Patents by Inventor Youichi Akasaka

Youichi Akasaka 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: 20150200724
    Abstract: The present disclosure includes a computer-implemented method of correcting a measured optical signal-to-noise ratio (OSNR) comprising receiving an optical signal and measuring OSNR of the optical signal using an interferometric OSNR monitor device. The method also includes applying a correction table to the measured OSNR to generate a corrected OSNR using a controller, the correction table comprising a correction function to counteract an artifact in the measured OSNR. The method also includes storing the corrected OSNR in a non-transitory computer-readable medium. The present disclosure also includes associated devices applying the correction table and methods of generating the correction table.
    Type: Application
    Filed: January 13, 2014
    Publication date: July 16, 2015
    Applicant: Fujitsu Limited
    Inventors: Jeng-Yuan Yang, Youichi Akasaka, Motoyoshi Sekiya, Takuji Maeda, Hiroki Ooi, Kentaro Nakamura, Satoru Okano
  • Publication number: 20140369678
    Abstract: The present disclosure includes a method of determining optical signal-to-noise ratio (OSNR) of a signal, comprising separating one polarization component from a plurality of polarization components in an optical signal, selecting one wavelength from a plurality of wavelengths in the optical signal, delaying a first portion of the one polarization component of the one wavelength of the optical signal, shifting a phase of the first portion by a first amount and the first amount plus pi radians, causing the first portion to interfere with a second portion, measuring a power of the interference of the first and second portions, receiving the power of the interference, and comparing the power of the interference when the phase is shifted by the first amount with the interference when the phase is shifted by the first amount plus pi radians to determine OSNR. The present disclosure also includes associated devices.
    Type: Application
    Filed: June 18, 2013
    Publication date: December 18, 2014
    Inventors: Jeng-Yuan Yang, Youichi Akasaka, Motoyoshi Sekiya, Takuji Maeda, Hiroki Ooi, Satoru Okano
  • Patent number: 8909063
    Abstract: A method for regenerating and amplifying optical signals includes determining a source optical signal, adding a first pump optical signal and a second pump optical signal to the source optical signal to yield an intermediate optical signal, duplicating the intermediate optical signal to yield a first duplicate signal and a second duplicate signal, phase-shifting the first duplicate signal, passing the phase-shifted first duplicate signal and the second duplicate signal bi-directionally through a nonlinear optical element, and performing degenerate phase-sensitive amplification on the phase-shifted first duplicate signal and the second duplicate signal.
    Type: Grant
    Filed: October 31, 2012
    Date of Patent: December 9, 2014
    Assignee: Fujitsu Limited
    Inventors: Jeng-Yuan Yang, Youichi Akasaka, Motoyoshi Sekiya, Inwoong Kim
  • Patent number: 8909062
    Abstract: A method for regenerating optical signal includes determining a source optical signal to be regenerated, adding a first pump optical signal and a second pump optical signal to the source optical signal to yield an intermediate optical signal, creating a first conjugate optical signal and a second conjugate optical signal from the intermediate optical signal, and performing degenerate phase-sensitive amplification utilizing the first conjugate optical signal, the second conjugate optical signal and the source optical signal to yield an output optical signal. The source optical signal is modulated with a multilevel modulation format. Each conjugate optical signal has a phase that is a conjugate of a multiple of the phase of the source optical signal.
    Type: Grant
    Filed: June 18, 2012
    Date of Patent: December 9, 2014
    Assignee: Fujitsu Limited
    Inventors: Jeng-yuan Yang, Youichi Akasaka, Motoyoshi Sekiya, Inwoong Kim
  • Publication number: 20140355105
    Abstract: A method for regenerating optical signals includes determining an input including a source amplitude-modulated optical signal, regenerating the source amplitude-modulated optical signal by using successive saturation modes of amplification, and producing an output optical signal from the regeneration. The source amplitude-modulated optical signal includes input power modulation levels that each indicate information carried on the source amplitude-modulated optical signal. The output optical signal includes output power modulation levels that include information equivalent to information of the input power modulation levels.
