Abstract: An optical receiving device includes: an adaptive equalizer that includes a position estimation unit configured to estimate, based on a first signal component and a second signal component of a reception signal generated by reception of a training sequence pattern transmitted from an optical transmitter, a symbol position of the reception signal, and generates an estimated symbol position, a delay unit configured to provide a delay difference between the first signal component and the second signal component, a control unit configured to set a plurality of symbol displacement amount candidates of displacement amounts for the estimated symbol position, causes the delay unit to generate a plurality of delay differences, and generates a channel estimation symbol position used for channel estimation, and an error rate calculation unit configured to calculate an error rate of the signal restored by an adaptive equalization unit.

Abstract: A non-linear distortion compensator includes: a non-linear distortion calculator that calculates non-linear distortion occurred in a received optical signal based on signal information after recovery of a carrier wave in a carrier wave phase recovery which recovers a phase of the carrier wave of the received optical signal; and a non-linear compensator that compensates the non-linear distortion of the received optical signal based on the non-linear distortion obtained by the non-linear distortion calculator.

Abstract: An optical transmitter includes: a mapper configured to generate an electric-field-information signal from transmission data; a training-signal-generation section configured to generate a training signal; a training-signal-insertion section configured to insert the training signal into the electric-field-information signal; a driver configured to generate a drive signal from the electric-field-information signal into which the training signal is inserted; a modulator configured to generate an optical-modulation signal based on the drive signal; an optical receiver configured to generate an intensity signal indicating intensity of the optical-modulation signal; a training-signal-extraction section configured to extract an intensity-training signal corresponding to the training signal, from the intensity signal; a coder configured to generate a coded-training signal by coding the intensity-training signal extracted by the training-signal-extraction section using the training signal generated by the training-sig

Abstract: An optical receiver includes a dividing unit, a control unit, and a compensating unit. The dividing unit divides an optical transmission signal into a plurality of frequency components by a set number of divisions and a set division bandwidth. The control unit controls the number of divisions and the division bandwidth on the basis of transmission path information about an optical transmission line through which the optical transmission signal is transmitted and signal information about the optical transmission signal. The compensating unit compensates optical nonlinear distortion of each of the frequency components divided by the dividing unit.

Abstract: An optical transmitter includes: a mapper that generates an electric field information signal from transmission data; a phase rotation circuit that adds a phase rotation to the electric field information signal; a driver that generates a driving signal from the electric field information signal to which the phase rotation is added; a modulator that generates a modulated optical signal according to the driving signal; and a controller that controls a bias of the modulator according to a change in a carrier frequency of the modulated optical signal corresponding to the phase rotation that is added to the electric field information signal by the phase rotation circuit.

Abstract: An optical transmission system includes optical transmission apparatuses configured to transmit wavelength-division multiplexed light signals via lightpaths, each of a pair of optical transmission apparatuses includes a conditioning unit configured to adjust the optical intensities of channels included in the wavelength-division multiplexed light signal, and one or more first processors configured to control, based on a conditioning level notified, the conditioning unit; and a managing apparatus configured to manage the pair of the optical transmission apparatuses, the managing apparatus including one or more second processors configured to compute a conditioning level on a basis of system information for respective the pair of optical transmission apparatuses in the optical transmission system.

Abstract: An optical transmitter transmits optical signal including a first signal and a second signal. The second signal is subjected to change in a polarization state relative to a polarization state of the first signal. An optical receiver analyzes a reception characteristic of the second signal and detects, based on the analyzed result, a polarization state of the first signal indicative of a higher signal quality than that of the second signal.

Abstract: An optical transmission system includes: a plurality of transmitters that output an optical signal having a frequency different from each other; a process unit that adds a reference signal to at least two of the optical signals, the reference signal having a frequency width narrower than that of the two optical signals, an interval of central frequencies of the reference signals being narrower than that of the two optical signals, a multiplexer that multiplexes optical signals output by the plurality of transmitters; an extract unit that extracts a beat signal generated between the reference signals because of a multiplexing of the multiplexer; and an adjust unit that adjusts a frequency interval of the two optical signals in accordance with an extract result of the extract unit.

Abstract: An optical transmission apparatus includes transmitters configured to correspond to the polarization multiplexing optical signals, each of at least two of the transmitters including a first computing unit that computes, based on information regarding an optical transmission line including a plurality of spans and a polarization multiplexing optical signal, data waveform information regarding the transmitter and transmits the data waveform information to at least one another transmitter provided for at least one another polarization multiplexing optical signal, and a second computing unit that receives data waveform information from the at least one another transmitter provided for the at least one another polarization multiplexing optical signal and pre-equalizes or reduces cross phase modulation occurring in the optical transmission line of a transmission signal based on the data waveform information received from the at least one another transmitter provided for the at least one another polarization multipl

Abstract: An optical receiving device includes: an adaptive equalizer that includes a position estimation unit configured to estimate, based on a first signal component and a second signal component of a reception signal generated by reception of a training sequence pattern transmitted from an optical transmitter, a symbol position of the reception signal, and generates an estimated symbol position, a delay unit configured to provide a delay difference between the first signal component and the second signal component, a control unit configured to set a plurality of symbol displacement amount candidates of displacement amounts for the estimated symbol position, causes the delay unit to generate a plurality of delay differences, and generates a channel estimation symbol position used for channel estimation, and an error rate calculation unit configured to calculate an error rate of the signal restored by an adaptive equalization unit.

