Patents by Inventor Hisao Nakashima

Hisao Nakashima has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 11309968
    Abstract: Optical transmission device is provided in one of a plurality of nodes in an optical network. Different carrier frequencies are respectively allocated to the plurality of nodes. The optical transmission device includes: transmitter, splitter and receiver. The transmitter generates a first subcarrier optical signal with a first subcarrier established on a low-frequency side of a first carrier frequency and a second subcarrier optical signal with a second subcarrier established on a high-frequency side of the first carrier frequency. The splitter splits an optical signal including the first subcarrier optical signal and the second subcarrier optical signal. The output of the splitter is guided to first and second adjacent nodes. The receiver recovers data carried by the first subcarrier and data carried by the second subcarrier from received optical signal. A difference between carrier frequencies of adjacent nodes corresponds to a bandwidth of the subcarrier.
    Type: Grant
    Filed: April 15, 2021
    Date of Patent: April 19, 2022
    Assignee: FUJITSU LIMITED
    Inventors: Anh Ha Ngo, Takafumi Terahara, Naoki Ainaka, Hisao Nakashima
  • Patent number: 11303483
    Abstract: A transmission device includes an imparter configured to impart redundant data to the beginning of each of a plurality of data blocks divided from a data signal, a plurality of THP operators configured to parallelly precode the plurality of data blocks to which the redundant data is imparted, a transmitter configured to sequentially transmit the plurality of data blocks precoded by the plurality of THP operators and the redundant data imparted to each of the plurality of data blocks to a transmission line according to an arrangement order in the data signal, wherein the plurality of THP operators feed back a plurality of pieces of the redundant data to the plurality of data blocks, respectively.
    Type: Grant
    Filed: July 7, 2021
    Date of Patent: April 12, 2022
    Assignee: FUJITSU LIMITED
    Inventors: Guoxiu Huang, Hisao Nakashima
  • Publication number: 20220006530
    Abstract: Optical transmission device is provided in one of a plurality of nodes in an optical network. Different carrier frequencies are respectively allocated to the plurality of nodes. The optical transmission device includes: transmitter, splitter and receiver. The transmitter generates a first subcarrier optical signal with a first subcarrier established on a low-frequency side of a first carrier frequency and a second subcarrier optical signal with a second subcarrier established on a high-frequency side of the first carrier frequency. The splitter splits an optical signal including the first subcarrier optical signal and the second subcarrier optical signal. The output of the splitter is guided to first and second adjacent nodes. The receiver recovers data carried by the first subcarrier and data carried by the second subcarrier from received optical signal. A difference between carrier frequencies of adjacent nodes corresponds to a bandwidth of the subcarrier.
    Type: Application
    Filed: April 15, 2021
    Publication date: January 6, 2022
    Applicant: FUJITSU LIMITED
    Inventors: Anh Ha Ngo, Takafumi Terahara, Naoki AINAKA, Hisao Nakashima
  • Patent number: 11159352
    Abstract: An adaptive equalizer includes a sample buffer that temporarily stores data obtained by fractional sampling at a sampling rate that is larger than one time and smaller than two times a symbol rate; and a processor coupled to the sample buffer and configured to: specify position of a training sequence in the data based on a correlation value between a first set of (f×T) samples and a second set of (f×T) samples following the first set of samples, assuming that the sampling rate is f, and a symbol length of a code pattern included in the training sequence inserted in the data is T, and calculate an initial value of a tap coefficient set to a tap of an adaptive equalization filter based on the specified training sequence, wherein the symbol length is set to be changeable so that f×T is an integer.
    Type: Grant
    Filed: October 9, 2020
    Date of Patent: October 26, 2021
    Assignee: FUJITSU LIMITED
    Inventors: Daisuke Sasaki, Hisao Nakashima, Nobukazu Koizumi
  • Patent number: 11146428
    Abstract: An adaptive equalizer, includes a sample buffer; and a processor coupled to the sample buffer and configured to: perform an adaptive equalization on data which has been fractionally sampled at a sampling rate higher than once a symbol rate and lower than twice the symbol rate, determine an initial value of a tap coefficient of the adaptive equalizer by using a training sequence inserted in the data, shift, by a predetermined shift amount, a sample point of one pattern from among two consecutive patterns included in the training sequence, specify a position of the training sequence in the data by replacing an original sample value with a sample value at the shifted sample point, and update the initial value of the tap coefficient based on the specified training sequence.
