SIST EN 61746-1:2011

SLOVENSKI STANDARD
SIST EN 61746-1:2011
01-maj-2011
1DGRPHãþD
SIST EN 61746:2005
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HQRURGQDYODNQD,(&
Calibration of Optical Time-Domain Reflectometers (OTDR) - Part 1: OTDR for single-
mode fibres (IEC 61746-1:2009)
Kalibrierung optischer Rückstreumessgeräte (OTDR) - Teil 1: OTDR für Einmodenfasern
(IEC 61746-1:2009)
Étalonnage des réflectomètres optiques dans le domaine temporel (OTDR) - Partie 1:
OTDR pour fibres unimodales (CEI 61746-1:2009)
Ta slovenski standard je istoveten z: EN 61746-1:2011
ICS:
17.180.30 2SWLþQLPHULOQLLQVWUXPHQWL Optical measuring
instruments
33.180.99 'UXJDRSUHPD]DRSWLþQD Other fibre optic equipment
YODNQD
SIST EN 61746-1:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61746-1:2011

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SIST EN 61746-1:2011

EUROPEAN STANDARD
EN 61746-1

NORME EUROPÉENNE
March 2011
EUROPÄISCHE NORM

ICS 33.180.01 Supersedes EN 61746:2005 (partially)


English version


Calibration of optical time-domain reflectometers (OTDR) -
Part 1: OTDR for single-mode fibres
(IEC 61746-1:2009)


Étalonnage des réflectomètres optiques Kalibrierung optischer
dans le domaine temporel (OTDR) - Rückstreumessgeräte (OTDR) -
Partie 1: OTDR pour fibres unimodales Teil 1: OTDR für Einmodenfasern
(CEI 61746-1:2009) (IEC 61746-1:2009)




This European Standard was approved by CENELEC on 2011-01-02. 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, 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, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

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

Management Centre: Avenue Marnix 17, B - 1000 Brussels


© 2011 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61746-1:2011 E

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SIST EN 61746-1:2011
EN 61746-1:2011 - 2 -
Foreword
The text of document 86/347/FDIS, future edition 1 of IEC 61746-1, prepared by IEC TC 86, Fibre optics,
was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61746-1 on
2011-01-02.
This European Standard partially supersedes EN 61746:2005.
The main technical changes to EN 61746:2005 are:
– the adaptation of Clause 4;
– the deletion of Clause 10;
– the adaptation of some definitions and calculations;
– the change of graphical symbology to IEC/TR 61930.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2011-10-02
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2014-01-02
with the EN have to be withdrawn
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61746-1:2009 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:
[2] IEC 60793-1-1 NOTE  Harmonized as EN 60793-1-1.
[3] IEC 60794-1-2:2003 NOTE  Harmonized as EN 60794-1-2:2003 (not modified).
[4] IEC 60825-1 NOTE  Harmonized as EN 60825-1.
[5] IEC 60825-2 NOTE  Harmonized as EN 60825-2.
[6] IEC 61280-1-3:1998 NOTE  Harmonized as EN 61280-1-3:1999 (not modified).
[7] IEC 61300-3-2 NOTE  Harmonized as EN 61300-3-2.
[8] IEC 61300-3-6 NOTE  Harmonized as EN 61300-3-6.
__________

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SIST EN 61746-1:2011
- 3 - EN 61746-1:2011
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  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

IEC 60793-1-40 - Optical fibres - EN 60793-1-40 -
(mod) Part 1-40: Measurement methods and test
procedures - Attenuation


IEC 60793-2-50 - Optical fibres - EN 60793-2-50 -
Part 2-50: Product specifications - Sectional
specification for class B single-mode fibres


ISO/IEC 17025 - General requirements for the competence of EN ISO/IEC 17025 -
testing and calibration laboratories


ITU-T 2004 Definitions and test methods for linear, - -
Recommendation deterministic attributes of single-mode fibre
G.650.1 and cable


ITU-T 2002 Definitions and test methods for statistical and - -
Recommendation non-linear related attributes of single-mode
G.650.2 fibre and cable

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SIST EN 61746-1:2011

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SIST EN 61746-1:2011
IEC 61746-1
®
Edition 1.0 2009-12
INTERNATIONAL
STANDARD


Calibration of optical time-domain reflectometers (OTDR) –
Part 1: OTDR for single mode fibres


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XC
ICS 33.180.01 ISBN 978-2-88910-553-3
® Registered trademark of the International Electrotechnical Commission

