IEC 60793-1-34:2021

Optical fibres - Part 1-34: Measurement methods and test procedures - Fibre curl

IEC 60793-1-34:2021 establishes uniform requirements for the mechanical characteristic: fibre curl or latent curvature in uncoated optical fibres, i.e. a specified length of the fibre has been stripped from coating. Fibre curl has been identified as an important parameter for minimizing the splice loss of optical fibres when using passive alignment fusion splicers or active alignment mass fusion splicers.Two methods are recognized for the measurement of fibre curl, in uncoated optical fibres:
- method A: side view microscopy;
- method B: laser beam scattering.
Both methods measure the radius of curvature of an uncoated fibre by determining the amount of deflection that occurs as an unsupported fibre end is rotated about the fibre's axis. Method A uses visual or digital video methods to determine the deflection of the fibre while method B uses a line sensor to measure the maximum deflection of one laser beam relative to a reference laser beam. By measuring the deflection behaviour of the fibre as it is rotated about its axis and understanding the geometry of the measuring device, the fibre's radius of curvature can be calculated from simple circular models, the derivation of which are given in Annex C. Both methods are applicable to type B optical fibres as described in IEC 60793 (all parts). Method A is the reference test method, used to resolve disputes. This third edition cancels and replaces the second edition published in 2006. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- modification of several derivation equations for laser scattering;
- change of angular increment from 10° to 30° to 10° to 45°;
- change of Annex B from informative to normative.

Fibres optiques - Partie 1-34: Méthodes de mesure et procédures d'essai - Ondulation de la fibre

L'IEC 60793-1-34:2021 établit des exigences uniformes pour les caractéristiques mécaniques: ondulation de fibre ou courbure latente des fibres optiques sans revêtement, c'est-à-dire qu'une longueur spécifiée de la fibre a été dénudée. L'ondulation de fibre a été définie comme étant un paramètre important de réduction des pertes d'épissure des fibres optiques lors de l'utilisation de soudeuses par fusion avec alignement passif ou de soudeuses par fusion de masse avec alignement actif. Deux méthodes sont reconnues pour la mesure de l'ondulation de fibre, pour les fibres optiques sans revêtement:
- méthode A: par microscopie latérale;
- méthode B: par diffusion d'un faisceau laser.
Les deux méthodes mesurent le rayon de courbure d'une fibre sans revêtement en déterminant la valeur de la flèche d'une extrémité de fibre non soutenue soumise à une rotation autour de son axe. La méthode A utilise des méthodes visuelles ou vidéo numériques pour déterminer la flèche de la fibre tandis que la méthode B utilise un capteur de ligne pour mesurer la flèche maximale d’un faisceau laser par rapport à un faisceau laser de référence. En mesurant le comportement de la flèche de la fibre pendant qu’elle est soumise à une rotation autour de son axe et d’après la configuration du dispositif de mesure, le rayon de courbure de la fibre peut être calculé à partir de modèles circulaires simples, déterminés à l’Annexe C. Ces deux méthodes sont applicables aux fibres optiques du type B telles que décrites dans la série IEC 60793 (toutes les parties). La méthode A est la méthode d'essai de référence, utilisée en cas de litige. Cette troisième édition annule et remplace la deuxième édition parue en 2006. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- modification de plusieurs équations de détermination pour la diffusion laser;
- modification de l'incrément angulaire qui passe de 10° à 30° à 10° à 45°;
- changement de statut de l'Annexe B qui devient normative.

General Information

• Status: Published
• Publication Date: 09-Feb-2021
• 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: 10-Feb-2021
• Completion Date: 04-Mar-2021

Relations

• Revises: IEC 60793-1-34:2006 - Optical fibres - Part 1-34: Measurement methods and test procedures - Fibre curl
• Effective Date: 05-Sep-2023

Overview

IEC 60793-1-34:2021 - Optical fibres - Part 1-34: Measurement methods and test procedures - Fibre curl defines uniform requirements and test methods for measuring fibre curl (latent curvature) in uncoated optical fibres. Fibre curl is a critical mechanical parameter that affects splice loss when using passive alignment fusion splicers or active alignment mass fusion splicers. This third edition (2021) updates measurement equations and test details from the 2006 edition.

Key topics and technical requirements

• Scope and purpose

  • Measurement of fibre curl (radius of curvature) for uncoated optical fibres (types A1, A2, A3 and B as per IEC 60793).
  • Method A (reference): side view microscopy (visual/digital video).
  • Method B: laser beam scattering using a line sensor.

• Measurement principle

  • An uncoated fibre end is mounted in a rotatable fixture with a specified overhang. The fibre is rotated about its axis and the deflection of the free end is recorded.
  • Typical measurement distance from fixture to measurement point: 10 mm to 20 mm. Excessive overhang risks vibration/gravity effects.

• Apparatus and procedure

  • Fibre holding fixture (v-groove, vacuum chuck or ferrule) and a rotator (manual or stepper motor).
  • Deflection measurement via side-view optics or laser detector; data optionally captured and processed by a computer.
  • Radius of curvature is calculated from the measured deflection using circular models derived in Annex C.

• Techniques and calculations

  • Two analysis techniques are described: extrema technique and Fourier fitting.
  • Annex C provides derivations of circular models for both microscopy and laser-scattering methods.
  • Method A is the reference test used to resolve disputes.

• Notable changes in the 2021 edition

  • Modified derivation equations for laser scattering.
  • Change of angular increment from previous ranges to 10° to 45°.
  • Annex B (laser beam scattering) changed from informative to normative.

Practical applications and who uses this standard

• Primary users

  • Optical-fibre manufacturers and production testing labs.
  • Quality assurance engineers and R&D teams evaluating fibre geometry and process control.
  • Fusion splicer and alignment system designers concerned with minimizing splice loss.
  • Telecom and datacom installers or specifiers verifying component compliance.

• Practical value

  • Ensures consistent, reproducible measurement of fibre curl for manufacturing quality control.
  • Reduces splice-loss variability by controlling curvature-related misalignment.
  • Provides standardized methods for contract testing, dispute resolution and product specifications.

Related standards

• IEC 60793 (all parts) - general series for Optical fibres; IEC 60793-1-34:2021 references and applies within this framework.

Keywords: IEC 60793-1-34:2021, optical fibre, fibre curl, measurement methods, side view microscopy, laser beam scattering, splice loss, radius of curvature, fusion splicer, uncoated optical fibres.

