Polarization mode dispersion (PMD) is a serious limiting factor for high bit rate optical communication systems. It is important and necessary for PMD researchers to know the joint statistical characters of the second order PMD (SOPMD) vs. differential group delay (DGD) and how about the penalty contributions of PMD vector’s components. In this letter, we first get the joint statistical distributing range and joint probability distributing density of normalized DGD slope, depolarization, and the SOPMD vs. normalized DGD, and the average values of normalized DGD slope and depolarization vs. normalized DGD. The results are independent with PMD value, and the depolarization is the main contributor for SOPMD value. We secondly analyze the system penalties induced by PMD vector’s components. The DGD is the main contributor for the maximum system penalty. When the sate of input polarization (SOIP) is
principle state of polarization (PSP) input and fixing DGD value, the SOPMD is the main contributor for penalty varieties, the main penalty contributors are DGD and depolarization. Ignoring DGD slope effect, with PSP input and fixing DGD value, the system penalty first keeps constant (near zero dB) and then increases linearly with depolarization value increasing; with PSP input and fixing depolarization value, the system penalty decreases with DGD value
increasing and the curve has slightly fluctuant.