EN 61744:2005

Calibration of fibre optic chromatic dispersion test sets

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.

Kalibrierung von Prüfaufbauten zur Bestimmung der chromatischen Dispersion

Etalonnage des ensembles d'essai de la dispersion chromatique des fibres optiques

La présente Norme Internationale fournit des procédures normalisées pour l'étalonnage des ensembles d'essai de la dispersion chromatique (CD) des fibres optiques. Elle fournit également des procédures pour réaliser la vérification de l'étalonnage sur des ensembles d'essai CD pour lesquels une prolongation de la période d'étalonnage de l'ensemble d'essai peut être obtenue.

Umerjanje pribora za preskušanje kromatične disperzije (IEC 61744:2005)

General Information

• Status: Published
• Publication Date: 21-Dec-2005
• Withdrawal Date: 31-Aug-2008
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: CLC/SR 86 - Fibre optics
• Drafting Committee: IEC/TC 86 - IEC_TC_86
• Parallel Committee: IEC/TC 86 - IEC_TC_86
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 22-Dec-2005
• Completion Date: 22-Dec-2005
• Ref Project: SIST EN 61744:2006 - Calibration of fibre optic chromatic dispersion test sets

Relations

• Replaced By: EN IEC 61744:2023 - Calibration of fibre optic chromatic dispersion test sets
• Effective Date: 25-Aug-2020
• Replaces: EN 61744:2001 - Calibration of fibre optic chromatic dispersion test sets
• Effective Date: 29-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61744:2006
01-marec-2006
1DGRPHãþD
SIST EN 61744:2004
8PHUMDQMHSULERUD]DSUHVNXãDQMHNURPDWLþQHGLVSHU]LMH,(&
Calibration of fibre optic chromatic dispersion test sets
Kalibrierung von Prüfaufbauten zur Bestimmung der chromatischen Dispersion

Etalonnage des ensembles d'essai de la dispersion chromatique des fibres optiques

Ta slovenski standard je istoveten z: EN 61744:2005
ICS:
33.140 Posebna merilna oprema za Special measuring
uporabo v telekomunikacijah equipment for use in
telecommunications
33.180.01 6LVWHPL]RSWLþQLPLYODNQLQD Fibre optic systems in
VSORãQR general
SIST EN 61744:2006 en

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

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SIST EN 61744:2006
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SIST EN 61744:2006
EUROPEAN STANDARD EN 61744
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2005
ICS 33.180.01 Supersedes EN 61744:2001
English version
Calibration of fibre optic chromatic dispersion test sets
(IEC 61744:2005)
Etalonnage des ensembles d'essai Kalibrierung von Prüfaufbauten
de la dispersion chromatique zur Bestimmung der chromatischen
des fibres optiques Dispersion
(CEI 61744:2005) (IEC 61744:2005)

This European Standard was approved by CENELEC on 2005-09-01. 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, Cyprus, Czech

Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, 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

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61744:2005 E
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SIST EN 61744:2006
EN 61744:2005 - 2 -
Foreword

The text of document 86/236/FDIS, future edition 2 of IEC 61744, prepared by IEC TC 86, Fibre

optics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as

EN 61744 on 2005-09-01.
This European Standard supersedes EN 61744:2001.

The principal change is the addition of reference to wavelength in vacuum. This reference is critical for

accurate production, measurement and sale of products in the emerging market applications of fibre

