SIST EN 60793-1-42:2014

Optical fibres - Part 1-42: Measurement methods and test procedures - Chromatic dispersion

This part of IEC 60793 establishes uniform requirements for measuring the chromatic dispersion of optical fibre, thereby assisting in the inspection of fibres and cables for commercial purposes. Chromatic dispersion varies with wavelength. Some methods and implementations measure the group delay as a function of wavelength and the chromatic dispersion and dispersion slope are deduced from the derivatives (with respect to wavelength) of this data. This differentiation is most often done after the data are fitted to a mathematical model. Other implementations can allow direct measurement (of the chromatic dispersion) at each of the required wavelengths. For some (sub-) categories of fibre, the chromatic dispersion attributes are specified with the parameters of a specific model. In these cases, the relevant recommendation or standard defines the model appropriate for the definition of the specified parameters. For other fibre (sub-) categories, the dispersion is specified to be within a given range for one or more specified wavelength intervals. In the latter case, either direct measurements may be made at the wavelength extremes or some fitting model may be used to either allow group delay measurement methods or implementations, or to allow storage of a reduced set of parameters that may be used to calculate the interpolated dispersion for particular wavelengths which may not have actual direct measurement values. Annex D gives a general description of chromatic dispersion fitting and outlines a number of fitting equations suitable for use with any of the measurement methods or fibre categories. This standard gives three methods for measuring chromatic dispersion: - method A: phase shift; - method B: spectral group delay in the time domain; - method C: differential phase shift. Methods A, B, and C apply to the measurement of chromatic dispersion of the following fibres from IEC 60793-2 over a specified wavelength range: - category A1 graded-index multimode fibres; - sub-category A4f, A4g and A4h multimode fibres; - category B1, B2, B4, B5 and sub-categories B6_a1 and B6_a2 single-mode fibres. The methods can be applied to laboratory, factory and field measurements of chromatic dispersion, and the wavelength range of the measurements can be tailored as required. Measurements are made at temperature as stated in Table 1 of IEC 60793-1-1:2008, Standard range of atmospheric conditions. The methods are suitable for fibre or cable lengths greater than 1 km. They may also be applied to shorter lengths, but accuracy and repeatability may be compromised. Information common to all methods is contained in Clauses 1 to 8, and information pertaining to each individual method appears in Annexes A, B and C, respectively.

Lichtwellenleiter - Teil 1-42: Messmethoden und Prüfverfahren - Chromatische Dispersion

Fibres optiques - Partie 1-42: Méthodes de mesure de la dispersion chromatique

La CEI 60793-1-42:2013 établit des exigences uniformes pour la mesure de la dispersion chromatique des fibres optiques, contribuant ainsi au contrôle des fibres et des câbles dans les relations commerciales. Cette troisième édition annule et remplace la deuxième édition parue en 2007, et constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:  - Ajout des fibres unimodales de catégorie B6;  - Suppression de la méthode d'essai D (interférométrie). Il convient que la présente norme soit lue conjointement avec la CEI 60793-1-1. Mots clés: dispersion chromatique des fibres optiques

Optična vlakna - 1-42. del: Metode merjenja in preskusni postopki - Kromatična disperzija

