IEC 61757:2018

IEC 61757 ®
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic sensors – Generic specification

Capteurs à fibres optiques – Spécification générique

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IEC 61757 ®
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic sensors – Generic specification

Capteurs à fibres optiques – Spécification générique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.99 ISBN 978-2-8322-5303-8

– 2 – IEC 61757:2018 © IEC 2018
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 10
4 Quality assurance . 17
5 Test and measurement procedures . 17
5.1 General . 17
5.2 Standard conditions for testing . 17
5.3 Test and measurement equipment requirements . 18
5.4 Visual inspection . 18
5.5 Dimensions . 18
5.6 Metrological properties. 18
5.6.1 General . 18
5.6.2 Metrological parameters . 19
5.7 Optical tests . 19
5.7.1 General . 19
5.7.2 Optical power . 19
5.7.3 Nominal wavelength and appropriate spectral characteristics . 19
5.7.4 State of polarization . 19
5.7.5 Fibre connector performance . 19
5.8 Electrical tests . 19
5.8.1 General . 19
5.8.2 Parameters and test procedures . 20
5.8.3 Voltage stress. 20
5.9 Mechanical tests . 20
5.9.1 General . 20
5.9.2 Parameters and test procedures . 20
5.10 Climatic and environmental tests . 21
5.10.1 General . 21
5.10.2 Parameters and test procedures . 21
5.11 Susceptibility to ambient light . 22
5.12 Resistance to solvents and contaminating fluids . 22
6 Classification . 22
6.1 General . 22
6.2 Measurand . 23
6.2.1 General . 23
6.2.2 Presence/absence of objects or features . 23
6.2.3 Position . 23
6.2.4 Rate of positional change . 23
6.2.5 Flow . 23
6.2.6 Temperature . 23
6.2.7 Force per directional vector . 23
6.2.8 Force per area . 24
6.2.9 Strain . 24
6.2.10 Electromagnetic quantities . 24

6.2.11 Ionizing and nuclear radiation . 24
6.2.12 Other physical properties of materials . 24
6.2.13 Composition and specific chemical quantities . 24
6.2.14 Particulates . 24
6.2.15 Imaging . 24
6.3 Transduction principle . 24
6.3.1 General . 24
6.3.2 Active generation of light . 24
6.3.3 Atom-field interaction . 24
6.3.4 Coherence modulation . 25
6.3.5 Intensity modulation . 25
6.3.6 Optical spectrum modulation . 25
6.3.7 Phase modulation . 25
6.3.8 Polarization modulation . 25
6.4 Spatial distribution . 25
6.5 Interface level . 25
7 Marking, labelling, packaging and instruction manual . 25
7.1 Marking of component . 25
7.2 Marking of sealed package and instruction manual . 26
8 IEC type designation . 26
9 Safety aspects . 26
9.1 General . 26
9.2 Personal safety . 26
9.3 Safety in explosive environment . 26
10 Ordering information . 26
11 Drawings . 26
Annex A (informative) Examples of fibre optic sensors . 27
A.1 General . 27
A.2 Presence/absence of objects or features. 27
A.2.1 Limit sensor (button, lever, key) . 27
A.2.2 Level . 27
A.2.3 Proximity . 27
A.2.4 Photo-interruption . 27
A.3 Position . 28
A.3.1 Linear position . 28
A.3.2 Angular position . 28
A.3.3 Proximity . 28
A.3.4 Zone (area) . 28
A.3.5 Dimensional . 28
A.4 Rate of positional change. 28
A.4.1 Linear speed or velocity . 28
A.4.2 Rotational speed or velocity . 28
A.4.3 Gyroscope . 29
A.4.4 Linear acceleration . 29
A.4.5 Rotational acceleration . 29
A.5 Flow . 29
A.6 Temperature . 29
A.7 Force per directional vector . 30

– 4 – IEC 61757:2018 © IEC 2018
A.7.1 Seismic. 30
A.7.2 Vibration . 30
A.7.3 Torque . 30
A.7.4 Weight . 30
A.8 Force per area . 30
A.8.1 Acoustic . 30
A.8.2 Pressure . 30
A.9 Strain . 31
A.10 Electromagnetic quantities . 32
A.10.1 Magnetic field . 32
A.10.2 Electrical current . 32
A.10.3 Electric field . 32
A.10.4 Voltage . 32
A.10.5 Electromagnetic radiation . 33
A.11 Ionizing and nuclear radiation . 33
A.12 Other physical properties of materials . 33
A.12.1 Material refractive index . 33
A.12.2 Density . 33
A.12.3 Viscosity . 33
A.12.4 Damage . 33
A.13 Composition and specific chemical quantities . 33
A.13.1 Chemical . 33
A.14 Particulates . 34
A.14.1 Count . 34
A.14.2 Atomic . 34
A.14.3 Turbidity . 34
A.15 Spatial distribution . 34
A.15.1 Single point . 34
A.15.2 Multiple point . 34
A.15.3 Integrating . 34
A.15.4 Distributed . 34
Bibliography . 35