    Type: Grant
    Filed: October 19, 2020
    Date of Patent: October 12, 2021
    Assignee: FUJITSU LIMITED
    Inventors: Daisuke Sasaki, Hisao Nakashima, Nobukazu Koizumi
  • Publication number: 20210297229
    Abstract: A transmission device includes a receiver configured to receive a frame signal including synchronization data, main signal data, and an error correction code, a compensator configured to compensate for distortion of the frame signal based on a compensation coefficient, a detector configured to detect synchronization timing of the frame signal from the synchronization data; a corrector configured to correct an error of the frame signal after the distortion is compensated, based on the error correction code according to the synchronization timing, a generator configured to generate a replica signal from the frame signal after the error is corrected by the corrector, based on the synchronization timing, the replica signal corresponding to the frame signal before the distortion is compensated, and an update processor configured to update the compensation coefficient based on the replica signal and the frame signal before the distortion is compensated.
    Type: Application
    Filed: February 17, 2021
    Publication date: September 23, 2021
    Applicant: FUJITSU LIMITED
    Inventors: Yoshitaka Nomura, Hisao Nakashima
  • Publication number: 20210223658
    Abstract: An optical modulator includes: a Mach-Zehnder modulator; and a processor that controls a bias of the Mach-Zehnder modulator. The Mach-Zehnder modulator includes first and second Mach-Zehnder interferometers that are respectively formed on first and second optical paths, a phase shifter that adjusts a phase difference between the first optical path and the second optical path. The processor outputs a first bias signal for controlling an operation point of the first Mach-Zehnder interferometer, a second bias signal for controlling an operation point of the second Mach-Zehnder interferometer, and a third bias signal for controlling a phase-shift amount of the phase shifter, a low-frequency signal being superimposed on the third bias signal. The processor controls the first through third bias signals based on a frequency component of the low-frequency signal that is included in the optical signal output from the Mach-Zehnder modulator.
    Type: Application
    Filed: December 10, 2020
    Publication date: July 22, 2021
    Applicant: FUJITSU LIMITED
    Inventors: GUOXIU HUANG, Hisao Nakashima
  • Publication number: 20210160108
    Abstract: An adaptive equalizer includes a sample buffer that temporarily stores data obtained by fractional sampling at a sampling rate that is larger than one time and smaller than two times a symbol rate; and a processor coupled to the sample buffer and configured to: specify position of a training sequence in the data based on a correlation value between a first set of (f×T) samples and a second set of (f×T) samples following the first set of samples, assuming that the sampling rate is f, and a symbol length of a code pattern included in the training sequence inserted in the data is T, and calculate an initial value of a tap coefficient set to a tap of an adaptive equalization filter based on the specified training sequence, wherein the symbol length is set to be changeable so that f×T is an integer.
    Type: Application
    Filed: October 9, 2020
    Publication date: May 27, 2021
    Applicant: FUJITSU LIMITED
    Inventors: Daisuke SASAKI, Hisao Nakashima, Nobukazu KOIZUMI
  • Publication number: 20210152403
    Abstract: An adaptive equalizer, includes a sample buffer; and a processor coupled to the sample buffer and configured to: perform an adaptive equalization on data which has been fractionally sampled at a sampling rate higher than once a symbol rate and lower than twice the symbol rate, determine an initial value of a tap coefficient of the adaptive equalizer by using a training sequence inserted in the data, shift, by a predetermined shift amount, a sample point of one pattern from among two consecutive patterns included in the training sequence, specify a position of the training sequence in the data by replacing an original sample value with a sample value at the shifted sample point, and update the initial value of the tap coefficient based on the specified training sequence.
    Type: Application
    Filed: October 19, 2020
    Publication date: May 20, 2021
    Applicant: FUJITSU LIMITED
    Inventors: Daisuke SASAKI, Hisao Nakashima, Nobukazu KOIZUMI
  • Patent number: 10873410
    Abstract: There is provided a reception device including a receiver configured to receive a wavelength-multiplexed optical signal so as to generate a wavelength-multiplexed signal, a filter configured to pass through the wavelength-multiplexed signal having a specific wavelength and an adjacent wavelength to the specific wavelength from the wavelength-multiplexed signal, and a processor configured to detect a specific signal having the specific wavelength from the wavelength-multiplexed signal having the passed through wavelengths by the filter, and detect a first supervisory control signal having the specific wavelength and a second supervisory control signal having the adjacent wavelength from the wavelength-multiplexed signal having the passed through wavelengths by the filter.
