IEC 60793-1-54:2012
(Main)Optical fibres - Part 1-54: Measurement methods and test procedures - Gamma irradiation
Optical fibres - Part 1-54: Measurement methods and test procedures - Gamma irradiation
IEC 60793-1-54:2012 outlines a method for measuring the steady state response of optical fibres and optical cables exposed to gamma radiation. It can be employed to determine the level of radiation induced attenuation produced in Class B single-mode or Class A, category A1 and A2 multimode optical fibres, in either cabled or uncabled form, due to exposure to gamma radiation. This second edition cancels and replaces the first edition, published in 2003. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: launching conditions and optical sources have been reviewed and are better defined. Keywords: gamma radiation, optical fibres, optical cables
Fibres optiques - Partie 1-54: Méthodes de mesure et procédures d'essai - Irradiation gamma
La CEI 60793-1-54:2012 présente une méthode de mesure de la réponse en régime permanent des fibres optiques et câbles optiques exposés au rayonnement gamma. Elle peut être utilisée pour déterminer le niveau d'affaiblissement induit par le rayonnement produit dans les fibres optiques unimodales de Classe B ou multimodales de Classe A, catégories A1 et A2, sous forme câblée ou non câblée, du fait d'une exposition au rayonnement gamma. Cette deuxième édition annule et remplace la première édition publiée en 2003. Elle constitue une révision technique. La présente édition contient les changements techniques significatifs suivants par rapport à l'édition précédente: les conditions d'injection et les sources optiques ont été revues et sont mieux définies. Mots clés: rayonnement gamma, fibres optiques, câbles optiques
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IEC 60793-1-54
®
Edition 2.0 2012-10
INTERNATIONAL
STANDARD
Optical fibres –
Part 1-54: Measurement methods and test procedures – Gamma irradiation
IEC 60793-1-54:2012(E)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2012 IEC, Geneva, Switzerland
All rights reserved. Unless otherwise specified, 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
either IEC or IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.
IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
Useful links:
IEC publications search - www.iec.ch/searchpub Electropedia - www.electropedia.org
The advanced search enables you to find IEC publications The world's leading online dictionary of electronic and
by a variety of criteria (reference number, text, technical electrical terms containing more than 30 000 terms and
committee,…). definitions in English and French, with equivalent terms in
It also gives information on projects, replaced and additional languages. Also known as the International
withdrawn publications. Electrotechnical Vocabulary (IEV) on-line.
IEC Just Published - webstore.iec.ch/justpublished Customer Service Centre - webstore.iec.ch/csc
Stay up to date on all new IEC publications. Just Published If you wish to give us your feedback on this publication
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also once a month by email. Customer Service Centre: csc@iec.ch.
---------------------- Page: 2 ----------------------
IEC 60793-1-54
®
Edition 2.0 2012-10
INTERNATIONAL
STANDARD
Optical fibres –
Part 1-54: Measurement methods and test procedures – Gamma irradiation
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
M
ICS 33.180.10 ISBN 978-2-83220-400-9
Warning! Make sure that you obtained this publication from an authorized distributor.
® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – 60793-1-54 © IEC:2012(E)
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Apparatus . 6
3.1 Radiation source . 6
3.1.1 Testing of environmental background radiation . 6
3.1.2 Testing of adverse nuclear environments . 6
3.2 Optical source . 6
3.3 Optical filters/monochromators . 6
3.4 Cladding mode stripper . 6
3.5 Fibre support and positioning apparatus . 6
3.6 Optical splitter . 6
3.7 Input launch conditions . 7
3.7.1 Class A, category A1 fibres (graded index multimode fibres) . 7
3.7.2 Class B fibres (single-mode fibres) . 7
3.7.3 Class A, category A2 fibres (quasi-step and step index fibres) . 7
3.8 Detector – Signal detection electronics . 7
3.9 Optical power meter . 7
3.10 Radiation dosimeter . 7
3.11 Temperature controlled container . 7
3.12 Test reel . 7
4 Sampling and specimens . 7
4.1 Specimens . 7
4.1.1 Fibre specimen . 7
4.1.2 Cable specimen . 8
4.2 Specimen for environmental background radiation test . 8
4.3 Specimen for testing adverse nuclear environments . 8
4.4 Test reel . 8
4.5 Ambient light shielding . 8
5 Procedure. 8
5.1 General . 8
5.2 Calibration of radiation source . 8
5.3 Preparation and pre-conditioning . 8
5.4 Attenuation measurement for environmental background radiation . 9
5.5 Attenuation measurement for adverse nuclear environment . 9
6 Calculations . 10
6.1 Change in optical attenuation ∆a (environmental background radiation test) . 10
6.2 Change in optical transmittance, a (adverse nuclear environmental radiation
test) . 10
6.3 Normalization of the results . 10
7 Results . 11
7.1 Information to be provided with each measurement . 11
7.2 Information available upon request . 11
8 Specification information . 11
Bibliography . 12
---------------------- Page: 4 ----------------------
60793-1-54 © IEC:2012(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-54: Measurement methods and test procedures –
Gamma irradiation
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 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
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 60793-1-54 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition, published in 2003. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– launching conditions and optical sources have been reviewed and are better defined.
