Abstract: There is provided a communication system, wherein: an optical transmission apparatus has: a first storage unit that stores amplitude distribution information, which is information representing a distribution of occurrence probabilities of symbols of an optical signal, in association with a modulation rate of an optical signal; a control unit that selects the modulation rate based on a signal band that is a band determined by the modulation rate and a device band that is a band in which a transmission path and the like allow passage of an optical signal, and controls an occurrence probability of a symbol of an optical signal based on the amplitude distribution information; and an optical transmitter that transmits an optical signal of a symbol of which the occurrence probability is controlled; and an optical reception apparatus has: an optical receiver that receives an optical signal of a symbol; a second storage unit that stores the amplitude distribution information in association with the modulation rate; a

Abstract: An optical transmission system including an optical transmitter and an optical receiver, wherein the optical transmitter includes a signal coding unit that performs non-linear block coding on an M (M is an integer greater than or equal to 1)-value symbol sequence or a bit sequence input as data information to generate an L (L is an integer greater than or equal to 2, L>M)-value symbol sequence that corresponds to the M-value symbol sequence or the bit sequence in one-to-one correspondence, a digital-to-analog conversion unit that converts the generated L-value symbol sequence to an analog signal, and a modulator that generates an optical modulation signal by performing modulation based on the analog signal, and the optical receiver includes a light receiving unit that receives the optical modulation signal transmitted from the optical transmitter and converts the optical modulation signal to an electrical signal, and a signal decoding unit that restores the M-value symbol sequence or the bit sequence by pe

Abstract: An optical communication system is provided in which a serial/parallel converting unit outputs bit sequences of sequence groups a number of which is determined by a logarithmic value and a bit sequence of a highest-order sequence group, a converting unit converts the bit sequence of the sequence group input to the converting unit into a bit sequence for which a probability of occurrence of 0 or a probability of occurrence of 1 is a predetermined probability of occurrence, a selecting unit acquires a bit sequence for which the probability of occurrence is converted by a converting unit higher in order than the converting unit for the selecting unit, and selects an order of output of a symbol to other selecting units in the sequence groups higher in order than the selecting unit in accordance with the acquired bit sequence, a multiplication unit multiplies a value representing the symbol selected by a highest-order selecting unit, by a number in accordance with the bit sequence of the highest order sequence gro

Abstract: There is provided an optical transmission system in which a plurality of optical transmission and reception apparatuses perform 1-to-N transmission and reception of optical signals (N is an integer equal to or greater than 1), the optical transmission system being configured to select a communication condition that includes at least a modulation scheme or a baud rate and is a communication condition when each of the optical transmission and reception apparatuses performs transmission and reception in accordance with a transmission line condition that is between any one first optical transmission and reception apparatus and each of second optical transmission and reception apparatuses, which are N grounds, other than the first optical transmission and reception apparatus.

Abstract: An optical transmission system including an optical transmission device and an optical reception device that receives, via an optical transmission line, a signal transmitted from the optical transmission device, the optical transmission system including a transmission-mode selection unit that selects transmission mode information in descending order of priority out of transmission mode information, which is combinations of a plurality of parameters concerning transmission performance, the transmission mode information being a plurality of kinds of the transmission mode information common to the transmission performance of the optical transmission device and the optical reception device, a signal transmission unit that transmits, to the optical reception device, a signal modulated based on the selected transmission mode information, and a signal reception unit that receives the signal and modulates the received signal based on the transmission mode information selected by the transmission-mode selection unit.

Abstract: A reception apparatus includes a dispersion compensation unit configured to acquire an electrical signal resulting from conversion of an optical signal and perform, on the electrical signal, dispersion compensation with a predetermined compensation amount, a clip rate measurement unit configured to measure a clip rate for the electrical signal subjected to the dispersion compensation, and a control unit configured to detect the compensation amount that minimizes the clip rate.

Abstract: A digital coherent receiver includes: an adaptive equalizer configured to execute, using a first tap coefficient, adaptive equalization processing on a digital signal that corresponds to a signal; a first coefficient updating unit configured to update the first tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a first step size; a second coefficient updating unit configured to update a second tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a second step size; and a control unit configured to detect a fluctuation speed of a state of polarization of the digital signal based on the second tap coefficient, and change the first tap coefficient to the updated second tap coefficient if it is determined that the fluctu

Abstract: An optical transmission system includes an optical transmitter, an optical receiver, and a control apparatus. The control apparatus repeatedly performs an adjustment process for adjusting power of an optical signal of a frequency band to be adjusted while switching the frequency band to be adjusted between at least two frequency bands including at least a frequency band where stimulated Raman scattering occurs among frequency bands that are multiplexed in a multiplexed optical signal transmitted by the optical transmission system. In the adjustment process, when power of an optical signal of the frequency band to be adjusted transmitted from the optical transmitter has been changed, the control apparatus determines the power of the optical signal of the frequency band to be adjusted on the basis of a signal quality measured by the optical receiver that has received the optical signal.

Abstract: A signal processing device includes a distributing unit and a plurality of correcting units with different processing performance, the distributing unit distributes a bit sequence having a first number of bits to the first correcting unit, and a bit sequence having a second number of bits less than the first number of bits to the second correcting unit having lower processing performance than the first correcting unit, the first correcting unit applies error correction processing to the bit sequence having the first number of bits distributed to the first correcting unit, and the second correcting unit applies error correction processing to the bit sequence having the second number of bits distributed to the second correcting unit.

