SIST EN IEC 60793-1-49:2019

Optical fibres - Part 1-49: Measurement methods and test procedures - Differential mode delay (IEC 60793-1-49:2018)

This part of IEC 60793 applies only to multimode, graded-index glass-core (category A1)
fibres. The test method is commonly used in production and research facilities, but is not
easily accomplished in the field.
This document describes a method for characterizing the modal structure of a graded-index
multimode fibre. This information is useful for assessing the bandwidth performance of a fibre
especially when the fibre is intended to support a range of launch conditions, for example,
those produced by standardized laser transmitters.
With this method, the output from a probe fibre that is single-moded at the test wavelength
excites the multimode fibre under test. The probe spot is scanned across the end-face of the
fibre under test at specified radial positions, and a set of response pulses are acquired at
these positions.
Three specifiable parameters can be derived from the collected set of data.
• The first parameter, differential modal delay (DMD), is the difference in optical pulse delay
time between the fastest and slowest mode groups of the fibre under test. DMD
specifications place limits on modal delay over a specified range of probe fibre radial
offset positions. DMD specifications are determined by modeling and experimentation to
correspond to a minimum effective modal bandwidth (EMB) for the expected range of
transmitters used in a link at a given performance level.
• The second specifiable parameter is derived by combining the pulses using sets of
specific radial weights to determine an approximation of a set of pulses from typical
transmitters. Using Fourier transforms, the calculated effective modal bandwidth (EMBc) is
determined for each weight set. The minimum of these EMBc values (minEMBc) is the
specifiable parameter.
• The third specifiable parameter, the computed overfilled launch bandwidth, OMBc, is
determined in a manner similar to EMBc, but by applying just one weight set to the set of
pulses; this weight set corresponds to the overfilling condition, where all mode groups are
equally excited.
The test's intent is to quantify the effects of interactions of the fibre modal structure and the
source modal characteristics excluding the source's spectral interaction with fibre chromatic
dispersion. Adding the effects of fibre chromatic dispersion and the source spectral
characteristics will reduce the overall transmission bandwidth, but this is a separate
calculation in most transmission models. In this test, the contribution of chromatic dispersion
is controlled by limiting the spectral width of usable test sources. Practical test sources will
have non-zero spectral width and will thus slightly distort the DMD, minEMBc and OMBc
values. These chromatic dispersion effects are considered in Annex A.
NOTE Comparison between IEC 60793-1-49 and ITU recommendations: ITU-T Recommendation G.650.1 [2]
contains no information on how to measure the DMD of a graded-index multimode fibre.

Lichtwellenleiter - Teil 1-49: Messmethoden und Prüfverfahren - Gruppenlaufzeitdifferenz (IEC 60793-1-49:2018)

Fibres optiques - Partie 1-49: Méthodes de mesure et procédures d'essai - Retard différentiel de mode (IEC 60793-1-49:2018)

IEC 60793-1-49:2018 s'applique uniquement aux fibres multimodales à cœur en verre à gradient d'indice (catégorie A1). Cette méthode d'essai, qui est généralement utilisée dans les installations de production et de recherche, n'est pas facilement réalisée sur le terrain. Le présent document décrit une méthode de caractérisation de la structure modale d'une fibre multimodale à gradient d'indice. Cette information est utile pour évaluer les performances de largeur de bande d'une fibre, en particulier lorsque la fibre est destinée à supporter une plage de conditions d'injection, par exemple celles produites par les émetteurs lasers normalisés. Cette troisième édition annule et remplace la deuxième édition parue en 2006 dont elle constitue une révision technique.  La présente édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) un meilleur alignement sur l'objectif initial en remédiant à certaines omissions pour améliorer la rigueur des mesures;
b) la mesure des fibres avec un plus petit retard différentiel de mode (et une plus grande largeur de bande modale) telles que des fibres de type A1a.3 de l'IEC 60793-2-10 utilisées pour construire des câbles de catégorie de performance OM4, de nouvelles exigences sur la spécification de l'amplitude du détecteur et de la réponse temporelle, les conditions de déploiement des spécimens, le balayage des quatre quadrants et l'uniformité des emplacements radiaux pour calculer la largeur de bande.
Mots clés: structure modale d'une fibre multimodale à gradient d'indice, performances de largeur de bande

