IEC TR 63309:2025

IEC TR 63309 ®
Edition 1.0 2025-06
TECHNICAL
REPORT
Active fibres – Characteristics and measurement methods – Guidance

ICS 33.180.10  ISBN 978-2-8327-0453-0

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– 2 – IEC TR 63309:2025 © IEC 2025
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references. 6
3 Terms and definitions . 6
4 Abbreviated terms . 7
5 Background of active fibres . 8
6 Classification . 12
6.1 Cladding structure . 12
6.2 Rare-earth elements . 12
7 Analysis of key characteristics . 12
7.1 Fibre geometry . 12
7.2 Optical characteristics . 13
7.2.1 Attenuation . 13
7.2.2 Numerical aperture . 14
7.3 Laser transmission characteristics . 15
7.3.1 Absorption coefficient . 15
7.3.2 High power scaling . 16
7.3.3 Slope efficiency . 16
7.3.4 Photodarkening . 16
8 Measurement method guidance of key characteristics . 17
8.1 General . 17
8.2 Guidance for slope efficiency measurement . 19
8.2.1 Object . 19
8.2.2 Apparatus . 19
8.2.3 Sample preparation . 21
8.2.4 Procedure . 22
8.3 Guidance for absorption coefficient measurement . 28
8.4 Guidance for optical-optical conversion efficiency measurement . 28
8.5 Guidance for photodarkening measurement . 28
8.6 Guidance for high power scaling measurement . 28
Annex A (informative) Application of active fibres . 29
Bibliography . 30

3+
Figure 1 – Yb 's energy level diagram in a germane-silicate host [1] . 8
3+
Figure 2 – Typical absorption and emission spectra of Yb ions in germanosilicate
host [2] . 9
Figure 3 – Working principle diagram of active fibre in a fibre lasers . 10
3+
Figure 4 – Er 's energy level diagram of stimulated emission [3] . 11
3+ 3+
Figure 5 – Er /Pr co-doped energy level diagram of stimulated emission [4] . 11
Figure 6 – Schematic diagram of the geometric cross-sections of the core and inner
cladding used in the simulation . 13
Figure 7 – Pumping efficiency of different cladding shapes [5] . 13
Figure 8 – Light absorption along the longitudinal axis . 15
Figure 9 – Definition of slope efficiency . 16
Figure 10 – Photodarkening example [8] . 17

Figure 11 – Typical schematic diagram for apparatus to calibrate pump light power . 22
Figure 12 – Typical schematic diagram for apparatus to laser power test via oscillator
system with beam splitter mirror . 23
Figure 13 – Typical schematic diagram for apparatus to laser power test via oscillator
system without beam splitter mirror . 24
Figure 14 – Typical schematic diagram for apparatus to laser power test via amplifier
system with beam splitter mirror . 25
Figure 15 – Typical schematic diagram for apparatus to laser power test via amplifier
system without beam splitter mirror . 26
Figure 16 – Representation of slope efficiency graph . 28
3+
Figure A.1 – Typical structure of Er -doped fibre amplifiers . 29

Table 1 – Key characteristics and relevant standards . 18
3+
Table 2 – Characteristic wavelength of RE in silica host . 19

– 4 – IEC TR 63309:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ACTIVE FIBRES – CHARACTERISTICS AND
MEASUREMENT METHODS – GUIDANCE

FOREWORD
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IEC TR 63309 has been prepared by subcommittee 86A: Fibres and cables, of IEC technical
committee 86: Fibre optic. It is a Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
86A/2515/DTR 86A/2586/RVDTR
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Report is English.

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specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
– 6 – IEC TR 63309:2025 © IEC 2025
ACTIVE FIBRES – CHARACTERISTICS AND
MEASUREMENT METHODS – GUIDANCE

1 Scope
This document provides an introduction of active fibres describing key characteristics and
measurement methods. For the purpose of this document, an active fibre is a silica-
...