prEN IEC 61757-1-2:2023
(Main)Fibre optic sensors - Part 1-2: Strain measurement - Distributed sensing based on Brillouin scattering
Fibre optic sensors - Part 1-2: Strain measurement - Distributed sensing based on Brillouin scattering
Lichtwellenleiter-Sensoren - Teil 1-2: Dehnungsmessung - Verteilte Sensorik auf der Basis von Brillouin-Streuung
Capteurs fibroniques - Partie 1-2: Mesure de déformation - Détection répartie basée sur la diffusion de Brillouin
Optični senzorji - 1-2. del: Merjenje deformacij - Porazdeljeno zaznavanje na podlagi Brillouinovega sipanja
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN IEC 61757-1-2:2022
01-september-2022
Optični senzorji - 1-2. del: Merjenje deformacij - Porazdeljeno zaznavanje na
podlagi Brillouinovega sipanja
Fibre Optic Sensors - Part 1-2: Strain measurement - Distributed sensing based on
Brillouin scattering
Capteurs fibroniques - Partie 1-2: Mesure de déformation - Détection répartie basée sur
la diffusion de Brillouin
Ta slovenski standard je istoveten z: prEN IEC 61757-1-2:2022
ICS:
33.180.99 Druga oprema za optična Other fibre optic equipment
vlakna
oSIST prEN IEC 61757-1-2:2022 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN IEC 61757-1-2:2022
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oSIST prEN IEC 61757-1-2:2022
86C/1798/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61757-1-2 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2022-06-24 2022-09-16
SUPERSEDES DOCUMENTS:
86C/1768/CD, 86C/1796/CC
IEC SC 86C : FIBRE OPTIC SYSTEMS AND ACTIVE DEVICES
SECRETARIAT: SECRETARY:
United States of America Mr Fred Heismann
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
TC 17,TC 18,TC 20,TC 38,TC 45,TC 65,TC 85
Other TC/SCs are requested to indicate their interest, if
any, in this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of
which they are aware and to provide supporting documentation.
TITLE:
Fibre Optic Sensors - Part 1-2: Strain measurement - Distributed sensing based on Brillouin
scattering
PROPOSED STABILITY DATE: 2026
NOTE FROM TC/SC OFFICERS:
Copyright © 2022 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to download this
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.
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oSIST prEN IEC 61757-1-2:2022
IEC CDV 61757-1-2/Ed1 © IEC:2022 – 2 – 86C/1798/CDV
1 CONTENTS
2
3 FOREWORD . 3
4 INTRODUCTION . 5
5 1 Scope . 6
6 2 Normative references . 6
7 3 Terms, definitions, abbreviated terms and quantity symbols . 6
8 3.1 Terms and definitions. 6
9 3.2 Abbreviated terms . 10
10 3.3 Quantity symbols . 10
11 4 General test setups for measurement of performance parameters . 10
12 4.1 General and test setup requirements . 10
13 4.2 General documentation requirements . 15
14 5 Measurement procedures for performance parameters . 15
15 5.1 Strain measurement error . 15
16 5.1.1 Test procedure and conditions . 15
17 5.1.2 Parameter calculation and reporting . 16
18 5.2 Spatial resolution . 16
19 5.2.1 Test procedure and conditions . 16
20 5.2.2 Parameter calculation and reporting . 16
21 5.3 Strain repeatability . 17
22 5.3.1 Test procedure and conditions . 17
23 5.3.2 Parameter calculation and reporting . 17
24 5.4 Spatial strain uncertainty . 18
25 5.4.1 Test procedure and conditions . 18
26 5.4.2 Parameter calculation and reporting . 18
27 5.5 Warm-up time . 18
28 5.5.1 Test procedure and conditions . 18
29 5.5.2 Parameter calculation and reporting . 19
30 5.6 Attenuation range . 19
31 5.6.1 General . 19
32 5.6.2 Method A based on strain repeatability . 19
33 5.6.3 Method B based on spatial strain uncertainty . 20
34 Bibliography . 22
35
36 Figure 1 – Optical fibre strain profile and related strain sample points . 8
37 Figure 2 – General test setup for single-ended configuration . 11
38 Figure 3 – General test setup for loop configuration . 12
39 Figure 4 – Measured vs applied strain (typical curve). 14
40 Figure 5 – Brillouin frequency shift as a function of elongation of a standard
41 telecommunication fibre . 14
42
43
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IEC CDV 61757-1-2/Ed1 © IEC:2022 – 3 – 86C/1798/CDV
44 INTERNATIONAL ELECTROTECHNICAL COMMISSION
45 ____________
46
47 FIBRE OPTIC SENSORS –
48
49 Part 1-2: Strain measurement – Distributed sensing based on Brillouin
50 scattering
51
52 FOREWORD
53 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
54 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
55 international co-operation on all questions concerning standardization in the electrical and electronic fields. To
56 this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
57 Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
58 Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
59 in the subject dealt with may participate in this preparatory work. International, governmental and non-
60 governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
61 with the International Organization for Standardization (ISO) in accordance with conditions determined by
62 agreement between the two organizations.
