Patents by Inventor Kosuke Komaki
Kosuke Komaki 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).
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Patent number: 8655185Abstract: An optical node disposed along a transmission line that uses optical fiber. The optical node includes a first signal generator and a monitor. The first signal generator generates a first measurement signal for measuring polarization mode dispersion values and transmits the first measurement signal along the transmission line. The monitor detects a second measurement signal from the transmission line and measures polarization mode dispersion values by performing signal processing with respect to the second measurement signal.Type: GrantFiled: January 11, 2011Date of Patent: February 18, 2014Assignee: Fujitsu LimitedInventors: Takeshi Sakamoto, Katsumi Fukumitsu, Kosuke Komaki
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Patent number: 8630552Abstract: A digital coherent receiver includes a front end, an A/D convertor, and a processor. The front end converts a light signal into an electric signal by using a signal light and a local oscillator light. The A/D convertor converts the electric signal of the front end into a digital signal. The processor calculates a spectrum gravity center of the digital signal converted by the A/D convertor, estimates a frequency offset of the digital signal based on the calculated spectrum gravity center, and reduces the frequency offset of the digital signal based on the estimated frequency offset.Type: GrantFiled: April 11, 2011Date of Patent: January 14, 2014Assignee: Fujitsu LimitedInventors: Hisao Nakashima, Takeshi Hoshida, Kosuke Komaki
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Publication number: 20130259478Abstract: There is provided an optical transmitter including: a demultiplexer configured to divide a data frame of a transmission signal into subframes with a predetermined length so as to form the subframes in a plurality of signal lanes; an index generator configured to generate an index for indicating an order of the signal lanes; a lane rearrangement unit configured to rearrange the order of the signal lanes according to the index; a carrier controller configured to generate a frequency offset of a carrier corresponding to the index; a mapping unit configured to map the transmission signal in the plurality of signal lanes with the rearranged order to the transmission signal with a phase corresponding to the frequency offset; and a transmitting unit configured to optically modulate the mapped transmission signal so as to transmit the modulated transmission signal.Type: ApplicationFiled: February 28, 2013Publication date: October 3, 2013Applicant: FUJITSU LIMITEDInventor: Kosuke Komaki
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Patent number: 8478137Abstract: An optical receiver includes: a waveform distortion compensator to perform an operation on digital signal representing an optical signal generated by an A/D converter to compensate for waveform distortion of the optical signal; a phase detector to generate phase information representing sampling phase of the A/D converter; a phase adjuster to generate digital signal representing an optical signal in which the sampling phase of the A/D converter is adjusted from an output signal of the waveform distortion compensator using the phase information; a demodulator to generate a demodulated signal from the output signal of the phase adjuster; a phase controller to control the sampling phase of the A/D converter; a peak detector to detect a peak value of the phase information while the sampling phase of the A/D converter is controlled by the phase controller; and a compensation controller to control the waveform distortion compensator using the peak value.Type: GrantFiled: January 31, 2011Date of Patent: July 2, 2013Assignee: Fujitsu LimitedInventors: Kosuke Komaki, Masahiro Shioda, Katsumi Fukumitsu, Osamu Takeuchi
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Patent number: 8358939Abstract: An optical communication device using a digital coherent reception system includes a phase detector configured to generate, based on a signal obtained in a course of digital signal processing, a phase signal indicating a displacement of a sampling of a reception signal, a clock switch-determiner configured to switch from an reference clock to a clock of transferred data when a value of an amplitude of the phase signal exceeds a given threshold value, and a selector configured to synchronize the sampling of the reception signal and an internal clock of the digital signal processing with the reference clock at start time or signal loss time, and synchronize the sampling of the reception signal and the internal clock with the line clock of the reception signal except for the start time and the signal loss time.Type: GrantFiled: July 28, 2010Date of Patent: January 22, 2013Assignee: Fujitsu LimitedInventor: Kosuke Komaki
