Patents by Inventor Olga I. Vassilieva

Olga I. Vassilieva 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: 11012187
    Abstract: An optical transmitter for probabilistic shaping and symbol rate optimization includes one or more matcher elements, each configured to assign respective probabilities to symbols represented in received binary data dependent on a target probability distribution and to output a respective shaped bit sequence. The optical transmitter further includes a single systematic error correction encoder configured to add parity bits collectively across the shaped bit sequences and to output a combined shaped bit sequence including data representing the shaped bit sequences and the added parity bits. The optical transmitter also includes multiple mapping elements, each configured to generate a respective codeword for each symbol represented in a portion of the combined shaped bit sequence, a serial-to-parallel converter to provide portions of the combined shaped bit sequence to the mapping elements, and a multiplexer to combine binary data representing the codewords for transmission using subcarrier multiplexing.
    Type: Grant
    Filed: March 4, 2020
    Date of Patent: May 18, 2021
    Assignee: Fujitsu Limited
    Inventors: Inwoong Kim, Olga I. Vassilieva, Paparao Palacharla, Tadashi Ikeuchi
  • Patent number: 10700807
    Abstract: Systems and methods for setting fiber input power for an optical transmission path may include determining an initial modulation format representing a uniform distribution QAM format, the initial modulation format associated with a first fiber input power and a first spectral efficiency, configuring optical transponders to apply probabilistic shaping to the initial modulation format when transmitting traffic over the optical transmission path, the traffic including probabilistically shaped signals with a second spectral efficiency, determining, dependent on the second spectral efficiency, a second fiber input power, and configuring optical amplifiers along the optical transmission path to transmit the traffic comprising the probabilistically shaped signals over the optical transmission path using the second fiber input power.
    Type: Grant
    Filed: July 1, 2019
    Date of Patent: June 30, 2020
    Assignee: Fujitsu Limited
    Inventors: Olga I. Vassilieva, Inwoong Kim, Tadashi Ikeuchi
  • Patent number: 10601517
    Abstract: A system and method for probabilistic shaping of an eight-dimensional super-symbol in optical transport networks, including receiving binary data to be transmitted as an optical signal; mapping at least a portion of the binary data to symbols of a M-QAM constellation; generating a first four-dimensional symbol of the M-QAM constellation for a first symbol period, including applying probabilistic shaping to the first four-dimensional symbol; generating a second four-dimensional symbol of the M-QAM constellation for a second symbol period, the second symbol period consecutive to the first symbol period, wherein the first and the second four-dimensional symbols have i) an equal symbol energy and ii) a one-to-one relationship; and time interleaving the first symbol period and the second symbol period to generate an eight-dimensional super-symbol.
    Type: Grant
    Filed: January 22, 2019
    Date of Patent: March 24, 2020
    Assignee: Fujitsu Limited
    Inventors: Inwoong Kim, Sebastiaan Anne René Goossens, Olga I. Vassilieva, Tadashi Ikeuchi
  • Patent number: 10530490
    Abstract: Systems and methods for constellation shaping of QAM modulation formats in an optical transport network may include selecting a target information rate for an optical transmission path, determining a measure of fiber nonlinearity for transmission media on the path, and selecting, dependent on the measure of fiber nonlinearity, one of multiple supported shaping parameter pairs, each specifying a respective shaping strength level and a respective error correction strength level. A network management system may configure optical transponders to apply probabilistic shaping to a QAM modulation format in accordance with the selected shaping parameter pair. A shaping parameter pair specifying a high shaping strength level and a low error correction strength level may be selected when the measure of fiber nonlinearity is high. A shaping parameter pair specifying a low shaping strength level and a high error correction strength level may be selected when the measure of fiber nonlinearity is low.
    Type: Grant
    Filed: February 27, 2019
    Date of Patent: January 7, 2020
    Assignee: Fujitsu Limited
    Inventors: Olga I. Vassilieva, Inwoong Kim, Tadashi Ikeuchi
  • Patent number: 10511388
    Abstract: Systems and methods for reducing variance in reach of wavelength division multiplexed (WDM) channels in optical transport networks may include selecting, for each channel assigned to a respective wavelength, an initial modulation format and an initial distribution of constellation points in the complex plane, determining a target reach for all WDM channels that is achievable by higher wavelength channels but not by shorter wavelength channels, and applying one or more reach extension techniques to at least one shorter wavelength channel but not to the higher wavelength channels. The reach extension techniques may include probabilistic constellation shaping, symbol rate optimized subcarrier multiplexing, or a combination of the two. Transponders may be configurable to transmit or receive traffic over the WDM channels with or without implementing the reach extension techniques, as applicable.
    Type: Grant
    Filed: August 10, 2018
    Date of Patent: December 17, 2019
    Assignee: Fujitsu Limited
    Inventors: Olga I. Vassilieva, Inwoong Kim, Tadashi Ikeuchi
  • Patent number: 10396899
    Abstract: Systems and methods for constellation shaping of M-QAM modulation formats in optical transport networks may receive binary data to be transmitted as an optical signal and partition symbols of an M-QAM constellation in the complex plane into two non-overlapping subsets of symbols, The systems and methods may include assigning respective probabilities to each symbol in the first subset of symbols dependent on a target probability distribution for the first subset, mapping at least a portion of the received binary data to the symbols in the first subset, including generating a respective codeword for each symbol in the first subset, in a first symbol period, providing data representing the respective codewords mapped to the symbols in the first subset to an optical modulator for transmission, and refraining from providing any data representing codewords mapped to the symbols in the second subset to the optical modulator until a second symbol period.
