Chromatic dispersion monitor for WDM systems using vestigial-sideband optical filtering

We propose and demonstrate a novel technique for 10- and 40-Gbit/s chromatic dispersion monitoring that uses an optical filter to select the upper and lower vestigial sideband (VSB) signals in transmitted optical data and determine the relative group delay caused by dispersion. The filter bandwidth is approximately equal to the bit-rate, e.g., -0.3 nm for 40-Gb/s data. The group delay can be measured from detecting the phase of the clock component in the photo-detected data. This technique can be used for both NRZ and RZ format. Many WDM channels can be accommodated by sweeping the optical filter across all channels.