偏振控制器(PC)是处理光纤中信号偏振态(SOP)的重要器件,它是偏振模色散(PMD)自适应补偿器的重要组成部分。以两种类型的商用偏振控制器为例,理论和实验证明了转变任意输入态到庞加莱(Poincare)球上其他任何状态至少需要调整三个自由度而不是两个自由度。因此至少需要控制每一阶段的PMD补偿器中偏振控制器上的三个自由度而不是两个自由度,才能够实现完全的PMD补偿。 Polarization Controller (PC) is an important device for processing signal polarization state (SOP) in optical fiber. It is an important part of Polarization Mode Dispersion (PMD) adaptive compensator. Taking two types of commercial polarization controllers as an example, the theory and experiments show that changing any input state to any other state on the Poincare sphere requires at least three degrees of freedom instead of two degrees of freedom. Therefore, it is at least necessary to control the three degrees of freedom on the polarization controller in each phase of the PMD compensator instead of two degrees of freedom to achieve full PMD compensation.