    Type: Application
    Filed: May 31, 2013
    Publication date: December 4, 2014
    Inventors: Youichi Akasaka, Jeng-Yuan Yang
  • Patent number: 8873950
    Abstract: In accordance with the present disclosure, disadvantages and problems associated with transmitting high capacity (e.g., 400 G) optical signals may be reduced. In accordance with an embodiment of the present disclosure a method for regenerating an optical signal comprises receiving an optical signal at a network element and measuring a performance characteristic of the optical signal. The method further comprises determining that the optical signal needs regeneration based on the performance characteristic of the optical signal. The method additionally comprises performing signal regeneration of the optical signal based on the determination that the optical signal needs regeneration.
    Type: Grant
    Filed: October 4, 2011
    Date of Patent: October 28, 2014
    Assignee: Fujitsu Limited
    Inventor: Youichi Akasaka
  • Patent number: 8798454
    Abstract: Systems and methods for distributing signals in an optical network are disclosed. In accordance with one embodiment of the present disclosure a method for distributing signals in an optical network comprises combining input signals into one or more output signals, determining, an availability status of optical lanes for carrying the output signals and distributing the output signals to optical transmitters associated with the optical lanes if the availability status indicates that the optical lanes are available.
    Type: Grant
    Filed: June 28, 2010
    Date of Patent: August 5, 2014
    Assignee: Fujitsu Limited
    Inventor: Youichi Akasaka
  • Publication number: 20140119743
    Abstract: A method for regenerating and amplifying optical signals includes determining a source optical signal, adding a first pump optical signal and a second pump optical signal to the source optical signal to yield an intermediate optical signal, duplicating the intermediate optical signal to yield a first duplicate signal and a second duplicate signal, phase-shifting the first duplicate signal, passing the phase-shifted first duplicate signal and the second duplicate signal bi-directionally through a nonlinear optical element, and performing degenerate phase-sensitive amplification on the phase-shifted first duplicate signal and the second duplicate signal.
    Type: Application
    Filed: October 31, 2012
    Publication date: May 1, 2014
    Applicant: FUJITSU NETWORK COMMUNICATIONS, INC.
    Inventors: Jeng-Yuan Yang, Youichi Akasaka, Motoyoshi Sekiya, Inwoong Kim
  • Patent number: 8705167
    Abstract: In accordance with one embodiment of the present disclosure a system for compensating for polarization dependent loss experienced by an optical signal comprises an optical amplifier configured to amplify an optical signal and having a polarization dependent gain (PDG). The system also comprises a polarization rotator coupled to the amplifier and configured to rotate the polarization of the optical signal before the signal enters the amplifier. The system also comprises a polarization dependent loss (PDL) controller coupled to the amplifier and the rotator. The PDL controller may be configured to determine a post-amplifier PDL of the optical signal as the signal leaves the optical amplifier. The PDL controller may also be configured to control the rotator to rotate the polarization of the optical signal based on the post-amplifier PDL, such that the PDG of the amplifier compensates for the PDL experienced by the optical signal.
    Type: Grant
    Filed: August 25, 2010
    Date of Patent: April 22, 2014
    Assignee: Fujitsu Limited
    Inventor: Youichi Akasaka
  • Publication number: 20140102148
    Abstract: In certain embodiment, a fiber fusion apparatus for mitigating polarization dependent splice loss include a first fiber guide operable to maintain alignment of a first optical fiber relative to a center axis and a second fiber guide operable to maintain alignment of a second optical fiber relative to the center axis. The apparatus further includes three or more electrodes evenly-spaced around the center axis. Each of the three or more electrodes is operable to apply heat to adjacent ends of the first and second optical fibers in order to fuse the first and second optical fibers.