    Type: Grant
    Filed: August 21, 2018
    Date of Patent: August 27, 2019
    Assignee: Fujitsu Limited
    Inventors: Inwoong Kim, Olga I. Vassilieva, Paparao Palacharla, Tadashi Ikeuchi
  • Patent number: 10389473
    Abstract: A disclosed method for extending reach in an adaptive optical network may include selecting, for an optical channel having a given target distance and a given maximum data rate, the modulation format having the highest spectral efficiency among modulation formats supported in the adaptive optical network that are suitable for optical channels having the given target distance and the given maximum data rate, determining a symbol rate for the optical channel dependent on characteristics of transmission media for the optical channel, determining a number of subcarriers for the optical channel corresponding to the determined symbol rate, and activating subcarrier multiplexing (SCM) for the optical channel. Activating SCM may include configuring transponders to transmit or receive the traffic in the optical channel using the selected modulation format and the determined number of subcarriers. The method may be implemented by a network management system of the optical network.
    Type: Grant
    Filed: April 27, 2018
    Date of Patent: August 20, 2019
    Assignee: Fujitsu Limited
    Inventors: Olga I. Vassilieva, Inwoong Kim, Tadashi Ikeuchi
  • Patent number: 10225008
    Abstract: A disclosed method for configuring an optical network includes determining that a measure of performance for a first optical path is approaching a safe threshold and designating the first optical path as at risk for performance degradation due to additional traffic. The method also includes, in response to adding a new optical path, calculating a system margin for the first optical path representing a difference between an OSNR delivered on the first optical path and a required OSNR for error-free operation on the first optical path, determining that the system margin is insufficient to meet an applicable performance level, modifying an operating parameter of a transmitter or receiver of the first optical path and refraining from calculating a system margin for a second optical path that is not designated as at risk for performance degradation. The method may be implemented by a network management system of the optical network.
    Type: Grant
    Filed: April 27, 2018
    Date of Patent: March 5, 2019
    Assignee: Fujitsu Limited
    Inventors: Olga I. Vassilieva, Inwoong Kim, Tadashi Ikeuchi
  • Patent number: 9941994
    Abstract: Methods and systems are provided for wavelength shift elimination during spectral inversion in optical networks. The method includes receiving an input optical signal, and generating a combined optical signal by combining, by Bragg scattering, the input optical signal having an input wavelength with a first pump signal having a first wavelength. The method further includes converting the combined optical signal into an output optical signal, by phase-conjugation, using a second pump signal having a second wavelength. The output optical signal has the same wavelength as the input optical signal.
    Type: Grant
    Filed: October 30, 2015
    Date of Patent: April 10, 2018
    Assignee: Fujitsu Limited
    Inventors: Kevin Croussore, Inwoong Kim, Olga I. Vassilieva, Takao Naito
  • Publication number: 20170126353
    Abstract: Methods and systems are provided for wavelength shift elimination during spectral inversion in optical networks. The method includes receiving an input optical signal, and generating a combined optical signal by combining, by Bragg scattering, the input optical signal having an input wavelength with a first pump signal having a first wavelength. The method further includes converting the combined optical signal into an output optical signal, by phase-conjugation, using a second pump signal having a second wavelength. The output optical signal has the same wavelength as the input optical signal.
    Type: Application
    Filed: October 30, 2015
    Publication date: May 4, 2017
    Inventors: Kevin Croussore, Inwoong Kim, Olga I. Vassilieva, Takao Naito
  • Patent number: 9515734
    Abstract: In one embodiment, a method for receiving optical signals includes receiving a first set of one or more signals and a second set of one or more signals, determining a block length used to process the first set of signals, and processing the first set of signals using the block length. The first set of signals and the second set of signals are separated by a guard band. The block length is based upon the width of the guard band.
    Type: Grant
    Filed: July 16, 2010
    Date of Patent: December 6, 2016
    Assignee: Fujitsu Limited
    Inventors: Inwoong Kim, Olga I. Vassilieva
  • Patent number: 8798481
    Abstract: In accordance with embodiments of the present disclosure, a method for compensation of noise in an optical device is provided. The method may include calculating noise present in an optical carrier signal. The method may also include generating quadrature amplitude modulation input signals, the quadrature amplitude modulation input signals each including a term for compensation of the noise based on the calculated noise. The method may further include modulating the optical carrier signal to generate a modulated optical signal based on quadrature amplitude modulation input signals.
