This part of IEC 61282 provides guidelines for the calculation of polarization mode dispersion (PMD) in fibre optic systems to accommodate the statistical variation of PMD and differential group delay (DGD) in optical fibre cables and components. This technical report describes methods for calculating PMD due to optical fibre cables and optical components in an optical link. The calculations are compatible with those documented in the outdoor optical fibre cable specification IEC 60794-3. Example calculations are given to illustrate the methods for calculating total optical link PMD from typical cable and optical component data. The calculations include the statistics of concatenating individual optical fibre cables drawn from a specified distribution. The calculations assume that all components have PMD equal to the maximum specified value. The calculations described cover first order PMD only. The following subject areas are currently beyond the scope of this technical report, but remain under study: – calculation of second and higher order PMD; – accommodation of components with polarization dependent loss (PDL) – if it is assumed that PDL is negligible in optical fibre cables; – system impairments (power penalty) due to PMD; – interaction with chromatic dispersion and other nonlinear effects. Measurement of PMD is beyond the scope of this technical report. Methods of measurement of PMD of optical fibre and cable are given in IEC 60793-1-48. The measurement of optical amplifier PMD is in IEC 61290-11-1. The measurement of component PMD is in IEC 61300-3-32. Measurement of link PMD is given in 61280-4-4. A general theory and guidance on measurements is given in 61282-9.