IEC 61757-1:2012 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 vendor 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 generic specification is to define, classify and provide the framework for specifying fibre optic sensors, and their specific components and subassemblies. The requirements of this standard apply to all related sectional, family, and detail specifications. Sectional specifications will contain requirements specific to sensors for particular quantities subject to measurement. Within each sectional specification, family and detail specifications contain requirements for a particular style or variant of a fibre optic sensor of that sectional specification. This edition includes a substantial technical update of all clauses, definitions, and cited references with respect to the previous edition.