    Type: Grant
    Filed: February 20, 2018
    Date of Patent: December 22, 2020
    Assignee: FUJITSU LIMITED
    Inventors: Yi Ge, Takeshi Hoshida, Hisao Nakashima, Tomofumi Oyama, Yuichi Akiyama
  • Patent number: 10862592
    Abstract: An optical receiver includes, a first converting circuit that converts an optical signal into an electric signal, a plurality of common circuits, each of which has a same circuit configuration and performs a digital signal processing on the electric signal, and a processor that selects and operates one or more common circuits from among the plurality of common circuits according to a transmission method.
    Type: Grant
    Filed: July 31, 2018
    Date of Patent: December 8, 2020
    Assignee: FUJITSU LIMITED
    Inventors: Hisao Nakashima, Takeshi Hoshida
  • Publication number: 20200313771
    Abstract: An optical transceiver includes: a receiver and a processor. The receiver receives a polarization multiplexed optical signal that includes a first polarization signal and a second polarization signal so as to output reception electric-field information that indicates an electric field of the polarization multiplexed optical signal. The processor calculates, according to the reception electric-field information, a variation monitor value that indicates an amount of leakage of signal components between the first polarization signal and the second polarization signal. When the variation monitor value exceeds a specified threshold, the processor analyzes, according to the reception electric-field information, a state of an optical transmission line through which the polarization multiplexed optical signal propagates.
    Type: Application
    Filed: March 30, 2020
    Publication date: October 1, 2020
    Applicant: FUJITSU LIMITED
    Inventor: Hisao Nakashima
  • Patent number: 10708035
    Abstract: A signal processing device includes: a filter configured to perform an adaptive equalization process of a signal, on a basis of a filter coefficient; an updater configured to update the filter coefficient, on a basis of amplitude of the signal and a target value of the amplitude; and a corrector configured to correct the target value, on a basis of the amplitude of the signal.
    Type: Grant
    Filed: December 20, 2018
    Date of Patent: July 7, 2020
    Assignee: FUJITSU LIMITED
    Inventors: Tomofumi Oyama, Hisao Nakashima
  • Patent number: 10698228
    Abstract: A transmission method includes mapping a data signal to a symbol according to a modulation mode to generate a first electric field signal and a second electric field signal, modulating a light beam based on the first electric field signal and the second electric field signal to generate a first polarized light beam and a second polarized light beam that are orthogonal to each other, multiplexing the first polarized light beam and the second polarized light beam, applying transformation processing of changing each polarization angle of the first polarized light beam and the second polarized light beam to the first electric field signal and the second electric field signal and adding polarization information indicating a change amount caused by the transformation processing for each polarization angle of the first polarized light beam and the second polarized light beam to the first electric field signal and the second electric field signal.
    Type: Grant
    Filed: April 18, 2019
    Date of Patent: June 30, 2020
    Assignee: FUJITSU LIMITED
    Inventors: Tomofumi Oyama, Hisao Nakashima
  • Patent number: 10567077
    Abstract: Provided is an imbalance compensation device that compensates for an imbalance between an in-phase component and a quadrature-phase component of a signal, the imbalance compensation device including: an extracting unit that extracts a signal component in an upper sideband or a signal component in a lower sideband from the signal; a measuring unit that measures power of the signal component in the upper sideband or the signal component in the lower sideband extracted by the extracting unit; and an adjusting unit that adjusts a parameter related to the imbalance, in accordance with the power measured by the measuring unit.
