IEC 61280-1-4:2023

Overview

IEC 61280-1-4:2023 specifies the encircled flux measurement method for light sources used with multimode fibre. The standard defines a traceable procedure to collect two‑dimensional near‑field greyscale images of a fibre output and to reduce them to one‑dimensional radial functions describing the source launch: intensity, incremental flux, and encircled flux as functions of radius from the optical centre. Estimating fibre core diameter is explicitly not an objective. This third edition (2023) updates calibration, measurement hardware and computation methods to improve precision and traceability.

Key Topics

• Measurement principle: capture calibrated 2D near‑field images and convert to three sampled radial functions (intensity, incremental flux, encircled flux).
• Data reduction: specifies numerical processing (e.g., trapezoidal or higher‑order integration), ring width parameter, integration limit, and baseline subtraction to reduce DC drift and improve repeatability.
• Apparatus and components: requirements for camera/detector, image digitizer, magnifying optics, attenuator, input port, calibration light source, fibre shaker, and test jumper assemblies.
• Calibration and traceability: improved calibration procedures and traceability requirements to ensure reproducible encircled flux results; the 2023 edition removes poorly traceable micro‑positioner calibration processes and aligns geometric calibration with established methodologies (see references such as IEC 61745).
• Pulsed sources: explicit inclusion of pulsed light sources in measurement scope and procedures.
• Measurement workflow: raw and dark image acquisition, corrected images, optical‑centre (centroid) determination, and computation of encircled flux.

Applications

IEC 61280-1-4:2023 is used where controlled multimode launch characterization is required:

• Manufacturers of multimode lasers, LEDs and transceivers for qualifying source launch conditions.
• Test laboratories and calibration houses performing standardized encircled flux measurements and reporting.
• System integrators and installers verifying launch conditions for consistent multimode link insertion‑loss measurements.
• Standards bodies and R&D groups modeling multimode link performance (minimum guaranteed length) and validating simulation inputs.
• Quality and acceptance testing of multimode components and links to ensure measurement reproducibility across instruments and sites.

Related Standards

• IEC 61745 (geometric calibration methodology reference)
• Other parts of the IEC 61280 series (fibre optic communication subsystem test procedures) for complementary test methods.

Keywords: IEC 61280-1-4:2023, encircled flux, multimode fibre, light source measurement, nearfield greyscale data, calibration traceability, fibre shaker, pulsed light sources, geometric calibration.