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 transmission system, in which an optical transmission apparatus and an optical reception apparatus are provided, includes a coefficient determination unit configured to optimize, based on a reception signal received by the optical reception apparatus, a coefficient to be used to compensate for deterioration according to characteristics of each device configuring a transmission path between the optical transmission apparatus and the optical reception apparatus, and a device characteristic estimation unit configured to estimate the characteristics of each device by using the optimized coefficient.

Abstract: A pump light generation unit of an optical amplifier pumping device outputs pump light with a single wavelength or a plurality of wavelengths from a plurality of output ports. A pump light multiplexing unit polarization-multiplexes or wavelength-multiplexes the plurality of pieces of pump light which has been output from the pump light generation unit. A polarization scrambler collectively polarization-scrambles the polarization-multiplexed or wavelength-multiplexed pump light which has been output from the pump light multiplexing unit and outputs the polarization-scrambled pump light to an optical waveguide for pump light. The optical waveguide for pump light inputs the pump light which has been polarization-multiplexed or wavelength-multiplexed by the pump light multiplexing unit to the pump light superimposition unit. A pump light superimposition unit multiplexes the polarization-multiplexed or wavelength-multiplexed pump light and signal light.

Abstract: A tentative decision is made for symbols on the basis of a received signal and a decision threshold, and a tentative decision signal including a sequence of the symbols is output. A scale value indicating a rate of increase or reduction of the received signal or a threshold change rate indicating a degree of change in the decision threshold is updated so that an appearance frequency of each of symbols included in the tentative decision signal matches an appearance frequency of each of symbols in a reference signal obtained by modulating a transmitted signal with a modulation method used in transmission which is shared between a transmitting side and a receiving side, and an SN ratio is calculated using the scale value or the threshold change rate when a degree of agreement between the appearance frequencies is within a predetermined permissible range.

Abstract: A depolarizer for depolarizing input light having a plurality of linearly polarized waves whose optical frequency interval is f includes: an input optical waveguide configured to propagate the input light while maintaining linear polarization; a first polarization-maintaining coupler configured to bifurcate the linearly polarized waves output from the input optical waveguide to a first arm and a second arm while maintaining a polarization state; a second polarization-maintaining coupler configured to polarization-multiplex and output the linearly polarized waves propagated through the first arm and the second arm; and a polarization-maintaining variable optical delay line arranged on at least one of the first arm or the second arm, in which the variable optical delay line is adjusted such that a difference in delay time between the linearly polarized waves propagated through the first arm and the second arm becomes close to (n+0.5)/f where n is an arbitrary integer.

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: An optical transmitter generates symbols for transmission by applying a predetermined coding method to each of m-valued transmission symbols generated from transmission data, generates signal light by performing optical modulation on the basis of the symbols for transmission, and transmits the signal light. An optical receiver generates a series of digital signals from the received signal light, detects coded symbols by applying predetermined digital signal processing to the series of digital signals, decodes the m-valued transmission symbols from the detected coded symbols, and restores the transmission data from the decoded m-valued transmission symbols.

Abstract: Provided is a first bias power source that generates a first data bias voltage to be applied to an optical modulation unit for the I component, a second bias power source that generates a second data bias voltage to be applied to an optical modulation unit for the Q component, and a third bias power source that generates a quadrature bias voltage to be applied to an optical phase shifter, a data bias voltage adjustment unit that applies a feedback control to each of the first bias power source and the second bias power source, and a quadrature bias voltage adjustment unit that determines whether or not the quadrature bias voltage is optimal on a basis of a second optical QAM signal generated by an IQ optical modulator, and applies a feedback control to the third bias power source, in which a first optical QAM signal and the second optical QAM signal are generated by the IQ optical modulator but the optical phase difference between an optical electric field EI and an optical electric field EQ differs by ?.

Abstract: The symbol determination device generates the plurality of estimated reception symbol sequences on the basis of the estimated transfer function of the transmission line represented by the tap gain value applied to each tap of the nonlinear filter including the plurality of taps and the plurality of candidate symbol sequences, determines the transmission symbol by the maximum likelihood sequence estimation on the basis of the determination target reception symbol sequence obtained from the reception signal sequence and each of the plurality of estimated reception symbol sequences, identifies the estimated transmission symbol corresponding to the determination target reception symbol sequence, calculates the new tap gain values on the basis of the determination target reception symbol sequence and the identified estimated transmission symbol sequence, updates the estimated transfer function by applying the calculated tap gain values to the taps of the transmission line estimation unit, and selects the tap to be

Abstract: An optical transmission system is an optical transmission system for transmitting a signal from an optical transmitter to an optical receiver via at least a transmission line among one or more optical nodes and the transmission line, wherein the optical transmitter includes a digital filter that compensates for, between ripple components that are micro-fluctuating components in a frequency region representing a transmission characteristic of the signal in the optical transmitter and the optical receiver and non-ripple components of the transmission characteristic, at least the ripple components of the transmission characteristic, and at least one of the optical node and the optical transmitter includes an optical filter that compensates for the non-ripple components of the transmission characteristic.