optics such as dense wavelength division multiplexing (DWDM) systems.
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) 2006-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-09-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 61744:2005 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 61315 NOTE Harmonized as EN 61315:1997 (not modified).
IEC 61746 NOTE Harmonized as EN 61746:2005 (not modified).
IEC 60793-1-1 NOTE Harmonized as EN 60793-1-1:2003 (not modified).
ISO 9000 NOTE Harmonized in the EN ISO 9000 series (not modified).
ISO 10012 NOTE Harmonized as EN ISO 10012 (not modified).
__________
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SIST EN 61744:2006
- 3 - EN 61744:2005
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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 Where 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 - International Electrotechnical Vocabulary - -
(IEV)
Chapter 731: Optical fibre communication
1) 2)
IEC 60825-1 - Safety of laser products EN 60825-1 1994
Part 1: Equipment classification, + corr. February 1995
requirements and user's guide
IEC 62129 - Calibration of optical spectrum analyzers- -
ISO 9000 Series Quality management and quality EN ISO 9000 Series
assurance standards
BIPM/IEC/IFCC/ 1995 Guide to the Expression of Uncertainty in - -
ISO/IUPAC/ Measurement (GUM)
IUPAP/OIML
1) 2)
ISO/IEC 17025 - General requirements for the competence EN ISO/IEC 2005
of testing and calibration laboratories 17025
Undated reference.
Valid edition at date of issue.
At draft stage.
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SIST EN 61744:2006
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SIST EN 61744:2006
NORME CEI
INTERNATIONALE
IEC
61744
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2005-09
Etalonnage des ensembles d'essai
de la dispersion chromatique
des fibres optiques
Calibration of fibre optic chromatic
dispersion test sets
 IEC 2005 Droits de reproduction réservés  Copyright - all rights reserved

Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any

utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including

électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from

microfilms, sans l'accord écrit de l'éditeur. the publisher.

International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland

Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch

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International Electrotechnical Commission
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Pour prix, voir catalogue en vigueur
For price, see current catalogue
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SIST EN 61744:2006
61744  IEC:2005 – 3 –
CONTENTS

FOREWORD...........................................................................................................................7

0 Introduction.....................................................................................................................11

0.1 Chromatic dispersion in optical fibres.....................................................................11

0.2 Chromatic dispersion (CD) test sets .......................................................................11

0.3 Overview of calibration procedures described in this standard ................................11

1 Scope .............................................................................................................................15

2 Normative references......................................................................................................15

3 Terms and definitions......................................................................................................17

4 Calibration ......................................................................................................................29

4.1 Rationale for calibration of CD test sets .................................................................29

4.2 Preparation for calibration......................................................................................33

4.3 Calibration procedure.............................................................................................35

4.4 Calibration checking procedure ..............................................................................37

5 Wavelength calibration procedure ...................................................................................37

5.1 General .................................................................................................................37

5.2 Discrete sources....................................................................................................39

5.3 Tunable sources ....................................................................................................39

5.4 Uncertainties and reporting ....................................................................................45

6 Delay [dispersion] calibration procedure ..........................................................................45

6.1 General .................................................................................................................45

6.2 Equipment and preparation ....................................................................................45

6.3 Calibration procedure.............................................................................................49

6.4 Uncertainties and reporting ....................................................................................51

7 Calibration checking procedure .......................................................................................51

7.1 General .................................................................................................................51

7.2 Equipment and preparation ....................................................................................53

7.3 Procedure..............................................................................................................53

7.4 Uncertainties and reporting ....................................................................................55

7.5 Generation of infant reference fibre........................................................................55

8 Documentation................................................................................................................57

8.1 Specifications, measurement data and uncertainties ..............................................57

8.2 Traceability information..........................................................................................59

Annex A (normative) Mathematical basis ..............................................................................61

Annex B (normative) Assessment of operational uncertainties ..............................................71

Annex C (informative) Chromatic dispersion .........................................................................87

Annex D (informative) CD test set calibration compensation .................................................95

Annex E (informative) Vacuum and air wavelength..............................................................101

Bibliography ........................................................................................................................107

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SIST EN 61744:2006
61744  IEC:2005 – 5 –

Figure 1 – Typical calibration chain for CD test sets...............................................................19

Figure 2 – Typical optical delay line artefact for CD test set delay calibration .........................47

Figure 3 – Typical differential delay [dispersion] simulator for CD test set calibration..............49

Figure 4 – Reference fibre comparison ..................................................................................55

Figure 5 – Generation of a reference fibre .............................................................................55

Figure A.1 – Deviation and uncertainty type B, and how to replace both by an

appropriately larger uncertainty .............................................................................................65

Figure C.1 – Schematic diagram of a CD test set...................................................................89

Figure E.1 – Dispersion and air and vacuum wavelength......................................................103

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SIST EN 61744:2006
61744  IEC:2005 – 7 –
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

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 61744 has been prepared by IEC technical committee 86: Fibre

optics.

