Overview
IEC TR 63309:2025 - Active fibres – Characteristics and measurement methods – Guidance - is a Technical Report from the IEC that introduces active fibres, defined here as silica-based optical fibres whose cores are doped with rare-earth ions (rare‑earth doped fibre) to provide optical gain. Edition 1.0 (2025‑06) summarizes key characteristics, classification, and practical measurement methods used for characterizing active fibres for use in fibre lasers and fibre amplifiers. The scope explicitly excludes fibres that rely on other gain mechanisms (e.g., Raman-effect fibres).
Key topics
- Background & classification
- Definition of active fibres and rare‑earth elements (Er, Yb, Nd, Tm, etc.)
- Cladding and core geometries affecting pump coupling and gain
- Key characteristics analyzed
- Fibre geometry (core/inner-cladding cross sections)
- Optical characteristics: attenuation, numerical aperture (NA)
- Laser transmission characteristics: absorption coefficient, slope efficiency, high‑power scaling, and photodarkening
- Nonlinear and limiting effects: mode instability (MI), stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS)
- Measurement method guidance
- General measurement principles and recommended apparatus layouts (pump calibration, oscillator/amplifier test setups)
- Detailed guidance sections for slope efficiency, absorption coefficient, optical‑to‑optical conversion efficiency, photodarkening, and high‑power scaling
- Practical notes on sample preparation, test procedures and data interpretation (figures and schematic diagrams support setup design)
- Informative annex
- Annex A provides typical applications (e.g., Er‑doped fibre amplifiers) and contextual examples
Applications and practical value
IEC TR 63309 is practical guidance for:
- Manufacturers of rare‑earth doped fibres validating product performance (attenuation, slope efficiency, photodarkening resistance)
- Test laboratories developing reproducible measurement procedures and test rigs for fibre characterization
- Laser and amplifier designers selecting active fibre types and assessing high power scaling and nonlinear limits (SRS/SBS, MI)
- Component suppliers and system integrators optimizing pump coupling, numerical aperture and cladding shapes for improved pumping efficiency
The report helps translate laboratory metrics into system‑level expectations for fibre lasers, high‑power amplifiers, and precision optical amplifiers used in industrial, telecom and scientific applications.
Related standards
- IEC TR 61931 - Fibre optic terminology
- IEC TS 62627‑09 - Vocabulary for passive optical devices
- References also note IEC TR 61282‑4 regarding SRS/SBS phenomena
Keywords: IEC TR 63309, active fibres, rare‑earth doped fibre, fibre laser, measurement methods, slope efficiency, photodarkening, absorption coefficient, numerical aperture.