Fujitsu Corporation

Katsumi Fukumitsu

Osamu Takeuchi

Kosuke Komaki

Taku Saito

Hirofumi Araki

Takeshi Hoshida

Takeshi Ono

Takeshi Sakamoto

Masahiro Shioda

Hisayuki Ojima

Kanji Naito

Toshiki Honda

Kazuhiro Kunimatsu

Tadayuki Takada

Daijiro Tanaka

Shoichi Murakami

Yuichirou Sakamoto

Masakazu Ozaki

An optimization unit in an optical receiver divides a symbol region out of a plurality of symbol regions into which signal points that specifies symbol information included in an optical signal are classified, into a plurality of division regions from the symbol center coordinate of the symbol region. Moreover, the optimization unit accumulates the signal points of the symbol information for every division region in the symbol region. Furthermore, based on the accumulated number of signal points for every division region, the optimization unit controls the average length of a phase estimation unit when the phase noise of the optical signal is calculated.

Optical signal processing device, optical signal processing method and recording medium

An optical transceiver converts a received optical signal to an electric signal and converts the electric signal to a digital signal, and has an adaptive equalizer to adaptively equalize the digital signal, a synchronization part to synchronize a first polarized wave and a second polarized wave contained in the adaptively equalized digital signal and having polarization axes perpendicular to each other, and a symbol offset determination part to determine an amount of symbol offset between the first polarized wave and the second polarized wave based upon symbol synchronization information of the first polarized wave and the second polarized wave supplied from the synchronization part, the symbol offset determination part being configured to repeat determination of the amount of symbol offset and restart the adaptive equalizer until the symbol offset is minimized.

Optical receiver and signal processing method for optical receiver

A digital coherent receiver, includes: an acquisition circuit configured to acquire a plurality of digital electrical signals obtained by sampling a plurality of analog electrical signals by using a sampling signal and digitally converting the plurality of analog electrical signals, the plurality of analog electrical signals being obtained by subjecting a plurality of optical signals to photoelectric conversion; a phase deviation detector configured to output a detection value corresponding to a phase deviation between the sampling signal and the optical signals by using the digital electrical signals; a determination circuit configured to determine whether or not a variation amount of the detection value is equal to or less than a first variation amount; and a compensation circuit configured to compensate wavelength dispersion of the digital electrical signals based on the detection value when the variation amount is equal to or less than the first variation amount.

Digital coherent receiver, optical reception system, and optical reception method

An optical node disposed along a transmission line that uses optical fiber. The optical node includes a first signal generator and a monitor. The first signal generator generates a first measurement signal for measuring polarization mode dispersion values and transmits the first measurement signal along the transmission line. The monitor detects a second measurement signal from the transmission line and measures polarization mode dispersion values by performing signal processing with respect to the second measurement signal.

Optical node, optical network system, and method for measuring polarization mode dispersion

The technique for improving the efficiency in use of power resources while maintaining the received signal quality that satisfies the requirement during a system operation is disclosed. The frame processing apparatus disclosed in the present case includes: a frame processing unit which performs frame processing on an input signal in the designated error processing mode; and a controlling unit which receives the monitoring result relating to the signal quality of the input signal and performs switching control of the designation of the above error processing mode in the frame processing unit based on the received monitoring result.

Frame processing apparatus, optical receiving apparatus, optical transceiving apparatus, optical transmission system, and frame processing controlling method

An optical receiver includes: a waveform distortion compensator to perform an operation on digital signal representing an optical signal generated by an A/D converter to compensate for waveform distortion of the optical signal; a phase detector to generate phase information representing sampling phase of the A/D converter; a phase adjuster to generate digital signal representing an optical signal in which the sampling phase of the A/D converter is adjusted from an output signal of the waveform distortion compensator using the phase information; a demodulator to generate a demodulated signal from the output signal of the phase adjuster; a phase controller to control the sampling phase of the A/D converter; a peak detector to detect a peak value of the phase information while the sampling phase of the A/D converter is controlled by the phase controller; and a compensation controller to control the waveform distortion compensator using the peak value.

Optical receiver

An optical receiver includes: delay interferometers respectively provided in at least two branches that branch a reception signal; a phase shift amount control device that controls a phase shift amount of the delay interferometer in accordance with an optical phase control value; a balanced optical detecting section that respectively photoelectrically converts respective branch signals output from the delay interferometers; a data regenerating section that regenerates transmission data from the photoelectrically converted branch signals output from the balanced optical detecting section; a control section that outputs the optical phase control value based on a signal of the data regenerating section; and a memory that stores therein the optical phase control value output from the control section at the time of signal communication, as a history of control values, wherein the control section refers to the history of control values during a signal communication operation to determine the optical phase control value.

Optical receiver and optical phase control method thereof

An optical signal, which is a low-speed signal superimposed on a high-speed phase modulated optical signal by intensity modulation, is used. In an optical receiver apparatus, a received signal is split, and one of the split signals is O/E converted and low frequency component alone is extracted via a filter. A clock is extracted from low-frequency component by CDR, and is compared with a preset frequency. Using the frequency difference obtained, dispersion compensation is performed with low accuracy. Next, the amount of phase control of the delay interferometeris adjusted so that the amplitude of the electrical signal is maximized. An error rate is measured, and fine adjustment is performed to improve the error rate.

High-speed dispersion compensation control apparatus

The optical reception apparatus of the invention branches into two an RZ-DQPSK optical signal input from an optical transmission path via an optical amplifier, respectively sends this to delay interferometers and photoelectric converters on a pair of arms, separately detects a number of generated errors for the signals propagating through the arms in an error-number detection circuit, obtains a difference in the respective number of generated errors in an error-number detector, and controls phase shift in the delay interferometers so that the difference is within a preset tolerance. By so doing, it is possible to realize excellent reception performance by suppressing the occurrence of the burst error.

Optical reception apparatus and controlling method thereof

A method for controlling an identification point for binarization processing in an optical signal receiver which can diminish a code error rate by optimally tracking an identification point at all times in accordance with a received signal, thereby maintaining transmission quality high. The method comprises identification point electrical signal increment/decrement steps. When the number of error correction operations is determined to have reached a target value in a target value arrival determination step, an identification point electrical signal is left unchanged. In contrast, when the number of error correction operations is determined not to have reached the target value, the identification point electrical signal is incremented or decremented within a predetermined increment/decrement range such that the number of error correction operations approaches the target value.

Optical signal receiver, and method for controlling identification point for binarization processing performed thereby

An error counting circuit is adapted to count a number of code errors of a main signal in an external apparatus which is coupled to an optical transmission path. The error counting circuit includes an error counter which counts error pulses received from the external apparatus and indicative of the number of code errors of the main signal in response to clock pulses having a predetermined period and outputting a counted value for each the predetermined period, and a mechanism for stopping a counting operation of the error counter when a power failure of the external apparatus occurs, so that an erroneous counting operation of the error counter is prevented.

Growing community of inventors

Kawasaki, Japan

Katsumi Fukumitsu