PMD Compensation/Mitigation Techniques for High-Speed Optical Transport

In high-speed long-haul optical transport systems with channel data rates at 40 Gbit/s and beyond, polarization-mode dispersion (PMD) is one of the major obstacles that limit system performance. It is desired or in most cases required to increase the system tolerance to PMD through PMD compensation and mitigation. In this paper, we review the techniques of PMD compensation and mitigation, including per-channel based optical PMD compensators (PMDCs), analog and digital electronic PMDCs and all-channel PMD mitigation using distributed fast polarization scrambling and forward-error correction (FEC). With the emergence of digital coherent detection, the signal optical field becomes digitally available, enabling powerful digital PMDC techniques to be applied. Digital PMDC techniques in optical single carrier coherent systems and orthogonal frequency-division-multiplexing (OFDM) systems are briefly reviewed.