Abstract: Provided an optical transmission characteristic estimation device that models an optical effect of an optical transmission line by a nonlinear Schrodinger equation, divides the optical transmission line into N (N is an integer of two or more) sections, obtains a solution of the nonlinear Schrodinger equation by an operation of N steps in which a section length of each of the divided N sections is a step size, and estimates transmission characteristics of the optical transmission line, the optical transmission characteristic estimation device including a step size update unit configured to update each of the N step sizes on the basis of an estimated optical power distribution and an estimated dispersion distribution, which are indicated by the transmission characteristics.

Abstract: A communication method in a communication system including an optical transmission device and an optical reception device includes: detecting wave-front distortions of a reference optical signal used for wave-front observation which arrives at a first time point and a second time point before a compensation start time point at which compensation for wave-front distortion is performed, by a plurality of sensors; estimating spatial phase distributions of a plurality of atmospheric layers between the optical transmission device and the optical reception device, respectively, at the first time point and the second time point, based on the wave-front distortions detected by the plurality of sensors, respectively; predicting the respective spatial phase distributions of the plurality of atmospheric layers at the compensation start time point by using estimation results of the respective spatial phase distributions of the plurality of atmospheric layers estimated at the first time point and the second time point; co

Abstract: A gain adjustment method in an optical transmission system that performs communication by a digital coherent system including an optical transmission device and an optical reception device includes converting an optical signal transmitted from the optical transmission device into an electrical signal, converting the electrical signal from an analog signal to a digital signal, performing first signal processing on the digital signal, performing adaptive equalization processing on the digital signal subjected to the first signal processing using a digital filter, correcting an amplitude of an output signal of the digital filter based on information of the amplitude and a phase of the output signal of the digital filter and the amplitude of a known transmission signal, and performing second signal processing on the output signal of the digital filter whose amplitude has been corrected.

Abstract: An aspect of the present invention is an adaptive equalization filter for an optical transmission system, including: a main signal filter; and a coefficient computation unit that updates the filter coefficient of the main signal filter. The pre-stage filter and the post-stage filter receive a sample of the main signal as an input. The pre-stage coefficient computation unit obtains the filter coefficient of the pre-stage filter by feedback control using the gradient method. The post-stage coefficient computation unit obtains the filter coefficient of the post-stage filter by feedforward control. The convolution computation unit obtains the filter coefficient of the main signal filter by convolution computation of the filter coefficient of the pre-stage filter obtained by the pre-stage coefficient computation unit and the filter coefficient of the post-stage filter obtained by the post-stage coefficient computation unit.

Abstract: A switching instructor outputs a beacon light selection notification signal when a optical transceiver transmits a optical wireless signal of a beacon light and outputs a signal light selection notification signal when the optical transceiver transmits the optical wireless signal of the signal light. A spatial light modulator controller performs switching of a control signal given to each of the plurality of pixels of a spatial light modulator to: cause a phase delay in light received by each of the plurality of pixels of the spatial light modulator when the switching instructor outputs the beacon light selection notification signal and cause a phase delay in light received by each of the plurality of pixels of the spatial light modulator when the switching instructor outputs the signal light selection notification signal.

Abstract: A communication device includes: a light output unit for outputting light; a light splitting unit for splitting the light output by the light output unit into a plurality of split beams; and a plurality of spatial optical communication units provided in correspondence to the plurality of split beams, wherein the spatial optical communication units respectively transmit a corresponding split beam which is input from the light splitting unit to a partner communication device across space.

Abstract: A phase difference distribution estimation method includes: receiving an optical signal via a space and detecting a phase of the optical signal; calculating characteristic values related to characteristics of the atmosphere through which the optical signal propagates from the optical signal received in the receiving; estimating a phase difference distribution of an optical signal received after a certain period of time, on the basis of the characteristic values calculated in the calculating; and controlling a phase of an optical signal in the receiving on the basis of the phase difference distribution estimated in the estimating.

Abstract: In an optical wireless communication system including: an optical wireless communication apparatus that moves along with a first optical wireless station; and a second optical wireless station opposed to the first optical wireless station, the optical wireless communication apparatus includes at least one reference light transmitting unit that transmits reference light to the second optical wireless station with a position in front in a moving direction of the first optical wireless station defined as a transmission position, the second optical wireless station includes a reference light receiving unit that receives the reference light transmitted from the at least one reference light transmitting unit, an estimation unit that estimates an influence of atmospheric air on transmission of signal light based on a reception state of the reference light received by the reference light receiving unit, a compensation unit that performs compensation processing on the signal light based on the influence of the atmosph

Abstract: A transmission apparatus causes a digital-to-analog conversion unit to perform digital-to-analog conversion on transmission signals pre-equalized by using a compensation filter, then converts electrical signals into optical signals, and outputs the optical signals. A receiving apparatus converts the received optical signals into received electrical signals, then performs analog-to-digital conversion, and demodulates the received signals. A scale estimation unit calculates a slope near an amplitude 0 in a correlation between an amplitude distribution of the pre-equalized transmission signals and an amplitude distribution of the received signals. A scale unit scales amplitude of the received signals on the basis of the calculated slope. A coefficient estimation unit calculates a filter coefficient of the compensation filter on the basis of the pre-equalized transmission signals and the scaled received signals.