Standards Content (Sample)

IEC 60793-1-34 ®
Edition 3.0 2021-02
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Optical fibres –
Part 1-34: Measurement methods and test procedures – Fibre curl

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC online collection - oc.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc

If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: [e-mail].
IEC 60793-1-34 ®
Edition 3.0 2021-02
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Optical fibres –
Part 1-34: Measurement methods and test procedures – Fibre curl

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.10 ISBN 978-2-8322-9430-7

– 2 – IEC 60793-1-34:2021 RLV  IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Apparatus . 7
4.1 Principle . 7
4.2 Fibre holding fixture . 7
4.3 Fibre rotator . 7
4.4 Deflection measurement device . 7
4.5 Computer (optional) . 7
5 Sample preparation . 7
6 Procedure . 7
6.1 General . 7
6.2 Mounting of the fibre . 7
6.3 Rotation . 8
7 Calculation . 8
8 Result . 8
9 Specification information . 8
Annex A (normative) Fibre curl by side view microscopy . 9
A.1 Principle . 9
A.2 Apparatus . 10
A.2.1 Deflection measurement device . 10
A.2.2 Video camera and monitor . 11
A.2.3 Digital image analysis system (optional) . 11
A.3 Test procedure . 11
A.3.1 General . 11
A.3.2 Procedure for the extrema technique . 11
A.3.3 Procedure for the Fourier fitting technique . 11
A.4 Calculations . 11
A.4.1 Extrema technique calculation . 11
A.4.2 Fourier fitting technique calculation . 11
A.4.3 Computation of fibre curl. 12
Annex B (informative normative) Fibre curl by laser beam scattering . 13
B.1 Principle . 13
B.2 Apparatus . 13
B.2.1 Light source . 13
B.2.2 Detector . 13
B.3 Test procedure . 13
B.3.1 General . 13
B.3.2 Procedure for the extrema technique . 13
B.3.3 Procedure for the Fourier fitting technique . 13
B.4 Calculations . 13
B.4.1 Extrema technique calculation . 13
B.4.2 Fourier fitting technique calculation . 14
B.4.3 Computation of fibre curl. 14

Annex C (informative) Derivation of the circular fibre curl model . 15
C.1 Derivation of equations for side view microscopy . 15
C.2 Derivation of equations for the laser scattering method . 16

Figure A.1 – Schematic diagram for apparatus to measure fibre curl using an optical
microscope . 9
Figure A.2 – Schematic diagram for apparatus to measure fibre curl using a laser
micrometer. 10
Figure A.3 – Schematic diagram for apparatus to measure fibre curl while securing the

sample in a ferrule . 10
Figure B.1 – Schematic diagram of optical curl by laser beam scattering . 14
Figure C.1 – Geometrical layout of side view microscopy fibre curl measurement . 15
Figure C.2 – Geometrical layout of laser scattering fibre curl measurement . 16

– 4 – IEC 60793-1-34:2021 RLV  IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-34: Measurement methods and test procedures – Fibre curl

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.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition IEC 60793-1-34:2006. A vertical bar appears in the margin
wherever a change has been made. Additions are in green text, deletions are in
strikethrough red text.
International Standard IEC 60793-1-34 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This third edition cancels and replaces the second edition published in 2006. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) modification of several derivation equations for laser scattering;
b) change of angular increment from 10° to 30° to 10° to 45°;
c) change of Annex B from informative to normative.
The text of this International Standard is based on the following documents:
CDV Report on voting
86A/1971/CDV 86A/1994/RVC
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.
A list of all parts in the 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.

– 6 – IEC 60793-1-34:2021 RLV  IEC 2021
OPTICAL FIBRES –
Part 1-34: Measurement methods and test procedures – Fibre curl

1 Scope
This part of IEC 60793 establishes uniform requirements for the mechanical characteristic: fibre
curl or latent curvature in uncoated optical fibres, i.e. a specified length of the fibre has been
stripped from coating. Fibre curl has been identified as an important parameter for minimizing
the splice loss of optical fibres when using passive alignment fusion splicers or active alignment
mass fusion splicers.
Two methods are recognized for the measurement of fibre curl, in uncoated optical fibres:
• method A: side view microscopy;
• method B: laser beam scattering.
Both methods measure the radius of curvature of an uncoated fibre by determining the amount
of deflection that occurs as an unsupported fibre end is rotated about the fibre's axis. Method A
uses visual or digital video methods to determine the deflection of the fibre while method B uses
a line sensor to measure the maximum deflection of one laser beam relative to a reference laser
beam.
By measuring the deflection behaviour of the fibre as it is rotated about its axis and
understanding the geometry of the measuring device, the fibre's radius of curvature can be
calculated from simple circular models, the derivation of which are given in Annex C.
Both methods are applicable to types A1, A2, A3 and B optical fibres as described in
IEC 60793 (all parts).
Method A is the reference test method, used to resolve disputes.
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 (all parts), Optical fibres
3 Terms and definitions
No terms and definitions are listed in this document.
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

4 Apparatus
4.1 Principle
An uncoated fibre end is mounted in a rotatable fixture so that the end extends freely into space
by an overhang distance which will depend on the measurement device. The overhang distance
is from the fibre fixture to the free endface of the uncoated fibre. The measurement distance
from the fibre fixture to the measurement point is typically 10 mm to 20 mm, and the
measurement point shall be close to the fibre's free endface. If the measurement device is
designed with overhang measurement distances greater than this, care must shall be taken to
avoid excessive degradation due to effects of vibration and gravity. The fibre is rotated and the
deviations in the position of the overhang test point relative to a reference position are
measured to obtain the fibre's radius of curvature, r .
c
Details pertaining to the two methods are given in the relevant Annex A or Annex B. Common
apparatus requirements are given in 4.2 to 4.5.
4.2 Fibre holding fixture
Provide a fixture that holds the fibre on a constant axis at the holding position and allows the
fibre to be rotated through 360°. The fixture may be a v-groove holder such as a vacuum chuck
or a fibre ferrule. If a ferrule is used, take care to ensure that the inside diameter is sized closely
enough to the fibre diameter to minimize variability in the deflection measurements.
4.3 Fibre rotator
Provide a device to grip and rotate the fibre through 360°. The device may be manually operated,
or it may be driven by a rotational device such as a stepper motor.
4.4 Deflection measurement device
Provide a deflection measurement device according to either Annex A or Annex B.
4.5 Computer (optional)
A computer may be used to provide motion control, data collection and computation.
5 Sample preparation
Use an uncabled fibre of appropriate length for the instrument design. Remove enough coating
from one end to allow mounting in the fibre fixture with the necessary overhang. The fibre should
not extend much past the measuring device's required overhang measurement distance since
excessive lengths can cause degradation as discussed in 4.1.
6 Procedure
6.1 General
Details for each method are given in Annex A and Annex B. Common procedures are described
in 6.1 and 6.2.
6.2 Mounting of the fibre
Mount the fibre in the holding fixture so that the stripped end extends into free space with
sufficient length to extend up to or beyond the overhang measurement distance. Typical
overhang measurement distances range between 10 mm and 20 mm. Attach the other end of
the fibre to the fibre rotator. If the overhang measurement distance is excessive, or the stripped

