公开(公告)号：US10454577B2

公开(公告)日：2019-10-22

申请号：US15751369

申请日：2016-08-17

Applicant: NEC CORPORATION

Inventor： Seigo Takahashi ,  Toshiharu Ito ,  Kohei Hosokawa ,  Manabu Arikawa ,  Yoshimasa Ono ,  Takashi Ishikawa

IPC: H04B10/118 ,  H04B10/112 ,  H04B10/116 ,  H04B10/50 ,  H04B10/61

Abstract: It is difficult in a free space optical transmitter to transmit a beacon beam stably at low cost, and that it is impossible to maintain stable tracking; therefore, a free space optical transmitter according to an exemplary aspect of the present invention includes a laser beam transmitting means for transmitting a plurality of laser beams capable of interfering with each other and differing in one of an optical frequency and a time variation in a phase difference; and a wavefront control beam transmitting means for transmitting, to a free space, a plurality of wavefront control beams obtained by making each of the plurality of laser beams have a different wavefront.

公开(公告)号：US10256904B2

公开(公告)日：2019-04-09

申请号：US15327862

申请日：2015-07-17

Applicant: NEC Corporation

Inventor： Seigo Takahashi ,  Toshiharu Ito ,  Kohei Hosokawa

IPC: H04B10/112 ,  H04B10/60

Abstract: The circuit size of a signal processing circuit increases in a free space optical receiver, which increases in cost, because the signal processing becomes complex attempting to improve the coupling efficiency between received light and a fiber; 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 multi-mode transmission medium for receiving input of the laser light and outputting multi-mode light; a multi-mode signal processing means for outputting a plurality of received electrical signals based on part of the multi-mode light; a monitor means for monitoring signal information based on the multi-mode light; a control means for controlling an operation of the multi-mode signal processing means based on the signal information; and a signal processing means for performing signal processing on the plurality of received electrical signals and outputting an output signal synthesized from the plurality of received electrical signals.

公开(公告)号：US10511409B2

公开(公告)日：2019-12-17

申请号：US15773035

申请日：2016-11-01

Applicant: NEC CORPORATION

Inventor： Kohei Hosokawa ,  Toshiharu Ito ,  Manabu Arikawa ,  Seigo Takahashi ,  Takashi Ishikawa ,  Yoshimasa Ono

IPC: H04L1/00 ,  H04L27/22 ,  H04B10/118 ,  H04B10/61 ,  H04L27/00

Abstract: An appropriate synthesized signal cannot be obtained by only correcting relative phase errors of a plurality of received signals; therefore, a received signal processor according to an exemplary aspect of the present invention includes a plurality of signal-to-noise ratio estimation means for estimating respective signal-to-noise ratios of a plurality of digital signal sequences in which relative phase errors of a plurality of received signal sequences having been corrected; a plurality of temporary decision means for performing symbol decisions of the plurality of digital signal sequences and outputting symbol signal sequences; symbol-map-rotation determination means for determining respective phase rotation amounts of the plurality of digital signal sequences from the plurality of symbol signal sequences and the respective signal-to-noise ratios of the plurality of digital signal sequences; and a plurality of phase rotation means for rotating phases of the plurality of digital signal sequences respectively based on the phase rotation amounts.

公开(公告)号：US10313011B2

公开(公告)日：2019-06-04

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 ,  H04B10/112 ,  H04B10/2581 ,  H04B10/548 ,  H04B10/67

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.

公开(公告)号：US10122447B2

公开(公告)日：2018-11-06

申请号：US15123103

申请日：2014-03-13

Applicant: NEC Corporation

Inventor： Seigo Takahashi ,  Toshiharu Ito ,  Kohei Hosokawa

IPC: H04B10/11 ,  H04B10/112 ,  H04B10/60 ,  H04J14/02

Abstract: It is impossible to prevent the deterioration of the coupling efficiency between received light and a single mode fiber, and difficult to achieve a higher transmission rate, with respect to a free space optical communication receiver; therefore, a free space optical receiver according to an exemplary aspect of the present invention includes light collecting means for collecting laser light having propagated through a free space transmission path; mode controlling means for separating the laser light collected by the light collecting means into a plurality of propagation mode beams depending on a wave-front fluctuation of the laser light and outputting the propagation mode beams; a plurality of single mode transmission media for guiding the plurality of propagation mode beams, respectively; and a plurality of light receiving means for receiving the plurality of propagation mode beams respectively through the plurality of single mode transmission media.

公开(公告)号：US10862593B2

公开(公告)日：2020-12-08

申请号：US16088328

申请日：2017-03-17

Applicant: NEC Corporation

Inventor： Kohei Hosokawa ,  Toshiharu Ito ,  Seigo Takahashi ,  Manabu Arikawa ,  Takashi Ishikawa ,  Yoshimasa Ono

IPC: H04B10/69 ,  H04J14/04 ,  H04B17/336 ,  H04B10/11

Abstract: The objective of the present invention is to reduce the size of a receiving device circuit in an optical space communication system while maintaining communication stability. A data receiving device which decodes one item of data from a plurality of input signals includes: two or more digital signal processing means for subjecting the plurality of input signals to signal processing; a first recording means for temporarily recording the plurality of input signals; a SN ratio estimating means for estimating S/N ratios of each of the plurality of input signals and determining the number of the plurality of input signals to be combined, and the signals to be combined; and a scheduling means for carrying out overall control on the basis of the results from the SN ratio estimating means.

公开(公告)号：US10411802B2

公开(公告)日：2019-09-10

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: H04B10/00 ,  H04B10/40 ,  H04B10/50 ,  H04B10/60 ,  H04B10/112 ,  H04B10/118

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.