SIST EN 61744:2004

EUROPEAN STANDARD EN 61744
NORME EUROPÉENNE
EUROPÄISCHE NORM April 2001
ICS 33.180.01
English version
Calibration of fibre optic chromatic dispersion test sets
(IEC 61744:2001)
Etalonnage des ensembles Kalibrierung von Prüf-Aufbauten zur
de la dispersion chromatique Bestimmung der chromatischen
des fibres optiques Dispersion
(CEI 61744:2001) (IEC 61744:2001)
This European Standard was approved by CENELEC on 2001-01-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat 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 Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway,
Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61744:2001 E

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EN 61744:2001 - 2 -
Foreword
The text of document 86/170/FDIS, future edition 1 of IEC 61744:2001, prepared by IEC TC 86, Fibre
optics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 61744 on 2001-01-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2001-11-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-01-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annexes A, B and ZA are normative and annexes C and D are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61744:2001 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
           IEC 61315      NOTE: Harmonized as EN 61315:1997 (not modified).
__________

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- 3 - «Field32»
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
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 60050-731 1991 International Electrotechnical --
Vocabulary (IEV)
Chapter 731: Optical fibre
communication
IEC 60793-1-1 1995 Optical fibres --
Part 1: Generic specification -- Section
1: General
IEC 60825-1 1993 Safety of laser products EN 60825-1 1994
Part 1: Equipment classification, + February 1995
requirements and user's guide + A11 1996
1)
IEC 62129 Calibration of optical spectrum --
analyzers
ISO 9000 Series Quality management and quality EN ISO 9000 Series
assurance standards - Part 1:
Guidelines for selection and use
ISO 10012-1 1992 Quality assurance requirements for--
measuring equipment
Part 1: Metrological confirmation system
for measuring equipment
ISO 10012-2 1997 Part 2: Guidelines for control of --
measurement processes
ISO 1993 Guide to the Expression of Uncertainty--
in Measurement (ISBN 02-67-10188-9)
2)
EN 45001 1989 General criteria for the operation of--
testing laboratories

1)
To be published.
2)
EN 45001:1989 is superseded by EN ISO/IEC 17025:2000.

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INTERNATIONAL IEC
STANDARD
61744
First edition
2001-02
Calibration of fibre optic chromatic
dispersion test sets
Etalonnage des ensembles d'essai de la dispersion
chromatique des fibres optiques
 IEC 2001  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http://www.iec.ch
Commission Electrotechnique Internationale
PRICE CODE
X
International Electrotechnical Commission
For price, see current catalogue

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– 2 – 61744  IEC:2001(E)
CONTENTS
Page
FOREWORD . 4
INTRODUCTION .5
Clause
1 Scope . 7
2 Normative references . 7
3 Terms and definitions. 8
4 Calibration . 14
4.1 Rationale for calibration of CD test sets. 14
4.1.1 (Full) calibration . 14
4.1.2 Calibration checking . 14
4.2 Preparation for calibration . 15
4.2.1 General advice and organization. 15
4.2.2 Test environmental requirements. 16
4.2.3 Measurement equipment requirements . 16
4.2.4 Traceability . 16
4.3 Calibration procedure. 16
4.4 Calibration checking procedure . 17
5 Wavelength calibration procedure. 17
5.1 General. 17
5.2 Discrete sources . 17
5.3 Tunable sources . 18
5.3.1 Method A . 18
5.3.2 Method B . 19
5.3.3 Method C . 20
5.4 Uncertainties and reporting . 20
6 Delay [dispersion] calibration procedure . 20
6.1 General. 20
6.2 Equipment and preparation . 20
6.2.1 Pulse delay CD test sets. 21
6.2.2 Phase shift CD test sets . 22
6.2.3 Interferometric CD test sets. 22
6.2.4 Differential phase shift CD test sets. 22
6.3 Calibration procedure. 23
6.4 Uncertainties and reporting . 23
7 Calibration checking procedure . 23
7.1 General. 23
7.2 Equipment and preparation . 24
7.3 Procedure . 24
7.4 Uncertainties and reporting . 25
7.5 Generation of infant reference fibre . 25
8 Documentation. 26
8.1 Specifications, measurement data and uncertainties. 26
8.2 Traceability information . 27

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61744  IEC:2000(E) – 3 –
Annex A (normative) Mathematical basis. 28
A.1 Deviations. 28
A.2 Uncertainties type A . 28
A.3 Uncertainties type B . 29
A.4 Accumulation of uncertainties. 30
A.5 Reporting . 31
Annex B (normative) Assessment of operational uncertainties. 32
B.1 Wavelength calibration uncertainties . 32
B.2 Fibre length uncertainty. 33
B.3 Optical delay variation . 33
B.4 Instrumentation uncertainties.34
B.5 Effect of dispersion modelling. 37
B.6 Fibre related uncertainties. 37
B.7 System dispersion uncertainties . 38
Annex C (informative) Chromatic dispersion. 39
C.1 Chromatic dispersion in fibres . 39
C.2 Description of chromatic dispersion test sets . 39
C.3 Measurement techniques.40
C.4 Fibre chromatic dispersion specifications . 41
Annex D (informative) CD test set calibration compensation. 42
D.1 Calibration compensation . 42
D.2 Calibrated reference fibres . 43
D.3 Calibration compensation procedure. 43
Bibliography . 45

