| Polarization Mode Dispersion (PMD) causes pulse broadening because of thedifference in speeds between two polarized modes in optical fiber communicationsystems. It limits the upgrading of bit rates and span of relay distance. Solving PMDis the key to realizing optical long-haul transmissions systems and becomes one of themost important considerations. The difficulty of solving PMD lies in its randomnessof differential group delay (DGD) between the two principal states of polarization(PSPs) and the change in PSPs with time and wavelength. PMD compensationsystem is researched in the thesis and tasks done here are of three aspects.Firstly, a prototype of PMD compensation system with electrical power as thefeedback signal for a 10Gbit/s transmission system is set up. In order to develop aPMD compensator working under the condition of 40Gbit/s, the relation betweenelectrical power and DGD for a 40Gbit/s transmission system is studied further.Secondly, Jones and Müller matrixes of polarization controller (PC) are derived,according to which the effects of each waveplate's retardation on the input state ofpolarization (SOP) are studied. The hysteresis characteristic of PC is measured. Apolarization scrambler can be realized by adjusting PC regularly, which isinvestigated theoretically and experimentally. Then a polarization stabilizer whichalso uses PC is theoretically researched.Finally, the influences of PMD's magnitude and direction on the distribution ofthe output SOP in Stockes space are researched. The PSP direction can bedetermined by adopting a proper method. The mathematical expressions of degreeof polarization (DOP) for arbitrary waveform and Gauss pulse sequence are derived.And the expression of DOP has been simplified by studying the effect of dispersionand chirp on DOP. The form of DOP-DGD curve for pseudo random m sequence isinvestigated. Then the relations between DOP and DGD with different powersplitting ratio and width of pulse are also researched. |
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