Abstract: An adaptive equalizer includes a sample buffer that temporarily stores data obtained by fractional sampling at a sampling rate that is larger than one time and smaller than two times a symbol rate; and a processor coupled to the sample buffer and configured to: specify position of a training sequence in the data based on a correlation value between a first set of (f×T) samples and a second set of (f×T) samples following the first set of samples, assuming that the sampling rate is f, and a symbol length of a code pattern included in the training sequence inserted in the data is T, and calculate an initial value of a tap coefficient set to a tap of an adaptive equalization filter based on the specified training sequence, wherein the symbol length is set to be changeable so that f×T is an integer.

Abstract: An adaptive equalizer, includes a sample buffer; and a processor coupled to the sample buffer and configured to: perform an adaptive equalization on data which has been fractionally sampled at a sampling rate higher than once a symbol rate and lower than twice the symbol rate, determine an initial value of a tap coefficient of the adaptive equalizer by using a training sequence inserted in the data, shift, by a predetermined shift amount, a sample point of one pattern from among two consecutive patterns included in the training sequence, specify a position of the training sequence in the data by replacing an original sample value with a sample value at the shifted sample point, and update the initial value of the tap coefficient based on the specified training sequence.

Abstract: There is provided a reception device including a receiver configured to receive a wavelength-multiplexed optical signal so as to generate a wavelength-multiplexed signal, a filter configured to pass through the wavelength-multiplexed signal having a specific wavelength and an adjacent wavelength to the specific wavelength from the wavelength-multiplexed signal, and a processor configured to detect a specific signal having the specific wavelength from the wavelength-multiplexed signal having the passed through wavelengths by the filter, and detect a first supervisory control signal having the specific wavelength and a second supervisory control signal having the adjacent wavelength from the wavelength-multiplexed signal having the passed through wavelengths by the filter.

Abstract: An optical receiver includes, a first converting circuit that converts an optical signal into an electric signal, a plurality of common circuits, each of which has a same circuit configuration and performs a digital signal processing on the electric signal, and a processor that selects and operates one or more common circuits from among the plurality of common circuits according to a transmission method.

Abstract: An optical transceiver includes: a receiver and a processor. The receiver receives a polarization multiplexed optical signal that includes a first polarization signal and a second polarization signal so as to output reception electric-field information that indicates an electric field of the polarization multiplexed optical signal. The processor calculates, according to the reception electric-field information, a variation monitor value that indicates an amount of leakage of signal components between the first polarization signal and the second polarization signal. When the variation monitor value exceeds a specified threshold, the processor analyzes, according to the reception electric-field information, a state of an optical transmission line through which the polarization multiplexed optical signal propagates.

Abstract: A signal processing device includes: a filter configured to perform an adaptive equalization process of a signal, on a basis of a filter coefficient; an updater configured to update the filter coefficient, on a basis of amplitude of the signal and a target value of the amplitude; and a corrector configured to correct the target value, on a basis of the amplitude of the signal.

Abstract: A transmission method includes mapping a data signal to a symbol according to a modulation mode to generate a first electric field signal and a second electric field signal, modulating a light beam based on the first electric field signal and the second electric field signal to generate a first polarized light beam and a second polarized light beam that are orthogonal to each other, multiplexing the first polarized light beam and the second polarized light beam, applying transformation processing of changing each polarization angle of the first polarized light beam and the second polarized light beam to the first electric field signal and the second electric field signal and adding polarization information indicating a change amount caused by the transformation processing for each polarization angle of the first polarized light beam and the second polarized light beam to the first electric field signal and the second electric field signal.

Abstract: Provided is an imbalance compensation device that compensates for an imbalance between an in-phase component and a quadrature-phase component of a signal, the imbalance compensation device including: an extracting unit that extracts a signal component in an upper sideband or a signal component in a lower sideband from the signal; a measuring unit that measures power of the signal component in the upper sideband or the signal component in the lower sideband extracted by the extracting unit; and an adjusting unit that adjusts a parameter related to the imbalance, in accordance with the power measured by the measuring unit.

Abstract: There is provided an optical transmitter including a modulator, a signal generator configured to generate in-phase or anti-phase skew adjustment signals that are identical in amplitude and frequency as signals to be input into an I axis and a Q axis of the modulator, a skew adjuster configured to perform skew adjustment upon the skew adjustment signals, a light source configured to enter light into the modulator, a monitor configured to monitor light that has been modulated using the skew adjustment signals and output from the modulator, a power detector configured to detect power of monitor light, and a controller configured to determine a skew adjustment amount with which average power of the monitor light is at a maximum or minimum value as an optimum skew adjustment value while changing a skew adjustment amount of the skew adjuster.

Abstract: A transmission method includes mapping a data signal to a symbol according to a modulation mode to generate a first electric field signal and a second electric field signal, modulating a light beam based on the first electric field signal and the second electric field signal to generate a first polarized light beam and a second polarized light beam that are orthogonal to each other, multiplexing the first polarized light beam and the second polarized light beam, applying transformation processing of changing each polarization angle of the first polarized light beam and the second polarized light beam to the first electric field signal and the second electric field signal and adding polarization information indicating a change amount caused by the transformation processing for each polarization angle of the first polarized light beam and the second polarized light beam to the first electric field signal and the second electric field signal.