Optična vlakna - 1-49. del: Merilne metode in postopki preskušanja - Diferenčna zakasnitev rodov (IEC 60793-1-49:2018)

Ta del standarda IEC 60793 se uporablja samo za večrodna gradientna steklena vlakna (kategorija A1). Preskusna metoda se običajno uporablja v proizvodnji in raziskovalnih ustanovah, na terenu pa ni lahko izvedljiva.
Ta dokument opisuje metodo za opredelitev rodovne strukture gradientnih večrodnih vlaken. Te informacije so uporabne pri ocenjevanju prenosne zmogljivosti vlaken, še posebej, ko so vlakna namenjena podpori različnim zagonskim pogojem, na primer tistim, ki jih proizvedejo standardizirani laserski oddajniki.
S to metodo izhod enorodnega vlakna na sondi pri preskusni valovni dolžini presega preskušano večrodno vlakno. Točka sonde se skenira na končnem delu preskušanega optičnega vlakna v določenih radialnih položajih, na teh položajih pa se pridobi niz odzivnih impulzov.
Iz zbranega nabora podatkov je mogoče izpeljati tri določljive parametre.
• Prvi parameter, diferenčna zakasnitev rodov (DMD), je razlika v času zakasnitve optičnega impulza med najhitrejšimi in najpočasnejšimi skupinami rodov pri preskušanem vlaknu. Specifikacije diferenčne zakasnitve rodov omejujejo zakasnitev rodov v določenem območju radialno izravnanih položajev vlaken v sondi. Specifikacije diferenčne zakasnitve rodov se določijo z modeliranjem in eksperimentiranjem, da ustrezajo minimalni učinkoviti pasovni širini rodov (EMB) za pričakovan obseg oddajnikov, uporabljenih v povezavi na določeni ravni zmogljivosti.
• Drugi določljiv parameter je izpeljan z združevanjem impulzov s pomočjo niza določenih radialnih bremen, da se določi približek niza impulzov pri tipičnih oddajnikih. S Fourierovimi transformacijami se izračuna učinkovita pasovna širina rodov (EMBc) za vsak niz bremena. Najnižja vrednost teh vrednosti EMBc (minEMBc) je določljiv parameter.
• Tretji določljiv parameter, izračunana pasovna širina prepolnega zagona (OMBc), se določi na način, podoben vrednosti EMBc, vendar z uporabo samo enega niza bremena pri nizu impulzov; ta niz bremena ustreza pogoju prenapolnjenosti, kjer so vse skupine rodov enako vzbujene.
Namen preskusa je kvantifikacija učinkov interakcij rodovne strukture vlaken in izvornih rodovnih značilnosti, razen spektralne interakcije vira z barvno razpršenostjo vlaken. Dodajanje učinkov barvne razpršenosti vlaken in spektralnih značilnosti vira bo zmanjšalo skupno pasovno širino prenosa, vendar je to v večini modelov prenosa ločen izračun. Pri tem preskusu se prispevek barvne razpršenosti nadzoruje z omejevanjem spektralne širine uporabnih preskusnih virov. Praktični preskusni viri bodo imeli neničelno spektralno širino in bodo tako nekoliko izkrivili vrednosti DMD, minEMBc in OMBc. Ti učinki barvne razpršenosti so obravnavani v dodatku A.
OPOMBA: Primerjava med standardom IEC 60793-1-49 in priporočili ITU: Priporočilo ITU-T G.650.1 [2] ne vsebuje nobenih informacij o tem, kako izmeriti DMD gradientnega večrodnega vlakna.

General Information

• Status: Published
• Publication Date: 25-Nov-2018
• ICS: 33.180.10 - Fibres and cables
• Technical Committee: MOC - Mobile Communications
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 09-Nov-2018
• Due Date: 14-Jan-2019
• Completion Date: 26-Nov-2018
• Ref Project: EN IEC 60793-1-49:2018 - Optical fibres - Part 1-49: Measurement methods and test procedures - Differential mode delay

Relations

• Replaces: SIST EN 60793-1-49:2007 - Optical fibres -- Part 1-49: Measurement methods and test procedures - Differential mode delay
• Effective Date: 06-Nov-2018

