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.