---------------------- Page: 5 ----------------------
– 4 – 60793-1-54 © IEC:2012(E)
The text of this standard is based on the following documents:
CDV Report on voting
86A/1413/CDV 86A/1433/RVC
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.
A list of all parts of the IEC 60793 series can be found, under the general title Optical Fibres,
on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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 publication may be issued at a later date.
---------------------- Page: 6 ----------------------
60793-1-54 © IEC:2012(E) – 5 –
OPTICAL FIBRES –
Part 1-54: Measurement methods and test procedures –
Gamma irradiation
1 Scope
This part of IEC 60793 outlines a method for measuring the steady state response of optical
fibres and optical cables exposed to gamma radiation. It can be employed to determine the
level of radiation induced attenuation produced in Class B single-mode or Class A, category
A1 and A2 multimode optical fibres, in either cabled or uncabled form, due to exposure to
gamma radiation.
The attenuation of cabled and uncabled optical fibres generally increases when exposed to
gamma radiation. This is primarily due to the trapping of radiolytic electrons and holes at
defect sites in the glass (i.e. the formation of “colour centres”). This test procedure focuses on
two regimes of interest: the low dose rate regime suitable for estimating the effect of
environmental background radiation, and the high dose rate regime suitable for estimating the
effect of adverse nuclear environments. The testing of the effects of environmental
background radiation is achieved with an attenuation measurement approach similar to
IEC 60793-1-40 Method A, cut-back. The effects of adverse nuclear environments are tested
by monitoring the power before, during and after exposure of the test sample to gamma
radiation. The depopulation of colour centres by light (photo bleaching) or by heat causes
recovery (lessening of radiation induced attenuation). Recovery may occur over a wide range
of time which depends on the irradiation time and annealing temperature. This complicates
the characterization of radiation induced attenuation since the attenuation depends on many
variables including the temperature of the test environment, the configuration of the sample,
the total dose and the dose rate applied to the sample and the light level used to measure it.
This test is not a material test for the non-optical material components of a fibre optic cable. If
degradation of cable materials exposed to irradiation is to be studied, other test methods will
be required.
This test method is written to contain a clear, concise listing of instructions. The background
knowledge that is necessary to perform correct, relevant and expressive irradiation tests as
well as to limit measurement uncertainty is presented separately in IEC/TR 62283.
Attention is drawn to the fact that strict regulations and suitable protective facilities are to be
adopted in the laboratory for this test. Carefully selected trained personnel shall be used to
perform this test. It can be extremely hazardous to test personnel if it is improperly performed
or without qualified conditions.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. 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 60793-1-44, Optical fibres – Part
...
IEC 60793-1-54
®
Edition 2.0 2012-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical fibres –
Part 1-54: Measurement methods and test procedures – Gamma irradiation
Fibres optiques –
Partie 1-54: Méthodes de mesure et procédures d’essai – Irradiation gamma
IEC 60793-1-54:2012
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2012 IEC, Geneva, Switzerland
All rights reserved. Unless otherwise specified, 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
either IEC or IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et les
microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.
IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
Useful links:
IEC publications search - www.iec.ch/searchpub Electropedia - www.electropedia.org
The advanced search enables you to find IEC publications The world's leading online dictionary of electronic and
by a variety of criteria (reference number, text, technical electrical terms containing more than 30 000 terms and
committee,…). definitions in English and French, with equivalent terms in
It also gives information on projects, replaced and additional languages. Also known as the International
withdrawn publications. Electrotechnical Vocabulary (IEV) on-line.
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Stay up to date on all new IEC publications. Just Published If you wish to give us your feedback on this publication
details all new publications released. Available on-line and or need further assistance, please contact the
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A propos de la CEI
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contactez-nous: csc@iec.ch.