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Publication number: 20120308227Abstract: A digital coherent receiver includes a sampling phase detector to detect a phase of a sampled digital signal, and a phase adjustor to adjust the sampling phase of the digital signal based upon the detected phase. The phase detector includes filters to equalize the digital signal with different equalization characteristics; sensitivity monitoring phase detectors, each connected to one of the filters and outputting a phase detection signal representing the phase of the output signal from the associated filter together with a sensitivity monitoring signal representing the sensitivity of the phase detection; sensitivity correction coefficient generators, each generating a sensitivity correction coefficient for correcting the associated phase detection signal using a square sum of the sensitivity monitoring signals; and an adder to add the phase detection signals that have been corrected by the sensitivity correction coefficients, and output a phase signal.Type: ApplicationFiled: April 13, 2012Publication date: December 6, 2012Applicant: FUJITSU LIMITEDInventors: Kosuke KOMAKI, Hisao Nakashima
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Publication number: 20120148266Abstract: A digital coherent optical receiver includes a processor that is operative to separate electric signals obtained by converting an optical signal into a horizontal signal component and a vertical signal component; to generate a histogram of the horizontal signal component and the vertical signal component as outputs of the equalizing filter; and to determine a presence/absence of local convergence based on distribution of the histogram of the horizontal signal component and the histogram of the vertical signal component.Type: ApplicationFiled: October 27, 2011Publication date: June 14, 2012Applicant: FUJITSU LIMITEDInventors: Kosuke Komaki, Osamu Takeuchi
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Publication number: 20120134684Abstract: An adaptive equalizer includes a finite impulse response filter with a predetermined number of taps; and a tap coefficient adaptive controller having a register to hold tap coefficients for the filter, a weighted center calculator to calculate a weighted center of the tap coefficients, and a tap coefficient shifter to shift the tap coefficients based on a calculation result of the weighted center. During an initial training period, the tap coefficient shifter shifts the tap coefficients on a symbol data basis such that a difference between the calculated weighted center of the tap coefficients and a tap center defined by the number of taps is minimized.Type: ApplicationFiled: October 14, 2011Publication date: May 31, 2012Applicant: FUJITSU LIMITEDInventors: Nobukazu Koizumi, Kazuhiko Hatae, Noriyasu Nakayama, Koji Nakamuta, Hisao Nakashima, Kosuke Komaki
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Publication number: 20120087669Abstract: In an optical node, a transmitter produces an optical supervisory signal for supervising an optical network, a processor is operative to control a power level of the optical supervisory signal according to a per-wavelength power level of an optical communication signal when the optical node has no post amplifiers, and a multiplexer combines the controlled optical supervisory signal with the optical communication signal to be transmitted to another optical node located downstream.Type: ApplicationFiled: October 4, 2011Publication date: April 12, 2012Applicant: FUJITSU LIMITEDInventors: Koji BIWA, Kosuke KOMAKI
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Publication number: 20120051754Abstract: An optical receiver includes: an optical to electric converter that converts a received optical signal into an analog electric signal; an analog to digital converter that converts the analog electric signal obtained by the optical to electric converter into a digital signal; a digital signal processor that performs wave shaping on the digital signal; an information extract circuit that extracts information related to loss or deterioration of the optical signal from a signal propagating from the analog to digital converter to the digital signal processor or a signal in the digital signal processor; and a judging circuit that judges, based on the information extracted by the information extract circuit, whether the optical signal is lost or deteriorates.Type: ApplicationFiled: July 7, 2011Publication date: March 1, 2012Applicant: Fujitsu LimitedInventors: Takeshi SAKAMOTO, Kosuke Komaki
