SIST EN IEC 61744:2023
(Main)Calibration of fibre optic chromatic dispersion test sets (IEC 61744:2023)
Calibration of fibre optic chromatic dispersion test sets (IEC 61744:2023)
IEC 61744:2023 provides standard procedures for the calibration of optical fibre chromatic dispersion (CD) test sets. This document is applicable to all types of CD test sets, with the exception that measurements on multimode optical fibres are excluded. The purpose of this document is to define a standard procedure for calibrating optical fibre chromatic dispersion (CD) test sets. The detailed calibration steps used vary according to the measurement technique used in the CD test set. Whilst it is acknowledged that chromatic dispersion also occurs in multimode fibre and this fibre can be measured on many CD test sets, this document will restrict discussion to single mode fibre measurements applications only. The purpose of the procedures outlined in this document is to focus manufacturers and users of CD test sets toward the reduction of measurement uncertainty in chromatic dispersion determination in optical fibres under all applicable conditions. The procedures apply to calibration laboratories and to the manufacturers or users of CD test sets for the purpose of
a) calibrating CD test sets, and
b) evaluating the level of performance of the instrument.
Use of the procedures also allows correct evaluation of CD test set uncertainty, relative and traceable to appropriate (for example, national) standards. This third edition cancels and replaces the second edition published in 2005. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) updated terms and definitions;
b) the use of a reference fibre standard for calibration is now allowed and at the same level as the other calibration method;
c) Annex B was split into a new Annex B (on calibration uncertainty, still normative) and a new Annex C (on uncertainty at operating conditions, informative);
d) removed former C.3.4 on interferometric method since this method is no longer supported in IEC 60793-1-42;
e) removed Annex D and other references in text to calibration compensation to align with other calibration documents;
f) removed Annex E and other references in text to use of air wavelength since it is not used in the fibre domain.
Kalibrierung von Prüfaufbauten zur Bestimmung der chromatischen Dispersion (IEC 61744:2023)
Etalonnage des ensembles d'essai de la dispersion chromatique fibronique (IEC 61744:2023)
IEC 61744:2023 fournit des procédures normales pour l’étalonnage des ensembles d’essai de la dispersion chromatique (CD) des fibres optiques. Le présent document s’applique à tous les types d’ensembles d’essai CD, à l’exception des mesures sur des fibres optiques multimodales.Le présent document a pour objet de définir une procédure normale pour l’étalonnage des ensembles d’essai de la dispersion chromatique (CD) des fibres optiques. Les étapes détaillées de l’étalonnage varient selon la technique de mesure utilisée sur l’ensemble d’essai CD. Tandis qu’il est admis que la dispersion chromatique se produit également dans des fibres multimodales et que ces fibres peuvent être mesurées sur plusieurs ensembles d’essai CD, le présent document limite l’étude uniquement aux mesures sur des fibres unimodales.Les procédures décrites dans le présent document ont pour objet d’attirer l’attention des fabricants et des utilisateurs des ens embles d’essai CD sur la réduction de l’incertitude de mesure relative à la détermination de la dispersion chromatique dans des fibres optiques, dans toutes les conditions applicables. Les procédures s’appliquent aux laboratoires d’étalonnage et aux fabricants ou utilisateurs des ensembles d’essai CD à des fins:
a) d’étalonnage des ensembles d’essai CD; et
b) d’évaluation du niveau de performance de l’instrument.
L’utilisation des procédures permet aussi une évaluation correcte de l’incertitude de l’ensemble d’essai CD, relative et traçable, par rapport à des étalons appropriés (par exemple des étalons nationaux). constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente:
a) mise à jour des termes et définitions;
b) l’utilisation d’une fibre de référence (normale) pour l’étalonnage est désormais autorisée et est considérée assurer le même niveau que les autres méthodes d’étalonnage;
c) l’Annexe B a été scindée en une nouvelle Annexe B (sur l’incertitude d’étalonnage, qui reste une annexe normative) et en une nouvelle Annexe C (sur l’incertitude dans les conditions de fonctionnement, informative);
d) suppression de l’ancien C.3.4 sur la méthode interférométrique, car celle-ci n’est plus prise en charge dans l’IEC 60793-1-42;
e) suppression de l’Annexe D et des autres références dans le texte à la compensation d’étalonnage, afin d’assurer la cohérence avec les autres documents d’étalonnage;
f) suppression de l’Annexe E et des autres références dans le texte à l’utilisation de longueur d’onde dans l’air, car cela n’est pas utilisé dans le domaine fibronique.
