Reception device, transmission device, optical communication system and optical communication method

A transmission device comprising:

• a plurality of optical transmission units each of which comprises a transmission coefficient computation unit which acquires a parameter indicating a degree of bandwidth narrowing when spectral shaping that narrows bandwidth of a signal to less than or equal to a baud rate is performed, as a band narrowing parameter that is set based on characteristics of a transmission line transmitting optical signals and computes a filter coefficient when processing of narrowing the bandwidth of the signal is applied as band narrowing filter processing, a band narrowing unit which, based on the filter coefficient computed by the transmission coefficient computation unit, applies processing of narrowing the bandwidth of the signal as band narrowing filter processing, and an electrical/optical conversion unit which acquires, as a wavelength-division-multiplexing spacing parameter, information of center wavelengths of the optical signals for respective channels and a spacing between the center wavelengths that are set based on characteristics of the transmission line and converts the signal the bandwidth of which is narrowed to less than or equal to the baud rate by the band narrowing unit to the optical signal, based on the wavelength-division-multiplexing spacing parameter;
• and
• a multiplexing unit which multiplexes the optical signals of the channels output from the plurality of optical transmission units into a multiplexed signal, at spacings less than or equal to the baud rate and outputs the multiplexed signal to the transmission line.

An optical communication method comprising:

• separating a multiplexed signal into which signals of respective channels to which spectral shaping that narrows bandwidth of a signal to less than or equal to a baud rate is applied as band narrowing filter processing, based on a band narrowing parameter that, based on characteristics of a transmission line transmitting optical signals, is set as a parameter indicating a degree of bandwidth narrowing of a signal are multiplexed at spacings less than or equal to the baud rate into optical signals for the respective channels;
• acquiring information of center wavelengths of optical signals for the respective channels and a spacing between the center wavelengths that are set based on characteristics of a transmission line, as a wavelength-division-multiplexing spacing parameter, converting the optical signals of the assigned channels to electrical signals, based on the wavelength-division-multiplexing spacing parameter, and outputting the electrical signals as reception signals,
• acquiring the band narrowing parameter and, based on the band narrowing parameter, computing a filter coefficient when processing having inverse characteristics to those of the band narrowing filter processing is applied to the reception signals as band restoration filter processing, and
• applying the band restoration filter processing to the reception signals, based on the computed filter coefficient and thereby restoring bands of the reception signals.