SIST EN 61746:2004
(Main)Calibration of optical time-domain reflectometers (OTDRs)
Calibration of optical time-domain reflectometers (OTDRs)
Provides procedures for calibrating single-mode optical time domain reflectometers (ODTRs). It only covers ODTR measurement errors and uncertainties. The ODTR must be equipped with a minimum feature set: programmable index of refraction, display of a trace representation, two cursors, absolute distance measurement, displayed power level relative to a reference level. It does not cover correction of the ODTR response.
Kalibrierung optischer Rückstreumessgeräte (OTDR)
Etalonnage des réflectomètres optiques dans le domaine de temps (OTDR)
Décrit des procédures destinées à l'étalonnage des réflectomètres optiques dans le domaine de temps pour fibres unimodales (ODTR). Elle ne traite que des erreurs et incertitudes de l'ODTR. Pour suivre la procédure dans cette norme, un ODTR sera au minimum équipé des fonctions spécifiques: un indice de réfraction programmable, l'affichage d'ume représentation graphique du signal, deux curseurs, mesurer la distance absolue, mesurer le niveau de puissance affiché par rapport une référence. Cette norme ne couvre pas la correction de la réponse de l'ODTR.
Kalibriranje optične časovne domene reflektometrov (OTDRji) (IEC 61746:2001)*
General Information
Relations
Standards Content (Sample)
EUROPEAN STANDARD EN 61746
NORME EUROPÉENNE
EUROPÄISCHE NORM November 2001
ICS 17.180.30;33.180.99
English version
Calibration of optical time-domain reflectometers (OTDRs)
(IEC 61746:2001)
Etalonnage des réflectomètres optiques Kalibrierung optischer
dans le domaine de temps (OTDR) Rückstreumessgeräte (OTDR)
(CEI 61746:2001) (IEC 61746:2001)
This European Standard was approved by CENELEC on 2001-10-01. 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, Malta, 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 61746:2001 E
---------------------- Page: 1 ----------------------
EN 61746:2001 - 2 -
Foreword
The text of document 86/175/FDIS, future edition 1 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 2001-10-01.
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) 2002-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-10-01
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, C and ZA are normative and annex D is informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61746:2001 was approved by CENELEC as a European
Standard without any modification.
__________
---------------------- Page: 2 ----------------------
- 3 - EN 61746:2001
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 60617-10 1996 Graphical symbols for diagrams EN 60617-10 1996
Part 10: Telecommunications:
Transmission
IEC 60793-1 Series Optical fibres --
Part 1: Generic specification
IEC 60794-1 Series Optical fibre cables EN 60794-1 Series
Part 1: Generic specification
IEC 60825-1 1993 Safety of laser products EN 60825-1 1994
Part 1: Equipment classification, + corr. February 1995
requirements and user's guide + A11 1996
A1 1997 - -
A2 2001 A2 2001
IEC 61300-3-2 1999 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
ISO 1993 International vocabulary of basic and--
general terms in metrology
ISO 1995 Guide to the expression of uncertainty--
in measurement
ITU-T 1997 Definition and test methods for the--
Recommendation relevant parameters of single-mode
G.650 fibres
---------------------- Page: 3 ----------------------
NORME CEI
INTERNATIONALE IEC
61746
INTERNATIONAL
Première édition
STANDARD
First edition
2001-09
Etalonnage des réflectomètres optiques
dans le domaine de temps (OTDR)
Calibration of optical time-domain
reflectometers (OTDRs)
© IEC 2001 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
utilisée sous quelque forme que ce soit et par aucun procédé, any form or by any means, electronic or mechanical,
électronique ou mécanique, y compris la photocopie et les including photocopying and microfilm, without permission in
microfilms, sans l'accord écrit de l'éditeur. 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