63 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
64 consensus of opinion on the relevant subjects since each technical committee has representation from all
65 interested IEC National Committees.
66 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
67 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
68 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
69 misinterpretation by any end user.
70 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
71 transparently to the maximum extent possible in their national and regional publications. Any divergence
72 between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
73 the latter.
74 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
75 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
76 services carried out by independent certification bodies.
77 6) All users should ensure that they have the latest edition of this publication.
78 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
79 members of its technical committees and IEC National Committees for any personal injury, property damage or
80 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
81 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
82 Publications.
83 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
84 indispensable for the correct application of this publication.
85 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
86 patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
87 IEC 61757-1-2 has been prepared by subcommittee SC 86C: Fibre optic systems and active
88 devices, of IEC technical committee TC 86: Fibre optics. It is an International Standard.
89 The text of this International Standard is based on the following documents:
Draft Report on voting
XX/XX/FDIS XX/XX/RVD
90
91 Full information on the voting for its approval can be found in the report on voting indicated in
92 the above table.
93 The language used for the development of this International Standard is English.
94 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
95 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
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IEC CDV 61757-1-2/Ed1 © IEC:2022 – 4 – 86C/1798/CDV
96 available at www.iec.ch/members_experts/refdocs. The main document types developed by
97 IEC are described in greater detail at www.iec.ch/standardsdev/publications.
98 A list of all parts in the IEC 61757 series, published under the general title Fibre optic
99 sensors, can be found on the IEC website.
100 The committee has decided that the contents of this document will remain unchanged until the
101 stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
102 the specific document. At this date, the document will be
103 • reconfirmed,
104 • withdrawn,
105 • replaced by a revised edition, or
106 • amended.
107
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108 INTRODUCTION
109 This International Standard is part of the IEC 61757 series, which is dedicated to fibre optic
110 sensors. Generic specifications for fibre optic sensors are defined in IEC 61757.
111 The individual parts of the IEC 61757 series are numbered as IEC 61757-M-T, where M
112 denotes the measure and T the technology of the fibre optic sensor. The IEC 61757-1-T
113 series is concerned with strain measurements.
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IEC CDV 61757-1-2/Ed1 © IEC:2022 – 6 – 86C/1798/CDV
114 FIBRE OPTIC SENSORS –
115
116 Part 1-2: Strain measurement – Distributed sensing based on Brillouin
117 scattering
118
119 1 Scope
120 This part of IEC 61757 defines detailed specifications for distributed strain measurements
121 with a fibre optic sensor, also known as fibre optic distributed strain sensing. It is applicable
122 to distributed strain sensing systems (DSS) based on spontaneous or stimulated Brillouin
123 scattering in the optical fibre sensor (strain sensitive element), that is, to sensors capable of
124 measuring absolute strain. This International Standard specifies the most important DSS
125 performance parameters and defines the procedures for their determination.
126 2 Normative references
127 The following documents are referred to in the text in such a way that some or all of their
128 content constitutes requirements of this document. For dated references, only the edition
129 cited applies. For undated references, the latest edition of the referenced document (including
130 any amendments) applies.
131 EN 50244:2016, Electrical apparatus for the detection of combustible gases in domestic
132 premises. Guide on the selection, installation, use and maintenance
133 IEC 60050 (all parts), International Electrotechnical Vocabulary
134 IEC 61757:2018, Fibre optic sensors – Generic specification
135 IEC 61757-2-2:2016, Fibre optic sensors – Part 2-2: Temperature measurement – Distributed
136 sensing
137 IEC 61757-3-2:2022, Fibre optic sensors – Part 3-2: Acoustic sensing and vibration
138 measurement – Distributed sensing
139 ISO/IEC GUIDE 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
140 uncertainty in measurement (GUM:1995)
141 ISO/IEC Guide 99, International vocabulary of metrology – Basic and general concepts and
142 associated terms (VIM)
143 3 Terms, definitions, abbreviated terms and quantity symbols
144 3.1 Terms and definitions
145 For the purposes of this document, the terms and definitions given in IEC 61757, IEC 61757-
146 2-2, IEC 61757-3-2, IEC 60050 (all parts), and the following apply.
