Patents by Inventor Yoshiaki Kisaka

Yoshiaki Kisaka 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).

  • Publication number: 20210218476
    Abstract: A digital coherent receiver includes: an adaptive equalizer configured to execute, using a first tap coefficient, adaptive equalization processing on a digital signal that corresponds to a signal; a first coefficient updating unit configured to update the first tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a first step size; a second coefficient updating unit configured to update a second tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a second step size; and a control unit configured to detect a fluctuation speed of a state of polarization of the digital signal based on the second tap coefficient, and change the first tap coefficient to the updated second tap coefficient if it is determined that the fluctu
    Type: Application
    Filed: August 27, 2019
    Publication date: July 15, 2021
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Akira MASUDA, Seiji OKAMOTO, Shuto YAMAMOTO, Fukutaro HAMAOKA, Masanori NAKAMURA, Asuka MATSUSHITA, Yoshiaki KISAKA
  • Publication number: 20210211218
    Abstract: An optical transmission system includes an optical transmitter, an optical receiver, and a control apparatus. The control apparatus repeatedly performs an adjustment process for adjusting power of an optical signal of a frequency band to be adjusted while switching the frequency band to be adjusted between at least two frequency bands including at least a frequency band where stimulated Raman scattering occurs among frequency bands that are multiplexed in a multiplexed optical signal transmitted by the optical transmission system. In the adjustment process, when power of an optical signal of the frequency band to be adjusted transmitted from the optical transmitter has been changed, the control apparatus determines the power of the optical signal of the frequency band to be adjusted on the basis of a signal quality measured by the optical receiver that has received the optical signal.
    Type: Application
    Filed: May 20, 2019
    Publication date: July 8, 2021
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Fukutaro HAMAOKA, Kyo MINOGUCHI, Seiji OKAMOTO, Yoshiaki KISAKA
  • Publication number: 20210203363
    Abstract: A signal processing device includes a distributing unit and a plurality of correcting units with different processing performance, the distributing unit distributes a bit sequence having a first number of bits to the first correcting unit, and a bit sequence having a second number of bits less than the first number of bits to the second correcting unit having lower processing performance than the first correcting unit, the first correcting unit applies error correction processing to the bit sequence having the first number of bits distributed to the first correcting unit, and the second correcting unit applies error correction processing to the bit sequence having the second number of bits distributed to the second correcting unit.
    Type: Application
    Filed: May 9, 2019
    Publication date: July 1, 2021
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Seiji OKAMOTO, Etsushi YAMAZAKI, Masanori NAKAMURA, Yoshiaki KISAKA, Masahito TOMIZAWA
  • Publication number: 20210167939
    Abstract: A frame synchronization apparatus (10) according to this invention includes a multiplication unit (11) configured to multiply a received signal by an inverse complex number of a predetermined synchronization pattern with respect to a predetermined signal point on a complex space diagram for each of a plurality of symbols of the received signal, an addition average unit (12) configured to perform addition averaging of outputs from the multiplication unit for the plurality of symbols of the received signal, and a synchronization determination unit (13) configured to perform coincidence determination of whether an output from the addition average unit (12) falls within a predetermined coincidence determination range of the predetermined signal point, and determine a synchronization state of the frame synchronization based on a result of the coincidence determination.
    Type: Application
    Filed: February 12, 2021
    Publication date: June 3, 2021
    Inventors: Mitsuteru YOSHIDA, Yasuyuki ENDOH, Katsuichi OYAMA, Masayuki IKEDA, Tsutomu TAKEYA, Etsushi YAMAZAKI, Yoshiaki KISAKA, Masahito TOMIZAWA
  • Publication number: 20210075541
    Abstract: An error correction device according to this invention includes a first correction unit configured to perform error correction decoding of data by a repetitive operation, and having a full operation state in which the repetitive operation of the error correction decoding is repeated until convergence is obtained and a save operation state in which the number of times of the repetitive operation of the error correction decoding is restricted to a predetermined number of times, an error information estimation unit configured to estimate an input error rate or an output error rate of the first correction unit using a decoding result of the first correction unit, and a control unit configured to control transition between the full operation state and the save operation state of the first correction unit based on at least one piece of information of the input error rate, the output error rate, and an operation time of the first correction unit.
    Type: Application
    Filed: December 20, 2018
    Publication date: March 11, 2021
    Inventors: Fumiaki NAKAGAWA, Yasuharu ONUMA, Katsuichi OYAMA, Yasuyuki ENDOH, Etsushi YAMAZAKI, Yoshiaki KISAKA, Masahito TOMIZAWA
  • Patent number: 10868617
    Abstract: A band division timing adjustment unit aligns timings of a plurality of signals, which are generated by dividing a received signal according to a plurality of frequency bands, in a time domain and combines the plurality of signals for which the timings have been aligned. A chromatic dispersion compensation unit compensates chromatic dispersion of an output signal of the band division timing adjustment unit for each of the plurality of frequency bands.