Umerjanje pribora za preskušanje kromatske disperzije (IEC 61744:2023)
Standard IEC 61744:2023 določa standardne postopke za umerjanje pribora za preskušanje kromatske disperzije (CD). Ta dokument se uporablja za vse vrste pribora za preskušanje kromatske disperzije, pri čemer so izvzete meritve na večrodovnih optičnih vlaknih. Namen tega dokumenta je opredeliti standardni postopek za umerjanje pribora za preskušanje kromatske disperzije. Uporaba podrobnih korakov umerjanja se razlikuje glede na tehniko merjenja, uporabljeno v priboru za preskušanje kromatske disperzije. Čeprav je znano, da se kromatska disperzija pojavlja tudi v večrodovnih vlaknih in je ta vlakna mogoče izmeriti s številnim priborom za preskušanje kromatske disperzije, ta dokument obravnava samo meritve enorodnih vlaken. Namen postopkov, opisanih v tem dokumentu, je usmeriti proizvajalce in uporabnike pribora za preskušanje kromatske disperzije k zmanjšanju negotovosti meritev pri določanju kromatske disperzije v optičnih vlaknih pod vsemi veljavnimi pogoji. Postopki se uporabljajo za laboratorije, ki izvajajo umerjanje, ter proizvajalce in uporabnike pribora za preskušanje kromatske disperzije za namene
a) umerjanja pribora za preskušanje kromatske disperzije in
b) ocenjevanja ravni zmogljivosti instrumenta.
Uporaba postopkov prav tako omogoča pravilno vrednotenje negotovosti pribora za preskušanje kromatske disperzije v povezavi z ustreznimi (na primer nacionalnimi) standardi. Tretja izdaja razveljavlja in nadomešča drugo izdajo, objavljeno leta 2005. Ta izdaja je tehnično popravljena izdaja. Ta izdaja v primerjavi s prejšnjo vključuje naslednje pomembne tehnične spremembe:
a) Izrazi in definicije so posodobljeni.
b) Uporaba referenčnega standarda o vlaknih za umerjanje je zdaj dovoljena in na enaki ravni kot druga metoda umerjanja.
c) Dodatek B je razdeljen v novi dodatek B (v zvezi z negotovostjo pri umerjanju, še vedno normativni) in dodatek C (v zvezi z negotovostjo pri pogojih delovanja, informativni).
d) Točka C.3.4 o interferometrični metodi je odstranjena, ker ni več podprta v standardu IEC 60793-1-42.
e) Dodatek D in drugi sklici v besedilu na kompenzacijo umerjanja so odstranjeni za uskladitev z drugimi dokumenti o umerjanju.
f) Dodatek F in drugi sklici v besedilu na uporabo valovne dolžine v zraku so odstranjeni, saj se le-ta ne uporablja za vlakna.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2023
Umerjanje pribora za preskušanje kromatske disperzije (IEC 61744:2023)
Calibration of fibre optic chromatic dispersion test sets (IEC 61744:2023)
Kalibrierung von Prüfaufbauten zur Bestimmung der chromatischen Dispersion (IEC
61744:2023)
Etalonnage des ensembles d'essai de la dispersion chromatique fibronique (IEC
61744:2023)
Ta slovenski standard je istoveten z: EN IEC 61744:2023
ICS:
33.140 Posebna merilna oprema za Special measuring
uporabo v telekomunikacijah equipment for use in
telecommunications
33.180.01 Sistemi z optičnimi vlakni na Fibre optic systems in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN IEC 61744
NORME EUROPÉENNE
EUROPÄISCHE NORM May 2023
ICS 33.180.01 Supersedes EN 61744:2005
English Version
Calibration of fibre optic chromatic dispersion test sets
(IEC 61744:2023)
Étalonnage des ensembles d'essai de la dispersion Kalibrierung von Prüfaufbauten zur Bestimmung der
chromatique fibronique chromatischen Dispersion
(IEC 61744:2023) (IEC 61744:2023)
This European Standard was approved by CENELEC on 2023-05-09. 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye 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
© 2023 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61744:2023 E
European foreword
The text of document 86/615/FDIS, future edition 3 of IEC 61744, prepared by IEC/TC 86 "Fibre
optics" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2024-02-09
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2026-05-09
document have to be withdrawn
This document supersedes EN 61744:2005 and all of its amendments and corrigenda (if any).
