Abstract: An optical transmission apparatus and an optical transmission method are provided. In particular, an optical transmission apparatus is disclosed as being configured to add strength to a signal. The signal corresponds to a value that an input signal has, and the strength added to the signal is strength according to the value. The optical transmission apparatus is further configured to give delays to a plurality of signals that includes the signal and to convert the sum of the plurality of signals into an optical signal.

Abstract: An optical transmission apparatus and an optical transmission method are provided. In particular, an optical transmission apparatus is disclosed as being configured to add strength to a signal. The signal corresponds to a value that an input signal has, and the strength added to the signal is strength according to the value. The optical transmission apparatus is further configured to give delays to a plurality of signals that includes the signal and to convert the sum of the plurality of signals into an optical signal.

Abstract: A receiving device includes an optical filter, an acquisition unit, a first determination unit, and a filter setting unit. The optical filter transmits an optical DMT signal received from a sending device. The acquisition unit acquires the transmission characteristics of the optical DMT signal received from the sending device. The first determination unit determines a filter frequency of the optical filter that removes a dip from the optical DMT signal on the basis of the acquired transmission characteristics. The filter setting unit sets the determined filter frequency in the optical filter.

Abstract: A method for estimating characteristics of an optical receiver includes: a generating process, a monitoring process, a suppressing process, a guiding process and an estimating process. The generating process generates a modulated optical signal based on an oscillation signal. The monitoring process monitors an optical spectrum of the modulated optical signal or a spectrum of an electric signal obtained by performing optical-to-electrical conversion on the modulated optical signal. The suppressing process suppresses a modulation component of an upper sideband or a lower sideband of the modulated optical signal based on the optical spectrum of the modulated optical signal or the spectrum of the electric signal. The guiding process guides the modulated optical signal in which the modulation component is suppressed to the optical receiver. The estimating process estimates the characteristics of the optical receiver based on an output signal of the optical receiver.

Abstract: There is provided a transmission apparatus includes: a first modulator configured to modulate a first electrical signal to a second electrical signal that is a multicarrier signal including a plurality of subcarriers to which transmission capacities are allocated, respectively; a light source configured to generate light having a predetermined wavelength; a second modulator configured to modulate the light generated by the light source to an optical signal, based on the second electrical signal modulated by the first modulator; and a processor configured to: measure a first frequency distribution of intensity of the second electrical signal modulated by the first modulator, measure a second frequency distribution of intensity of the optical signal modulated by the second modulator, compare the first frequency distribution and the second frequency distribution, and control modulation characteristics of the second modulator according to a result of comparing the first frequency distribution and the second frequ

Abstract: An optical reception apparatus may include a receiver, a monitor, and a controller. The optical reception apparatus receives multi-carrier modulated signal light modulated by a multi-carrier modulation scheme. The multi-carrier modulation scheme is available to allocate different transmission conditions for each of a plurality of subcarriers in accordance with transmission characteristics of the subcarriers. The receiver may receive from an optical transmission line a training signal light allocated with the same transmission conditions for each of the subcarriers. The monitor may monitor the transmission characteristics of the training signal light to detect a frequency at which a dip of the transmission characteristics occurs. The controller may control, based on the frequency detected by the monitor, a dispersion compensation for the multi-carrier modulated signal light having received a dispersion from the optical transmission line.

Abstract: An optical transmitter includes an optical modulator to modulate light having a predetermined wavelength into an optical signal based on a data signal, a memory, and a processor coupled to the memory and the processor configured to modulate an input signal into a multi-carrier signal so as to generate the data signal, the multi-carrier signal including a plurality of subcarriers each to which a transmission capacity is allocated, acquire a first frequency distribution of an intensity of the multi-carrier signal, acquire a second frequency distribution of an intensity of the optical signal, control the modulating of the input signal into the multi-carrier signal to change a number of subcarriers of the multi-carrier signal, and control the optical modulator to adjust a modulation characteristic of the optical modulator so that a divergence between the first frequency distribution and the second frequency distribution is equal to or less than a predetermined value.

Abstract: An apparatus includes a receiver configured to receive a signal that has traveled an optical transmission line without returning output from an optical transmitting device and synchronize with the optical transmitting device in order to demodulate the signal; a dispersion compensator configured to compensate for wavelength dispersion caused by transmission of the signal; an acquisition circuit configured to acquire a transmitting timing at which the signal has been transmitted from the optical transmitting device; a calculation circuit configured to calculate a transmission time period from the optical transmitting device to the receiver from the transmitting timing and a receiving timing at which the signal has been received with the receiver; and an amount setting circuit configured to adjust a dispersion compensation amount of the dispersion compensator in accordance with the transmission time period.

Abstract: A transmission apparatus including: a waveform shaper that performs spectrum correction on an optical signal converted from an electrical signal encoded by OFDM (Orthogonal Frequency Division Multiplexing); a converter that converts the optical signal on which the waveform shaper has performed the spectrum correction, into the electrical signal; and a nonlinear compensator that compensates for a nonlinear distortion with respect to the electrical signal converted by the converter.

Abstract: An optical transmitter includes an optical modulator to modulate light having a predetermined wavelength into an optical signal based on a data signal, a memory, and a processor coupled to the memory and the processor configured to modulate an input signal into a multi-carrier signal so as to generate the data signal, the multi-carrier signal including a plurality of subcarriers each to which a transmission capacity is allocated, acquire a first frequency distribution of an intensity of the multi-carrier signal, acquire a second frequency distribution of an intensity of the optical signal, control the modulating of the input signal into the multi-carrier signal to change a number of subcarriers of the multi-carrier signal, and control the optical modulator to adjust a modulation characteristic of the optical modulator so that a divergence between the first frequency distribution and the second frequency distribution is equal to or less than a predetermined value.

