Fujitsu Corporation

The University of Tokyo

Yutaka Kai

Hideyuki Miyata

Tomoo Takahara

Setsuo Yoshida

Hiroshi Onaka

Toshiki Tanaka

Masato Nishihara

Masaji Noguchi

Tomohiro Ueno

Ryou Okabe

Yasuhiko Aoki

Terumi Chikama

Kyosuke Sone

Goji Nakagawa

Tadao Nakazawa

Keisuke Harada

Isao Tsuyama

Takeshi Hoshida

Susumu Kinoshita

Shigeki Watanabe

Hiroki Ooi

George Ishikawa

Kentaro Nakamura

Yuichi Akiyama

Yutaka Takita

Tomoyuki Kato

Naoki Hashimoto

Naoki Kuwata

Masahiro Yuki

Kazue Otsuka

Yoshiaki Nakano

Hiroshi Miyata

Taku Yoshida

Kazue Okazaki

Yoshinori Nishizawa

Yoichi Takasu

Eric Gouardes

Akira Miura

Jens Rasmussen

Koji Matsunaga

Hiroyasu Ito

Yoshihiro Saito

Toshihisa Kyouno

Kazumasa Kubotera

Jens C Rasmussen

An optical transmitter transmits to an optical receiver a multi-carrier modulated signal light by driving a light source with a modulated signal modulated with a multi-carrier modulation scheme. The optical receiver monitors reception characteristic of any of subcarrier signals included in the modulated signal and transmits a monitor result to the optical transmitter. The optical transmitter controls drive conditions of the light source based on the monitor result received from the optical receiver.

Multi-carrier optical transmission system, optical transmitter, and optical receiver

An optical reception apparatus may include a receiver, a monitor, and a controller. The optical reception apparatus receives multi-carrier modulated signal light modulated by a multi-carrier modulation scheme. The multi-carrier modulation scheme is available to allocate different transmission conditions for each of a plurality of subcarriers in accordance with transmission characteristics of the subcarriers. The receiver may receive from an optical transmission line a training signal light allocated with the same transmission conditions for each of the subcarriers. The monitor may monitor the transmission characteristics of the training signal light to detect a frequency at which a dip of the transmission characteristics occurs. The controller may control, based on the frequency detected by the monitor, a dispersion compensation for the multi-carrier modulated signal light having received a dispersion from the optical transmission line.

Optical reception apparatus

An optical transmitter includes an optical modulator to modulate light having a predetermined wavelength into an optical signal based on a data signal, a memory, and a processor coupled to the memory and the processor configured to modulate an input signal into a multi-carrier signal so as to generate the data signal, the multi-carrier signal including a plurality of subcarriers each to which a transmission capacity is allocated, acquire a first frequency distribution of an intensity of the multi-carrier signal, acquire a second frequency distribution of an intensity of the optical signal, control the modulating of the input signal into the multi-carrier signal to change a number of subcarriers of the multi-carrier signal, and control the optical modulator to adjust a modulation characteristic of the optical modulator so that a divergence between the first frequency distribution and the second frequency distribution is equal to or less than a predetermined value.

Optical transmitter, optical communication system, and optical transmission/reception control method

An apparatus includes a receiver configured to receive a signal that has traveled an optical transmission line without returning output from an optical transmitting device and synchronize with the optical transmitting device in order to demodulate the signal; a dispersion compensator configured to compensate for wavelength dispersion caused by transmission of the signal; an acquisition circuit configured to acquire a transmitting timing at which the signal has been transmitted from the optical transmitting device; a calculation circuit configured to calculate a transmission time period from the optical transmitting device to the receiver from the transmitting timing and a receiving timing at which the signal has been received with the receiver; and an amount setting circuit configured to adjust a dispersion compensation amount of the dispersion compensator in accordance with the transmission time period.

Optical receiving device and method for controlling dispersion compensation amount

There is proved an optical transmission system including: a transmitter configured to transmit an optical signal modulated with a discrete multi-tone (DMT) drive signal; a filter capable of changing a wavelength of the optical signal input from the transmitter; a monitor configured to monitor a power of the optical signal passed through the filter; and at least one processor configured to: set a center wavelength of the filter, shift the center wavelength, detect a change in the power monitored by the monitor, identify a carrier component of the optical signal based on the change in the power, and control a relative relationship between a transmission characteristic of the filter and a wavelength of the carrier component so that the carrier component is included in the optical signal and one of an upper sideband and a lower sideband of the optical signal is at least partially removed by the filter.

Optical transmission system, controller for wavelength tunable filter, and control method of wavelength tunable filter

A bit allocation method is used in an optical transmission system that transmits multicarrier signals of different wavelengths in wavelength division multiplexing. Frequency characteristics of subcarriers included in the multicarrier signals are different between the respective multicarrier signals. The method includes: measuring transmission characteristics of the subcarriers included in corresponding multicarrier signals at different subcarrier frequencies; and determining a number of bits to be allocated to each of the subcarriers included in each of the multicarrier signals based on the transmission characteristics measured at the different subcarrier frequencies.

