Abstract: A communication device includes: a spectrum controller and optical signal generator. The spectrum controller controls a shape of a spectrum of a first signal. The optical signal generator generates an optical signal based on the first signal, the shape of the spectrum of the first signal being controlled by the spectrum controller. The spectrum controller controls the shape of the spectrum of the first signal according to a second signal.

Abstract: A method and system for multi-channel optical XPM compensation may include a DCM to improve performance of a feed-forward control loop in an optical path in an optical network. Additionally, various spectral overlap schemes may be used with multi-channel WDM optical signals using XPM compensators in parallel, such as at a ROADM node. Polarization diversity may also be supported for XPM compensation including a DCM.

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.

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 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.

Abstract: There is provided a transmission apparatus configured to transmit an optical signal by using a plurality of subcarriers, the transmission apparatus includes: a plurality of modulators, a modulator of the plurality of modulators configured to be capable of changing a modulation format corresponding to a subcarrier of the plurality of subcarriers; a controller configured to control the modulation format for the modulator so as to use a first modulation format and a second modulation format for two or more subcarriers among the plurality of subcarriers and include subcarriers that are different in at least one of a first timing and a second timing of the first modulation format; and a multiplexer configured to multiplex signals modulated by the plurality of modulators.

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: An optical remodulator includes: a polarization diversity modulator configured to modulate an input optical signal to generate an output optical signal by using a first optical modulator implemented for a first polarization state and a second optical modulator implemented for a second polarization state that is orthogonal to the first polarization state; a photo detector configured to optical-to-electrical convert the input optical signal or the output optical signal or both of the optical signals into an electric signal; and a drive signal generator configured to generate a first drive signal that drives the first optical modulator and a second drive signal that drives the second optical modulator based on the electric signal generated by the photo detector.

Abstract: An optical transmitter includes: a light source configured to generate CW light; a drive signal generator configured to generate a drive signal; an optical modulator configured to modulate the CW light with the drive signal so as to generate a first optical signal; a combiner configured to combine the first optical signal and a second optical signal generated by using another light source; and a detector configured to detect a frequency difference between a frequency of the CW light and a center frequency of the second optical signal. The drive signal generator includes: a mapper configured to generate an electric field information signal based on input data; and a frequency controller configured to modify the electric field information signal based on the frequency difference such that the frequency of the CW light matches the center frequency of the second optical signal to generate the drive signal.

Abstract: An optical receiver including: a digital filter that performs spectral shaping on a signal; an analyzer that analyzes a spectrum waveform of the signal; a determiner that determines, based on an analysis result by the analyzer, whether the spectrum waveform of the signal is a Nyquist waveform on the basis of a Nyquist first reference; and a controller that stops the spectral shaping of the signal to be performed by the digital filter when the spectrum waveform of the signal is not the Nyquist waveform as a result of the determination by the determiner, and controls a filter coefficient of the digital filter based on the spectrum waveform of the signal when the spectrum waveform of the signal is the Nyquist waveform as the result of the determination by the determiner.

Abstract: An optical-frequency shift device to shift a first optical-signal of a first optical-frequency to a second optical-signal of a second optical-frequency, including a splitter to split the first optical-signal to optical-signals of first and second polarizations, orthogonal each other, a generator to generate first and fourth controlled-light of the first polarization, and second and third controlled-light of the second polarization, each of frequency differences between the first and second controlled-light and between the third and fourth controlled-light having a spacing equal to a difference between the first and second optical-frequencies, a nonlinear optical-medium in which idler light of the second and first polarization are created by causing cross phase modulation of the optical-signals of the first and second polarizations, the first and third controlled-light, and the second and fourth controlled-light, respectively, and an optical-combiner to combine the idler light of the second and first polarizat

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: A method and apparatus for correcting inter-channel power imbalance and a receiver, applicable to a receiver in a multicarrier optical communication system, where the method includes: receiving by the receiver reference information transmitted by a neighboring receiver; and performing power imbalance error correction by the receiver according to the reference information. With this application, based on performing signal processing in the receiver, estimation errors produced due to power imbalance in the central channel and the neighboring channel may be reduced.

Abstract: A signal processing device includes digital signal processing circuits. Each of the digital signal processing circuits includes: a regeneration circuit that regenerates a bit stream front an electric field information signal of an optical signal; an error correction circuit that corrects an error in the bit stream; an encoder circuit that generates an encoded bit stream from received data; and a generation circuit that generates an electric field information signal from the encoded bit stream. An electric field information signal or a bit stream is given from a regeneration circuit, an encoder circuit or a generation circuit in a first digital signal processing circuit to a second digital signal processing circuit. A regeneration circuit, an error correction circuit or a generation circuit in the second digital signal processing circuit processes the electric field information signal or the bit stream given from the first digital signal processing circuit.

Abstract: An optical-frequency shift device to shift a first optical-signal of a first optical-frequency to a second optical-signal of a second optical-frequency, including a splitter to split the first optical-signal to optical-signals of first and second polarizations, orthogonal each other, a generator to generate first and fourth controlled-light of the first polarization, and second and third controlled-light of the second polarization, each of frequency differences between the first and second controlled-light and between the third and fourth controlled-light having a spacing equal to a difference between the first and second optical-frequencies, a nonlinear optical-medium in which idler light of the second and first polarization are created by causing cross phase modulation of the optical-signals of the first and second polarizations, the first and third controlled-light, and the second and fourth controlled-light, respectively, and an optical-combiner to combine the idler light of the second and first polarizat

Abstract: An error correction circuit includes a first error correction circuit, a second error correction circuit and a controller. The first error correction circuit performs an error correction in a first correction scheme. The second error correction circuit performs an error correction in a second correction scheme. A correction performance of the second correction scheme is lower than a correction performance of the first correction scheme. The controller makes the first error correction circuit perform error correction of a received signal when a capacity of the received signal is smaller than or equal to a processing capacity of the first error correction circuit, and makes the first error correction circuit and the second error correction circuit perform error correction of the received signal when the capacity of the received signal is larger than the processing capacity of the first error correction circuit.

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 signal processing device that processes a digital signal formed by sampling an electric signal using a clock signal, the electric signal being obtained by converting an optical signal inputted from a transmission line, the signal processing device includes: a first chromatic dispersion compensator that compensates a waveform distortion caused by a chromatic dispersion with respect to the digital signal; a first nonlinear optical effect compensator that compensates a waveform distortion caused by a nonlinear optical effect with respect to one signal outputted from the first chromatic dispersion compensator; and a controller that detects a phase fluctuation of other signal outputted from the first chromatic dispersion compensator, and controls the clock signal based on the detected phase fluctuation.

Abstract: A data collecting device includes a receiver configured to receive an optical signal; an optical-to-electrical converter configured to convert the optical signal received by the receiver into an electrical signal; an analog-to-digital converter configured to convert the electrical signal into a digital signal; a data reducing circuit configured to reduce the digital signal output from the analog-to-digital converter; and a transmitter configured to transmit, to a managing device that manages the data collecting device, a signal obtained by reducing the digital signal by the data reducing circuit.

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.