Abstract: A signal processing circuit includes: a first compensator configured to compensate for waveform distortion corresponding to chromatic dispersion of a received optical signal by using digital electrical signals obtained by sampling analog electrical signals by using a sampling signal, the analog electrical signals being obtained by opto-electric conversion of multiple optical signals that include an intensity of the received optical signal and phase information thereon; and a chromatic dispersion compensation controller configured to control a compensation value for the chromatic dispersion in the first compensation from the digital electrical signals in which the chromatic dispersion has been compensated for on the basis of a detected phase offset between the sampling signal and a modulation frequency of the received optical signal.

Abstract: A method includes sweeping an optical frequency of an optical signal by an optical transmitter controlling an electric-field information signal corresponding to a transmitted signal, providing different polarization states for individual frequencies of the optical signal by the optical transmitter controlling a mixture of a first electric-field information signal corresponding to a first transmitted signal and a second electric-field information signal corresponding to a second transmitted signal, obtaining, for individual frequencies of the optical signal, polarization dependent characteristics corresponding to different frequencies, when the optical transmitter sweeps the frequency of the optical signal, by an optical receiver calculating a polarization-dependent characteristic of an optical transmission line between the optical transmitter and the optical receiver, based on items of received-electric-field information corresponding to the different polarization states, and obtaining statistical information

Abstract: In a sampling clock synchronizing apparatus, an A/D converter converts an analog signal to a digital signal based on a sampling clock, and a processor compensates a band limitation due to spectral narrowing by filter characteristics of characteristics opposite to those of the spectral narrowing with respect to a signal produced from the A/D converter subjected to the spectral narrowing, and detects a phase shift in the sampling clock based on a signal after the compensation of the spectral narrowing and synchronizes sampling timing.

Abstract: A receiving device that converts, to a digital signal, a signal in which signal light from an optical transmission path and local oscillation light are mixed, so as to perform digital signal processing, the optical communication receiving device comprising: a frequency offset compensation unit configured to calculate a frequency offset of the digital signal and to, based on the frequency offset, compensate for a phase of the digital signal; a carrier phase recovery unit configured to calculate a carrier phase of the digital signal whose phase is compensated for in the frequency offset compensation unit; and a residual frequency offset detection unit configured to calculate an average of differences in the carrier phase, and to output the average as a residual frequency offset, wherein the frequency offset compensation unit is configured to correct the frequency offset using the residual frequency offset output by the residual frequency offset detection unit.

Abstract: An optical node apparatus that establishes an optical path between a first optical node and a second optical node in an optical network include a frequency modulation unit that superimposes a supervisory signal on a main signal by frequency-modulating the main signal, and a frequency demodulation unit that frequency-demodulates the supervisory signal superimposed on the received main signal.

Abstract: A non-linear distortion compensator includes: a first signal generator configured to generate a signal with a second multivalued level lower than a first multivalued level from an input signal; a non-linear distortion calculator configured to calculate non-linear distortion of the signal with the first multivalued level based on the signal with the second multivalued level generated by the first signal generator; and a non-linear compensator configured to compensate the non-linear distortion of the signal with the first multivalued level based on the non-linear distortion calculated by the non-linear distortion calculator.

Abstract: A non-linear distortion compensator includes: a non-linear distortion calculator that calculates non-linear distortion occurred in a received optical signal based on signal information after recovery of a carrier wave in a carrier wave phase recovery which recovers a phase of the carrier wave of the received optical signal; and a non-linear compensator that compensates the non-linear distortion of the received optical signal based on the non-linear distortion obtained by the non-linear distortion calculator.

Abstract: A light receiving device includes: a converter digitalizing an analog signal with a given sampling clock frequency, the analog signal being obtained through a photoelectric conversion of a received optical signal; a plurality of fixed distortion compensators compensating an output signal of the converter for waveform distortion with a fixed compensation amount that is different from each other; a plurality of phase shift detector circuits detecting a sampling phase shift from an output signal of the plurality of the fixed distortion compensators; a phase-adjusting-amount determiner determining a sampling phase adjusting amount with use of an output signal of the plurality of the phase shift detector circuits; and a phase adjusting circuit reducing a phase difference between the sampling clock frequency and the received optical signal based on a determination result of the phase-adjusting-amount determiner.

Abstract: An optical transmission/reception system includes a modulator for modulating light based on data to output signal light; a transmission-side signal processor performing transmission-side digital signal processing which imparts a polarization change to the signal light by the optical modulation with respect to an input signal; an optical transmitter in which the modulator performs the optical modulation based on the input signal subjected to the transmission-side digital signal processing in the transmission-side signal processor; and an optical receiver including a converter converting the signal light inputted from the optical transmitter via a transmission path to a digital electric signal for each polarization component, and a reception-side signal processor performing reception-side digital signal processing which imparts a polarization change having a property substantially inverse to a property of the polarization change in the transmission-side signal processor with respect to the digital electric sign

Abstract: An optical transmission system includes an optical transmitter and an optical receiver. The optical transmitter includes: a first digital signal processor configured to generate an electric-field information signal corresponding to a transmission signal; and a transmitter front-end configured to generate an optical signal from the electric-field information signal. The optical receiver includes: a receiver front-end configured to generate an electric signal corresponding to the optical signal; and a second digital signal processor configured to detect polarization dependent effects on the optical signal based on the electric signal. The first digital signal processor corrects the electric-field information signal based on the polarization dependent effects detected by the second digital signal processor in the optical receiver.