Method and apparatus for automatic compensation of chromatic dispersion

A chromatic dispersion compensation apparatus for automatic compensation of chromatic dispersion, CD, of signals transmitted via an optical link at predetermined wavelengths of WDM channels within a predetermined band of a WDM system, the chromatic dispersion compensation apparatus having a signal input and a signal output, and comprising:

• an amplifier connected to the signal input for amplifying optical signals received at the signal input;
• and
• a tapping unit coupled to the signal output and receiving the amplified optical signals from the amplifier via an internal signal line coupled to the amplifier, the tapping unit adapted such that the amplified optical signals output by the amplifier can travel through the tapping unit to the signal output and adapted to tap the amplified optical signals received by the chromatic dispersion compensation apparatus at its signal input via the optical link at predetermined wavelengths and adapted to supply the tapped optical signals to an optical coherent receiver adapted to tune its local oscillator to selected WDM channels to generate corresponding analog electrical signals of the different WDM channels which are sampled by an analog digital converter, ADC, to provide digital signal samples of the selected WDM channels processed by a digital signal processor, DSP, of the chromatic dispersion compensation apparatus to calculate an estimate residual chromatic dispersion value of the received optical signals,
• wherein a tuneable dispersion compensation module, TDCM, of the chromatic dispersion compensation apparatus is set to perform an optical compensation of a residual chromatic dispersion, rCD, of the received optical signals depending on the calculated estimate residual chromatic dispersion value of the received optical signals.