Having Feedback Patents (Class 398/206)
  • Patent number: 9325425
    Abstract: A DPSK/DQPSK receiver includes an optical splitter that separates the received DPSK/DQPSK optical signal according to an optical power splitting ratio into a plurality of received optical signals. A plurality of optical filters passes a plurality of filtered received optical signals. A plurality of optical detectors generates a plurality of electrical detection signals, each with a power that is related to a power of a respective filtered optical signal. A plurality of amplifiers generates a plurality of amplified electrical signals. At least one electrical signal combiner combines the plurality of amplified electrical detection signals generated by the plurality of optical amplifiers into a combined reception signal.
    Type: Grant
    Filed: February 23, 2009
    Date of Patent: April 26, 2016
    Assignee: Finisar Corporation
    Inventors: Er'el Granot, Shalva Ben-Ezra, Yinnon Stav, Sagie Tsadka, Heider Ereifej
  • Patent number: 9048956
    Abstract: In a coherent optical receiver device, the dynamic range considerably decreases in the case of selectively receiving the optical multiplexed signals by means of the wavelength of the local oscillator light, therefore, a coherent optical receiver device according to an exemplary aspect of the invention includes a coherent optical receiver receiving optical multiplexed signals in a lump in which signal light is multiplexed; a variable optical attenuator; a local oscillator connected to the coherent optical receiver; and a first controller controlling the variable optical attenuator by means of a first control signal based on an output signal of the coherent optical receiver; wherein the coherent optical receiver includes a 90-degree hybrid circuit, a photoelectric converter, and an impedance conversion amplifier, and selectively detects the signal light interfering with local oscillation light output by the local oscillator out of the optical multiplexed signals; and the variable optical attenuator is disposed
    Type: Grant
    Filed: September 26, 2011
    Date of Patent: June 2, 2015
    Assignee: NEC CORPORATION
    Inventor: Kouichi Suzuki
  • Patent number: 9031420
    Abstract: An optical signal is converted into an electric signal by an O/E converter on the reception side, and converted into a digital signal by an analog/digital conversion unit. In a capture unit A at the input stage of the digital signal processing unit at the next stage, the constellation of a signal output from an analog/digital conversion unit is acquired for each polarization. According to the constellation information, the amplitude value of the electric signal input to the analog/digital conversion unit is corrected so that the value is optimum. Also, the capture unit B acquires the constellation on the signal after the demodulation by the digital signal processing. According to the constellation information, the amplitude of the I and Q signals and the skew between the I and Q signals are corrected.
    Type: Grant
    Filed: February 5, 2013
    Date of Patent: May 12, 2015
    Assignee: Fujitsu Limited
    Inventor: Yuichirou Sakamoto
  • Patent number: 9020365
    Abstract: Current optical networks are engineered to handle amplifier noise and chromatic dispersion. Polarization mode dispersion occurs in optical networks due splitting of the light energy of a pulse propagating in a fiber into two modes. Compensating for polarization mode dispersion is a difficult and expensive task and hence only few commercial systems have been deployed to deal with this issue. A polarization mode dispersion compensation module according to an example embodiment of the present invention compensates for polarization mode dispersion by determining a performance metric related to an error rate of an optical signal in at least one polarization mode in a filtered state. Based on the performance metric, a control vector is determined to control the optical signal in the at least one polarization mode in the filtered state. The control vector is then applied to a polarization effecting device to compensate for polarization mode dispersion.
    Type: Grant
    Filed: April 8, 2008
    Date of Patent: April 28, 2015
    Assignee: Tellabs Operations, Inc.
    Inventors: Richard C. Younce, Julia Y. Larikova
  • Patent number: 9014574
    Abstract: In order to appropriately demultiplex the polarization multiplexed BPSK signal without using a training sequence and decreasing the resistance to a frequency offset, an optical receiver includes a coherent optical detection unit receiving an optical signal in which BPSK modulated carrier waves are polarization-multiplexed, performing coherent detection by mixing the received optical signal with local light, and outputting first electrical signals corresponding to the carrier waves; a butterfly FIR filter receiving the first electrical signals and extracting second electrical signals corresponding to each of the carrier waves from the first electrical signals; and a coefficient control unit for calculating a sum of respective phases of the second electrical signals output from the butterfly FIR filter, adaptively controlling tap coefficients of the butterfly FIR filter so that the calculated phase sum may become equal to 0 or ?, and outputting tap coefficients after being controlled to the butterfly FIR filter
    Type: Grant
    Filed: February 28, 2012
    Date of Patent: April 21, 2015
    Assignee: NEC Corporation
    Inventors: Manabu Arikawa, Daisaku Ogasahara, Emmanuel Le Taillandier de Gabory, Kiyoshi Fukuchi
  • Patent number: 8983309
    Abstract: A transmitter in an optical communications system includes a digital signal processor for processing a data signal to generate a sample stream encoding successive symbols in accordance with a constrained phase modulation scheme having a constellation of at least two symbols and a modulation phase constrained to a phase range spanning less than 4?. A digital-to-analog converter converts the sample stream into a corresponding analog drive signal. A finite range phase modulator modulates a phase of a continuous wavelength channel light in accordance with the analog drive signal, to generate a modulated channel light for transmission through the optical communications system. A receiver in the optical communications system includes an optical stage for detecting phase and amplitude of the modulated channel light and for generating a corresponding sample stream, and a digital signal processor for processing the sample stream to estimate each successive symbol of the modulated channel light.
