SIST EN IEC 61757-2-1:2021
(Main)Fibre Optic Sensors - Part 2-1: Temperature measurement - Temperature sensors based on fibre Bragg gratings (IEC 61757-2-1:2021)
Fibre Optic Sensors - Part 2-1: Temperature measurement - Temperature sensors based on fibre Bragg gratings (IEC 61757-2-1:2021)
This part of IEC 61757 specifies the terminology, characteristic performance parameters and
related test methods of optical temperature sensors based on fibre Bragg gratings (FBG) that
carry out temperature measurements in the temperature range between –260 °C and 600 °C.
Generic specifications for fibre optic sensors are defined in IEC 61757.
Lichtwellenleitersensoren - Teil 2-1: Temperaturmessung - Temperatursensoren auf der Basis von Faser-Bragg-Gittern (IEC 61757-2-1:2021)
Capteurs fibroniques - Partie 2-1: Mesure de la température - Capteurs de température basés sur des réseaux de Bragg à fibres (IEC 61757-2-1:2021)
IEC 61757-2-1:2021 spécifie la terminologie, les paramètres de performance caractéristiques et les méthodes d’essai associées des capteurs de température optiques basés sur des réseaux de Bragg à fibres (FBG) qui réalisent des mesures de température dans la plage de températures comprise entre –260 °C et 600 °C. Les spécifications génériques applicables aux capteurs fibroniques sont définies dans l’IEC 61757.
Optični senzorji - 2-1. del: Merjenje temperature - Temperaturni senzorji na podlagi optovlakenskih Braggovih rešetk (IEC 61757-2-1:2021)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN IEC 61757-2-1:2021
01-november-2021
Optični senzorji - 2-1. del: Merjenje temperature - Temperaturni senzorji na podlagi
optovlakenskih Braggovih rešetk (IEC 61757-2-1:2021)
Fibre Optic Sensors - Part 2-1: Temperature measurement - Temperature sensors based
on fibre Bragg gratings (IEC 61757-2-1:2021)
Lichtwellenleitersensoren - Teil 2-1: Temperaturmessung - Temperatursensoren auf der
Basis von Faser-Bragg-Gittern (IEC 61757-2-1:2021)
Capteurs fibroniques - Partie 2-1: Mesure de la température - Capteurs de température
basés sur des réseaux de Bragg à fibres (IEC 61757-2-1:2021)
Ta slovenski standard je istoveten z: EN IEC 61757-2-1:2021
ICS:
17.200.20 Instrumenti za merjenje Temperature-measuring
temperature instruments
33.180.99 Druga oprema za optična Other fibre optic equipment
vlakna
SIST EN IEC 61757-2-1:2021 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN IEC 61757-2-1:2021
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SIST EN IEC 61757-2-1:2021
EUROPEAN STANDARD EN IEC 61757-2-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2021
ICS 33.180.99
English Version
Fibre optic sensors - Part 2-1: Temperature measurement -
Temperature sensors based on fibre Bragg gratings
(IEC 61757-2-1:2021)
Capteurs fibroniques - Partie 2-1: Mesure de la température Lichtwellenleitersensoren - Teil 2-1: Temperaturmessung -
- Capteurs de température basés sur des réseaux de Bragg Temperatursensoren auf der Basis von Faser-Bragg-Gittern
à fibres (IEC 61757-2-1:2021)
(IEC 61757-2-1:2021)
This European Standard was approved by CENELEC on 2021-09-01. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61757-2-1:2021 E
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EN IEC 61757-2-1:2021 (E)
European foreword
The text of document 86C/1725/FDIS, future edition 1 of IEC 61757-2-1, prepared by SC 86C “Fibre
optic systems and active devices” of IEC/TC 86 “Fibre optics” was submitted to the IEC-CENELEC
parallel vote and approved by CENELEC as EN IEC 61757-2-1:2021.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2022–06–01
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2024–09–01
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61757-2-1:2021 was approved by CENELEC as a
European Standard without any modification.
