Fujitsu Corporation

Fujitsu Telecom Networks Limited

Kosuke Komaki

Taku Saito

Taketo Endo

Hisao Nakashima

Norifumi Shukunami

Takeshi Sakamoto

Hiroyuki Itoh

Tomoaki Takeyama

Hiroyuki Itou

Osamu Takeuchi

Taizo Maeda

Hiroshi Iizuka

Katsumi Fukumitsu

Hiroshi Nishida

Hirofumi Araki

Makoto Shimizu

Shoichi Murakami

Shuzo Matsushita

Yusuke Shigeta

Takeshi Hoshida

Nobukazu Koizumi

Naoya Okada

Takuji Maeda

Shota Mori

Masahiro Yuki

Masahiro Shioda

Yuji Tamura

Kazuhiko Hatae

Koji Nakamuta

Yuji Shimada

Yoshinobu Matsukawa

Masao Nakata

Shingo Hara

Yoshio Shimano

Hiroki Oi

Noriyasu Nakayama

Hironobu Hongou

Yuichirou Sakamoto

Yuya Osumi

Hidetoshi Sato

Masamichi Sugamoto

Koji Biwa

An optical receiver includes an optical filter that transmits signal light to be received from wavelength-multiplexed signal light, a light source that outputs local oscillation light, a 90-degree hybrid circuit that causes the local oscillation light output from the light source to interfere with the signal light transmitted through the optical filter to output interference signal light, a converter that converts the interference signal light into an electrical data signal, a spectrum detector that detects a frequency spectrum of the electrical data signal based on the electrical data signal, and a controller that controls a center frequency of a passband of the optical filter based on a shape of the frequency spectrum.

Optical receiver

An optical transmitter includes an electro-optic modulator, a monitor circuit that monitors output light of the electro-optic modulator, and a processor that controls a bias voltage of the electro-optic modulator using a monitoring result of the monitor circuit, wherein the processor superimposes a first dither signal with a first frequency and a second dither signal with a second frequency different from the first frequency, onto one bias voltage in a time sharing manner, calculates a first control error based on a first component oscillating at the first frequency and a second control error based on a second component oscillating at the second frequency based on the monitoring result, and determines a control value for controlling the bias voltage using the first control error and the second control error.

Optical transmitter, communication apparatus, and method of controlling bias voltage of electro-optic modulator

An optical apparatus includes an attenuator, a photoelectric convertor, an amplifier, and a processor. the attenuator attenuates signal light. The photoelectric convertor converts the signal light attenuated by the attenuator into an electric signal. The amplifier adjusts a gain of the electric signal. The processor detects a monitor value of a target channel from an output signal of the amplifier, calculates a power value of the target channel from the detected monitor value, calculates a difference value between the power value and a target power value, calculates a attenuation amount by adding a current attenuation amount, which is currently set to the attenuator, to the difference value, controls the gain of the amplifier so that the difference value of the target channel is minimized when the set attenuation amount is less than zero, and sets the attenuation amount to the attenuator when the attenuation amount is zero or more.

Optical apparatus and optical receiving method

A network system includes a first device and a second device coupled to the first device. The second device configured to calculate a bandwidth of an optical signal narrowed by a wavelength filter from the number of wavelength filters on a transmission route of the optical signal, to select, based on a plurality of combinations of a degree of multilevel and the baud rate, and a correspondence between a lower limit value of a bandwidth of the optical signal and a lower limit value of an optical signal to noise ratio (OSNR) for maintaining predetermined quality of the optical signal, one or more first combinations from the plurality of combinations, to select a second combination from the one or more first combinations, and to set the degree of multilevel and the baud rate of the second combination in the first device.

Network system, management device, and network design method

An optical communication apparatus has an interface circuit that acquires transfer condition information including a bit rate and a channel spacing of an optical network, a processor that selects a modulation scheme in accordance with the transfer condition information and operates in the modulation scheme, wherein the processor is configured to select a first modulation scheme when the bit rate is greater than a first value in accordance with the channel spacing, and select a second modulation scheme when the bit rate is smaller than the first value, the second modulation scheme having a data transfer performance higher than the first modulation scheme.

Optical communication apparatus, server apparatus, and optical transport system

There is provided an optical transmitter including a memory, a processor coupled to the memory and the processor to generate an electric signal, an optical generator to generate light, an optical modulator to modulate the light with the electric signal to create an optical signal, a first voltage electrode to apply a first voltage to the optical signal, a second voltage electrode to apply a second voltage to the optical signal to which the first voltage is applied, and a detector to detect an optical power of the optical signal to which the second voltage is applied, wherein the processor stops generating the electric signal, controls the first voltage electrode to change the first voltage after the stop of generating the electric signal, and controls the second voltage electrode to change the second voltage according to the detected optical power after the change of the first voltage.