    Type: Grant
    Filed: February 13, 2012
    Date of Patent: March 17, 2015
    Assignee: Ciena Corporation
    Inventors: James Harley, Douglas McGhan, Shahab Oveis Gharan, Kim B. Roberts, Mark Rollins
  • Patent number: 8977137
    Abstract: An apparatus including a polarization controller is described. The polarizer controller is communicatively coupled via a feedback loop to an evaluation module located near an optical receiver. The evaluation module is configured to measure polarization dependent loss (PDL) of an optical signal received at the optical receiver. The polarization controller is configured to receive feedback control data regarding the PDL from the evaluation module. Additionally, the polarization controller is configured to modify a state of polarization of the optical signal at an optical transmitter, which is communicatively coupled to the optical receiver, based on the feedback control data.
    Type: Grant
    Filed: July 18, 2012
    Date of Patent: March 10, 2015
    Assignee: Fujitsu Limited
    Inventors: Olga Vassilieva, Inwoong Kim, Motoyoshi Sekiya
  • Patent number: 8942573
    Abstract: A device and method are disclosed for blind equalization of an optical signal to implement adaptive polarization recovery, Polarization Mode Dispersion (PMD) compensation, and residual Chromatic Dispersion (CD) compensation in a digital coherent optical communication system.
    Type: Grant
    Filed: October 19, 2012
    Date of Patent: January 27, 2015
    Assignee: AT&T Intellectual Property I, L.P.
    Inventor: Xiang Zhou
  • Patent number: 8929731
    Abstract: An apparatus for measuring performance of a coherent optical receiver includes a beam splitter splitting light into first and second paths, a first optical modulator modulating the first path light, a variable optical attenuator controlling an optical power of the first optical modulator, a first polarization controller transmitting a signal controlling polarization of an output of the variable optical attenuator to the coherent optical receiver, a second optical modulator modulating the second path light, a variable optical delay line delaying time of an output of the second optical modulator, a second polarization controller transmitting a signal controlling polarization of an output of the variable optical delay line to the coherent optical receiver, a network analyzer measuring performance of the coherent optical receiver and controlling the optical modulators, and a controller transmitting a control signal to the optical modulators.
    Type: Grant
    Filed: November 28, 2012
    Date of Patent: January 6, 2015
    Assignee: Electronics and Telecommunications Research Institute
    Inventors: Chun Ju Youn, Joong-Seon Choe, Jong-Hoi Kim, Duk Jun Kim, Yong-Hwan Kwon, Eun Soo Nam
  • Patent number: 8903255
    Abstract: A polarization-multiplexed signal receiver includes a polarization adjustment unit to adjust a polarization state of inputted polarization-multiplexed signal, which is carrying signal data on each of two polarized waves being inputted, based on a control signal and to output the adjusted polarization-multiplexed signal, an optical signal reception unit to convert the polarization-multiplexed signal having the adjusted polarization state into an analog electric signal and output the analog electric signal, an A/D conversion unit to convert the analog electric signal into a digital electric signal and output the digital electric signal, a digital signal processing unit to perform digital coherent processing to the digital electric signal and take out the signal data and a feedback control unit to generate the control signal based on quality of the signal data and output the signal data to the polarization adjustment unit.
    Type: Grant
    Filed: August 1, 2012
    Date of Patent: December 2, 2014
    Assignee: NEC Corporation
    Inventor: Takeshi Okamoto
  • Patent number: 8897396
    Abstract: Provided is a pulse receiver capable of receiving a burst signal and decoding the burst signal with a bit error rate reduced to a target value or less by controlling a determination threshold such that decoding success rate is equal to or less than a predetermined value. A decode unit 140 decodes a pulse train 20 to information 30, counts the number of decoding successes for a predetermined time period and outputs the counted number (decoding success rate DR) to a control unit 150. The control unit 150 uses as a basis the decoding success rate DR communicated from the decode unit 140 to control the set value of reference voltage Vth used in the comparator 130.
