Fibre optic sensors - Part 3-1: Temperature measurement - Distributed sensing (IEC 61757-2-2:2016)

This part of IEC 61757 defines detail specifications for distributed temperature measurement
by a fibre optic sensor, also known as fibre optic distributed temperature sensing (DTS). DTS
includes the use of Raman scattering, Brillouin scattering and Rayleigh scattering effects. In
addition, Raman scattering and Rayleigh scattering based measurements are performed with
a single-ended fibre configuration only. Brillouin scattering based measurements are
performed with a single-ended fibre or fibre loop configuration. The technique accessible from
both sides at same time (e. g. Brillouin optical time domain analysis, BOTDA) is referred to
here as a loop configuration. Generic specifications for fibre optic sensors are defined in
IEC 61757-1:2012.
This part of IEC 61757 specifies the most important DTS performance parameters and defines
the procedures for their determination. In addition to the group of performance parameters, a
list of additional parameters has been defined to support the definition of the measurement
specifications and their associated test procedures. The definitions of these additional
parameters are provided for informational purposes and should be included with the sets of
performance parameters.
A general test setup is defined in which all parameters can be gathered through a set of tests.
The specific tests are described within the clause for each measurement parameter. This
general test setup is depicted and described in Clause 4 along with a list of general
information that should be documented based upon the specific DTS instrument and test
setup used to measure these parameters as per IEC 61757-2-2.
Annex A provides a blank performance parameter table which should be used to record the
performance parameter values for a given DTS instrument and chosen optical test setup
configuration.
Annex B provides guidelines for optional determination of point defect effects.

Lichtwellenleitersensoren - Teil 2-2: Temperaturmessung - Ortsaufgelöste faseroptische Messung

Capteurs fibroniques - Partie 2-2: Mesure de la température - Détections réparties

IEC 61757-2-2: 2016 définit les spécifications particulières de la mesure de température répartie par un capteur à fibres optiques, également connue sous l’appellation détection de température répartie (DTS) à fibres optiques. La DTS utilise les effets des diffusions de Raman, de Brillouin et de Rayleigh. De plus, les mesures basées sur une diffusion de Raman ou de Rayleigh sont uniquement effectuées avec une configuration à fibre unique. Les mesures basées sur une diffusion de Brillouin sont effectuées avec une configuration à fibre unique ou à boucle de fibre. La technique accessible simultanément des deux extrémités [par exemple Brillouin optical time domain analysis, BOTDA (analyse à capteurs à fibres optiques répartis utilisant la diffusion Brillouin dans le domaine temporel)] est appelée ici configuration à boucle. Les spécifications génériques applicables aux capteurs à fibres optiques sont définies dans l’IEC 61757-1:2012. La présente partie de l’IEC 61757 spécifie les paramètres de performance les plus importants de la DTS et définit les procédures pour leur détermination. En plus du groupe de paramètres de performance, une liste de paramètres supplémentaires a été définie pour venir à l’appui de la définition des spécifications de mesure et de leurs procédures d’essai associées. Les définitions de ces paramètres supplémentaires sont fournies à titre d’information et il convient de les inclure dans les ensembles de paramètres de performance. Un montage d’essai général est défini et permet d’obtenir tous les paramètres par un ensemble d’essais. Les essais spécifiques sont décrits dans l’article pour chaque paramètre de mesure. Ce montage d’essai général est décrit à l’Article 4, ainsi qu’une liste d’informations générales qu’il convient de consigner en fonction de l’instrument DTS spécifique et du montage d’essai utilisé pour mesurer ces paramètres, conformément à l’IEC 61757-2-2. L’Annexe A fournit un tableau de paramètres de performance vierge dans lequel il convient de consigner les valeurs des paramètres de performance d’un instrument DTS donné et de la configuration choisie pour le montage d’essais optiques. L’Annexe B fournit des lignes directrices pour la détermination facultative des effets des défauts ponctuels. Cette Norme internationale doit être utilisée conjointement avec l’IEC 61757-1:2012. La présente version bilingue (2020-09) correspond à la version anglaise monolingue publiée en 2016-05.

