Abstract: An apparatus which transmits data and control information which indicates at least one of a demodulation method and a decoding method of the data using an optical signal, includes: a modulator configured to perform modulation in which a rate of change of a polarization state of light is changed according to the control information, and modulation in which a characteristic of light which is different from the rate of change of the polarization state is changed in accordance with the data; and an emitting section configured to emit light, on which modulation is performed using the modulator, to another communication apparatus via a free space.

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 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 includes a circuit that controls a first frequency component and a second frequency component that are contained in an optical signal to be transmitted to be in different polarization states from each other.

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 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 power monitor that detects optical power of respective wavelengths of a signal light in a wavelength multiplexing system, includes: a light emitter configured to superimpose a frequency modulation component on a signal light; a wavelength tunable filter configured to sweep a pass band of the signal light across a wavelength band for a signal light; and a detector configured to detect intensity changes in optical power passing through the wavelength tunable filter with a frequency modulation of the optical power, and to detect an optical power measurement value at a middle point of two points of the intensity changes of the optical power as the optical power of a wavelength to be measured.

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 digital coherent receiver includes: a polarization separation circuit configured to perform polarization separation on a received signal and output polarized signals; and a determination circuit configured to trigger a start of digital signal processing in a stage subsequent to the polarization separation circuit when it is determined that a distribution of a peak of an amplitude of one of the polarized signals has a characteristic corresponding to a modulation method used on a transmitting side.

Abstract: A signal processing device includes: a phase controller configured to control respective phases of an in-phase signal and an quadrature signal, which are obtained by converting an analog signal into a digital signal when a multi-value phase modulation light is demodulated, by digital signal processing; and a control amount provider configured to provide a control amount to the phase controller based on an output of the phase controller.

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.

Abstract: Light output from a seed light source generation unit that outputs continuous light having a single frequency or a plurality of frequencies is input by a multi-wavelength light source to an optical circulation unit, and light having a plurality of frequencies that is frequency-synchronized with seed light output from the seed light source generation unit is generated. The optical circulation unit is provided with an optical frequency shifter to shift light frequencies, and includes a circulation circuit to return output from the optical frequency shifter to the input side. On a circulation path, an optical spectral shaper capable of adjusting an optical amount of attenuation for each frequency unit is provided so that optical amount of attenuations are adjusted, and thereby the number and the like of optical frequencies output from the optical circulation unit are changed.

Abstract: A distortion compensator, an optical receiver and a transmission system including an operation selectively compensating for linear waveform distortion exerted on an optical signal via a plurality of distortion compensators and compensating for nonlinear waveform distortion exerted on the optical signal using nonlinear distortion compensators.

Abstract: The present invention relates to chromatic dispersion monitor and method, chromatic dispersion compensator. The chromatic dispersion monitor is used for estimating a chromatic dispersion in accordance with a chromatic dispersion correlation amount sequence, comprising: a phase differential unit, for obtaining a phase difference sequence by performing a phase differential calculation in accordance with the chromatic dispersion correlation amount sequence; a phase difference differential unit, for obtaining a phase difference differential sequence by performing a phase difference differential operation; and a chromatic dispersion estimating unit, for estimating the chromatic dispersion in accordance with the phase difference differential sequence obtained by the phase difference differential unit.

Abstract: An adaptive equalizer and an adaptive equalizing method are provided. The adaptive equalizer includes an adaptive equalizing unit, for adaptively equalizing an inputted signal to output the equalized signal; a coefficient updating unit, for updating a coefficient of a filter of the adaptive equalizing unit; a switching unit, connected between the coefficient updating unit and the adaptive equalizing unit and a monitoring device, for controlling on or off of the switching unit in accordance with the fact that a down sampling phase of the inputted signal or a down sampling phase of the equalized signal is within a predetermined range. When the switching unit is on, the coefficient updating unit is capable of updating the coefficient of the adaptive equalizing unit, and when the switching unit is off, the coefficient updating unit is incapable of updating the coefficient of the adaptive equalizing unit.

Abstract: An optical receiver includes: a first generator to generate, from an optical signal to which a reference signal is inserted, a first digital signal representing a signal component of a first partial band including the reference signal, using a first local oscillation light of a first frequency; a second generator to generate, from the optical signal, a second digital signal representing a signal component of a second partial band including the reference signal, using a second local oscillation light of a second frequency being different from the first frequency; a frequency compensator to adjust a frequency of the signal component of the first partial band and a frequency of the signal component of the second partial band according to a frequency of the reference signal; and a combiner to combine the first and second partial bands adjusted by the frequency compensator.

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.

Abstract: In a digital signal processing circuit of an optical receiver applicable to this method for electric power supply control, tap coefficients of a filter used in a waveform equalization section are calculated in a tap coefficient calculating section, based on a state of an optical fiber transmission line. Then, among the calculated tap coefficients, a tap coefficient for which an absolute value is less than a previously determined threshold is determined, and electric power supply to a circuit part of a filter corresponding to the tap coefficient is stopped. As a result, for an optical receiver that performs digital signal processing, it is possible to reduce the power consumption, while realizing waveform equalization at a high accuracy.

Abstract: An optical digital coherent receiver includes: a polarization separation circuit configured to perform polarization separation on a received signal and output polarized signals; and a determination circuit configured to trigger a start of digital signal processing in a stage subsequent to the polarization separation circuit when it is determined that a distribution of a peak of an amplitude of one of the polarized signals has a characteristic corresponding to a modulation method used on a transmitting side.