Optical fibres - Part 1-40: Attenuation measurement methods

This part of IEC 60793 establishes uniform requirements for measuring the attenuation of optical fibre, thereby assisting in the inspection of fibres and cables for commercial purposes. Four methods are described for measuring attenuation, one being that for modelling spectral attenuation: - method A: cut-back; - method B: insertion loss; - method C: backscattering; - method D: modelling spectral attenuation. Methods A to C apply to the measurement of attenuation for all categories of the following fibres: - class A multimode fibres; - class B single-mode fibres. Method C, backscattering, also covers the location, losses and characterization of point discontinuities. Method D is applicable only to class B fibres. Information common to all four methods appears in Clauses 1 to 11, and information pertaining to each individual method appears in Annexes A, B, C, and D, respectively.

Lichtwellenleiter - Teil 1-40: Dämpfungsmessverfahren

Fibres optiques - Partie 1-40: Méthodes de mesurage d'affaiblissement

IEC 60793-1-40:2019 est disponible sous forme de IEC 60793-1-40:2019 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.IEC 60793-1-40:2019 établit des exigences uniformes pour mesurer l'affaiblissement d'une fibre optique, contribuant ainsi au contrôle des fibres et des câbles dans les relations commerciales. Quatre méthodes sont décrites pour mesurer l'affaiblissement, parmi lesquelles une méthode pour modéliser l'affaiblissement spectral: – méthode A: fibre coupée; – méthode B: pertes d'insertion; – méthode C: rétrodiffusion; – méthode D: modélisation de l'affaiblissement spectral. Les méthodes A à C s'appliquent au mesurage de l'affaiblissement pour toutes les catégories de fibres suivantes: – fibres multimodales de classe A; – fibres unimodales de classe B. La méthode C, rétrodiffusion, s'applique aussi à la localisation, aux pertes et à la caractérisation des discontinuités ponctuelles. La méthode D s'applique uniquement aux fibres de classe B. Les informations communes à ces quatre méthodes sont présentées dans les Articles 1 à 11, et les informations propres à chaque méthode individuelle, sont présentées dans les Annexes A, B, C et D, respectivement. Cette deuxième édition annule et remplace la première édition parue en 2001 dont elle constitue une révision technique. La présente édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: a) Amélioration de la description des détails de mesurage pour les fibres B6; b) Amélioration des exigences d'étalonnage pour les fibres A4; c) Ajout de l'Annexe E qui décrit des exemples de résultats d'essai sur des câbles courts pour des fibres multimodales A1. Mots-clés: mesurer l'affaiblissement d'une fibre optique

Optična vlakna - 1-40. del: Metode merjenja slabljenja (IEC 60793-1-40:2019)

1.1 Opredelitev izdelka
Ta evropski standard vsebuje začetne, začetne dimenzijske, optične, mehanske in okoljske zahteve (razen električnih zahtev) za sprejemnik/oddajnik tipa 4+4x10.3125 Gb/s MPO (QFSP) s konektorjem MPO, ki je opremljen z 12 vlakenskimi tulkami PPS, zaključenimi na vlaknu kategorije A1a.3a ali A1a.3b po standardu EN 60793 2 10, da se uvrsti v kategorijo standardnega izdelka EN.
Ker so dovoljene različne izvedbe, so podrobnosti o označevanju izdelkov podane v točki 4.6.
1.2 Združljivost
Vsi izdelki, ki so v skladu z zahtevami tega standarda, so namenjeni medsebojnemu povezovanju in zagotavljajo določeno raven naključno združene in prejete učinkovitosti. Namen tega je, da bo tako ne glede na vire proizvodnje izdelka.
1.3 Delovno okolje
Izbrani preskusi v kombinaciji z resnostjo in trajanjem so reprezentativni za notranjo uporabo osnovne plošče/hrbtne plošče, ki izhaja iz zaščitenega okolja v prostorih kupca, kot je določeno v skupini standardov EN 50173 in ISO/IEC 11801 in kot je določeno v kategoriji C po standardu EN 61753 1, ki se običajno opisuje kot okolje podatkovnega centra.
1.4 Zanesljivost
Medtem ko znaša pričakovana tehnična življenjska doba izdelka v tem okolju 10 let, skladnost s tem standardom ne zagotavlja zanesljivosti izdelka. To naj bi napovedali v okviru priznanega programa za oceno zanesljivosti.
1.5 Zagotavljanje kakovosti
Skladnost s tem standardom ne zagotavlja doslednosti izdelave izdelka. To naj bi vzdrževali v okviru priznanega programa za zagotavljanje kakovosti.