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Publication number: 20110255877Abstract: A digital coherent receiver includes a front end, an A/D convertor, and a processor. The front end converts a light signal into an electric signal by using a signal light and a local oscillator light. The A/D convertor converts the electric signal of the front end into a digital signal. The processor calculates a spectrum gravity center of the digital signal converted by the A/D convertor, estimates a frequency offset of the digital signal based on the calculated spectrum gravity center, and reduces the frequency offset of the digital signal based on the estimated frequency offset.Type: ApplicationFiled: April 11, 2011Publication date: October 20, 2011Applicant: FUJITSU LIMITEDInventors: Hisao NAKASHIMA, Takeshi HOSHIDA, Kosuke KOMAKI
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Publication number: 20110229127Abstract: A digital coherent receiver converts signals and local light respectively detected, as detection results, in signal light from an optical transmission line, into digital signals and that further applies digital processing to the digital signals. The receiver includes a skew detecting unit that detects skew between the digital signals; a skew control unit controls the skew of each of the signals so that the skew to be detected by the skew detecting unit will be reduced; and a demodulating unit that demodulates each signal controlled for skew by the skew control unit.Type: ApplicationFiled: February 24, 2011Publication date: September 22, 2011Applicant: FUJITSU LIMITEDInventors: Yuichirou SAKAMOTO, Kosuke Komaki
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Publication number: 20110229128Abstract: An optical node disposed along a transmission line that uses optical fiber. The optical node includes a first signal generator and a monitor. The first signal generator generates a first measurement signal for measuring polarization mode dispersion values and transmits the first measurement signal along the transmission line. The monitor detects a second measurement signal from the transmission line and measures polarization mode dispersion values by performing signal processing with respect to the second measurement signal.Type: ApplicationFiled: January 11, 2011Publication date: September 22, 2011Applicant: FUJITSU LIMITEDInventors: Takeshi SAKAMOTO, Katsumi FUKUMITSU, Kosuke KOMAKI
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Publication number: 20110200339Abstract: An optical receiver includes: a waveform distortion compensator to perform an operation on digital signal representing an optical signal generated by an A/D converter to compensate for waveform distortion of the optical signal; a phase detector to generate phase information representing sampling phase of the A/D converter; a phase adjuster to generate digital signal representing an optical signal in which the sampling phase of the A/D converter is adjusted from an output signal of the waveform distortion compensator using the phase information; a demodulator to generate a demodulated signal from the output signal of the phase adjuster; a phase controller to control the sampling phase of the A/D converter; a peak detector to detect a peak value of the phase information while the sampling phase of the A/D converter is controlled by the phase controller; and a compensation controller to control the waveform distortion compensator using the peak value.Type: ApplicationFiled: January 31, 2011Publication date: August 18, 2011Applicant: FUJITSU LIMITEDInventors: Kosuke KOMAKI, Masahiro Shioda, Katsumi Fukumitsu, Osamu Takeuchi
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Patent number: 7899331Abstract: According to a WDM optical transmission system of the present invention, wavelength numbers information of a WDM signal light output from an upstream side optical amplifying unit to a transmission path fiber, and signal output level information thereof are transmitted to a downstream side optical amplifying unit utilizing a supervisory control light. In the downstream side optical amplifying unit, a loss (span loss) in the transmission path fiber is computed using the upstream side signal output level information and downstream side signal input level information, so that a gain to be set for a downstream side optical amplifier is calculated based on the computed loss, and also, the gain is corrected based on a difference between a target value of the signal output level computed using the wavelength numbers information and an actual measurement value thereof, so that the optical amplifier is controlled in accordance with the post-corrected gain.Type: GrantFiled: July 30, 2007Date of Patent: March 1, 2011Assignee: Fujitsu LimitedInventors: Hiroyuki Itoh, Kosuke Komaki
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Publication number: 20110026940Abstract: An optical communication device using a digital coherent reception system includes a phase detector configured to generate, based on a signal obtained in a course of digital signal processing, a phase signal indicating a displacement of a sampling of a reception signal, a clock switch-determiner configured to switch from an reference clock to a clock of transferred data when a value of an amplitude of the phase signal exceeds a given threshold value, and a selector configured to synchronize the sampling of the reception signal and an internal clock of the digital signal processing with the reference clock at start time or signal loss time, and synchronize the sampling of the reception signal and the internal clock with the line clock of the reception signal except for the start time and the signal loss time.Type: ApplicationFiled: July 28, 2010Publication date: February 3, 2011Applicant: FUJITSU LIMITEDInventor: Kosuke KOMAKI
