On the Second-Order Approximation of PMD

A second-order PMD approximation based upon the pulse-width distortion has been studied. It shows that a complete second-order approximation should include the second derivative of the PMD vector as well as the first derivative of the PMD vector. Second-order pulse distortions are explicitly expressed including a "first-order" term involving principal states of polarization (PSP) of the pulse and a second-order term involving the beating between fiber chromatic dispersion and effective PMD chromatic dispersion. An analytical result is derived for the probability of second-order PMD power penalty. It shows that the mean PMD of the fiber should be restricted to 26 ps and 18 ps, respectively for a optical link with zero and 850 ps/nm chromatic dispersion, in order to maintain a one dB power second-order penalty with a probability below 10 sup at data rate of 10 Gb/s. The analysis also indicates that a second-order PMD compensator can be used as a dynamic chromatic dispersion compensator.