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

IEC 60793-1-34:2021 is available as IEC 60793-1-34:2021 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.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

IEC 60793-1-34:2021 est disponible sous forme de IEC 60793-1-34:2021 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.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
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
10-Feb-2021
Ref Project

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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
IEC 60793-1-34:2021-02(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
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

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 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

---------------------- Page: 4 ----------------------
IEC 60793-1-34:2021  IEC 2021 – 3 –

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

---------------------- Page: 5 ----------------------
– 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
---------------------- Page: 6 ----------------------
IEC 60793-1-34:2021  IEC 2021 – 5 –

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.
---------------------- Page: 7 ----------------------
– 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
---------------------- Page: 8 ----------------------
IEC 60793-1-34:2021  IEC 2021 – 7 –
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 .

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.

---------------------- Page: 9 ----------------------
– 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.

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.
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.
---------------------- Page: 10 ----------------------
IEC 60793-1-34:2021  IEC 2021 – 9 –
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
---------------------- Page: 11 ----------------------
– 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.

---------------------- Page: 12 ----------------------
IEC 60793-1-34:2021  IEC 2021 – 11 –
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

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):
DD−
max min
δ = (A.1)
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:
I = D × sinθ (A.2)
1 ∑ i i
i=1
---------------------- Page: 13 ----------------------
– 12 – IEC 60793-1-34:2021  IEC 2021
R = D × cosθ
(A.3)
1 ∑ ii
i=1
Compute δ as the magnitude of the first-order Fourier component:
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:
Z +δ
r = (A.5)
where
Z is the measurement distance.
---------------------- Page: 14 ----------------------
IEC 60793-1-34:2021  IEC 2021 – 13 –
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 po

...

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