Abstract: An optical transceiver to which subcarrier modulation is applied includes a signal processor that monitors a differential group delay and polarization fluctuation of a transmission line for a predetermined period of time, and a control processor that determines, based on the monitoring results of the differential group delay and the polarization fluctuation, a number of subcarriers to be configured in the optical transceiver from among candidates of numbers of subcarriers configurable in the optical transceiver, the numbers of subcarrers configurable in the optical transceiver being determined depending on an ability of a signal processor of the optical transceiver.

Abstract: A network system includes a first device and a second device coupled to the first device. The second device configured to calculate a bandwidth of an optical signal narrowed by a wavelength filter from the number of wavelength filters on a transmission route of the optical signal, to select, based on a plurality of combinations of a degree of multilevel and the baud rate, and a correspondence between a lower limit value of a bandwidth of the optical signal and a lower limit value of an optical signal to noise ratio (OSNR) for maintaining predetermined quality of the optical signal, one or more first combinations from the plurality of combinations, to select a second combination from the one or more first combinations, and to set the degree of multilevel and the baud rate of the second combination in the first device.

Abstract: A network system includes a first device and a second device coupled to the first device. The second device configured to calculate a bandwidth of an optical signal narrowed by a wavelength filter from the number of wavelength filters on a transmission route of the optical signal, to select, based on a plurality of combinations of a degree of multilevel and the baud rate, and a correspondence between a lower limit value of a bandwidth of the optical signal and a lower limit value of an optical signal to noise ratio (OSNR) for maintaining predetermined quality of the optical signal, one or more first combinations from the plurality of combinations, to select a second combination from the one or more first combinations, and to set the degree of multilevel and the baud rate of the second combination in the first device.

Abstract: An optical communication apparatus has an interface circuit that acquires transfer condition information including a bit rate and a channel spacing of an optical network, a processor that selects a modulation scheme in accordance with the transfer condition information and operates in the modulation scheme, wherein the processor is configured to select a first modulation scheme when the bit rate is greater than a first value in accordance with the channel spacing, and select a second modulation scheme when the bit rate is smaller than the first value, the second modulation scheme having a data transfer performance higher than the first modulation scheme.

Abstract: A network design method includes calculating, from the number of wavelength filters on a transmission route of an optical signal, a bandwidth of the optical signal after narrowing by the wavelength filters, selecting, from a plurality of combinations of a multi-level modulation system and a baud rate about the optical signal set in a transmitting apparatus, one or more first combinations about which a lower-limit value of the bandwidth of the optical signal in each of the combinations is equal to or smaller than the bandwidth of the optical signal after narrowing, and selecting a second combination from the one or more first combinations based on a minimum value of an OSRN of the optical signal in the selected combinations.

Abstract: An optical communication apparatus includes an interface circuit that acquires bit rate information of an optical network, and a processor that selects a modulation scheme in accordance with the bit rate information and operates in the modulation scheme, wherein the processor is configured to select a first modulation scheme when the bit rate is equal to or greater than a first value, and select a second modulation scheme when the bit rate is smaller than the first value, the second modulation scheme having a data transfer performance higher than the first modulation scheme.

Abstract: A receiving apparatus includes a first processor configured to compensate, in a perturbation back-propagation (PBP) scheme, waveform degradation of an optical signal by traveling an optical transmission line due to a nonlinear optical effect; a memory; and a second processor coupled to the memory and the second processor configured to change a gamma coefficient to be used in the PBP scheme, measure reception quality of the optical signal for each of gamma coefficients obtained by the changing, specify a gamma coefficient in accordance with the reception quality from among the gamma coefficients obtained by the changing, and set the specified gamma coefficient as a parameter of the PBP scheme.

Abstract: A network design method includes calculating, from the number of wavelength filters on a transmission route of an optical signal, a bandwidth of the optical signal after narrowing by the wavelength filters, selecting, from a plurality of combinations of a multi-level modulation system and a baud rate about the optical signal set in a transmitting apparatus, one or more first combinations about which a lower-limit value of the bandwidth of the optical signal in each of the combinations is equal to or smaller than the bandwidth of the optical signal after narrowing, and selecting a second combination from the one or more first combinations based on a minimum value of an OSRN of the optical signal in the selected combinations.

Abstract: A receiving apparatus includes a first processor configured to compensate, in a perturbation back-propagation (PBP) scheme, waveform degradation of an optical signal by traveling an optical transmission line due to a nonlinear optical effect; a memory; and a second processor coupled to the memory and the second processor configured to change a gamma coefficient to be used in the PBP scheme, measure reception quality of the optical signal for each of gamma coefficients obtained by the changing, specify a gamma coefficient in accordance with the reception quality from among the gamma coefficients obtained by the changing, and set the specified gamma coefficient as a parameter of the PBP scheme.

Abstract: A receiving apparatus includes a first processor configured to compensate, in a perturbation back-propagation (PBP) scheme, waveform degradation of an optical signal by traveling an optical transmission line due to a nonlinear optical effect; a memory; and a second processor coupled to the memory and the second processor configured to change a gamma coefficient to be used in the PBP scheme, measure reception quality of the optical signal for each of gamma coefficients obtained by the changing, specify a gamma coefficient in accordance with the reception quality from among the gamma coefficients obtained by the changing, and set the specified gamma coefficient as a parameter of the PBP scheme.