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SIST EN 61746-1:2011
– 2 – 61746-1 © IEC:2009(E)
CONTENTS
FOREWORD.6
INTRODUCTION.8
1 Scope.9
2 Normative references.9
3 Terms, definitions and symbols .9
4 Preparation for calibration.16
4.1 Organization .16
4.2 Traceability.16
4.3 Preparation.16
4.4 Test conditions .16
4.5 Documentation .16
5 Distance calibration – General .17
5.1 General .17
5.2 Location deviation model .17
5.3 Using the calibration results.19
5.4 Measuring fibre length .19
6 Distance calibration methods .20
6.1 General .20
6.2 External source method .20
6.2.1 Short description and advantage .20
6.2.2 Equipment .20
6.2.3 Calibration of the equipment .21
6.2.4 Measurement procedure .22
6.2.5 Calculations and results .23
6.2.6 Uncertainties .24
6.3 Concatenated fibre method.25
6.3.1 Short description and advantages .25
6.3.2 Equipment .25
6.3.3 Measurement procedures.27
6.3.4 Calculations and results .27
6.3.5 Uncertainties .28
6.4 Recirculating delay line method.29
6.4.1 Short description and advantage .29
6.4.2 Equipment .29
6.4.3 Measurement procedure .31
6.4.4 Calculations and results .31
6.4.5 Uncertainties .32
7 Loss calibration – General .33
7.1 General .33
7.2 Determination of the displayed power level F .33
7.3 Selection of an appropriate reference loss A .34
ref
7.4 Development of a test plan .35
7.5 Polarization dependence.37
7.6 Calculation of the calibration results.38
7.7 Using the calibration results.38
8 Loss calibration methods .38

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SIST EN 61746-1:2011
61746-1 © IEC:2009(E) – 3 –
8.1 General .38
8.2 Fibre standard method.39
8.2.1 Short description and advantage .39
8.2.2 Equipment .39
8.2.3 Measurement procedure .40
8.2.4 Calculations and results .41
8.2.5 Uncertainties .41
8.3 External source method (see Figure 16).42
8.3.1 Short description and advantage .42
8.3.2 Equipment .42
8.3.3 Calibration of the reference loss.43
8.3.4 Measurement procedure .44
8.3.5 Calculations and results .45
8.3.6 Uncertainties .45
8.4 Splice simulator method.46
8.4.1 Short description and advantage .46
8.4.2 Equipment .46
8.4.3 Procedure.47
8.4.4 Calculations and results .49
8.4.5 Uncertainties .49
8.5 Power reduction method .50
8.5.1 Short description and advantage .50
8.5.2 Equipment .51
8.5.3 Measurement procedure .52
8.5.4 Calculations and results .53
8.5.5 Uncertainties .53
9 Reflectance calibration.54
9.1 Objective .54
9.2 Reflectance measurements (see Figure 23) .54
9.3 Use of the backscatter parameter, K .54
9.4 Range of reflectance measurement.55
9.5 Development of a test plan .56
9.6 Equipment .57
9.7 Measurement procedure .58
9.7.1 Preparation.58
9.7.2 Taking reflectance measurements.58
9.7.3 Calculation and results.58
9.7.4 Uncertainties .58
Annex A (normative) Recirculating delay line for distance calibration .60
Annex B (normative) Optical fibre standard for loss calibration.64
Annex C (normative) Standard splice simulator for loss calibration.68
Annex D (normative) Mathematical basis.72
Annex E (normative)  Reflectance standard .75
Annex F (normative)  Simple version of reflectance standard.81
Annex G (informative)  OTDR basis: Backscatter theory – Reflectance measurements
using an OTDR – Determination of fibre backscatter parameter .85
Bibliography .90