Optical transmitter

An optical transmission apparatus may include a coherent detector, a photoelectric converter, an amplifier, a gain controller, and an optical power monitor. The coherent detector may perform a coherent detection on received light including a plurality of wavelengths to select light having any one of the wavelengths. The photoelectric converter may convert the light having the selected wavelength to an electrical signal. The amplifier may amplify the electrical signal. The gain controller may control a gain of the amplifier depending on an output amplitude of the amplifier. The optical power monitor may calculate an optical power level of the selected wavelength based on the gain and the output amplitude.

Optical transmission apparatus, optical power monitor, and method of monitoring optical power

An optical transmission apparatus includes: a coherent detector configured to receive light including different polarization components from an optical transmission path, and perform coherent detection of received light including the different polarization components; an adaptive equalizer configured to adaptively equalize, by a digital filter, a complex electric signal for each of the polarization components obtained by the coherent detection, a gain value for controlling an amplitude of the complex electric signal being applied to the complex electric signal; and a polarization dependent loss monitor configured to determine a polarization dependent loss of the optical transmission path, based on a correction filter parameter obtained by correcting a filter parameter of the digital filter according to the gain value, the filter parameter being adaptively updated by an adaptive equalization of the adaptive equalizer.

Optical transmission apparatus, optical transmission system, and polarization dependent loss monitor

An optical transmission apparatus includes: an optical receiver configured to receive an optical signal; a variable optical attenuator configured to adjust a power of the optical signal to be input to the optical receiver according to a variable attenuation amount; and a controller configured to control the attenuation amount of the variable optical attenuator based on an electrical signal obtained by performing a coherent detection and a photoelectric conversion on the optical signal received by the optical receiver.

Optical transmission apparatus and method for controlling optical power

An optical transmission system includes comprising: a first optical transmission apparatus to transmit wavelength-multiplexed optical signals; and a second optical transmission apparatus to receive the wavelength-multiplexed optical signals, the second optical transmission apparatus including: a receiver to perform digital coherent reception; a wavelength spacing monitor to transform a reception signal obtained by the digital coherent reception from a time domain signal to a frequency domain spectrum signal, and to monitor wavelength spacing of the spectrum signal; and a transmitter to transmit, to the first optical transmission apparatus, wavelength control information according to a monitor result obtained by the wavelength spacing monitor or the monitor result, wherein the first optical transmission apparatus includes: a receiver to receive the wavelength control information or the monitor result; and a control unit to control the wavelength spacing based on the wavelength control information or the monitor result received by the receiver.

Optical transmission system, optical transmission apparatus and wavelength spacing measurement apparatus

An optical transmission device includes a receiver that receives first light, a transmitter that outputs second light, a memory, a processor coupled to the memory, configured to control a first optical level of the second light in such a way that a second optical level calculated based on an optical level of the received first light and an optical level of the second light that is output from the transmitter becomes a predetermined target value, a combiner that combines the received first light and the second light for which the first optical level is controlled by the processor, and an amplifier that amplifies the combined light.

Optical transmission device and optical transmission method

A transmitting device includes a transmitter configured to transmit signal light to an external receiver over a medium included in a transmission line; and a controller configured to control a transmission level of the signal light in accordance with a reception level of probe light which is input from the receiver over the medium in the transmission line.

Transmitting device, communication system, and method for transmission level control

An optical transmission device including a wavelength selective switch including plural output ports, an optical intensity monitoring device that receives each optical signal output from the plural output ports of the wavelength selective switch and monitors the optical intensity of the optical signals, and a controller that controls optical intensity of the optical signals from the plural output ports of the wavelength selective switch based on the optical intensities monitored by the optical intensity monitoring device.

Optical transmission device

A transmission apparatus includes: an amplifier controller configured to determine a target value for an average optical input power of a transmitting amplifier in a transmitting-side apparatus, based on an index based on a quality of transmission from an output of the transmitting amplifier to an output of a receiving amplifier in a receiving-side apparatus; and a pre-emphasis controller configured to determine amounts of adjustment of transmission optical powers for respective wavelengths, based on the target value and per-wavelength reception optical powers at the output of the receiving amplifier.

Transmission apparatus, transmission system, and method of controlling average optical input power

There is provided an optical transmitter including: a demultiplexer configured to divide a data frame of a transmission signal into subframes with a predetermined length so as to form the subframes in a plurality of signal lanes; an index generator configured to generate an index for indicating an order of the signal lanes; a lane rearrangement unit configured to rearrange the order of the signal lanes according to the index; a carrier controller configured to generate a frequency offset of a carrier corresponding to the index; a mapping unit configured to map the transmission signal in the plurality of signal lanes with the rearranged order to the transmission signal with a phase corresponding to the frequency offset; and a transmitting unit configured to optically modulate the mapped transmission signal so as to transmit the modulated transmission signal.

Growing community of inventors

Kawasaki, Japan

Kosuke Komaki