SIST EN IEC 61757-5-1:2021

Fibre optic sensors - Part 5-1: Tilt measurement - Tilt sensors based on fibre Bragg gratings (IEC 61757-5-1:2021)

This part of IEC 61757 defines the terminology, structure, characteristics and their
measurement method including the procedures, for an optical tilt sensor based on fibre Bragg
gratings (FBGs) as the sensitive element.

Lichtwellenleitersensoren – Teil 5-1: Neigungsmessung - Neigungssensoren auf Basis von Faser-Bragg-Gittern (IEC 61757-5-1:2021)

Capteurs fibroniques - Partie 5-1: Mesure d’inclinaison - Capteurs d’inclinaison basés sur des réseaux de Bragg à fibres (IEC 61757-5-1:2021)

IEC 61757-5-1:2021 définit la terminologie, la structure, les caractéristiques et la méthode de mesure, incluant les procédures, d’un capteur d’inclinaison optique basé sur des réseaux de Bragg à fibres (FBG, fibre Bragg gratings) et utilisé comme élément sensible.

Optični senzorji - 5-1. del: Meritve nagiba - Nagibni senzorji na podlagi optovlakenskih Braggovih rešetk (IEC 61757-5-1:2021)

General Information

• Status: Published
• Publication Date: 07-Sep-2021
• ICS: 33.180.99 - Other fibre optic equipment
• Technical Committee: MOC - Mobile Communications
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 03-Sep-2021
• Due Date: 08-Nov-2021
• Completion Date: 08-Sep-2021
• Ref Project: EN IEC 61757-5-1:2021 - Fibre optic sensors - Part 5-1: Tilt measurement - Tilt sensors based on fibre Bragg gratings

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN IEC 61757-5-1:2021
01-november-2021
Optični senzorji - 5-1. del: Meritve nagiba - Nagibni senzorji na podlagi
optovlakenskih Braggovih rešetk (IEC 61757-5-1:2021)
Fibre optic sensors - Part 5-1: Tilt measurement - Tilt sensors based on fibre Bragg
gratings (IEC 61757-5-1:2021)
Lichtwellenleitersensoren – Teil 5-1: Neigungsmessung - Neigungssensoren auf Basis
von Faser-Bragg-Gittern (IEC 61757-5-1:2021)
Capteurs fibroniques - Partie 5-1: Mesure d’inclinaison - Capteurs d’inclinaison basés sur
des réseaux de Bragg à fibres (IEC 61757-5-1:2021)
Ta slovenski standard je istoveten z: EN IEC 61757-5-1:2021
ICS:
33.180.99 Druga oprema za optična Other fibre optic equipment
vlakna
SIST EN IEC 61757-5-1:2021 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 61757-5-1:2021

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SIST EN IEC 61757-5-1:2021


EUROPEAN STANDARD EN IEC 61757-5-1

NORME EUROPÉENNE

EUROPÄISCHE NORM
August 2021
ICS 33.180.99

English Version
Fibre optic sensors - Part 5-1: Tilt measurement - Tilt sensors
based on fibre Bragg gratings
(IEC 61757-5-1:2021)
Capteurs fibroniques - Partie 5-1: Mesure d'inclinaison - Lichtwellenleitersensoren - Teil 5-1: Neigungsmessung -
Capteurs d'inclinaison basés sur des réseaux de Bragg à Neigungssensoren auf Basis von Faser-Bragg-Gittern
fibres (IEC 61757-5-1:2021)
(IEC 61757-5-1:2021)
This European Standard was approved by CENELEC on 2021-08-11. 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 61757-5-1:2021 E

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SIST EN IEC 61757-5-1:2021
EN IEC 61757-5-1:2021 (E)
European foreword
The text of document 86C/1699/CDV, future edition 1 of IEC 61757-5-1, 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 61757-5-1:2021.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2022–05–11
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2024–08–11
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 61757-5-1:2021 was approved by CENELEC as a
European Standard without any modification.
2

