SIST EN IEC 60793-1-47:2018

SLOVENSKI STANDARD
01-april-2018
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SIST EN 60793-1-47:2009
2SWLþQDYODNQDGHO0HULOQHPHWRGHLQSUHVNXVQLSRVWRSNL,]JXEH]DUDGL
PDNURXSRJLERY,(&
Optical fibres - Part 1-47: Measurement methods and test procedures - Macrobending
loss (IEC 60793-1-47:2017)
Lichtwellenleiter - Teil 1-47: Messmethoden und Prüfverfahren - Makrobiegeverlust (IEC
60793-1-47:2017)
Fibres optiques - Partie 1-47: Méthodes de mesure et procédures d'essai - Pertes par
macrocourbures (IEC 60793-1-47:2017)
Ta slovenski standard je istoveten z: EN IEC 60793-1-47:2018
ICS:
33.180.10 2SWLþQDYODNQDLQNDEOL Fibres and cables
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60793-1-47

NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2018
ICS 33.180.10 Supersedes EN 60793-1-47:2009
English Version
Optical fibres - Part 1-47: Measurement methods and test
procedures - Macrobending loss
(IEC 60793-1-47:2017)
Fibres optiques - Partie 1-47: Méthodes de mesure et Lichtwellenleiter - Teil 1-47: Messmethoden und
procédures d'essai - Pertes par macrocourbures Prüfverfahren - Makrobiegeverlust
(IEC 60793-1-47:2017) (IEC 60793-1-47:2017)
This European Standard was approved by CENELEC on 2017-11-15. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60793-1-47:2018 E

European foreword
The text of document 86A/1823/FDIS, future edition 2 of IEC 60793-1-47, prepared by IEC/SC 86A
"Fibres and cables", of IEC/TC 86 "Fibre optics" was submitted to the IEC-CENELEC parallel vote and
approved by CENELEC as EN IEC 60793-1-47:2018.

The following dates are fixed:
• latest date by which the document has to be (dop) 2018-08-15
implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2020-11-15
• latest date by which the national
standards conflicting with the
document have to be withdrawn
This document supersedes EN 60793-1-47:2009.

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 60793-1-47:2017 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 60793-1-40 NOTE Harmonized as EN 60793-1-40.
IEC 60793-1-46 NOTE Harmonized as EN 60793-1-46.
IEC 60793-2-50 NOTE Harmonized as EN 60793-2-50.

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60793 series Optical fibres - series
IEC 60793-1-1 2017 Optical fibres - Part 1-1: Measurement EN 60793-1-1 2017
methods and test procedures - General
and guidance
IEC 60793-2 -  Optical fibres - Part 2: Product EN 60793-2 -
specifications - General
IEC 60793-2-10 -  EN 60793-2-10 -
IEC 61280-1-4 -  Fibre optic communication subsystem test EN 61280-1-4 -
procedures -- Part 1-4: General
communication subsystems - Light source
encircled flux measurement method
IEC 61280-4-1 -  Fibre optic communication subsystem test EN 61280-4-1 -
procedures -- Part 4-1: Installed cable plant
- Multimode attenuation measurement

IEC 60793-1-47 ®
Edition 4.0 2017-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical fibres –
Part 1-47: Measurement methods and test procedures – Macrobending loss

Fibres optiques –
Partie 1-47: Méthodes de mesure et procédures d'essai – Pertes par

macrocourbures
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.10 ISBN 978-2-8322-4865-2