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN IEC 60793-1-49:2019
01-januar-2019
1DGRPHãþD
SIST EN 60793-1-49:2007
2SWLþQDYODNQDGHO0HULOQHPHWRGHLQSRVWRSNLSUHVNXãDQMD'LIHUHQþQD
]DNDVQLWHYURGRY,(&
Optical fibres - Part 1-49: Measurement methods and test procedures - Differential mode
delay (IEC 60793-1-49:2018)
Lichtwellenleiter - Teil 1-49: Messmethoden und Prüfverfahren - Gruppenlaufzeitdifferenz
(IEC 60793-1-49:2018)
Fibres optiques - Partie 1-49: Méthodes de mesure et procédures d'essai - Retard
différentiel de mode (IEC 60793-1-49:2018)
Ta slovenski standard je istoveten z: EN IEC 60793-1-49:2018
ICS:
33.180.10 2SWLþQDYODNQDLQNDEOL Fibres and cables
SIST EN IEC 60793-1-49:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 60793-1-49:2019

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SIST EN IEC 60793-1-49:2019


EUROPEAN STANDARD EN IEC 60793-1-49

NORME EUROPÉENNE

EUROPÄISCHE NORM
November 2018
ICS 33.180.10 Supersedes EN 60793-1-49:2006
English Version
Optical fibres - Part 1-49: Measurement methods and test
procedures - Differential mode delay
(IEC 60793-1-49:2018)
Fibres optiques - Partie 1-49: Méthodes de mesure et Lichtwellenleiter - Teil 1-49: Messmethoden und
procédures d'essai - Retard différentiel de mode Prüfverfahren - Gruppenlaufzeitdifferenz
(IEC 60793-1-49:2018) (IEC 60793-1-49:2018)
This European Standard was approved by CENELEC on 2018-09-19. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.


European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN IEC 60793-1-49:2018 E

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SIST EN IEC 60793-1-49:2019
EN IEC 60793-1-49:2018 (E)
European foreword
The text of document 86A/1812/CDV, future edition 3 of IEC 60793-1-49, 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 60793-1-49:2018.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2019-06-19
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2021-09-19
document have to be withdrawn

This document supersedes EN 60793-1-49:2006.
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 60793-1-49:2018 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 60793-2-10 NOTE Harmonized as EN 60793-2-10
IEC 60793-1-42 NOTE Harmonized as EN 60793-1-42


2

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SIST EN IEC 60793-1-49:2019
EN IEC 60793-1-49:2018 (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 2017 Optical fibres - Part 1-1: Measurement methods EN 60793-1-1 2017
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 60793-1-41 -  Optical fibres - Part 1-41: Measurement methods - -
and test procedures - Bandwidth
IEC 60793-1-45 -  Optical fibres - Part 1-45: Measurement methods EN IEC 60793-1-45 -
and test procedures - Mode field diameter
IEC 60825-1 -  Safety of laser products - Part 1: Equipment EN 60825-1 -
classification and requirements
IEC 60825-2 -  Safety of laser products - Part 2: Safety of optical EN 60825-2 -
fibre communication systems (OFCS)
IEC 61280-1-4 -  Fibre optic communication subsystem test EN 61280-1-4 -
procedures - Part 1-4: General communication
subsystems - Light source encircled flux
measurement method

3

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SIST EN IEC 60793-1-49:2019



IEC 60793-1-49

®


Edition 3.0 2018-08




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE











Optical fibres –

Part 1-49: Measurement methods and test procedures – Differential mode delay




Fibres optiques –

Partie 1-49: Méthodes de mesure et procédures d'essai – Retard différentiel de

mode















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 33.180.10 ISBN 978-2-8322-5954-2




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 60793-1-49:2019
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CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Apparatus . 8
4.1 Overview. 8
4.2 Optical source . 9
4.3 Probe fibre . 10
4.4 Scanning stage . 10
4.5 Probe to test sample coupling . 10
4.6 Cladding mode stripper . 10
4.7 Detection system . 10
4.8 Sampler and digitizer . 11
4.9 Computational equipment . 11
4.10 System performance . 11
4.10.1 General . 11
4.10.2 Pulse temporal stability . 12
4.10.3 System stability frequency limit (SSFL) . 12
5 Sampling and specimens . 13
5.1 Test sample . 13
5.2 Specimen end-faces . 13
5.3 Specimen length . 13
5.4 Specimen deployment . 13
5.5 Specimen positioning . 13
6 Procedure . 13
6.1 Fibre coupling and system setup . 13
6.2 Determination of centre . 14
6.3 Measurement of the test sample . 14
6.3.1 Selection of radii and quadrant . 14
6.3.2 Collection of scan data . 14
6.4 Determination of ∆T and ∆T . 14
PULSE REF
6.5 Reference test method . 14
7 Calculations and interpretation of results . 15
7.1 General . 15
7.2 Differential mode delay (DMD) . 15
7.2.1 General . 15
7.2.2 Deconvolution . 15
7.2.3 Pulse folding . 15
7.2.4 Determination of DMD . 16
7.3 Minimum calculated effective modal bandwidth . 17
7.3.1 General . 17
7.3.2 Time domain pulse computation . 17
7.3.3 Calculate the transfer function . 18
7.3.4 Compute the power spectrum . 18
7.3.5 Compute EMB and minEMB . 18
c c
7.4 Length normalization . 18