Ta del standarda IEC 60793 določa enotne zahteve za merjenje kromatične disperzije optičnih vlaken, pri čemer pomaga pri pregledu vlaken in kablov za komercialne namene. Kromatična disperzija se spreminja z valovno dolžino. Z nekaterimi metodami in izvedbami se meri skupinska zakasnitev glede na valovno dolžino, pri čemer se kromatična disperzija in strmina disperzije določita iz derivatov (ob upoštevanju valovne dolžine) teh podatkov. To razlikovanje se najpogosteje opravi po prilagoditvi podatkov matematičnemu modelu. Druge izvedbe lahko omogočijo neposredno merjenje (kromatične disperzije) pri vsaki zahtevani valovni dolžini. Pri nekaterih (pod)kategorijah vlaken se atributi kromatične disperzije določijo s parametri specifičnega modela. V teh primerih ustrezno priporočilo ali standard opredeli model, primeren za določitev opredeljenih parametrov. Pri drugih (pod)kategorijah vlaken se opredeli, da mora biti disperzija znotraj določenega razpona za enega ali več opredeljenih intervalov valovne dolžine. V zadnjem primeru se lahko opravijo neposredne meritve pri ekstremnih vrednostih valovne dolžine ali se uporabi nekakšen prilagoditveni model, da se omogočijo merilne metode ali izvedbe skupinske zakasnitve ali da se omogoči shramba omejenega sklopa parametrov, ki se lahko uporabijo za izračun interpolirane disperzije za posamezne valovne dolžine, ki morda nimajo dejanskih vrednosti neposrednega merjenja. Dodatek D vsebuje splošen opis prilagoditve kromatične disperzije in navaja več prilagoditvenih enačb, primernih za uporabo s katero koli merilno metodo ali kategorijo vlaken. Ta standard določa tri metode za merjenje kromatične disperzije: – metodo A: fazni zamik; – metodo B: spektralna skupinska zakasnitev v časovni domeni; – metodo C: diferencialni fazni zamik. Metode A, B in C se uporabljajo za merjenje kromatične disperzije naslednjih vlaken iz standarda IEC 60793-2 v določenem razponu valovne dolžine: – gradientnih večrodnih vlaken kategorije A1; – večrodnih vlaken podkategorij A4f, A4g in A4h; – enorodnih vlaken kategorij B1, B2, B4, B5 ter podkategorij B6_a1 in B6_a2. Metode se lahko uporabljajo za laboratorijske, tovarniške in terenske meritve kromatične disperzije, pri čemer je mogoče razpon valovne dolžine meritev po potrebi prilagoditi. Meritve se izvajajo pri temperaturi iz preglednice 1 iz standarda IEC 60793-1-1:2008, Standardni razpon atmosferskih pogojev. Metode so primerne za vlakna ali kable dolžine nad 1 km. Uporabljajo se lahko tudi za krajše dolžine, vendar lahko to vpliva na točnost in ponovljivost. Informacije, skupne vsem metodam, so navedene v točkah 1 do 8, pri čemer so informacije v zvezi z vsako posamezno metodo navedene v dodatkih A, B in C.

General Information

• Status: Published
• Publication Date: 05-Dec-2013
• ICS: 33.180.10 - Fibres and cables
• Technical Committee: MOC - Mobile Communications
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 03-Dec-2013
• Due Date: 07-Feb-2014
• Completion Date: 06-Dec-2013
• Ref Project: EN 60793-1-42:2013 - Optical fibres - Part 1-42: Measurement methods and test procedures - Chromatic dispersion

Relations

• Corrected By: SIST EN 60793-1-42:2014/AC:2014 - Optical fibres - Part 1-42: Measurement methods and test procedures - Chromatic dispersion
• Effective Date: 29-Jan-2023
• Replaces: SIST EN 60793-1-42:2007 - Optical fibres -- Part 1-42: Measurement methods and test procedures - Chromatic dispersion
• Effective Date: 29-Jan-2023
• Revised: SIST EN 60793-1-42:2007 - Optical fibres -- Part 1-42: Measurement methods and test procedures - Chromatic dispersion
• Effective Date: 06-May-2014
• Corrected By: SIST EN 60793-1-42:2014/AC:2014 - Optical fibres - Part 1-42: Measurement methods and test procedures - Chromatic dispersion
• Effective Date: 26-Nov-2013