147 ISO and IEC maintain terminological databases for use in standardization at the following
148 addresses:
149 • IEC Electropedia: available at http://www.electropedia.org/
150 • ISO Online browsing platform: available at http://www.iso.org/obp
151 Note: For the following definitions, the relevant test procedures and parameters are defined in Clause 4.
152 3.1.1
153 attenuation range
154 total accumulated optical loss (one way) tolerated by the DSS without affecting the specified
155 measurement performance more than a given factor for a given location, spatial resolution,
156 and measurement time
157 Note 1 to entry: The total accumulated loss can include fibre attenuation as well as point defect losses introduced
158 by components such as connectors, splices, fibre kinks, and attenuators.
159 Note 2 to entry: The attenuation range is usually expressed in dB.
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160 Note 3 to entry: For fibre loop configurations, the attenuation range is specified by the loss between the output
161 and input connector of the interrogation unit.
162 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
163 3.1.2
164 distributed fibre optic strain sensing system
165 DSS
166 measurement set-up consisting of a distributed fibre optic sensor connected to an
167 interrogation unit, including processor, data archive, and user interface, which provides a
168 spatially resolved strain measurement
169 [SOURCE: IEC 61757-3-2:2022, modified − adapted to distributed strain measurement]
170 3.1.3
171 distance measurement range
172 maximum distance from the DSS interrogation unit output connector along the fibre optic
173 sensor within which the DSS measures strain with specified measurement performance under
174 defined conditions
175 Note 1 to entry: Defined conditions are spatial resolution (3.1.9), spatial strain uncertainty (3.1.10) and
176 measurement time (3.1.6).
177 Note 2 to entry: This supporting parameter is closely related to the attenuation range of the interrogation unit. In
178 test cases used to prove or verify the reported specifications, the total fibre length shall be equal to or greater than
179 the specified distance measurement range, for the specified attenuation range.
180 Note 3 to entry: The distance measurement range is usually expressed in km.
181 Note 4 to entry: For fibre loop configurations, the distance measurement range is given by half the fibre length
182 between the output and input connector of the interrogation unit.
183 [SOURCE: IEC 61757-2-2:2016 and ISO/IEC Guide 99, 4.7, modified − adapted to distributed
184 strain measurement]
185 3.1.4
186 strained spot
187 ΔL
188 length of fibre optic sensor that experiences a small elongation (δL), which causes strain that
189 is significantly bigger than the strain repeatability of the interrogation unit and which is
190 confirmed by a reference strain measurement
191 Note 1 to entry: The applied strain ε is equal to (δL/ΔL).
192 Note 2 to entry: It is useful to define strain in με, where 1 με corresponds to a δL of 1 μm over a ΔL of 1 m.
193 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
194 3.1.5
195 location
196 L
197 optical distance from the DSS interrogation unit output connector to a desired strain sample
198 point along the fibre optic sensor
199 Note 1 to entry: The farthest location from the DSS interrogation unit output connector for the particular test is
200 quantified as L km and is often chosen to be the same as the distance measurement range for purposes of
F,long
201 comparing the measurement results with quoted specifications.
202 Note 2 to entry: The location is usually expressed in km.
203 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
204 3.1.6
205 measurement time
206 time between independent strain measurements when making successive measurements on a
207 single fibre optic sensor
208 Note 1 to entry: Equivalently, it is the time interval between successive strain trace timestamps under these
209 conditions.
210 Note 2 to entry: This parameter includes acquisition time and processing time for the measured data. This
211 parameter is typically selectable by the user in some limited fashion. Multiple independent strain measurements
212 may be averaged together to provide an overall measurement time.
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213 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
214 3.1.7
215 point defect
216 local deviation of a fibre optic sensor from its nominal optical and mechanical properties
217 occurring at a single location, or over a length substantially less than the DSS spatial
218 resolution
219 Note 1 to entry: The definition of a point defect encompasses a wide range of situations, which can produce
220 similar effects on the strain trace. Examples include:
221 – a point loss, like a bad fibre splice,
222 – a back reflection (or return loss), as can be introduced by a fibre connector,
223 – a localized region of high loss, such as a bend or kink in the fibre,
224 – a physical discontinuity in the fibre, like a splice between two fibres of different core diameters.