Abstract: A receiving device receives a received signal in which a data signal, modulated by using a phase modulation method, and a pilot signal are time-multiplexed. The receiving device includes a synchronizing circuit that synchronizes the phase of the received signal. The synchronizing circuit extracts a pilot signal from the received signal. The synchronizing circuit estimates a phase error by comparing the extracted pilot signal and a predetermined pattern. The synchronizing circuit conducts phase rotation on constellation points of the received signal in accordance with the reference phase, obtained from the phase error, and the phase in the modulation method related to the received signal. The synchronizing circuit estimates a phase estimate value of the received signal in accordance with the constellation points, on which phase rotation has been conducted. The synchronizing circuit compensates for a phase error of the received signal in accordance with the phase estimate value.

Abstract: A transmission system includes a first transponder including a first I/Q modulator, and a second transponder including a second I/Q modulator, and configured to communicate with the first transponder using a frequency modulation scheme, wherein the first transponder is configured to set a first phase rotation mode in a first state for first light signal output from the first I/Q modulator, and transmit, to the second transponder, a first command to specify a second phase rotation mode for second light signal output from the second I/Q modulator, and the second transponder is configured to set, in response to the first command, the second phase rotation mode in a state specified by the first command.

Abstract: A method of controlling a transmission signal, includes transmitting a training signal including four polarization states having a given relation; and performing rotation control and transmission power level control of a polarization component of a data signal, based on a rotation control matrix for a polarization state and an inverse-operation control matrix for a power level imbalance, which are estimated from Stokes parameters related to input power level present on a Poincare sphere acquired from the training signal and Stokes parameters related to output power level present on the Poincare sphere.

Abstract: A transmission device includes: a receiving unit that receives an optical signal; an acquiring unit that acquires spectrum information from the optical signal, the spectrum information relating to a spectrum of the optical signal; and a narrowing calculating unit that calculates an index value for narrowing of a band of the optical signal by calculating a sampling timing error in accordance with the spectrum information, the sampling timing error being an error when a clock signal is extracted from the optical signal.

Abstract: A signal processing device includes: a filter configured to perform an adaptive equalization process of a signal, on a basis of a filter coefficient; an updater configured to update the filter coefficient, on a basis of amplitude of the signal and a target value of the amplitude; and a corrector configured to correct the target value, on a basis of the amplitude of the signal.

Abstract: There is provided a receiving device including a hardware processor configured to demodulate a signal into which a first signal and a second signal are wavelength-multiplexed, into a first baseband signal and a second baseband signal corresponding to the first signal and the second signal, respectively, extract, from the second baseband signal, a signal component of crosstalk from the second signal to the first signal, shift a frequency of the extracted signal component, and compensate for the crosstalk from the second signal to the first signal, based on the extracted signal component shifted by the frequency.

Abstract: An optical transmitter includes, a processor that receives an input data signal from an outside and performs rotation processing for periodically or repeatedly rotating a polarization state or phase of the optical output signal upon the input data signal, an optical modulator that modulates light transmitted from a light source based on the input data signal, a digital-to-analog converter that converts an output of the processor into an analog electric signal, a driving circuit that amplifies an output of the digital-to-analog converter and drives the optical modulator, and a monitoring control circuit that monitors an optical output signal output from the optical modulator and adjusts at least one of an output of the digital-to-analog converter and a gain of the driving circuit based on a result of monitoring of the optical output signal.

Abstract: A signal processing device processes an electric field information signal indicating a polarization multiplexed optical signal in which different modulation formats are used. A first optical signal transmitted in a first polarization component and a second optical signal transmitted in a second polarization component are multiplexed in the polarization multiplexed optical signal. The signal processing device includes a generator and a compensation circuit. The generator selects the first polarization component or the second polarization component based on modulation formats of the first and second optical signals, and generates a compensation value for compensating for an electric field information signal of a selected polarization component based on the electric field information signal of the selected polarization component. The compensation circuit compensates for electric field information signals of the first and second polarization components using the compensation value generated by the generator.

Abstract: There is provided a transmission apparatus configured to receive a frequency-division multiplexed optical signal generated by modulating carrier light based on a plurality of frequency-division multiplexed subcarrier signals, the transmission apparatus including: a processor configured to: extract a plurality of subcarrier signals of the plurality of frequency-division multiplexed subcarrier signals from the frequency-division multiplexed optical signal; calculate signal qualities of the plurality of subcarrier signals; detect a deviation of the signal qualities between the plurality of subcarrier signals; and perform a frequency control of the carrier light generated by an optical source of a transmission apparatus configured to transmit the frequency-division multiplexed optical signal, based on the deviation of the signal qualities.

Abstract: A network controller includes: a first acquisition unit configured to acquire, based on a signal quality amount of each of wavelength paths set in a network of an optical wavelength-multiplexed transmission system, a signal quality amount of each of spans in each of the wavelength paths; an arithmetic unit configured to calculate a signal quality amount of each of spans in a wavelength path of an estimation target, based on the signal quality amount acquired by the first acquisition unit; and an estimation unit configured to estimate a signal quality amount of the wavelength path of the estimation target, based on the signal quality amount calculated by the arithmetic unit.