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 60793-1-42:2014
01-januar-2014
2SWLþQDYODNQDGHO0HWRGHPHUMHQMDLQSUHVNXVQLSRVWRSNL.URPDWLþQD
GLVSHU]LMD
Optical fibres - Part 1-42: Measurement methods and test procedures - Chromatic
dispersion
Lichtwellenleiter - Teil 1-42: Messmethoden und Prüfverfahren - Chromatische
Dispersion
Fibres optiques - Partie 1-42: Méthodes de mesure de la dispersion chromatique
Ta slovenski standard je istoveten z: EN 60793-1-42:2013
ICS:
33.180.10 2SWLþQDYODNQDLQNDEOL Fibres and cables
SIST EN 60793-1-42:2014 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60793-1-42:2014

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SIST EN 60793-1-42:2014

EUROPEAN STANDARD
EN 60793-1-42

NORME EUROPÉENNE
April 2013
EUROPÄISCHE NORM

ICS 33.180.10 Supersedes EN 60793-1-42:2007


English version


Optical fibres -
Part 1-42: Measurement methods and test procedures -
Chromatic dispersion
(IEC 60793-1-42:2013)


Fibres optiques -  Lichtwellenleiter -
Partie 1-42: Méthodes de mesure Teil 1-42: Messmethoden
et procédures d’essai - und Prüfverfahren -
Dispersion chromatique Chromatische Dispersion
(CEI 60793-1-42:2013) (IEC 60793-1-42:2013)





This European Standard was approved by CENELEC on 2013-02-28. 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels


© 2013 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60793-1-42:2013 E

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SIST EN 60793-1-42:2014
EN 60793-1-42:2013 - 2 -
Foreword
The text of document 86A/1419/CDV, future edition 3 of IEC 60793-1-42, 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 60793-1-42:2013.

The following dates are fixed:
(dop) 2013-11-28
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2016-02-28
standards conflicting with the
document have to be withdrawn

This document supersedes EN 60793-1-42:2007.

EN 60793-1-42:2013 includes the following significant technical changes with respect to
EN 60793 1-42:2007:
a) the inclusion of category B6 single-mode fibres;
b) the deletion of test method D (interferometry).

This standard should be read in conjunction with EN 60793-1-1.

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

Endorsement notice
The text of the International Standard IEC 60793-1-42:2013 was approved by CENELEC as a
European Standard without any modification.

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SIST EN 60793-1-42:2014
- 3 - EN 60793-1-42:2013
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

IEC 60793-1-1 2008 Optical fibres - EN 60793-1-1 2008
Part 1-1: Measurement methods and test
procedures - General and guidance


IEC 60793-1-41 - Optical fibres - EN 60793-1-41 -
Part 1-41: Measurement methods and test
procedures - Bandwidth


IEC 60793-2 - Optical fibres - EN 60793-2 -
Part 2: Product specifications - General

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SIST EN 60793-1-42:2014

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SIST EN 60793-1-42:2014




IEC 60793-1-42

®


Edition 3.0 2013-01




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










Optical fibres –

Part 1-42: Measurement methods and test procedures – Chromatic dispersion




Fibres optiques –

Partie 1-42: Méthodes de mesure et procédures d’essai – Dispersion

chromatique















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX U


ICS 33.180.10 ISBN 978-2-83220-576-1



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 60793-1-42:2014
– 2 – 60793-1-42 © IEC:2013
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 7
3 Overview of methods . 7
3.1 Method A, phase shift . 7
3.2 Method B, spectral group delay in the time domain . 7
3.3 Method C, differential phase shift . 7
4 Reference test methods . 8
4.1 Category A1 and sub-category A4f, A4g and A4h multimode fibres . 8
4.2 Class B single-mode fibres . 8
5 Apparatus . 8
5.1 General . 8
5.2 Launch optics . 8
5.3 High-order mode filter (single-mode) . 8
5.4 Input positioning apparatus . 8
5.5 Output positioning apparatus . 8
5.6 Computation equipment . 9
6 Sampling and specimens . 9
6.1 Specimen length . 9
6.2 Specimen end face . 9
6.3 Reference fibre. 9
7 Procedure. 9
8 Calculations . 9
8.1 General . 9
8.2 Category A1 and sub-category A4f, A4g, A4h multimode fibres and category
B1.1, B1.3 and sub-category B6_a1 and B6_a2 single-mode fibres . 10
8.3 Category B1.2 single-mode fibres . 10
8.4 Category B2 single-mode fibres . 10
8.5 Category B4 and B5 single-mode fibres . 11
9 Results . 11
9.1 Report the following information with each measurement: . 11
9.2 The following information shall be available upon request: . 11
10 Specification information . 11
Annex A (normative) Requirements specific to method A, phase-shift . 12
Annex B (normative) Requirements specific to method B, spectral group delay in the
time domain . 17
Annex C (normative) Requirements specific to method C, differential phase-shift . 21
Annex D (normative) Chromatic dispersion fitting . 26
Bibliography . 28