– 2 – IEC 60793-1-47:2017 © IEC 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Apparatus . 9
4.1 Method A – Fibre winding . 9
4.2 Method B – Quarter circle bends . 9
4.3 Input system . 10
4.3.1 Optical source . 10
4.3.2 Optical launch arrangement . 10
4.4 Output system and detection . 12
4.4.1 Optical divider . 12
4.4.2 Optical detector . 12
4.4.3 Optical detection assembly . 13
4.4.4 Signal processing . 13
5 Specimen . 13
5.1 Specimen length . 13
5.1.1 Method A – Fibre winding . 13
5.1.2 Method B – Quarter circle bends. 13
5.2 Specimen end face . 13
6 Procedure . 13
6.1 Method A – Fibre winding . 13
6.1.1 General consideration . 13
6.1.2 Single-mode fibres . 14
6.1.3 Multimode (A1) fibres . 15
6.2 Method B – Quarter circle bends . 15
7 Calculations . 17
8 Results . 17
8.1 Information available with each measurement . 17
8.2 Information available upon request . 17
9 Specification information . 17
Annex A (normative) Change in transmittance by transmitted power technique . 19
A.1 Apparatus . 19
A.1.1 General . 19
A.2 Procedure . 20
A.3 Calculations . 20
Annex B (normative) Cut-back technique . 22
B.1 General . 22
B.2 Apparatus . 22
B.2.1 General apparatus for all fibres. 22
B.3 Procedure . 22
B.4 Calculations . 23
Annex C (normative) Requirements for the optical source characteristics for A1
multimode measurement . 24

IEC 60793-1-47:2017 © IEC 2017 – 3 –
C.1 Encircled flux (EF) . 24
C.2 Limits on encircled flux . 24
Annex D (informative) Small bend radius phenomena . 27
D.1 General . 27
D.2 Interference between propagating and radiating modes . 27
D.3 Polarization effects . 29
D.4 High power damage . 29
Annex E (informative) Parallel plate (2-point) macrobend loss approximation . 30
E.1 General . 30
E.2 Specimen . 30
E.3 Apparatus . 30
E.3.1 General . 30
E.3.2 Stepper motor control . 31
E.3.3 Movable plate . 31
E.3.4 Fixed plate . 31
E.4 Procedure . 32
E.5 Calculation . 32
E.6 Results . 32
E.7 Comparison of results with normative test . 33
Bibliography . 35

Figure 1 – Quarter circle guide groove in plate . 9
Figure 2 – General launch arrangement . 10
Figure 3 – Lens system . 11
Figure 4 – Launch fibre . 11
Figure 5 – Mode scrambler (for A4 fibre) . 12
Figure 6 – Multiple bends using stacked plates . 16
Figure A.1 – Measurement of change in optical transmittance using reference
specimen . 19
Figure A.2 – Measurement of change in optical transmittance using stabilized source . 20
Figure B.1 – Arrangement of equipment to perform loss measurement at one specified
wavelength . 22
Figure B.2 – Arrangement of equipment used to obtain a loss spectrum . 22
Figure C.1 – Encircled flux template example . 25
Figure D.1 – Loss curves versus curve fits . 28
Figure E.1 – Schematic of possible (two-point bend) apparatus . 31
Figure E.2 – Example of applying an exponential fit to the spectral data of a B6_a2
fibre . 33
Figure E.3 – Example of 2-point bend test data for a B6_a2 fibre . 33

Table 1 – Launch conditions for A2 to A4 fibres . 12
Table C.1 – Threshold tolerance . 25
Table C.2 – EF requirements for 50 µm core fibre cabling at 850 nm . 26
Table C.3 – EF requirements for 50 µm core fibre cabling at 1 300 nm . 26
Table C.4 – EF requirements for 62,5 µm core fibre cabling at 850 nm . 26
Table C.5 – EF requirements for 62,5 µm core fibre cabling at 1 300 nm . 26

– 4 – IEC 60793-1-47:2017 © IEC 2017
Table E.1 – Comparison of parallel plate (2-point) versus method A macrobend loss
measurement for a B6_b3 fibre at 10 mm diameter (ratio of mandrel / 2-point). 34

IEC 60793-1-47:2017 © IEC 2017 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-47: Measurement methods and test procedures –
Macrobending loss
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60793-1-47 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This fourth edition cancels and replaces the third edition published in 2009. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) former Annex A has been renumbered to Annex D;
b) introduction of new Annex A on the transmitted power monitoring technique;
c) introduction of Annex B on the cut-back technique;
d) introduction of Annex C on the requirements for the optical source characteristics of
A1 multimode measurement;
e) introduction of Annex E on parallel plate (2-point) macrobend loss approximation.
The text of this International Standard is based on the following documents:

– 6 – IEC 60793-1-47:2017 © IEC 2017
FDIS Report on voting
86A/1823/FDIS 86A/1828/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
This standard is to be read in conjunction with IEC 60793-1-1:2017.
A list of all parts of IEC 60793 series, published under the general title Optical fibres, can be
found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
IEC 60793-1-47:2017 © IEC 2017 – 7 –
INTRODUCTION
Publications in the IEC 60793-1 series concern measurement methods and test procedures as
they apply to optical fibres.
Within the same series, several different areas are grouped, but all numbers are possibly not
used, as follows:
Parts 1-10 to 1-19: General
Parts 1-20 to 1-29: Measurement methods and test procedures for dimensions
Parts 1-30 to 1-39: Measurement methods and test procedures for mechanical
characteristics
Parts 1-40 to 1-49: Measurement methods and test procedures for transmission and
optical characteristics
Parts 1-50 to 1-59: Measurement methods and test procedures for environmental
characteristics
– 8 – IEC 60793-1-47:2017 © IEC 2017
OPTICAL FIBRES –
Part 1-47: Measurement methods and test procedures –
Macrobending loss
1 Scope
This part of IEC 60793 establishes uniform requirements for measuring the macrobending
loss of single-mode fibres (class B) at 1 550 nm or 1 625 nm, category A1 multimode fibres at
850 nm or 1 300 nm, and category A3 and A4 multimode fibres at 650 nm, 850 nm or
1 300 nm, thereby assisting in the inspection of fibres and cables for commercial purposes.
This document gives two methods for measuring macrobending sensitivity:
• Method A – Fibre winding, pertains to class B single-mode fibres and category A1
multimode fibres.
• Method B – Quarter circle bends, pertains to category A3 and A4 multimode fibres.
For both of these methods, the macrobending loss can be measured utilizing general fibre
attenuation techniques, for example the power monitoring technique (see Annex A) or the
cut-back technique (see Annex B). Methods A and B are expected to produce different results
if they are applied to the same fibre. This is because the key difference between the two
methods is the deployment, including the bend radius and length of fibre that is bent. The
reason for the difference is that A3 and A4 multimode fibres are expected to be deployed in
short lengths with a smaller number of bends per unit fiber length compared to single-mode
and category A1 multimode fibres.
In this document, the "curvature radius" is defined as the radius of the suitable circular
shaped support (e.g. mandrel or guiding groove on a flat surface) on which the fibre can be
bent.
In addition, informative Annex E has been added to approximate bend loss for class B single-
mode fibres across a broad wavelength range at various effective bends.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. 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 (all parts), Optical fibres – Measurement methods and test procedures
IEC 60793-1-1:2017, Optical fibres – Part 1-1: Measurement methods and test procedures –
General and guidance
IEC 60793-2, Optical fibres – Part 2: Product specifications – General
IEC 60793-2-10, Optical fibres – Part 2-10: Product specifications – Sectional specification for
category A1 multimode fibres
IEC 61280-1-4, Fibre optic communication subsystem test procedures – Part 1-4: General
communication subsystems – Light source encircled flux measurement method
IEC 61280-4-1, Fibre-optic communication subsystem test procedures – Part 4-1: Installed
cable plant– Multimode attenuation measurement

IEC 60793-1-47:2017 © IEC 2017 – 9 –
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60793-2,
IEC 60793-1 (all parts) and IEC 60793-1-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE General definitions for fibres are provided in IEC 60793-2, definitions of the specified attributes are
contained in the relevant test methods standard of IEC 60793-1 (all parts), and general definitions for testing are
provided in IEC 60793-1-1.
4 Apparatus
4.1 Method A – Fibre winding
The apparatus consists of a tool (e.g. a mandrel or a guiding groove on a flat surface) able to
hold the sample bent with a radius as stated in the appropriate optical fibre sectional product
specification and a loss measurement instrument. Determine the macrobending loss at the
wavelength as stated in the appropriate sectional product specification by using either the
transmitted power monitoring technique (Annex A) or the cut-back technique (Annex B),
taking care of the appropriate launch condition for the specific fibre type.
4.2 Method B – Quarter circle bends
The apparatus consists of one or more plates, each containing one or more "guide grooves",
and a loss measurement instrument. The plates shall be designed to be stacked during the
test without contacting the sample fibre in a lower or higher plate; such contact will affect the
measurement results. Each guide groove shall have a quarter circle segment (i.e. 90°) as
shown in Figure 1. The bend radius r, i.e. the radius of the quarter circle segment, shall be
stated in the detail specification. The width of each guide groove is recommended to be 40 %
broader than the outer fibre diameter.
Determine the macrobending loss at the wavelength as stated in the appropriate sectional
product specification by using either the transmitted power monitoring technique (Annex A) or
the cut-back technique (Annex B), taking care of the appropriate launch condition for the
specific fibre type.
Guide groove
r
Bend
radius
IEC
Figure 1 – Quarter circle guide groove in plate