    Type: Grant
    Filed: August 15, 2012
    Date of Patent: November 25, 2014
    Assignees: Furukawa Electric Co., Ltd., Furukawa Automotive Systems Inc.
    Inventors: Hiroyuki Itohara, Kazutaka Kamimura, Yasushi Aoyagi
  • Patent number: 8873973
    Abstract: 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: Grant
    Filed: April 13, 2012
    Date of Patent: October 28, 2014
    Assignee: Fujitsu Limited
    Inventors: Kosuke Komaki, Hisao Nakashima
  • Patent number: 8873968
    Abstract: An optical field receiver comprises an optical branching circuit for branching a received optical multilevel signal into first and second optical signals, a first optical delayed demodulator for performing delayed demodulation on the first optical signal at a delay time T (T=symbol time), a second optical delayed demodulator for performing delayed demodulation on the second optical signal at the delay time T with an optical phase difference deviating from the first optical delayed demodulator by 90°, first and second optical receivers for converting each of the delayed demodulation signals representing x and y components of complex signals output from the first and second delayed demodulators into first and second electrical signals, and a field processing unit fort generating a first reconstructed signal representing an inter-symbol phase difference or a phase angle of a received symbol from the first and second electrical signals for each symbol time T.
    Type: Grant
    Filed: May 11, 2006
    Date of Patent: October 28, 2014
    Assignee: Hitachi, Ltd.
    Inventor: Nobuhiko Kikuchi
  • Patent number: 8861982
    Abstract: When designing a demodulator for a DPSK-modulated signal, it is required that optical phase modulation is performed fast and the demodulator has a long lifetime. To achieve this object, a delay line interferometer inside the demodulator performs adjustment of phase difference between two split lights caused to interfere, using a first optical phase modulation unit such as a Piezo actuator and a second optical phase modulation unit such as a heating element that operates slower in modulation speed than the first optical phase modulation unit and is slower in deterioration speed.
    Type: Grant
    Filed: January 6, 2011
    Date of Patent: October 14, 2014
    Assignee: Oclaro Japan, Inc.
    Inventors: Hideharu Mikami, Taichi Kogure
  • Patent number: 8861979
    Abstract: The present disclosure relates to the field of communications, and in particular, to a coherent receiver apparatus and a chromatic dispersion compensation method. The apparatus includes a polarization beam splitter and a chromatic dispersion compensation module. An optical splitter is disposed in front of the polarization beam splitter, and a chromatic dispersion monitoring module is connected between the optical splitter and the chromatic dispersion compensation module. The optical splitter is configured to split a modulated optical signal received by the coherent receiver apparatus and then transmit the split modulated optical signal to the chromatic dispersion monitoring module and the polarization beam splitter.
    Type: Grant
    Filed: August 2, 2012
    Date of Patent: October 14, 2014
    Assignee: Huawei Technologies Co., Ltd.
    Inventor: Ning Liu
  • Patent number: 8861980
    Abstract: A loop filter include: a register that stores a result of arithmetic operation performed on a complex signal and outputs the stored complex signal; a first multiplier that multiplies the complex signal output from the register and a predetermined coefficient; an absolute value judging unit that outputs a multiplier coefficient used to control such that the amplitude of the complex signal output from the register is held in a predetermined range; a multiplier that multiplies an output from the first multiplier and the multiplier coefficient; a second multiplier that multiplies an input signal and a value (1?the predetermined coefficient); and an adder that adds an output from the multiplier to an output from the second multiplier and inputs a result of addition into the register.
    Type: Grant
    Filed: September 15, 2011
    Date of Patent: October 14, 2014
    Assignee: Fujitsu Limited
    Inventors: Yasuo Ohtomo, Nobukazu Koizumi
  • Patent number: 8787777
    Abstract: A system may receive a group of electrical signals from an optical receiver and via a group of channels; identify a first signal, as a reference signal, that is received via a first channel; and identify a second signal, as an orthogonal signal, that is received via a second channel, where the second signal may be orthogonal to the first signal. The system may further measure a group of skew values based on a difference in arrival times between one or more other signals, of the group of electrical signals, and the reference signal or the orthogonal signal; generate a group of de-skew values based on at least a portion of the skew values; and transmit the de-skew values, to the optical receiver, where transmitting the de-skew values allows the optical receiver to de-skew signals on the group of channels.
    Type: Grant
    Filed: June 29, 2011
    Date of Patent: July 22, 2014
    Assignee: Infinera Corporation
    Inventor: Gilad Goldfarb
  • Patent number: 8787776
    Abstract: An optical receiver includes a photodetector for detecting incoming optical data signals and an amplifier for providing signal gain and current to voltage conversion. The detection signal generated by the photodetector may include a distortion component caused by an operating characteristic of the photodetector. A signal compensating circuit may reconstruct the received optical data signal by effectively canceling the distortion component. For this purpose, the signal compensating circuit may include a decision feedback equalizer implemented using at least one feedback filter matched to the operating characteristic of the photodetector causing the signal distortion so as to reproduce the distortion component for cancellation. Use of a control module may also configure the optical receiver in real time to account for other operating and environmental conditions of the optical receiver.
