IEC 61757-1-1:2020

Overview

IEC 61757-1-1:2020 - "Fibre optic sensors ­– Part 1-1: Strain measurement – Strain sensors based on fibre Bragg gratings" is an international standard from the IEC that defines detailed specifications and test procedures for FBG (fibre Bragg grating) based strain sensors. It is the second edition (2020), replacing the 2016 edition, and provides the key performance parameters and measurement methods for both the sensor element and the corresponding FBG measuring instrument used to read out optical signals. The standard covers static and dynamic strain measurement across a range of frequencies and includes a blank detail specification (Annex B) for manufacturer or purchaser use.

Key topics and requirements

• Scope & intent: Defines features, characteristics and test methods specific to FBG strain sensors, building on the generic fibre optic sensor rules in IEC 61757.
• FBG characteristics: Requirements for Bragg wavelength, spectral width, reflectivity and spectral shape (including side-lobes).
• Strain sensitivity & gauge factor: Procedures to determine sensitivity, gauge factor and conversion of wavelength shift to strain.
• Mechanical and installation parameters: Gauge length, measuring point, attachment and minimum operating radius of curvature.
• Performance & environmental limits: Temperature and humidity ranges, temperature‑induced strain response, stability (drift, creep, hysteresis), fatigue behavior, maximum strain range and proof-test/lifetime considerations.
• Measurement and evaluation procedures: Sampling plans (type, series and individual testing), statistical reporting, test set-ups (tensile, bending, fatigue), and requirements for the measuring instrument used to interrogate FBGs.
• Documentation: Annexes include a blank detail specification (Annex B), extended properties (Annex A), polarization effects (Annex C) and applied sensor guidance (Annex D).

Applications and who uses the standard

IEC 61757-1-1:2020 is essential for:

• FBG sensor manufacturers specifying product performance and producing data sheets.
• Calibration and test laboratories conducting type and conformance testing.
• System integrators and end-users in structural health monitoring (bridges, buildings, tunnels), aerospace, automotive, energy (wind, oil & gas), civil engineering and research organizations needing validated strain measurement solutions.
• Procurement teams using the blank detail specification to define contractual sensor requirements.

Practical benefits include consistent, repeatable evaluation of FBG strain sensors, clearer instrument requirements for optical interrogation, and guidance to ensure reliable static and dynamic strain monitoring with traceable test methods.

Related standards

• IEC 61757 (generic specifications for fibre optic sensors) - referenced as the overarching document for fibre optic sensor families.