Fujitsu Corporation

Other

Yuichi Akiyama

Takeshi Hoshida

Hiroki Ooi

Hisao Nakashima

Takafumi Terahara

Toshiki Tanaka

George Ishikawa

Akira Miura

Jens Rasmussen

Hideyuki Miyata

Tomofumi Oyama

Kentaro Nakamura

Tomoo Takahara

Takahito Tanimura

Masahiro Yuki

Noriaki Mizuguchi

Yi Ge

Akihiko Isomura

Yoshitaka Nomura

Shigeki Watanabe

Masato Nishihara

Shoichiro Oda

Yutaka Kai

Naoki Kuwata

Yoshinori Nishizawa

Hiroshi Onaka

Terumi Chikama

Tamotsu Akashi

Yoshio Hirose

Yoshio Sakai

Kiichi Sugitani

Guoxiu Huang

Hiroshi Ogiwara

Tomohiro Kaneoka

Jens C Rasmussen

An optical transmission device includes: a frontend circuit, a converter, an equalizer, a recovery, spectrum detector a correction information generator, and a transmitter. The frontend circuit converts an optical signal received via an optical network into an electric signal. The converter converts an output signal of the frontend circuit into a digital signal. The equalizer equalizes the digital signal or a second digital signal that is generated based on the digital signal. The recovery recovers a symbol from an output signal of the equalizer. The spectrum detector detects a reception spectrum of the optical signal based on the digital signal or the second digital signal. The correction information generator generates, according to the reception spectrum, correction information for correcting a shape of a transmission spectrum of the optical signal. The transmitter transmits the correction information to the source device.

Optical transmission device and optical transmission system

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.

Reception device and method of detecting supervisory control signal

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.

Optical transmitter and skew compensation method

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.

Transmission system and method

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.

Optical transmitter and control method for optical transmitter

An optical reception apparatus includes an equalization processor, an extraction unit, a first ratio calculator, and an instruction transmitter. The equalization processor suppresses fluctuations in amplitude of an electrical signal obtained by converting an optical signal including a plurality of pilot symbols subjected to BPSK modulation by an optical transmission apparatus. The extraction unit extracts the pilot symbols from the electrical signal with suppressed fluctuations in amplitude. The first ratio calculator calculates a ratio of an amplitude component to a phase component of each of the pilot symbols extracted by the extraction unit. The instruction transmitter transmits information relating to skew adjustment based on the ratio of the amplitude component to the phase component calculated by the first ratio calculator for each of different control values to the optical transmission apparatus.

Optical reception apparatus, optical transmission apparatus, optical communication system, and skew adjusting method

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.

Digital signal processing circuit and signal processing device that includes a plurality of digital signal processing circuits

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.

Optical transmitter and control method of optical transmitter

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.

Optical transmission device, optical modulator, and bias control method

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.

Transmission apparatus, reception apparatus and modulation method

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*&#x3c0; 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.

Optical transmitter, optical transmission system and optical communication control method

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.

Optical transmitter and method for controlling bias of optical modulator

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.

Optical transmitter, method for controlling optical modulator, and controller for optical modulator

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.

Optical transmission device, transmission system, and transmission method

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.

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Kawasaki, Japan

Yuichi Akiyama