IEC 61280-4-3:20 22描述了使用单模光纤的已安装无源光网络（PON）中的衰减、光回波损耗和光功率的测量。本文档规定了在激活PON之前测量衰减的两种方法: 方法A:使用光源和功率计(LSPM)的单线法； 方法B:仅在上游方向上的光时域反射计（OTDR）方法，减少了由于反向散射系数变化而导致的不确定性。 此外，在资料性附录C中描述的方法C提供了在上游方向上使用U波段滤波光时域反射计(FOTDR)对PON的部分激活之后的衰减的估计。 本出版物包含一个Excel电子表格形式的题为“补充数据”的附件。本文件旨在作为补充，不构成标准的组成部分。

IEC 61280-4-3: 2022 describes the measurement of attenuation, optical return loss and optical power in installed passive optical networks (PONs) using single-mode fibre. This document specifies two methods for measuring the attenuation before activation of the PON:

• method A: one-cord method using a light source and a power meter (LSPM);
• method B: optical time-domain reflectometer (OTDR) method in upstream direction only, with reduction of uncertainties due to the variation of backscatter coefficient.

In addition, method C, which is described in informative Annex C, provides an estimate of the attenuation after partial activation of the PON by using a U band filtered optical time-domain reflectometer (FOTDR) in an upstream direction.
This publication contains an attached file titled "Supplemental Data" in the form of an Excel spread sheet. This file is intended to be used as a complement and does not form an integral part of the standard.