Study On Crystal-type Depolarizer And Polarization Mode Dispersion Emulator

This thesis consists of two parts: the design of crystal-type depolarizer andPolarization Mode Dispersion(PMD) emulator. Depolarizer can be used to reducepolarization-dependent damage and thus polarization-related problems can be solvedin optical fiber communication systems, measuring instrument and optical fibersensor. PMD emulator is used to mimic PMD behavior of real optical fibertransmission systems, and it is one of the key technologies for solving PMDproblems.First, the related concepts and knowledge of polarized light are introduced, and asummary of the related concept of PMD and its statistics nature is given in chapter 2,which are the fundamentals for further discussion in later chapters.The following is the work on the design of depolarizer. The performance ofwedged crystal depolarizer and its problems in use are analyzed. Then step-wedgedcrystal depolarizer is described. The performance of Lyot depolarizer on Rectangle,Lorentz and Gauss optical sources and the design criteria of Lyot depolarizer arestudied. According to the optical spectrum of Febry-Perot laser, the optimized designof crystal-type depolarizer for Multiple Longitudinal Mode(MLM) laser is discussedin frequency domain. For two available MLM laser diodes, the relationship betweenpolarization degree of depolarized light and Optical Path Difference (OPD) isnumerically calculated. An experimental depolarizer installation is proposed in whichOPD can be adjusted continuously in a large range. The experimental results are ingood agreement with the theoretical analysis. The designed crystal-type depolarizerfor MLM has two advantages of small accommodation space and strong depolarizingability.We begin by investigating the properties of the first order and the second orderon PMD emulator by simulation. The performances of PMD emulator usingpolarization scrambler and using rotatable waveplate are compared. Next the basictheory of Importance Sampling (IS) and multiple IS are discussed. The first orderperformances of two kinds of PMD emulator are simulated with the help of multipleIS technique. Finally, PMD emulator, which can use multiple IS technique is designed.The PMD emulator allows rare PMD events to be emulated efficiently and has a goodagreement with the Maxwell distribution in the DGD tail.