EN 61746:2005

SLOVENSKI SIST EN 61746:2005
STANDARD
november 2005
Kalibriranje optične časovne domene reflektometrov (OTDR) (IEC 61746:2005)
Calibration of optical time-domain reflectometers (OTDR) (IEC 61746:2005)
ICS 17.180.30; 33.180.99 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 61746
NORME EUROPÉENNE
EUROPÄISCHE NORM March 2005
ICS 33.180.01 Supersedes EN 61746:2001

English version
Calibration of optical time-domain reflectometers (OTDR)
(IEC 61746:2004)
Etalonnage des réflectomètres optiques Kalibirerung optischer
dans le domaine de temps (OTDR) Rückstreumessgeräte (OTDR)
(CEI 61746:2004) (IEC 61746:2004)

This European Standard was approved by CENELEC on 2005-02-01. 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 61746:2005 E
Foreword
The text of document 86/230/FDIS, future edition 2 of IEC 61746, prepared by IEC TC 86, Fibre
optics, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 61746 on 2005-02-01.
This European Standard supersedes EN 61746:2001.
Specific changes to EN 61746:2001 include the development of Clause 9, “Reflectance calibration”,
and the introduction of Annexes E, F and G.
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) 2005-11-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-02-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61746:2005 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 60825-1 NOTE Harmonized as EN 60825-1:1994 (not modified).
IEC 60825-2 NOTE Harmonized as EN 60825-2:2004 (not modified).
IEC 61300-3-6 NOTE Harmonized as EN 61300-3-6:2003 (not modified).
__________
- 3 - EN 61746:2005
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 60793-1 Series Optical fibres EN 60793-1 Series
Part 1: Measurement methods and test
procedures
1) 2)
IEC 60793-1-40 - Optical fibres EN 60793-1-40 2003
(mod) Part 1-40: Measurement methods and
test procedures – Attenuation
1) 2)
IEC 60794-1-2 - Optical fibre cables EN 60794-1-2 2003
Part 1-2: Generic specification - Basic
optical cable test procedures
1) 2)
IEC 61300-3-2 - Fibre optic interconnecting devices and EN 61300-3-2 1999
passive components - Basic tests and
measurement procedures
Part 3-2: Examinations and
measurements - Polarization dependence
of attenuation in a single-mode fibre optic
device
ITU-T 2004 Definitions and test methods for linear, - -
Recommendation deterministic attributes of single-mode
G.650.1 fibre and cable
ITU-T 2002 Definitions and test methods for statistical - -
Recommendation and non-linear attributes of single-mode
G.650.2 fibre and cable
1)
Undated reference.
2)
Valid edition at date of issue.

NORME CEI
INTERNATIONALE IEC
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2005-01
Etalonnage des réflectomètres optiques
dans le domaine de temps (OTDR)
Calibration of optical time-domain
reflectometers (OTDR)
© IEC 2005 Droits de reproduction réservés ⎯ Copyright - all rights reserved
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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.
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61746¤ IEC:2005 – 3 –
CONTENTS
FOREWORD . 9
1 Scope .13
2 Normative references .13
3 Terms, definitions and symbols.15
4 Calibration test requirements .27
4.1 Preparation .27
4.2 Test conditions .27
4.3 Traceability .29
5 Distance calibration – General .29
5.1 Location error model.29
5.2 Using the calibration results.33
5.3 Measuring fibre length .33
6 Distance calibration methods .35
6.1 External source method .35
6.2 Concatenated fibre method.45
6.3 Recirculating delay line method .53
7 Loss calibration – General .63
7.1 Determination of the displayed power level F .63
7.2 Selection of an appropriate reference loss A .65
ref
7.3 Development of a test plan .65
7.4 Polarization dependence .69
7.5 Calculation of the calibration results .71
7.6 Using the calibration results.73
8 Loss calibration methods .73
8.1 Loss calibration with fibre standard.73
8.2 External source method (see Figure 16).81
8.3 Splice simulator method .89
8.4 Power reduction method .97
9 Reflectance calibration .105
9.1 Reflectance measurements (see Figure 23) .105
9.2 Use of the backscatter parameter, K .107
9.3 Range of reflectance measurement.109
9.4 Development of a test plan .111
9.5 Equipment .113
9.6 Measurement procedure .115
10 Documentation .117
10.1 Measurement data and uncertainties .117
10.2 Test conditions .119
Annex A (normative) Recirculating delay line for distance calibration.121
Annex B (normative) Optical fibre standard for loss calibration .129
Annex C (normative) Standard splice simulator for loss calibration .137
Annex D (informative) Mathematical basis.147

61746¤ IEC:2005 – 5 –
Annex E (normative) Reflectance standard.155
Annex F (normative)  Simple version of reflectance standard.169
Annex G (informative)  OTDR basis: Backscatter theory – Reflectance measurements
using an OTDR – Determination of fibre backscatter parameter.177
Bibliography .189
Figure 1 – Definition of attenuation dead zone .15
Figure 2 – Representation of the location error ∆L(L) .31
Figure 3 – Equipment for calibration of the distance scale – External source method .37
Figure 4 – Set-up for calibrating the system insertion delay .39
Figure 5 – Concatenated fibres used for calibration of the distance scale .47
Figure 6 – Distance calibration with a recirculating delay line .55
Figure 7 – OTDR trace produced by recirculating delay line .57
Figure 8 – Determining the reference level and the displayed power level.63
Figure 9 – Measurement of the OTDR loss samples .65
Figure 10 – Region A, the recommended region for loss measurement samples .67
Figure 11 – Possible placement of sample points within region A .69
Figure 12 – External source method for testing the polarization dependence of the OTDR .69
Figure 13 – Reflection method for testing the polarization dependence of the OTDR.71
Figure 14 – Loss calibration with a fibre standard.75
Figure 15 – Placing the beginning of section D outside the attenuation dead zone .77
Figure 16 – Loss calibration with the external source method .83
Figure 17 – Location and measurements for external source method .87
Figure 18 – Set-up for loss calibration with splice simulator.91
Figure 19 – OTDR display with splice simulator.91
Figure 20 – Measurement of the splice loss .93
Figure 21 – Loss calibration with "fibre-end" variant of the power reduction method.101
Figure 22 – Loss calibration with "long-fibre" variant of the power reduction method .101
Figure 23 – Parameters involved in reflectance measurements.107
Figure 24 – The same reflectance at the end of three fibres with different values of
the backscatter parameter shows different pulse amplitudes .109
Figure 25 – Maximum and minimum values for the pulse amplitude, ∆F .111
Figure 26 – Range of reflectance measurement .
...