Abstract

Over the last few years, polarization-mode dispersion (PMD) has become a serious impediment to upgrading the per channel bit rate of previously installed transmission lines. To first order in frequency, PMD splits a pulse between the fast and the slow axis of the fiber; at the same time, higher orders of PMD induce depolarization and polarization-dependent chromatic dispersion. At high bit rates, all of these effects lead to unacceptable transmission penalties. Various PMD compensation techniques have been proposed. An often-used estimate of PMD-induced penalties is the amount of fractional temporal broadening experienced by a pulse.^1–5 and so a way to assess the relative merit of a PMD compensation technique is to study how it affects pulse broadening.⁴ The expectation value of the residual broadening after compensation for first-order compensators and for compensation by principal state transmission was calculated.⁶ Since transmission errors are primarily caused by the rare events where PMD is unusually large, however, the mean reduction of the pulse broadening is not sufficient to adequately describe the ability of a PMD compensator to reduce system outages.⁵ Here, following Refs. [5, 7], we apply importance sampling (IS) to Monte-Carlo simulations of PMD-induced transmission effects. We find that, when a variable-delay PMD compensator is used, the pulse broadening is strongly correlated with the residual second-order PMD of the whole system.

© 2002 Optical Society of America