225 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
226 3.1.8
227 sample spacing
228 distance between two consecutive strain sample points in a single strain trace
229 Note 1 to entry: Sample spacing can be a user-selectable parameter in the interrogation unit.
230 Note 2 to entry: The sample spacing is usually expressed in m.
231 Note 3 to entry: See Figure 1.
232 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
Sample
spacing
Fibre strain to
be measured
Strain
sample
point
Location [m]
233
234 Figure 1 – Optical fibre strain profile and related strain sample points
235 3.1.9
236 spatial resolution
237 smallest length of strain-affected fibre optic sensor for which a DSS can measure and confirm
238 the reference strain of a defined strained spot within the specified strain measurement error of
239 the DSS
240 Note 1 to entry: The spatial resolution is usually expressed in m.
241 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
242 3.1.10
243 spatial strain uncertainty
244 uncertainty of the location of strain data in a single strain trace, expressed by twice the
245 standard deviation of a specified number of adjacent strain sample points, with the fibre optic
246 sensor held at constant strain and temperature
Fibre strain [με]
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247 Note 1 to entry: Due to a potential cross-sensitivity of DSS to temperature, it can be necessary to stabilize the
248 temperature of the fibre optic sensor.
249 Note 2 to entry: The spatial strain uncertainty is usually expressed in units of με and noted as a tolerance (e.g., ±
250 xx με), where 1 με corresponds to a δL of 1 μm over a ΔL of 1 m.
251 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
252 3.1.11
253 strain dead zone
254 limited zone of a strain trace, where the strain sample points deviate from the undisturbed
255 parts of the trace by a specified limit due to a point defect
256 Note 1 to entry: The strain dead zone is usually expressed in m.
257 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
258 3.1.12
259 strain measurement error
260 maximum difference between a centred and uniformly weighted moving average of the
261 measured strain and a reference strain for all data points of the fibre optic sensor over the full
262 operating temperature range and all acquisition times
263 Note 1 to entry: Single value (worst case) is expressed like a tolerance in units of με (e.g., ± xx με).
264 Note 2 to entry: The number of elements used for the moving average is defined later in the document. In
265 practical applications other methods of smoothing might be applicable.
266 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
267 3.1.13
268 strain repeatability
269 precision of strain data based on repeated strain traces at a given location expressed by twice
270 the standard deviation of corresponding strain sample points in each strain trace, with the
271 fibre optic sensor held at constant strain and temperature
272 Note 1 to entry: The strain repeatability is expressed like a tolerance in units of με (e.g., ± xx με).
273 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
274 3.1.14
275 strain sample point
276 measured strain value associated with a single point at a known location along a fibre optic
277 sensor
278 Note 1 to entry: Due to signal averaging effects, the measured value represents the strain along a very small
279 section of the fibre optic sensor that includes the strain sample point.
280 Note 2 to entry: See Figure 1.
281 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
282 3.1.15
283 strain trace
284 set of strain sample points distributed along a fibre optic sensor and spaced by the sample
285 spacing
286 Note 1 to entry: All sample points are associated with a common time of measurement, often called the trace
287 timestamp. The measured values represent the strain during a time period that includes the timestamp.
288 Note 2 to entry: All sample points in a strain trace are measured values produced by the DSS, and not
289 interpolated or smoothed values produced by subsequent processing outside the interrogation unit.
290 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
291 3.1.16
292 total fibre length
293 L
F,tot
294 distance from the DSS interrogation unit output connector to the final end of the fibre optic
295 sensor
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296 Note 1 to entry: The final end of the fibre optic sensor can be either a purposely cut or terminated end of the
297 fibre, physically located far from the interrogation unit (in a single-ended configuration), or the end of a loop
298 consisting of a connector that is connected to the same interrogation unit (in a loop configuration).
299 Note 2 to entry: This parameter is either equal to or greater than the distance measurement range and usually
300 expressed in km.
301 [SOURCE: IEC 61757-2-2:2016, modified − adapted to distributed strain measurement]
302 3.1.17
303 warm-up time
304 time interval between the time when the DSS interrogation unit is switched on and the time
305 when the unit is fully operational as specified by the manufacturer
306 Note 1 to entry: Warm-up time is usually expressed in seconds or minutes.
307 Note 2 to entry: The warm-up time helps to upload software and to stabilize operating temperatures of optical and
308 electronic components.
309 [SOURCE: EN 50244:2016, modified − adapted to distributed strain measurement]
310 3.2 Abbreviated terms
311 DSS distributed fibre optic strain sensing system
312 FAT factory acceptance test
313 LVDT linear variable differential transformer
314 VOA variable optical attenuator
315
316 3.3 Quantity symbols
317 A cross-sectional area
318 E Young’s modulus
319 F force
320 L optical distance from the output connector to a desired strain sample point
321 L , L fibre lengths
F,opt F,short
322 L , L fibre lengths
F,loop F,long
323 L total fibre length
F,tot
324 ΔL length of fibre optic sensor to be strained (strained spot)
325 δL small change in length of ΔL
326 N, n number of traces, number of data points
327 S standard deviation
328 T temperature
329 T , T , T minimum, typical, and maximum DSS operating temperature
low op high
330 T ambient operating temperature of the strain test section
STC
331 ε strain
332 ε strain repeatability
rep
333 ε spatial strain uncertainty
unc
334 σ stress
335 4 General test setups for measurement of performance parameters
336 4.1 General and test setup requirements
337 General test setups for single-ended and loop configurations are schematically shown in
338 Figure 2 and Figure 3, respectively. The aim of these setups is to provide a common base for
339 determining the measurement specifications while at the same time minimizing complexity,
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340 cost, reconfiguration requirements, and test execution time. Temperature stabilisation is used
341 to avoid crosstalk from temperature.