Abstract: A pressing surface of a hammer and a to-be-pressed surface of a key switch have relatively-concaved shapes in a longitudinal direction of the hammer. When a switch body is pressed by the hammer, an inclination caused by an overall curvature of the switch body that results from the fact that the switch body is pressed by the hammer from an oblique direction is canceled by an inclination of the switch body caused by partial compression and deformation that results from the relatively-concaved shapes, so that movable contacts in the switch body frontally face stationary contacts and come into contact with the stationary contacts, respectively.

Abstract: There is provided an optical transmission system in which a plurality of optical transmission and reception apparatuses perform 1-to-N transmission and reception of optical signals (N is an integer equal to or greater than 1), the optical transmission system being configured to select a communication condition that includes at least a modulation scheme or a baud rate and is a communication condition when each of the optical transmission and reception apparatuses performs transmission and reception in accordance with a transmission line condition that is between any one first optical transmission and reception apparatus and each of second optical transmission and reception apparatuses, which are N grounds, other than the first optical transmission and reception apparatus.

Abstract: A state estimating device includes a pre-processing unit and an estimating unit. The pre-processing unit acquires data representing at one or more of a phase of a signal transmitted from a transmission unit of a transmission device and received at a reception unit of another transmission device via a transmission path, a reception strength, a reception quality, a voltage after conversion into an electric signal, and a signal processing parameter used in reception processing, and processes the acquired data into feature data to be used for state estimation. The estimating unit estimates a state of the transmission path, an abnormal state of the transmission unit, or an abnormal state of the reception unit, on the basis of the feature data.

Abstract: A signal-to-noise ratio (SNR) estimation method includes an optical signal transmission step of inserting at least one pair of signal sequences into transmission data and transmitting the transmission data into which the at least one pair of signal sequences is inserted, a signal sequence extraction step of extracting the at least one pair of signal sequences from a received signal obtained by receiving the transmitted transmission data, an inner product calculation step of calculating an inner product value of the extracted at least one pair of signal sequences, a reception power calculation step of calculating reception power of the extracted at least one pair of signal sequences, and an SNR calculation step of calculating an SNR of the at least one pair of signal sequences on the basis of the calculated inner product value and the calculated reception power.

Abstract: An optical receiver that demodulates an optical modulation signal into a baseband signal, which is an electrical signal, and decodes a received symbol acquired by converting the baseband signal. The optical receiver includes: an analog-to-digital converter that converts the baseband signal into a digital signal of which the number of samples per received symbol is M/N (samples/symbol), M and N being positive integers, M/N being not an integer, and “M>N” being satisfied; and an adaptive equalization processing unit that executes an equalization operation set in advance to output the received symbol on the basis of the digital signal of which the number of samples per received symbol is M/N (samples/symbol) and a predetermined tap coefficient digital signal equalization tap coefficients used for equalization of a signal, the coefficient being updated in any sampling period.

Abstract: A pressing surface of a hammer and a to-be-pressed surface of a key switch have relatively-concaved shapes in a longitudinal direction of the hammer. When a switch body is pressed by the hammer, an inclination caused by an overall curvature of the switch body that results from the fact that the switch body is pressed by the hammer from an oblique direction is canceled by an inclination of the switch body caused by partial compression and deformation that results from the relatively-concaved shapes, so that movable contacts in the switch body frontally face stationary contacts and come into contact with the stationary contacts, respectively.

Abstract: An optical transmitter of an optical data transmission system transmitting data through an optical fiber transmission path includes a main signal generator that converts first transmission data into a predetermined signal format to generate a first signal, a DCSK modulator that DCSK-modulates second transmission data to generate a second signal, a signal-multiplexer that performs time-division multiplexing of the first signal and the second signal, and an electro-optical converter that converts a multiplexed signal obtained by the time-division multiplexing of the signal-multiplexer from an electric signal into an optical signal, and outputs the optical signal to the optical fiber transmission path.

Abstract: An optical receiver that demodulates an optical modulation signal into a baseband signal, which is an electrical signal, and decodes a received symbol acquired by converting the baseband signal. The optical receiver includes: an analog-to-digital converter that converts the baseband signal into a digital signal of which the number of samples per received symbol is M/N (samples/symbol), M and N being positive integers, M/N being not an integer, and “M >N” being satisfied; and an adaptive equalization processing unit that executes an equalization operation set in advance to output the received symbol on the basis of the digital signal of which the number of samples per received symbol is M/N (samples/symbol) and a predetermined tap coefficient digital signal equalization tap coefficients used for equalization of a signal, the coefficient being updated in any sampling period.

Abstract: A signal-to-noise ratio (SNR) estimation method includes an optical signal transmission step of inserting at least one pair of signal sequences into transmission data and transmitting the transmission data into which the at least one pair of signal sequences is inserted, a signal sequence extraction step of extracting the at least one pair of signal sequences from a received signal obtained by receiving the transmitted transmission data, an inner product calculation step of calculating an inner product value of the extracted at least one pair of signal sequences, a reception power calculation step of calculating reception power of the extracted at least one pair of signal sequences, and an SNR calculation step of calculating an SNR of the at least one pair of signal sequences on the basis of the calculated inner product value and the calculated reception power.

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: An optical transmitter of an optical data transmission system transmitting data through an optical fiber transmission path includes a main signal generator that converts first transmission data into a predetermined signal format to generate a first signal, a DCSK modulator that DCSK-modulates second transmission data to generate a second signal, a signal-multiplexer that performs time-division multiplexing of the first signal and the second signal, and an electro-optical converter that converts a multiplexed signal obtained by the time-division multiplexing of the signal-multiplexer from an electric signal into an optical signal, and outputs the optical signal to the optical fiber transmission path.