Networking aspects of PMD and PMD control

For most traffic demands and network topologies, especially in Europe, the efficient usage of ultra long haul WDM systems requires the introduction of optical transparent network elements (NE) which are able to switch or at least add/drop traffic on a optical wavelength basis (OADM or OXC. This leads to optical transparent network domains where distortion effects like chromatic dispersion (CD), nonlinearities, polarisation mode dispersion (PMD) and the noise are accumulating over the optical transparent path which moreover is changing during switching events in the network. To compensate for PMD induced distortions the stochastic nature of PMD anyway causes an adaptive approach. Thus a need for adaptive NE is evident. This NE and their control algorithms require new types of specifications and acceptance testing methods.