by an OFDR measurement instrument at different times, and filters the optical spectrogram in both a time direction and a frequency direction.

公开(公告)号：US20210262892A1

公开(公告)日：2021-08-26

申请号：US17252311

申请日：2019-06-12

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Hiroyuki IIDA ,  Tetsuya MANABE ,  Yusuke KOSHIKIYA ,  Hidenobu HIROTA ,  Takui UEMATSU

IPC: G01M11/00 ,  H04B10/071

Abstract: An object of the present disclosure is to provide a frequency division multiplexing coherent OTDR, a test method, a signal processing apparatus, and a program that can maintain, even in a case where a DFB laser is used, a spatial resolution equivalent to a spatial resolution achieved when a fiber laser or an external resonant laser is used. An OTDR according to the present disclosure includes a light incidence unit configured to change an optical frequency of light from a light source by a predetermined frequency interval at a predetermined time interval to generate test light pulses and cause the test light pulses to sequentially enter a fiber under test, a light reception unit configured to use the light from the light source as local light to coherently detect backscattered light from the fiber under test to acquire a received signal, and a computation unit configured to separate the received signal into signals with frequencies obtained by changing the optical frequency by the predetermined frequency interval, square amplitudes of the signals resulting from frequency separation to generate square values, perform Wiener filter processing on the square values, compensate values resulting from the Wiener filter processing for delay time when the test light pulses are caused to enter the fiber under test, and calculate an arithmetic mean of the compensated values.