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– 4 – 61744  IEC:2001(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CALIBRATION OF FIBRE OPTIC CHROMATIC
DISPERSION TEST SETS
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any divergence
between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the
latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61744 has been prepared by IEC technical committee 86: Fibre
optics.
The text of this standard is based on the following documents:
FDIS Report on voting
86/170/FDIS 86/173/RVD
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 3.
Annexes A and B form an integral part of this standard.
Annexes C and D are for information only.
The committee has decided that the contents of this publication will remain unchanged until
2002. At this date, the publication will be
reconfirmed;
withdrawn;
replaced by a revised edition, or
amended.

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61744  IEC:2000(E) – 5 –
INTRODUCTION
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 C and
IEC 60793-1-1.
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 C 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. Thus, wavelength constitutes the ‘x-axis’ and delay or
dispersion the ‘y-axis’.
Overview of calibration procedures described in this standard
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 standard
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, measuring its response and
adjusting (correcting) the CD test set to achieve results that match the standards used. In this
way the CD test set results will be brought to close agreement with other CD test sets also
calibrated in the manner described in this standard.
Primarily the artefacts or standards used are as follows:
a) wavelength artefact(s) 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’) in
order that the correct delay or dispersion (the ‘y-axis’) be determined subsequently;
b) delay or dispersion artefact(s) used to calibrate the delay or dispersion response of the CD
test set (the ‘y-axis’).
Calibration can only be carried out using these artefacts. After a calibration has been
completed, a calibration period is defined over which the CD test set is deemed to remain
calibrated. At the end of this period, it would be necessary to establish if the CD test set
calibration requires updating (changing); this can be performed using the artefact described
above, or by use of a known standard fibre (reference fibre) whose chromatic dispersion is
known. This is referred to as calibration checking. The fibre forms a stable source of known
dispersion and may be used as a simple dispersion artefact.
If it is found that the calibration has not changed within the required uncertainty limits, then it is
possible to simply extend the calibration period again by a defined amount.
If, however, 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), then calibration using the
artefacts (if not already carried out at this time) should be carried out and the calibration
renewed.

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– 6 – 61744  IEC:2001(E)
The above rationale ensures that the CD test set calibration is only ever performed using known
standards (artefacts), but that if the CD test set is sufficiently stable over the calibration period
selected, then a simple check of calibration can suffice to ascertain this and to (justify) allow
the extension of the calibration period. The extension can be repeated indefinitely over many
calibration periods, provided the CD test set continues to remain within uncertainty limits over
the entire set of calibration periods.
In order to be considered calibrated and in conformance with this standard, a CD test set must
have its calibration adjusted based on comparison to artefacts for the primary parameters of
wavelength and delay [dispersion]. In all cases, this calibration of primary parameters is
necessary, but may or may not be sufficient, to ensure calibration of the CD test set to the
required uncertainty.
In addition, it may be necessary to also confirm or compensate the calibration state of a CD test
set using a calibrated reference fibre. The CD test set calibration compensation is explained
more fully in annex D. It should be noted that use of a calibrated reference fibre alone is not
sufficient to ensure calibration of a CD test set.
It should also be noted that if a calibrated CD test set undergoes calibration compensation
using a calibrated reference fibre, the scope and extent of its calibration is limited to the
conditions used at the time of calibration compensation (i.e. wavelength, fibre type, loss regime,
etc.) Care should be exercised that test sets calibrated and compensated in this manner are
used only within the appropriate limits of their calibration extent. The adjustments required to
effect compensation on one set of wavelengths for one fibre type may increase the uncertainty
of measurement of other fibre types with different minimum dispersion wavelengths.

