IEC 61300-3-7:2021 describes methods available to measure the wavelength dependence of attenuation and return loss of two-port, single mode passive optical components. It is not, however, applicable to dense wavelength division multiplexing (DWDM) devices. Measurement methods of wavelength dependence of attenuation of DWDM devices are described in IEC 61300-3-29.There are two measurement cases described in this document:

1. measurement of attenuation only;
2. measurement of attenuation and return loss at the same time.

This third edition cancels and replaces the second edition published in 2009. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:

1. reduction of the number of alternative methods proposed to bring in-line with industry practice;
2. re-statement of the equations for insertion loss and return loss using logarithmic forms more common in the industry;
3. additional recommendations with respect to the creation of fibre terminations;
4. additional discussion on the characterization of the optical sources used in this document;
5. simplification of bi-directional testing;
6. removal of separate return loss only measurement procedures.