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

constitutes a technical revision. The principal change is the addition of reference to wavelength

in vacuum. This reference is critical for accurate production, measurement and sale of products

in the emerging market applications of fibre optics such as dense wavelength division

multiplexing (DWDM) systems.
The text of this standard is based on the following documents:
FDIS Report on voting
86/236/FDIS 86/240/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.
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SIST EN 61744:2006
61744  IEC:2005 – 9 –

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

The committee has decided that the contents of this publication will remain unchanged until the

maintenance result 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.
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SIST EN 61744:2006
61744  IEC:2005 – 11 –
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 C and

IEC 60793-1-1.
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 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’.
0.3 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.
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SIST EN 61744:2006
61744  IEC:2005 – 13 –

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.

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.

In this document, the reference medium for wavelength and the velocity of light is assumed to

be in normal air. However, since the velocity of light in air (or rather, the refractive index of air)

is dependent on barometric pressure, humidity and temperature, it is sometime advantageous

to reference the velocity of light in vacuum, and hence define the refractive index =1,0000000.

This leads to a slight shift in the wavelength scale of the order of 0,3 nm to 0,4 nm depending

on the wavelength value, between the so-called “wavelength in air” (as assumed in this

document) and the wavelength in vacuum, also called “vacuum wavelength”.

Vacuum wavelength is typically used where very accurate dispersion control is required such

as in long-haul or submarine fiber cable systems. CD test sets for measuring fibers used in

these applications are typically calibrated to vacuum wavelength, e.g. using a wavemeter, or by

mathematical correction of results obtained with an internal air wavelength calibration.

In order that the user be familiar with the conversion from air wavelength and the mathematical

corrections involved, an informative annex, Annex E, is provided.
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SIST EN 61744:2006
61744  IEC:2005 – 15 –
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 referenced documents are indispensable for the application 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

IEC 60825-1, Safety of laser products – Part 1: Equipment classification, requirements and

user’s guide
___________

A consolidated edition 1.2 exists (1998) that includes IEC 60825-1 (1993) and its Amendment 1 (1997) and

Amendment 2 (2001).
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SIST EN 61744:2006
61744  IEC:2005 – 17 –
IEC 62129, Calibration of optical spectrum analyzers
ISO 9000 (all parts), Quality management and quality assurance standards

BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OIML:1995, Guide to the Expression of Uncertainty in

Measurement (GUM)

ISO/IEC 17025, General requirements for the competence of testing and calibration

laboratories
3 Terms and definitions

For the purposes of this document, the terms and definitions contained in 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

NOTE 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.
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)
___________
To be published.
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SIST EN 61744:2006
61744  IEC:2005 – 19 –
National wavelength
Uncertainty
and delay standard
Uncertainty of
reference
standard
Uncertainty of
Reference wavelength Transfer
transfer
and delay standard uncertainty
standard
Transfer
Uncertainty of
uncertainty
working
standard
Transfer wavelength
and delay standard
Transfer
Uncertainty of
uncertainty
CD test set at
reference
Working wavelength
condition
and delay standard
Total
Transfer
uncertainty of
uncertainty
CD test set
CD test set at
reference conditions
Operational
uncertainty
CD test set at normal
operating conditions
IEC 1329/05
Figure 1 – Typical calibration chain for CD test sets
3.6
...