342
343 Key
344 1 Temperature-controlled encasement (e.g., temperature chamber)
345 2 DSS interrogation unit
346 3 DSS interrogation unit output connector
347 4 Fibre fusion splice
348 5 Optional variable optical attenuator
349 6 Optional long fibre length L (normal spool)
F,opt
350 7 Temperature-controlled environment for stable ambient conditions
351 8 Long fibre length L (loose and strain free wound)
F,long
352 9 Strain test section with temperature-controlled environment for stable ambient conditions
353 10 Fixed fibre clamping unit
354 11 Movable fibre clamping unit
355 12 Short fibre length L (loose wound), longer than 5 times the spatial resolution
F,short
356 13 Fibre termination
357 Figure 2 – General test setup for single-ended configuration
358
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359
360 Key
361 1 Temperature-controlled encasement (e.g. temperature chamber)
362 2 DSS interrogation unit
363 3 DSS interrogation unit output connector
364 4 Fibre fusion splice
365 5 Optional variable optical attenuator
366 6 Optional long fibre length L (normal spool)
F,opt
367 7 Temperature-controlled environment for stable ambient conditions
368 8 Long fibre length L (loose and strain fre
...
SLOVENSKI STANDARD
oSIST prEN IEC 61757-1-2:2023
01-maj-2023
Optični senzorji - 1-2. del: Merjenje deformacij - Porazdeljeno zaznavanje na
podlagi Brillouinovega sipanja
Fibre Optic Sensors - Part 1-2: Strain measurement - Distributed sensing based on
Brillouin scattering
Lichtwellenleiter-Sensoren - Teil 1-2: Dehnungsmessung - Verteilte Sensorik auf der
Basis von Brillouin-Streuung
Capteurs fibroniques - Partie 1-2: Mesure de déformation - Détection répartie basée sur
la diffusion de Brillouin
Ta slovenski standard je istoveten z: prEN IEC 61757-1-2:2023
ICS:
33.180.99 Druga oprema za optična Other fibre optic equipment
vlakna
oSIST prEN IEC 61757-1-2:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN IEC 61757-1-2:2023
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oSIST prEN IEC 61757-1-2:2023
86C/1857/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61757-1-2 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2023-03-10 2023-05-05
SUPERSEDES DOCUMENTS:
86C/1798/CDV, 86C/1846/RVC
IEC SC 86C : FIBRE OPTIC SYSTEMS AND ACTIVE DEVICES
SECRETARIAT: SECRETARY:
United States of America Mr Fred Heismann
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
TC 17,TC 18,TC 20,TC 38,TC 45,TC 65,TC 85
Other TC/SCs are requested to indicate their interest, if
any, in this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of
• any relevant patent rights of which they are aware and to provide supporting documentation,
• any relevant “in some countries” clauses to be included should this proposal proceed. Recipients are
reminded that the enquiry stage is the final stage for submitting "in some countries" clauses. See
AC/22/2007.