Figure 1 – Fibre optic sensor configuration with a passive sensing element and
separate fibre leads for optical input and output . 12
Figure 2 – Fibre optic sensor configuration with an active sensing element and one
optical fibre lead for optical output . 12
Figure 3 – Fibre optic sensor configuration with a passive sensing element and one
fibre lead for optical input and output . 13

Table 1 – Electrical test parameters and procedures . 20
Table 2 – Mechanical test parameters and procedures. 21
Table 3 – Climatic and environmental test parameters and procedures . 22

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC SENSORS –
GENERIC SPECIFICATION
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
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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 61757 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
This first edition of IEC 61757 cancels and replaces IEC 61757-1, published in 2012. This
edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to
IEC 61757-1:2012:
a) change of the document number due to a new structure of the fibre optic standard series;
b) update of the normative references and bibliography;
c) revision of Annex A.
– 6 – IEC 61757:2018 © IEC 2018
The text of this International Standard is based on the following documents:
CDV Report on voting
86C/1461/CDV 86C/1488/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
INTRODUCTION
A fibre optic sensor contains an optical or optically powered sensing element in which the
information is created by reaction of light to a measurand. The sensing element can be the
fibre itself or an optically powered element inserted along the optical path. In a fibre optic
sensor, one or more light parameters are directly or indirectly modified by the measurand
somewhere in the optical path, contrary to an optical data link where the information is merely
transmitted from the transmitter to the receiver.
Generic tests or measurement methods for fibre optic sensors are defined in this document.
Where possible, these definitions are by reference to an IEC standard – otherwise the test or
measurement method is outlined in the relevant standard of the fibre optic sensor standard
series.
Annex A gives examples of fibre optic sensors to better illustrate the classification scheme.
The examples given are illustrative only and are not limitative, nor do they constitute a
recommendation or endorsement of a particular transduction principle.

– 8 – IEC 61757:2018 © IEC 2018
FIBRE OPTIC SENSORS –
GENERIC SPECIFICATION
1 Scope
This document is a generic specification covering optical fibres, components and sub-
assemblies as they pertain specifically to fibre optic sensing applications. It has been
designed to be used as a common working and discussion tool by the vendors of components
and subassemblies intended to be integrated in fibre optic sensors, as well as by designers,
manufacturers and users of fibre optic sensors independent of any application or installation.
The objective of this document is to define, classify and provide the framework for specifying
fibre optic sensors, and their specific components and subassemblies. The requirements of
this document apply to all related fibre optic sensor standards which belong to IEC 61757 (all
parts). Standards of IEC 61757 (all parts) contain requirements specific to sensors for
particular quantities subject to measurement, and for a particular style or variant of such a
fibre optic sensor.
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 (available at
www.electropedia.org)
IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60068-1, Environmental testing – Part 1: General and guidance
IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-5, Environmental testing – Part 2-5: Tests – Test Sa: Simulated solar radiation at
ground level and guidance for solar radiation testing
IEC 60068-2-6, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-10, Environmental testing – Part 2-10: Tests – Test J and guidance: Mould
growth
IEC 60068-2-11, Basic environmental testing procedures – Part 2-11: Tests – Test Ka: Salt
mist
IEC 60068-2-13, Basic environmental testing procedures – Part 2-13: Tests – Test M: Low air
pressure
IEC 60068-2-14, Environmental testing – Part 2-14: Tests – Test N: Change of temperature

IEC 60068-2-27, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60068-2-30, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic (12 h
+ 12 h cycle)
IEC 60068-2-42, Environmental testing – Part 2-42: Tests – Test Kc: Sulphur dioxide test for
contacts and connections
IEC 60068-2-43, Environmental testing – Part 2-43: Tests – Test Kd: Hydrogen sulphide test
for contacts and connections
IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady
state
IEC 60079-28, Explosive atmospheres – Part 28: Protection of equipment and transmission
systems using optical radiation
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60793-1-20, Optical fibres – Part 1-20: Measurement methods and test procedures –
Fibre geometry
IEC 60793-1-21, Optical fibres – Part 1-21: Measurement methods and test procedures –
Coating geometry
IEC 60793-1-31, Optical fibres – Part 1-31: Measurement methods and test procedures –
Tensile strength
IEC 60793-1-32, Optical fibres – Part 1-32: Measurement methods and test procedures –
Coating strippability
IEC 60793-1-47, Optical fibres – Part 1-47: Measurement methods and test procedures –
Macrobending loss
IEC 60793-1-54, Optical fibres – Part 1-54: Measurement methods and test procedures –
Gamma irradiation
IEC 60794-1-21, Optical fibre cables – Part 1-21: Generic specification – Basic optical cable
test procedures – Mechanical tests methods
IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements
IEC 60874-1, Fibre optic interconnecting devices and passive components – Connectors for
optical fibres and cables – Part 1: Generic specification
IEC 61000-4-2, Electromagnetic compatibility (EMC) – Part 4-2: Testing and measurement
techniques – Electrostatic discharge immunity test
IEC 61000-4-3, Electromagnetic compatibility (EMC) – Part 4-3: Testing and measurement
techniques – Radiated, radio-frequency, electromagnetic field immunity test
IEC 61000-4-4, Electromagnetic compatibility (EMC) – Part 4-4: Testing and measurement
techniques – Electrical fast transient/burst immunity test
IEC 61000-4-5, Electromagnetic compatibility (EMC) – Part 4-5: Testing and measurement
techniques – Surge immunity test