CODE PRIX
Commission Electrotechnique Internationale
XB
PRICE CODE
International Electrotechnical Commission
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 4 ----------------------
61746 © IEC:2001 – 3 –
CONTENTS
FOREWORD . 9
1 General. 11
1.1 Scope . 11
1.2 Normative references. 11
2 Definitions. 13
3 Calibration test requirements. 23
3.1 Preparation . 23
3.2 Test conditions. 23
3.3 Traceability . 23
4 Distance calibration – General. 25
4.1 Location error model . 25
4.2 Using the calibration results . 29
4.3 Measuring fibre length. 29
5 Distance calibration methods. 31
5.1 External source method . 31
5.1.1 Short description and advantage. 31
5.1.2 Equipment. 31
5.1.3 Measurement procedure. 35
5.1.4 Calculations and results . 37
5.1.5 Uncertainties. 37
5.2 Concatenated fibre method . 41
5.2.1 Short description and advantages. 41
5.2.2 Equipment. 41
5.2.3 Measurement procedures . 43
5.2.4 Calculations and results . 45
5.2.5 Uncertainties. 47
5.3 Recirculating delay line method . 49
5.3.1 Short description and advantage. 49
5.3.2 Equipment. 49
5.3.3 Measurement procedures . 51
5.3.4 Calculations and results . 53
5.3.5 Uncertainties. 53
6 Loss calibration – General. 57
6.1 Determination of the displayed power level F . 57
6.2 Selection of an appropriate reference loss A . 59
ref
6.3 Development of a test plan. 59
6.4 Polarization dependence . 63
6.5 Calculation of the calibration results . 65
6.6 Using the calibration results . 67
---------------------- Page: 5 ----------------------
61746 © IEC:2001 – 5 –
7 Loss calibration methods. 67
7.1 Loss calibration with fibre standard. 67
7.1.1 Short description and advantage. 67
7.1.2 Equipment. 67
7.1.3 Measurement procedure. 71
7.1.4 Calculations and results . 71
7.1.5 Uncertainties. 73
7.2 External source method . 75
7.2.1 Short description and advantage. 75
7.2.2 Equipment. 75
7.2.3 Measurement procedure. 77
7.2.4 Calculations and results . 79
7.2.5 Uncertainties. 81
7.3 Splice simulator method . 81
7.3.1 Short description and advantage. 81
7.3.2 Equipment. 83
7.3.3 Procedure . 85
7.3.4 Calculations and results . 87
7.3.5 Uncertainties. 89
7.4 Power reduction method. 89
7.4.1 Short description and advantage. 89
7.4.2 Equipment. 91
7.4.3 Measurement procedure. 95
7.4.4 Calculations and results . 95
7.4.5 Uncertainties. 95
8 Reflectance calibration . 97
9 Documentation. 97
9.1 Measurement data and uncertainties . 97
9.2 Test conditions. 99
Annex A (normative) Recirculating delay line for distance calibration. 101
A.1 Construction . 101
A.2 Calibration . 101
A.3 Uncertainties. 105
A.4 Documentation. 107
Annex B (normative) Optical fibre standard for loss calibration . 109
B.1 Fibre requirements. 109
B.2 Suitability check of the fibre. 109
B.3 Preparation and calibration of the fibre standard. 113
B.4 Recalibration of the optical fibre standard. 115
B.5 Uncertainty of the fibre standard. 115
B.6 Documentation. 115
Annex C (normative) Standard splice simulator for loss calibration . 117
C.1 Structure. 117
C.2 Preparation of the standard splice simulator . 119
C.3 Calibration procedure. 119
C.4 Uncertainties. 121
C.5 Documentation. 123
---------------------- Page: 6 ----------------------
61746 © IEC:2001 – 7 –
Annex D (informative) Mathematical basis . 125
D.1 Deviations. 125
D.2 Uncertainties type A . 125
D.3 Uncertainties type B . 127
D.4 Accumulation of uncertainties. 129
D.5 Reporting . 131
Figure 1 – Definition of attenuation dead zone. 13
Figure 2 – Representation of the location error ∆L(L) . 27
Figure 3 – Equipment for calibration of the distance scale – External source method. 31
Figure 4 – Set-up for calibrating the system insertion delay . 33
Figure 5 – Concatenated fibres used for calibration of the distance scale . 41
Figure 6 – Distance calibration with a recirculating delay line. 49
Figure 7 – OTDR trace produced by recirculating delay line. 51
Figure 8 – Determining the reference level and the displayed power level. 57
Figure 9 – Measurement of the OTDR loss samples. 59