– 10 – IEC 60793-1-47:2017 © IEC 2017
4.3 Input system
4.3.1 Optical source
Use a suitable radiation source, such as a lamp, laser or light emitting diode. The choice of
source depends upon the type of measurement. The source shall be stable in position,
intensity and wavelength over a time period sufficiently long to complete the measurement
procedure. Specify the spectral line width (between the 50 % optical intensity power points of
the sources used) such that the line width is narrow, for example less than 10 nm, compared
with any features of the fibre spectral attenuation. Align the fibre to the launch cone, or
connect it coaxially to a launch fibre.
4.3.2 Optical launch arrangement
4.3.2.1 General
Figure 2 shows the general launch arrangement used for all fibres. Apply the appropriate
launch arrangement to produce a full or restricted launch, depending on the parameter being
measured. See 4.3.2.3 to 4.3.2.4 for further details as they apply to specific categories of
single-mode and multimode fibres.
LED/laser
Mode Cladding mode
scrambler stripper
Lamp
Mode filter Launch
Lens
IEC
Figure 2 – General launch arrangement
4.3.2.2 Launch arrangement for single-mode fibres
4.3.2.2.1 General
An optical lens system or fibre pigtail may be employed to excite the test fibre. The power
coupled into the fibre shall be stable for the duration of the measurement (see Figure A.1 or
Figure B.1).
4.3.2.2.2 Fibre pigtail
If using a pigtail, it may be necessary to use index-matching material between the source
pigtail and test fibre to eliminate interference effects.
4.3.2.2.3 Optical lens system
If using an optical lens system, provide a means of stably supporting the input end of the
fibre, such as a vacuum chuck. Mount this support on a positioning device so that the fibre
end can be repeatedly positioned in the input beam. A method of making the positioning of the
fibre less sensitive is to overfill the fibre end spatially and angularly.
4.3.2.2.4 High-order mode filter
Use a method to remove high-order propagating modes in the wavelength range of interest.
An example of such a high-order mode filter is a single loop of radius sufficiently small to shift
the cut-off wavelength below the minimum wavelength of interest, but not so small as to
induce wavelength-dependent oscillations.

IEC 60793-1-47:2017 © IEC 2017 – 11 –
Another option commonly employed on bend insensitive single mode fibres and other single
mode fibres with little or no cut-off response to bend is the use of a standard single mode
fibre as a mode filter.
4.3.2.2.5 Cladding mode stripper
Use suitable techniques to remove optical power propagating in the cladding where this would
significantly influence the received signal. The cladding mode stripper ensures that no
radiation modes, propagating in the cladding region, will be detectable after a short distance
along the fibre. The cladding mode stripper often consists of a material having a refractive
index equal to or greater than that of the fibre cladding. This may be an index-matching fluid
applied directly to the uncoated fibre near its ends; under some circumstances, the fibre
coating itself will perform this function.
4.3.2.3 Launch arrangement for A1 multimode fibres
The required launch for measuring the macrobending loss of A1 multimode fibres shall be an
encircled flux launch. The requirements for the optical source characteristics for A1 multimode
measurement are included in Annex C.
The encircled flux emitted by the launching cord depends on the characteristic of the light
source emerging from the face of the socket, the connection of the launching cord to the
socket, the optical fibre within the launch cord, and any applied mode conditioning.
The test equipment manufacturer should provide specifications for the test cord that are
compatible with the particular source implementation used. When the specification on the cord
is met and used with the test equipment, the encircled flux (EF) requirements should be
assured.
4.3.2.4 Launch arrangements for A2 to A4 multimode fibres
Below are some examples of generic launching arrangements for short-distance fibres
described in Figure 3, Figure 4 and Figure 5.
Fibre under test
IEC
Lens
Figure 3 – Lens system
Launch fibre
Fibre under test
Splice
Cladding mode stripper
IEC
(if necessary)
Figure 4 – Launch fibre
– 12 – IEC 60793-1-47:2017 © IEC 2017
Fibre under test
Mode scrambler
IEC
Figure 5 – Mode scrambler (for A4 fibre)
The reproducibility of the attenuation measurements of step-index fibres is critical. Therefore,
a well-defined launching set-up description is necessary. Such a set-up can be achieved by
using commercially available optical components and shall be able to provide spot sizes and
launch numerical apertures (NAs) as given in Table 1. In addition, the measurement
wavelength shall be calibrated to within ±10 nm.
Table 1 – Launch conditions for A2 to A4 fibres
Attribute Fibre category
A2 A3 A4
Glass core/glass cladding
Glass core/plastic Plastic core/plastic
cladding cladding
Spot size = fibre core size = fibre core size = fibre core size with full
mode launch (or use mode
scrambler with equilibrium
mode launch)
a b
Numerical aperture = fibre max NA, with full
= fibre max NA = fibre max NA
b
(NA)
mode launch
a
This launch condition can be produced by overfilling a mode filter made from 2 m of fibre identical to the fibre
under test (FUT), with appropriate cladding mode stripping and using the output from this mode filter to launch
into the FUT.
b
This launch condition can be produced in the same manner as described in Note a. However, some types of
A3 and A4 fibre will not require cladding mode stripping for the mode filter.