TITLE:
Fibre Optic Sensors - Part 1-2: Strain measurement - Distributed sensing based on Brillouin
scattering
PROPOSED STABILITY DATE: 2026
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oSIST prEN IEC 61757-1-2:2023
IEC CDV 61757-1-2/Ed1 © IEC 2023 – 2 – 86C/1857/CDV
1 CONTENTS
2
3 FOREWORD . 3
4 INTRODUCTION . 5
5 1 Scope . 6
6 2 Normative references . 6
7 3 Terms, definitions, abbreviated terms and symbols . 6
8 3.1 Terms and definitions . 6
9 3.2 Abbreviated terms . 10
10 3.3 Symbols . 10
11 4 General test setups for measurement of performance parameters . 11
12 4.1 General and test setup requirements . 11
13 4.2 General documentation requirements . 16
14 5 Measurement procedures for performance parameters . 17
15 5.1 Strain measurement error . 17
16 5.1.1 Test procedure and conditions . 17
17 5.1.2 Parameter calculation and reporting . 17
18 5.2 Spatial resolution . 17
19 5.2.1 Test procedure and conditions . 17
20 5.2.2 Parameter calculation and reporting . 18
21 5.3 Strain repeatability . 18
22 5.3.1 Test procedure and conditions . 18
23 5.3.2 Parameter calculation and reporting . 18
24 5.4 Spatial strain uncertainty . 19
25 5.4.1 Test procedure and conditions . 19
26 5.4.2 Parameter calculation and reporting . 19
27 5.5 Warm-up time . 20
28 5.5.1 Test procedure and conditions . 20
29 5.5.2 Parameter calculation and reporting . 20
30 5.6 System performance with altered attenuation . 21
31 5.6.1 General . 21
32 5.6.2 At distance measurement range . 21
33 5.6.3 At short distance with high loss. 22
34 Bibliography . 25
35
36 Figure 1 – Optical fibre strain profile and related strain sample points. 8
37 Figure 2 – General test setup for single-ended configuration . 12
38 Figure 3 – General test setup for loop configuration . 13
39 Figure 4 – Measured versus applied strain (typical curve) . 15
40 Figure 5 – Brillouin frequency shift as a function of elongation of a standard
41 telecommunication fibre . 15
42 Figure 6 – Performance evaluation at distance measurement range . 21
43 Figure 7 – Performance evaluation at short distance with high loss . 23
44
45
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46 INTERNATIONAL ELECTROTECHNICAL COMMISSION
47 ____________
48
49 FIBRE OPTIC SENSORS –
50
51 Part 1-2: Strain measurement – Distributed sensing based on
52 Brillouin scattering
53
54 FOREWORD
55 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
56 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
57 co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
58 in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
59 Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
60 preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
61 may participate in this preparatory work. International, governmental and non-governmental organizations liaising
62 with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
63 Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
64 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
65 consensus of opinion on the relevant subjects since each technical committee has representation from all
66 interested IEC National Committees.
67 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
68 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
69 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
70 misinterpretation by any end user.
71 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
72 transparently to the maximum extent possible in their national and regional publications. Any divergence between
73 any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
74 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
75 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
76 services carried out by independent certification bodies.
77 6) All users should ensure that they have the latest edition of this publication.
78 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
79 members of its technical committees and IEC National Committees for any personal injury, property damage or
80 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
81 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
82 Publications.
83 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
84 indispensable for the correct application of this publication.
85 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
86 rights. IEC shall not be held responsible for identifying any or all such patent rights.
87 IEC 61757-1-2 has been prepared by subcommittee 86C: Fibre optic systems and active
88 devices, of IEC technical committee 86: Fibre optics. It is an International Standard.
89 The text of this International Standard is based on the following documents:
Draft Report on voting
86C/XX/FDIS 86C/XX/RVD
90
91 Full information on the voting for its approval can be found in the report on voting indicated in
92 the above table.
93 The language used for the development of this International Standard is English.
94 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
95 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
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96 at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
97 described in greater detail at www.iec.ch/publications.
98 A list of all parts in the IEC 61757 series, published under the general title Fibre optic sensors,
99 can be found on the IEC website.
100 The committee has decided that the contents of this document will remain unchanged until the
101 stability date indicated on the IEC website under webstore.iec.ch in the data related to the
102 specific document. At this date, the document will be
103 • reconfirmed,
104 • withdrawn,
105 • replaced by a revised edition, or
106 • amended.
107
IMPORTANT – The "colour inside" logo on the cover page of this document 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.
108
109
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110 INTRODUCTION
111 This International Standard is part of the IEC 61757 series, which is dedicated to fibre optic
112 sensors. Generic specifications for fibre optic sensors are defined in IEC 61757.
113 The individual parts of the IEC 61757 series are numbered as IEC 61757-M-T, where M denotes
114 the measure and T the technology of the fibre optic sensor. The IEC 61757-1-T series is
115 concerned with strain measurements.
116
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117 FIBRE OPTIC SENSORS –
118
119 Part 1-2: Strain measurement – Distributed sensing based on
120 Brillouin scattering
121
122
123
124 1 Scope
125 This part of IEC 61757 defines detailed specifications for distributed strain measurements with
126 a fibre optic sensor, also known as fibre optic distributed strain sensing. It is applicable to
127 distributed strain sensing systems (DSS) based on spontaneous or stimulated Brillouin
128 scattering in the optical fibre sensor (strain sensitive element), that is, to sensors capable of
129 measuring absolute strain. This document specifies the most important DSS performance
130 parameters and defines the procedures for their determination.
131 2 Normative references
132 The following documents are referred to in the text in such a way that some or all of their content
133 constitutes requirements of this document. For dated references, only the edition cited applies.