    Type: Grant
    Filed: June 3, 2011
    Date of Patent: July 22, 2014
    Assignee: The Governing Council of the University of Toronto
    Inventors: Anthony Chan Carusone, Tony Shuo-Chun Kao, Hemesh Yasotharan
  • Patent number: 8774645
    Abstract: Method and apparatus for controlling bias point of DQPSK demodulator are disclosed. The method comprises: step 1: respectively applying first and second bias voltages to I-path and Q-path, and applying identical pilot voltage signals to I-path and Q-path (S202); step 2: executing filtering processing on I-path and Q-path differential current signals collected by balance receiver and determining ?Iand ?Q (S204); step 3: performing feedback control to first and second bias voltages respectively according to ?I and ?Q so that ?I and ?Q respectively reaches expected bias point values of I-path and Q-path (S206); executing step 2 and 3 cyclically at preset regular intervals (S208), so that ?I and ?Q remains consistently the expected bias point values of I-path and Q-path. The solution enables bias point of DQPSK demodulator to be locked at any expected bias point value, facilitates realization of digitization, and is not easily influenced.
    Type: Grant
    Filed: August 20, 2010
    Date of Patent: July 8, 2014
    Assignee: ZTE Corporation
    Inventors: Jianhua Chen, Hong Yi
  • Patent number: 8768178
    Abstract: Feed-forward and feedback strategies are used to control local oscillator power and transimpedance amplifier gain in a high-speed coherent optical receiver.
    Type: Grant
    Filed: September 15, 2011
    Date of Patent: July 1, 2014
    Assignee: Opnext Subsystems, Inc.
    Inventors: Sunil Kumar Singh Khatana, George Zarris
  • Patent number: 8744279
    Abstract: Polarization mode dispersion (PMD) in a dual-pole optical communications network is compensated for using an adaptive PMD equalizer. The PMD equalizer may include a number of substantially identical filter modules that provide partial outputs which may be combined to form a PMD compensated output. A constant modulus algorithm (CMA)-based equalizer may track PMD across both poles and generates an error signal. The CMA-based equalizer includes a filter bank, and uses an update algorithm and tap/output adjustments based on a difference between combined tap energies and an index, and feedback from a forward error correction code frame synchronizer.
    Type: Grant
    Filed: August 8, 2011
    Date of Patent: June 3, 2014
    Assignee: ViaSat, Inc.
    Inventors: Fan Mo, Sameep Dave, Lawrence W. Esker
  • Patent number: 8744276
    Abstract: An optical receiving apparatus includes a combining unit that combines signal light and reference light; a optoelectric converting unit that converts, into electrical signals, two or more optical signals that enable reconstruction of a complex electric field signal of the signal light obtained by the combining unit; and a sampling clock generating unit that generates a sampling clock that has a frequency preset based on a symbol rate of the signal light and is asynchronous with the signal light. The optical receiving apparatus further includes a digital converting unit that samples at the frequency of the sampling clock signal, an electrical signal obtained by the optoelectric converting unit and converts the electrical signal into a digital signal; and a digital signal processing unit that demodulates a received signal based on a complex digital signal obtained from the digital signal obtained by the digital converting unit.
    Type: Grant
    Filed: March 20, 2009
    Date of Patent: June 3, 2014
    Assignee: Fujitsu Limited
    Inventors: Hisao Nakashima, Takeshi Hoshida, Takahito Tanimura, Lei Li, Ling Liu
  • Patent number: 8737847
    Abstract: An apparatus and method for performing joint equalization and timing recovery in coherent optical systems. The method includes equalizing signals to generate compensated polarization signals, wherein timing error in a distorted optical signal is calculated based on one of the compensated polarization signals. The method further includes performing resampling polarization signals to correct timing offset in an optical signal based on the calculated timing error. The calculated timing error may also be used to adaptively control one or more operating parameters of an external device.
    Type: Grant
    Filed: March 19, 2012
    Date of Patent: May 27, 2014
    Assignee: Futurewei Technologies, Inc.
    Inventors: Chuandong Li, Zhuhong Zhang, Fei Zhu, Yu Sheng Bai
  • Patent number: 8705985
    Abstract: A method and an optical receiver implementing this method suitable for robustly receiving unencoded optical data. The method sets the threshold for the receiver using values relating to the high and low values of a binary signal. However, for some data patterns these values may not be accurately determined, such as for extended periods of constant high or low values being transmitted. In this case the method, in one embodiment, assumes that the extinction ratio of the signal is substantially constant and is thereby able to track the threshold for the signal.