– 10 – IEC 61757:2018 © IEC 2018
IEC 61300 (all parts), Fibre optic interconnecting devices and passive components – Basic
test and measurement procedures
IEC 61300-2-1, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 2-1: Tests – Vibration (sinusoidal)
IEC 61300-2-9, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 2-9: Tests – Shock
IEC 61300-2-18, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 2-18: Tests – Dry heat – High temperature endurance
IEC 61300-2-22, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 2-22: Tests – Change of temperature
IEC 61300-2-34, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 2-34: Tests – Resistance to solvents and contaminating
fluids of interconnecting components and closures
IEC 61300-2-46, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 2-46: Tests – Damp heat, cyclic
IEC 61300-3-35, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-35: Examinations and measurements – Visual
inspection of fibre optic connectors and fibre-stub transceivers
IEC 61753 (all parts), Fibre optic interconnecting devices and passive components
performance standard
IEC TR 61931, Fibre optic – Terminology
IEC TR 62222, Fire performance of communication cables installed in buildings
IEC TR 62283, Optical fibres – Guidance for nuclear radiation tests
IEC TR 62627-01, Fibre optic interconnecting devices and passive components – Part 01:
Fibre optic connector cleaning methods
ISO/IEC Guide 99, International vocabulary of metrology – Basic and general concepts and
associated terms (VIM)
3 Terms and definitions
For the purpose of this document, the terms and definitions given in IEC TR 61931,
ISO/IEC Guide 99 (VIM), 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
3.1
accuracy
quality which characterizes the ability of a measuring instrument to
provide an indicated value close to a true value of the measurand

Note 1 to entry: This term is used in the "true value" approach. This is a value that would be obtained by a perfect
measurement.
Note 2 to entry: Accuracy is all the better when the indicated value is closer to the corresponding true value.
3.2
analogue signal interface
signal interface which provides analogue output signals in a form directly usable for control or
measurement purposes, and which is generally electrical
Note 1 to entry: Output schemes should preferably comply with existing interface standards such as those
existing for electrical analogue signals. Output schemes can be, for example, 4 mA to 20 mA, 0 mA to 20 mA, 0 V
to 5 V, etc. A fibre optic sensor with a photodetector or other square-law detector, or with integrated signal
processing electronics is a representative application example.
3.3
characteristic curve
calibration curve
expression of the relation between indication and corresponding measured quantity value
Note 1 to entry: A characteristic curve/calibration curve expresses a one-to-one relation that does not supply a
complete measurement result as it bears no information about the measurement uncertainty.
[SOURCE: ISO/IEC Guide 99:2007, 4.31, modified – The term "characteristic curve" has been
added as a first preferred term, as well as in the note.]
3.4
communication interface
digital interface of a fibre optic sensor which provides digital output signals in a form directly
usable for control or measurement purposes, or which enables digital communication with
other digital devices (e.g. personal computer)
Note 1 to entry: It is usually designed to a specific standard (e.g. USB, RS-232) and used for transmitting control
and measurement data.
3.5
distributed fibre optic sensor
fibre optic sensor which provides a spatially resolved measurement of a measurand over an
extended region by means of a continuous sensing element
3.6
drift
change in the metrological characteristics of a measuring instrument (and/or fibre optic
sensor), generally slow, continuous, not necessarily in the same direction and not related to a
change in the measurand
3.7
durability
ability of a fibre optic sensor to perform a required function under defined conditions of use
and maintenance, until a limiting state is reached
Note 1 to entry: A limiting state of an item may be characterized by the end of the useful life, unsuitability for any
economic or technological reasons or other relevant factors.
3.8
extrinsic fibre optic sensor
fibre optic sensor in which the characteristics of the light are affected externally to the optical
fibre(s) by the measurand
– 12 – IEC 61757:2018 © IEC 2018
3.9
fibre optic sensor
part of a measuring instrument, or measuring chain, which is directly affected by the
measurand and which generates a change in the optical characteristics of an optical fibre
related to the value of the measurand
Note 1 to entry: The optical fibre itself acts as the sensing element or it includes an optical or optically powered
sensing element and may include one or more of the following (see Figure 1, Figure 2, and Figure 3):
– optical fibre lead;
– signal conditioning.
Optical
Signal
interface
interface
Phenomenon
Sensing Optical
element receiver
Optical fibre lead(s)
Optical
Optical or optically
source
powered element
or sensitive fibre
Signal conditioning
IEC
Figure 1 – Fibre optic sensor configuration with a passive sensing element
and separate fibre leads for optical input and output
Optical Signal
interface interface
Phenomenon
Sensing
element
Optical
receiver
Optical fibre lead
Optical or optically
powered element
or sensitive fibre
Signal conditioning
IEC
Figure 2 – Fibre optic sensor configuration with an active sensing element
and one optical fibre lead for optical output