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.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61744:2023 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 standard indicated:
ISO/IEC 17025 NOTE Approved as EN ISO/IEC 17025
IEC 60793-1-42 NOTE Approved as EN 60793-1-42
IEC 60793-2-50 NOTE Approved as EN IEC 60793-2-50
IEC 60825-1 NOTE Approved as EN 60825-1
IEC 61315 NOTE Approved as EN IEC 61315
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.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60050-731 - International Electrotechnical Vocabulary - - -
Chapter 731: Optical fibre communication
IEC 62129-1 - Calibration of wavelength/optical frequency EN 62129-1 -
measurement instruments - Part 1: Optical
spectrum analyzers
IEC 62129-2 - Calibration of wavelength/optical frequency EN 62129-2 -
measurement instruments - Part 2:
Michelson interferometer single
wavelength meters
ISO/IEC Guide 98-3 - Uncertainty of measurement - Part 3: - -
Guide to the expression of uncertainty in
measurement (GUM:1995)
IEC 61744 ®
Edition 3.0 2023-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Calibration of fibre optic chromatic dispersion test sets
Étalonnage des ensembles d’essai de la dispersion chromatique fibronique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.01 ISBN 978-2-8322-6734-9
– 2 – IEC 61744:2023 © IEC 2023
CONTENTS
FOREWORD . 4
0 Introduction . 6
0.1 Chromatic dispersion in optical fibres . 6
0.2 Chromatic dispersion (CD) test sets . 6
0.3 Overview of calibration procedures described in this document . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Calibration . 11
4.1 General . 11
4.2 Preparation for calibration . 12
4.2.1 General advice and organization. 12
4.2.2 Environmental conditions requirements . 12
4.2.3 Measurement equipment requirements . 12
4.2.4 Traceability . 12
4.3 Calibration procedure . 13
5 Wavelength and delay calibration procedure . 13
5.1 Wavelength calibration procedure . 13
5.1.1 General . 13
5.1.2 Discrete sources . 13
5.1.3 Tuneable sources . 14
5.1.4 Uncertainties and reporting . 16
5.2 Delay (dispersion) calibration procedure . 17
5.2.1 General . 17
5.2.2 Equipment and preparation . 17
5.2.3 Calibration procedure . 18
5.2.4 Uncertainties and reporting . 19
6 Calibration using a reference fibre . 19
6.1 General . 19
6.2 Equipment and preparation . 20
6.3 Procedure . 20
6.4 Uncertainties and reporting . 21
7 Documentation . 21
7.1 General . 21
7.2 Calibration certificate contents . 21
Annex A (normative) Mathematical basis for measurement uncertainty calculations . 22
A.1 General . 22
A.2 Deviations . 22
A.3 Uncertainties type A . 22
A.4 Uncertainties type B . 23
A.5 Determining the combined standard uncertainty . 24
A.6 Reporting . 25
Annex B (normative) Calibration uncertainty . 26
B.1 General . 26
B.2 Wavelength and delay calibration uncertainties . 26
B.2.1 Wavelength uncertainties . 26
IEC 61744:2023 © IEC 2023 – 3 –
B.2.2 Optical delay calibration uncertainty . 26
B.2.3 Effect of dispersion modelling . 26
B.3 Uncertainty of a calibration using a reference fibre . 27
Annex C (informative) Uncertainty at operating conditions . 28
C.1 General . 28
C.2 Fibre related uncertainties . 28
C.2.1 Axial fibre strain. 28
C.2.2 Fibre temperature . 28
C.2.3 Second order modes . 29
–
C.2.4 OH absorption . 29
C.2.5 Total fibre loss . 29
C.2.6 Optical reflections . 29
Annex D (informative) Chromatic dispersion . 30
D.1 Chromatic dispersion in fibres . 30
D.2 Description of chromatic dispersion test sets . 30
D.3 Measurement techniques . 31
D.3.1 General . 31
D.3.2 Pulse delay method . 31
D.3.3 Phase shift method . 32
D.3.4 Differential phase shift method . 32
D.4 Fibre chromatic dispersion specifications . 32
Bibliography . 33
Figure 1 – Example of a traceability chain . 9
Figure 2 – Typical optical delay line artefact for CD test set delay calibration . 17
Figure 3 – Typical differential delay (dispersion) simulator for CD test set calibration . 18
Figure 4 – Reference fibre comparison . 20
Figure A.1 – Deviation and uncertainty type B and how to replace both by an
appropriately larger uncertainty . 23
Figure D.1 – Schematic diagram of a CD test set . 31
– 4 – IEC 61744:2023 © IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CALIBRATION OF FIBRE OPTIC CHROMATIC
DISPERSION TEST SETS
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.
