IEC TR 62221:2012

Optical fibres - Measurement methods - Microbending sensitivity

IEC/TR 62221:2012(E) describes four methods (A, B, C and D) for the measurement of microbending sensitivity of optical fibres. These four methods are distinguished by the equipment being used for measurements and their applications:
- method A using an expandable drum and applies to category A1 and class B fibres;
- method B using a fixed diameter drum and applies to category A1 and class B fibres;
- method C using a plate and applied loads and applies to category A1 and class B fibres;
- method D using a "basketweave" wrap on a fixed diameter drum, and applies to category A1 and class B fibres. This second edition cancels and replaces the first edition published in 2001, and constitutes a technical and editorial revision. The main changes with respect to the previous edition are:
- updates related to B6 (bend-insensitive) category single-mode fibres;
- inclusion of a definition for microbending and general properties;
- expansion of general considerations;
- more details given for each method;
- addition of an Annex A. Key words: measurement of microbending sensitivity of optical fibres

General Information

• Status: Published
• Publication Date: 11-Dec-2012
• ICS: 33.180.10 - Fibres and cables
• Technical Committee: SC 86A - Fibres and cables
• Drafting Committee: WG 1 - TC 86/SC 86A/WG 1
• Current Stage: PPUB - Publication issued
• Start Date: 12-Dec-2012
• Completion Date: 28-Feb-2013

Relations

• Revises: IEC TR 62221:2001 - Optical fibres - Measurement methods - Microbending sensitivity
• Effective Date: 05-Sep-2023

Overview

IEC TR 62221:2012 - "Optical fibres - Measurement methods - Microbending sensitivity" is a technical report from the IEC that describes four standardized laboratory methods for measuring microbending sensitivity of optical fibres. The report focuses on characterization test procedures (methods A, B, C and D), system setups and practical considerations for obtaining microbend-induced loss data for category A1 and class B fibres. The second edition (2012) updates the guidance for bend-insensitive (B6) single‑mode fibres, defines microbending, expands general considerations, and adds an informative Annex A.

Key topics and requirements

• Four measurement methods:
  • Method A - Expandable drum; applicable to category A1 and class B; suitable for wide-range linear pressure testing and optical fibre ribbons.
  • Method B - Fixed-diameter drum; applicable to category A1 and class B; used for fixed linear pressure tests and ribbons.
  • Method C - Plate with applied loads; applicable to category A1 and class B; allows wide-range load measurement on short samples.
  • Method D - Basketweave wrap on fixed-diameter drum; applicable to category A1 and class B; long-length characterization.
• Sample length guidance (typical examples given in the report):
  • Method A ~ 300 m; Method B ~ 400 m; Method C ~ 2–3 m; Method D ~ 2.5 km.
• Temperature cycling: Methods A, B and D can be used with temperature cycles if low thermal‑expansion materials (e.g., quartz drums) are used.
• Measurement scope: These are characterization-type tests - results are qualitative and can vary significantly between laboratories; they are not intended as routine production acceptance tests.
• General considerations covered: launch conditions for multimode fibres, winding tension, relaxation time, drum and material choices, and calculation/interpretation of added loss.

Practical applications

• Characterizing fibre designs for sensitivity to microbending during:
  • Fibre R&D and qualification (single-mode and multimode fibres, including bend‑insensitive types).
  • Cable design optimization - assessing how coatings, buffer and cable structures protect fibres from microbend-induced loss.
  • Environmental testing - evaluating loss changes with temperature cycling and mechanical stresses.
• Use cases: determining whether a fibre or ribbon will meet performance targets when subjected to installation strains, thermal cycling, or cable material variations.

Who should use this standard

• Optical fibre manufacturers and R&D engineers
• Independent testing laboratories and qualification facilities
• Cable designers and system integrators concerned with reliability under mechanical and thermal stresses
• Standards and compliance teams assessing fibre characterization methods

Related standards

• IEC 60793-1-1 (measurement methods - general guidance)
• IEC 60793-1-22 (length measurement)
• IEC 60793-1-40 (attenuation)
• IEC 60793-1-46 (monitoring optical transmittance changes)
• IEC 62614 (launch conditions for multimode attenuation tests)

Keywords: IEC TR 62221:2012, microbending sensitivity, optical fibres, measurement methods, expandable drum, fixed diameter drum, plate test, basketweave, bend‑insensitive fibre, fibre characterization.