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Patent number: 7880960Abstract: An optical amplifier includes a first optical amplification unit that amplifies input light, a variable optical attenuation unit that attenuates an output of the first optical amplification unit, a second optical amplification unit that amplifies an output of the variable optical attenuation unit, and a loss amount control unit that controls the variable optical attenuation unit, wherein an external attenuating optical medium is inserted between the variable optical attenuation unit and the second optical amplification unit. The optical amplifier includes an abnormality detecting unit that detects abnormality in optical loss based on a light level between the external attenuating optical medium and the second optical amplification unit, and a detection invalidating unit that invalidates any abnormality detected by the abnormality detecting unit when a light level between the variable optical attenuation unit and the external attenuating optical medium is lower than a threshold level.Type: GrantFiled: June 23, 2009Date of Patent: February 1, 2011Assignee: Fujitsu LimitedInventors: Kosuke Komaki, Yuji Tamura
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Patent number: 7756422Abstract: During initial start-up of an optical communication system, an ASE reference span loss is calculated based on transmitting power and received power of ASE light generated by an optical amplifier, and an OSC reference span loss is calculated based on the transmitting power and the received power of OSC light. During normal operation of the optical communication system, a span loss is calculated using the OSC light, and an amount of change in the span loss representing a difference between the span loss and the OSC reference span loss is calculated. A current span loss between a transmitting station and a receiving station is calculated by adding the amount of change in the span loss to the ASE reference span loss.Type: GrantFiled: August 11, 2006Date of Patent: July 13, 2010Assignee: Fujitsu LimitedInventors: Takeshi Sakamoto, Kosuke Komaki, Yuji Shimada, Takuji Maeda
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Publication number: 20090257115Abstract: An optical amplifier includes a first optical amplification unit that amplifies input light, a variable optical attenuation unit that attenuates an output of the first optical amplification unit, a second optical amplification unit that amplifies an output of the variable optical attenuation unit, and a loss amount control unit that controls the variable optical attenuation unit, wherein an external attenuating optical medium is inserted between the variable optical attenuation unit and the second optical amplification unit. The optical amplifier includes an abnormality detecting unit that detects abnormality in optical loss based on a light level between the external attenuating optical medium and the second optical amplification unit, and a detection invalidating unit that invalidates any abnormality detected by the abnormality detecting unit when a light level between the variable optical attenuation unit and the external attenuating optical medium is lower than a threshold level.Type: ApplicationFiled: June 23, 2009Publication date: October 15, 2009Applicant: FUJITSU LIMITEDInventors: Kosuke KOMAKI, Yuji Tamura
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Publication number: 20080080867Abstract: According to a WDM optical transmission system of the present invention, wavelength numbers information of a WDM signal light output from an upstream side optical amplifying unit to a transmission path fiber, and signal output level information thereof are transmitted to a downstream side optical amplifying unit utilizing a supervisory control light. In the downstream side optical amplifying unit, a loss (span loss) in the transmission path fiber is computed using the upstream side signal output level information and downstream side signal input level information, so that a gain to be set for a downstream side optical amplifier is calculated based on the computed loss, and also, the gain is corrected based on a difference between a target value of the signal output level computed using the wavelength numbers information and an actual measurement value thereof, so that the optical amplifier is controlled in accordance with the post-corrected gain.Type: ApplicationFiled: July 30, 2007Publication date: April 3, 2008Applicant: FUJITSU LIMITEDInventors: Hiroyuki Itoh, Kosuke Komaki