IEC 61744 has been prepared by IEC technical committee 86: Fibre optics. It is an International
Standard.
This third edition cancels and replaces the second edition published in 2005. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) updated terms and definitions;
b) the use of a reference fibre standard for calibration is now allowed and at the same level as
the other calibration method;
c) Annex B was split into a new Annex B (on calibration uncertainty, still normative) and a new
Annex C (on uncertainty at operating conditions, informative);
d) removed former C.3.4 on interferometric method since this method is no longer supported
in IEC 60793-1-42;
e) removed Annex D and other references in text to calibration compensation to align with
other calibration documents;
IEC 61744:2023 © IEC 2023 – 5 –
f) removed Annex E and other references in text to use of air wavelength since it is not used
in the fibre domain.
The text of this International Standard is based on the following documents:
Draft Report on voting
86/615/FDIS 86/617/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under 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.
– 6 – IEC 61744:2023 © IEC 2023
0 Introduction
0.1 Chromatic dispersion in optical fibres
Chromatic dispersion is the variation with optical light wavelength of the light propagation delay
time in a length of fibre. This variation can cause bandwidth limitation in the fibre when used to
transmit communication signals. For a more detailed explanation, refer to Annex D and
IEC 60793-1-42.
0.2 Chromatic dispersion (CD) test sets
CD test sets are used to measure the chromatic dispersion properties of optical fibres and
typically comprise an optical source of known wavelength(s), a fibre light input coupling and
output coupling means, optical detection means, and electronic or optical means of determining
the optical delay or dispersion at the source wavelength. There are several variants each
requiring slightly different calibration techniques. Refer to Annex D for further details.
In general, all CD test sets produce an output of fibre delay or dispersion versus the light
wavelength, typically in graphical form.
In essence, all CD test sets operate with wavelength as a programmed (independent) variable,
usually the abscissa (x-axis) and dispersion or time delay as the ordinate (y-axis) as a measured
(dependent) variable. By their nature, fibre chromatic dispersion measurements require multiple
wavelengths to be programmed. Even in the case of a single dispersion point obtained using
the differential phase shift method, two separate wavelength values are used. It is also typical
to expect a wide range of dispersion values over a range of wavelengths to be measured.
0.3 Overview of calibration procedures described in this document
The requirement to calibrate the CD test set, traceable to known standards, is essential for
quality control in fibre optic production, fibre research and similar activities. This document
describes the detailed procedures used to establish calibration of a CD test set.
Calibration of a CD test set is established by applying known artefacts or standards (themselves
calibrated to reference standards) to the CD test set and measuring its response.
Primarily, the artefacts or standards used are as follows.
a) Wavelength artefact(s) or traceable wavelength measuring instruments used to calibrate the
light source wavelength(s) used by the CD test set. This is to establish the correct excitation
wavelength for the system (the "x-axis").
b) Delay or dispersion artefact(s) used to calibrate the delay or dispersion response of the CD
test set (the "y-axis").
c) Traceable chromatic dispersion reference fibre used to calibrate the CD test set. This
method allows a simultaneous calibration of the whole CD test set, including the
measurement of the delay or dispersion response of the CD test set as a function of
wavelength and also the internal data processing part. A proper selection of the type of
reference fibre is important, especially for an accurate calibration of the zero dipersion
wavelength.