Standards Content (Sample)

IEC/TR 62221 ®
Edition 2.0 2012-12
TECHNICAL
REPORT
colour
inside
Optical fibres – Measurement methods – Microbending sensitivity

IEC/TR 62221:2012(E)
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IEC/TR 62221 ®
Edition 2.0 2012-12
TECHNICAL
REPORT
colour
inside
Optical fibres – Measurement methods – Microbending sensitivity

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
T
ICS 33.180.10 ISBN 978-2-83220-500-6

– 2 – TR 62221  IEC:2012(E)
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 General properties of microbending loss . 7
4 General considerations . 7
4.1 Launch condition for multimode fibres . 7
4.2 Sample lengths . 7
4.3 Winding tension . 7
4.4 Relaxation time . 8
4.5 Material used for fixed roughness . 8
4.6 Drum materials . 8
4.7 Drum material for temperature cycling . 8
5 Test procedures . 8
5.1 Method A: expandable drum . 8
5.1.1 General . 8
5.1.2 Apparatus . 8
5.1.3 Procedure . 9
5.1.4 Calculations . 9
5.2 Method B: fixed diameter drum . 10
5.2.1 General . 10
5.2.2 Apparatus . 10
5.2.3 Procedure . 12
5.2.4 Calculations . 12
5.3 Method C: plate test . 13
5.3.1 General . 13
5.3.2 Apparatus . 13
5.3.3 Procedure . 14
5.3.4 Calculations . 14
5.4 Method D: basketweave . 15
5.4.1 General . 15
5.4.2 Apparatus . 15
5.4.3 Procedure . 16
5.4.4 Calculations or interpretation of results . 17
6 Results . 17
Annex A (informative) Representative results with method B . 19
Bibliography . 24

Figure 1 –Set-up for expandable drum method used in an optical fibre testing facility . 9
Figure 2 – Standard winding/prooftester can be used for preparing the sample . 11
Figure 3 –Example of a possible set-up in temperature cycling . 11
Figure 4 – Alternative wire mesh set-up used in an optical fibre testing facility . 12
Figure 5 – Microbend-inducing equipment . 13
Figure 6 – Quartz drum with basketwoven fibre . 15

TR 62221  IEC:2012(E) – 3 –
Figure 7 – Basketweave example as used in an optical fibre testing facility . 16
Figure 8 – Example of temperature cycle inside chamber. 17
Figure A.1 – Example of temperature cycling of 10 different unshifted single-mode
fibres (wavelength 1 310 nm) . 20
Figure A.2 – Example of temperature cycling of 10 different unshifted single-mode
fibres (wavelength 1 550 nm) . 20
Figure A.3 – Microbending repeatability for fibre N° 1 with winding tension 1 N . 21
Figure A.4 – Ribbon set-up . 21
Figure A.5 – Losses at 1 310 nm for different ribbons . 22
Figure A.6 – Losses at 1 625 nm for different ribbons . 22

Table A.1 – Used instrument and values for single-mode fibres . 19
Table A.2 – Multimode fibre test results . 23

– 4 – TR 62221  IEC:2012(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
MEASUREMENT METHODS –
MICROBENDING SENSITIVITY
FOREWORD
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The main task of IEC technical committees is to prepare International Standards. However, a
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data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 62221, which is a technical report, has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2001, and constitutes a
technical and editorial revision.
The main changes with respect to the previous edition are listed below:
a) updates related to B6 (bend-insensitive) category single-mode fibres;
b) inclusion of a definition for microbending and general properties;
c) expansion of general considerations;