---------------------- Page: 2 ----------------------
IEC 60793-1-54
®
Edition 2.0 2012-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical fibres –
Part 1-54: Measurement methods and test procedures – Gamma irradiation
Fibres optiques –
Partie 1-54: Méthodes de mesure et procédures d’essai – Irradiation gamma
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX M
ICS 33.180.10 ISBN 978-2-8322-0930-1
Warning! Make sure that you obtained this publication from an authorized distributor.
Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – 60793-1-54 © IEC:2012
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Apparatus . 6
3.1 Radiation source . 6
3.1.1 Testing of environmental background radiation . 6
3.1.2 Testing of adverse nuclear environments . 6
3.2 Optical source . 6
3.3 Optical filters/monochromators . 6
3.4 Cladding mode stripper . 6
3.5 Fibre support and positioning apparatus . 6
3.6 Optical splitter . 6
3.7 Input launch conditions . 7
3.7.1 Class A, category A1 fibres (graded index multimode fibres) . 7
3.7.2 Class B fibres (single-mode fibres) . 7
3.7.3 Class A, category A2 fibres (quasi-step and step index fibres) . 7
3.8 Detector – Signal detection electronics . 7
3.9 Optical power meter . 7
3.10 Radiation dosimeter . 7
3.11 Temperature controlled container . 7
3.12 Test reel . 7
4 Sampling and specimens . 7
4.1 Specimens . 7
4.1.1 Fibre specimen . 7
4.1.2 Cable specimen . 8
4.2 Specimen for environmental background radiation test . 8
4.3 Specimen for testing adverse nuclear environments . 8
4.4 Test reel . 8
4.5 Ambient light shielding . 8
5 Procedure. 8
5.1 General . 8
5.2 Calibration of radiation source . 8
5.3 Preparation and pre-conditioning . 8
5.4 Attenuation measurement for environmental background radiation . 9
5.5 Attenuation measurement for adverse nuclear environment . 9
6 Calculations . 10
6.1 Change in optical attenuation Δa (environmental background radiation test) . 10
6.2 Change in optical transmittance, a (adverse nuclear environmental radiation
test) . 10
6.3 Normalization of the results . 10
7 Results . 11
7.1 Information to be provided with each measurement . 11
7.2 Information available upon request . 11
8 Specification information . 11
Bibliography . 12
---------------------- Page: 4 ----------------------
60793-1-54 © IEC:2012 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRES –
Part 1-54: Measurement methods and test procedures –
Gamma irradiation
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 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
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 60793-1-54 has been prepared by subcommittee 86A: Fibres and
cables, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition, published in 2003. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– launching conditions and optical sources have been reviewed and are better defined.
---------------------- Page: 5 ----------------------
– 4 – 60793-1-54 © IEC:2012
This bilingual version (2013-07) corresponds to the monolingual English version, published in
2012-10.
The text of this standard is based on the following documents:
CDV Report on voting
86A/1413/CDV 86A/1433/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 60793 series can be found, under the general title Optical Fibres,
on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
---------------------- Page: 6 ----------------------
60793-1-54 © IEC:2012 – 5 –
OPTICAL FIBRES –
Part 1-54: Measurement methods and test procedures –
Gamma irradiation
1 Scope
This part of IEC 60793 outlines a method for measuring the steady state response of optical
fibres and optical cables exposed to gamma radiation. It can be employed to determine the
level of radiation induced attenuation produced in Class B single-mode or Class A, category
A1 and A2 multimode optical fibres, in either cabled or uncabled form, due to exposure to
gamma radiation.
The attenuation of cabled and uncabled optical fibres generally increases when exposed to
gamma radiation. This is primarily due to the trapping of radiolytic electrons and holes at
defect sites in the glass (i.e. the formation of “colour centres”). This test procedure focuses on
two regimes of interest: the low dose rate regime suitable for estimating the effect of
environmental background radiation, and the high dose rate regime suitable for estimating the
effect of adverse nuclear environments. The testing of the effects of environmental
background radiation is achieved with an attenuation measurement approach similar to
IEC 60793-1-40 Method A, cut-back. The effects of adverse nuclear environments are tested
by monitoring the power before, during and after exposure of the test sample to gamma
radiation. The depopulation of colour centres by light (photo bleaching) or by heat causes
recovery (lessening of radiation induced attenuation). Recovery may occur over a wide range
of time which depends on the irradiation time and annealing temperature. This complicates
the characterization of radiation induced attenuation since the attenuation depends on many
variables including the temperature of the test environment, the configuration of the sample,
the total dose and the dose rate applied to the sample and the light level used to measure it.
This test is not a material test for the non-optical material components of a fibre optic cable. If
degradation of cable materials exposed to irradiation is to be studied, other test methods will
be required.
