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偏振模色散动态补偿技术研究

Researches on Adaptive Technology of Compensation for Polarization Mode Dispersion

【作者】 王剑

【导师】 鲍振武; 于晋龙;

【作者基本信息】 天津大学 , 通信与信息系统, 2003, 博士

【摘要】 偏振模色散(PMD)是光纤通信系统中由于不同偏振模式传播速度不同而引起的脉冲展宽现象,并由此限制光纤通信系统的码率和中继距离的提高。解决PMD问题是实现高速光纤通信系统的关键之一,也是近年来光纤通信领域研究的热点之一。PMD问题的最大困难在于差分群延迟(DGD)和偏振主态(PSP)变化的随机性。下面是本论文完成的主要工作:首先通过不同的实验手段观察到由于PMD引起的脉冲展宽和眼图恶化现象。研制了10Gbit/s偏振模色散动态补偿系统的实验样机,从理论上和实验研究了电功率作为反馈控制信息的提取方法,建立了这种反馈控制信息与差分群延迟的关系。计算给出了电控式偏振控制器的传输矩阵,以及将任意输入偏振态变化为任意输出偏振态时偏振控制器电压参数的确定,并实验予以验证。完成了实验样机的硬件设计、关键器件的选购、加工及其联机调试和控制算法的设计与调试、整个系统的调试等。完成了10Gbit/s伪随机码序列的PMD动态补偿的实验,给出补偿前后的眼图。用误码仪测量了三种误码率下的PMD补偿前后的接收灵敏度,并进行了比较,结果显示补偿实验样机能够补偿由于模拟器引起的通道代价,有明显的补偿效果。补偿系统可以跟踪输入PMD的变化并保持良好的眼图张口,实现了动态的PMD补偿。对偏振度(DOP)作为PMD动态补偿的反馈控制信息进行了理论和实验研究。以光相干矩阵为基础推导了DOP与DGD和分光比之间的数学关系,对高斯脉冲的波形函数进行了计算。实验测量了非归零码(NRZ)和归零码(RZ)在不同比特率下(10Gbit/s和20Gbit/s)传输光信号偏振度与差分群延迟和光强分配比的关系曲线。对理论计算和实验结果进行了比较,证明理论计算与实验结果的一致性。

【Abstract】 Polarization Mode Dispersion (PMD) causes pulse broadening because of the difference in speed between two polarized modes in optical fiber communication systems. It limits the upgrading of bit rates and span of relay distance. Solving PMD is the key to realizing optical long-haul transmissions systems and becomes one of the most important considerations. The difficulty of solving PMD lies in its randomness of differential group delay (DGD) between the principal states of polarization (PSP) and the change in PSP with time and wavelength. Tasks done in the thesis are of three aspects. Firstly, a mathematical description of PMD is given and optical pulse broadening and eye patterns closing are observed with different set-ups of experiments. A prototype of PMD compensation system for a 10Gbit/s transmission system emulated by two sections of DGD is set up. The relation between electrical power and DGD is established and ways of extracting feedback control signals for PMD compensation are shown. Calculations for the transmission matrix of a polarization controller are performed and are useful for a control algorithm of compensation.Secondly, experiments of dynamic compensation are well done for PMD of 10Gbit/s pseudo random sequences. The eye patterns with/without compensation are compared and results are shown to be good. Receiving sensitivity of the prototype is measured and deterioration caused by simulator is well compensated for by using our compensation system.Finally, degree of polarization (DOP) as feedback signal for PMD compensation is investigated theoretically and experimentally. A mathematical relation between DOP and DGD is derived based on optical coherent matrix. Theoretical calculations and experiments for optical transmissions of Gaussian pulse are done and compared, showing a fine fit between them for both non-return to zero (NRZ) and return to zero (RZ) codes of 10Gbit/s under certain conditions. Other factors affecting DOP are also mentioned in the thesis.

  • 【网络出版投稿人】 天津大学
  • 【网络出版年期】2004年 04期
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