Figure A.1 – Chromatic dispersion measurement set, multiple laser system (typical) . 13
Figure A.2 – Typical delay and dispersion curves . 13
Figure A.3 – Chromatic dispersion measurement set, LED system (typical) . 15
Figure B.1 – Block diagram, fibre Raman laser system . 18
Figure B.2 – Block diagram, multiple laser diode system . 18

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SIST EN 60793-1-42:2014
60793-1-42 © IEC:2013 – 3 –
Figure C.1 – Chromatic differential phase dispersion measurement set, multiple laser
system . 22
Figure C.2 – Chromatic differential phase dispersion measurement set, LED system . 23
Figure C.3 – Chromatic dispersion measurement set, differential phase by dual
wavelength method . 23
Figure C.4 – Chromatic dispersion measurement set, differential phase by double
demodulation . 24

Table D.1 – Definition of fit types and fit coefficients; equations for group delay and
dispersion coefficient . 26
Table D.2 – Slope equations . 26
Table D.3 – Zero-dispersion wavelength and slope equations . 27

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SIST EN 60793-1-42:2014
– 4 – 60793-1-42 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

OPTICAL FIBRES –

Part 1-42: Measurement methods and test procedures –
Chromatic dispersion

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 60793-1-42 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 2007. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the inclusion of category B6 single-mode fibres;
b) the deletion of test method D (interferometry).
This standard should be read in conjunction with IEC 60793-1-1.

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SIST EN 60793-1-42:2014
60793-1-42 © IEC:2013 – 5 –
The text of this standard is based on the following documents:
CDV Report on voting
86A/1419/CDV 86A/1443/RVC

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the 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 publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication 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 60793-1-42:2014
– 6 – 60793-1-42 © IEC:2013
OPTICAL FIBRES –

Part 1-42: Measurement methods and test procedures –
Chromatic dispersion



1 Scope
This part of IEC 60793 establishes uniform requirements for measuring the chromatic
dispersion of optical fibre, thereby assisting in the inspection of fibres and cables for
commercial purposes.
Chromatic dispersion varies with wavelength. Some methods and implementations measure
the group delay as a function of wavelength and the chromatic dispersion and dispersion
slope are deduced from the derivatives (with respect to wavelength) of this data. This
differentiation is most often done after the data are fitted to a mathematical model. Other
implementations can allow direct measurement (of the chromatic dispersion) at each of the
required wavelengths.
For some (sub-) categories of fibre, the chromatic dispersion attributes are specified with the
parameters of a specific model. In these cases, the relevant recommendation or standard
defines the model appropriate for the definition of the specified parameters. For other fibre
(sub-) categories, the dispersion is specified to be within a given range for one or more
specified wavelength intervals. In the latter case, either direct measurements may be made at
the wavelength extremes or some fitting model may be used to either allow group delay
measurement methods or implementations, or to allow storage of a reduced set of parameters
that may be used to calculate the interpolated dispersion for particular wavelengths which
may not have actual direct measurement values.
Annex D gives a general description of chromatic dispersion fitting and outlines a number of
fitting equations suitable for use with any of the measurement methods or fibre categories.
This standard gives three methods for measuring chromatic dispersion:
– method A: phase shift;
– method B: spectral group delay in the time domain;
– method C: differential phase shift.
Methods A, B, and C apply to the measurement of chromatic dispersion of the following fibres
from IEC 60793-2 over a specified wavelength range:
– category A1 graded-index multimode fibres;
– sub-category A4f, A4g and A4h multimode fibres;
– category B1, B2, B4, B5 and sub-categories B6_a1 and B6_a2 single-mode fibres.
The methods can be applied to laboratory, factory and field measurements of chromatic
dispersion, and the wavelength range of the measurements can be tailored as required.
Measurements are made at temperature as stated in Table 1 of IEC 60793-1-1:2008,
Standard range of atmospheric conditions.
The methods are suitable for fibre or cable lengths greater than 1 km. They may also be
applied to shorter lengths, but accuracy and repeatability may be compromised.
Information common to all methods is contained in Clauses 1 to 8, and information pertaining
to each individual method appears in Annexes A, B and C, respectively.