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SIST EN IEC 61757-5-1:2021
EN IEC 61757-5-1:2021 (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 60068-2 series Environmental testing - Part 2X: Tests EN 60068-2 series
IEC 61300-2 series Fibre optic interconnecting devices and EN 61300-2 series
passive components - Basic test and
measurement procedures - Part 2X: Tests
IEC 61754 series Fibre optic interconnecting devices and EN 61754 series
passive components - Fibre optic
connector interfaces
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
IEC 62129-1 - Calibration of wavelength/optical frequency EN 62129-1 -
measurement instruments - Part 1: Optical
spectrum analyzers
IEC 62129-2 - Calibration of wavelength/optical frequency EN 62129-2 -
measurement instruments - Part 2:
Michelson interferometer single
wavelength meters
IEC 62129-3 - Calibration of wavelength/optical frequency EN IEC 62129-3 -
measurement instruments - Part 3:Optical
frequency meters internally referenced to a
frequency comb
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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IEC 61757-5-1

®


Edition 1.0 2021-07




INTERNATIONAL



STANDARD




NORME


INTERNATIONALE











Fibre optic sensors –

Part 5-1: Tilt measurement – Tilt sensors based on fibre Bragg gratings



Capteurs fibroniques –

Partie 5-1: Mesure d’inclinaison – Capteurs d’inclinaison basés sur des réseaux

de Bragg à fibres















INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE


INTERNATIONALE




ICS 33.180.99 ISBN 978-2-8322-9949-4




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 and definitions . 7
4 Symbols . 8
5 Structure and characteristics . 9
5.1 Fibre Bragg grating (FBG) . 9
5.2 FBG tilt sensor configuration . 9
5.3 Reference wavelength . 11
5.4 Stability behaviour . 11
5.4.1 Drift and creep . 11
5.4.2 Hysteresis . 12
5.5 Test specimen . 12
5.6 Indication of the measured values . 12
5.7 Zero point related measurement . 12
5.8 Non-zero point related measurement . 12
5.9 Production set . 12
5.10 FBG tilt sensor standard type . 13
5.11 FBG tilt sensor series . 13
6 Features and characteristics to be measured . 13
6.1 Sampling and statistical evaluation . 13
6.1.1 Sampling . 13
6.1.2 Reporting the measuring result . 13
6.1.3 Sample conditioning . 14
6.1.4 Ambient test conditions . 14
6.1.5 Required type of test for individual characteristics . 14
6.2 Bragg wavelength λ . 14
Β
6.2.1 General . 14
6.2.2 Measuring procedure . 15
6.2.3 Evaluation . 15
6.2.4 Reporting . 15
6.3 FBG spectral width. 15
6.3.1 Measuring procedure . 15
6.3.2 Evaluation . 15
6.3.3 Reporting . 15
6.4 FBG reflectivity . 16
6.4.1 Measuring procedure . 16
6.4.2 Evaluation . 16
6.4.3 Reporting . 16
6.5 Tilt measurement . 16
6.5.1 Test set-up . 16
6.5.2 Measuring procedure . 17
6.5.3 Calibration and evaluation . 18
6.6 Gauge factor κ . 19
θ
6.7 Temperature and humidity ranges . 19

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6.7.1 General . 19
6.7.2 Measuring procedure . 19
6.7.3 Evaluation . 20
6.7.4 Reporting . 20
7 Features and characteristics to be reported . 20
7.1 Construction details . 20
7.2 Configuration of the FBG tilt sensor . 20
7.3 Temperature and humidity range . 20
7.4 Connecting requirement . 20
8 Recommendations for use of FBG measuring instruments . 20


Figure 1 – Examples for measuring single axis tilt changes . 10
Figure 2 – Examples of Bragg wavelength change caused by tilt . 10
Figure 3 – Example of tilt sensor using FBG (schematic diagram) . 11
Figure 4 – Schematic diagram of tilt measurement system . 16
Figure 5 – Example of temperature dependence of the Bragg wavelengths of two
FBGs . 17
Figure 6 – Example of tilt dependence of the Bragg wavelengths of FBG1 and FBG2 . 18

