Chromatic dispersion compensation controlling system
The dispersion monitoring device of the present invention detects a change in dispersion caused in a system by performing the decision process of a received signal using a data flip-flop in which required decision phase and decision threshold are set, averaging the output signal of the data flip-flop using an integration circuit and determining a received waveform, based on a change in a level of an output signal from the integration circuit. In another preferred embodiment, a signal is inputted to a chromatic dispersion change sign monitor. If a chirping parameter is correctly set, residual chromatic dispersion shifts in the negative direction when the peak value of a received signal is large, and it shifts in the positive direction when the peak value of a received signal is small. Using this fact, optimum dispersion compensation is conducted.
1. 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.
2. A chromatic dispersion compensation controlling method for compensating for chromatic dispersion caused when an optical signal is transmitted through a transmission line, comprising:
detecting a peak value of a receiving signal: and
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; said determining comprising:
supplying a control signal to said variable chromatic dispersion compensator, using a positive/negative sign of excessive chromatic dispersion obtained by a detection of a peak value and an absolute value of an amount of chromatic dispersion compensation to be compensated from the transmission quality information;
setting a threshold of an amount of change in optimal chromatic dispersion compensation
controlling chromatic dispersion compensation by one of a down-hill method and a dithering method, responsive to an observed amount of change being equal to or less than the threshold; and
controlling 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.