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SIST EN IEC 60793-1-49:2019
IEC 60793-1-49:2018 © IEC 2018 – 3 –
8 Documentation . 18
8.1 Information to be reported . 18
8.2 Information available upon request . 19
9 Specification information . 19
Annex A (normative) Source spectral width limitation . 20
A.1 Limiting the effect of chromatic dispersion (CD) on the value of DMD . 20
A.1.1 General . 20
A.1.2 Limit CD contribution to DMD to be measured . 20
A.1.3 Limit CD contribution to reference width . 20
A.1.4 Adjust ∆T to account for CD contribution . 21
REF
A.1.5 High-performance DMD fibres and spectral requirements . 21
A.2 Chromatic dispersion in multimode fibres . 22
Annex B (informative) Determination of fibre optical centre . 23
B.1 General . 23
B.2 Method . 23
Annex C (normative) Detection system modal measurement . 26
C.1 General . 26
C.2 Determination of coupling function . 26
C.2.1 Overview . 26
C.2.2 Fibre sample and coupling . 26
C.2.3 Detector response . 26
C.2.4 Reference response . 27
C.2.5 Coupling function determination . 28
Annex D (informative) Discussion of measurement details . 29
D.1 DMD . 29
D.2 EMB calculation . 30
c
Annex E (informative) Determining DMD weights for EMB calculation . 33
c
E.1 Selecting a set of weightings . 33
E.2 Procedure for generating DMD weightings given encircled flux data . 33
Annex F (informative) EMB calculation information . 35
c
F.1 Default DMD weightings for transmitters conforming to IEC 60793-2-10 . 35
F.2 Example method to determine if an adjusted bandwidth (BW) metric is
adequate. 36
Bibliography . 38
Figure 1 – Example apparatus . 9
Figure B.1 – Typical area data from centring waveforms . 24
Figure D.1 – Idealized DMD data . 29
Table A.1 – Worst-case chromatic dispersion. 22
Table C.1 – Theoretical normalized coupling efficiency . 27
Table F.1 – DMD weightings . 35
Table F.2 – DMD weightings . 36

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

OPTICAL FIBRES –

Part 1-49: Measurement methods and test procedures –
Differential mode delay

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 60793-1-49 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) better alignment with original intent by filling some omissions and therefore improving
measurement rigor;

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SIST EN IEC 60793-1-49:2019
IEC 60793-1-49:2018 © IEC 2018 – 5 –
b) the measurement of fibres with smaller differential mode delay (and higher modal
1
bandwidth) such as type A1a.3 fibres of IEC 60793-2-10 [1] that are used in constructing
OM4 performance category cables; new requirements on specifying detector amplitude
and temporal response, specimen deployment conditions, four-quadrant scanning, and
uniformity of radial locations for calculating bandwidth.
The text of this International Standard is based on the following documents:
CDV Report on voting
86A/1812/CDV 86A/1860/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.
This International Standard is to be used in conjunction with IEC 60793-1-1:2017.
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.

