Research On Compensation Of Polarization Mode Dispersion In 40Gbit/s Optical Fiber Communication System

Polarization Mode Dispersion (PMD) causes pulse broadening because of thedifference of the group delays between two polarized modes of the optical signal.PMD has become the obstacle to the deployment of 40Gbit/s optical communicationsystem. PMD varies randomly with environmental fluctuations. Solving the problemsof the PMD becomes one of the most important considerations. This thesis reports thedetailed research works of the 40Gbit/s PMD compensation system. It is described inthe following four aspects.First, the relation between the electrical power and the differential group delay(DGD) for a 40Gbit/s transmission system with PMD effect is theoretically analyzedand experimentally demonstrated. The 40Gbit/s automatic PMD compensationsystem with the electrical power as the feedback signal is presented.Secondly, the mathematical expression of the relationship between DOP andDGD is derived. The DOP-DGD curve for a single Gauss pulse and the pseudorandom m sequence Gauss pulse are researched theoretically and the different powersplitting ratios and the optical spectrum widths are considered as the parameters ofthe formulae. The formulas are checked experimentally. The research of the 40Gbit/sautomatic PMD compensation system with DOP as the feedback signal is presented,and the experimental results show that it is effective for PMD compensation.Third, a novel adaptive tracking algorithm is adopted, which shows theeffectiveness in the tracking course with no instant worsening of the feedback signal,and efficiently eliminating the hysteresis effect of the polarization controller (PC).The response time of the operation of the algorithm is at the level of milliseconds.Finally, the PMD forward compensation sketch based on state of polarization(SOP) is proposed, and the methods of measuring the magnitude and direction ofPMD are researched.