Figure 10 – Region A, the recommended region for loss measurement samples. 61
Figure 11 – Possible placement of sample points within region A . 63
Figure 12 – External source method for testing the polarization dependence of the OTDR . 63
Figure 13 – Reflection method for testing the polarization dependence of the OTDR. 65
Figure 14 – Loss calibration with a fibre standard. 69
Figure 15 – Placing the beginning of section D outside the attenuation dead zone. 69
1
Figure 16 – Loss calibration with the external source method . 75
Figure 17 – Location and measurements for external source method. 79
Figure 18 – Set-up for loss calibration with splice simulator. 83
Figure 19 – OTDR display with splice simulator (the smaller circle represents the OTDR
response to the reference loss). 83
Figure 20 – Measurement of the splice loss . 85
Figure 21 – Loss calibration with "fibre-end" variant of the power reduction method. 93
Figure 22 – Loss calibration with "long-fibre" variant of the power reduction method . 93
Figure A.1 – Recirculating delay line . 101
Figure A.2 – Measurement set-up for loop transit time T . 103
b
Figure A.3 – Calibration set up for lead-in transit time T . 105
a
Figure B.1 – Determination of a highly linear power range . 111
Figure B.2 – Testing the longitudinal backscatter uniformity of the fibre standard. 113
Figure C.1 – Splice simulator and idealized OTDR signature . 117
Figure C.2 – Determination of the reference loss A . 121
ref
Figure D.1 – Deviation and uncertainty type B, and how to replace both
by an appropriately larger uncertainty. 127
Table 1 – Attenuation coefficients defining region A . 61
---------------------- Page: 7 ----------------------
61746 © IEC:2001 – 9 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CALIBRATION OF OPTICAL TIME-DOMAIN
REFLECTOMETERS (OTDRs)
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 61746 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
86/175/FDIS 86/177/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.
Annexes A, B and C form an integral part of this standard.
Annex D is 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.
---------------------- Page: 8 ----------------------
61746 © IEC:2001 – 11 –
CALIBRATION OF OPTICAL TIME-DOMAIN
REFLECTOMETERS (OTDRs)
1 General
1.1 Scope
This International Standard provides procedures for calibrating single-mode optical time
domain reflectometers (OTDRs). It only covers OTDR measurement errors and uncertainties.
This standard does not cover correction of the OTDR response.
In order for an OTDR to qualify as a candidate for complete calibration using this standard, it is
to 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).
1.2 Normative references
Les documents de référence suivants sont indispensables pour l'application du présent
document. Pour les références datées, seule l'édition citée s'applique. Pour les références non
datées, la dernière édition du document de référence s'applique (y compris les éventuels
amendements).
IEC 60050-731:1991, International Electrotechnical Vocabulary (IEV) – Chapter 731: Optical
fibre communication
IEC 60617-10:1996, Graphical symbols for diagrams – Part 10: Telecommunications –
Transmission
IEC 60793-1 (all parts), Optical fibres – Part 1: Generic specification
IEC 60794-1 (all parts), Optical fibre cables – Part 1: Generic specification
IEC 60825-1:1993, Safety of laser products – Part 1: Equipment classification, requirements
and user's guide
1)
Amendment 1 (1997)
Amendment 2 (2001)
IEC 61300-3-2:1999, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-2: Examinations and measurements – Polarization
dependence of attenuation in a single-mode fibre optic device
ISO:1993, International vocabulary of basic and general terms in metrology
ISO:1995, Guide to the expression of uncertainty in measurement
ITU-T Recommendation G.650:1997, Definition and test methods for the relevant parameters of
single-mode fibres
________
1)
There is a consolidated edition 1.1 (1998) that includes IEC 60825-1 (1993) and its amendment 1 (1997).