2
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EN IEC 61757-2-1:2021 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 1 Where an International Publication has been modified by common modifications, indicated by (mod), the
relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60050 (series) International Electrotechnical Vocabulary - -
(IEV)
IEC 61757 - Fibre optic sensors - Generic specification EN IEC 61757 -
IEC 61757-1-1 2020 Fibre optic sensors - Part 1–1: Strain EN IEC 61757-1-1 2020
measurement - Strain sensors based on
fibre Bragg gratings
ISO/IEC Guide 98-3 - Uncertainty of measurement - Part 3: - -
Guide to the expression of uncertainty in
measurement (GUM:1995)
3
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SIST EN IEC 61757-2-1:2021
IEC 61757-2-1
®
Edition 1.0 2021-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic sensors –
Part 2-1: Temperature measurement – Temperature sensors based on fibre
Bragg gratings
Capteurs fibroniques –
Partie 2-1: Mesure de la température – Capteurs de température basés
sur des réseaux de Bragg à fibres
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.99 ISBN 978-2-8322-1009-5
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
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CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, abbreviated terms and symbols of quantities . 7
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 11
3.3 Symbols of quantities . 12
4 Design and characteristics of an FBG temperature sensor . 13
4.1 Fibre Bragg grating (FBG) . 13
4.2 Dependence of Bragg wavelength on temperature . 13
4.3 Design features. 14
5 Performance parameters . 14
6 Test apparatuses for performance parameter determination . 15
6.1 Temperature calibration equipment . 15
6.2 Optical spectrum analyzer and interrogator . 16
6.3 Broadband light source . 16
7 Test procedures of performance parameters . 16
7.1 Sample preparation and test set-up . 16
7.2 Bragg wavelength λ . 17
Bref
7.2.1 Measuring procedure . 17
7.2.2 Evaluation . 18
7.2.3 Reporting . 18
7.3 FBG peak spectral width . 18
7.3.1 Measuring procedure . 18
7.3.2 Evaluation . 18
7.3.3 Reporting . 18
7.4 FBG reflectivity . 18
7.4.1 Measuring procedure . 18
7.4.2 Evaluation . 18
7.4.3 Reporting . 19
7.5 Side-lobe suppression ratio . 19
7.5.1 Measuring procedure . 19
7.5.2 Evaluation . 20
7.5.3 Reporting . 20
7.6 Signal-to-noise ratio . 21
7.6.1 Measuring procedure . 21
7.6.2 Evaluation . 21
7.6.3 Reporting . 21
7.7 Characteristic curve . 22
7.7.1 Measuring procedure . 22
7.7.2 Evaluation . 23
7.7.3 Reporting . 27
7.8 Thermal time constant. 28
7.8.1 Measuring procedure . 28
7.8.2 Evaluation . 28
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7.8.3 Reporting . 28
7.9 Sensor stability . 29
7.9.1 Measuring procedure . 29
7.9.2 Evaluation . 29
7.9.3 Reporting . 29
Annex A (informative) Blank detail specification . 30
A.1 General . 30
A.2 Mechanical and optical set-up . 30
A.3 Operational characteristics . 30
A.4 Limiting parameters . 31
A.5 Further information given upon request . 31
Annex B (informative) Examples of specific temperature calibration equipment . 32
B.1 Simple liquid bath . 32
B.2 Liquid tube-thermostat . 33
B.3 Solid-state calibration equipment . 34
Annex C (informative) Contributions to measurement uncertainty . 37
Bibliography . 38
Figure 1 – Principal test set-up for FBG . 17
Figure 2 – Determination of the FBG reflectivity from the reflection spectrum (left) and
transmission spectrum (right) . 19
Figure 3 – Side-lobes in the case of a single FBG temperature sensor . 20
Figure 4 – Signal-to-noise ratio determination . 21
Figure 5 – Example of a polynomial fit of calibration points λ (T ) . 24
B,i N,i
Figure 6 – Example of a third-order polynomial fit . 25
Figure 7 – Example of a fourth-order polynomial fit . 26
Figure 8 – Example of a polynomial fit of the sensitivity . 27
Figure 9 – Typical response time curve . 28
Figure B.1 – Schematic representation of a simple liquid bath [3] . 32
Figure B.2 – Schematic representation of liquid calibration device for connection to
laboratory liquid thermostats [4] . 33
Figure B.3 – Schematic representation of a long-tube fluid calibration device [3] . 34
Figure B.4 – Schematic representation of a solid-state calibration device for higher
temperatures [4] . 35
Figure B.5 – Schematic representation of a dry-block calibrator for calibrating an FBG
temperature sensor at higher temperatures . 36
Table 1 – Calibration bath fluids. 15
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC SENSORS –
Part 2-1: Temperature measurement –
Temperature sensors based on fibre Bragg gratings
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.