Abstract: A frequency offset estimation device includes a correlation processing unit that obtains a correlation pattern that is a waveform pattern indicating a correlation between a reception signal spectrum and a detection pattern based on a power spectrum of the reception signal or the reception signal spectrum indicating an amplitude spectrum based on the power spectrum and the detection pattern that is a predetermined waveform pattern, and an estimation unit that estimates a frequency offset amount based on a peak position of the correlation pattern obtained by the correlation processing unit.

Abstract: According to an aspect of the present invention, an optical signal control apparatus controls a compensation coefficient of an equalizer of an optical transmitter including the equalizer of a symbol period interval and a digital-to-analog converter (DAC) operating at a symbol period interval sampling rate and having a sampling phase adjustment function, and the sampling phase of the DAC. The optical signal control apparatus includes a skew calculation unit configured to calculate a sampling phase amount from a group delay difference between an in-phase component and a quadrature component based on characteristic information of a device and a transmission path and to output the calculated sampling phase amount to the DAC and a compensation coefficient calculation unit configured to calculate the compensation coefficient in which a phase characteristic of a Nyquist frequency of the DAC is 0 or an integer multiple of ? and to output the calculated compensation coefficient to the equalizer.

Abstract: An optical signal emitting direction control method of a present embodiment includes arranging a transparent member to extend over an underwater space and an in-air space, causing an optical signal to enter the transparent member from the underwater space via a surface of an underwater portion of the transparent member immersed in the underwater space, and causing the optical signal entered the transparent member to be emitted into the in-air space via a surface of an in-air portion of the transparent member exposed to the in-air space.

Abstract: An aspect of the present invention is a wireless communication device including a water flow generator that controls a shape of a partial region on a water surface, and an emission unit that emits a wave carrying information toward the region.

Abstract: An aspect of the present invention is an adaptive equalization filter for an optical transmission system, including: a main signal filter; and a coefficient computation unit that updates the filter coefficient of the main signal filter. The pre-stage filter and the post-stage filter receive a sample of the main signal as an input. The pre-stage coefficient computation unit obtains the filter coefficient of the pre-stage filter by feedback control using the gradient method. The post-stage coefficient computation unit obtains the filter coefficient of the post-stage filter by feedforward control. The convolution computation unit obtains the filter coefficient of the main signal filter by convolution computation of the filter coefficient of the pre-stage filter obtained by the pre-stage coefficient computation unit and the filter coefficient of the post-stage filter obtained by the post-stage coefficient computation unit.

Abstract: A signal processing apparatus includes: a coefficient update unit configured to approximate a characteristic of a transmission line of an optical signal by a first tap coefficient vector of which an L0 norm is a predetermined value or less; a zeroing unit configured to generate a second tap coefficient vector by replacing, with 0, a tap coefficient of which an absolute value is less than a threshold among tap coefficients of the first tap coefficient vector; and an adaptive filter configured to perform, based on the second tap coefficient vector, adaptive equalization processing on a digital signal corresponding to an optical signal received via the transmission line.

Abstract: A phase difference distribution estimation method includes: receiving an optical signal via a space and detecting a phase of the optical signal; calculating characteristic values related to characteristics of the atmosphere through which the optical signal propagates from the optical signal received in the receiving; estimating a phase difference distribution of an optical signal received after a certain period of time, on the basis of the characteristic values calculated in the calculating; and controlling a phase of an optical signal in the receiving on the basis of the phase difference distribution estimated in the estimating.

Abstract: A communication device includes: a light output unit for outputting light; a light splitting unit for splitting the light output by the light output unit into a plurality of split beams; and a plurality of spatial optical communication units provided in correspondence to the plurality of split beams, wherein the spatial optical communication units respectively transmit a corresponding split beam which is input from the light splitting unit to a partner communication device across space.

Abstract: A switching instructor outputs a beacon light selection notification signal when a optical transceiver transmits a optical wireless signal of a beacon light and outputs a signal light selection notification signal when the optical transceiver transmits the optical wireless signal of the signal light. A spatial light modulator controller performs switching of a control signal given to each of the plurality of pixels of a spatial light modulator to: cause a phase delay in light received by each of the plurality of pixels of the spatial light modulator when the switching instructor outputs the beacon light selection notification signal and cause a phase delay in light received by each of the plurality of pixels of the spatial light modulator when the switching instructor outputs the signal light selection notification signal.

Abstract: In an optical wireless communication system including: an optical wireless communication apparatus that moves along with a first optical wireless station; and a second optical wireless station opposed to the first optical wireless station, the optical wireless communication apparatus includes at least one reference light transmitting unit that transmits reference light to the second optical wireless station with a position in front in a moving direction of the first optical wireless station defined as a transmission position, the second optical wireless station includes a reference light receiving unit that receives the reference light transmitted from the at least one reference light transmitting unit, an estimation unit that estimates an influence of atmospheric air on transmission of signal light based on a reception state of the reference light received by the reference light receiving unit, a compensation unit that performs compensation processing on the signal light based on the influence of the atmosph

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.