    Type: Grant
    Filed: October 6, 2017
    Date of Patent: December 15, 2020
    Assignees: NTT Electronics Corporation, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Mitsuteru Yoshida, Etsushi Yamazaki, Yoshiaki Kisaka, Masahito Tomizawa
  • Patent number: 10841006
    Abstract: A signal-to-noise ratio (SNR) estimation method includes an optical signal transmission step of inserting at least one pair of signal sequences into transmission data and transmitting the transmission data into which the at least one pair of signal sequences is inserted, a signal sequence extraction step of extracting the at least one pair of signal sequences from a received signal obtained by receiving the transmitted transmission data, an inner product calculation step of calculating an inner product value of the extracted at least one pair of signal sequences, a reception power calculation step of calculating reception power of the extracted at least one pair of signal sequences, and an SNR calculation step of calculating an SNR of the at least one pair of signal sequences on the basis of the calculated inner product value and the calculated reception power.
    Type: Grant
    Filed: March 26, 2018
    Date of Patent: November 17, 2020
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Seiji Okamoto, Yoshiaki Kisaka, Kengo Horikoshi, Mitsuteru Yoshida, Masahiro Suzuki
  • Patent number: 10826620
    Abstract: An optical receiver that demodulates an optical modulation signal into a baseband signal, which is an electrical signal, and decodes a received symbol acquired by converting the baseband signal. The optical receiver includes: an analog-to-digital converter that converts the baseband signal into a digital signal of which the number of samples per received symbol is M/N (samples/symbol), M and N being positive integers, M/N being not an integer, and “M>N” being satisfied; and an adaptive equalization processing unit that executes an equalization operation set in advance to output the received symbol on the basis of the digital signal of which the number of samples per received symbol is M/N (samples/symbol) and a predetermined tap coefficient digital signal equalization tap coefficients used for equalization of a signal, the coefficient being updated in any sampling period.
    Type: Grant
    Filed: October 25, 2017
    Date of Patent: November 3, 2020
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Fukutaro Hamaoka, Seiji Okamoto, Masanori Nakamura, Kengo Horikoshi, Yoshiaki Kisaka
  • Patent number: 10651944
    Abstract: An optical transmitter of an optical data transmission system transmitting data through an optical fiber transmission path includes a main signal generator that converts first transmission data into a predetermined signal format to generate a first signal, a DCSK modulator that DCSK-modulates second transmission data to generate a second signal, a signal-multiplexer that performs time-division multiplexing of the first signal and the second signal, and an electro-optical converter that converts a multiplexed signal obtained by the time-division multiplexing of the signal-multiplexer from an electric signal into an optical signal, and outputs the optical signal to the optical fiber transmission path.
    Type: Grant
    Filed: July 26, 2017
    Date of Patent: May 12, 2020
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Kengo Horikoshi, Seiji Okamoto, Asuka Matsushita, Mitsuteru Yoshida, Fukutaro Hamaoka, Yoshiaki Yamada, Yoshiaki Kisaka
  • Patent number: 10608743
    Abstract: A reception circuit includes a first adaptive compensator compensating distortion of a received signal. An adaptive compensation coefficient calculator includes a known-signal detector detecting first and second known-signals from the received signal, a second adaptive compensator compensating distortion of the received signal, a tap coefficient initial value calculator calculating an initial value of a tap coefficient of the second adaptive compensator by comparing the first known-signal with its true value, a first phase shift compensator compensating phase shift of an output of the second adaptive compensator using the second known-signal, and a tap coefficient calculator calculating tap coefficients of the first and second adaptive compensators by comparing at least one of the first and second known-signals compensated by the second adaptive compensator and the first phase shift compensator with its true value.
    Type: Grant
    Filed: May 26, 2017
    Date of Patent: March 31, 2020
    Assignees: NTT ELECTRONICS CORPORATION, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Tomohiro Takamuku, Etsushi Yamazaki, Katsuichi Oyama, Yasuharu Onuma, Kazuhito Takei, Masanori Nakamura, Mitsuteru Yoshida, Masahito Tomizawa, Yoshiaki Kisaka
  • Publication number: 20200067598
    Abstract: A band division timing adjustment unit (10) aligns timings of a plurality of signals, which are generated by dividing a received signal according to a plurality of frequency bands, in a time domain and combines the plurality of signals for which the timings have been aligned. A chromatic dispersion compensation unit (17) compensates chromatic dispersion of an output signal of the band division timing adjustment unit (10) for each of the plurality of frequency bands.