Optična zaznavala - 3-1. del: Merjenje temperature - Razpršeno zaznavanje (IEC 61757-2-2:2016)

Ta del standarda IEC 61757 določa podrobne specifikacije za razpršeno merjenje temperature z optičnim zaznavalom, znanim tudi kot optično razpršeno zaznavanje (DTS). Optično razpršeno zaznavanje vključuje uporabo učinkov Ramanovega sipanja, Brillouinovega sipanja in Rayleighovega sipanja, Poleg tega se meritve na podlagi Ramanovega in Rayleighovega sipanja izvajajo samo z enojno optično konfiguracijo. Meritve na podlagi Brillouinovega sipanja se izvajajo z enojno optično konfiguracijo ali konfiguracijo optične zanke. Tehnika, dostopna z obeh strani hkrati (npr. optična analiza BOTDA), se tukaj nanaša na konfiguracijo zanke. Splošne specifikacije za optična zaznavala so določene v standardu IEC 61757-1:2012.
Ta del standarda IEC 61757 določa najpomembnejše parametre delovanja DTS in opredeljuje postopke za njihovo določevanje. Poleg skupine parametrov delovanja je opredeljen tudi seznam dodatnih parametrov za pomoč pri definiciji specifikacij merjenja in njihovih povezanih preskusnih postopkov. Definicije teh dodatnih parametrov so podane samo za informativne namene in jih je treba vključiti v sklope parametrov delovanja.
Opredeljena je splošna postavitev za preskušanje, v kateri je mogoče vse parametre zbrati prek nabora preskusov.
Posebni preskusi do opisani v točki za vsak posamezen parameter. Ta splošna postavitev za preskušanje je prikazana in opisana v točki 4 poleg seznama splošnih informacij, ki jih je treba dokumentirati na podlagi posebnega instrumenta DTS in postavitve za preskušanje, uporabljene za merjenje teh parametrov v skladu s standardom IEC 61757-2-2.
Dodatek A vsebuje prazno preglednico s parametri delovanja, ki jo je treba uporabiti za beleženje vrednosti parametrov delovanja za dani instrument DTS in izbrano konfiguracijo optične postavitve preskušanja.
Dodatek B vsebuje smernice za izbirno določevanje točkovnih učinkov napak.

General Information

Status
Published
Publication Date
07-Nov-2017
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
13-Oct-2017
Due Date
18-Dec-2017
Completion Date
08-Nov-2017

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SLOVENSKI STANDARD
SIST EN 61757-2-2:2017
01-december-2017
2SWLþQD]D]QDYDODGHO0HUMHQMHWHPSHUDWXUH5D]SUãHQR]D]QDYDQMH ,(&


Fibre optic sensors - Part 3-1: Temperature measurement - Distributed sensing (IEC

61757-2-2:2016)
Ta slovenski standard je istoveten z: EN 61757-2-2:2017
ICS:
17.200.20 Instrumenti za merjenje Temperature-measuring
temperature instruments
33.180.99 'UXJDRSUHPD]DRSWLþQD Other fibre optic equipment
YODNQD
SIST EN 61757-2-2:2017 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61757-2-2:2017
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SIST EN 61757-2-2:2017
EUROPEAN STANDARD EN 61757-2-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2017
ICS 33.180.99
English Version
Fibre optic sensors -
Part 2-2: Temperature measurement -
Distributed sensing
(IEC 61757-2-2:2016)
Capteurs fibroniques - Lichtwellenleitersensoren -
Partie 2-2: Mesure de la température - Teil 2-2: Temperaturmessung -
Détections réparties Ortsaufgelöste faseroptische Messung
(IEC 61757-2-2:2016) (IEC 61757-2-2:2016)

This European Standard was approved by CENELEC on 2016-06-16. 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, 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: Avenue Marnix 17, B-1000 Brussels