Method for determining numbers of bits allocated to subcarriers and optical transmission system

A multilevel-intensity modulation and demodulation system includes: a digital-to-analog conversion unit to convert an output level value of a digital signal into an analog signal; a multilevel-intensity-modulated light transmission unit to transmit an optical signal multilevel-intensity modulated based on the analog signal; a multilevel-intensity-modulated light reception unit to receive the optical signal multilevel-intensity modulated, and convert the received optical signal into an analog reception electrical signal; an analog-to-digital conversion unit to convert the analog reception electrical signal into a reception level value; and a controller to convert a transmission multiple gradation level being one of a plurality of multiple gradation levels of multilevel-intensity modulation to which the digital signal is mapped, into the output level value so as to cause the reception level value to be in a desired reception state, and to receive a digital signal corresponding to a reception multiple-gradation-level determined from the reception level value.

Multilevel intensity modulation and demodulation system and method

A transmission apparatus includes: an assigning unit that assigns an information signal to a subcarrier with a frequency different from a frequency of a received radio signal; a creating unit that creates a multi-carrier signal, in which information signals are multiplexed, each of the information signals being assigned to one subcarrier by the assigning unit; and a multiplexing unit that frequency-multiplexes the received radio signal to the multi-carrier signal created by the creating unit and outputs a resulting frequency-multiplexed signal.

Transmission apparatus, transmission system, and transmission method

A transmitting apparatus is used in an electrical frequency division multiplex transmission system including nodes that are on an optical transmission path and that respectively frequency-multiplex a sub-carrier of a unique frequency and a carrier wave to transmit information to a receiving apparatus on the optical transmission path. The transmitting apparatus is disposed in each node and includes a determining unit that receives an input of information concerning unused sub-carriers of a transmission signal in the optical transmission path and determines transmission of the information to the receiving apparatus using an unused sub-carrier; an electrical frequency division multiplex transmission unit that using a frequency of the unused sub-carrier determined by the determining unit, modulates the input information to be transmitted to the receiving apparatus; and a coupling unit that adds to the transmission signal in the optical transmission path, a modulated modulation signal.

Transmitting apparatus, receiving apparatus, optical frequency division multiplex transmission system, and optical signal communication method

An optical transmission system includes: multiplex transmitting devices, each configured to modulate, with an optical carrier, a data signal modulated into light by an optical modulator in a non-linear optical medium arranged on a transmission path so as to multiplex the data signal into the optical carrier, the data signal having a frequency different in each of the multiplex transmitting devices; a receiving device configured to execute optical-to-electrical conversion on the optical carrier received from the transmission path so as to execute reception process of the data signals multiplexed by the multiplex transmitting devices; and a management device configured to specify a frequency band to be used, based on a modulation band of each of the optical modulators, and manage assignment of the frequency of each of the data signals within the frequency band to be used so as to avoid an effect of harmonics generated upon the optical-to-electrical conversion.

Optical transmission system using cross phase modulation

An optical amplification apparatus includes a front-stage semiconductor optical amplifier which amplifies an input light and a rear-stage semiconductor optical amplifier which amplifies an amplified light outputted from the front-stage semiconductor optical amplifier. The front-stage semiconductor optical amplifier exercises auto level control of an output light by exercising variable control of driving current which flows according to applied voltage higher than light emitting threshold voltage of an internal optical amplification element. The rear-stage semiconductor optical amplifier performs gate switching of a transmitted light by exercising switching control of driving current. By doing so, distortion of a waveform is controlled and optical communication quality can be improved.

Optical amplification apparatus

A level control circuit that generates output signal for level control includes: a control information storage that stores control information corresponding to a signal level, a control information circuit that outputs the output signal for level control corresponding to the signal level of a first input signal based on the control information stored in the control information storage; and an information update circuit that updates the control information of the control information storage according to the signal level of a second input signal.

Level control circuit, level control method, and level control system

A phase shift unit provides a prescribed phase difference (&#x3c0;/2, for example) between a pair of optical signals transmitted via a pair of arms constituting a data modulation unit. A low-frequency signal fis superimposed on one of the optical signals. A signal of which phase is shifted by &#x3c0;/2 from the low-frequency signal fis superimposed on the other optical signal. A pair of the optical signals is coupled, and a part of which is converted into an electrical signal by a photodiode. 2fcomponent contained in the electrical signal is extracted. Bias voltage provided to the phase shift unit is controlled by feedback control so that the 2fcomponent becomes the minimum.

Optical transmitting apparatus, optical receiving apparatus, and optical communication system comprising them

An optical output level control apparatus includes a detector configured to detect power of an input optical signal; an amplifier configured to amplify the input optical signal; a memory configured to store data that define a first curved line representing a relationship between the input power and a drive voltage of the amplifier for obtaining a first output level and data that defines a second curved line representing a relationship between the input power and the drive voltage of the amplifier for obtaining a second output level; a generator configured to correct at least one of the first and second curved lines and generate a target curved line representing a relationship between input power and a drive voltage of the amplifier for obtaining a target output level through interpolation based on the first and second curved lines at least one of which is corrected.

Optical output level control apparatus

An optical communication network includes a plurality of optical transmission devices, a communication path, an optical repeater, and a supervisory controller that includes a supervisory control information sender which is installed on at least one of one of the optical transmission devices and the optical repeater and controls a drive signal supplied to a semiconductor optical amplifier that amplifies and outputs input signal light onto the communication path on the basis of the supervisory control information, and a supervisory control information receiver that receives the light which has been output from a semiconductor optical amplifier and transmitted through the communication path, converts the received light to an electric signal and identifies the supervisory control information on the basis of an intensity-modulated component of the total power of the electric signal in at least the other of one of the optical transmission devices and the optical repeater.

Optical communication network and supervisory control device

Growing community of inventors

Kawasaki, Japan

Yutaka Kai