TR 62221  IEC:2012(E) – 5 –
d) more details given for each method;
e) addition of an Annex A.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
86A/1460/DTR 86A/1470/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
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– 6 – TR 62221  IEC:2012(E)
OPTICAL FIBRES –
MEASUREMENT METHODS –
MICROBENDING SENSITIVITY
1 Scope
IEC 62221, which is a technical report, describes four methods (A, B, C and D) for the
measurement of microbending sensitivity of optical fibres.
These four methods are distinguished by the equipment being used for measurements and
their applications:
• method A using an expandable drum and applies to category A1 and class B fibres;
• method B using a fixed diameter drum and applies to category A1 and class B fibres;
• method C using a plate and applied loads and applies to category A1 and class B fibres;
• method D using a "basketweave" wrap on a fixed diameter drum, and applies to category
A1 and class B fibres
Methods A and B may also be used to measure the microbending sensitivity of optical fibre
ribbons.
Methods A and C offer the capability to measure the microbending sensitivity over a wide
range of applied linear pressure or loads. Method B may be used to determine the
microbending sensitivity for a fixed linear pressure.
Methods A, B and D can also be used at different temperatures (temperature cycling)
provided special low thermal expansion materials (e.g. quartz drums) are used.
The results from the four methods can only be compared qualitatively. These methods are
considered characterization type tests.
It shall be understood that the microbend results from any method, could have significant
variation between laboratories.
These methods do not constitute a routine test used in the general evaluation of optical fibre.
This parameter is not generally specified within a detail specification.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60793-1-1:2008, Optical fibres – Part 1-1: Measurement methods and test procedures –
General and guidance
IEC 60793-1-22:2001, Optical fibres – Part 1-22: Measurement methods and test procedures
– Length measurement
IEC 60793-1-40:2001, Optical fibres – Part 1-40: Measurement methods and test procedures
– Attenuation
TR 62221  IEC:2012(E) – 7 –
IEC 60793-1-46:2001, Optical fibres – Part 1-46: Measurement and test procedures –
Monitoring of changes in optical transmittance
IEC 62614, Fibre optics – Launch condition requirements for measuring multimode
attenuation
3 General properties of microbending loss
Added loss due to microbending occurs when localized lateral forces along the length of the
fibre appear. These may be caused by manufacturing and installation strains, as well as
dimensional variations in the cable materials due to temperature changes. Sensitivity to
microbending is a function of the difference of refractive index of the core and the cladding,
and diameters of the core and cladding. Coating structure and material property may also
have an influence.
The effect of microbending in single-mode fibres is increased optical loss at 1 310 nm, 1 550
nm and 1 625 nm wavelength ranges as opposed to macrobend effects in single-mode fibres
that primarily is present in the longer wavelengths 1 550 nm and 1 625 nm.
In category A1 multimode fibres, microbending manifests itself in general nearly equally over
a wide wavelength range (e.g. 850 nm – 1 320 nm).
To reduce microbending losses, the cable structure has to protect the optical fibres from
lateral forces. Loose tube cable construction should be optimized to prevent buckling of the
fibre in the tube during temperature changes leading to possible macrobending as well as
microbending loss.
Cable components such as the cable sheath and the strength member are important because
they also help to reduce the microbending caused by the external mechanical forces on the
cable and by temperature changes.
Microbending losses may also be introduced in aerial cables subjected to excessive
elongation (e.g. heavy ice loading).
4 General considerations
4.1 Launch condition for multimode fibres
Concerning multimode fibres, reference is made to the launching technique described in
IEC 62614, as done for the macrobend test method.
4.2 Sample lengths
This technical report lists several methods to evaluate microbend sensitivity for optical fibres.
One key difference is the sample length requirements for the different methods. Though the
exact sample lengths may vary, a list with lengths that have been typically used is given here
below:
Method Length
A 300 m
B 400 m
C 2 m − 3 m
D 2,5 km
4.3 Winding tension
When using methods A, B or D, the control of the winding tension should be mentioned and
carried out with a calibrated device. Added loss due to microbending is reasonably linear over

– 8 – TR 62221  IEC:2012(E)
a winding tension range from 1 N to 3 N, but different winding tensions could yield different
normalised microbending sensitivity results. For methods A and B, careful winding is required
with no crossovers in order to avoid negative influence on the correct winding force.
4.4 Relaxation time
Information about relaxation time should be given. Almost all fibres show some kind of coating
relaxation effect, most probably dependant on the mechanical properties of the secondary
layer of the primary coating. If no fixed relaxation time is used (time between ending the
winding and starting the attenuation measurement) less repeatable results may be obtained.
This relaxation time needs to be investigated by each user (depending on the particular
coating system tested).
Other mechanical relaxation issues (such as humidity and temperature) have been observed
such as the difference in storage temperature of the fibre spool and the winding/measurement
conditions. This requires some description of the measurement conditions. Temperature
cycling is an additional option in microbending testing.
4.5 Material used for fixed roughness
For methods A and B a fixed roughness material is required that is single wide with only one
single seam such as wire mesh or adhesive sandpaper (e.g. a sandpaper/lapping film PSA –
grade 40 µm – mineral Al O ).
2 3
Reference measurements with kn
...