WG 2 - TC 86/SC 86C/WG 2

IEC 61757-1-2: 2023 defines detailed specifications for distributed strain measurements with a fibre optic sensor, also known as "fibre optic distributed strain sensing". It is applicable to distributed strain sensing systems (DSS) based on spontaneous or stimulated Brillouin scattering in the optical fibre sensor (strain sensitive element), that is, to sensors capable of measuring absolute strain. This document specifies the most important DSS performance parameters and defines the procedures for their determination.

IEC 61757-3-2:2022 specifies the terminology, characteristic performance parameters, related test and calculation methods, as well as specific test equipment for interrogation units used in distributed fibre optic acoustic sensing and vibration measurement systems. This document refers to the Rayleigh backscatter and phase detection method by phase-sensitive coherent optical time-domain reflectometry (ϕ-OTDR) only. Quasi-static and low frequency operation modes are not covered by this document. Generic specifications for fibre optic sensors are defined in IEC 61757.

IEC 61757-2-1:2021 specifies the terminology, characteristic performance parameters and related test methods of optical temperature sensors based on fibre Bragg gratings (FBG) that carry out temperature measurements in the temperature range between ‑260 °C and 600 °C. Generic specifications for fibre optic sensors are defined in IEC 61757.

IEC 61757-5-1:2021 defines the terminology, structure, characteristics and their measurement method including the procedures, for an optical tilt sensor based on fibre Bragg gratings (FBGs) as the sensitive element.

IEC 61757-4-3: 2020 defines terminology, structure, and a characteristic test method of an optical current sensor using the polarimetric method. It addresses the current sensing element only and not the additional devices that are unique to each application. Generic specifications for fibre optic sensors are defined in IEC 61757. As the specifications of optical polarimetric fibre current sensors required by each user vary depending on the application, this document does not define the required performance values. The required performance values are defined when designing a sensor according to the specific application.
The contents of the corrigendum of June 2022 have been included in this copy.

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.

IEC 61757:2018 is a generic specification covering optical fibres, components and sub-assemblies as they pertain specifically to fibre optic sensing applications. It has been designed to be used as a common working and discussion tool by the vendors of components and subassemblies intended to be integrated in fibre optic sensors, as well as by designers, manufacturers and users of fibre optic sensors independent of any application or installation. The objective of this document is to define, classify and provide the framework for specifying fibre optic sensors, and their specific components and subassemblies. The requirements of this document apply to all related fibre optic sensor standards which belong to IEC 61757 (all parts). Standards of IEC 61757 (all parts) contain requirements specific to sensors for particular quantities subject to measurement, and for a particular style or variant of such a fibre optic sensor.
Keywords: fibre optic sensors

IEC 61757-2-2:2016 defines detail specifications for distributed temperature measurement by a fibre optic sensor, also known as fibre optic distributed temperature sensing (DTS). DTS includes the use of Raman scattering, Brillouin scattering and Rayleigh scattering effects. In addition, Raman scattering and Rayleigh scattering based measurements are performed with a single-ended fibre configuration only. Brillouin scattering based measurements are performed with a single-ended fibre or fibre loop configuration. The technique accessible from both sides at same time (e. g. Brillouin optical time domain analysis, BOTDA) is referred to here as a loop configuration. Generic specifications for fibre optic sensors are defined in IEC 61757-1:2012. This part of IEC 61757 specifies the most important DTS performance parameters and defines the procedures for their determination. In addition to the group of performance parameters, a list of additional parameters has been defined to support the definition of the measurement specifications and their associated test procedures. The definitions of these additional parameters are provided for informational purposes and should be included with the sets of performance parameters. A general test setup is defined in which all parameters can be gathered through a set of tests. The specific tests are described within the clause for each measurement parameter. This general test setup is depicted and described in Clause 4 along with a list of general information that should be documented based upon the specific DTS instrument and test setup used to measure these parameters as per IEC 61757-2-2. Annex A provides a blank performance parameter table which should be used to record the performance parameter values for a given DTS instrument and chosen optical test setup configuration. Annex B provides guidelines for optional determination of point defect effects. Keywords: fibre optic distributed temperature sensing (DTS)
This publication is to be read in conjunction with IEC 61757-1:2012