– 8 – IEC 60793-1-34:2021 RLV  IEC 2021
fibre is substantially longer than the required overhang measurement distance, then the
measurement may be degraded.
6.3 Rotation
Follow the procedure of Annex A or Annex B.
7 Calculation
Complete the detailed calculation of the fibre curl, r , using Annex A or Annex B.
c
NOTE Though the intermediate parameters used in the calculations are typically scaled in micrometres, the radius
of curvature, r , is typically re-scaled in units of metres.
c
8 Result
8.1 The following information should be reported for each test:
• date of the test;
• fibre identification;
• fibre radius of curvature.
8.2 The following information should be available for each test:
• method used to determine curl;
• technique used for calculations;
• description of the equipment;
• calibration data.
9 Specification information
The detail specification shall specify the following:
• information to be reported;
• any deviations to the procedure that apply;
• failure or acceptance criteria.

Annex A
(normative)
Fibre curl by side view microscopy
A.1 Principle
This procedure measures the radius of curvature of an uncoated fibre by determining the
amount of deflection that occurs as an unsupported fibre end is rotated about the fibre's axis.
By knowing the amplitude of the deflection of the fibre and the overhang measurement distance
from the fibre fixture to the measurement point, the fibre's radius of curvature can be calculated
from a simple circular model, the derivation of which is given in Clause C.1. Schematic diagrams
of typical test set-ups for these techniques are shown in Figure A.1, Figure A.2 and Figure A.3.

Figure A.1 – Schematic diagram for apparatus to measure fibre curl
using an optical microscope
– 10 – IEC 60793-1-34:2021 RLV  IEC 2021

Figure A.2 – Schematic diagram for apparatus to measure fibre curl
using a laser micrometre
Figure A.3 – Schematic diagram for apparatus to measure fibre curl
while securing the sample in a ferrule
A.2 Apparatus
A.2.1 Deflection measurement device
Provide a device to measure the fibre deflection as it is rotated through 360°. Such a device
may consist of a viewing microscope or an optical measuring instrument such as a laser
micrometre. If a viewing microscope is used, provide means to permit accurate measurement
of fibre deflection, such as a filar eyepiece or a digital image analysis system.

A.2.2 Video camera and monitor
A video camera and monitor may be used to enhance the viewing system for manual or
automated operation.
A.2.3 Digital image analysis system (optional)
A digital video analyser may be used to provide more precise location of the deflections than
might be obtained by a filar eyepiece. Such a system might include an analogue or digital video
camera, a frame grabber and associated software for the purpose of locating the fibre's position
at the overhang measurement distance as the fibre is rotated.
A.3 Test procedure
A.3.1 General
Two techniques are provided for obtaining the deflection, δ . The first is an extrema technique
f
that is limited by the precision with which the extremes of the deflection can be determined.
The second is a Fourier fitting method.
A.3.2 Procedure for the extrema technique
Rotate the specimen until the deflection is at a maximum and record the deflection value, D .
max
Rotate the specimen until the deflection is at a minimum, typically 180° from the angular position
of the maximum, and record the deflection value, D .
min
A.3.3 Procedure for the Fourier fitting technique
Record the deflection of the specimen at its initial position, D , and angular position, θ . Rotate
1 1
the specimen through 360° (do not duplicate the initial position in the data as the last angular
position), stopping at equal angular increments and recording the deflection values at each
increment, D , and its angular positions, θ . Angular increments of 10° to 30 45° are
2.n 2.n
typically used.
A.4 Calculations
A.4.1 Extrema technique calculation
The fibre deflection δ is calculated by Formula (A.1):
f
DD−
max min
δ =
(A.1)
f
where
D and D are the maximum and minimum deflection values, generally described in
max min
micrometres.
A.4.2 Fourier fitting technique calculation
Compute the first order Fourier coefficients:
n
I = D × sinθ
(A.2)
1 ∑ i i
n
i=1
– 12 – IEC 60793-1-34:2021 RLV  IEC 2021
n
R = D × cosθ (A.3)
1 ∑ ii
n
i=1
Compute δ as the magnitude of the first-order Fourier component:
f
δ = R + I (A.4)
f 11
Least squares fitting of the set of θ and D may be used as an alternative. The Fourier technique
i i
described in A.4.2 and least squares fitting of the amplitude and phase are numerically
equivalent.
A.4.3 Computation of fibre curl
Fibre curl, r , is computed as:
c
Z + δ
mf
r = (A.5)
c
2δ
f
where
Z is the overhang measurement distance.
m
Annex B
(informative normative)
Fibre curl by laser beam scattering
B.1 Principle
This procedure measures the latent curvature (curl) in an optical fibre by laser beam scattering.
This procedure measures the radius of curvature of an uncoated fibre by determining the
amount of deflection that occurs as an unsupported fibre end is rotated about the fibre's axis.
By measuring the differential deflection of two beams separated by a known distance and the
geometry of the measuring device, the fibre's radius of curvature can be calculated from a
simple circular model, the derivation of which is given in Clause C.2. A schematic diagram is
shown in Figure B.1.
B.2 Apparatus
B.2.1 Light source
Split He-Ne laser beams are used as the light source.
B.2.2 Detector
An image sensor such as CCD line sensor is used as the detector.
B.3 Test procedure
B.3.1 General
Two techniques are provided for obtaining the deflection difference, ΔS. The first is an extrema
technique that is limited by the precision with which the extremes of the deflection can be
determined. The second is a Fourier fitting method.
B.3.2 Procedure for the extrema technique
Rotate the specimen until the deflection is at a maximum and record the deflection value, ΔS .
max
B.3.3 Procedure for the Fourier fitting technique
Record the deflection of the specimen at its initial position, ΔS , and angular position, θ . Rotate
1 1
the specimen through 360° (do not duplicate the initial position in the data as the last angular
position), stopping at equal angular increments and recording the deflection values at each
increment, ΔS , and its angular positions, θ . Angular increments of 10° to 30 45° are
2.n 2.n
typically used.
B.4 Calculations
B.4.1 Extrema technique calculation
(B.1)
SS=∆∆- Z
A max
where
ΔZ is the separation distance of the two laser beams.

