IEC 61300-3-55:2020提供了测量基于PM光纤的单模偏振保持（PM）光学元件的偏振消光比（PER）的方法。本文件还提供了检测PM部件主轴输入和输出方向的方法，以及估计键控精度的方法，即主轴和连接器机械参考导向键之间的角度偏差（如果存在）。

IEC 61300-3-55: 2020 provides methods for measuring the polarisation extinction ratio (PER) of single-mode, polarisation maintaining (PM) optical components based upon PM fibres. This document also provides methods for detecting the input and output orientation of the PM components' principal axes as well as methods for estimating the keying accuracy, i.e. the angular misalignment between the principal axes and the mechanical reference guide key of the connectors, if these are present.