Calibration can only be carried out using these artefacts; the use of a known standard fibre
(reference fibre described in c)) whose chromatic dispersion is known is recommended as the
fibre forms a stable source of known dispersion and may be used as a simple dispersion
artefact.
If it is found that the CD test set measurement results have changed significantly compared to
the user requirements (i.e. the test set has drifted by more than the repeatability), then
adjustment may be carried out depending on the need.
In this document, the reference medium for wavelength and the velocity of light is assumed to
be in vacuum, and hence define the refractive index = 1,000 000 0.
IEC 61744:2023 © IEC 2023 – 7 –
CALIBRATION OF FIBRE OPTIC CHROMATIC
DISPERSION TEST SETS
1 Scope
This document provides standard procedures for the calibration of optical fibre chromatic
dispersion (CD) test sets.
This document is applicable to all types of CD test sets, with the exception that measurements
on multimode optical fibres are excluded.
The purpose of this document is to define a standard procedure for calibrating optical fibre
chromatic dispersion (CD) test sets. The detailed calibration steps used vary according to the
measurement technique used in the CD test set.
Whilst it is acknowledged that chromatic dispersion also occurs in multimode fibre and this fibre
can be measured on many CD test sets, this document will restrict discussion to single mode
fibre measurements applications only.
The purpose of the procedures outlined in this document is to focus manufacturers and users
of CD test sets toward the reduction of measurement uncertainty in chromatic dispersion
determination in optical fibres under all applicable conditions. The procedures apply to
calibration laboratories and to the manufacturers or users of CD test sets for the purpose of
a) calibrating CD test sets, and
b) evaluating the level of performance of the instrument.
Use of the procedures also allows correct evaluation of CD test set uncertainty, relative and
traceable to appropriate (for example, national) standards.
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 60050-731, International Electrotechnical Vocabulary (IEV) – Chapter 731: Optical fibre
communication, available at www.electropedia.org
IEC 62129-1, Calibration of wavelength/optical frequency measurement instruments – Part 1:
Optical spectrum analyzers
IEC 62129-2, Calibration of wavelength/optical frequency measurement instruments – Part 2:
Michelson interferometer single wavelength meters
ISO/IEC Guide 98-3, Uncertainty of measurement – Guide to the expression of uncertainty in
measurement (GUM:1995)
– 8 – IEC 61744:2023 © IEC 2023
3 Terms and definitions
For the purposes of this document, the terms and definitions contained in IEC 60050-731 and
the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
accredited calibration laboratory
calibration laboratory authorized by the appropriate national standards laboratory to issue
calibration certificates with a minimum specified uncertainty that demonstrate traceability to
national standards
3.2
adjustment
set of operations carried out on an instrument in order that it provides given indications
corresponding to given values of the measurand
3.3
artefact
device, instrument, or equipment used in the process of calibrating a CD test set for wavelength,
delay, or chromatic dispersion
3.4
calibration
set of operations that establish, under specified conditions, the relationship between the values
of quantities indicated by a measuring instrument and the corresponding values realized by
measurement standards
Note 1 to entry: The result of a calibration permits either the assignment of values of measurands to the indications
or the determination of corrections with respect to indications.
Note 2 to entry: A calibration may also determine other metrological properties such as the effect of influence
quantities.
Note 3 to entry: The result of a calibration may be recorded in a document, sometimes called a calibration certificate
or a calibration report.
Note 4 to entry: See also ISO/IEC Guide 99:2007, 2.39.
3.5
traceability chain
unbroken chain of comparison using standards
Note 1 to entry: See Figure 1.