134 For undated references, the latest edition of the referenced document (including any
135 amendments) applies.
136 IEC 60869-1, Fibre optic interconnecting devices and passive components – Fibre optic passive
137 power control devices – Part 1: Generic specification
138 IEC 61757:2018, Fibre optic sensors – Generic specification
139 IEC 61757-2-2:2016, Fibre optic sensors – Part 2-2: Temperature measurement – Distributed
140 sensing
141 IEC 61757-3-2:2022, Fibre optic sensors – Part 3-2: Acoustic sensing and vibration
142 measurement – Distributed sensing
143 ISO/IEC GUIDE 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
144 uncertainty in measurement (GUM:1995)
145 3 Terms, definitions, abbreviated terms and symbols
146 3.1 Terms and definitions
147 For the purposes of this document, the terms and definitions given in IEC 61757,
148 IEC 61757‑2‑2, IEC 61757-3-2, and the following apply.
149 ISO and IEC maintain terminology databases for use in standardization at the following
150 addresses:
151 • IEC Electropedia: available at https://www.electropedia.org/
152 • ISO Online browsing platform: available at https://www.iso.org/obp
153 NOTE For the following definitions, the relevant test procedures and parameters are defined in Clause 4.
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154 3.1.1
155 distributed fibre optic strain sensing system
156 DSS
157 measurement set-up consisting of a distributed fibre optic sensor connected to an interrogation
158 unit, including processor, data archive, and user interface, which provides a spatially resolved
159 strain measurement
160 [SOURCE: IEC 61757-3-2:2022, 3.1.2, modified − adapted to distributed strain measurement]
161 3.1.2
162 distance measurement range
163 maximum distance from the DSS interrogation unit output connector along the fibre optic sensor
164 within which the DSS measures strain with specified measurement performance under defined
165 conditions
166 Note 1 to entry: Defined conditions are spatial resolution (3.1.9), spatial strain uncertainty (3.1.10) and
167 measurement time (3.1.6).
168 Note 2 to entry: This supporting parameter is closely related to the total accumulated optical loss (one way)
169 tolerated by the interrogation unit without affecting specified measurement performance. In test cases used to prove
170 or verify the reported specifications, the total fibre length shall be equal to or greater than the specified distance
171 measurement range, for the tolerated total accumulated optical loss.
172 Note 3 to entry: The distance measurement range is usually expressed in km.
173 Note 4 to entry: For fibre loop configurations, the distance measurement range is given by half the fibre length
174 between the output and input connector of the interrogation unit.
175 [SOURCE: IEC 61757-2-2:2016, 3.2 and ISO/IEC Guide 99:2007, 4.7, modified − adapted to
176 distributed strain measurement]
177 3.1.3
178 strained spot
179 ΔL
180 length of fibre optic sensor that experiences a small elongation (δL), which causes strain that
181 is significantly bigger than the strain repeatability of the interrogation unit and which is
182 confirmed by a reference strain measurement
183 Note 1 to entry: The applied strain ε is equal to (δL/ΔL).
184 Note 2 to entry: It is useful to define strain in με, where 1 με corresponds to a δL of 1 μm over a ΔL of 1 m.
185 [SOURCE: IEC 61757-2-2:2016, 3.6, modified − adapted to distributed strain measurement]
186 3.1.4
187 location
188 L
189 optical distance from the DSS interrogation unit output connector to a desired strain sample
190 point along the fibre optic sensor
191 Note 1 to entry: The farthest location from the DSS interrogation unit output connector for the particular test is
192 quantified as L km and is often chosen to be the same as the distance measurement range for purposes of
F,long
193 comparing the measurement results with quoted specifications.
194 Note 2 to entry: The location is usually expressed in km.
195 [SOURCE: IEC 61757-2-2:2016, 3.7, modified − adapted to distributed strain measurement]
196 3.1.5
197 measurement time
198 time between independent strain measurements when making successive measurements on a
199 single fibre optic sensor
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200 Note 1 to entry: Equivalently, it is the time interval between successive strain trace timestamps under these
201 conditions.
202 Note 2 to entry: This parameter includes acquisition time and processing time for the measured data. This
203 parameter is typically selectable by the user in some limited fashion. Multiple independent strain measurements may
204 be averaged together to provide an overall measurement time.