    Type: Application
    Filed: October 6, 2017
    Publication date: February 27, 2020
    Applicants: NTT Electronics Corporation, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Mitsuteru YOSHIDA, Etsushi YAMAZAKI, Yoshiaki KISAKA, Masahito TOMIZAWA
  • Publication number: 20200052793
    Abstract: An optical receiver that demodulates an optical modulation signal into a baseband signal, which is an electrical signal, and decodes a received symbol acquired by converting the baseband signal. The optical receiver includes: an analog-to-digital converter that converts the baseband signal into a digital signal of which the number of samples per received symbol is M/N (samples/symbol), M and N being positive integers, M/N being not an integer, and “M >N” being satisfied; and an adaptive equalization processing unit that executes an equalization operation set in advance to output the received symbol on the basis of the digital signal of which the number of samples per received symbol is M/N (samples/symbol) and a predetermined tap coefficient digital signal equalization tap coefficients used for equalization of a signal, the coefficient being updated in any sampling period.
    Type: Application
    Filed: October 25, 2017
    Publication date: February 13, 2020
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Fukutaro HAMAOKA, Seiji OKAMOTO, Masanori NAKAMURA, Kengo HORIKOSHI, Yoshiaki KISAKA
  • Publication number: 20200028586
    Abstract: A signal-to-noise ratio (SNR) estimation method includes an optical signal transmission step of inserting at least one pair of signal sequences into transmission data and transmitting the transmission data into which the at least one pair of signal sequences is inserted, a signal sequence extraction step of extracting the at least one pair of signal sequences from a received signal obtained by receiving the transmitted transmission data, an inner product calculation step of calculating an inner product value of the extracted at least one pair of signal sequences, a reception power calculation step of calculating reception power of the extracted at least one pair of signal sequences, and an SNR calculation step of calculating an SNR of the at least one pair of signal sequences on the basis of the calculated inner product value and the calculated reception power.
    Type: Application
    Filed: March 26, 2018
    Publication date: January 23, 2020
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Seiji OKAMOTO, Yoshiaki KISAKA, Kengo HORIKOSHI, Mitsuteru YOSHIDA, Masahiro SUZUKI
  • Patent number: 10422719
    Abstract: A Fourier-transformer performs Fourier transform on a filter coefficient output from an adaptive equalizer which comprises a finite impulse response filter of N taps (N represents an integer of 2 or more) in a time direction. An eigenvalue sum calculator integrates a frequency-differentiation result of the Fourier-transformed filter coefficient and a complex conjugate of the Fourier-transformed filter coefficient to calculate a matrix, and calculates a sum of two eigenvalues of the matrix. A proportionality factor calculator calculates a proportionality factor for frequency from the sum of the two eigenvalues.
    Type: Grant
    Filed: October 4, 2016
    Date of Patent: September 24, 2019
    Assignees: NTT ELECTRONICS CORPORATION, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Etsushi Yamazaki, Tomohiro Takamuku, Yuki Yoshida, Mitsuteru Yoshida, Koki Shibahara, Kengo Horikoshi, Yoshiaki Kisaka
  • Patent number: 10419127
    Abstract: A symbol phase difference compensating portion (6) calculates a first phase difference which is a phase difference between a known pattern extracted from a received signal and a true value of the known pattern and performs phase compensation for the received signal based on the first phase difference. A tentative determination portion (12) tentatively determines an output signal of the symbol phase difference compensating portion (6) to acquire an estimated value of a phase. A first phase difference acquiring portion (13) acquires a second phase difference which is a phase difference between a phase of the output signal and the estimated value of the phase acquired by the tentative determination portion (12). A first phase difference compensating portion (14) performs phase compensation for the output signal based on the second phase difference.
    Type: Grant
    Filed: April 13, 2017
    Date of Patent: September 17, 2019
    Assignees: NTT ELECTRONICS CORPORATION, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Etsushi Yamazaki, Hiroyukl Nouchi, Yasuharu Onuma, Tomohiro Takamuku, Katsuichi Oyama, Kazuhito Takei, Masahito Tomizawa, Yoshiaki Kisaka, Mltsuteru Yoshida, Masanori Nakamura
  • Publication number: 20190273560
    Abstract: An optical transmitter of an optical data transmission system transmitting data through an optical fiber transmission path includes a main signal generator that converts first transmission data into a predetermined signal format to generate a first signal, a DCSK modulator that DCSK-modulates second transmission data to generate a second signal, a signal-multiplexer that performs time-division multiplexing of the first signal and the second signal, and an electro-optical converter that converts a multiplexed signal obtained by the time-division multiplexing of the signal-multiplexer from an electric signal into an optical signal, and outputs the optical signal to the optical fiber transmission path.