Table 1 – Required type of test for individual characteristics . 14

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

FIBRE OPTIC SENSORS –

Part 5-1: Tilt measurement –
Tilt 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 61757-5-1 has been prepared by subcommittee 86C: Fibre optic systems and active
devices, of IEC technical committee TC86: Fibre optics. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
86C/1699/CDV 86C/1718/RVC

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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SIST EN IEC 61757-5-1:2021
IEC 61757-5-1:2021 © 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
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.

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FIBRE OPTIC SENSORS –

Part 5-1: Tilt measurement –
Tilt sensors based on fibre Bragg gratings



1 Scope
This part of IEC 61757 defines the terminology, structure, characteristics and their
measurement method including the procedures, for an optical tilt sensor based on fibre Bragg
gratings (FBGs) as the sensitive element.
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 60068-2 (all parts), Environmental testing – Part 2X: Tests
IEC 61300-2 (all parts), Fibre optic interconnecting devices and passive components – Basic
test and measurement procedures – Part 2X: Tests
IEC 61754 (all parts), Fibre optic interconnecting devices and passive components – Fibre
optic connector interfaces
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
IEC 62129-1, Calibration of wavelength/optical frequency measurement instruments – Part 1:
Optical spectrum analyzers
IEC 62129-2, Calibration of wavelength/optical frequency measurement instruments – Part 2:
Michelson interferometer single wavelength meters
IEC 62129-3, Calibration of wavelength/optical frequency measurement instruments – Part 3:
Optical frequency meters internally referenced to a frequency comb
ISO/IEC GUIDE 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61757,
IEC 61757-1-1, IEC 60050 (all parts) and the following apply.

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ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• ISO Online browsing platform: available at https://www.iso.org/obp
• IEC Electropedia: available at http://www.electropedia.org/
3.1
tilt
angle of rotation
for a point rotating around a fixed axis, quotient of the length travelled by the point, and the
distance from the point to the axis, taken positive or negative, according to whether the
rotation is observed to be in the counterclockwise sense or in the clockwise sense,
respectively, for an observer looking in the direction opposite to the direction of the axis
Note 1 to entry: Angle of rotation can take any real value, whereas the angle or plane angle defined in geometry
(see IEC 60050-102:2007, 102-04-14) is non-negative and restricted to the closed interval [0, π].
Note 2 to entry: The coherent SI unit of angle is radian (symbol rad). Other units accepted for use with the SI are
degree (symbol °), minute (symbol ′), and second (symbol ″): 1 ° = (π/180) rad, 1′ = (1/60) °, 1″ = (1/60)′.
[SOURCE: IEC 60050-113:2011, 113-01-43, modified – in the term, "oriented angle" has been
replaced with "tilt"]
3.2
FBG tilt sensor
fibre optic sensor that uses one or more fibre Bragg gratings as a sensitive element for tilt
measurements in either single axis or multiple axes
3.3
gauge factor
κ
θ
ratio of the relative change in wavelength Δλ/λ to a tilt change Δθ introduced to an FBG tilt
0
sensor and expressed by the gauge factor κ with a unit of 1/rad measured by the
θ
manufacturer, and expressed as:
Δλ

κ =
θ
λθΔ
0
Note 1 to entry: The gauge factor κ is used by manufacturers to express the tilt response of their products.
θ
Note 2 to entry: The gauge factor κ for an FBG tilt sensor assumes a linear characteristic. Considering the whole
θ
measurement system (sensor, device, cabling), it can be separately defined for the components of the
measurement system. It is only valid for defined conditions. In the case of a non-linear characteristic, the gauge
factor κ is considered as linear within a defined permissible error.
θ
3.4
temperature compensation constant
constant for correcting the influence of temperature changes when the tilt is obtained from the
wavelength changes
Note 1 to entry: The temperature compensation constant should be provided by the manufacturer.
4 Symbols
For the purposes of this document, the following symbols apply:
C temperature compensation constant
D displacement
Δθ tilt change