    Type: Grant
    Filed: June 2, 2011
    Date of Patent: April 22, 2014
    Assignee: Mellanox Technologies Denmark APS
    Inventor: Steen Bak Christensen
  • Patent number: 8693898
    Abstract: 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: Grant
    Filed: October 14, 2011
    Date of Patent: April 8, 2014
    Assignee: Fujitsu Limited
    Inventors: Nobukazu Koizumi, Kazuhiko Hatae, Noriyasu Nakayama, Koji Nakamuta, Hisao Nakashima, Kosuke Komaki
  • Patent number: 8693881
    Abstract: An optical heterodyne device includes an optical meta-material exhibiting non-linear behavior. The optical meta-material mixes an input signal and a local signal to produce a heterodyne signal.
    Type: Grant
    Filed: November 19, 2010
    Date of Patent: April 8, 2014
    Assignee: Hewlett-Packard Development Company, L.P.
    Inventors: Wei Wu, Shih-Yuan (SY) Wang, Alexandre M. Bratkovski
  • Patent number: 8670678
    Abstract: 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: Grant
    Filed: February 24, 2011
    Date of Patent: March 11, 2014
    Assignee: Fujitsu Limited
    Inventors: Yuichirou Sakamoto, Kosuke Komaki
  • Patent number: 8669512
    Abstract: A system for measuring one or more characteristics of light of a photon energy Eph from a light source, that can be determined from measuring three-photon absorption events, the system comprising: a) a detector having a band gap material characterized by gap energy between 2.1 and 3 times Eph; b) an optical element configured to concentrate a beam of light from the light source on the detector; c) a signal amplifier that amplifies an output signal indicative of when three photons produced by the light source undergo a three-photon absorption event in the band gap material; and d) an analyzer that analyzes the output signal to count or measure a rate of the three-photon absorption events, and determines the one or more characteristics of the light from the light source.
    Type: Grant
    Filed: December 28, 2011
    Date of Patent: March 11, 2014
    Assignee: Technion Research & Development Foundation Limited
    Inventors: Amir Nevet, Alex Hayat, Meir Orenstein
  • Patent number: 8666251
    Abstract: The invention provides a system and method, for an optical communication network to compensate impairments in the network, using electronic dispersion compensation, said system comprising optical means comprising two or more optical-to-electrical converters for generating at least two electrical signals, comprising amplitude and instantaneous frequency of a received distorted optical signal, and an electrical circuit adapted to perform a full-field reconstruction of the received distorted optical signal using said electrical signals. The system is characterised by a dispersive transmission line circuit with compensation parameters updated at a selected rate to process said full-field reconstructed signal and compensate for coarse chromatic dispersion; and an adaptive electronic equalization circuit with compensation parameters updated at a rate faster than those in the said dispersive transmission line circuit to provide a fine impairment compensation of said reconstructed signals.
    Type: Grant
    Filed: June 23, 2010
    Date of Patent: March 4, 2014
    Assignee: University College Cork—National University of Ireland Cork
    Inventors: Jian Zhao, Mary McCarthy
  • Patent number: 8649690
    Abstract: A system configured to maintain a consistent local-oscillator-power-to-primary-signal-power ratio (LO/SIG ratio).
    Type: Grant
    Filed: May 30, 2012
    Date of Patent: February 11, 2014
    Assignee: Cisco Technology, Inc.
    Inventors: Soren Gehrke, Theodor Kupfer, James Whiteaway
  • Patent number: 8649689
    Abstract: A digital coherent receiving apparatus includes a first oscillator for outputting a local light signal of a fixed frequency, a hybrid unit mixing the local light signal with a light signal received by a receiver, a second oscillator for outputting a sampling signal of a sampling frequency, a converter for converting the mixed light signal into digital signal synchronizing with the sampling signal, a waveform adjuster for adjusting a waveform distortion of the converted digital signal, a phase adjustor for adjusting a phase of the digital signal adjusted by the waveform adjustor, a demodulator for demodulating the digital signal adjusted by the phase adjuster, and a phase detector for detecting a phase of the digital signal adjusted by the phase adjuster, and a control signal output unit for outputting a frequency control signal on the basis of the detected phase signal to the second oscillator.
    Type: Grant
    Filed: June 22, 2010
    Date of Patent: February 11, 2014
    Assignee: Fujitsu Limited
    Inventors: Nobukazu Koizumi, Takeshi Hoshida, Takahito Tanimura, Hisao Nakashima, Koji Nakamuta, Noriyasu Nakayama
  • Patent number: 8611763
    Abstract: A method (10) of compensating phase noise in a coherent optical communications network. The method comprises: receiving a traffic sample (12); receiving an optical carrier and determining a phase noise estimate for the optical carrier (14); and removing the phase noise estimate from the traffic sample to form a phase noise compensated traffic sample (16).