– 14 – IEC 60793-1-34:2021 RLV  IEC 2021
B.4.2 Fourier fitting technique calculation
Compute the first order Fourier coefficients:
n
I ∆S × sinθ (B.2)
1 ∑ i i
n
i=1
n
R ∆S × cosθ (B.3)
1 ii
∑
n
i=1
Compute ΔS S as the magnitude of the first-order Fourier component:
A
S = R + I (B.4)
A 11
Least squares fitting of the set of θ and (ΔS – ΔZ) may be used as an alternative. The Fourier
i i
technique described above and least squares fitting of the amplitude and phase are numerically
equivalent.
B.4.3 Computation of fibre curl
2LZ∆
r ≈ (B.5)
c
S
A
where
L is the distance between the fibre and the line sensor;
ΔZ is the laser beam separation distance.

Figure B.1 – Schematic diagram of optical curl by laser beam scattering

=
=
Annex C
(informative)
Derivation of the circular fibre curl model
C.1 Derivation of equations for side view microscopy
Figure C.1 shows the geometrical layout of side view microscopy fibre curl measurement.

Figure C.1 – Geometrical layout of side view microscopy fibre curl measurement
We define the following:
Z is the overhang measurement distance;
m
δ is the fibre deflection from the fibre holder’s axis measured at Z ;
f m
C is the hypotenuse of right triangle formed by Z , δ and C.
,
m f
Therefore,
CZ= + δ (C.1)
mf
Form an isosceles triangle with C as the base and sides r extending from the centre of the
c
circle. Bisect C and form two right triangles from the isosceles triangle. Angle â of the newly
formed right triangles is equal to angle â of the Z , δ and C right triangle.

m f
Therefore,
δ ½ C
f
sinâ  (C.2)
Cr
c
= =
– 16 – IEC 60793-1-34:2021 RLV  IEC 2021
Substituting Formula (C.1) into Formula (C.2) gives:
Z + δ
mf
r =
(C.3)
c
2δ
f
C.2 Derivation of equations for the laser scattering method
Figure C.2 shows the deometrical layout of laser scattering fibre curl measurement.

Figure C.2 – Geometrical layout of laser scattering fibre curl measurement
We define the following:
ΔZ is the separation distance between the two laser beams;
L is the distance between the fibre holder's axis of rotation and the sensor plane;
Z is the distance from the fibre holder to the first beam's impingement point.
G
Note that:
(C.4)
∆=SZ - Z
ω
 
Z = LZ+ tan tan2ω (C.5)
1G 1
 
 
 ω 
Z=L + (∆∆ZZ+ )tan tan2ω + Z (C.6)
1G 2
 
 
The small corrections to the parameter L in Formulae (C.5) and (C.6) are due to the fact that
when the curled fibre is rotated to its maximum deflection point, the laser beams impinge on
the fibre at a distance which depends on r , Z and ΔZ. These terms are on the order of ΔZ /r
c G c,
which for practical systems are very small, and can usually be ignored.
The z-coordinates of each beam relative to the fibre constraint point are
(C.7)
Zr= sinω
Gc 1
(C.8)
∆=Zr sinω - Z
c 2G
The angle ω can be expressed two different ways:
Z
G
sinω = (C.9)
r
c
ZZ
(C.10)
tan2ω ≈
ω
L
LZ+ tan
G
Likewise, the angle ω can be expressed in two different ways:
ZZ+ ∆
G
sinω = (C.11)
r
c
ZZ--∆∆ZZ
tan2ω ≈ (C.12)
ω
L
L + (∆ZZ+ )tan
G
It is convenient to measure the difference between the deflections of the two beams, ΔS, which
will be invariant with the angle of entry of the fibre. When the fibre's curl radius is substantially
larger than the geometrical parameters L, Z and ΔZ of the measuring device, we can
G
successfully use small angle approximations to get the difference results.
If we assume for both ω and ω (a good assumption for practical fibres and implementations):
1 2
sinω ≈ ω
ω ω
tan ≈
tan2ωω≈ 2
=
=
– 18 – IEC 60793-1-34:2021 RLV  IEC 2021

then we can rewrite Formula (C.4) as:
S 2L(ωω- ) +(∆ZZ+ )ω - Z ω +∆Z (C.13)
2 1 G 2 G1
and using Formulae (C.9) and (C.11) (and the small angle approximation), we get
2LZ∆ (∆ZZ+ ) Z
GG
SZ++∆ - (C.14)
r
rr
c
cc
Inspecting Formula (C.14), we can see two cubic terms. If one considers a practical system
= 1 m) and letting ΔZ and Z be 0,01 m (1 cm), then we can see that
with a very curled fibre (r
c G
these cubic terms become very small compared with the first two terms. We can then write
SL∆Z
SZ+∆ (C.15)
r
c
and finally
2LZ∆
r = (C.16)
c
∆∆SZ-
For practical fibres and measuring device constraints, all of the above approximations will not
contribute errors in excess of hundredths of percent. For fibres with curl radii in excess of 5 m,
these errors become even smaller.

___________
∆=
∆=
∆=
IEC 60793-1-34 ®
Edition 3.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical fibres –
Part 1-34: Measurement methods and test procedures – Fibre curl

Fibres optiques –
Partie 1-34: Méthodes de mesure et procédures d’essai – Ondulation de la fibre

– 2 – IEC 60793-1-34:2021  IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Apparatus . 7
4.1 Principle . 7
4.2 Fibre holding fixture . 7
4.3 Fibre rotator . 7
4.4 Deflection measurement device . 7
4.5 Computer (optional) . 7
5 Sample preparation . 7
6 Procedure . 7
6.1 General . 7
6.2 Mounting of the fibre . 7
6.3 Rotation . 8
7 Calculation . 8
8 Result . 8
9 Specification information . 8
Annex A (normative) Fibre curl by side view microscopy . 9
A.1 Principle . 9
A.2 Apparatus . 10
A.2.1 Deflection measurement device . 10
A.2.2 Video camera and monitor . 11
A.2.3 Digital image analysis system (optional) . 11
A.3 Test procedure . 11
A.3.1 General . 11
A.3.2 Procedure for the extrema technique . 11
A.3.3 Procedure for the Fourier fitting technique . 11
A.4 Calculations . 11
A.4.1 Extrema technique calculation . 11
A.4.2 Fourier fitting technique calculation . 11
A.4.3 Computation of fibre curl. 12
Annex B (normative) Fibre curl by laser beam scattering . 13
B.1 Principle . 13
B.2 Apparatus . 13
B.2.1 Light source . 13
B.2.2 Detector . 13
B.3 Test procedure . 13
B.3.1 General . 13
B.3.2 Procedure for the extrema technique . 13
B.3.3 Procedure for the Fourier fitting technique . 13
B.4 Calculations . 13
B.4.1 Extrema technique calculation . 13
B.4.2 Fourier fitting technique calculation . 14
B.4.3 Computation of fibre curl. 14