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ΔT temperature change
κ gauge factor
θ
L length
Λ FBG period
λ Bragg wavelength
B
λ reference wavelength
0
5 Structure and characteristics
5.1 Fibre Bragg grating (FBG)
Fibre Bragg gratings are phase diffraction gratings inscribed into optical waveguides. They
are frequently produced using ultraviolet (UV) light (e.g. by an excimer laser at 248 nm). The
fibre is exposed to an interference pattern of this UV radiation. UV photosensitive processes
then produce changes in the refractive index of the fibre core which is susceptible to these.
The interference pattern is an image in the fibre core of a periodically changing refractive
index. Incident and transported light along the fibre is additively superposed for a certain
wavelength at these points (constructive interference); this spectral part of the incident light is
reflected. In the transmitted light, this wavelength (denoted Bragg wavelength λ ) is
Β
attenuated according to FBG reflectivity.
The value of the reflected Bragg wavelength λ is determined from the Bragg condition:
Β
λΛ=2⋅⋅n (1)
B eff

According to Formula (1), the Bragg wavelength λ of the FBG depends on the effective
Β
refractive index of the FBG and the FBG period Λ. The spectral width of the Bragg wavelength
peak is essentially determined by the number of grating periods and the magnitude of the
refractive index modulation (see IEC 61757-1-1:2020, 5.1).
5.2 FBG tilt sensor configuration
The FBG tilt sensor can be made of various materials and with various forms as a segment of
optical fibre with one or more FBG sensors (in the following denoted Bragg grating fibre). The
FBG tilt sensor is capable of measuring both absolute and relative tilt, but it is more suitable
for tilt monitoring using relative tilt changes. The reference axis for absolute tilt measurements
is the vertical axis.
If the sensor is tilted in such a way that the tilt changes the tensile force applied to the FBG
sensor, the tilt can be measured by measuring the reflected Bragg wavelength of the FBG
(see Figure 1a) and Figure 1b)). In the example of Figure 1a), the tilt change causes a change
in torque due to the repositioning of the weight, which in turn causes a change in the tensile
force applied to the FBG, resulting in a change in the FBG reflected wavelength (see
Figure 2a), Figure 2b) and Figure 2c)). The method used to convert a tilt change into a
change of the Bragg wavelength is not part of this document and can be different depending
on the manufacturer.

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a) rotation type b) metal plate type

Figure 1 – Examples for measuring single axis tilt changes


a) no tilt b) clockwise tilt c) counterclockwise tilt

Figure 2 – Examples of Bragg wavelength change caused by tilt
A broadband source and a spectrometer are connected to the tilt sensing FBG by a circulator
as shown in Figure 3. An additional FBG (FBG1), placed in close proximity to the tilt sensing
FBG (FBG2), is used for temperature compensation, while FBG2 performs tilt measurements.
FBG1 and FBG2 can be connected in parallel or in series, as shown in Figure 3.

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Figure 3 – Example of tilt sensor using FBG (schematic diagram)
5.3 Reference wavelength
Different evaluation methods and different devices result in different Bragg wavelengths being
measured for the same filter function of the FBG. In the context of this document, therefore,
the result of the wavelength measurement after installation of the FBG tilt sensor with the
specified device will be denoted as the reference wavelength λ .
0
The reference wavelength is not necessarily the same as the Bragg wavelength specified by
the manufacturer of the FBG. If the FBG is prestrained, for example, there is a difference
between the reference wavelength and the Bragg wavelength. If the FBG is not prestrained,
the difference between the reference wavelength and the Bragg wavelength is usually very
small, so that both wavelength values can be used without significant error.
If the reference wavelength is measured when the measurement cycle is started, this
wavelength measurement can be considered as the zero point measuremen
...