© 2017 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 61757-2-2:2017 E
---------------------- Page: 3 ----------------------
SIST EN 61757-2-2:2017
EN 61757-2-2:2017
European foreword

The text of document 86C/1323/CDV, future edition 1 of IEC 61757-2-2, 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 61757-2-2:2017.
The following dates are fixed:
• latest date by which the document has to be implemented at (dop) 2018-04-06
national level by publication of an identical national
standard or by endorsement
• latest date by which the national standards conflicting with (dow) 2020-10-06
the document have to be withdrawn
This standard is to be read in conjunction with EN 61757-1:2012.

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.

Endorsement notice

The text of the International Standard IEC 61757-2-2:2016 was approved by CENELEC as a

European Standard without any modification.
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SIST EN 61757-2-2:2017
EN 61757-2-2:2017
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 When 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
IEC 61757-1 2012 Fibre optic sensors - Part 1: Generic EN 61757-1 2012
specification
IEC/TR 61931 - Fibre optic - Terminology - -
ISO/IEC Guide 99 - International vocabulary of metrology - - -
Basic and general concepts and
associated terms (VIM)
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SIST EN 61757-2-2:2017
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SIST EN 61757-2-2:2017
IEC 61757-2-2
Edition 1.0 2016-05
INTERNATIONAL
STANDARD
colour
inside
Fibre optic sensors –
Part 2-2: Temperature measurement – Distributed sensing
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.99 ISBN 978-2-8322-3363-4

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 7 ----------------------
SIST EN 61757-2-2:2017
– 2 – IEC 61757-2-2:2016 © IEC 2016
CONTENTS

FOREWORD ......................................................................................................................... 4

INTRODUCTION ................................................................................................................... 6

1 Scope ............................................................................................................................ 7

2 Normative references..................................................................................................... 7

3 Terms and definitions .................................................................................................... 8

4 General test setups for measurement of performance parameters ................................. 11

4.1 General and test setup requirements ................................................................... 11

4.2 General required information to be documented ................................................... 13

5 Measurement procedures for performance parameters ................................................. 14

5.1 Temperature measurement error ......................................................................... 14

5.1.1 Test procedure and conditions ...................................................................... 14

5.1.2 Parameter calculation .................................................................................. 14

5.2 Spatial resolution ................................................................................................ 16

5.2.1 Test procedure and conditions ...................................................................... 16

5.2.2 Parameter calculation .................................................................................. 17

5.3 Temperature repeatability .................................................................................... 17

5.3.1 Test procedure and conditions ...................................................................... 17

5.3.2 Parameter calculation .................................................................................. 18

5.3.3 Formulas ..................................................................................................... 19

5.4 Spatial temperature uncertainty ........................................................................... 19

5.4.1 Test procedure and conditions ...................................................................... 19

5.4.2 Parameter calculation .................................................................................. 19

5.5 Environmental temperature stability ..................................................................... 20

5.5.1 Test procedure and conditions ...................................................................... 20

5.5.2 Parameter calculation .................................................................................. 21

5.6 Warm-up time ..................................................................................................... 22

5.6.1 Test procedure and conditions ...................................................................... 22

5.6.2 Parameter calculation .................................................................................. 23

5.7 Attenuation range ................................................................................................ 24

5.7.1 Test procedure and conditions ...................................................................... 24

5.7.2 Parameter calculation .................................................................................. 25

Annex A (informative) Measurement parameter performance table ...................................... 26

Annex B (informative) Point defect effects ......................................................................... 28

B.1 General ............................................................................................................... 28

B.2 Point defect......................................................................................................... 28

B.3 Test procedures and conditions ........................................................................... 28

Bibliography ....................................................................................................................... 31

Figure 1 – Example of a temperature trace with temperature sample points.......................... 10

Figure 2 – General test setup: single-ended ........................................................................ 12

Figure 3 – General test setup: loop configuration ................................................................. 12