    Type: Grant
    Filed: December 14, 2010
    Date of Patent: August 5, 2014
    Assignee: Fujitsu Limited
    Inventors: Inwoong Kim, Olga I. Vassilieva
  • Patent number: 8644704
    Abstract: In accordance with an embodiment of the present disclosure a method for adaptively spacing channels of an optical network comprises determining a first desired power level of a first channel of an optical network. The method further comprises determining a second desired power level of a second channel of the optical network, the second desired power level being less than the first desired power level. Additionally, the method comprises determining a first spectral space between the first channel and one or more channels neighboring the first channel based at least on the first desired power level. The method also comprises determining a second spectral space between the second channel and one or more channels neighboring the second channel based at least on the second desired power level, the second spectral space less than the first spectral space.
    Type: Grant
    Filed: April 21, 2011
    Date of Patent: February 4, 2014
    Assignee: Fujitsu Limited
    Inventors: Olga I Vassilieva, Motoyoshi Sekiya, Martin Bouda
  • Patent number: 8543000
    Abstract: In accordance with the present disclosure a system for reducing polarization dependent loss (PDL) of an optical signal comprises a delay module coupled to one or more PDL inducing network elements of an optical network. The delay module is configured to time interleave a first polarization component with respect to a second polarization component of the optical signal. The time interleaving reduces interference caused by cross-talk components associated with the first and second polarization components and induced by the PDL of the PDL inducing elements.
    Type: Grant
    Filed: September 10, 2010
    Date of Patent: September 24, 2013
    Assignee: Fujitsu Limited
    Inventors: Olga I Vassilieva, 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: 8467690
    Abstract: Methods and systems are provided for cancellation of chromatic dispersion combined laser phase noise. A method may include measuring a differential of laser phase noise using two optical pilot signals, the pilot signals each having a different optical frequency, or using an optical carrier and a pilot signal. The method may also include determining an approximate laser phase noise present in an optical system based on the measured differential of laser phase noise. The method may further include compensating for laser phase noise based on the determined approximate laser phase noise.
    Type: Grant
    Filed: September 10, 2010
    Date of Patent: June 18, 2013
    Assignee: Fujitsu Limited
    Inventors: Inwoong Kim, Takao Naito, Olga I. Vassilieva
  • Patent number: 8401389
    Abstract: A method for compensating for optical dispersion includes receiving an optical signal at a first node of an optical network that includes a first set of channels and a second set of channels that are each configured to be received using coherent digital receivers at a second node of the optical network. Each coherent digital receiver provides electronic dispersion compensation for the received channel at the second node. The method also includes forwarding the first set of channels from the first node without performing optical dispersion compensation on those channels. Furthermore, the method includes compensating for optical dispersion in the second set of channels at the first optical node and forwarding those channels from the first node. The optical dispersion compensation on the second set of channels at the first node provides dispersion compensation in addition to the compensation provided by the associated coherent digital receivers at the second node.
    Type: Grant
    Filed: March 12, 2010
    Date of Patent: March 19, 2013
    Assignee: Fujitsu Limited
    Inventor: Olga I Vassilieva
  • Patent number: 8369442
    Abstract: A transmitter modulator that is operable to modulate signals according to multiple modulation formats includes a first modulator, a second modulator, and a polarization beam combiner. The first modulator encodes a first signal according to a first modulation format. The second modulator encodes a second signal according to a second modulation format, the first signal orthogonally polarized with respect to the second signal. The polarization beam combiner combines the first signal and the second signal for transmission.
    Type: Grant
    Filed: January 12, 2007
    Date of Patent: February 5, 2013
    Assignee: Fujitsu Limited
    Inventors: Olga I. Vassilieva, Takao Naito
  • Publication number: 20120269506
    Abstract: In accordance with an embodiment of the present disclosure a method for adaptively spacing channels of an optical network comprises determining a first desired power level of a first channel of an optical network. The method further comprises determining a second desired power level of a second channel of the optical network, the second desired power level being less than the first desired power level. Additionally, the method comprises determining a first spectral space between the first channel and one or more channels neighboring the first channel based at least on the first desired power level. The method also comprises determining a second spectral space between the second channel and one or more channels neighboring the second channel based at least on the second desired power level, the second spectral space less than the first spectral space.
    Type: Application
    Filed: April 21, 2011
    Publication date: October 25, 2012
    Applicant: FUJITSU LIMITED
    Inventors: Olga I. Vassilieva, Motoyoshi Sekiya, Martin Bouda
  • Patent number: 8270835
    Abstract: A method for reducing cross-phase modulation in an optical signal includes receiving an optical signal comprising a plurality of channels, wherein the information being communicated in a first set of one or more of the channels is modulated using one or more single-polarization modulation techniques and wherein the information being communicated in a second set of one or more of the channels is modulated using one or more dual-polarization modulation techniques. The method also includes splitting the optical signal into at least a first copy of the optical signal and a second copy of the optical signal and terminating the second set of channels in the first copy. Furthermore, the method includes applying a differential group delay to the second copy, the differential group delay introducing a walk-off between symbols communicated in a first polarization component of the second set of channels and the symbols of a second polarization component of the second set of channels.
    Type: Grant
    Filed: March 31, 2010
    Date of Patent: September 18, 2012
    Assignee: Fujitsu Limited
    Inventors: Kevin Croussore, Inwoong Kim, Olga I. Vassilieva