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: An optical transmitter includes a discrete multi-tone (DMT) modulation unit that modulates a carrier signal having a specific frequency with an information signal and a carrier signal having a frequency different from the specific frequency with a monitor signal, to generate a DMT modulation signal that multiplexes the information signal and the monitor signal. The optical transmitter includes a laser diode (LD) unit that optically converts the DMT modulation signal to a corresponding optical DMT modulation signal, a frequency extraction unit that extracts a harmonic distortion component of the monitor signal from the optical DMT modulation signal, and a frequency analysis unit. The optical transmitter includes a bias control unit that controls a bias supply unit that adjusts a bias value to be supplied to the LD unit such that the extracted harmonic distortion component of the monitor signal is reduced.

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 optical signal receiving device includes a receiver configured to receive an optical signal on which modulation has been performed by an optical signal transmission device, a convertor configured to convert the optical signal received by the receiver to a digital signal by sampling an intensity of the optical signal, and a processor coupled to the converter and configured to determine, based on a frequency distribution of the intensity of the optical signal indicated by the digital signal converted by the converter, a modulation scheme of the modulation performed by the optical signal transmission device.

Abstract: A transmission apparatus includes: a first obtaining section configured to obtain a first transmission characteristic in communication of a multi-carrier signal through a transmission path between the transmission apparatus and a distant transmission apparatus; a second obtaining section configured to obtain a second transmission characteristic under a predetermined usage condition within a specified performance range of the transmission apparatus; a correcting section configured to correct the first transmission characteristic according to the second transmission characteristic; and a determining section configured to determine an amount of allocation for each subcarrier included in the multi-carrier signal, according to the first transmission characteristic that has been corrected by the correcting section.

Abstract: A transmission device is implemented in a first node in an optical transmission system in which a frame is transmitted from the first node to a second node via an optical interface. The transmission device includes a decision unit that decides whether a type of a first error correction code used in the first node is the same as a type of a second error correction code used in the second node. When a type of the first error correction code is the same as a type of the second error correction code, the transmission device transmits the frame to which an error correction code used in the first node is added to the second node without terminating the error correction code.

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 device includes: a plurality of modulators that respectively generate multicarrier signals from given data; a distributor that distributes input data to the modulators; an optical circuit that multiplexes the multicarrier signals to generate a WDM optical signal; and a controller that obtains allocation information from a receiver of the WDM optical signal and generates a distribution instruction to control the distributor and a bit allocation instruction to control the modulators according to the allocation information. The allocation information is calculated based on transmission characteristics of each subcarrier of the respective multicarrier signals and the allocation information indicates a number of bits of data allocated to each of the subcarriers. The distributor distributes the input data to the modulators according to the distribution instruction.

Abstract: An optical transmitter converts a plurality of transmission signals transmitted via a plurality of lanes into a multi-carrier signal and transmits the multi-carrier signal. The optical transmitter includes: a controller configured to generate allocation information that indicates an allocation of sub-carriers to the plurality of lanes according to a bit rate of the transmission signal of each of the lanes and a possible transmission capacity of each of the sub-carriers; and a signal processor configured to convert the plurality of transmission signals into the multi-carrier signal in accordance with the allocation information generated by the controller.

Abstract: An optical transmitter includes a DMT modulating unit that allocates information signals to SCs and that generates a DMT signal by performing multi-level modulation on each of the information signals allocated to each of the SCs. The optical transmitter includes a mixer that shifts, on the basis of the probe result of the DMT signal and frequency information on a wireless signal that is input, the carrier frequency of the wireless signal so as not to overlap the SC to which the information signal in the DMT signal is allocated. Furthermore, the optical transmitter includes a multiplexing unit that multiplexes the DMT signal received from the DMT modulating unit and the wireless signal in which the carrier frequency has been shifted and outputs the multiplexed signal.

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 transmission device includes an error correction scheme determining unit, an error correction encoder, a modulation format determining unit and an optical transmitter. The error correction scheme determining unit determines an error correction scheme based on a latency between the optical transmission device and a correspondent device. The error correction encoder generates encoded data by performing an error correction encoding on transmission data using the error correction scheme determined by the error correction scheme determining unit. The modulation format determining unit determines a modulation format based on the error correction scheme determined by the error correction scheme determining unit and transmission characteristics between the optical transmission device and the correspondent device. The optical transmitter generates a modulated optical signal from the encoded data with the modulation format determined by the modulation format determining unit.

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 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 transmission device connects a plurality of transmission device by a ring network. The transmission device includes a generating unit, a transmission unit, a determination unit, and a setting unit. The generating unit generates a test signal. The transmission unit transmits the generated test signal to a first transmission device provided immediately downstream in the ring network. The determination unit determines whether a transmission characteristic of the own device on the basis of the test signal measured by the first transmission device is acquired from a second transmission device provided immediately upstream by rounding the ring network. The setting unit sets, on the basis of the acquired transmission characteristic when the transmission characteristic of the own device is acquired, a control level related to the transmission performed by the transmission unit.

Abstract: An optical transmitter includes: a digital signal process unit that generates a drive signal for generating multi-carrier signals through a plurality of independent digital signal processes, the multi-carrier signals having a cyclic prefix and to be transmitted by a parallel transmission; a synchronization unit that synchronizes clocks of the plurality of digital signal processes; and an adjust unit that reduces a delay difference of the cyclic prefix between the multi-carrier signals after the parallel transmission.