公开(公告)号：US20220006521A1

公开(公告)日：2022-01-06

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: H04B10/071

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.

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：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：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：US20230288287A1

公开(公告)日：2023-09-14

申请号：US18020958

申请日：2020-08-21

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Atsushi NAKAMURA ,  Daisuke IIDA ,  Tomokazu ODA ,  Hiroyuki OSHIDA

IPC: G01M11/00

CPC classification number: G01M11/31

Abstract: An object of the present disclosure is to provide a power coupling coefficient measurement method and a power coupling coefficient measurement device capable of inexpensively and easily measuring a power coupling coefficient. The power coupling coefficient measurement method according to the present disclosure is a power coupling coefficient measurement method for measuring a power coupling coefficient of a multi-core fiber in order to achieve the aforementioned object, and includes: inputting a test light pulse from one end of the multi-core fiber to any one of cores; receiving backscattered light of the core to which the test light pulse is input or any one of the other cores; measuring an intensity distribution of the backscattered light with respect to a distance from the one end of the multi-core fiber; and calculating the power coupling coefficient from the intensity distribution of the backscattered light.

公开(公告)号：US20230175884A1

公开(公告)日：2023-06-08

申请号：US17766494

申请日：2019-10-17

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Yoshifumi WAKISAKA ,  Daisuke IIDA ,  Hiroyuki OSHIDA

IPC: G01H9/00

CPC classification number: G01H9/004

Abstract: An object of the present invention is to propose a design method of a minimum value N of the number of multiplexed frequencies that is necessary for measuring an object vibrational frequency according to DAS-P while taking into consideration a trade-off between a measurement distance and an upper limit of a measurable vibrational frequency. When a phase change of an arbitrary section of a measured optical fiber is represented by A×sin (2πfvt), N=4Zfv/ν is satisfied when A is smaller than π/2 but N=2Zfv/(ν·Arcsin (π/2A)) is satisfied when A is equal to or larger than π/2, where fv represents vibrational frequency, t represents time, Z represents a length of the measured optical fiber (a measurement distance), and ν represents the speed of light inside the measured optical fiber.

公开(公告)号：US20220260454A1

公开(公告)日：2022-08-18

申请号：US17622977

申请日：2019-07-11

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Tomokazu ODA ,  Yoshifumi WAKISAKA ,  Daisuke IIDA ,  Hiroyuki OSHIDA

IPC: G01M11/02 ,  G01M11/00 ,  H04B10/073

Abstract: An object is to provide a light intensity distribution measurement method and a light intensity distribution measurement apparatus that are capable of accurately measuring the intensity of light in each mode at each position of an optical fiber through which light is propagated in a plurality of modes. With a light intensity distribution measurement apparatus according to the present invention, a gain coefficient matrix is acquired in advance, which is constituted by Brillouin gain coefficients of propagation modes with predetermined optical frequency differences measured using a reference optical fiber that exhibits the same properties as a measurement-target optical fiber and that does not cause mode coupling, and the intensity distribution of light in each propagation mode in a lengthwise direction of the measurement-target optical fiber is calculated based on the gain coefficient matrix and a difference in light intensity before and after Brillouin amplification of the probe light emitted in a predetermined propagation mode at a predetermined optical frequency difference measured using the measurement-target optical fiber.

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：US20220103252A1

公开(公告)日：2022-03-31

申请号：US17427651

申请日：2020-01-17

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Daisuke IIDA ,  Nazuki HONDA ,  Tatsuya OKAMOTO ,  Yoshifumi WAKISAKA ,  Hiroyuki OSHIDA

IPC: H04B10/071 ,  H04B10/27 ,  H04B10/2507

Abstract: An object is to provide an optical fiber route search method, an optical fiber route search device, and a program that can efficiently confirm a path of an optical fiber that is installed over a long distance or across a large range. The optical fiber route search method according to the present invention carries out optical measurement that performs distributed measurement of the state of an optical fiber while applying a disturbance to the optical fiber in a portion in which wires of the optical fiber are parallel to each other, branch out, or intersect with each other (a proximity portion), and determines that the position in which the number of singularities (peaks or intensity fluctuations) fluctuates (becomes plural) is the position of the proximity portion from a distribution diagram obtained through the optical measurement.