Patent ID: 7389049

Claim:
A chromatic dispersion compensation controlling system for compensating for chromatic dispersion caused when an optical signal is transmitted through a transmission line, comprising: a peak detection unit detecting a peak value of a receiving signal: and a control unit determining whether chromatic dispersion caused in an optical signal is excessive in a positive direction or in a negative direction, by comparing the peak value with a predetermined threshold and supplying a variable chromatic dispersion compensator with a control signal; a transmission quality detection unit detecting transmission quality information of a receiving signal, wherein said control unit supplies the variable chromatic dispersion compensator with a control signal, using a positive/negative sign of excessive chromatic dispersion obtained by detecting a peak value and an absolute value of an amount of chromatic dispersion to be compensated that is obtained from the transmission quality information; sets a threshold of an amount of change in optimal chromatic dispersion compensation, controls the chromatic dispersion compensation by one of a down-hill method and a dithering method, responsive to an amount of change being equal to or less than the threshold, and controls the chromatic dispersion using a positive/negative sign of residual chromatic dispersion obtained from a peak value and an absolute value of an amount of chromatic dispersion to be compensated responsive to the amount of change exceeding the predetermined threshold.