Abstract: An optical communication system includes an optical transmitter that sends an optical signal; and an optical receiver that receives the optical signal. The optical transmitter controls a transmission rate of the optical signal to a first transmission rate corresponding to first reception light power lower than target reception light power of the optical receiver in response to transmission light power control for the optical signal corresponding to the target reception light power.

Abstract: A multilevel-intensity modulation and demodulation system includes: a digital-to-analog conversion unit to convert an output level value of a digital signal into an analog signal; a multilevel-intensity-modulated light transmission unit to transmit an optical signal multilevel-intensity modulated based on the analog signal; a multilevel-intensity-modulated light reception unit to receive the optical signal multilevel-intensity modulated, and convert the received optical signal into an analog reception electrical signal; an analog-to-digital conversion unit to convert the analog reception electrical signal into a reception level value; and a controller to convert a transmission multiple gradation level being one of a plurality of multiple gradation levels of multilevel-intensity modulation to which the digital signal is mapped, into the output level value so as to cause the reception level value to be in a desired reception state, and to receive a digital signal corresponding to a reception multiple-gradation-

Abstract: An optical transmitter transmits to an optical receiver a multi-carrier modulated signal light by driving a light source with a modulated signal modulated with a multi-carrier modulation scheme. The optical receiver monitors reception characteristic of any of subcarrier signals included in the modulated signal and transmits a monitor result to the optical transmitter. The optical transmitter controls drive conditions of the light source based on the monitor result received from the optical receiver.

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 transmission apparatus includes: an assigning unit that assigns an information signal to a subcarrier with a frequency different from a frequency of a received radio signal; a creating unit that creates a multi-carrier signal, in which information signals are multiplexed, each of the information signals being assigned to one subcarrier by the assigning unit; and a multiplexing unit that frequency-multiplexes the received radio signal to the multi-carrier signal created by the creating unit and outputs a resulting frequency-multiplexed signal.

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 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 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: 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: 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: A transmission control device includes a subcarrier selector configured to select one or more subcarriers for transmitting an error correction code for correcting data, from a plurality of subcarriers having different transmission capacities, each of the plurality of subcarriers used for transmitting either of the data and the error correction code, in accordance with an amount of data of the error correction code and transmission capacities respectively assigned to the plurality of subcarriers.

Abstract: An optical transmission device includes: an error correction scheme determining unit configured to determine an error correction scheme based on a latency between the optical transmission device and a correspondent device; an error correction encoder configured to generate encoded data by performing an error correction encoding on transmission data using the error correction scheme determined by the error correction scheme determining unit; a modulation format determining unit configured to determine 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; and an optical transmitter configured to generate a modulated optical system from the encoded data with the modulation format determined by the modulation format determining unit.

Abstract: A PON (Passive Optical Network) system, which modulates multiple subcarriers with data of multiple users to output an optical multiplexed signal from a station device, splits the optical multiplexed signal to transmit the split signals to multiple subscriber devices that are provided for each of the users, and demodulates the data of the users at the respective subscriber devices, includes: an obtaining section configured to obtain a transmission characteristic for each of the subcarriers at each of the subscriber devices, by receiving a test signal at the subscriber devices, which is transmitted from the station device; and an assigning section configured to assign one or more of the subcarriers for each of the subscriber devices suited to the transmission characteristics of the assigned subcarriers at each of the subscriber devices.

Abstract: A multilevel-intensity modulation and demodulation system includes: a digital-to-analog conversion unit to convert an output level value of a digital signal into an analog signal; a multilevel-intensity-modulated light transmission unit to transmit an optical signal multilevel-intensity modulated based on the analog signal; a multilevel-intensity-modulated light reception unit to receive the optical signal multilevel-intensity modulated, and convert the received optical signal into an analog reception electrical signal; an analog-to-digital conversion unit to convert the analog reception electrical signal into a reception level value; and a controller to convert a transmission multiple gradation level being one of a plurality of multiple gradation levels of multilevel-intensity modulation to which the digital signal is mapped, into the output level value so as to cause the reception level value to be in a desired reception state, and to receive a digital signal corresponding to a reception multiple-gradation-

Abstract: A transmitting apparatus is used in an electrical frequency division multiplex transmission system including nodes that are on an optical transmission path and that respectively frequency-multiplex a sub-carrier of a unique frequency and a carrier wave to transmit information to a receiving apparatus on the optical transmission path. The transmitting apparatus is disposed in each node and includes a determining unit that receives an input of information concerning unused sub-carriers of a transmission signal in the optical transmission path and determines transmission of the information to the receiving apparatus using an unused sub-carrier; an electrical frequency division multiplex transmission unit that using a frequency of the unused sub-carrier determined by the determining unit, modulates the input information to be transmitted to the receiving apparatus; and a coupling unit that adds to the transmission signal in the optical transmission path, a modulated modulation signal.

Abstract: An optical communication system includes an optical transmitter that sends an optical signal; and an optical receiver that receives the optical signal. The optical transmitter controls a transmission rate of the optical signal to a first transmission rate corresponding to first reception light power lower than target reception light power of the optical receiver in response to transmission light power control for the optical signal corresponding to the target reception light power.

Abstract: A transmission apparatus includes: an assigning unit that assigns an information signal to a subcarrier with a frequency different from a frequency of a received radio signal; a creating unit that creates a multi-carrier signal, in which information signals are multiplexed, each of the information signals being assigned to one subcarrier by the assigning unit; and a multiplexing unit that frequency-multiplexes the received radio signal to the multi-carrier signal created by the creating unit and outputs a resulting frequency-multiplexed signal.

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.

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: A phase shift unit provides a prescribed phase difference (?/2, for example) between a pair of optical signals transmitted via a pair of arms constituting a data modulation unit. A low-frequency signal f0 is superimposed on one of the optical signals. A signal of which phase is shifted by ?/2 from the low-frequency signal f0 is superimposed on the other optical signal. A pair of the optical signals is coupled, and a part of which is converted into an electrical signal by a photodiode. 2f0 component contained in the electrical signal is extracted. Bias voltage provided to the phase shift unit is controlled by feedback control so that the 2f0 component becomes the minimum.