    Type: Application
    Filed: October 11, 2012
    Publication date: April 17, 2014
    Applicant: Fujitsu Limited
    Inventor: Youichi Akasaka
  • Publication number: 20140037290
    Abstract: In accordance with an embodiment of the present disclosure a network element comprises a plurality of optically absorbent layers. Each layer of the plurality of optically absorbent layers is configured to receive an optical signal such that the optical signal passes through the layer. The optical signal has a specific polarization state and is associated with noise having a plurality of randomly varying polarization states. Each layer absorbs optical waves having a particular polarization state. The particular polarization state of each layer is different from the polarization state associated with the other layers of the plurality of optically absorbent layers. The plurality of layers are coupled together such that as the optical signal and associated noise pass through the plurality of layers, the network element absorbs the associated noise more than the polarized optical signal to improve an Optical Signal to Noise Ratio (OSNR) of the optical signal.
    Type: Application
    Filed: August 2, 2012
    Publication date: February 6, 2014
    Applicant: Fujitsu Limited
    Inventor: Youichi Akasaka
  • Publication number: 20130272702
    Abstract: A method for regenerating optical signal includes determining a source optical signal to be regenerated, adding a first pump optical signal and a second pump optical signal to the source optical signal to yield an intermediate optical signal, creating a first conjugate optical signal and a second conjugate optical signal from the intermediate optical signal, and performing degenerate phase-sensitive amplification utilizing the first conjugate optical signal, the second conjugate optical signal and the source optical signal to yield an output optical signal. The source optical signal is modulated with a multilevel modulation format. Each conjugate optical signal has a phase that is a conjugate of a multiple of the phase of the source optical signal.
    Type: Application
    Filed: June 18, 2012
    Publication date: October 17, 2013
    Applicant: FUJITSU NETWORK COMMUNICATIONS, INC.
    Inventors: Jeng-yuan Yang, Youichi Akasaka, Motoyoshi Sekiya, Inwoong Kim
  • Patent number: 8543006
    Abstract: A method is provided for reducing polarization dependent loss experienced by an optical signal comprises monitoring a power level of a polarization multiplexed optical signal. The method further comprises detecting a power spike based on the monitored power. The power spike is induced by misalignment of a polarization component axis of the optical signal with a polarization dependent loss (PDL) axis of one or more network elements. The method further comprises rotating the polarization orientation of the optical signal such that the power spike is reduced.
    Type: Grant
    Filed: September 10, 2010
    Date of Patent: September 24, 2013
    Assignee: Fujitsu Limited
    Inventors: Olga I Vassilieva, Youichi Akasaka
  • Patent number: 8437074
    Abstract: A Raman amplifier according to the present invention comprises a plurality of pumping means using semiconductor lasers of Fabry-Perot, DFB, or DBR type or MOPAs, and pumping lights outputted from the pumping means have different central wavelengths, and interval between the adjacent central wavelength is greater than 6 nm and smaller than 35 nm. An optical repeater according to the present invention comprises the above-mentioned Raman amplifier and adapted to compensate loss in an optical fiber transmission line by the Raman amplifier. In a Raman amplification method according to the present invention, the shorter the central wavelength of the pumping light the higher light power of said pumping light.
    Type: Grant
    Filed: February 8, 2011
    Date of Patent: May 7, 2013
    Assignee: Furukawa Electric Co., Ltd.
    Inventors: Youichi Akasaka, Yoshihiro Emori, Shu Namiki
  • Publication number: 20130084064
    Abstract: In accordance with the present disclosure, disadvantages and problems associated with transmitting high capacity (e.g., 400 G) optical signals may be reduced. In accordance with an embodiment of the present disclosure a method for regenerating an optical signal comprises receiving an optical signal at a network element and measuring a performance characteristic of the optical signal. The method further comprises determining that the optical signal needs regeneration based on the performance characteristic of the optical signal. The method additionally comprises performing signal regeneration of the optical signal based on the determination that the optical signal needs regeneration.