Figure 4 – Temperature measurement error calculation: step 1 ............................................ 15

Figure 5 – Temperature measurement error calculation: steps 2 through 3 ........................... 16

Figure 6 – Temperature measurement error calculation: steps 4 through 5 ........................... 16

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SIST EN 61757-2-2:2017
IEC 61757-2-2:2016 © IEC 2016 – 3 –

Figure 7 – Spatial resolution illustration ............................................................................... 17

Figure 8 – Temperature repeatability calculated from Figure 4 ............................................. 18

Figure 9 – Spatial temperature uncertainty calculated from Figure 4 .................................... 20

Figure 10 – Environmental temperature cycle (example for a DTS instrument with an

operating temperature range of 0 °C to 40 °C) ..................................................................... 21

Figure 11 – Environmental temperature stability parameter calculation method .................... 22

Figure 12 – Example illustrating calculation of warm-up time................................................ 23

Figure B.1 – Point defect measurement (example) ............................................................... 29

Table A.1 – Blank measurement parameter performance table ............................................. 26

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SIST EN 61757-2-2:2017
– 4 – IEC 61757-2-2:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC SENSORS –
Part 2-2: Temperature measurement – Distributed sensing
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 61757-2-2 has been prepared by subcommittee SC 86C: Fibre

optic systems and active devices of IEC technical committee 86: Fibre optics.
The text of this standard is based on the following documents:
CDV Report on voting
86C/1323/CDV 86C/1354/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 in the IEC 61757 series, published under the general title Fibre optic

sensors, can be found on the IEC website.
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SIST EN 61757-2-2:2017
IEC 61757-2-2:2016 © IEC 2016 – 5 –
This International Standard is to be used in conjunction with IEC 61757-1:2012.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC website 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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
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SIST EN 61757-2-2:2017
– 6 – IEC 61757-2-2:2016 © IEC 2016
INTRODUCTION

It has been decided to restructure the IEC 61757 series with the following logic. From now on,

the sub-parts will be renumbered as IEC 61757-M-T where M denotes the measure and T the

technology.

The existing part IEC 61757-1:2012 will be renumbered as IEC 61757 when it will be revised

and will serve as an umbrella document over the entire series.
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SIST EN 61757-2-2:2017
IEC 61757-2-2:2016 © IEC 2016 – 7 –
FIBRE OPTIC SENSORS –
Part 2-2: Temperature measurement – Distributed sensing
1 Scope

This part of IEC 61757 defines detail specifications for distributed temperature measurement

by a fibre optic sensor, also known as fibre optic distributed temperature sensing (DTS). DTS

includes the use of Raman scattering, Brillouin scattering and Rayleigh scattering effects. In

addition, Raman scattering and Rayleigh scattering based measurements are performed with

a single-ended fibre configuration only. Brillouin scattering based measurements are

performed with a single-ended fibre or fibre loop configuration. The technique accessible from

both sides at same time (e. g. Brillouin optical time domain analysis, BOTDA) is referred to

here as a loop configuration. Generic specifications for fibre optic sensors are defined in

IEC 61757-1:2012.

This part of IEC 61757 specifies the most important DTS performance parameters and defines

the procedures for their determination. In addition to the group of performance parameters, a

list of additional parameters has been defined to support the definition of the measurement

specifications and their associated test procedures. The definitions of these additional

parameters are provided for informational purposes and should be included with the sets of

performance parameters.

A general test setup is defined in which all parameters can be gathered through a set of tests.

The specific tests are described within the clause for each measurement parameter. This

general test setup is depicted and described in Clause 4 along with a list of general

information that should be documented based upon the specific DTS instrument and test

setup used to measure these parameters as per IEC 61757-2-2.