4.4 Output system and detection
4.4.1 Optical divider
When an optical divider is required, it shall have a splitting ratio that remains constant during
the test. The splitting ratio and temperature stability shall be as shown in the relevant detail
specification. Commercially available or custom built devices may be used.
4.4.2 Optical detector
The optical detector shall be of sufficient area to intercept all of the radiated power in the
output cone and shall be sufficiently linear over the optical powers encountered.
The optical detector shall have a sufficiently uniform response over the active area and range
of incidence angle at the measurement wavelength to ensure the movement of the output
cone in position or angle relative to the detector. This shall be within the limits determined by
the mechanical design of the measurement equipment and shall not significantly affect the
results.
Where more than one detector is used, as in the arrangement shown in Figure A.1, the
detectors shall be of the same manufacturer and model and be of comparable linearity.

IEC 60793-1-47:2017 © IEC 2017 – 13 –
4.4.3 Optical detection assembly
All power emitted from the specimen should be coupled to the active region of the detector by
an appropriate means. For example, an optical lens system, a butt spliced fibre pigtail, or
direct coupling to the detector may be used. If the detector is already pigtailed, the pigtail
fibre shall have sufficiently large core diameter and numerical aperture to capture all of the
light exiting the reference and specimen fibres.
Use an optical detector that is linear and stable over the range of intensities and
measurement times that are encountered in performing this measurement. A typical system
can include a photovoltaic mode photodiode amplified by a current input amplifier, with
synchronous detection by a lock-in amplifier.
4.4.4 Signal processing
It is customary to modulate the light source in order to improve the signal-to-noise ratio (SNR)
at the receiver. If such a procedure is adopted, link the detector to a signal processing system
synchronous with the source modulation frequency. The detecting system should be
substantially linear or have known characteristics.
When low loss is expected, more test bends may be added provided there are separate
grooves for each additional bend to improve the SNR; however, the approximation of the bend
diameter along with the bend control may be further degraded.
5 Specimen
5.1 Specimen length
5.1.1 Method A – Fibre winding
The specimen shall be a known length of fibre, as specified in the detail specification. In
particular, the length of the sample tested for loss is determined by the measurement set-up,
i.e. curvature radius (R) and number of turns (N); any further fibre length does not affect the
measurement results, provided that the SNR is optimised.
5.1.2 Method B – Quarter circle bends
The specimen length shall be determined according to the details shown in 6.2.
5.2 Specimen end face
Prepare a flat end face, orthogonal to the fibre axis, at the input and output ends of each test
specimen.
6 Procedure
6.1 Method A – Fibre winding
6.1.1 General consideration
Loosely wind the fibre on the tool, avoiding excessive fibre twist. The number of turns,
curvature radius and wavelength at which loss is to be measured are discussed below in 6.1.1
and in 6.1.2 and 6.1.3.
Since the actual curvature radius is critical, a maximum tolerance of ±0,1 mm (for radii lower
than or equal to 15 mm) or ±1,0 mm (for larger radii) is accepted: a tighter tolerance on small
radii is required for higher measurement sensitivity.
Both for single-mode and for multimode fibres, two optical powers can be measured using
– the power-monitoring technique, which measures the fibre attenuation increase due to a
change from the straight condition to a bent condition, or
– the cut-back technique, which measures the total attenuation of the fibre in the bent
condition. In order to determine the induced attenuation due to macrobending, this value
should be corrected for the intrinsic attenuation of the fibre.
The fibre length outside the mandrel and the reference cut-back length shall be free of bends
that can introduce a significant change in the measurement result. It is also possible to rewind

