相干光通信系统中的偏振控制技术

Polarisation Control Techniques for Coherent 0ptical Communications

在相干光通信系统中,接收端的输入信号和本机振荡信号的偏振状态(SOP)必须相匹配,否则不但难以达到应有的接收灵敏度,甚至还可能劣于直接检测系统。对于目前普遍使用的单模光纤,由于其SOP转移特性是随时间和其它环境条件的影响而变化,因此必须对接收端的输入信号或本机振荡信号的SOP进行实时控制,以确保系统的性能指标。本文介绍了目前国际上常用的几种偏振控制技术,重点放在无限循环控制(Endless Control)和电光集成器件运。用Poincare球面表示法,任何一种偏振控制器的SOP转移特性都可以看作是代表SOP的点在Poincare球面上的旋转过渡。

In coherent optical communication systems the state ofpolarisation (SOP)of the input and local oscillator signal must matchto achieve the highest sensitivity and prevent signal fading. Forcoherent optieal transmission system using conventional single-modefibre, the SOP of received signal varies with time and environmentalconditions. Techniques for real time control of SOP in single-modefibre are required to obtain the best system performance. In this paper, several SOP control techniques are discussed with the emphasison endless control and electro-optic integrated devices. The poincaresphere representation of polarisation is used throughout, in which theSOP transformations are described by rotations on the sphere.