Abstract: There is proved an optical transmission system including: a transmitter configured to transmit an optical signal modulated with a discrete multi-tone (DMT) drive signal; a filter capable of changing a wavelength of the optical signal input from the transmitter; a monitor configured to monitor a power of the optical signal passed through the filter; and at least one processor configured to: set a center wavelength of the filter, shift the center wavelength, detect a change in the power monitored by the monitor, identify a carrier component of the optical signal based on the change in the power, and control a relative relationship between a transmission characteristic of the filter and a wavelength of the carrier component so that the carrier component is included in the optical signal and one of an upper sideband and a lower sideband of the optical signal is at least partially removed by the filter.

Abstract: A bit allocation method is used in an optical transmission system that transmits multicarrier signals of different wavelengths in wavelength division multiplexing. Frequency characteristics of subcarriers included in the multicarrier signals are different between the respective multicarrier signals. The method includes: measuring transmission characteristics of the subcarriers included in corresponding multicarrier signals at different subcarrier frequencies; and determining a number of bits to be allocated to each of the subcarriers included in each of the multicarrier signals based on the transmission characteristics measured at the different subcarrier frequencies.

Abstract: An apparatus includes a receiver configured to receive a signal that has traveled an optical transmission line without returning output from an optical transmitting device and synchronize with the optical transmitting device in order to demodulate the signal; a dispersion compensator configured to compensate for wavelength dispersion caused by transmission of the signal; an acquisition circuit configured to acquire a transmitting timing at which the signal has been transmitted from the optical transmitting device; a calculation circuit configured to calculate a transmission time period from the optical transmitting device to the receiver from the transmitting timing and a receiving timing at which the signal has been received with the receiver; and an amount setting circuit configured to adjust a dispersion compensation amount of the dispersion compensator in accordance with the transmission time period.

Abstract: A method for estimating characteristics of an optical receiver includes: a generating process, a monitoring process, a suppressing process, a guiding process and an estimating process. The generating process generates a modulated optical signal based on an oscillation signal. The monitoring process monitors an optical spectrum of the modulated optical signal or a spectrum of an electric signal obtained by performing optical-to-electrical conversion on the modulated optical signal. The suppressing process suppresses a modulation component of an upper sideband or a lower sideband of the modulated optical signal based on the optical spectrum of the modulated optical signal or the spectrum of the electric signal. The guiding process guides the modulated optical signal in which the modulation component is suppressed to the optical receiver. The estimating process estimates the characteristics of the optical receiver based on an output signal of the optical receiver.

Abstract: There is provided a transmission apparatus includes: a first modulator configured to modulate a first electrical signal to a second electrical signal that is a multicarrier signal including a plurality of subcarriers to which transmission capacities are allocated, respectively; a light source configured to generate light having a predetermined wavelength; a second modulator configured to modulate the light generated by the light source to an optical signal, based on the second electrical signal modulated by the first modulator; and a processor configured to: measure a first frequency distribution of intensity of the second electrical signal modulated by the first modulator, measure a second frequency distribution of intensity of the optical signal modulated by the second modulator, compare the first frequency distribution and the second frequency distribution, and control modulation characteristics of the second modulator according to a result of comparing the first frequency distribution and the second frequ

Abstract: There is proved an optical transmission system including: a transmitter configured to transmit an optical signal modulated with a discrete multi-tone (DMT) drive signal; a filter capable of changing a wavelength of the optical signal input from the transmitter; a monitor configured to monitor a power of the optical signal passed through the filter; and at least one processor configured to: set a center wavelength of the filter, shift the center wavelength, detect a change in the power monitored by the monitor, identify a carrier component of the optical signal based on the change in the power, and control a relative relationship between a transmission characteristic of the filter and a wavelength of the carrier component so that the carrier component is included in the optical signal and one of an upper sideband and a lower sideband of the optical signal is at least partially removed by the filter.

Abstract: An optical multiplexing includes: a monitor configured to detect power of an optical component including a frequency component of a cross point between spectra of a first sub-carrier signal and a second sub-carrier signal; and a controller configured to control a modulation timing of a data symbol of the second sub-carrier signal according to the power detected by the monitor, wherein the second sub-carrier signal is multiplexed to a carrier to be adjacent to the first sub-carrier signal multiplexed to the carrier so as to generate an optical Orthogonal Frequency Divisional Multiplexing (OFDM) signal in which an interference between the first and second sub-carrier signals is suppressed.

Abstract: A transmission apparatus including: a waveform shaper that performs spectrum correction on an optical signal converted from an electrical signal encoded by OFDM (Orthogonal Frequency Division Multiplexing); a converter that converts the optical signal on which the waveform shaper has performed the spectrum correction, into the electrical signal; and a nonlinear compensator that compensates for a nonlinear distortion with respect to the electrical signal converted by the converter.

Abstract: A bit allocation method is used in an optical transmission system that transmits multicarrier signals of different wavelengths in wavelength division multiplexing. Frequency characteristics of subcarriers included in the multicarrier signals are different between the respective multicarrier signals. The method includes: measuring transmission characteristics of the subcarriers included in corresponding multicarrier signals at different subcarrier frequencies; and determining a number of bits to be allocated to each of the subcarriers included in each of the multicarrier signals based on the transmission characteristics measured at the different subcarrier frequencies.

Abstract: A receiving device includes an optical filter, an acquisition unit, a first determination unit, and a filter setting unit. The optical filter transmits an optical DMT signal received from a sending device. The acquisition unit acquires the transmission characteristics of the optical DMT signal received from the sending device. The first determination unit determines a filter frequency of the optical filter that removes a dip from the optical DMT signal on the basis of the acquired transmission characteristics. The filter setting unit sets the determined filter frequency in the optical filter.