Abstract: A tap-coefficient control circuit sets the tap coefficient converged by the second tap coefficient updater as an initial value of the tap coefficient in the first digital filter which is to be updated by the first tap coefficient updater, arranges the tap coefficients converged by the second tap coefficient updater in descending order of contribution degree to the convergence operation of tap coefficient update in the first tap coefficient updater, judges the tap coefficient not less than upper specified number to be valid and the tap coefficient less than the specified number to be invalid, and sets the tap coefficient of the first digital filter corresponding to the tap coefficient judged to be invalid to zero not to be used in a calculation of the first tap coefficient updater until a next judgment result is made.

Abstract: Part of compensation of the transmission characteristics of the optical transmitter is performed by transmitter compensation circuitry disposed at a stage prior to the optical transmitter. Remaining part of compensation of the transmission characteristics of the optical transmitter and compensation of the transmission characteristics of the optical receiver is performed by a receiver compensation circuitry disposed at a stage subsequent to the optical receiver. Transmitter compensation characteristics of the transmitter compensation circuitry is set so that a peak-to-average-power ratio of an output signal from the transmitter compensation circuitry becomes equal to or smaller than a predetermined value.

Abstract: Part of compensation of the transmission characteristics of the optical transmitter is performed by transmitter compensation circuitry disposed at a stage prior to the optical transmitter. Remaining part of compensation of the transmission characteristics of the optical transmitter and compensation of the transmission characteristics of the optical receiver is performed by a receiver compensation circuitry disposed at a stage subsequent to the optical receiver. Transmitter compensation characteristics of the transmitter compensation circuitry is set so that a peak-to-average-power ratio of an output signal from the transmitter compensation circuitry becomes equal to or smaller than a predetermined value.

Abstract: First compensation circuitry includes a first digital filter compensating a phase difference between a phase of a symbol of a received signal and a sampling timing, and first filter coefficient calculation circuitry calculating a filter coefficient of the first digital filter as a first filter coefficient. Second filter coefficient calculation circuitry calculates, as a second filter coefficient, a filter coefficient for adaptive equalization that compensates distortion due to temporally changing polarization dispersion, based on an output of the first digital filter. Coefficient combination circuitry combines the first filter coefficient and the second filter coefficient. Second compensation circuitry includes a second digital filter which uses a filter coefficient combined by the coefficient combination circuitry and performs a compensation of the phase difference between the phase of the symbol of the received signal and the sampling timing, and a process of the adaptive equalization at the same time.

Abstract: A process of estimating a transfer function or an inverse transfer function of the optical transmitter from first data obtained by the optical receiver when a first known signal is transmitted from the transmitter to the receiver, and a temporary transfer function or a temporary inverse transfer function of the optical receiver, is performed for multiple frequency offsets between the optical transmitter and the optical receiver. At this time, the transfer function or the inverse transfer function of the optical transmitter is estimated by comparing the first data obtained by compensating at least one or none of a temporary transfer function of the optical receiver and transmission path characteristics detected in the receiver, with a first known signal before transmission to which what is not compensated for the first data between the temporary transfer function of the optical receiver and the transmission path characteristic is added.

Abstract: A binary arithmetic device includes an LPS/MPS determining unit that determines, using a context variable, a range length, and an offset, whether a code is an inferior probability code or a superior probability code, a renormalization processing unit that performs renormalization processing on the range length and the offset, and a context-variable calculating unit that derives the binary data of the code using a determination result and updates the context variable according to the determination result. The renormalization processing unit 15 includes a first renormalizing unit and a second renormalizing unit and a selecting unit that selects, according to the determination result, an output of the first renormalizing unit or an output of the second renormalizing unit.

Abstract: A known pattern comparison type phase difference detection unit (12) detects a phase difference between a known pattern extracted from a received signal and a true value of the known pattern as a first phase difference. M indicates the number of modulation phases in a phase modulation method of the received signal. An M-th power type phase difference detection unit (13) removes a modulation component by raising the received signal to M-th power, and detects phase variation from a modulation phase point used for mapping on a transmission side, as a second phase difference. A phase compensation unit (11) compensates phase variation of the received signal based on an addition result of the first phase difference and the second phase difference.

Abstract: A band division timing adjustment unit aligns timings of a plurality of signals, which are generated by dividing a received signal according to a plurality of frequency bands, in a time domain and combines the plurality of signals for which the timings have been aligned. A chromatic dispersion compensation unit compensates chromatic dispersion of an output signal of the band division timing adjustment unit for each of the plurality of frequency bands.

Abstract: A band division timing adjustment unit (10) aligns timings of a plurality of signals, which are generated by dividing a received signal according to a plurality of frequency bands, in a time domain and combines the plurality of signals for which the timings have been aligned. A chromatic dispersion compensation unit (17) compensates chromatic dispersion of an output signal of the band division timing adjustment unit (10) for each of the plurality of frequency bands.