IEC 61744:2023 © IEC 2023 – 9 –
Figure 1 – Example of a traceability chain
3.6
centroidal wavelength
power-weighted mean wavelength of a light source in vacuum
Note 1 to entry: For a continuous source spectrum, the centroidal wavelength λ in vacuum is defined by the
c
following integral, where the integration limits enclose the entire spectrum of the source. However, it is usually
sufficient to perform the integral or summation over the spectrum where the spectral density p(λ) or power P is higher
i
than 0,1 % of the maximum spectral density p(λ) or power P :
i
λ = (1/ P ) × [ p(λ) × λ dλ]
(1)
c total
∫
where
P = p(λ) d is the total optical source power.
total
∫
For a spectrum consisting of i discrete lines, the centroidal wavelength in vacuum λ is defined as:
c
λ = (1/ P ) × pλ
(2)
c total ∑ i i
i
where
p(λ) is the spectral power spectral density of the source in W/nm;
λ is the centroidal wavelength in vacuum in nanometers;
c
th
λ is the i discrete line in nm;
i
p is the power levels at λ in W;
i i
=
P p is the total power in W.
total ∑ i
i
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3.7
chromatic dispersion (CD) test sets
instrument capable of measuring the chromatic dispersion of a single mode fibre at various
wavelengths in the transmission windows of interest
Note 1 to entry: Windows of interest are typically the 1 310 nm and/or 1 550 nm wavebands.
3.8
correction offset
CO
number that is added to or subtracted from the measurement result of a CD test set to correct
for a known physical effect or deviation
3.9
instrument state
complete description of the measurement conditions and state of the CD test set during the
calibration process
Note 1 to entry: Typical parameters of the instrument state are the wavelength range in use, the data fit model (as
applicable), warm-up time, and other instrument settings.
3.10
measurement result
displayed or electrical output of any CD test set, in
–1 –1
• dispersion D in units of ps × nm × km ,
• lambda zero λ in units of nm,
–2 –1
• zero dispersion slope S in units of ps × nm × km ,
after completing all actions suggested by the operating instructions, for example warm-up
3.11
national standard
standard recognized by a national decision to serve in a country as the basis for assigning
values to other standards of the quantity concerned
Note 1 to entry: For more information, see ISO/IEC Guide 99:2007, 5.3.
3.12
national standards laboratory
national metrology institute
laboratory which maintains the national standard
3.13
operating conditions
appropriate set of specified ranges of values of influence quantities usually wider than the
reference conditions for which the uncertainties of a measuring instrument are specified
3.14
reference standard
standard, generally having the highest metrological quality available at a given location or in a
given organization, from which measurements made therein are derived
Note 1 to entry: For more information, see ISO/IEC Guide 99:2007, 5.6.
IEC 61744:2023 © IEC 2023 – 11 –
3.15
scaling factor
SF
ratio of known standard values for a standard artefact to the values indicated by the CD test set
when no correction offsets are applied
Note 1 to entry: The factors can apply to wavelength, delay (dispersion) calibration, as well as to recorded zero
dispersion wavelength, slope and actual dispersion data values when using a calibrated reference fibre.
3.16
spectral bandwidth
B
full-width at half-maximum (FWHM) of the source spectrum
Note 1 to entry: If the source is a laser diode with a multiple-longitudinal mode spectrum, then the FWHM spectral
bandwidth B is the RMS spectral bandwidth, multiplied by 2,35 (assuming the source has a Gaussian envelope):
2 2 ½
B = 2,35 × [{ ( 1/ P ) × ( p λ )} – λ ]
total ∑ i i c
(3)
i
where
λ is the centroidal wavelength (see 3.6) of the laser diode, in nm;
c
P = p is the total power, in W;
total ∑ i
i
th
p is the power of i longitudinal mode, in W;
i
th
λ is the vacuum wavelength of i longitudinal mode, in nm.
i
3.17
traceability
property of the result of a measurement or the value of a standard whereby it can be related to
stated references, usually national or international standards, through an unbroken chain of
comparisons all having stated uncertainties
Note 1 to entry: For more information, see ISO/IEC Guide 99:2007, 2.41.
3.18
transfer standard
reference standard
standard, generally having the highest metrological quality available at a given location or in a
given organization, from which measurements made therein are derived, and used to calibrate
working standards
3.19
working standard
standard that is used routinely to calibrate measuring instruments
Note 1 to entry: A working standard is usually calibrated against a transfer standard (3.18).
Note 2 to entry: For more information, see ISO/IEC Guide 99:2007, 5.7.