General Information

Status
Published
Publication Date
09-May-2019
Current Stage
6060 - Document made available
Due Date
02-Sep-2019

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SLOVENSKI STANDARD
SIST EN IEC 60793-1-40:2019
01-julij-2019
Nadomešča:
SIST EN 60793-1-40:2004
Optična vlakna - 1-40. del: Metode merjenja slabljenja (IEC 60793-1-40:2019)

Optical fibres - Part 1-40: Attenuation measurement methods (IEC 60793-1-40:2019)

Lichtwellenleiter - Teil 1-40: Messmethoden und Prüfverfahren - Dämpfung (IEC 60793-1

-40:2019)
Fibres optiques - Partie 1-40: Méthodes de mesure et procédures d'essai -
Affaiblissement (IEC 60793-1-40:2019)
Ta slovenski standard je istoveten z: EN IEC 60793-1-40:2019
ICS:
33.180.10 (Optična) vlakna in kabli Fibres and cables
SIST EN IEC 60793-1-40:2019 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 60793-1-40:2019
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SIST EN IEC 60793-1-40:2019
EUROPEAN STANDARD EN IEC 60793-1-40
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2019
ICS 33.180.10 Supersedes EN 60793-1-40:2003
English Version
Optical fibres - Part 1-40: Attenuation measurement methods
(IEC 60793-1-40:2019)

Fibres optiques - Partie 1-40: Méthodes de mesurage Lichtwellenleiter - Teil 1-40: Messmethoden und

d'affaiblissement Prüfverfahren - Dämpfung
(IEC 60793-1-40:2019) (IEC 60793-1-40:2019)

This European Standard was approved by CENELEC on 2019-05-01. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,

Switzerland, Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 60793-1-40:2019 E
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SIST EN IEC 60793-1-40:2019
EN IEC 60793-1-40:2019 (E)
European foreword

The text of document 86A/1909/FDIS, future edition 2 of IEC 60793-1-40, prepared by SC 86A "Fibres

and cables" of IEC/TC 86 "Fibre optics" was submitted to the IEC-CENELEC parallel vote and

approved by CENELEC as EN IEC 60793-1-40:2019.
The following dates are fixed:

• latest date by which the document has to be implemented at national (dop) 2020-02-01

level by publication of an identical national standard or by endorsement

• latest date by which the national standards conflicting with the (dow) 2022-05-01

document have to be withdrawn
This document supersedes EN 60793-1-40:2003.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice

The text of the International Standard IEC 60793-1-40:2019 was approved by CENELEC as a

European Standard without any modification.
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SIST EN IEC 60793-1-40:2019
EN IEC 60793-1-40:2019 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments)

applies.

NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60793-1-1 - Optical fibres - Part 1-1: Measurement methods EN 60793-1-1 -
and test procedures - General and guidance

IEC 60793-1-22 - Optical fibres - Part 1-22: Measurement methods EN 60793-1-22 -

and test procedures - Length measurement

IEC 60793-1-43 - Optical fibres - Part 1-43: Measurement methods EN 60793-1-43 -

and test procedures - Numerical aperture
measurement
IEC 61746-1 - Calibration of optical time-domain reflectometers EN 61746-1 -
(OTDR) - Part 1: OTDR for single mode fibres
IEC 61746-2 - Calibration of optical time-domain reflectometers EN 61746-2 -
(OTDR) - Part 2: OTDR for multimode fibres
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SIST EN IEC 60793-1-40:2019
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SIST EN IEC 60793-1-40:2019
IEC 60793-1-40
Edition 2.0 2019-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical fibres –
Part 1-40: Attenuation measurement methods
Fibres optiques –
Partie 1-40: Méthodes de mesurage de l'affaiblissement
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.10 ISBN 978-2-8322-6593-2