    Type: Grant
    Filed: March 6, 2018
    Date of Patent: February 18, 2020
    Assignee: FUJITSU LIMITED
    Inventors: Tomofumi Oyama, Takeshi Hoshida, Yoshitaka Nomura, Hisao Nakashima
  • Patent number: 10498459
    Abstract: There is provided an optical transmitter including a modulator, a signal generator configured to generate in-phase or anti-phase skew adjustment signals that are identical in amplitude and frequency as signals to be input into an I axis and a Q axis of the modulator, a skew adjuster configured to perform skew adjustment upon the skew adjustment signals, a light source configured to enter light into the modulator, a monitor configured to monitor light that has been modulated using the skew adjustment signals and output from the modulator, a power detector configured to detect power of monitor light, and a controller configured to determine a skew adjustment amount with which average power of the monitor light is at a maximum or minimum value as an optimum skew adjustment value while changing a skew adjustment amount of the skew adjuster.
    Type: Grant
    Filed: June 12, 2018
    Date of Patent: December 3, 2019
    Assignee: FUJITSU LIMITED
    Inventors: Yoshitaka Nomura, Tomofumi Oyama, Hisao Nakashima, Yuichi Akiyama, Takeshi Hoshida
  • Publication number: 20190331931
    Abstract: A transmission method includes mapping a data signal to a symbol according to a modulation mode to generate a first electric field signal and a second electric field signal, modulating a light beam based on the first electric field signal and the second electric field signal to generate a first polarized light beam and a second polarized light beam that are orthogonal to each other, multiplexing the first polarized light beam and the second polarized light beam, applying transformation processing of changing each polarization angle of the first polarized light beam and the second polarized light beam to the first electric field signal and the second electric field signal and adding polarization information indicating a change amount caused by the transformation processing for each polarization angle of the first polarized light beam and the second polarized light beam to the first electric field signal and the second electric field signal.
    Type: Application
    Filed: April 18, 2019
    Publication date: October 31, 2019
    Applicant: FUJITSU LIMITED
    Inventors: Tomofumi Oyama, Hisao Nakashima
  • Patent number: 10439732
    Abstract: A receiving device receives a received signal in which a data signal, modulated by using a phase modulation method, and a pilot signal are time-multiplexed. The receiving device includes a synchronizing circuit that synchronizes the phase of the received signal. The synchronizing circuit extracts a pilot signal from the received signal. The synchronizing circuit estimates a phase error by comparing the extracted pilot signal and a predetermined pattern. The synchronizing circuit conducts phase rotation on constellation points of the received signal in accordance with the reference phase, obtained from the phase error, and the phase in the modulation method related to the received signal. The synchronizing circuit estimates a phase estimate value of the received signal in accordance with the constellation points, on which phase rotation has been conducted. The synchronizing circuit compensates for a phase error of the received signal in accordance with the phase estimate value.
    Type: Grant
    Filed: August 24, 2017
    Date of Patent: October 8, 2019
    Assignee: FUJITSU LIMITED
    Inventors: Tomofumi Oyama, Takeshi Hoshida, Hisao Nakashima
  • Patent number: 10419263
    Abstract: A transmission system includes a first transponder including a first I/Q modulator, and a second transponder including a second I/Q modulator, and configured to communicate with the first transponder using a frequency modulation scheme, wherein the first transponder is configured to set a first phase rotation mode in a first state for first light signal output from the first I/Q modulator, and transmit, to the second transponder, a first command to specify a second phase rotation mode for second light signal output from the second I/Q modulator, and the second transponder is configured to set, in response to the first command, the second phase rotation mode in a state specified by the first command.
    Type: Grant
    Filed: July 6, 2018
    Date of Patent: September 17, 2019
    Assignee: FUJITSU LIMITED
    Inventors: Yi Ge, Takeshi Hoshida, Hisao Nakashima, Yuichi Akiyama
  • Patent number: 10396900
    Abstract: A method of controlling a transmission signal, includes transmitting a training signal including four polarization states having a given relation; and performing rotation control and transmission power level control of a polarization component of a data signal, based on a rotation control matrix for a polarization state and an inverse-operation control matrix for a power level imbalance, which are estimated from Stokes parameters related to input power level present on a Poincare sphere acquired from the training signal and Stokes parameters related to output power level present on the Poincare sphere.
    Type: Grant
    Filed: March 16, 2018
    Date of Patent: August 27, 2019
    Assignee: FUJITSU LIMITED
    Inventors: Guoxiu Huang, Setsuo Yoshida, Takeshi Hoshida, Hisao Nakashima, Shoichiro Oda