Abstract: A coding apparatus includes a check matrix, a calculator, a selector, and a synthesizer. The check matrix includes a parity operation matrix including a matrix along a diagonal, a circulant matrix positioned one row and a predetermined number of rows below the diagonal, and an information operation matrix. The calculator sets, in response to an input of a bit sequence of a message, every pattern of initial values to a less-significant bit sequence of parity bits corresponding to the number of the predetermined rows, and calculates parity bit sequences for the respective patterns of the initial values. The selector selects a parity bit sequence corresponding to one of the patterns of initial values when the less-significant bit sequence of the parity bit sequence matches the pattern of initial values. The synthesizer concatenates the selected parity bit sequence to the bit sequence of the message, and outputs the resultant code word.

Abstract: An optical transmission system includes a first optical transmission apparatus that adds a plurality of error correction codes to a main signal, retrieves, from a first error correction code that is added to the main signal and that corresponds to a first sub-carrier among the plurality of sub-carriers, a first code portion in excess of a predetermined redundancy level, distributes the first code portion to a second sub-carrier among the plurality of sub-carriers, concatenates a second code portion into the first error correction code, and transmits an optical signal including the main signal multiplexed with the first error correction code that has been concatenated with the second code portion.

Abstract: An optical transmission system includes: a first optical transmission apparatus configured to add an error correction code (ECC) having a code length in accordance with transmission quality of each of sub-carriers forming a super channel to a main signal, retrieve, from the ECC added to the main signal on a sub-carrier to be processed, a code portion in excess of a predetermined redundancy level, distribute the code portion to another sub-carrier, and concatenate the code portion of the ECC to be added to a main signal on the another sub-carrier into the ECC added to a main signal on the sub-carrier to be processed; and a second optical transmission apparatus configured to concatenate the cord portion of the ECC distributed from another sub-carrier into the ECC included in the optical signal, and decode a main signal in the optical signal on a corresponding sub-carrier by using the concatenated ECC.

Abstract: An optical transmission system includes: a plurality of optical transmission devices each including: an adjustment unit to adjust optical power of channels in the WDM optical signal; and a controller to control the adjustment unit based on an adjustment amount, and a management device including: a converter to convert an evaluation value for evaluating quality of service provided by using the channels in the WDM optical signal into a threshold value of transmission quality to be satisfied by the channels; and a determination unit to calculate the transmission quality of the channels based on monitoring information of the channels in the WDM optical signal adjusted by the adjusting unit of at least one of the plurality of optical transmission devices and to determine the adjustment amount to be set for the optical transmission device so that the calculated transmission quality of the channels satisfy the threshold value.

Abstract: An optical transmission system includes: a plurality of optical transmission devices each including: an adjustment unit to adjust optical power of channels in the WDM optical signal; and a controller to control the adjustment unit based on an adjustment amount, and a management device including: a converter to convert an evaluation value for evaluating quality of service provided by using the channels in the WDM optical signal into a threshold value of transmission quality to be satisfied by the channels; and a determination unit to calculate the transmission quality of the channels based on monitoring information of the channels in the WDM optical signal adjusted by the adjusting unit of at least one of the plurality of optical transmission devices and to determine the adjustment amount to be set for the optical transmission device so that the calculated transmission quality of the channels satisfy the threshold value.

Abstract: In an optical communication device, a light source is capable of varying the wavelength of light to be output. An optical multiplexer multiplexes light output from the light source with signal light received from a transmission path. To an optical medium, light output from the optical multiplexer is input. A monitor monitors light having a predetermined wavelength output from the optical medium. A wavelength number measuring unit measures the number of wavelengths of signal light transmitted through the transmission path based on the result of monitoring by the monitor.

Abstract: A communication system is provided for communicating over a network. A plurality of transmission devices are disposed within a network and connected by transmission channels. A control device calculates initial data required during an initial operation of the transmission devices and sets the initial data to the transmission devices. The transmission devices perform reception processing using maximum likelihood sequence estimation, and the control device obtains, as the initial data, with respect to paths that are signal communication pathways between the transmission devices and in accordance with transmission states of individual paths, initial likelihood information that is initial-stage likelihood information for performing the maximum likelihood sequence estimation.

Abstract: In a wavelength-division multiplexing communications system including a plurality of optical transmission devices having an optical amplifier, downstream optical transmission devices transmit gain wavelength characteristic information of an optical amplifier in each of the downstream optical transmission devices to an upstream optical transmission device. The upstream optical transmission device controls gain wavelength characteristics on the basis of the received gain wavelength characteristic information.

Abstract: A communication system is provided for communicating over a network. A plurality of transmission devices are disposed within a network and connected by transmission channels. A control device calculates initial data required during an initial operation of the transmission devices and sets the initial data to the transmission devices. The transmission devices perform reception processing using maximum likelihood sequence estimation, and the control device obtains, as the initial data, with respect to paths that are signal communication pathways between the transmission devices and in accordance with transmission states of individual paths, initial likelihood information that is initial-stage likelihood information for performing the maximum likelihood sequence estimation.

Abstract: In a wavelength-division multiplexing communications system including a plurality of optical transmission devices having an optical amplifier, downstream optical transmission devices transmit gain wavelength characteristic information of an optical amplifier in each of the downstream optical transmission devices to an upstream optical transmission device. The upstream optical transmission device controls gain wavelength characteristics on the basis of the received gain wavelength characteristic information.