Fujitsu Corporation

Hiroshi Nakamoto

Takao Naito

Hiroki Ooi

George Ishikawa

Toshiki Tanaka

Terumi Chikama

Takuji Yamamoto

Yoshinori Nishizawa

Kenichi Torii

Takeshi Hoshida

Shigeki Watanabe

Hiroshi Onaka

Hideyuki Miyata

Shoichiro Oda

Toru Katagiri

Akira Miura

Tetsuya Kiyonaga

Naomasa Shimojoh

Kazunori Hayami

Hiroyuki Irie

Shinji Sonoda

An optical transmission apparatus includes: an optical amplifier configured to amplify a wavelength multiplexing light to be transmitted, the wavelength multiplexing light being input thereto; a combining unit configured to combine a plurality of non-signal lights in such a way that angles formed between polarization planes of the plurality of non-signal lights of a wavelength of wavelengths belonging to an amplification band of the optical amplifier become equal, the wavelength being different from a wavelength of a polarization multiplexing signal light; and a wavelength multiplexer configured to generate the wavelength multiplexing light to be input to the optical amplifier by multiplexing the plurality of non-signal lights combined by the combining unit and the polarization multiplexing signal light.

Optical transmission apparatus and optical transmission method

A communication system includes a transmission path through which an optical signal is propagated; and dispersion slope imparting sections provided on a transmitting side and a receiving side of the transmission path, the dispersion slope imparting sections imparting different dispersion and dispersion slope characteristics in accordance with a wavelength band of the optical signal, wherein the dispersion and dispersion slope characteristics imparted by the dispersion slope imparting section on the transmitting side is different from those on the receiving side.

Communication system, dispersion slope imparting section, and method for communicating

In the optical transmitting system, the optical transmitter transmits a polarization combined signal light obtained by combining a pair of lights having different polarization orientation, and the optical receiver separates the combined signal light. In the optical transmitter, a polarization changer changes a state of polarization of the polarization combined signal light. In the optical receiver, a polarization reverse-changer changes the state of the polarization combined signal light in a reverse direction of the change that polarization changer applies.

Optical transmission system, transmitter, receiver and method

A polarization fluctuation compensation device, when WDM light received by, for example, an optical reception device includes a polarization scrambled optical signal and a non-polarization scrambled optical signal, collects information related to whether optical signals having respective wavelengths are polarization scrambled, obtains a target value of control parameters which are different from each other, according to the speed of polarization fluctuations in the non-polarization scrambled optical signal based on the collected information, and performs reception processing of the non-polarization scrambled optical signal by using a control parameter set as the target value. As a result, an influence of fast polarization fluctuations generated resulting from an interaction between optical signals having respective wavelengths can be reliably compensated for, thereby enabling to realize excellent reception characteristics.

Polarization fluctuation compensation device and optical communication system

An optical transmitter of the invention phase modulates an output light from a light source according to data using a phase modulator, and then supplies it to an intensity modulator. The intensity modulator performs pulse carving of the output light from the phase modulator in accordance with a clock signal in which a duty cycle is changed to a value different from 50% by a waveform transformation circuit, with an operating range being a slope from a trough to a crest in the photoelectric response characteristics. As a result, it is possible to realize, at the same time, duty cycle and chirp characteristics that enable excellent transmission characteristics to be obtained.

Optical transmitter and optical transmission system

An optical transmission system capable of efficiently reducing waveform distortion of an optical signal. A transmitting-side distortion compensation coefficient storage of a transmitting station stores transmitting-side distortion compensation coefficients for compensating for waveform distortion of an optical signal to be transmitted to a receiving station. A transmit signal processor performs distortion compensation on the optical signal on the basis of a suitable transmitting-side distortion compensation coefficient stored in the transmitting-side distortion compensation coefficient storage. A transmitter transmits the distortion-compensated signal to a transmission path. A receiver of the receiving station receives the optical signal from the transmission path. A receiving-side distortion compensation coefficient storage stores receiving-side distortion compensation coefficients for compensating for waveform distortion of the optical signal received by the receiver. A received signal processor performs distortion compensation on the received optical signal on the basis of a suitable receiving-side distortion compensation coefficient.

Optical transmission system

A waveform converting unit gives a change to a clock signal as a periodic voltage fluctuation that drives a pulse carver unit carrying out shaping into an RZ waveform. The pulse carver unit receives a bias voltage applied thereto from a bias voltage applying unit, is driven by the clock signal that is given a change by the waveform converting unit and that is amplified by an amplifying unit, and outputs an RZ pulse whose duty has been changed.

Optical transmitting apparatus and optical communication system

A WDM optical transmission system of the invention: detects an optical waveform of an intensity-modulated optical signal adjacent to a phase-modulated optical signal in a wavelength range; calculates a phase modulation drive waveform for canceling XPM of the phase-modulated optical signal affected by the adjacent intensity-modulated optical signal in the optical transmission path, based on the detected result; and additionally phase-modulates the phase-modulated optical signal synchronously with the adjacent intensity-modulated optical signal, according to the drive waveform, to thereby compensate the XPM. As a result, excellent transmission characteristics can be realized.