Annex C (informative) Derivation of the circular fibre curl model . 15
C.1 Derivation of equations for side view microscopy . 15
C.2 Derivation of equations for the laser scattering method . 16

Figure A.1 – Schematic diagram for apparatus to measure fibre curl using an optical
microscope . 9
Figure A.2 – Schematic diagram for apparatus to measure fibre curl using a laser
micrometer. 10
Figure A.3 – Schematic diagram for apparatus to measure fibre curl while securing the

sample in a ferrule . 10
Figure B.1 – Schematic diagram of optical curl by laser beam scattering . 14
Figure C.1 – Geometrical layout of side view microscopy fibre curl measurement . 15
Figure C.2 – Geometrical layout of laser scattering fibre curl measurement . 16

– 4 – IEC 60793-1-34:2021  IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-34: Measurement methods and test procedures – Fibre curl

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 60793-1-34 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This third edition cancels and replaces the second edition published in 2006. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) modification of several derivation equations for laser scattering;
b) change of angular increment from 10° to 30° to 10° to 45°;
c) change of Annex B from informative to normative.
The text of this International Standard is based on the following documents:
CDV Report on voting
86A/1971/CDV 86A/1994/RVC
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 b
...

IEC 60793-1-34 ®
Edition 3.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical fibres –
Part 1-34: Measurement methods and test procedures – Fibre curl

Fibres optiques –
Partie 1-34: Méthodes de mesure et procédures d’essai – Ondulation de la fibre

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC online collection - oc.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always have
committee, …). It also gives information on projects, replaced access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and once
and French, with equivalent terms in 18 additional languages.
a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or need
further assistance, please contact the Customer Service
Centre: [e-mail].
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - Découvrez notre puissant moteur de recherche et consultez
webstore.iec.ch/advsearchform gratuitement tous les aperçus des publications. Avec un
La recherche avancée permet de trouver des publications IEC abonnement, vous aurez toujours accès à un contenu à jour
en utilisant différents critères (numéro de référence, texte, adapté à vos besoins.
comité d’études, …). Elle donne aussi des informations sur les
projets et les publications remplacées ou retirées. Electropedia - www.electropedia.org

Le premier dictionnaire d'électrotechnologie en ligne au monde,
IEC Just Published - webstore.iec.ch/justpublished
avec plus de 22 000 articles terminologiques en anglais et en
Restez informé sur les nouvelles publications IEC. Just
français, ainsi que les termes équivalents dans 16 langues
Published détaille les nouvelles publications parues.
additionnelles. Egalement appelé Vocabulaire
Disponible en ligne et une fois par mois par email.
Electrotechnique International (IEV) en ligne.

Service Clients - webstore.iec.ch/csc
Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
[e-mail].
IEC online collection - oc.iec.ch

IEC 60793-1-34 ®
Edition 3.0 2021-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical fibres –
Part 1-34: Measurement methods and test procedures – Fibre curl

Fibres optiques –
Partie 1-34: Méthodes de mesure et procédures d’essai – Ondulation de la fibre

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.10 ISBN 978-2-8322-9396-6

– 2 – IEC 60793-1-34:2021  IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Apparatus . 7
4.1 Principle . 7
4.2 Fibre holding fixture . 7
4.3 Fibre rotator . 7
4.4 Deflection measurement device . 7
4.5 Computer (optional) . 7
5 Sample preparation . 7
6 Procedure . 7
6.1 General . 7
6.2 Mounting of the fibre . 7
6.3 Rotation . 8
7 Calculation . 8
8 Result . 8
9 Specification information . 8
Annex A (normative) Fibre curl by side view microscopy . 9
A.1 Principle . 9
A.2 Apparatus . 10
A.2.1 Deflection measurement device . 10
A.2.2 Video camera and monitor . 11
A.2.3 Digital image analysis system (optional) . 11
A.3 Test procedure . 11
A.3.1 General . 11
A.3.2 Procedure for the extrema technique . 11
A.3.3 Procedure for the Fourier fitting technique . 11
A.4 Calculations . 11
A.4.1 Extrema technique calculation . 11
A.4.2 Fourier fitting technique calculation . 11
A.4.3 Computation of fibre curl. 12
Annex B (normative) Fibre curl by laser beam scattering . 13
B.1 Principle . 13
B.2 Apparatus . 13
B.2.1 Light source . 13
B.2.2 Detector . 13
B.3 Test procedure . 13
B.3.1 General . 13
B.3.2 Procedure for the extrema technique . 13
B.3.3 Procedure for the Fourier fitting technique . 13
B.4 Calculations . 13
B.4.1 Extrema technique calculation . 13
B.4.2 Fourier fitting technique calculation . 14
B.4.3 Computation of fibre curl. 14

Annex C (informative) Derivation of the circular fibre curl model . 15
C.1 Derivation of equations for side view microscopy . 15
C.2 Derivation of equations for the laser scattering method . 16

Figure A.1 – Schematic diagram for apparatus to measure fibre curl using an optical
microscope . 9
Figure A.2 – Schematic diagram for apparatus to measure fibre curl using a laser
micrometer. 10
Figure A.3 – Schematic diagram for apparatus to measure fibre curl while securing the

sample in a ferrule . 10
Figure B.1 – Schematic diagram of optical curl by laser beam scattering . 14
Figure C.1 – Geometrical layout of side view microscopy fibre curl measurement . 15
Figure C.2 – Geometrical layout of laser scattering fibre curl measurement . 16

– 4 – IEC 60793-1-34:2021  IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-34: Measurement methods and test procedures – Fibre curl

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 60793-1-34 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This third edition cancels and replaces the second edition published in 2006. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) modification of several derivation equations for laser scattering;
b) change of angular increment from 10° to 30° to 10° to 45°;
c) change of Annex B from informative to normative.
The text of this International Standard is based on the following documents:
CDV Report on voting
86A/1971/CDV 86A/1994/RVC
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.
A list of all parts in the 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.