___________
1
Numbers in square brackets refer to the Bibliography.

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OPTICAL FIBRES –

Part 1-49: Measurement methods and test procedures –
Differential mode delay


1 Scope
This part of IEC 60793 applies only to multimode, graded-index glass-core (category A1)
fibres. The test method is commonly used in production and research facilities, but is not
easily accomplished in the field.
This document describes a method for characterizing the modal structure of a graded-index
multimode fibre. This information is useful for assessing the bandwidth performance of a fibre
especially when the fibre is intended to support a range of launch conditions, for example,
those produced by standardized laser transmitters.
With this method, the output from a probe fibre that is single-moded at the test wavelength
excites the multimode fibre under test. The probe spot is scanned across the end-face of the
fibre under test at specified radial positions, and a set of response pulses are acquired at
these positions.
Three specifiable parameters can be derived from the collected set of data.
• The first parameter, differential modal delay (DMD), is the difference in optical pulse delay
time between the fastest and slowest mode groups of the fibre under test. DMD
specifications place limits on modal delay over a specified range of probe fibre radial
offset positions. DMD specifications are determined by modeling and experimentation to
correspond to a minimum effective modal bandwidth (EMB) for the expected range of
transmitters used in a link at a given performance level.
• The second specifiable parameter is derived by combining the pulses using sets of
specific radial weights to determine an approximation of a set of pulses from typical
transmitters. Using Fourier transforms, the calculated effective modal bandwidth (EMB ) is
c
values (minEMB ) is the
determined for each weight set. The minimum of these EMB
c c
specifiable parameter.
• The third specifiable parameter, the computed overfilled launch bandwidth, OMB , is
c
determined in a manner similar to EMB , but by applying just one weight set to the set of
c
pulses; this weight set corresponds to the overfilling condition, where all mode groups are
equally excited.
The test's intent is to quantify the effects of interactions of the fibre modal structure and the
source modal characteristics excluding the source's spectral interaction with fibre chromatic
dispersion. Adding the effects of fibre chromatic dispersion and the source spectral
characteristics will reduce the overall transmission bandwidth, but this is a separate
calculation in most transmission models. In this test, the contribution of chromatic dispersion
is controlled by limiting the spectral width of usable test sources. Practical test sources will
have non-zero spectral width and will thus slightly distort the DMD, minEMB and OMB
c c
values. These chromatic dispersion effects are considered in Annex A.
NOTE Comparison between IEC 60793-1-49 and ITU recommendations: ITU-T Recommendation G.650.1 [2]
contains no information on how to measure the DMD of a graded-index multimode fibre.
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

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SIST EN IEC 60793-1-49:2019
IEC 60793-1-49:2018 © IEC 2018 – 7 –
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60793-1-1:2017, 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 60793-1-41, Optical fibres – Part 1-41: Measurement methods and test procedures –
Bandwidth
IEC 60793-1-45, Optical fibres – Part 1-45: Measurement methods and test procedures –
Mode field diameter
IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements
IEC 60825-2, Safety of laser products – Part 2: Safety of optical fibre communication systems
(OFCS)
IEC 61280-1-4, Fibre optic communication subsystem test procedures – Part 1-4: General
communication subsystems – Light source encircled flux measurement method
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
maximum DMD
maximum DMD occurring between the outer (R ) and inner (R ) limits of radial offset
OUTER INNER
position over which the probe spot is scanned for one or more sets of R and R
OUTER INNER
3.2
minimum EMB
c
minEMB
c
minimum EMB among the EMB values calculated from a sequence of DMD weightings
c c
Note 1 to entry: The user of this document may also specify the calculated overfilled modal bandwidth (OMB ).
c
3.3
differential mode delay
DMD
estimated difference in optical pulse delay time between the fastest and slowest modes
excited for all radial offset positions between and including R and R
INNER OUTER
Note 1 to entry: This note applies to the French language only.

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SIST EN IEC 60793-1-49:2019
– 8 – IEC 60793-1-49:2018 © IEC 2018
3.4
effective modal bandwidth
EMB
bandwidth associated with the transfer function, H(f), of a particular laser/fibre combination
Note 1 to entry: This note applies to the French language only.
3.5
calculated overfilled modal bandwidth
OMB
c
bandwidth associated with the transfer function, H(f), when the fibre is overfilled
3.6
quadrant
radial section at one of four possible azimuthal angles over which a radial set of pulse data
can be collected
Note 1 to entry: For example, a radial section may be taken from one of the sets x-positive, x-negative, y-positive
or y-negative.
3.7
mode field diameter
MFD
diameter of the mode emanating from the end-face of a single-mode fibre, as determined by
IEC 60793-1-45
Note 1 to entry: This note applies to the French language only.
3.8
reference test method
RTM
test method in which a given characteristic of a specified class of optical fibres or optical
cables (and associat
...