    Type: Grant
    Filed: September 2, 2010
    Date of Patent: December 17, 2013
    Assignee: Telefonaktiebolaget L M Ericsson (publ)
    Inventors: Marco Secondini, Tommaso Foggi, Giulio Colavolpe, Gianluca Meloni, Luca Poti, Enrico Forestieri
  • Patent number: 8582979
    Abstract: From an real valued OFDM signal (S0(t)) is a baseband signal (SB(t)) derived and converted into a complex single sideband modulation signal (n(t)). This is modulated onto an optical carrier (fOC) to generate a SSB transmission signal (SOT) having a small bandwidth an carrying the information in the envelope or in the power of the envelope. According to the modulation direct detection is possible. Only a small bandwidth is necessary for the transmission.
    Type: Grant
    Filed: August 18, 2008
    Date of Patent: November 12, 2013
    Assignee: Nokia Siemens Networks OY
    Inventors: Christian Alexander Bunge, Matthias Schuster, Bernhard Spinnler
  • Patent number: 8577225
    Abstract: Provided is an optical receiver which accurately demodulates an optical signal obtained by the differential phase shift modulation method. The optical receiver includes: an interferometer which branches the inputted optical signal into two parts and gives a one-bit phase difference to the resultant two optical signals so that the two optical signals after addition of the phase difference are made to interfere each other to output two output lights; reflection means which reflects one of the output lights from the interferometer so as to return to the interferometer; detection means which detects the return light which has been reflected by the reflection means and propagates through the interferometer in the different direction from the inputted optical signal, for output; and phase difference control means which adjusts the phase difference given by the interferometer according to the intensity of the return light detected by the detection means.
    Type: Grant
    Filed: March 25, 2009
    Date of Patent: November 5, 2013
    Assignee: Sumitomo Osaka Cement Co., Ltd.
    Inventors: Masahito Mure, Norikazu Miyazaki, Toshio Kataoka, Kaoru Higuma
  • Patent number: 8565621
    Abstract: A method for detecting and measuring time skew in high-speed DP-QPSK coherent optical receivers is described.
    Type: Grant
    Filed: September 23, 2011
    Date of Patent: October 22, 2013
    Assignee: Opnext Subsystems, Inc.
    Inventors: Edem Ibragimov, Sunil Kumar Singh Khatana
  • Patent number: 8538271
    Abstract: An apparatus comprising an optical receiver configured to receive an optical signal, and a combined level and clock recovery circuit coupled to the optical receiver and configured to update a signal threshold and a clock phase substantially simultaneously. Also included is an apparatus comprising at least one processor configured to implement a method comprising recognizing reception of a signal, and adjusting a threshold and a clock phase associated with the signal using a rising time for the signal and a falling time for the signal. Also included is a method comprising receiving a signal, and adjusting a threshold level of the signal to establish level recovery using a clock recovery scheme.
    Type: Grant
    Filed: November 23, 2009
    Date of Patent: September 17, 2013
    Assignee: Futurewei Technologies, Inc.
    Inventor: Frank J. Effenberger
  • Patent number: 8532502
    Abstract: In present invention, a filter coefficient adjustment apparatus is used in a polarization demultiplexer which demultiplexes the input signals by using filters to obtain demultiplexed output signals, said filter coefficient adjustment apparatus being used for adjusting the coefficients of the filters, wherein said filter coefficient adjustment apparatus comprises: an logarithm partial derivative calculation unit for calculating the logarithm partial derivative value of a target probability density function of the demultiplexed output signals when its self-variable value is the present demultiplexed output signal value; a gradient calculation unit for calculating the gradient of a target optimizing function for optimizing the distribution of the multiplexed output signals based on the logarithm partial derivative value calculated by the logarithm partial derivative calculation unit; and a filter coefficient updating unit for updating the coefficients of the filters based on the gradient calculated by the gradie
    Type: Grant
    Filed: June 5, 2009
    Date of Patent: September 10, 2013
    Assignee: Fujitsu Limited
    Inventors: Huijian Zhang, Zhenning Tao, Takahito Tanimura
  • Patent number: 8478137
    Abstract: 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: Grant
    Filed: January 31, 2011
    Date of Patent: July 2, 2013
    Assignee: Fujitsu Limited
    Inventors: Kosuke Komaki, Masahiro Shioda, Katsumi Fukumitsu, Osamu Takeuchi
  • Patent number: 8472812
    Abstract: Transmission-side communication apparatus 100 using a DQPSK (differential quadrature phase-shift keying) scheme is provided with: optical carrier generation section 102 which generates an optical carrier the frequency of which switches among a plurality of different frequencies within one symbol period; and modulation section 103 with which DQPSK-modulates the optical carrier generated by the optical carrier generation means in accordance with a modulation signal at an interval of the symbol period. There are provided: single delay interference section 121 which receives an optical signal obtained by DQPSK-modulating an optical carrier the frequency of which switches among a plurality of different frequencies within one symbol period and outputs an output light obtained by causing the optical signal 104 and a delay optical signal thereof to interfere with each other; and photoelectric conversion section 124 which converts the output light outputted by the delay interference means to an electric signal.