– 6 – IEC 60793-1-34:2021  IEC 2021
OPTICAL FIBRES –
Part 1-34: Measurement methods and test procedures – Fibre curl

1 Scope
This part of IEC 60793 establishes uniform requirements for the mechanical characteristic: fibre
curl or latent curvature in uncoated optical fibres, i.e. a specified length of the fibre has been
stripped from coating. Fibre curl has been identified as an important parameter for minimizing
the splice loss of optical fibres when using passive alignment fusion splicers or active alignment
mass fusion splicers.
Two methods are recognized for the measurement of fibre curl, in uncoated optical fibres:
• method A: side view microscopy;
• method B: laser beam scattering.
Both methods measure the radius of curvature of an uncoated fibre by determining the amount
of deflection that occurs as an unsupported fibre end is rotated about the fibre's axis. Method A
uses visual or digital video methods to determine the deflection of the fibre while method B uses
a line sensor to measure the maximum deflection of one laser beam relative to a reference laser
beam.
By measuring the deflection behaviour of the fibre as it is rotated about its axis and
understanding the geometry of the measuring device, the fibre's radius of curvature can be
calculated from simple circular models, the derivation of which are given in Annex C.
Both methods are applicable to type B optical fibres as described in IEC 60793 (all parts).
Method A is the reference test method, used to resolve disputes.
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 (all parts), Optical fibres
3 Terms and definitions
No terms and definitions are listed in this document.
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

4 Apparatus
4.1 Principle
An uncoated fibre end is mounted in a rotatable fixture so that the end extends freely into space
by an overhang distance which will depend on the measurement device. The overhang distance
is from the fibre fixture to the free endface of the uncoated fibre. The measurement distance
from the fibre fixture to the measurement point is typically 10 mm to 20 mm, and the
measurement point shall be close to the fibre's free endface. If the measurement device is
designed with measurement distances greater than this, care shall be taken to avoid excessive
degradation due to effects of vibration and gravity. The fibre is rotated and the deviations in the
position of the test point relative to a reference position are measured to obtain the fibre's radius
of curvature, r .
c
Details pertaining to the two methods are given in the relevant Annex A or Annex B. Common
apparatus requirements are given in 4.2 to 4.5.
4.2 Fibre holding fixture
Provide a fixture that holds the fibre on a constant axis at the holding position and allows the
fibre to be rotated through 360°. The fixture may be a v-groove holder such as a vacuum chuck
or a fibre ferrule. If a ferrule is used, take care to ensure that the inside diameter is sized closely
enough to the fibre diameter to minimize variability in the deflection measurements.
4.3 Fibre rotator
Provide a device to grip and rotate the fibre through 360°. The device may be manually operated,
or it may be driven by a rotational device such as a stepper motor.
4.4 Deflection measurement device
Provide a deflection measurement device according to either Annex A or Annex B.
4.5 Computer (optional)
A computer may be used to provide motion control, data collection and computation.
5 Sample preparation
Use an uncabled fibre of appropriate length for the instrument design. Remove enough coating
from one end to allow mounting in the fibre fixture with the necessary overhang. The fibre should
not extend much past the measuring device's required measurement distance since excessive
lengths can cause degradation as discussed in 4.1.
6 Procedure
6.1 General
Details for each method are given in Annex A and Annex B. Common procedures are described
in 6.1 and 6.2.
6.2 Mounting of the fibre
Mount the fibre in the holding fixture so that the stripped end extends into free space with
sufficient length to extend up to or beyond the measurement distance. Typical measurement
distances range between 10 mm and 20 mm. Attach the other end of the fibre to the fibre rotator.

– 8 – IEC 60793-1-34:2021  IEC 2021
If the measurement distance is excessive, or the stripped fibre is substantially longer than the
required measurement distance, then the measurement may be degraded.
6.3 Rotation
Follow the procedure of Annex A or Annex B.
7 Calculation
Complete the detailed calculation of the fibre curl, r , using Annex A or Annex B.
c
NOTE Though the intermediate parameters used in the calculations are typically scaled in micrometres, the radius
of curvature, r , is typically re-scaled in units of metres.
c
8 Result
8.1 The following information should be reported for each test:
• date of the test;
• fibre identification;
• fibre radius of curvature.
8.2 The following information should be available for each test:
• method used to determine curl;
• technique used for calculations;
• description of the equipment;
• calibration data.
9 Specification information
The detail specification shall specify the following:
• information to be reported;
• any deviations to the procedure that apply;
• failure or acceptance criteria.

Annex A
(normative)
Fibre curl by side view microscopy
A.1 Principle
This procedure measures the radius of curvature of an uncoated fibre by determining the
amount of deflection that occurs as an unsupported fibre end is rotated about the fibre's axis.
By knowing the amplitude of the deflection of the fibre and the measurement distance from the
fibre fixture to the measurement point, the fibre's radius of curvature can be calculated from a
simple circular model, the derivation of which is given in Clause C.1. Schematic diagrams of
typical test set-ups for these techniques are shown in Figure A.1, Figure A.2 and Figure A.3.

Figure A.1 – Schematic diagram for apparatus to measure fibre curl
using an optical microscope
– 10 – IEC 60793-1-34:2021  IEC 2021

Figure A.2 – Schematic diagram for apparatus to measure fibre curl
using a laser micrometre
Figure A.3 – Schematic diagram for apparatus to measure fibre curl
while securing the sample in a ferrule
A.2 Apparatus
A.2.1 Deflection measurement device
Provide a device to measure the fibre deflection as it is rotated through 360°. Such a device
may consist of a viewing microscope or an optical measuring instrument such as a laser
micrometre. If a viewing microscope is used, provide means to permit accurate measurement
of fibre deflection, such as a filar eyepiece or a digital image analysis system.