– 14 – IEC 60793-1-47:2017 © IEC 2017
the fibre from a mandrel with a large radius (introducing negligible macrobend loss) to the
mandrel with the required radius. In this case, the macrobend loss can be determined directly
by using the power-monitoring technique (without the correction for the intrinsic attenuation of
the fibre).
Care shall be taken in order not to introduce torsion on any fibre part during the
measurements, as this would affect the result.
6.1.2 Single-mode fibres
Different applications may require different deployment conditions: fibre types have been
developed which exhibit bending performances optimised for each condition.
Two typical environments are recognised for (possibly) different fibre types, for which different
measurement set-ups should be considered when characterising fibre performances.
a) Long distance networks: far from urban areas, space occupancy is not typically an issue,
and bends imposed on the fibres can be limited to relatively large radii. Fibres designed
for this application should be tested in similar conditions, i.e. with the samples wrapped
around relatively large radius mandrels, for example in the range 25 mm to 30 mm.
This measurement set-up is mainly affected by errors related to low SNR and by unwanted
tension, torsions or kinks on the relatively long fibre length used for the measurement.
b) Access networks: operating conditions require bending radii as small as possible,
compatible with lifetime expectations and acceptable bend losses. For more information
on lifetime expectations please refer to ITU-T G Suppl.59:2016. Fibres designed for this
application should be tested in similar conditions, i.e. with the samples bent at small radii,
for example in the range 7,5 mm to 15 mm (see Annex C).
The measurement can be affected by different sources, i.e. reflections, which may occur
at the coating-air or coating-glass interface, at surrounding surfaces (including, when
used, the mandrel surface), or at connectors.
The test can be carried out on samples either making complete (360º) turn(s), in open air or
around a suitable support (mandrel), or making an equivalent number of partial turns, for
example U-turns (180º) or quarter turns (90º), in open air or around suitable supports. The
length under test is different for complete and partial turns; for example, the length of a
complete turn being twice the length of a U-turn or four times the length of a quarter turn. In
this document, the term "coil" refers to one complete turn. One coil could also be made of, for
example, two consecutive U-turns or four consecutive quarter turns. This should be taken
into account while normalising the results to the length of the sample (number of coils).
The following recommendations apply to test conditions in both cases (items a) and b) above):
Number of turns
– The number of turns should be in accordance with the values stated in the product
specification.
– For single-mode fibres, the attenuation increases in a linear fashion with the number of
turns.
– For each radius, the number of turns shall be chosen in such a way that:
• the induced loss is significantly higher than the detection limit of the set-up; when
necessary, for example for low bend loss fibres, tests may be carried out with more
turns than the specification requires – followed by linear normalization to the specified
number;
• the induced loss is significantly lower than the onset of the non-linear region in the set-
up; for bending radii in the range 5 mm to 10 mm, this may imply that not more than 5
to 10 turns should be used.
___________
If there is excessive displacement between successive U-turns, the length of the sample arranged on two
U-turns can be shorter than one coil. A maximum displacement between adjacent U-turns of 0,5 mm is
therefore suggested.
IEC 60793-1-47:2017 © IEC 2017 – 15 –
Bend radius
The value of bend radius shall be in accordance with the values stated in the product
2.
specification
Wavelength
The measurement wavelength shall be 1 550 nm or 1 625 nm, in accordance with the
relevant product specification; it should be considered that bending losses increase
exponentially with the wavelength.
The homogeneity of bend loss in d
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