    Type: Grant
    Filed: February 18, 2009
    Date of Patent: June 25, 2013
    Assignee: NEC Corporation
    Inventors: Satomi Shioiri, Toshiharu Ito, Kiyoshi Fukuchi
  • Patent number: 8472813
    Abstract: A polarization-multiplexed (POLMUX) optical orthogonal frequency division multiplexing (OFDM) system with direct detection includes an adaptive dual POLMUX carrier OFDM transmitter; and a block symmetric (B-S) MIMO equalizer coupled to the adaptive dual POLMUX carrier OFDM transmitter through a standard single-mode-fiber (SSMF) feedback path.
    Type: Grant
    Filed: June 18, 2010
    Date of Patent: June 25, 2013
    Assignee: NEC Laboratories America, Inc.
    Inventors: Neda Cvijetic, Narayan Prasad, Dayou Qian, Ting Wang
  • Patent number: 8463140
    Abstract: A reception device includes at least a light receiving unit, a phase calculation unit, and a demodulation unit. The light receiving unit receives intensity-modulated light from a transmission device. The transmission device executes phase modulation to a bit stream as an object to be transmitted and emits the intensity-modulated light which has an intensity changing at a preset time cycle and a phase changing in response to the phase modulation, and the phase is maintained during M cycles. The phase calculation unit detects the intensity of the intensity-modulated light p times per cycle of the intensity-modulated light and repeatedly calculates the phase of the intensity-modulated light on the basis of a result of the detection. The demodulation unit executes demodulation, which corresponds to the phase modulation, to the phase calculated by the phase calculation unit, and generates transmitted bit stream.
    Type: Grant
    Filed: February 18, 2010
    Date of Patent: June 11, 2013
    Assignee: Honda Motor Co., Ltd.
    Inventor: Chiaki Aoyama
  • Patent number: 8463141
    Abstract: A digital version of both amplitude and phase of at least one generic polarization component of a received optical signal is developed using dual-polarization direct differential detection with digital signal processing. The received signal is split into orthogonal polarization components, each of which is split into three copies. For each orthogonal polarization component a) an intensity profile is conventionally obtained using a copy and b) phase information is obtained by supplying each remaining copy to a respective one of a pair of optical delay interferometers having orthogonal phase offsets, followed by respective balanced intensity detectors. The outputs the balanced intensity detectors and the intensity profiles are converted into digital representations and used to develop, via signal processing, the optical field information of at least one generic polarization component of the received optical signal. Compensation of impairments, such as PMD, is realized through further processing.
    Type: Grant
    Filed: December 14, 2007
    Date of Patent: June 11, 2013
    Assignee: Alcatel Lucent
    Inventor: Xiang Liu
  • Patent number: 8447190
    Abstract: A distortion compensating apparatus which compensates for distortion in a waveform of a received light signal through a digital signal processing includes a plurality of fixed amount compensators which compensate for the distortion in the waveform at respective given compensating amounts. The combination of operating states of the plurality of fixed amount compensators is changed by on/off switching of each of the plurality of fixed amount compensators, and the plurality of fixed amount compensators are cascaded.
    Type: Grant
    Filed: January 29, 2010
    Date of Patent: May 21, 2013
    Assignee: Fujitsu Limited
    Inventors: Takahito Tanimura, Takeshi Hoshida, Hisao Nakashima, Kazunari Shiota, Kiichi Sugitani
  • Patent number: 8406635
    Abstract: An optical receiver for receiving an optical signal that transmits a first data signal and a second data signal, including: an optical front-end configured to generate a digital signal that represents the optical signal; a detector configured to detect a state of the optical signal by using the digital signal and output state information that represents the state of the optical signal; a state controller configured to control the digital signal on the basis of the state information in order to recover the first data signal; and a data recovery configured to recover the second data signal on the basis of the state information.
