公开(公告)号：US20190013875A1

公开(公告)日：2019-01-10

申请号：US16066854

申请日：2017-01-10

Applicant: NEC CORPORATION

Inventor： Manabu ARIKAWA ,  Toshiharu ITO

IPC: H04B10/61

CPC classification number: H04B10/6165 ,  H04B10/1121 ,  H04B10/118 ,  H04L27/063 ,  H04L27/22

Abstract: In order to increase a compensation range for Doppler shift compensation, this digital signal processing circuit is provided with a Doppler shift compensation unit which, on the basis of a sample sequence signal which is oversampled at N (where N is an integer at least equal to 2) times a symbol rate and includes a central sample corresponding to the timing at a symbol center, and a transition sample corresponding to the timing of a symbol transition, finds a Doppler shift amount included in the sample sequence signal and performs Doppler shift compensation. The Doppler shift compensation unit includes a symbol determining unit which performs a symbol determination with respect to the central sample and a determination with respect to the transition sample. The Doppler shift compensation unit switches between these determinations for each corresponding sample and performs said determinations in order to obtain a phase difference and thereby detect the Doppler shift amount.

公开(公告)号：US20180234180A1

公开(公告)日：2018-08-16

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: H04B10/116 ,  H04B10/50 ,  H04B10/61

CPC classification number: H04B10/116 ,  H04B10/1121 ,  H04B10/118 ,  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：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：US20170070289A1

公开(公告)日：2017-03-09

申请号：US15123103

申请日：2014-03-13

Applicant: NEC Corporation

Inventor： Seigo TAKAHASHI ,  Toshiharu ITO ,  Kohei HOSOKAWA

IPC: H04B10/112 ,  H04B10/60

CPC classification number: H04B10/1121 ,  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.

Abstract translation: 相对于自由空间光通信接收机，不可能防止接收光和单模光纤之间的耦合效率的劣化，难以实现更高的传输速率; 因此，根据本发明的示例性方面的自由空间光学接收器包括：聚光装置，用于收集通过自由空间传播路径传播的激光; 模式控制装置，用于根据激光的波前波动将由光收集装置收集的激光分离成多个传播模式光束，并输出传播模式光束; 分别引导多个传播模式波束的多个单模传输介质; 以及多个光接收装置，用于分别通过多个单模传输介质接收多个传播模式光束。

公开(公告)号：US20220149940A1

公开(公告)日：2022-05-12

申请号：US17431504

申请日：2020-02-19

Applicant: NEC Corporation

Inventor： Manabu ARIKAWA ,  Toshiharu ITO

IPC: H04B10/11

Abstract: Tracking control of a light beam is achieved at high speed and with good precision, without requiring preparation of an optical system that causes high signal loss when coupling a reception light beam with an optical fiber. A reception device for optical space communication comprises: fibers having a plurality of propagation modes with spatially different characteristics; an optical coupling system for coupling the reception light beam to the fibers; and a mode separator that separates the coupled light into a plurality of propagation modes, the adjustment axes of the optical coupling system for coupling the reception light beam to one end of the fibers being controlled on the basis of the total coupling strength to all of the modes, and the priority of control of the axes being adjusted on the basis of information about the coupling strength ratio for each mode.

公开(公告)号：US20210083779A1

公开(公告)日：2021-03-18

申请号：US16498138

申请日：2018-03-22

Applicant: NEC CORPORATION

Inventor： Manabu ARIKAWA ,  Yasunori FUTATSUGI ,  Toshiharu ITO

IPC: H04B10/61 ,  H04B7/08

Abstract: A signal processing device combines a plurality of received signals, and includes: a phase reference signal selection means for selecting a signal serving as a phase reference from among the plurality of received signals on the basis of the quality of the plurality of received signals; a relative phase calculation means for obtaining information about the relative phases of the plurality of received signals before the combining; a phase compensation means for performing relative phase compensation on each of the plurality of received signals on the basis of the relative phases; and a phase correction means for calculating a phase correction amount based on the relative phase information and performing phase correction on the received signals, wherein when switching occurs in the selected phase reference signal, the phase correction amount is changed by as much as the relative phase difference between the phase reference signals before and after the switching.

公开(公告)号：US20190312639A1

公开(公告)日：2019-10-10

申请号：US16466702

申请日：2017-12-11

Applicant: NEC Corporation

Inventor： Yoshimasa ONO ,  Toshiharu ITO

IPC: H04B10/079 ,  H04B10/118

Abstract: An optical space communication device includes first and second optical antennas that transmit first and second transmission light and receive first and second reception light, first and second delay circuits that provide a delay to transmission data included in the first and second transmission light, third and fourth delay circuits that provide a delay to reception data included in the first and second reception light, and a receiver that sets a delay of at least one of the first delay circuit and the second delay circuit and sets a delay of at least one of the third delay circuit and the fourth delay circuit, based on delays between the first and third delay circuits and the first optical antenna, delays between the second and fourth delay circuits and a fourth optical antenna, and delays between a communication destination and the third and fourth delay circuits.

公开(公告)号：US20180323904A1

公开(公告)日：2018-11-08

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 ,  H04B10/61 ,  H04B10/118 ,  H04L27/00

CPC classification number: H04L1/0057 ,  H04B10/118 ,  H04B10/61 ,  H04L27/0014 ,  H04L27/22 ,  H04L2027/0057

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：US20180069625A1

公开(公告)日：2018-03-08

申请号：US15559150

申请日：2016-03-17

Applicant: NEC Corporation

Inventor： Manabu ARIKAWA ,  Emmanuel LE TAILLANDIER DE GABORY ,  Toshiharu ITO

IPC: H04B10/079 ,  H04B10/077 ,  H04B10/25

CPC classification number: H04B10/07951 ,  H04B10/077 ,  H04B10/25 ,  H04B10/2513 ,  H04B10/2581

Abstract: In the optical transmission system to transmit optical signals using a plurality of adjacent paths, it is difficult to detect a delay difference between a plurality of paths and chromatic dispersion with a high degree of accuracy due to a crosstalk; therefore, a method for detecting optical signal information according to an exemplary aspect of the present invention includes generating a plurality of data signal sequences corresponding to a plurality of paths multiplexed spatially, each of the plurality of data signal sequences obtained by inserting periodically a training signal with a plurality of frequency components in a data signal, in the plurality of data signal sequences, the training signals respectively included in the data signal sequences to be propagated through adjacent paths at least having different frequency components from each other at the same timing, each of a plurality of the training signals included in one of the data signal sequences having the plurality of frequency components whose frequency difference differing depending on a position to be inserted; and calculating a propagation delay difference between the plurality of paths and chromatic dispersion amounts in the plurality of paths from the plurality of frequency components included in the training signals having been propagated through the plurality of paths by optical signals.