This test method is written to contain a clear, concise listing of instructions. The background
knowledge that is necessary to perform correct, relevant and expressive irradiation tests as
well as to limit measurement uncertainty is presented separately in IEC/TR 62283.
Attention is drawn to the fact that strict regulations and suitable protective facilities are to be
adopted in the laboratory for this test. Carefully selected trained personnel shall be used to
perform this test. It can be extremely hazardous to test personnel if it is improperly performed
or without qualified conditions.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. 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 60793-1-44, Optical fibres – Part 1-44: Measurement methods and test procedures –
Cut-off wavelength
---------------------- Page: 7 ----------------------
– 6 – 60793-1-54 © IEC:2012
IEC 60793-1-46, Optical fibres – Part 1-46: Measurement methods and test procedures –
Monitoring of changes in optical transmittance
IEC 61280-4-1, Fibre-optic communication subsystem test procedures – Part 4-1: Installed
cable plant – Multimode attenuation measurement
3 Apparatus
3.1 Radiation source
3.1.1 Testing of environmental background radiation
60
A Co or equivalent ionising source shall be used to deliver gamma radiation. This
environment is characterised by relatively low total dose and dose rate.
3.1.2 Testing of adverse nuclear environments
60
A Co or equivalent ionizing source(s) shall be used to deliver gamma radiation. This
environment is characterised by higher total dose and dose rate.
3.2 Optical source
An optical source such as a lamp, laser or light emitting diode emitting at wavelengths
compatible with the optical fibres under test shall be used.
The optical source shall be stable in intensity over a time period sufficient to perform the
measurement. The power coupled from the source into the test sample shall be < –30 dBm
(1,0 μW) or as specified in the detail specification. The optical source shall be modulated with
a pulsed signal at a 50 % duty cycle.
NOTE If a source that couples more than 1,0 μW is used, photo bleaching may occur.
3.3 Optical filters/monochromators
Unless otherwise specified, wavelength tolerances of ± 20 nm shall be obtained by filtering
the optical source with a set of optical filters or a monochromator. The 3 dB optical bandwidth
of the filters shall be less than or equal to 25 nm.
3.4 Cladding mode stripper
When necessary, a device that extracts cladding modes shall be employed at the input end
and output end of the test sample. If the fibre coating materials are designed to strip cladding
modes, a cladding mode stripper is not required.
3.5 Fibre support and positioning apparatus
A means of stable support for the input end of the test sample, such as a vacuum chuck, shall
be arranged. This support shall be mounted on a positioning device so that the end of the test
sample can be repeatedly positioned in the input beam.
3.6 Optical splitter
An optical splitter shall divert a small portion of the input light to a reference detector. The
reference path shall be used to monitor system fluctuations for the duration of the test.
---------------------- Page: 8 ----------------------
60793-1-54 © IEC:2012 – 7 –
3.7 Input launch conditions
3.7.1 Class A, category A1 fibres (graded index multimode fibres)
An equilibrium mode simulator shall be used to attenuate higher order propagation modes and
to establish a steady-state mode condition near the input end of the fibre. The requirements
for the launch conditions for sub-category A1a graded index multimode fibre measurements
are defined in IEC 61280-4-1.
3.7.2 Class B fibres (single-mode fibres)
An optical lens system or fibre pigtail may be employed to excite the test fibre. The power
coupled into the test sample shall be stable for the duration of the test. If an optical lens
system is used, a method of making the positioning of the fibre less sensitive is to overfill the
fibre end spatially and angularly. If a pigtail is used, it may be necessary to use index
matching material to eliminate interference effects. A high order mode filter shall be employed
to remove high order propagating modes in the wavelength range greater than or equal to the
cut-off wavelength of the test fibre. The test condition specified in IEC 60793-1-44, Method C
satisfies this requirement.
3.7.3 Class A, category A2 fibres (quasi-step and step index fibres)
Launch conditions shall be created as specified in the detail specification.
3.8 Detector – Signal detection electronics
An optical detector which is linear and stable over the range of intensities that are
encountered shall be used. A typical system might include a photovoltaic mode photodiode
amplified by a current input preamplifier, with synchronous detection by a lock-up amplifier.
3.9 Optical power meter
A suitable optical power meter shall be used to determine that the power coupled from the
optical source into the test sample is less than or equal to 1,0 μW or the level specified in the
detail specification.
3.10 Radiation dosimeter
Thermo luminescent LiF or CaF crystal detectors (TLDs) or an ion chamber detector shall be
used to measure the total radiation dose received by the specimen fibre.