Signal
Optical
interface
interface
Phenomenon
Optical
Sensing
receiver
element
Y-Splitter
Optical fibre lead(s)
Optical
Optical or optically
source
powered element
or sensitive fibre
Signal conditioning
IEC
NOTE The signal separation is realized by a Y-splitter.
Figure 3 – Fibre optic sensor configuration with a passive sensing element
and one fibre lead for optical input and output
3.10
gauge length
measurement basis
length marked on the parallel portion of a measured object from which the elongation is
measured
Note 1 to entry: Used in mechanical testing of materials, it is the length marked on the parallel portion of a tensile
test piece from which the elongation is measured.
Note 2 to entry: For example, if the sensor is only anchored at two fixed points L cm apart, then the gauge length
is L. On the other hand, if a sensor of length l is continuously-fixed in or to a measured object of length L, then the
actual gauge length depends on the method of attachment to the measured object and is a function of the
mechanical properties of both the sensor and its surrounding; it is generally longer than l but shorter than L.
Note 3 to entry: If a user wants to achieve a pre-determined gauge length, he shall be very careful in selecting
the procedure by which the sensor is anchored/attached/embedded. In case of continuously-fixed sensors, the
fixing length shall exceed the defined gauge length by a few tens of fibre diameter to avoid shear-lag problems at
the edges. In the specific case of fracture or cracks within the gauge length of the sample, the final gauge length
shall be calculated then from the gauge length at fracture by subtracting from the latter the elastic portion of the
elongation.
3.11
influence quantity
quantity that, in a direct measurement, does not affect the quantity that is actually measured,
but affects the relation between the indication and the measurement result
[SOURCE: ISO/IEC Guide 99:2007, 2.52]
3.12
integrating fibre optic sensor
fibre optic sensor which provides a measurement result of a measurand over an extended
region by means of a continuous sensing element of a defined length
Note 1 to entry: The measurand is not spatially resolved but is integrated or summed over the length of the
sensing element.
3.13
intrinsic fibre optic sensor
fibre optic sensor whose sensing element consists of one or more optical fibre(s) in which one
or more characteristics like intensity, phase, polarization, spectrum, wavelength or transit time
of light depend on the measurand

– 14 – IEC 61757:2018 © IEC 2018
Note 1 to entry: There are a lot of fibre optic sensors where the sensing principle is based on a change in coating
characteristics only (e.g. chemical or RH sensors) or on an interaction between core and cladding (e.g. bending
sensor). They can be defined as indirect intrinsic fibre optic sensors. Direct intrinsic fibre optic sensors are defined
by a direct change of the fibre core characteristics (e.g. Brillouin, Raman or Rayleigh scattering based sensors).
3.14
instrumental measurement uncertainty
component of measurement uncertainty arising from a measuring instrument or measuring
system in use
Note 1 to entry: Instrumental measurement uncertainty is obtained through calibration of a measuring instrument
or measuring system, except for a primary measurement standard for which other means are used.
Note 2 to entry: Instrumental uncertainty is used in a Type B evaluation of measurement uncertainty according to
ISO/IEC Guide 98-3.
3.15
limiting operating condition
limiting values for operation
extreme operating condition that a measuring instrument or measuring system or a sensing
element (or a fibre optic sensor) is required to withstand without damage, and without
degradation of specified metrological properties, when it is subsequently operated under its
rated operating conditions
Note 1 to entry: Limiting conditions for storage, transport or operation can differ.
Note 2 to entry: Limiting conditions can include limiting values of a quantity being measured and of any influence
quantity.
Note 3 to entry: The limiting values can depend on the duration of their application.
[SOURCE: ISO/IEC Guide 99:2007, 4.10, modified – The second preferred term "limiting
va
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