Optical dispersion monitoring technique using double sideband subcarriers

A technique for measuring the accumulated dispersion affecting a digital optical signal without recovering the baseband was developed and experimentally demonstrated. This technique allows measurement of the accumulated dispersion independently of the data origin and transport history. The technique employs an amplitude-modulated double-sideband subcarrier applied to the signal at the transmitter and monitored at an arbitrary point in a link or network using a novel suppressed-sideband optical-tap technique. The phase difference between the upper and lower sidebands of the subcarrier signal is measured and used to compute the dispersion. A combined coarse and fine measurement realizes high accuracy and large dynamic-range dispersion monitoring.