Abstract: A method estimating transmission characteristics of an optical transmitter of a transmission unit and an optical receiver of a reception unit, including: estimating a temporary transfer or inverse transfer function of the optical receiver; estimating a transfer or inverse transfer function of the optical transmitter from first data acquired by the reception unit when a first known signal is transmitted from the transmission unit, and the estimated temporary transfer or inverse transfer function of the optical receiver, a difference between the first known signal and an original first known signal is minimized; and estimating a transfer or inverse transfer function of the optical receiver from second data acquired by the reception unit when a second known signal is transmitted from the transmission unit, and the estimated transfer or inverse transfer function of the optical transmitter, a difference between the second known signal and an original second known signal is minimized.

Abstract: 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.

Abstract: 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.

Abstract: A packet receiving unit (4) receives an IP packet having a network parameter and a transmission source identifier. A transmission source identifier table (5) records the transmission source identifier of the received IP packet. A packet storage processing unit (6) stores the received IP packet in a first buffer (7) regardless of the network parameter if the transmission source identifier of the received IP packet coincides with a transmission source identifier recorded in the transmission source identifier table. A packet extraction/transmission unit (8) extracts the IP packet stored in the first buffer (7) from the first buffer (7) and transmits the packet.

Abstract: In the case of implementing a polarization separation circuit, a polarization rotator, and the like by inserting a thin-film element into a substrate in one optical interference circuit, one common large-sized groove shared among a plurality of thin-film elements for their insertion has been formed. The optical waveguide type device of the present invention is configured such that at least one groove intersects only one corresponding optical waveguide for inserting the thin-film element and does not intersect other optical waveguides adjacent to the one corresponding optical waveguide. This groove substantially has a rectangular shape, and has a minimum size adapted to the thin-film element to be inserted so as to stably hold and fix the thin-film element in the groove. Adjacent grooves are formed so as to be arranged such that their portions in a direction substantially vertical to the optical waveguide are facing each other.

Abstract: 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.

Abstract: A light modulation device detects a power of the modulated optical signal modulated by each of an I-component optical modulator and a Q-component optical modulator, synchronously-detects a component of a frequency fd from the power of the modulated optical signal, outputs a dither signal of a frequency fd/n (where n is a positive integer equal to or larger than 1) applied to a first bias voltage or a second bias voltage when adjusting the first bias voltage or the second bias voltage, outputs two dither signals having a frequency fd/m (where m is a positive integer equal to or larger than 1, where n<m), which are mutually orthogonal to each other, applied to the first and second bias voltages when adjusting a third bias voltage, and adjusting bias voltages by increasing or decreasing bias voltages based on a synchronous detection result.

Abstract: A video coding apparatus comprises a motion prediction unit configured to perform motion prediction for a plurality of coding unit sizes of an original image serving as the picture of an input video signal and evaluate results obtained by the motion prediction for the coding unit sizes so as to supply a first evaluation value; a merge mode evaluation unit configured to evaluate each of merge candidates on a coding unit of the merge size determined by a merge size determination unit so as to supply a second evaluation value of each of the merge candidates; and an inter-prediction mode determination unit configured to determine a mode used for coding on the basis of the second evaluation value obtained by the merge mode evaluation unit and the first evaluation value of the coding unit sizes.

Abstract: Before completion of merge encoding processing of an immediately preceding PU, a controller determines the order of evaluation of merge candidates with the immediately preceding PU excluded from the merge candidates to be evaluated, and a merge-candidate derivation part evaluates each merge candidate in the order of evaluation. After the completion of the merge encoding processing of the immediately preceding PU, the controller re-determines the order of evaluation of merge candidates with the immediately preceding PU included in the merge candidates to be evaluated, and the merge-candidate derivation part evaluates each merge candidate in the re-determined order of evaluation excluding the merge candidate whose evaluation has already been started.

Abstract: In a waveguide device, unnecessary optical power is appropriately terminated. According to an embodiment of the present invention, the waveguide device has a termination structure filled with a light blocking material to terminate light from a waveguide end. In the termination structure, a cladding and a core are removed to form a groove on an optical waveguide. The groove is filled with a material (light blocking material) that attenuates the intensity of light. Thus, light input to the termination structure is attenuated by the light blocking material, suppressing crosstalk which possibly effects on other optical devices. Thus, such a termination structure can restrain crosstalk occurred in optical devices integrated in the same substrate and can also suppress crosstalk which possibly effects on any other optical device connected directly to the substrate.

Abstract: A light modulation device detects a power of the modulated optical signal modulated by each of an I-component optical modulator and a Q-component optical modulator, synchronously-detects a component of a frequency fd from the power of the modulated optical signal, outputs a dither signal of a frequency fd/n (where n is a positive integer equal to or larger than 1) applied to a first bias voltage or a second bias voltage when adjusting the first bias voltage or the second bias voltage, outputs two dither signals having a frequency fd/m (where m is a positive integer equal to or larger than 1, where n<m), which are mutually orthogonal to each other, applied to the first and second bias voltages when adjusting a third bias voltage, and adjusting bias voltages by increasing or decreasing bias voltages based on a synchronous detection result.