Improving the tolerance to polarization mode dispersion (PMD) is considered to be one of the major prerequisites for the success of modern high bit rate optical communication systems. Various approaches such as optical compensation, electrical mitigation, multi-level modulation formats promise to increase the PMD tolerance of optical systems, whereas the question of how to experimentally characterize these solutions needs to be answered before commercial deployment. We show that deterministic polarization controllers combined with in-situ measurement of PMD can help to explore the PMD tolerance of an optical communication system and to generate reliable and repeatable. These elements can be combined to form a PMD testbed which allows to stress a system by applying a deterministic amount of PMD including a well-defined rate of change. Finding an agreement on standard test procedures for such a testbed will make the evaluation of PMD tolerant receivers easier and more comparable.