Abstract: An optical transmission apparatus includes a wavelength multiplexing unit that performs wavelength multiplexing with respect to dummy light for each channel of WDM and dummy light for each sub-band including the channels in plural; and a selecting unit that measures for each sub-band and corresponding to intensity of the channel-specific dummy light, transmission characteristics at a reception end, and according to measurement results, selects for each of the sub-bands, any one among the channel-specific dummy light and the sub-band-specific dummy light. The wavelength multiplexing unit wavelength multiplexes any of the channel-specific dummy light selected for each of the sub-bands by the selecting unit.

Abstract: A pre-emphasis control method includes calculating an average value of transmission characteristics based on transmission characteristics of a plurality of light beams received by a receiver, and determining that, among signals of the plurality of light beams, a wavelength with a deviation from the average value is a wavelength at which control is to be performed, determining that the wavelength at which control is to be performed and a wavelength adjacent thereto are a group of wavelengths at which control is to be performed, obtaining an average of transmission characteristics of the group of wavelengths at which control is to be performed, and based on a difference between averaged transmission characteristics and respective transmission characteristics of the group of wavelengths at which control is to be performed, changing a light intensity output from each transmitter that transmits a group of wavelengths at which control is to be performed.

Abstract: An optical transmission apparatus includes a wavelength multiplexing unit that performs wavelength multiplexing with respect to dummy light for each channel of WDM and dummy light for each sub-band including the channels in plural; and a selecting unit that measures for each sub-band and corresponding to intensity of the channel-specific dummy light, transmission characteristics at a reception end, and according to measurement results, selects for each of the sub-bands, any one among the channel-specific dummy light and the sub-band-specific dummy light. The wavelength multiplexing unit wavelength multiplexes any of the channel-specific dummy light selected for each of the sub-bands by the selecting unit.

Abstract: A pre-emphasis control method includes calculating an average value of transmission characteristics based on transmission characteristics of a plurality of light beams received by the receiver, and determining that, among signals of the plurality of light beams, a wavelength with a deviation from the average value is a wavelength at which control is to be performed, determining that the wavelength at which control is to be performed and a wavelength adjacent thereto are a group of wavelengths at which control is to be performed, obtaining an average of transmission characteristics of the group of wavelengths at which control is to be performed, and changing a light intensity output from each transmitter that transmits a group of wavelengths at which control is to be performed based on a difference between averaged transmission characteristics and respective transmission characteristics of the group of wavelengths at which control is to be performed.