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SIST EN 60793-1-42:2014
60793-1-42 © IEC:2013 – 7 –
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60793-1-1:2008, Optical fibres – Part 1-1: Measurement methods and test procedures –
General and guidance
IEC 60793-1-41, Optical fibres – Part 1-41: Measurement methods and test procedures –
Bandwidth
IEC 60793-2, Optical fibres – Part 2: Product specifications – General
3 Overview of methods
3.1 Method A, phase shift
This method describes a procedure for determining the chromatic dispersion of the categories
of class B single-mode fibres B1, B2, B4, B5 and sub-categories B6_a1 and B6_a2, category
A1 graded-index multimode fibres and sub-category A4f, A4g and A4h fibres, over a specified
wavelength range using the relative phase shifts among sinusoidally modulated optical
sources of different wavelengths. The sources are typically laser diodes or filtered light
emitting diodes or filtered amplified spontaneous emission (ASE) sources. Relative phase
shifts are converted to relative time delays, and the resultant spectral group delay data are
then fitted to an equation defined for each fibre (sub) category.
3.2 Method B, spectral group delay in the time domain
This method describes a procedure for determining the chromatic dispersion of the categories
of class B single-mode fibres B1, B2, B4, B5 and sub-categories B6_a1 and B6_a2, category
A1 graded-index multimode fibres and sub-category A4f, A4g and A4h fibres with the use of a
Nd:YAG/fibre Raman laser source or multiple laser diodes operating at a number of
wavelengths, both greater than and less than, the typical zero-dispersion wavelength.
In this method, the time difference of optical pulse delay through a known length of fibre at
several wavelengths is measured. A reference set of measurements shall also be taken
through a short reference fibre and data are subtracted from data taken from the fibre under
test to obtain relative spectral group delay. The resultant spectral group delay data are then
fitted to an equation defined for each fibre (sub) category.
3.3 Method C, differential phase shift
This method describes a procedure for determining the chromatic dispersion of the categories
of class B single-mode fibres B1, B2, B4, B5 and sub-categories B6_a1 and B6_a2, category
A1 graded-index multimode fibres and sub-category A4f, A4g and A4h fibres. The dispersion
coefficient at a particular wavelength is determined from the differential group delay between
two closely spaced wavelengths.
In this procedure, a modulated light source is coupled into the fibre under test, and the phase
of the light exiting the fibre at a first wavelength is compared with the phase of the light exiting
at a second wavelength. Average chromatic dispersion over the interval between the two
wavelengths is determined from differential phase shift, wavelength interval, and fibre length.
The chromatic dispersion coefficient at a wavelength medial to the two test wavelengths is
assumed to be equal to the average chromatic dispersion over the interval between the two