4 Calibration
4.1 General
Clause 4 summarizes the action of calibrating a chromatic dispersion (CD) test set and details
the recommendations for the environmental requirements of the calibration facility.
– 12 – IEC 61744:2023 © IEC 2023
4.2 Preparation for calibration
4.2.1 General advice and organization
The accreditation calibration laboratory should ensure that suitable requirements for calibration
are followed.
NOTE Guidance about good practices for calibration are in ISO/IEC 17025 [1] .
There should be a documented measurement procedure for each type of calibration performed,
giving step-by-step operating instructions and equipment to be used.
4.2.2 Environmental conditions requirements
The following requirements shall be observed:
a) all tests shall be performed at an ambient temperature of 23 °C ± 3 °C (or tighter);
b) the CD test set, test apparatus and equipment shall be given sufficient time to reach thermal
equilibrium with the environment in accordance with the manufacturer's recommendations
for each item of equipment, before commencement of any part of the calibration procedure;
c) the instrument state of the CD test set and test equipment shall be recorded, a precondition
for reproducible measurements;
d) connectors and optical input ports, etc. should always be cleaned before measurement.
If the current calibration conditions are different from those of the calibration standards, make
sure that the calibration standards remain traceable with the required level of uncertainty.
4.2.3 Measurement equipment requirements
Calibration of test equipment with traceability described in 4.2.4 is mandatory. The tests
described require the use of some or all of the following:
a) a variable optical attenuator;
b) a wavelength measuring device (an optical spectrum analyzer calibrated according to
IEC 62129-1 or wavelength meter calibrated according to IEC 62129-2) for discrete
wavelength sources such as lasers;
c) a wavelength standard (for example, He-Ne laser or other wavelength standard) for tuneable
monochromator-based systems;
d) an optical delay line artefact (differential optical delay line artefact) for delay (dispersion)
calibration;
e) a calibrated chromatic dispersion reference fibre.
4.2.4 Traceability
Ensure that all test equipment which has significance to the calibration result has been
calibrated in an unbroken traceability chain to the appropriate national standard. The
recalibration period(s) shall be defined and documented. The details of traceability for this test
equipment shall be made available on request (see Clause 7).
___________
Numbers in square brackets refer to the Bibliography.
IEC 61744:2023 © IEC 2023 – 13 –
4.3 Calibration procedure
The calibration methods for all types of CD test sets calibrate either
a) the source wavelength(s), and the delay (dispersion) response of the set separately, which
allows determining relevant correction offset and/or scaling factors for both quantities
separately, or
b) the full test set in a single measurement, using a calibrated chromatic dispersion reference
fibre, which allows determining relevant offsets for chromatic dispersion, dispersion slope
and zero dispersion wavelength.
In case a), the user shall first ascertain which type of light source(s) (for example lasers or
LED/filter/ monochromator) is in use and which measurement technique is in use in the CD test
set.
Some CD test sets can perform more than one measurement technique, in which case it would
be necessary to separately calibrate the CD test set for all measurement techniques in use,
under the auspices of this document.
For each CD test set calibration, the procedure consists of the following.
a) Use the procedure appropriate to the CD test set measurement method for
1) calibration of the wavelength parameter (see 5.1):
i) for discrete wavelength source systems, use the procedure of 5.1.2;
ii) for continuously tuneable source systems, use the procedure of 5.1.3.
2) Use equipment appropriate to the CD test set measurement method; calibrate the delay
parameter using the procedure of 5.2.3.
b) Or, instead of the procedures in a), only calibrate the chromatic dispersion using the
procedure of Clause 6.
c) Report and record on a certificate the calibration results according to Clause 7. The CD test
set is now fully calibrated to national standards with the specified uncertainty.
5 Wavelength and delay calibration procedure
5.1 Wavelength calibration procedure
5.1.1 General
5.1 describes procedures for calibration of wavelength in CD test sets. The technical principle
is to apply calibrated wavelength artefacts such as external sources, optical transmission
elements or other artefacts to determine the centroidal wavelength(s) used in the CD test set
for dispersion measurement. The actual wavelengths used may then be adjusted. The process
of calibration differs according to the light source used in the CD test set under consideration.
