公开(公告)号：US20190391073A1

公开(公告)日：2019-12-26

申请号：US16478508

申请日：2018-01-22

Applicant: NEC Corporation

Inventor： Akihiro TANAKA

IPC: G01N21/3504 ,  G01N21/27 ,  G01N21/31 ,  G01J3/26 ,  H04B10/116

Abstract: In order to distinguish between a deterioration in a received optical signal strength resulting from optical axis deviation, and a deterioration in the received optical signal strength due to the effects of dust and the like, this detecting system is provided with: a transmitter provided with a light emitting unit for transmitting a first optical signal and a second optical signal having mutually different wavelengths and divergence angles; and a receiver provided with a detecting unit for receiving the first and second optical signals and outputting a first reception signal indicating the reception strength of the first optical signal, and a second reception signal indicating the reception strength of the second optical signal, and an identification unit for determining a state of propagation of the first and second optical signals on the basis of an amount of variation in the first and second reception signals.

公开(公告)号：US20180212681A1

公开(公告)日：2018-07-26

申请号：US15745254

申请日：2016-07-15

Applicant: NEC CORPORATION

Inventor： Akihiro TANAKA ,  Toshiharu ITO ,  Kohei HOSOKAWA ,  Seigo TAKAHASHI ,  Manabu ARIKAWA

IPC: H04B10/118 ,  H04B10/00

CPC classification number: H04B10/118 ,  H04B10/112 ,  H04B10/12 ,  H04B10/40 ,  H04B10/50 ,  H04B10/60

Abstract: A receiving-side splitter 4 that constitutes part of an optical communication device 1 splits a receiving-side signal light into a plurality of lights at a splitting ratio according to the intensity distribution of mutually different propagation modes included in the receiving-side signal light passed through a transmission medium 3. A transmission-side splitter 10 splits a transmission-side signal light into a plurality of-lights. A signal processing device 5 detects the light intensity and/or the phase of the receiving-side signal light, and sets a control target value for the light intensity and/or the phase of the transmission-side signal light to a value according to the result of the detection. A modulator 9 adjusts the light intensity or the phase of a the transmission-side signal light so that the light intensity or phase equals the set value. A multiplexer 8 multiplexes the plurality of transmission-side signal lights.

公开(公告)号：US20220155138A1

公开(公告)日：2022-05-19

申请号：US17438997

申请日：2019-03-26

Applicant: NEC Corporation

Inventor： Akihiro TANAKA ,  Tomoyuki HINO ,  Chaitanya Prasad NARISETTY

IPC: G01H9/00 ,  B61L23/04 ,  E01C23/01

Abstract: Provided are a structure deterioration detection system and a structure deterioration detection method capable of detecting deterioration of a structure at low cost. In one example embodiment, a structure deterioration detection system includes an optical fiber cable that is placed along the longitudinal direction of a structure and continuously detects any vibration along the longitudinal direction of the structure, and a signal processing unit including a vibration measurement unit that measures the strength of a detected vibration, a per unit time integration unit that integrates the vibration strength for a specified period of time, an information storage unit that stores the integrated vibration strength, and a deterioration determination unit that makes a determination about whether deterioration of the structure has occurred by comparing the integrated vibration strengths at different times.

公开(公告)号：US20220057255A1

公开(公告)日：2022-02-24

申请号：US17417198

申请日：2019-03-05

Applicant: NEC Corporation

Inventor： Tomoyuki HINO ,  Akihiro TANAKA

IPC: G01H9/00 ,  H04B10/2537 ,  G01D5/353

Abstract: In optical fiber sensors, sensor signals obtained differ according to the circumstances of installation, in locations being observed, of optical fibers serving as sensors, and it is difficult to perform accurate measurements; therefore, a sensor signal processing apparatus according to the present invention includes variation calculation means for receiving a sensor signal based on scattered light of a light pulse propagating through an optical fiber, and calculating a variation of the sensor signal from a reference value; and normalization processing means for normalizing the variation within a predetermined time, and calculating a normalized variation.

公开(公告)号：US20170264365A1

公开(公告)日：2017-09-14

申请号：US15529145

申请日：2015-11-18

Applicant: NEC Corporation

Inventor： Seigo TAKAHASHI ,  Toshiharu ITO ,  Akihiro TANAKA ,  Kohei HOSOKAWA ,  Manabu ARIKAWA

IPC: H04B10/118 ,  H04B10/548 ,  H04B10/112 ,  H04B10/2581 ,  H04B10/67

CPC classification number: H04B10/118 ,  H04B10/112 ,  H04B10/2581 ,  H04B10/548 ,  H04B10/676

Abstract: It is difficult in a free space optical receiver to satisfy both of the stable receiving and the highly sensitive receiving; therefore, a free space optical receiver according to an exemplary aspect of the present invention includes a light collecting means for collecting laser light having propagated through a free space transmission path; a multimode light generating means for receiving input of the laser light collected by the light collecting means, exciting multimode light, and outputting multimode propagation light including a plurality of propagation mode light beams with a number smaller than a number of multimode light beams possible to be excited; and a mode separating means for separating the multimode propagation light into the plurality of propagation mode light beams and outputting the plurality of propagation mode light beams.