    Type: Application
    Filed: July 26, 2017
    Publication date: September 5, 2019
    Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Kengo HORIKOSHI, Seiji OKAMOTO, Asuka MATSUSHITA, Mitsuteru YOSHIDA, Fukutaro HAMAOKA, Yoshiaki YAMADA, Yoshiaki KISAKA
  • Patent number: 10305675
    Abstract: An FIR filter convolutes sampled data obtained by sampling a reception signal with tap coefficients. A phase difference detector detects a phase difference between a synchronization timing of a signal waveform estimated from an output signal of the FIR filter and a sampling timing of the output signal. A tap coefficient adjuster adjusts the tap coefficients so as to reduce the phase difference detected by the phase difference detector and causes the sampling timing of the output signal of the FIR filter to track the synchronization timing.
    Type: Grant
    Filed: January 16, 2017
    Date of Patent: May 28, 2019
    Assignees: NTT ELECTRONICS CORPORATION, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Yasuharu Onuma, Masahiro Tachibana, Etsushi Yamazaki, Kazuhito Takei, Yuki Yoshida, Masayuki Ikeda, Yoshiaki Kisaka, Masahito Tomizawa
  • Publication number: 20190074903
    Abstract: A reception circuit includes a first adaptive compensator compensating distortion of a received signal. An adaptive compensation coefficient calculator includes a known-signal detector detecting first and second known-signals from the received signal, a second adaptive compensator compensating distortion of the received signal, a tap coefficient initial value calculator calculating an initial value of a tap coefficient of the second adaptive compensator by comparing the first known-signal with its true value, a first phase shift compensator compensating phase shift of an output of the second adaptive compensator using the second known-signal, and a tap coefficient calculator calculating tap coefficients of the first and second adaptive compensators by comparing at least one of the first and second known-signals compensated by the second adaptive compensator and the first phase shift compensator with its true value.
    Type: Application
    Filed: May 26, 2017
    Publication date: March 7, 2019
    Inventors: Tomohiro TAKAMUKU, Etsushi YAMAZAKI, Katsuichi OYAMA, Yasuharu ONUMA, Kazuhito TAKEI, Masanori NAKAMURA, Mitsuteru YOSHIDA, Masahito TOMIZAWA, Yoshiaki KISAKA
  • Publication number: 20190074909
    Abstract: A symbol phase difference compensating portion (6) calculates a first phase difference which is a phase difference between a known pattern extracted from a received signal and a true value of the known pattern and performs phase compensation for the received signal based on the first phase difference. A tentative determination portion (12) tentatively determines an output signal of the symbol phase difference compensating portion (6) to acquire an estimated value of a phase. A first phase difference acquiring portion (13) acquires a second phase difference which is a phase difference between a phase of the output signal and the estimated value of the phase acquired by the tentative determination portion (12). A first phase difference compensating portion (14) performs phase compensation for the output signal based on the second phase difference.
    Type: Application
    Filed: April 13, 2017
    Publication date: March 7, 2019
    Inventors: Etsushi YAMAZAKI, Hiroyukl NOUCHI, Yasuharu ONUMA, Tomohiro TAKAMUKU, Katsuichi OYAMA, Kazuhito TAKEI, Masahito TOMIZAWA, Yoshiaki KISAKA, Mltsuteru YOSHIDA, Masanori NAKAMURA
  • Patent number: 10171173
    Abstract: An optical signal transmission apparatus includes a modulation unit which modulates a transmission signal, a training signal sequence generation unit which generates a plurality of signal sequences having power concentrated in a plurality of different frequency bands, at least one of an amplitude and a phase of the plurality of signal sequences being modulated, as a training signal sequence, a signal multiplexing unit which appends the training signal sequence to the transmission signal, and an electro-optical conversion unit which converts a signal sequence obtained by appending the training signal sequence to the transmission signal into an optical signal and transmits the optical signal.
    Type: Grant
    Filed: March 17, 2015
    Date of Patent: January 1, 2019
    Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
    Inventors: Seiji Okamoto, Koichi Ishihara, Etsushi Yamazaki, Mitsuteru Yoshida, Tomoyoshi Kataoka, Kazushige Yonenaga, Yoshiaki Kisaka, Masanori Nakamura, Masahito Tomizawa