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 transmitter includes an optical modulator that is driven by a driving signal, an acquisition part, and a controller. The acquisition part obtains a relationship between a fluctuation of a parameter to adjust the driving signal and a fluctuation of a state of output light from the optical modulator due to the fluctuation of the parameter. The controller controls an amplitude of the driving signal on the basis of the obtained relationship.

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 transmission device includes an optical modulator and a processor. The optical modulator optically modulates an optical signal with a driving signal to output a modulated optical signal. The processor performs ABC on a bias of the optical modulator, using the modulated optical signal, so as to cause the bias to converge to an optimum point. The processor starts the ABC using a modulated optical signal optically modulated with a QPSK signal at start-up timing, acquires an optimum value that is a bias value when the bias converges to the optimum point, and stops the ABC. After the ABC is stopped, the processor sets the acquired optimum value as an initial value, and restarts the ABC using a modulated optical signal optically modulated with an N-QPSK signal.

Abstract: There is provided an optical transmission device including: a generator configured to convert an electric signal into a plurality of parallel signals, modulate the plurality of parallel signals, shift center frequencies of spectra of the plurality of modulated parallel signals into different frequencies, so as to generate signals accommodated in a plurality of sub-channels each having different center frequencies, and generate a multiplexed signal by multiplexing the signals accommodated in the plurality of sub-channels; a transmitter configured to optical-modulate the multiplexed signal and transmit the optical-modulated signal to an optical reception device; and a controller configured to control a frequency spacing between adjacent sub-channels of the plurality of sub-channels, based on a monitoring result of reception characteristics of the signals accommodated in the plurality of sub-channels within the multiplexed signal in the optical reception device.

Abstract: A signal shifted from a carrier frequency in a frequency domain by using digital signal processing is generated, and the optical modulator is driven with a drive signal based on the signal. A monitor monitors whether or not a component of a modulated signal light output from the optical modulator appears in a specific frequency depending on a frequency shift performed by the digital signal processing, and the controller controls a relation between a sign of the drive signal and an operating point of the optical modulator according to a monitored result.

Abstract: An optical transmission apparatus includes an optical modulator that is driven by a drive signal generated from an electrical signal obtained by performing a digital signal processing on a data signal, a detector configured to detect a change in a spectrum of output light of the optical modulator, and a controller configured to control the digital signal processing based on a detection result of the detector.

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: 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: An optical transmission device includes: a drive signal generate unit that generates a drive signal; a modulation unit that modulates an optical signal in accordance with the drive signal; a detect unit that detects a fluctuation of a signal component of the drive signal with respect to an optical signal output by the modulation unit; and a correct unit that corrects a parameter of the drive signal generate unit in accordance with a detect result of the detect unit so that a non-linear characteristic of the modulation unit gets closer to a linear characteristic.

Abstract: There is provided an optical transmission device including: a generator configured to convert an electric signal into a plurality of parallel signals, modulate the plurality of parallel signals, shift center frequencies of spectra of the plurality of modulated parallel signals into different frequencies, so as to generate signals accommodated in a plurality of sub-channels each having different center frequencies, and generate a multiplexed signal by multiplexing the signals accommodated in the plurality of sub-channels; a transmitter configured to optical-modulate the multiplexed signal and transmit the optical-modulated signal to an optical reception device; and a controller configured to control a frequency spacing between adjacent sub-channels of the plurality of sub-channels, based on a monitoring result of reception characteristics of the signals accommodated in the plurality of sub-channels within the multiplexed signal in the optical reception device.

Abstract: An optical transmitter has an electrical signal generator configured to generate an electrical drive signal based upon input data; an optical modulator configured to modulate an input light by the electrical drive signal, the optical modulator having a first waveguide pair, a second waveguide pair, and a phase shifter that provides a phase difference between light waves travelling through the first waveguide pair and the second waveguide pair; and a controller configured to set the phase difference at the phase shifter to 0+n*? radians, where it is an integer, when a modulation scheme of the optical modulator is changed from a first scheme using four or more phase values to a second scheme using two phase values.

Abstract: An optical signal transmitter includes first and second modulation units, a combiner, and a control unit. The first and second modulation units generate first and second modulated optical signals, respectively. The combiner combines the first and second modulated optical signals to generate a polarization multiplexed optical signal. The control unit controls at least one of the first and second modulation units so that the optical powers of the first and second modulated optical signals become approximately equal to each other.

Abstract: An optical transmitter includes: a drive signal generator configured to generate a drive signal from input data; an optical modulator configured to generate an optical signal corresponding to the drive signal; a superimposer configured to superimpose a first reference signal on the drive signal and superimpose a second reference signal on a bias voltage of the optical modulator; a detector configured to detect the first reference signal and the second reference signal included in the optical signal, and generate a first monitor signal indicating intensity and a phase of the detected first reference signal and a second monitor signal indicating intensity and a phase of the detected second reference signal; and a controller configured to control the bias voltage of the optical modulator in a control scheme determined based on the first monitor signal and the second monitor signal.

Abstract: An optical transmitter includes an optical modulator that is driven by a driving signal, an acquisition part, and a controller. The acquisition part obtains a relationship between a fluctuation of a parameter to adjust the driving signal and a fluctuation of a state of output light from the optical modulator due to the fluctuation of the parameter. The controller controls an amplitude of the driving signal on the basis of the obtained relationship.

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 apparatus includes an optical modulator that is driven by a drive signal generated from an electrical signal obtained by performing a digital signal processing on a data signal, a detector configured to detect a change in a spectrum of output light of the optical modulator, and a controller configured to control the digital signal processing based on a detection result of the detector.