Abstract: According to an aspect of the present invention, there is provided an optical signal demodulator including an optical reception unit, an AD conversion unit, a digital signal processing unit, and a signal determination unit, in which the signal determination unit includes: a spectrum shaping filter processing unit that receives a reception signal sequence of the digital signal from the digital signal processing unit and outputs a value obtained by performing a convolution operation on the reception signal sequence which is received; a transmission line simulation filter processing unit that outputs a value obtained by performing a convolution operation on a candidate signal sequence which is determined based on a symbol transition of the reception signal; an error information acquisition unit that acquires error information between the value output from the spectrum shaping filter processing unit and the value output from the transmission line simulation filter processing unit; and a bit determination unit tha

Abstract: A synchronization detection device includes: a correction unit configured to correct sampled data of a waveform on which a dither signal is superimposed, for each period of a reference signal in accordance with a period of the dither signal; a multiplication unit configured to multiply the corrected sampled data by a weight coefficient that is different for each level of the reference signal and associated with a timing of the reference signal; and an averaging unit configured to derive, as a detection result, an average of a result of the multiplication of the corrected sampled data by the weight coefficient.

Abstract: An optical transmission system according to an embodiment includes: an optical transmission unit which modulates an optical signal into which a known signal is inserted and transmits the optical signal; and an optical reception unit which receives the optical signal from the optical transmission unit, wherein the optical reception unit includes: an optical receiver which performs coherent detection of a reception signal of the optical signal received from the optical transmission unit; a receiver transfer function estimation section which estimates a nonlinear response transfer function of the optical receiver based on the known signal included in the reception signal after the detection by the optical receiver; and a receiver compensation section which compensates nonlinear distortion of the reception signal after the detection based on the nonlinear response transfer function which the receiver transfer function estimation section estimates.

Abstract: A device generates a symbol sequence by performing adaptive equalization by an estimation inverse transfer function of a transmission line on a reception signal sequence extracted from the transmission line, and performing provisional determination on the symbol sequence generated; generates a plurality of the symbol sequences indicating transmission line states in a range of a provisional determination symbol provisionally determined and nearby symbols of the provisional determination symbol; generates, based on the plurality of the symbol sequences indicating the transmission line states generated and an estimation transfer function of the transmission line, an estimation reception symbol sequence for each of the transmission line states; calculates a metric between the symbol sequence obtained from the reception signal sequence and each of a plurality of the estimation reception symbol sequences; selects a most likelihood estimation reception symbol sequence of the plurality of the estimation reception sym

Abstract: An electric digital received signal obtained from a received optical signal is segmented into blocks of a certain length with an overlap of a length determined in advance with an adjacent block. Fourier transformation is performed for each of the blocks. The blocks subjected to the Fourier transformation are stored consecutively in time series, a coefficient determined based on a wavelength dispersion compensation amount according to one of frequency positions and a delay amount according to one of the frequency positions and one of time positions is applied to each of frequency component values included in a plurality of the stored blocks, and the blocks to which the coefficient has been applied and which are obtained by adding up the frequency component values to which the coefficient has been applied for each of the frequency positions are generated. Inverse Fourier transformation is performed on the generated blocks to which the coefficient has been applied.

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: An optical transmission system, in which an optical transmission apparatus and an optical reception apparatus are provided, includes a coefficient determination unit configured to optimize, based on a reception signal received by the optical reception apparatus, a coefficient to be used to compensate for deterioration according to characteristics of each device configuring a transmission path between the optical transmission apparatus and the optical reception apparatus, and a device characteristic estimation unit configured to estimate the characteristics of each device by using the optimized coefficient.

Abstract: A tentative decision is made for symbols on the basis of a received signal and a decision threshold, and a tentative decision signal including a sequence of the symbols is output. A scale value indicating a rate of increase or reduction of the received signal or a threshold change rate indicating a degree of change in the decision threshold is updated so that an appearance frequency of each of symbols included in the tentative decision signal matches an appearance frequency of each of symbols in a reference signal obtained by modulating a transmitted signal with a modulation method used in transmission which is shared between a transmitting side and a receiving side, and an SN ratio is calculated using the scale value or the threshold change rate when a degree of agreement between the appearance frequencies is within a predetermined permissible range.

Abstract: An optical transmitter generates symbols for transmission by applying a predetermined coding method to each of m-valued transmission symbols generated from transmission data, generates signal light by performing optical modulation on the basis of the symbols for transmission, and transmits the signal light. An optical receiver generates a series of digital signals from the received signal light, detects coded symbols by applying predetermined digital signal processing to the series of digital signals, decodes the m-valued transmission symbols from the detected coded symbols, and restores the transmission data from the decoded m-valued transmission symbols.

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