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN IEC 60793-1-40:2019
– 2 – IEC 60793-1-40:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 5

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 8

4 Calibration requirements .................................................................................................. 9

5 Reference test method .................................................................................................... 9

6 Apparatus ........................................................................................................................ 9

7 Sampling and specimens ................................................................................................. 9

7.1 Specimen length ..................................................................................................... 9

7.2 Specimen end face ................................................................................................. 9

8 Procedure ........................................................................................................................ 9

9 Calculations ..................................................................................................................... 9

9.1 Methods A and B .................................................................................................... 9

9.2 Method C ................................................................................................................ 9

9.3 Method D ................................................................................................................ 9

10 Results ............................................................................................................................ 9

10.1 Information available with each measurement ......................................................... 9

10.2 Information available upon request ....................................................................... 10

10.3 Method-specific additional information .................................................................. 10

11 Specification information ............................................................................................... 10

Annex A (normative) Requirements specific to method A – Cut-back ................................... 11

A.1 General ................................................................................................................. 11

A.2 Apparatus ............................................................................................................. 11

A.2.1 General apparatus for all fibres...................................................................... 11

A.2.2 Launch apparatus for all single-mode fibres ................................................... 13

A.2.3 Launch apparatus for A1 multimode fibres ..................................................... 14

A.2.4 Launch apparatus for A2 to A4 multimode fibres ............................................ 16

A.2.5 Calibration requirements ................................................................................ 17

A.3 Procedure ............................................................................................................. 18

A.4 Calculations .......................................................................................................... 18

Annex B (normative) Requirements specific to method B – Insertion loss ............................. 19

B.1 General ................................................................................................................. 19

B.2 Apparatus ............................................................................................................. 19

B.2.1 General set-ups ............................................................................................. 19

B.2.2 Apparatus common to method A (cut-back).................................................... 19

B.2.3 Additional apparatus specific to method B (insertion-loss) ............................. 19

B.2.4 Calibration requirements ................................................................................ 19

B.3 Procedure ............................................................................................................. 19

B.4 Calculations .......................................................................................................... 20

Annex C (normative) Requirements specific to method C – Backscattering .......................... 21

C.1 General ................................................................................................................. 21

C.2 Apparatus ............................................................................................................. 21

C.2.1 General ......................................................................................................... 21

C.2.2 Optical transmitter ......................................................................................... 22

C.2.3 Launch conditions .......................................................................................... 22

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IEC 60793-1-40:2019 © IEC 2019 – 3 –

C.2.4 Optical splitter ............................................................................................... 22

C.2.5 Optical receiver ............................................................................................. 22

C.2.6 Pulse duration and repetition rate .................................................................. 22

C.2.7 Signal processor ............................................................................................ 22

C.2.8 Display .......................................................................................................... 23

C.2.9 Data interface (optional) ................................................................................ 23

C.2.10 Reflection controller (optional) ....................................................................... 23

C.2.11 Splices and connectors .................................................................................. 23

C.3 Sampling and specimens ...................................................................................... 23

C.4 Procedure ............................................................................................................. 23

C.4.1 General ......................................................................................................... 23

C.4.2 Further steps for measuring attenuation......................................................... 25

C.4.3 Further steps for measuring point discontinuities ........................................... 25

C.4.4 Calibration ..................................................................................................... 27

C.5 Calculations .......................................................................................................... 27

C.6 Results ................................................................................................................. 27

Annex D (normative) Requirements specific to method D – Spectral attenuation

modelling .............................................................................................................................. 28

D.1 General ................................................................................................................. 28