IEC 61757-2-1 has been prepared by subcommittee 86C: Fibre optic systems and active
devices, of IEC technical committee 86: Fibre optics. It is an International Standard.
The text of this International Standard is based on the following documents:
FDIS Report on voting
86C/1725/FDIS 86C/1737/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
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IEC 61757-2-1:2021 © IEC 2021 – 5 –
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types developed by
IEC are described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 61757 series, published under the general title Fibre optic
sensors, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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INTRODUCTION
This document is based on the guideline VDI/VDE 2660 Blatt 2:2020-04, Technical
temperature measurement – Optical temperature sensor based on fibre Bragg gratings –
Recommendation on temperature measurement and statement of measurement uncertainty
1
[1] . It was prepared in cooperation with VDI/VDE-GMA Technical Committee 2.17 "Fibre optic
measurement techniques".
The IEC 61757 series is published with the following logic: the sub-parts are numbered as
IEC 61757-M-T, where M denotes the measure and T, the technology.
___________
1
Numbers in square brackets refer to the Bibliography.
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FIBRE OPTIC SENSORS –
Part 2-1: Temperature measurement –
Temperature sensors based on fibre Bragg gratings
1 Scope
This part of IEC 61757 specifies the terminology, characteristic performance parameters and
related test methods of optical temperature sensors based on fibre Bragg gratings (FBG) that
carry out temperature measurements in the temperature range between –260 °C and 600 °C.
Generic specifications for fibre optic sensors are defined in IEC 61757.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 (all parts), International Electrotechnical Vocabulary (IEV) (available at
www.electropedia.org)
IEC 61757, Fibre optic sensors – Generic specification
IEC 61757-1-1:2020, Fibre optic sensors – Part 1-1: Strain measurement – Strain sensors
based on fibre Bragg gratings
ISO/IEC GUIDE 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)
3 Terms, definitions, abbreviated terms and symbols of quantities
For the purposes of this document, terms and definitions given in IEC 60050 (all parts),
IEC 61757, IEC 61757-1-1, and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
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3.1 Terms and definitions
3.1.1
Bragg wavelength under reference conditions
λ
Bref
wavelength of maximal reflectance or minimal transmittance of a mechanically stress-free
fibre Bragg grating at reference or standard temperature conditions, without the effect of a
temperature change
Note 1 to entry: The term Bragg wavelength λ specified in the data sheet of the manufacturer of a fibre Bragg
B
grating normally describes the Bragg wavelength without further details on reference or standard temperature
conditions.
[SOURCE: IEC 61757-1-1:2020, 3.3, modified – transformed to temperature sensing.]