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SIST EN 60793-1-42:2014
– 8 – 60793-1-42 © IEC:2013
wavelengths. The resultant chromatic dispersion data are then fitted to an equation defined
for each fibre (sub) category.
4 Reference test methods
4.1 Category A1 and sub-category A4f, A4g and A4h multimode fibres
For category A1 and sub-category A4f, A4g and A4h multimode fibres, method B, spectral
group delay in the time domain, is the reference test method ("RTM"), which shall be the one
used to resolve disputes .
4.2 Class B single-mode fibres
For the categories of class B single-mode fibres B1, B2, B4, B5 and sub-categories B6_a1
and B6_a2, method A, phase shift, is the RTM. In the absence of method A, method C,
differential phase shift, may also be used to resolve disputes.
5 Apparatus
5.1 General
The following apparatus is common to all measurement methods. Annexes A, B and C include
layout drawings and other equipment requirements that individually apply for each of the
methods, A, B and C respectively.
5.2 Launch optics
The output from the signal sources shall be coupled to the fibre under test or the reference
fibre such that the physical path length for each source is held constant during the
measurement. (This requirement ensures that the relative phases of the sources do not
change due to path-length changes.) Suitable devices may include multichannel single-mode
optical switches or demountable optical connectors.
For measurement of category A1, and sub-category A4f, A4g, A4h multimode fibre, launch
conditions shall comply with method A, Impulse response, of IEC 60793-1-41.
5.3 High-order mode filter (single-mode)
For measurement of single-mode fibre, use a method to remove high-order propagating
modes in the wavelength range of interest. An example of such a high-order mode filter is a
single loop of radius sufficiently small to shift cut-off wavelength below the minimum
wavelength of interest.
5.4 Input positioning apparatus
Provide means to couple the input of the specimen to the light source. Examples include the
use of x-y-z micropositioner stages, or mechanical coupling methods such as connectors,
vacuum splices, three-rod splices, etc. The position of the fibre shall remain stable over the
duration of the test.
5.5 Output positioning apparatus
Provide means of positioning the output end of the specimen such that the guided optical
power is coupled to the system detector. Such coupling may include the use of lenses, or may
be a mechanical connection to a detector pigtail.

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5.6 Computation equipment
A digital computer may be used for purposes of equipment control, data acquisition, and
numerical evaluation of the data.
6 Sampling and specimens
6.1 Specimen length
Methods A, B, and C require the specimen to be a fibre or cable of known length sufficiently
long to produce adequate phase measurement accuracy. A typical minimum length is 1 km.
Because sub-category A4f, A4g and A4h fibres have higher loss than category A1 fibres, for
these A4 fibres a minimum length of 100 m is acceptable.
NOTE Reproducibility is affected when using shorter measuring length. Longer lengths generally yield better
reproducibility.
6.2 Specimen end face
Prepare a flat end face, orthogonal to the fibre axis, at the input and output ends of each
specimen.
6.3 Reference fibre
A single mode fibre with known dispersion characteristics shall be used to compensate for
chromatic delays in the optical sources and other equipment components. The length of this
fibre shall be less than or equal to 0,2 % of the specimen length.
In case of A4f, A4g and A4h fibres, the length of the reference fibre shall be less than or
equal to 2 m. If this length is longer than 0,2 % of the length of the specimen under test, the
chromatic dispersion of the reference fibres shall be taken into account by subtracting its
chromatic dispersion value from the results measured on the specimen length.
The temperature of the specimen shall be stable during the measurement within 0,1 °C to
1 °C, depending upon the temporal behaviour due to this change.
7 Procedure
See Annexes A, B and C for the procedures for methods A, B and C, respectively.
Reference fibre measurements are required for all methods. Reference fibre data can be
stored for use in making measurements on the specimens. The reference fibre measurement
procedure should be repeated when equipment changes on the source or receive optics or
electronics occur.
8 Calculations
8.1 General
The calculation of relative delay appropriate for each method is given in Annexes A, B and C,
respectively.
The remainder of this clause describes the numerical fit that can be applied for all methods to
the spectral group delay data normalized by length, τ(λ), see also the Annex D.
λ   is the wavelength   (nm)

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SIST EN 60793-1-42:2014
– 10 – 60793-1-42 © IEC:2013
τ(λ) is the normalized spectral group delay data fit   (ps
...