D.2 Apparatus ............................................................................................................. 28

D.3 Sampling and specimens ...................................................................................... 28

D.4 Procedure ............................................................................................................. 28

D.5 Calculations .......................................................................................................... 29

D.6 Results ................................................................................................................. 29

Annex E (informative) Examples of short cable test results on A1 multimode fibres ............. 31

Bibliography .......................................................................................................................... 33

Figure A.1 – Arrangement of equipment for loss measurement at a specified

wavelength ........................................................................................................................... 11

Figure A.2 – Arrangement of equipment used to obtain loss spectrum .................................. 12

Figure A.3 – General launch arrangement ............................................................................. 12

Figure A.4 – Limited phase space launch optics .................................................................... 15

Figure A.5 – Two examples of optical fibre scramblers .......................................................... 16

Figure A.6 – Lens system ..................................................................................................... 16

Figure A.7 – Launch fibre ...................................................................................................... 17

Figure A.8 – Mode scrambler (for A.4 fibre) .......................................................................... 17

Figure A.9 – A wide-spectrum source (line "b") could lead to attenuation measurement

errors due to sharp variations on spectral attenuation of polymer-core fibres (line "a") .......... 18

Figure B.1 – Calibration of insertion loss measurement set ................................................... 20

Figure B.2 – Measurement of insertion loss .......................................................................... 20

Figure C.1 – Block diagram of an OTDR ............................................................................... 21

Figure C.2 – Schematic OTDR trace for a "uniform" specimen preceded by a dead-

zone fibre ............................................................................................................................. 24

Figure C.3 – Schematic OTDR trace for a "uniform" specimen not preceded by a dead-

zone fibre ............................................................................................................................. 24

Figure C.4 – Schematic OTDR trace showing apparent loss due to point discontinuities,

one reflective and one non-reflective .................................................................................... 26

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Figure C.5 – Schematic of an expanded OTDR trace showing two point discontinuities,

one with apparent gain, and another with no apparent loss or gain ....................................... 26

Figure E.1 – Example of attenuation coefficient tests on A1a.1 fibre ..................................... 31

Figure E.2 – Example of attenuation coefficient tests on A1a.3 fibre ..................................... 31

Figure E.3 – Example of attenuation coefficient tests on A1b fibre ........................................ 32

Table A.1 – Size examples ................................................................................................... 15

Table A.2 – Launch conditions for A2 to A4 fibres ................................................................. 16

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SIST EN IEC 60793-1-40:2019
IEC 60793-1-40:2019 © IEC 2019 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-40: Attenuation measurement methods
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 60793-1-40 has been prepared by subcommittee 86A: Fibres and

cables, of IEC technical committee 86: Fibre optics.

This second edition cancels and replaces the first edition published in 2001. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) Improvement of the description of measurement details for B6 fibre;
b) Improvement of the calibration requirements for A4 fibre;

c) Introduction of Annex E describing examples of short cable test results on A1 multimode

fibres.
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SIST EN IEC 60793-1-40:2019
– 6 – IEC 60793-1-40:2019 © IEC 2019
The text of this International Standard is based on the following documents:
FDIS Report on voting
86A/1909/FDIS 86A/1927/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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.
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SIST EN IEC 60793-1-40:2019
IEC 60793-1-40:2019 © IEC 2019 – 7 –
OPTICAL FIBRES –
Part 1-40: Attenuation measurement methods
1 Scope

This part of IEC 60793 establishes uniform requirements for measuring the attenuation of

optical fibre, thereby assisting in the inspection of fibres and cables for commercial purposes.

Four methods are described for measuring attenuation, one being that for modelling spectral

attenuation:
– method A: cut-back;
– method B: insertion loss;
– method C: backscattering;
– method D: modelling spectral attenuation.

Methods A to C apply to the measurement of attenuation for all categories of the following

fibres:
– class A multimode fibres;
– class B single-mode fibres.

Method C, backscattering, also covers the location, losses and characterization of point

discontinuities.
Method D is applicable only to class B fibres.

