IEC 61757-1-1:2020 is available as IEC 61757-1-1:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 61757-1-1:2020 defines detail specifications for fibre optic sensors using one or more fibre Bragg gratings (FBG) as the sensitive element for strain measurements. Generic specifications for fibre optic sensors are defined in IEC 61757. This document specifies the most important features and characteristics of a fibre optic sensor for strain measurements, based on use of an FBG as the sensitive element, and defines the procedures for their determination. Furthermore, it specifies basic performance parameters and characteristics of the corresponding measuring instrument to read out the optical signal from the FBG. This document refers to the measurement of static and dynamic strain values in a range of frequencies. A blank detail specification is provided in Annex B. This second edition cancels and replaces the first edition published in 2016. This edition constitutes a technical revision. This edition includes the following technical changes with respect to the previous edition:
- update of cited standards;
- clarification of definitions and test specifications.