A.2.2 Video camera and monitor
A video camera and monitor may be used to enhance the viewing system for manual or
automated operation.
A.2.3 Digital image analysis system (optional)
A digital video analyser may be used to provide more precise location of the deflections than
might be obtained by a filar eyepiece. Such a system might include an analogue or digital video
camera, a frame grabber and associated software for the purpose of locating the fibre's position
at the measurement distance as the fibre is rotated.
A.3 Test procedure
A.3.1 General
Two techniques are provided for obtaining the deflection, δ . The first is an extrema technique
f
that is limited by the precision with which the extremes of the deflection can be determined.
The second is a Fourier fitting method.
A.3.2 Procedure for the extrema technique
Rotate the specimen until the deflection is at a maximum and record the deflection value, D .
max
Rotate the specimen until the deflection is at a minimum, typically 180° from the angular position
of the maximum, and record the deflection value, D .
min
A.3.3 Procedure for the Fourier fitting technique
Record the deflection of the specimen at its initial position, D , and angular position, θ . Rotate
1 1
the specimen through 360° (do not duplicate the initial position in the data as the last angular
position), stopping at equal angular increments and recording the deflection values at each
increment, D , and its angular positions, θ . Angular increments of 10° to 45° are typically
2.n 2.n
used.
A.4 Calculations
A.4.1 Extrema technique calculation
The fibre deflection δ is calculated by Formula (A.1):
f
DD−
max min
δ = (A.1)
f
where
D and D are the maximum and minimum deflection values, generally described in
max min
micrometres.
A.4.2 Fourier fitting technique calculation
Compute the first order Fourier coefficients:
n
I = D × sinθ (A.2)
1 ∑ i i
n
i=1
– 12 – IEC 60793-1-34:2021  IEC 2021
n
R = D × cosθ
(A.3)
1 ∑ ii
n
i=1
Compute δ as the magnitude of the first-order Fourier component:
f
δ = R + I (A.4)
f 11
Least squares fitting of the set of θ and D may be used as an alternative. The Fourier technique
i i
described in A.4.2 and least squares fitting of the amplitude and phase are numerically
equivalent.
A.4.3 Computation of fibre curl
Fibre curl, r , is computed as:
c
Z +δ
mf
r = (A.5)
c
2δ
f
where
Z is the measurement distance.
m
Annex B
(normative)
Fibre curl by laser beam scattering
B.1 Principle
This procedure measures the latent curvature (curl) in an optical fibre by laser beam scattering.
This procedure measures the radius of curvature of an uncoated fibre by determining the
amount of deflection that occurs as an unsupported fibre end is rotated about the fibre's axis.
By measuring the differential deflection of two beams separated by a known distance and the
geometry of the measuring device, the fibre's radius of curvature can be calculated from a
simple circular model, the derivation of which is given in Clause C.2. A schematic diagram is
shown in Figure B.1.
B.2 Apparatus
B.2.1 Light source
Split He-Ne laser beams are used as the light source.
B.2.2 Detector
An image sensor such as CCD line sensor is used as the detector.
B.3 Test procedure
B.3.1 General
Two techniques are provided for obtaining the deflection difference, ΔS. The first is an extrema
technique that is limited by the precision with which the extremes of the deflection can be
determined. The second is a Fourier fitting method.
B.3.2 Procedure for the extrema technique
Rotate the specimen until the deflection is at a maximum and record the deflection value, ΔS .
max
B.3.3 Procedure for the Fourier fitting technique
Record the deflection of the specimen at its initial position, ΔS , and angular position, θ . Rotate
1 1
the specimen through 360° (do not duplicate the initial position in the data as the last angular
position), stopping at equal angular increments and recording the deflection values at each
increment, ΔS , and its angular positions, θ . Angular increments of 10° to 45° are typically
2.n 2.n
used.
B.4 Calculations
B.4.1 Extrema technique calculation
(B.1)
SS=∆∆- Z
A max
where
ΔZ is the separation distance of the two laser beams.

– 14 – IEC 60793-1-34:2021  IEC 2021
B.4.2 Fourier fitting technique calculation
Compute the first order Fourier coefficients:
n
I ∆S × sinθ
(B.2)
1 ∑ i i
n
i=1
n
R ∆S × cosθ
(B.3)
1 ∑ ii
n
i=1
Compute S as the magnitude of the first-order Fourier component:
A
S = R + I (B.4)
A 11
Least squares fitting of the set of θ and (ΔS – ΔZ) may be used as an alternative. The Fourier
i i
technique described above and least squares fitting of the amplitude and phase are numerically
equivalent.
B.4.3 Computation of fibre curl
2LZ∆
r ≈ (B.5)
c
S
A
where
L is the distance between the fibre and the line sensor;
ΔZ is the laser beam separation distance.

Figure B.1 – Schematic diagram of optical curl by laser beam scattering

=
=
Annex C
(informative)
Derivation of the circular fibre curl model
C.1 Derivation of equations for side view microscopy
Figure C.1 shows the geometrical layout of side view microscopy fibre curl measurement.

Figure C.1 – Geometrical layout of side view microscopy fibre curl measurement
We define the following:
Z is the measurement distance;
m
δ is the fibre deflection from the fibre holder’s axis measured at Z ;
f m
C is the hypotenuse of right triangle formed by Z , δ and C.
,
m f
Therefore,
CZ= +δ (C.1)
mf
Form an isosceles triangle with C as the base and sides r extending from the centre of the
c
circle. Bisect C and form two right triangles from the isosceles triangle. Angle â of the newly
formed right triangles is equal to angle â of the Z , δ and C right triangle.

m f
Therefore,
δ ½ C
f
sinâ  (C.2)
Cr
c
==
– 16 – IEC 60793-1-34:2021  IEC 2021
Substituting Formula (C.1) into Formula (C.2) gives:
Z +δ
mf
r = (C.3)
c
2δ
f
C.2 Derivation of equations for the laser scattering method
Figure C.2 shows the deometrical layout of laser scattering fibre curl measurement.

Figure C.2 – Geometrical layout of laser scattering fibre curl measurement
We define the following:
ΔZ is the separation distance between the two laser beams;
L is the distance between the fibre holder's axis of rotation and the sensor plane;
is the distance from the fibre holder to the first beam's impingement point.
Z
G
Note that:
∆=SZ - Z (C.4)
ω
 
Z = LZ+ tan tan2ω (C.5)
1G 1
 
 
 ω 
Z=L + (∆∆ZZ+ )tan tan2ω + Z (C.6)
1G 2
 
 
The small corrections to the parameter L in Formulae (C.5) and (C.6) are due to the fact that
when the curled fibre is rotated to its maximum deflection point, the laser beams impinge on
the fibre at a distance which depends on r , Z and ΔZ. These terms are on the order of ΔZ /r
c G c,
which for practical systems are very small, and can usually be ignored.
The z-coordinates of each beam relative to the fibre constraint point are
Zr= sinω (C.7)
Gc 1
∆=Zr sinω - Z (C.8)
c 2G
The angle ω can be expressed two different ways:
Z
G
sinω = (C.9)
r
c
ZZ
tan2ω ≈
(C.10)
ω
L
LZ+ tan
G
Likewise, the angle ω can be expressed in two different ways:
ZZ+∆
G
sinω = (C.11)
r
c
ZZ--∆∆ZZ
tan2ω ≈ (C.12)
ω
L
L + (∆ZZ+ )tan
G
It is convenient to measure the difference between the deflections of the two beams, ΔS, which
will be invariant with the angle of entry of the fibre. When the fibre's curl radius is substantially
larger than the geometrical parameters L, Z and ΔZ of the measuring device, we can
G
successfully use small angle approximations to get the difference results.
If we assume for both ω and ω (a good assumption for practical fibres and implementations):
1 2
sinω≈ω
ω ω
tan ≈
tan2ωω≈ 2
=
=
– 18 – IEC 60793-1-34:2021  IEC 2021