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SIST EN 61746-1:2011
– 4 – 61746-1 © IEC:2009(E)
Figure 1 – Definition of attenuation dead zone .10
Figure 2 – Representation of the location deviation ΔL(L).18
Figure 3 – Equipment for calibration of the distance scale – External source method .21
Figure 4 – Set-up for calibrating the system insertion delay.22
Figure 5 – Concatenated fibres used for calibration of the distance scale.26
Figure 6 – Distance calibration with a recirculating delay line .30
Figure 7 – OTDR trace produced by recirculating delay line .30
Figure 8 – Determining the reference level and the displayed power level .34
Figure 9 – Measurement of the OTDR loss samples .35
Figure 10 – Region A, the recommended region for loss measurement samples .36
Figure 11 – Possible placement of sample points within region A .36
Figure 12 – External source method for testing the polarization dependence of the
OTDR .37
Figure 13 – Reflection method for testing the polarization dependence of the OTDR .37
Figure 14 – Loss calibration with a fibre standard .39
Figure 15 – Placing the beginning of section D outside the attenuation dead zone.40
1
Figure 16 – Loss calibration with the external source method.43
Figure 17 – Location and measurements for external source method .44
Figure 18 – Set-up for loss calibration with splice simulator .46
Figure 19 – OTDR display with splice simulator .47
Figure 20 – Measurement of the splice loss.48
Figure 21 – Loss calibration with "fibre-end" variant of the power reduction method .51
Figure 22 – Loss calibration with "long-fibre" variant of the power reduction method.52
Figure 23 – Parameters involved in reflectance measurements.54
Figure 24 – The same reflectance at the end of three fibres with different values of the
backscatter parameter shows different pulse amplitudes .55
Figure 25 – Maximum and minimum values for the pulse amplitude, ΔF .56
Figure 26 – Range of reflectance measurement.56
Figure 27 – Determining the default displayed power level and the default location .57
Figure 28 – Set-up for reflectance calibration.58
Figure A.1 – Recirculating delay line.60
Figure A.2 – Measurement set-up for loop transit time T .61
b
Figure A.3 – Calibration set-up for lead-in transit time T .62
a
Figure B.1 – Determination of a highly linear power range.65
Figure B.2 – Testing the longitudinal backscatter uniformity of the fibre standard .66
Figure C.1 – Splice simulator and idealized OTDR signature.68
Figure C.2 – Determination of the reference loss A .70
ref
Figure E.1 – Reflectance standard description and trace.75
Figure E.2 – Calibration set up and reference points for calibration.78
Figure F.1 – Reflectance standard description and trace.81
Figure F.2 – Calibration set up and reference points for calibration .83
Figure G.1 – OTDR signals used for determining reflectance .86
Figure G.2 – Set-up for measurement of the backscatter coefficient .88

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SIST EN 61746-1:2011
61746-1 © IEC:2009(E) – 5 –

Table 1 – Attenuation coefficients defining region A.35

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SIST EN 61746-1:2011
– 6 – 61746-1 © IEC:2009(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

CALIBRATION OF OPTICAL TIME-DOMAIN
REFLECTOMETERS (OTDR) –

Part 1: OTDR for single mode fibres


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,
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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
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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 61746-1 has been prepared by IEC technical committee 86: Fibre
optics.
This first edition of IEC 61746-1 cancels and replaces the second edition of IEC 61746,
published in 2005. It constitutes a technical revision.
The main technical changes are the adaptation of Clause 4, the suppression of Clause 10, the
improvement and the addition of some definitions, the change of some calculations and the
change of graphical symbology to IEC/TR 61930.

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SIST EN 61746-1:2011
61746-1 © IEC:2009(E) – 7 –
The text of this standard is based on the following documents:
FDIS Report on voting
86/347/FDIS 86/362/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 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.
A bilingual version of this standard may be issued at a later date.

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SIST EN 61746-1:2011
– 8 – 61746-1 © IEC:2009(E)
INTRODUCTION
In order for an Optical time-domain reflectometer (OTDR) to qualify as a candidate for
complete calibration using this standard, it must be equipped with the following minimum
feature set:
a) a programmable index of refraction, or equivalent parameter;
b) the ability to present a display of a trace representation, with a logarithmic power scale and
a linear distance scale;
c) two markers/cursors, which display the loss and distance between any two points on a trace
display;
d) the ability to measure absolute distance (location) from the OTDR's zero-distance reference;
e) the ability to measure the displayed power level relative to a reference level (for example,
the clipping level);
f) the ability to evaluate the reflectance of a reflective event.

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SIST EN 61746-1:2011
61746-1 © IEC:2009(E) – 9 –
CALIBRATION OF OPTICAL TIME-DOMAIN
REFLECTOMETERS (OTDR) –

Part 1: OTDR for single mode fibres



1 Scope
This part of IEC 61746 provides procedures for calibrating single-mode optical time domain
reflectometers (OTDR). It only covers OTDR measurement errors and uncertainties.
This standard does not cover correction of the OTDR response.
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 60793-1-40, Optical fibres – Part 1-40: Measurement methods and test procedures –
Attenuation
IEC 60793-2-50, Optical fibres – Part 2-50: Product specifications – Sectional specification for
class B single-mode fibres
ISO/IEC 17025, General requirements for the competence of testing and calibration
laboratories
ITU-T Recommendation G.650.1:2002, Definitions and test methods for linear, deterministic
attributes of single-mode fibre and cable
ITU-
...