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一、单模光纤偏振特性及其表征单模光纤中一般存在着两个相互垂直的偏振态,即HE_(11)模的两个偏振态HE_(11x)和HE_(11y)。而对实际的单模光纤来说,由于其结构不完整性,如纤芯形变、弯曲、扭转,以及内应力或由于受到外力的作用等等原因,往往引起了双折射现象即:HE_(11x)模和HE_(11y)模间的相速差和群速差,从而产生模式色散;同时也引起了两个偏振态之间的模式能量耦合。这对于通信用单模光纤,特别是对于采用单频光源和零材料色散的高质量单模光纤的通信系统,常常会使其通信容量或中继距
First, the polarization characteristics of single-mode optical fiber and its characterization In single-mode optical fiber there are generally two perpendicular to the polarization state, that HE_ (11) mode two polarization HE_ (11x) and HE_ (11y). However, the actual single-mode optical fiber often causes birefringence due to its structural imperfections such as core deformation, bending, twisting, internal stress or external force, and so on: HE 11x ) Mode and the HE_ (11y) mode, resulting in mode dispersion, and also inducing mode energy coupling between the two polarization states. This is often the case for single-mode optical fibers for communications, and especially for high-quality single-mode optical fibers that use single-frequency light sources and zero-dispersion material,