    Type: Grant
    Filed: November 16, 2009
    Date of Patent: March 26, 2013
    Assignee: Fujitsu Limited
    Inventors: Hisao Nakashima, Takeshi Hoshida
  • Patent number: 8396375
    Abstract: A method for enabling bidirectional data communication using a single optical carrier and a single laser source with the aid of an integrated, colorless demodulator and detector for frequency modulated signals, and a reflective modulator. A receiving optical system holds a technique for demodulation and detection of optical frequency modulated signals, enabling remodulation of the incoming signal to establish bidirectional communication with the transmitting optical system, without introducing a high penalty. A colorless demodulator and detector, which provides the functionality of a periodic filtering device for demodulation of the downstream, and also detection capability. The principle of operation of the CDD relies on the introduction of a comb transfer function with the help of a Semiconductor Optical Amplifier, by providing a reflected feedback signal to the CDD's active element.
    Type: Grant
    Filed: February 18, 2010
    Date of Patent: March 12, 2013
    Assignee: Universitat Politecnica de Catalunya
    Inventors: Bernhard Schrenk, José Antonio Lázaro Villa, Christophe Kazmierski, Josep Joan Prat Gomà
  • Patent number: 8385747
    Abstract: A signal equalizer for compensating impairments of an optical signal received through a link of a high speed optical communications network. At least one set of compensation vectors are computed for compensating at least two distinct types of impairments. A frequency domain processor is coupled to receive respective raw multi-bit in-phase (I) and quadrature (Q) sample streams of each received polarization of the optical signal. The frequency domain processor operates to digitally process the multi-bit sample streams, using the compensation vectors, to generate multi-bit estimates of symbols modulated onto each transmitted polarization of the optical signal. The frequency domain processor exhibits respective different responses to each one of the at least two distinct types of impairments.
    Type: Grant
    Filed: June 15, 2011
    Date of Patent: February 26, 2013
    Assignee: Ciena Corporation
    Inventors: Kim B. Roberts, Han Sun
  • Patent number: 8340534
    Abstract: A method comprising generating a plurality of first symbols that correspond to a side band pilot tone (SBPT) signal for a plurality of data streams, mapping the first symbols into a plurality of second symbols that correspond to a plurality of signal components of the polarization multiplexed (PM) optical signal, and transmitting the second symbols in a plurality of data blocks of a PM optical signal. An apparatus comprising at least one processor coupled to a memory and configured to obtain a data block that comprises a plurality of SBPTs in a received PM optical signal, estimate a set of values for a carrier frequency and a polarization state, update a tap weight of a master equalizer based on the estimated set of values, and update a plurality of slave equalizers based on the updated tap weight of the master equalizer.
    Type: Grant
    Filed: July 30, 2010
    Date of Patent: December 25, 2012
    Assignee: Futurewei Technologies, Inc.
    Inventors: Zhuhong Zhang, Chuandong Li, Fei Zhu, Yusheng Bai
  • Patent number: 8335438
    Abstract: According to particular embodiments, a signal communicated from a transmitter to a receiver is received. A frequency offset estimate of the signal is determined. The frequency offset estimate indicates a frequency difference between the transmitter and the receiver. The frequency offset estimate is provided as feedback. A next frequency offset is compensated for according to the feedback.
    Type: Grant
    Filed: October 30, 2009
    Date of Patent: December 18, 2012
    Assignee: Fujitsu Limited
    Inventors: Inwoong Kim, Takao Naito
  • Patent number: 8331803
    Abstract: An apparatus comprising a plurality of receivers each configured to receive a plurality of polarized signals, a voltage control oscillator (VCO) coupled to the receivers and configured to control timing and sampling frequency of the polarized signals, and a signal processing component coupled to the receivers and configured to update a plurality of weighted linear factors, wherein the polarized signals and the weighted linear factors are used to obtain a combined signal, and wherein the weighted linear factors are updated using a real part or an imaginary part of the combined signal. Included is a method comprising using a linear factor to combine a plurality of polarized optical signals to provide time recovery information, and updating the linear factor using a combination of the polarized optical signals.
    Type: Grant
    Filed: October 7, 2009
    Date of Patent: December 11, 2012
    Assignee: Futurewei Technologies, Inc.
    Inventors: Chuandong Li, Zhuhong Zhang
  • Patent number: 8326160
    Abstract: A dispersion compensation device includes: an optical branching unit to branch an optical signal to be received; a first dispersion compensator to perform dispersion compensation on one part of the optical signal branched by the optical branching unit with a variable compensation amount; a second dispersion compensator to perform dispersion compensation on another part of the optical signal branched by the optical branching unit; a monitoring unit to monitor the communication quality of an output optical signal of the second dispersion compensator; and a controlling unit to determine the direction of variation in chromatic dispersion of the optical signal based on the direction of variation in communication quality monitored by the monitoring unit and control the compensation amount of the first dispersion compensator based on the result of the determination.
    Type: Grant
    Filed: November 22, 2010
    Date of Patent: December 4, 2012
    Assignee: Fujitsu Limited
    Inventors: Makoto Murakami, Toshihiro Ohtani