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 broadband optical wavelength multiplexer/demultiplexer is provided. Two waveguides are arranged such that, in a case where a connection position where one of the two waveguides is connected to a first slab waveguide is set closer to the other waveguide by a channel frequency interval ?f, a central position between the two waveguides aligns with a central position on a connection end surface of the first slab waveguide, and two waveguide groups of an output waveguide are arranged such that a central position between the two waveguide groups aligns with a central position of a second slab waveguide, and an interval between a connection position where the other waveguide is connected to the first slab waveguide and the central position on the connection end surface of the first slab waveguide is set equal to an interval between a connection position where the waveguide groups are connected to the second slab waveguide.

Abstract: An optical circuit board which is mounted with a loop-back circuit for returning aligning light to the fiber array in the vicinity of the fiber array connection end. Since an aligning loop-back circuit can be formed in an optical waveguide pattern, a production cost does not increase in comparison to an optical circuit board of the related art. The aligning light combined from the optical fiber to the aligning port of the optical circuit board is returned to the optical fiber around the loop-back circuit. Therefore, it is possible to perform alignment using the returned light. That is, alignment can be performed while being mounted on a package without installing a light-reflecting film or mirror.

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 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: An amplifier typically exemplified by a TIA is realized that provides an optimal band characteristic, that reduces the possibility of the oscillation, and that achieves a reduced dispersion of the band characteristics. An amplifier for amplifying an electric signal, comprising: a first buffer for amplifying the electric signal; a filter that is connected to an output of the first buffer and that includes a parallel circuit consisting of an inductor and a first capacity; and a second buffer connected to an output of the filter.

Abstract: A processing equipment includes a processing unit having a plurality of functions. A retaining unit retains a device identifier capable of identifying the processing equipment. An interface unit receives a function authentication key which is a code for setting a specific function among the plurality of functions to be enabled or disabled. A control unit sets the specific function to be enabled or disabled according to the function authentication key when a device identifier included in the received function authentication key coincides with the device identifier retained in the retaining unit.

Abstract: An optical module that is connectable to an optical fiber array and that can be packaged in a high density. Two package modules are mounted on a board, and optical waveguides in a Si photonic lightwave circuit mounted on the package module are connected to an optical fiber array fixed to an optical fiber block. Moreover, output end surfaces of the optical waveguides in the Si photonic lightwave circuit are perpendicular to a mount surface of the package module. The optical waveguides in the Si photonic lightwave circuit may be tilted at an appropriate angle with respect to a direction perpendicular to a right end surface. Moreover, the optical fiber block fixes optical fibers with the optical fibers tilted with respect to a direction perpendicular to an end surface connected to the Si photonic lightwave circuit.

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 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.

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: 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.

Abstract: A Fourier-transformer performs Fourier transform on a filter coefficient output from an adaptive equalizer which comprises a finite impulse response filter of N taps (N represents an integer of 2 or more) in a time direction. An eigenvalue sum calculator integrates a frequency-differentiation result of the Fourier-transformed filter coefficient and a complex conjugate of the Fourier-transformed filter coefficient to calculate a matrix, and calculates a sum of two eigenvalues of the matrix. A proportionality factor calculator calculates a proportionality factor for frequency from the sum of the two eigenvalues.

Abstract: A symbol phase difference compensating portion (6) 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 (12) tentatively determines an output signal of the symbol phase difference compensating portion (6) to acquire an estimated value of a phase. A first phase difference acquiring portion (13) 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 (12). A first phase difference compensating portion (14) performs phase compensation for the output signal based on the second phase difference.

Abstract: In a method in which a compensation coefficient calculating portion (6) calculates a compensation coefficient of a compensation portion (5) 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.

Abstract: A position coordinate difference computing unit (5a to 5c) calculates position coordinate differences between position coordinates of the output digital signals and position coordinates of the input digital signals adjacent to the position coordinates. An FIR coefficient memory (13a to 13c) stores FIR coefficients of an FIR-LPF and outputs FIR coefficients corresponding to position coordinate differences between a fixed number of the output digital signals adjacent to the position coordinates of the output digital signals and the output digital signals. A control unit (11) supplies a group of the FIR coefficients and a group of the input digital signals corresponding to the respective position coordinate differences to the parallel FIR calculator (4) in predetermined order when the position coordinate differences corresponding to two or more different output digital signals are concurrently computed.

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: 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.