3.11 Temperature controlled container
Unless otherwise specified, the temperature controlled container shall have the capability of
maintaining the specified temperatures to within ± 2 °C.
3.12 Test reel
The test reel shall not act as a shield or sink for the radiation used in this test. Reels of wood,
plastic or similar non-conducting materials would, in principle, act as transparent to the
radiation. The additional absorption shall be taken into account for exact measurements.
4 Sampling and specimens
4.1 Specimens
4.1.1 Fibre specimen
The test specimen shall be a representative sample of the fibre specified in the detail
specification.
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4.1.2 Cable specimen
The test specimen shall be a representative sample of the cable described in the detail
specification and shall contain at least one of the specified fibres.
4.2 Specimen for environmental background radiation test
Unless otherwise specified in the detail specification, the length of the test sample shall be
(3 000 ± 30) m. (Where reactor constraints dictate smaller lengths, the length of the test
sample may be (1 100 ± 20) m.) A minimum length at the ends of the test sample (typically
5 m) shall reside outside of the test chamber and be used to connect the optical source to the
detector. The irradiated length of the test sample shall be reported.
4.3 Specimen for testing adverse nuclear environments
Unless otherwise specified in the detail specification, the length of the test sample shall be
(250 ± 2,5) m. (When test conditions require a high total dose and dose rate a shorter test
sample length may be necessary). A minimum length at the ends of the test sample (typically
5 m) shall remain outside of the test chamber and be used to connect the optical source to the
detector. The irradiated length of the test sample shall be reported.
4.4 Test reel
The test sample shall be spooled onto a reel with a drum diameter that is specified in the
detail specification. Allowance shall be made for the unspooling of a measured length of the
test sample from each end of the reel to allow for attachment to the optical measurement
equipment. An alternative deployment method allows the fibre to be loosely wound in a coil of
specified diameter.
4.5 Ambient light shielding
The test sample shall be shielded from ambient light to prevent external photo bleaching.
5 Procedure
5.1 General
The radiation tests differ in exposure dose, dose rate, exposure time and temperature. The
tests are environmental background radiation test and adverse nuclear radiation test.
5.2 Calibration of radiation source
Calibration of the radiation source for dose uniformity and level shall be made prior to the test
sample being set up in the chamber. Four TLDs shall be placed in the area of exposure and
the centre of the TLDs shall be placed where the axis of the test reel will be placed. (Four
TLDs are used to get a representative average value.) A dose equal to or greater than the
actual test dose shall be used to calibrate the system. To maintain the highest possible
accuracy in measuring the test dose, the TLDs shall not be used more than once.
5.3 Preparation and pre-conditioning
The test sample shall be preconditioned in the temperature chamber at (25 ± 5) °C for 1 h
prior to testing, or at the test temperature for a preconditioned time as specified in the detail
specification.
The input end of the short test length shall be placed in the positioning device and aligned in
the test set to obtain maximum optical power as measured with a calibrated power meter.
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The power at the input end of the test sample shall be measured with a calibrated power
meter. If necessary, the source power level shall be adjusted so that the power at the input
end of the fibre is less than 1,0 μW or as specified in the detail specification.
NOTE If a source that couples more than 1,0 μW is used, photobleaching may occur.
With the radiation source off, the input end of the test sample shall be positioned to obtain
maximum optical power at the detector. Once set, the input launch conditions shall not be
changed during the gamma irradiation portion of the test.
A chart recorder or suitable continuous measurement device shall be connected to the
detection system so that a continuous power measurement can be made. The measurement
equipment shall be set up such that the detection signal does not exceed the limits of the
equipment.
60
A Co or equivalent ionizing source(s) shall be used to deliver gamma radiation at a desired
dose rate.
Dose rate levels are only approximate levels since the radiation source characteristics
change. A variation in dose rate as high as ± 50 % can be expected between sources. The
time required to turn the radiation source on or off shall be < 10 % of the total exposure time.
It is important that the temperature is kept constant during the tests. If the test should be
performed at different temperatures, then the attenuation prior to irradiation has to be
measured for different temperatures for each specified wavelength.
5.4 Attenuation measurement for environmental background radiation
An attenuation measurement of the test sample shall be performed, at the specified test
wavelengths, in accordance with IEC 60793-1-40, Method A, cut-back. The attenuation a of
1
the fibre prior to exposure to the gamma radiation source shall be recorded. The
environmental temperature shall be the same as during the up-coming irradiation tests when
the initial attenuation measurement is performed.
Environmental background radiation effects, d
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