Annex A provides a blank performance parameter table which should be used to record the

performance parameter values for a given DTS instrument and chosen optical test setup

configuration.
Annex B provides guidelines for optional determination of point defect effects.
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 60050 (all parts), International Electrotechnical Vocabulary (available at
http://www.electropedia.org)
IEC 61757-1:2012, Fibre optic sensors – Part 1: Generic specification
IEC TR 61931, Fibre optic – Terminology

ISO/IEC Guide 99, International vocabulary of metrology – Basic and general concepts and

associated terms (VIM)
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SIST EN 61757-2-2:2017
– 8 – IEC 61757-2-2:2016 © IEC 2016
3 Terms and definitions

For the purposes of this document, the definitions given in IEC 61757-1:2012, IEC 60050,

IEC TR 61931, ISO/IEC Guide 99 (VIM), as well as the following apply.
3.1
attenuation range

total cumulated optical loss (one way loss) tolerated by the DTS system without affecting the

specified measurement performance more than a given factor at a given location, spatial

resolution, and measurement time

Note 1 to entry: Part of the total cumulative loss can be the fibre attenuation, point defect losses introduced by

components such as connectors, splices, kink in the fibre, attenuators.
Note 2 to entry: The attenuation range is expressed in decibels (dB).
3.2
distance measurement range

maximum distance from the DTS instrument output connector along the fibre optic sensor

within which the instrument measures a temperature with specified measurement performance

under defined conditions

Note 1 to entry: This supporting parameter is closely related to the attenuation range of the instrument. In test

cases used to prove or verify the reported specifications, the total fibre length shall be equal to or greater than the

specified distance measurement range.

Note 2 to entry: The distance measurement range is expressed in length units (m or km).

3.3
environmental temperature repeatability

difference of the measured constant fibre optic sensor temperature at a specified instrument

temperature (e. g. nominal operating temperature) before and after temperature cycling of the

instrument across the entire instrument operating temperature range

Note 1 to entry: This parameter is derived from environmental temperature stability.

3.4
environmental temperature stability

difference of the measured constant fibre optic sensor temperature before, during and after

temperature cycling of the DTS instrument across the entire instrument operating temperature

range

Note 1 to entry: Worst case environmental temperature effect, high/low environmental temperature effect, and

environmental temperature repeatability are derived from this definition.
3.5
high/low environmental temperature effect

difference of the measured constant fibre optic sensor temperature at the high and low

temperature limit of the instrument temperature operating range

Note 1 to entry: This parameter is derived from environmental temperature stability.

3.6
hot spot

length of fibre optic sensor (∆L) which is exposed by a measurable temperature change (∆T)

which is significantly bigger than the instrument temperature repeatability and which is

confirmed by reference temperature devices in the two thermal chambers.
Note 1 to entry: See Clause 4 and Figure 7.
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SIST EN 61757-2-2:2017
IEC 61757-2-2:2016 © IEC 2016 – 9 –
3.7
location

optical distance (specified in length units) from the DTS instrument output connector to a

desired temperature sample point along the fibre optic sensor

Note 1 to entry: The furthest location from DTS instrument output connector for the particular test is quantified as

Z m and is often chosen to be the same as the distance measurement range for purposes of comparing the

measurement results with quoted specifications.
3.8
measurement time
time between independent temperature measurements when making successive
measurements on a single fibre optic sensor

Note 1 to entry: This parameter includes acquisition time and processing time for measured data. This parameter

is selectable by the user typically in some limited fashion. Multiple independent temperature measurements may be

averaged together to provide an overall measurement time.

Note 2 to entry: Equivalently, it is the time interval between successive temperature trace timestamps under these

conditions.
3.9
point defect

local deviation of a fibre optic sensor from its nominal optical and mechanical properties

occurring at a single location, or over a length substantially less than the DTS spatial

resolution

Note 1 to entry: The definition of a point defect encompasses a wide range of situations, which may produce

similar effects on the temperature trace. Examples include
– a point loss, such as a bad fibre splice;
– a back reflection, such as may arise from a fibre connector;
– a localized region of high loss, such as a bend or kink in the fibre;

– a physical discontinuity in the fibre, such as a splice between two fibres of different core diameters.