---------------------- Page: 9 ----------------------
61746 © IEC:2001 – 13 –
2 Definitions
For the purpose of this International Standard the definitions given below apply. For more
precise definitions, the references of IEC 60050-731 should be referred to.
2.1
attenuation, symbol A
optical power decrease in decibels (dB). If P (watts) is the power entering one end of a
in
segment of fibre and P (watts) is the power leaving the other end, then the attenuation of
out
the segment is
⎛ ⎞
P
in
A = 10 log ⎜ ⎟ dB (1)
10
⎜ ⎟
P
⎝ out ⎠
An alternative for "attenuation" is "loss"
[IEV 731-01-48, modified]
2.2
attenuation coefficient, symbol α
attenuation of a fibre per unit length
[IEV 731-03-42, modified]
2.3
attenuation dead zone
for a reflective or attenuating event, the region after the event where the displayed trace
deviates from the undisturbed backscatter trace by more than a given vertical distance ∆F
NOTE The attenuation dead zone will depend on the following event parameters: reflectance, loss, displayed
power level and location. It may also depend on any fibre optic component in front of the event.
Initial dead zone
∆F
Attenuation
dead zone
Location km
IEC 1421/01
Figure 1 – Definition of attenuation dead zone
2.4
calibration
set of operations which establish, under specified conditions, the relationship between the
values indicated by the measuring instrument and the corresponding known values of that
quantity (see ISO )
International vocabulary of basic and general terms in metrology
Displayed power F dB
---------------------- Page: 10 ----------------------
61746 © IEC:2001 – 15 –
2.5
centre wavelength, symbol λ
centre
power-weighted mean wavelength of a light source in vacuum, in nanometres (nm)
For a continuous spectrum, the centre wavelength is defined as:
1
λ = p(λ)λdλ (2)
centre
∫
P
total
For a spectrum consisting of discrete lines, the centre wavelength is defined as:
Pi i
∑
i
λ = (3)
centre
P
i
∑
i
where
p(λ) is the spectral power density of the source, for example in W/nm;
th
λ is the i discrete wavelength;
i
P is the power at λ , for example in watts;
i i
P = Σ P is the total power, for example in watts.
total i
The above integrals and summations extend over the entire spectrum of the light source.
2.6
confidence level
estimated probability that the true value of a measured quantity lies within a given expanded
uncertainty
NOTE In this standard, the confidence level is standardized to 95 %. See "expanded uncertainty" for further
clarification.
2.7
distance
spacing (actual or simulated) between two features in a fibre, for example in metres
2.8
distance sampling error
maximum distance error attributable to the distance between successive sample points,
specified in metres
NOTE The distance sampling error is repetitive in nature; therefore, one way of quantifying this error is by its
amplitude.
2.9
distance scale deviation, symbol ∆S
L
average error of the distance scale, that is difference between the average displayed distance
< D > and the correspondent reference distance D divided by the reference distance, for
otdr ref
example in m/m:
< D >− D < D >
otdr ref otdr
∆S = = − 1 (4)
L
D D
ref ref
where < D > is the displayed distance between two features on a fibre (actual or simulated)
otdr
averaged over at least one sample spacing
NOTE It is assumed that a relatively long distance, for example 2 000 m, is used in this formula.
---------------------- Page: 11 ----------------------
61746 © IEC:2001 – 17 –
2.10
distance scale factor, symbol S
L
average displayed distance divided by the correspondent reference distance:
< D >
otdr
S = (5)
L
D
ref
where < D > is the displayed distance between two features on a fibre (actual or simulated)
otdr
averaged over at least one sample spacing
NOTE It is assumed that relatively long distances are used in this formula.
2.11
distance scale uncertainty, symbol σ
∆SL
uncertainty of the distance scale deviation, for example in m/m
⎛ ⎞ ⎛ ⎞
< D > < D >
otdr otdr
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.