Ntt Electronics Corporation

Nippon Telegraph and Telephone Corporation

Yasuharu Onuma

Etsushi Yamazaki

Masahito Tomizawa

Mitsuteru Yoshida

Katsuichi Oyama

Tomohiro Takamuku

Yoshiaki Kisaka

Kazuhito Takei

Masanori Nakamura

Seiji Okamoto

Yuki Yoshida

Kengo Horikoshi

Masahiro Tachibana

Naoki Miura

Osamu Ishida

Akihiro Yamagishi

Yasuyuki Endoh

Masayuki Ikeda

Sadayuki Yasuda

Yasuyuki Endo

Hiroyuki Nouchi

Eiichi Hosoya

Fumiaki Nakagawa

Hiroyukl Nouchi

Mltsuteru Yoshida

An error correction device includes a first correction unit which performs error correction decoding of data by a repetitive operation, having a full operation state in which the error correction decoding is repeated until convergence is obtained and a save operation state in which the number of times of the repetitive operation is restricted to a predetermined number. An error information estimation unit estimates an input error rate or an output error rate of the first correction unit using a decoding result of the first correction unit, and a control unit which controls transition between the full operation state and the save operation state based on at least one piece of information of the input error rate, the output error rate, and an operation time of the first correction unit. It is thus possible to provide an error correction device that can improve a transmission characteristic while suppressing power consumption.

Error correction device, error correction method, and optical communication system

A plurality of error correction circuits corrects errors of the data transmitted through the plurality of transmission lines. A combining portion combines the plurality of transmission lines to the plurality of error correction circuits. The plurality of transmission lines includes a first transmission line, and a second transmission line having a lower transmission characteristic than the first transmission line. The plurality of error correction circuits includes a first and a second error correction circuit having lower error correction capability and power consumption than the first error correction circuit. The combining portion uses a function to combine a plurality of error correction circuits with one transmission path, combines the first transmission line with the second error correction circuit at a higher rate than the first error correction circuit, and combines the second transmission line with the first error correction circuit at a higher rate than the second error correction circuit.

Error correction device, error correction method, and communication device

A reception circuit includes a first adaptive compensator compensating distortion of a received signal. An adaptive compensation coefficient calculator includes a known-signal detector detecting first and second known-signals from the received signal, a second adaptive compensator compensating distortion of the received signal, a tap coefficient initial value calculator calculating an initial value of a tap coefficient of the second adaptive compensator by comparing the first known-signal with its true value, a first phase shift compensator compensating phase shift of an output of the second adaptive compensator using the second known-signal, and a tap coefficient calculator calculating tap coefficients of the first and second adaptive compensators by comparing at least one of the first and second known-signals compensated by the second adaptive compensator and the first phase shift compensator with its true value.

Transmission characteristic compensation apparatus, transmission characteristic compensation method, and communication apparatus

Fourier transform is performed on a reception signal to obtain a first calculation value. Fourier transform is performed on a known signal to obtain a second calculation value. The first calculation value is divided by the second calculation value to obtain a third calculation value. Inverse Fourier transform is performed on the third calculation value to obtain a fourth calculation value. A maximum value of an amplitude of the fourth calculation value and a sample point at which the maximum value is obtained are detected. The position of the known signal in the reception signal is detected from the sample point at which the maximum value is obtained.

Known signal detection method

A symbol phase difference compensating portion () calculates a first phase difference which is a phase difference between a known pattern extracted from a received signal and a true value of the known pattern and performs phase compensation for the received signal based on the first phase difference. A tentative determination portion () tentatively determines an output signal of the symbol phase difference compensating portion () to acquire an estimated value of a phase. A first phase difference acquiring portion () acquires a second phase difference which is a phase difference between a phase of the output signal and the estimated value of the phase acquired by the tentative determination portion (). A first phase difference compensating portion () performs phase compensation for the output signal based on the second phase difference.

Phase compensation device, phase compensation method and communication apparatus

In a method in which a compensation coefficient calculating portion () calculates a compensation coefficient of a compensation portion () which compensates transmission characteristics of a signal, a known signal is extracted from the signal. Next, a pseudo-random number is added to the extracted known signal. Next, the compensation coefficient is calculated by comparing a true value of the known signal with the known signal to which the pseudo-random number is added.

Compensation coefficient calculation method

A coherent optical reception device includes a local oscillation laser that supplies laser light, a coherent optical reception front-end unit that receives a multi-level modulated optical signal, demodulates the optical signal on the basis of the laser light, and converts a demodulated optical signal into an electrical analog signal, an analog-to-digital converter that converts the analog signal into a digital signal, a compensation unit that compensates for an influence of dispersion due to a wavelength or a polarized wave of the optical signal and recovers a carrier phase of the digital signal, a constellation distortion compensation unit that compensates for constellation distortion of the multi-level modulation included in the digital signal in which an influence of dispersion is compensated for by the compensation unit, and an error correction decoding unit that performs error correction of the digital signal in which the constellation distortion is compensated for.

Coherent optical reception device

An I component compensation unit calculates an I component in which a distortion has been compensated, by forming a first polynomial expressing the distortion of the I component based on an I component and a Q component of a quadrature modulation signal and multiplying each term of the first polynomial by a first coefficient. A Q component compensation unit calculates a Q component in which a distortion has been compensated, by forming a second polynomial expressing the distortion of the Q component based on the I component and the Q component of the quadrature modulation signal and multiplying each term of the second polynomial by a second coefficient. A coefficient calculation unit calculates the first and second coefficients by comparing outputs of the I component compensation unit and the Q component compensation unit and a known signal.

Optical transmission distortion compensation device, optical transmission distortion compensation method, and communication device

An FIR filter convolutes sampled data obtained by sampling a reception signal with tap coefficients. A phase difference detector detects a phase difference between a synchronization timing of a signal waveform estimated from an output signal of the FIR filter and a sampling timing of the output signal. A tap coefficient adjuster adjusts the tap coefficients so as to reduce the phase difference detected by the phase difference detector and causes the sampling timing of the output signal of the FIR filter to track the synchronization timing.

Data phase tracking device, data phase tracking method and communication device

A parallel transfer rate converter inputs first parallel data with number of samples being S1 pieces in synchronism with a first clock, and outputs second parallel data with number of samples being S2=S1&#xd7;(m/p) pieces (p is an integer equal to or larger than 1) in synchronism with a second clock having a frequency which is p/m times of a frequency of the first clock. A convolution operation device inputs the second parallel data in synchronism with the second clock, generates third parallel data with number of samples being S3=S2&#xd7;(n/m) pieces (S3 is an integer equal to or larger than 1) by executing a convolution operation with a coefficient indicating a transmission characteristic to the second parallel data, and outputs the third parallel data in synchronism with the second clock.

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Kanagawa, Japan

Yasuharu Onuma