US Patent 7162154 System and method for dispersion detection

According to the system and method of the present invention, the frequency of an optical data signal is modulated on the transmitter side, and group transit time changes of the optical signal are detected on the receiver side. These group transit time changes are preferably determined via synchronous demodulation of a control signal of a voltage-controlled oscillator for timing recovery and are a measurement for any chromatic dispersion, which can be compensated via a chromatic dispersion compensator. The parasitic amplitude modulation generated with the frequency modulation can be used to obtain a reference signal for the synchronous demodulation.