Optical transmission system and method for chromatic dispersion compensation

An optical transmission system comprising:

• an optical transmission path to transmit WDM signals to which optical signals of different wavelengths are multiplexed, the WDM signals including optical signals of different bit rates or optical signals of different modulation formats;
• a repeater arranged in the optical transmission path, the repeater including a chromatic dispersion compensation unit to compensate chromatic dispersion for the WDM signals;
• and
• a network management system including processes of:
• determining a dispersion compensation ratio indicating a ratio with respect to a dispersion compensation amount at which residual dispersion of the WDM signals is zero after transmission via the optical transmission path, based on a mixture ratio of different optical signals included in the WDM signals, and
• variably setting the dispersion compensation amount for an in-line repeater according to the dispersion compensation ratio,
• wherein the network management system variably sets the dispersion compensation ratio in order to be a maximum value of a product of a transmission capacity of the transmission path and a transmission distance of the transmission line, wherein the maximum value is determined on the basis of a range to satisfy a spec of the transmission distance or the transmission capacity for one or more optical signals multiplexed in the WDM signals to be transmitted.