For sets using lasers or other discrete wavelength sources, see 5.1.2; for continuously variable
(tuneable) sources, see 5.1.3. In either case, see 5.1.4 to report the calibration results.
5.1.2 Discrete sources
Many CD test sets use discrete laser diodes or discrete filtered LED/lamp sources, and the
procedure below shall be used to calibrate the wavelength. Any additional measurement
apparatus, artefact or equipment used in this calibration procedure shall be prior calibrated to
traceable standards. In these instruments, the following procedure shall be used.
a) Establish that the test equipment requirements have been met (see 4.2.3).
b) Establish that the test environmental conditions have been met (see 4.2.2).
c) Set up the CD test set instrument state to the appropriate settings for calibration procedures
(see 4.2.2).
– 14 – IEC 61744:2023 © IEC 2023
d) Refer to Annex B to consider the effects and technical origins of uncertainty sources.
e) For each discrete source, measure the wavelength using one of the following items, first
ensuring that it is itself calibrated:
1) an optical spectrum analyzer;
2) a wavelength meter;
f) For each discrete source, measure the centroidal wavelength λ and the spectral bandwidth
c
B (as defined in 3.6 and 3.16 respectively).
g) The possibility of wavelength shift under different conditions of source modulation (chirp)
shall be considered. Evaluation of the individual uncertainties of the source wavelengths
shall also be carried out. The wavelength uncertainty may vary with the actual wavelength
(region) used, so that in the subsequent evaluation of dispersion uncertainties, the correct
uncertainty value(s) shall be used. Use the centroidal wavelength λ and spectral bandwidth
c
B for subsequent calculation of the time delay and or dispersion curve. Suitable wavelength
uncertainty fitting techniques are described in IEC 62129-1.
h) The calibrated wavelengths of the source(s) chosen shall be used in the calculation of the
monochromator tuning relation (calibration curve).
5.1.3 Tuneable sources
5.1.3.1 General
For CD test sets employing continuously variable (tuneable) sources, the wavelength calibration
involves determining the wavelength calibration of the monochromator used for wavelength
selection over the wavelength range of the CD test set. This may be accomplished in one of
three ways (see 5.1.3.2, 5.1.3.3, 5.1.3.4), or a combination of these as detailed below. All and
any additional apparatus, artefacts or equipment used in these calibration procedures shall be
calibrated to traceable standards.
In all cases of standard sources and filters, the spectral bandwidth should be 5 nm or less
FWHM. Similarly, the spectral resolution of wavelength measurement apparatus should be
commensurate with the wavelength uncertainty required.
5.1.3.2 Method A
This method uses a sufficient number of external sources of known optical wavelengths (or set
of wavelengths) at the input to the monochromator.
a) Each known external light source shall be calibrated, stable and of well-defined wavelength
and of discrete line character. The monochromator calibration may be referenced to a
fundamental physical phenomenon by deriving the test wavelengths from classical sources
of discrete wavelengths. These could take the form of a 633 nm He-Ne laser, argon laser,
mercury lamp, etc. to which the monochromator within the CD test set may be tuned using
various diffraction orders. The intention is to obtain a sufficient number of calibration points
for the monochromator drive to fully cover the wavelength range of the CD test set (see
IEC 62129-1). It is also possible to obtain calibration points by using a suitable (broadband)
source and known calibrated monochromator. The spectral width of the sources, in any
case, should be less than 5 nm (see 5.1.4).
b) Ensure that the optical path of the calibration artefact exactly replicates the normal operating
conditions in the CD test set. It is important to assess the uncertainties due to variations in
the optical alignment between calibration and normal use of the CD test set.
c) Establish that the test equipment requirements have been met (see 4.2.3).
d) Establish that the test environmental conditions have been met (see 4.2.2).
e) Set up the CD test set instrument state to the appropriate settings for calibration procedures
(see 4.2.2).
f) Refer to Annex B to consider the effects and technical origins of uncertainty sources.
IEC 61744:2023 © IEC 2023 – 15 –
g) For each source wavelength or diffraction order setting, the centroidal wavelength λ and
c
spectral bandwidth B (see 3.6 and 3.16) shall be measured.
h) Evaluation of the
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