Information common to all four methods appears in Clauses 1 to 11, and information

pertaining to each individual method appears in Annexes A, B, C, and D, respectively.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.

IEC 60793-1-1, Optical fibres – Part 1-1: Measurement methods and test procedures –

General and guidance

IEC 60793-1-22, Optical fibres – Part 1-22: Measurement methods and test procedures –

Length measurement

IEC 60793-1-43, Optical fibres – Part 1-43: Measurement methods and test procedures –

Numerical aperture measurement

IEC 61746-1, Calibration of optical time-domain reflectometers (OTDR) – Part 1: OTDR for

single mode fibres

IEC 61746-2, Calibration of optical time-domain reflectometers (OTDR) – Part 2: OTDR for

multimode fibres
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SIST EN IEC 60793-1-40:2019
– 8 – IEC 60793-1-40:2019 © IEC 2019
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60793-1-1 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
attenuation

attenuation of a fibre at wavelength λ between two cross-sections, 1 and 2, separated by a

distance and defined as
P ()λ
A()λ = 10log
(1)
P ()λ
where
A(λ) is the attenuation, in dB, at wavelength λ;
P (λ) is the optical power traversing cross-section 1;
P (λ) is the optical power traversing cross-section 2.

Note 1 to entry: Attenuation is a measure of the decreasing optical power in a fibre at a given wavelength. It

depends on the nature and length of the fibre and is also affected by measurement conditions.

3.2
attenuation coefficient
attenuation per unit length for a uniform fibre under steady-state conditions

Note 1 to entry: It is possible to define the attenuation per unit length or the attenuation coefficient as follows:

A()λ
αλ()= (2)
which is independent of the chosen length of the fibre,
where
α(λ) is the attenuation coefficient;
A(λ) is the attenuation at wavelength λ;
L is the length, in kilometres.

Note 2 to entry: Uncontrolled launching conditions normally excite higher order lossy modes that produce

transient losses and result in attenuation that is not proportional to the length of the fibre. A controlled, steady-

state launching condition yields attenuation that is proportional to the fibre's length. Under steady-state conditions,

an attenuation coefficient of a fibre can be determined and the attenuation of concatenated fibres added linearly.

3.3
spectral attenuation modelling

technique that predicts the attenuation coefficients across a spectrum of wavelengths from a

small number (three to five) of discrete values measured directly at different wavelengths

3.4
point discontinuity

temporary or permanent local deviation of the continuous optical time-domain reflectometer

(OTDR) signal in the upward or downward direction
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IEC 60793-1-40:2019 © IEC 2019 – 9 –

Note 1 to entry: The nature of the deviation can vary with test conditions (e.g. pulse duration, wavelength, and

direction of the OTDR signal). Although a point discontinuity can have a length greater than the corresponding

displayed pulse duration (including transmitter and receiver effects), the length is usually about equal to the pulse

duration. For a correct interpretation, the guidelines in IEC 60793-1-22 should be followed for measuring length.

4 Calibration requirements
See Annexes A, B, and C for methods A, B, and C, respectively.
5 Reference test method

Method A, cut-back, is the reference test method (RTM), which shall be the one used to settle

disputes.
6 Apparatus

Annexes A, B, C, and D include layout drawings and other equipment requirements for each

of the methods, respectively.
7 Sampling and specimens
7.1 Specimen length

The specimen shall be a known length of fibre on a reel, or within a cable, as specified in the

detail specification.
7.2 Specimen end face

Prepare a flat end face, orthogonal to the fibre axis, at the input and output ends of each

specimen.
8 Procedure
See Annexes A, B, C and D for methods A, B, C and D, respectively.
9 Calculations
9.1 Methods A and B

Methods A and B, cut-back and insertion loss use Equations (1) and (2) respectively, which

appear in 3.1 and 3.2.
9.2 Method C
See Annex C.
9.3 Method D
See Annex D.
10 Results
10.1 Information available with each measurement
Report the following information with each measurement:
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