WDM optical transmission system and WDM optical transmission method

An optical wavelength controlling method and a system thereof for an optical wavelength division multiplexing transmission system, wherein a plurality of wavelengths of channels are multiplexed and transmitted by an optical transmitting unit, and the multiplexed wavelengths are divided into the wavelengths of the channels by an optical receiving unit, are disclosed. The optical wavelength controlling method includes: a step of reducing optical power of the wavelength of a target channel, and transmitting the wavelengths; a step of evaluating channel crosstalk based on a code error rate of a channel adjacent to the target channel, and detecting a shift of the wavelength of the target channel; and a step of compensating for the shift of the wavelength of the target channel.

Optical wavelength controlling method and a system thereof

According to the present invention, for example, a WDM light containing 10 Gbit/s signal lights and 40 Gbit/s signal light arranged on wavelength grids at 25 GHz intervals is branched into two by an input side optical coupler to be sent to two routes. In one route side, only the 10 Gbit/s signal lights are demultiplexed by a 10 Gbit/s demultiplexer and a plurality of 1&#xd7;2 optical switches, while in the other route side, only the 40 Gbit/s signal lights are demultiplexed by a 40 Gbit/s demultiplexer and a plurality of 1&#xd7;2 optical switches. Further, the respectively demultiplexed signal lights are multiplexed for each modulating rate by a 10 Gbit/s multiplexer and a 40 Gbit/s multiplexer, and thereafter, further multiplexed by an output side optical coupler to become a WDM light. Thus, it becomes possible to arrange signal lights having different modulating rates at arbitrary wavelengths on wavelength grids at predetermined intervals.

Optical demultiplexing method and optical multiplexing method, and optical transmission apparatus using same

The present invention has an object to provide a technology for monitoring the quality of a WDM signal light, capable of quickly and accurately judging an occurrence of quality deterioration of signal light and a deterioration factor thereof. To this end, according to a quality monitoring apparatus of WDM signal light of the present invention, a part of the WDM signal light being propagated through an optical transmission path is branched as a monitor light, a signal light of one wavelength contained in the monitor light is selected as a channel to be measured. Then, the frequency of occurrences of bit error for the channel to be measured is repeatedly measured for a plurality of times, and whether or not the signal quality is deteriorated is judged, together with the deterioration factor based on the measurement results, and a control signal light for adjusting the signal light power according to the judgment result is transmitted to the optical transmission path, to achieve the improvement of a characteristic of the WDM signal light.

Quality monitoring method and apparatus for wavelength division multiplexed optical signal and optical transmission system using the same

A plurality of pump light sources generate plural variations of pump light having different frequencies. A modulation circuit intensity-modulates the plural variations of pump light in the predetermined periods, respectively. A pump light pair whose frequency difference equals a Raman shift frequency are modulated such that they cannot simultaneously enters an emission state. A wavelength-multiplexer wavelength-multiplexes the plural variations of pump light modulated by the modulation circuit. A optical guide device guides the plural variations of pump light wavelength-multiplexed by the wavelength-multiplexer to an optical fiber.

Raman amplifier utilizing pump modulation for expanding gain band width

The present invention offers a compensation device having a transmission property for collectively compensating inclinations of accumulated transmission properties in a signal wavelength band of light signals of a plurality of channels configuring a wavelength-multiplexed light, among wavelength dependencies of transmission properties of a plurality of sets of light demultiplexers and light multiplexers.

Apparatus and method of compensating transmission property of light demultiplexer/light multiplexer

An optical transmission apparatus and method for changing a rise time (t) and fall time (t) of a signal light to be transmitted, to reduce wavelength dispersion characteristics and nonlinear effect of a transmission path. A transmitter includes a ttadjusting circuit capable of adjusting tand tof a modulation signal so that the modulation signal is optimized in accordance with reception characteristics. A modulator then modulates a light with this adjusted modulation signal, and the modulated light is then transmitted to a receiver via a transmission path. Therefore, by transmitting the modulated light having changed tand t, the influence of wavelength dispersion characteristics and nonlinear effect of the transmission path can be offset, so that the waveform deterioration of signal light after transmission can be reduced.

Optical transmission apparatus and method which adjust rise and fall time of signal light to be transmitted

The present invention has an object to provide an optical transmission technology using Raman amplification wherein a supervisory signal transferred among a plurality of optical transmission apparatuses is superimposed on a main signal light by using a pumping light for Raman amplification. To this end, a Raman amplifier applied with the optical transmission method of the present invention, is provided with a supervisory signal superimposing section for superimposing a supervisory signal transferred among the optical transmission apparatuses on at least one of a plurality of pumping lights of different wavelengths to be supplied to a Raman amplification medium via a multiplexer from a pumping light generating section, thereby transmitting the main signal light propagated through the Raman amplification medium to be Raman amplified, which is superimposed with the supervisory signal.

Growing community of inventors

Kawasaki, Japan

Hiroshi Nakamoto