  The use of quantum correlations between photons to measure polarization mode
dispersion (PMD) and chromatic dispersion is investigated. Two types of
apparatus are discussed which use coincidence counting of entangled photon
pairs to allow sub-femtosecond resolution for measurement of both PMD and
chromatic dispersion, as well as separation of even-order and odd-order
chromatic effects in the PMD. Group delays can be measured with a resolution of
order 0.1 fs, whereas attosecond resolution can be achieved for phase delays.