then we can rewrite Formula (C.4) as:
S 2L(ωω- ) +(∆ZZ+ )ω - Z ω +∆Z (C.13)
2 1 G 2 G1
and using Formulae (C.9) and (C.11) (and the small angle approximation), we get
2LZ∆ (∆ZZ+ ) Z
GG
SZ++∆ - (C.14)
r
rr
c
cc
Inspecting Formula (C.14), we can see two cubic terms. If one considers a practical system
= 1 m) and letting ΔZ and Z be 0,01 m (1 cm), then we can see that
with a very curled fibre (r
c G
these cubic terms become very small compared with the first two terms. We can then write
SL∆Z
(C.15)
SZ+∆
r
c
and finally
2LZ∆
r = (C.16)
c
∆∆SZ-
For practical fibres and measuring device constraints, all of the above approximations will not
contribute errors in excess of hundredths of percent. For fibres with curl radii in excess of 5 m,
these errors become even smaller.

___________
∆=
∆=
∆=
– 20 – IEC 60793-1-34:2021  IEC 2021

SOMMAIRE
AVANT-PROPOS . 22
1 Domaine d’application . 24
2 Références normatives . 24
3 Termes et définitions . 24
4 Appareillage . 25
4.1 Principe . 25
4.2 Dispositif de fixation de la fibre . 25
4.3 Dispositif de rotation de la fibre. 25
4.4 Dispositif de mesure de la flèche . 25
4.5 Ordinateur (facultatif) . 25
5 Préparation de l'échantillon . 25
6 Mode opératoire . 26
6.1 Généralités . 26
6.2 Montage de la fibre . 26
6.3 Rotation . 26
7 Calcul . 26
8 Résultat . 26
9 Informations à mentionner dans la spécification . 26
Annexe A (normative) Mesure de l'ondulation de fibre par microscopie latérale . 27
A.1 Principe . 27
A.2 Appareillage . 28
A.2.1 Dispositif de mesure de la flèche . 28
A.2.2 Caméra vidéo et moniteur . 29
A.2.3 Système d'analyse d'image numérique (facultatif) . 29
A.3 Procédure d'essai . 29
A.3.1 Généralités . 29
A.3.2 Procédure pour la technique des extrêmes . 29
A.3.3 Procédure pour la technique d'ajustement de Fourier . 29
A.4 Calculs . 29
A.4.1 Calcul pour la technique des extrêmes . 29
A.4.2 Calcul pour la technique d'ajustement de Fourier . 29
A.4.3 Calcul de l’ondulation de la fibre . 30
Annexe B (normative) Mesure de l'ondulation de fibre par diffusion d'un faisceau laser . 31
B.1 Principe . 31
B.2 Appareillage . 31
B.2.1 Source de rayonnement lumineux . 31
B.2.2 Détecteur . 31
B.3 Procédure d'essai . 31
B.3.1 Généralités . 31
B.3.2 Procédure pour la technique des extrêmes . 31
B.3.3 Procédure pour la technique d'ajustement de Fourier . 31
B.4 Calculs . 31
B.4.1 Calcul pour la technique des extrêmes . 31
B.4.2 Calcul pour la technique d'ajustement de Fourier . 32
B.4.3 Calcul de l’ondulation de la fibre . 32

Annexe C (informative) Détermination du modèle circulaire d'ondulation de fibre . 33
C.1 Détermination des équations pour la microscopie latérale . 33
C.2 Détermination des équations pour la méthode de diffusion laser . 34

Figure A.1 – Schéma d'appareillage pour mesurer l'ondulation de la fibre à l'aide d'un
microscope optique . 27
Figure A.2 – Schéma d'appareillage pour mesurer l'ondulation de la fibre à l'aide d'un
micromètre laser . 28
Figure A.3 – Schéma d'appareillage pour mesurer l'ondulation de la fibre en fixant

l'échantillon dans une férule . 28
Figure B.1 – Schéma de mesure de l'ondulation optique par diffusion de rayons laser . 32
Figure C.1 – Disposition géométrique de la mesure de l’ondulation de fibre par
microscopie latérale . 33
Figure C.2 – Disposition géométrique de la mesure de l’ondulation de fibre par
diffusion laser . 34

– 22 – IEC 60793-1-34:2021  IEC 2021

COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
FIBRES OPTIQUES –
Partie 1-34: Méthodes de mesure et procédures d’essai –
Ondulation de la fibre
AVANT-PROPOS
1) La Commission Electrotechnique Internationale (IEC) est une organisation mondiale de normalisation composée
de l'ensemble des comités électrotechniques nationaux (Comités nationaux de l'IEC). L’IEC a pour objet de
favoriser la coopération internationale pour toutes les questions de normalisation dans les domaines de
l'électricité et de l'électronique. À cet effet, l’IEC – entre autres activités – publie des Normes internationales,
des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au public (PAS) et des
Guides (ci-après dénommés "Publication(s) de l’IEC"). Leur élaboration est confiée à des comités d'études, aux
travaux desquels tout Comité national intéressé par le sujet traité peut participer. Les organisations
internationales, gouvernementales et non gouvernementales, en liaison avec l’IEC, participent également aux
travaux. L’IEC collabore étroitement avec l'Organisation Internationale de Normalisation (ISO), selon des
conditions fixées par accord entre les deux organisations.
2) Les décisions ou accords officiels de l'IEC concernant les questions techniques représentent, dans la mesure du
possible, un accord international sur les sujets étudiés, étant donné que les Comités nationaux de l'IEC intéressés
sont représentés dans chaque comité d’études.
3) Les Publications de l'IEC se présentent sous la forme de recommandations internationales et sont agréées
comme telles par les Comités nationaux de l'IEC. Tous les efforts raisonnables sont entrepris afin que l'IEC
s'assure de l'exactitude du contenu technique de ses publications; l'IEC ne peut pas être tenue responsable de
l'éventuelle mauvaise utilisation ou interprétation qui en est faite par un quelconque utilisateur final.
4) Dans le but d'encourager l'uniformité internationale, les Comités nationaux de l'IEC s'engagent, dans toute la
mesure possible, à appliquer de façon transparente les Publications de l'IEC dans leurs publications nationales
et régionales. Toutes divergences entre toutes Publications de l'IEC et toutes publications nationales ou
régionales correspondantes doivent être indiquées en termes clairs dans ces dernières.
5) L'IEC elle-même ne fournit aucune attestation de conformité. Des organismes de ce
...