    Type: Application
    Filed: October 4, 2011
    Publication date: April 4, 2013
    Applicant: FUJITSU LIMITED
    Inventor: Youichi Akasaka
  • Patent number: 8284479
    Abstract: A system for optical communication including an optical amplifier card configured to receive a plurality of pump laser modules. The optical amplifier card includes a receptacle configured to receive the pump laser module, a connector configured to couple the pump laser module to the optical amplifier card, a monitor configured to measure at least the optical output power of the pump laser module, and a pump combiner communicatively coupled to the monitor. The pump combiner is configured to receive a signal from the monitor indicating a drop in the output power of a first pump laser module below a threshold level, and, in response to the signal, switch the optical amplifier card from using the optical power of the first pump laser module to using the optical power of a second pump laser module without substantially affecting normal operation of the optical amplifier card.
    Type: Grant
    Filed: August 18, 2009
    Date of Patent: October 9, 2012
    Assignee: Fujitsu Limited
    Inventors: Youichi Akasaka, Takao Naito
  • Publication number: 20120063783
    Abstract: In accordance with the present disclosure a method for reducing polarization dependent loss experienced by an optical signal comprises monitoring a power level of a polarization multiplexed optical signal. The method further comprises detecting a power spike based on the monitored power. The power spike is induced by misalignment of a polarization component axis of the optical signal with a polarization dependent loss (PDL) axis of one or more network elements. The method further comprises rotating the polarization orientation of the optical signal such that the power spike is reduced.
    Type: Application
    Filed: September 10, 2010
    Publication date: March 15, 2012
    Applicant: FUJITSU LIMITED
    Inventors: Olga I. Vassilieva, Youichi Akasaka
  • Publication number: 20120050846
    Abstract: In accordance with one embodiment of the present disclosure a system for compensating for polarization dependent loss experienced by an optical signal comprises an optical amplifier configured to amplify an optical signal and having a polarization dependent gain (PDG). The system also comprises a polarization rotator coupled to the amplifier and configured to rotate the polarization of the optical signal before the signal enters the amplifier. The system also comprises a polarization dependent loss (PDL) controller coupled to the amplifier and the rotator. The PDL controller may be configured to determine a post-amplifier PDL of the optical signal as the signal leaves the optical amplifier. The PDL controller may also be configured to control the rotator to rotate the polarization of the optical signal based on the post-amplifier PDL, such that the PDG of the amplifier compensates for the PDL experienced by the optical signal.
    Type: Application
    Filed: August 25, 2010
    Publication date: March 1, 2012
    Applicant: FUJITSU LIMITED
    Inventor: Youichi Akasaka
  • Patent number: 8107815
    Abstract: In one embodiment, a method for providing wireless communications utilizing a passive optical network (PON) is disclosed. The method includes receiving, at a PON, downstream packets from a base station destined for a mobile station, and transmitting the downstream packets to wireless transceivers associated with PON. The method also includes receiving, at the first wireless transceiver communicatively coupled to a first optical network terminal (ONT), the downstream packets from the first ONT and transmitting a first wireless signal comprising the downstream packets to a first cell. The method also includes receiving, at a second wireless transceiver communicatively coupled to a second ONT, the downstream packets from the second ONT and transmitting a second wireless signal comprising the downstream packets to a second cell.
    Type: Grant
    Filed: March 31, 2008
    Date of Patent: January 31, 2012
    Assignee: Fujitsu Limited
    Inventors: Youichi Akasaka, Takao Naito, Satoshi Mizutani
  • Publication number: 20110317994
    Abstract: Systems and methods for distributing signals in an optical network are disclosed. In accordance with one embodiment of the present disclosure a method for distributing signals in an optical network comprises combining input signals into one or more output signals, determining, an availability status of optical lanes for carrying the output signals and distributing the output signals to optical transmitters associated with the optical lanes if the availability status indicates that the optical lanes are available.
    Type: Application
    Filed: June 28, 2010
    Publication date: December 29, 2011
    Applicant: FUJITSU LIMITED
    Inventor: Youichi Akasaka