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61744  IEC:2000(E) – 7 –
CALIBRATION OF FIBRE OPTIC CHROMATIC
DISPERSION TEST SETS
1 Scope
This International Standard provides standard procedures for the calibration of optical fibre
chromatic dispersion (CD) test sets. It also provides procedures to perform calibration checking
on CD test sets whereby an extension to the test set calibration period may be obtained.
This standard is applicable to all types of CD test sets, with the exception that measurements
on multimode optical fibres are excluded.
The purpose of this standard 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
may be measured on many CD test sets, this standard will restrict discussion to single mode
fibre measurements only.
The purpose of the procedures outlined in this standard 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,
b) setting specifications of CD test sets,
c) extending the calibration period of an already calibrated CD test set.
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 normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this International Standard are encouraged to investigate the possibility
of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of IEC
and ISO maintain registers of currently valid International Standards.
IEC 60050(731):1991, International Electrotechnical Vocabulary (IEV) – Chapter 731: Optical
fibre communication
1)
IEC 60793-1-1:1995, Optical fibres – Part 1: Generic specification – Section 1: General
IEC 60825-1:1993, Safety of laser products – Part 1: Equipment classification, requirements
2)
and user’s guide
___________
1)
 A consolidated edition 1.1 exists (1999) that includes IEC 60793-1-1 (1995) and its amendment 1 (1998).

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– 8 – 61744  IEC:2001(E)
3)
IEC 62129, Calibration of optical spectrum analyzers
ISO 9000 (all parts), Quality management and quality assurance standards
ISO 10012-1:1992, Quality assurance requirements for measuring equipment – Part 1:
Metrological confirmation system for measuring equipment
ISO 10012-2:1997, Quality assurance for measuring equipment – Part 2: Guidelines for control
of measurement processes
Guide to the Expression of Uncertainty in Measurement, 1993, ISO, ISBN 02-67-10188-9
EN 45001:1989, General criteria for the operation of testing laboratories
3 Terms and definitions
For the purpose of this International Standard, IEC 60050(731) and the following definitions
apply.
3.1
accredited calibration laboratory
calibration laboratory authorized by the appropriate national standards laboratory to issue
calibration certificates with a minimum specified uncertainty, which demonstrate traceability to
national standards
3.2
adjustment
modifying the hardware or firmware of a CD test set with the intention of making the
measurement result of the CD test set equal to that of a national standard or a similar
calibrated CD test set. This has the effect of correcting all subsequent measurements on that
CD test set
3.3
artefact
device, instrument or equipment used in the process of calibrating a CD test set, for both
wavelength and delay [dispersion]. The artefact is a means of transferring calibration of these
parameters to a CD test set
3.4
calibration
process by which the relationship between the values indicated by the infant CD test set and
known values of the calibration standard is established under specified conditions. The
intention of calibration is to bring all CD test sets into substantial agreement with a suitable
national standards laboratory. This may be performed by first comparing the relevant parameter
of a measurement artefact with that produced by the CD test set, followed by transfer of that
result, either by adjustment of the CD test set or by documentation of a calibration factor(s) in a
calibration certificate. The pertaining environmental conditions and instrument state are usually
recorded. Calibration includes estimation of all uncertainties. The use of reference fibres is for
calibration checking only

2)
 A consolidated edition 1.1 exists (1998) that includes IEC 60825-1 (1993) and its amendment 1 (1997).
3)
 To be published.

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61744  IEC:2000(E) – 9 –
3.5
calibration chain
unbroken chain of transfers from a primary standard to the CD test set via reference standards,
intermediate and/or working standards (see figure 1)
Uncertainty
National wavelength
and delay standard
Uncertainty of
reference
standard
Uncertainty of
Reference wavelength
Transfer
transfer
and delay standard
uncertainty
standard
Transfer
uncertainty
Uncertainty of
working
standard
Transfer wavelength
and delay standard
Transfer Uncertainty of
uncertainty CD test set at
reference
condition
Working wavelength
and delay standard
Transfer
Total
uncertainty
uncertainty of
CD test set
CD test set at
reference conditions
Operational
uncertainty
CD test set at
normal operating
conditions
IEC  2767/2000
Figure 1 – Typical calibration chain for CD test sets
3.6
calibration checking
process of establishing that a CD test set which has been previously calibrated, but is nearing
the end of its calibration period, remains within specified uncertainty limits. If the CD test set
has drifted outside these limits, then calibration is required. Otherwise, the calibration period
can be extended for a stated period, and calibration checking may be repeated indefinitely if the
CD test set remains stable over successive calibration periods. Calibration checking is
performed using a reference fibre or working standard. Essentially calibration checking is the
first part of the process of calibration, but without the additional process of transfer or
adjustment
3.7
calibration period
interval of confirmation
time period over which a calibration performed in accordance with the procedures in this
standard is deemed to remain within the uncertainty limits set. (i.e. remain valid). The time
allotted will be governed by individual user requirements, CD test set characteristics, past
experience, environmental conditions, etc. and by monitored CD test set measurement result
experience in normal use (see also ISO 10012-1 and ISO 10012-2)

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– 10 – 61744  IEC:2001(E)
3.8
calibration standard
artefact that is calibrated against a reference standard and is used to calibrate CD test sets.
The artefact may be a delay [dispersion] or a wavelength standard artefact. Proper use of the
calibration standard ensures traceability. The term includes the national standard, reference
...