3.10
point defect temperature offset

difference between the average values of the temperature sample points in two zones on the

temperature trace, one each side of a point defect, where the actual fibre optic sensor

temperatures are the same

Note 1 to entry: The point defect temperature offset may be positive, negative or zero.

3.11
sample spacing

distance between two consecutive temperature sample points in a single temperature trace

Note 1 to entry: See Figure 1.
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SIST EN 61757-2-2:2017
– 10 – IEC 61757-2-2:2016 © IEC 2016
Red dots represent Black line represents
temperature sample points
the actual temperature (unknown)
Sample
spacing
Location (m)
IEC
Figure 1 – Example of a temperature trace with temperature sample points
Note 2 to entry: Sample spacing may be a user-selectable instrument parameter.

Note 3 to entry: The distance measurement range is expressed in length units (in m).

Note 4 to entry: In case of very high spacing resolution, the distance measurement range can be expressed in cm

or mm.
3.12
spatial resolution

smallest length of a temperature-affected fibre optic sensor for which a DTS system can

measure the reference temperature of the hot spot fibre condition within the specified

temperature measurement error of the DTS system
3.13
spatial temperature uncertainty

uncertainty of location of temperature data in a single temperature trace expressed by twice

the standard deviation of a specified number of adjacent temperature sample points, with the

fibre optic sensor held at constant temperature
3.14
temperature dead zone

limited zone of a temperature trace, where the temperature sample points deviate from the

undisturbed parts of the trace by a specified limit due to a point defect
3.15
temperature measurement error

maximum difference between a centred and uniformly weighted moving average of the

measured temperature and a reference temperature for all data points of the fibre optic

sensor over the full operating temperature range and all acquisition times

Note 1 to entry: Single value (worst case) is specified in temperature units (e.g. ± 0,8 °C).

Note 2 to entry: The number of elements used for the moving average is defined in Clause 5. In practical

applications, other methods of smoothing might be applicable.
3.16
temperature repeatability

precision of temperature data based on repeated temperature traces at a given location

expressed by twice the standard deviation of corresponding temperature sample points in

each temperature trace, with the fibre optic sensor held at constant temperature
Temperature (°C)
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SIST EN 61757-2-2:2017
IEC 61757-2-2:2016 © IEC 2016 – 11 –
3.17
temperature sample point

measured temperature value associated with a single point at a known location along a fibre

optic sensor

Note 1 to entry: Due to thermodynamic effects, the measured value represents the temperature along a very small

section of the fibre optic sensor that includes the point.
3.18
temperature trace

set of temperature sample points distributed along a fibre optic sensor and spaced by the

sample spacing

Note 1 to entry: All the sample points are associated with a common time of measurement, often called the trace

timestamp. The measured values represent the temperature during a period that includes the timestamp.

Note 2 to entry: All the sample points in a temperature trace are measured values produced by the DTS

instrument, and not interpolated or smoothed values produced by subsequent processing outside the instrument.

3.19
total fibre length

distance from the DTS output connector to the final end of the fibre optic sensor

Note 1 to entry: Final end of the fibre optic sensor can either be a purposefully cut or terminated end of the fibre

physically far from the instrument (in a single-ended configuration), or the end of a loop consisting of a connector

that is connected to the same instrument (in a loop configuration).

Note 2 to entry: This parameter is either equal to or greater than the distance measurement.

Note 3 to entry: The distance measurement range is expressed in length units (m or km).

3.20
warm-up time

duration of time starting from the initiation of the first temperature measurement until the DTS

instrument complies with specified measurement specifications
3.21
worst case environmental temperature effect

maximum difference of the measured constant fibre optic sensor temperature at different

locations along the sensor during a complete temperature cycling of the DTS instrument

across the entire instrument operating temperature range

Note 1 to entry: This parameter is derived from environmental temperature stability.

4 General test setups for measurement of performance parameters
4.1 General and test setup requirements
General test setups for single and loop configurations a
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