3.1.2
birefringence
optical property of the directional dependence of the index of refraction of an optically
anisotropic material having orientation-dependent refractive indices that lead to different
propagation velocities of light in different propagation and polarization directions
Note 1 to entry: In fibre optic sensors terminology, the term "birefringence" is mainly applied when optical
waveguides with birefringence properties, such as PANDA or bow-tie fibres, are used. Birefringence in fibre Bragg
gratings becomes important only when polarized light is used for the measurement. Because of the properties of
fibre Bragg gratings, this can lead to an additional systematic increase in the measurement uncertainty.
[SOURCE: IEC 61757-1-1:2020,3.22, modified – clarified and Note modified.]
3.1.3
drift
shift of the characteristic curve (or, rarely, change of the characteristic curve parameters)
under the same measuring and operating conditions or reference conditions due to material
ageing or/and mechanical and/or thermal continuous or alternating stress
3.1.4
dynamic measurement deviation
ΔT(t)
time-dependent thermal measurement deviation resulting from time-varying differences
between the sensor temperature T (t) and the temperature of the medium T (t) with
S M
ΔTt T t− T t
() () ()
SM (1)
3.1.5
FBG peak
reflection peak or transmission minimum in the Bragg grating reflectance or transmittance
spectrum
Note 1 to entry: Maximum peak value is typically at the Bragg wavelength λ .
B
3.1.6
FBG peak spectral width
full width at half maximum (FWHM) of the FBG peak
Note 1 to entry: Full width at half maximum of the FBG peak is the wavelength range of the spectrum for which
the amplitude is greater than 50 % (3 dB).
[SOURCE: IEC 61757-1-1:2020, 3.7, modified – transformed for temperature sensor.]
=
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3.1.7
FBG period
Λ
distance between the periodically changing refractive index zones (grating planes) in an
optical waveguide having an effective refractive index n
eff
Note 1 to entry: The FBG period defines the Bragg wavelength λ through the formula
B
k⋅λ
B
Λ=
for k = positive integer
(2)
2 n
eff
[SOURCE: IEC 61757-1-1:2020, 3.18, modified – definition extended.]
3.1.8
FBG temperature sensor
fibre optic sensor that uses a fibre Bragg grating as a sensitive element for temperature
measurements
Note 1 to entry: FBG temperature sensors can be used in a series configuration with multiple gratings allowing to
perform distributed measurements.
3.1.9
FBG temperature sensing system
measurement set-up consisting of one or more serial arranged FBG temperature sensors
connected to an interrogation unit consisting of a light source, detector module, processor,
data archive, and user interface
Note 1 to entry: An FBG temperature sensing system normally works as follows: After light from the light source is
sent into the fibre and partially reflected or transmitted by the FBG temperature sensor, it is guided to the detector
module of the interrogator, which determines the FBG peak wavelength. From a shift of the FBG peak wavelength
caused by temperature change, the temperature change can be quantitatively determined in the measuring units.
3.1.10
maximum operating temperature
highest value of temperature at which the FBG temperature sensor meets the specified
performance
3.1.11
minimum operating temperature
lowest value of temperature at which the FBG temperature sensor meets the specified
performance
3.1.12
minimum bending radius
minimum radius at which an FBG temperature sensor is bent without change of the specified
performance parameters
Note 1 to entry: This value can differ from the minimum bending radius given for transport and storage.
[SOURCE: IEC 61757-1-1:2020, 3.16, modified – transformed for temperature sensor.]
3.1.13
parasitic strain effect
non-thermally induced deformation of the fibre Bragg grating during temperature
measurement resulting in a change in the wavelength response of the FBG
Note 1 to entry: A non-rateable deformation of the FBG during temperature measurement occurs as an apparent
temperature change in the response signal and shall therefore be excluded or be assessable.
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3.1.14
reference wavelength
λ
ref
wavelength response of a fibre Bragg grating to which a specific temperature T value is
ref
referred
Note 1 to entry: Depending on the evaluation method, the interrogator devices of the sensor often emit different
wavelengths to determine the filter function of the Bragg grating. The reference wavelength is not necessarily equal
to the Bragg wave
...
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