205 [SOURCE: IEC 61757-2-2:2016, 3.8, modified − adapted to distributed strain measurement]
206 3.1.6
207 point defect
208 local deviation of a fibre optic sensor from its nominal optical and mechanical properties
209 occurring at a single location, or over a length substantially less than the DSS spatial resolution
210 Note 1 to entry: The definition of a point defect encompasses a wide range of situations, which can produce similar
211 effects on the strain trace. Examples include:
212 – a point loss, like a bad fibre splice,
213 – a back reflection (or return loss), as can be introduced by a fibre connector,
214 – a localized region of high loss, such as a bend or kink in the fibre,
215 – a physical discontinuity in the fibre, like a splice between two fibres of different core diameters.
216 [SOURCE: IEC 61757-2-2:2016, 3.9, modified − adapted to distributed strain measurement]
217 3.1.7
218 sample spacing
219 distance between two consecutive strain sample points in a single strain trace
220 Note 1 to entry: Sample spacing can be a user-selectable parameter in the interrogation unit.
221 Note 2 to entry: The sample spacing is usually expressed in m.
222 Note 3 to entry: See Figure 1.
223 [SOURCE: IEC 61757-2-2:2016, 3.11, modified − adapted to distributed strain measurement]
224
225 Figure 1 – Optical fibre strain profile and related strain sample points
226 3.1.8
227 spatial resolution
228 smallest length of strain-affected fibre optic sensor for which a DSS can measure and confirm
229 the reference strain of a defined strained spot within the specified strain measurement error of
230 the DSS
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231 Note 1 to entry: The spatial resolution is usually expressed in m.
232 [SOURCE: IEC 61757-2-2:2016, 3.12, modified − adapted to distributed strain measurement]
233 3.1.9
234 spatial strain uncertainty
235 uncertainty of the location of strain data in a single strain trace, expressed by twice the standard
236 deviation of a specified number of adjacent strain sample points, with the fibre optic sensor held
237 at constant strain and temperature
238 Note 1 to entry: Due to a potential cross-sensitivity of DSS to temperature, it can be necessary to stabilize the
239 temperature of the fibre optic sensor.
240 Note 2 to entry: The spatial strain uncertainty is usually expressed in units of με and noted as a tolerance (e.g. ± xx
241 με), where 1 με corresponds to a δL of 1 μm over a ΔL of 1 m.
242 [SOURCE: IEC 61757-2-2:2016, 3.13, modified − adapted to distributed strain measurement]
243 3.1.10
244 strain dead zone
245 limited zone of a strain trace, where the strain sample points deviate from the undisturbed parts
246 of the trace by a specified limit due to a point defect
247 Note 1 to entry: The strain dead zone is usually expressed in m.
248 [SOURCE: IEC 61757-2-2:2016, 3.14, modified − adapted to distributed strain measurement]
249 3.1.11
250 strain measurement error
251 maximum difference between a centred and uniformly weighted moving average of the
252 measured strain and a reference strain for all data points of the fibre optic sensor over the full
253 operating temperature range and all acquisition times
254 Note 1 to entry: Single value (worst case) is expressed like a tolerance in units of με (e.g. ± xx με).
255 Note 2 to entry: The number of elements used for the moving average is defined later in the document. In practical
256 applications other methods of smoothing might be applicable.
257 [SOURCE: IEC 61757-2-2:2016, 3.15, modified − adapted to distributed strain measurement]
258 3.1.12
259 strain repeatability
260 precision of strain data based on repeated strain traces at a given location expressed by twice
261 the standard deviation of corresponding strain sample points in each strain trace, with the fibre
262 optic sensor held at constant strain and temperature
263 Note 1 to entry: The strain repeatability is expressed like a tolerance in units of με (e.g. ± xx με).
264 [SOURCE: IEC 61757-2-2:2016, 3.16, modified − adapted to distributed strain measurement]
265 3.1.13
266 strain sample point
267 measured strain value associated with a single point at a known location along a fibre optic
268 sensor
269 Note 1 to entry: Due to signal averaging effects, the measured value represents the strain along a very small section
270 of the fibre optic sensor that includes the strain sample point.
271 Note 2 to entry: See Figure 1.
272 [SOURCE: IEC 61757-2-2:2016, 3.17, modified − adapted to distributed strain measurement]
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273 3.1.14
274 strain trace
275 set of strain sample points distributed along a fibre optic sensor and spaced by the sample
276 spacing
277 Note 1 to entry: All sample points are associated with a common time of measurement, often called the trace
278 timestamp. The measured values represent the strain during a time period that includes the timestamp.
279 Note 2 to entry: All sample points in a strain trace are measured values produced by the DSS, and not interpolated
280 or smoothed values produced by subsequent processing outside the interrogation unit.
281 [SOURCE: IEC 61757-2-2:2016, 3.18, modified − adapted to distributed strain measurement]
282 3.1.15
283 total fibre length
284 L
F,tot
285 distance from the DSS interrogation unit output connector to the final end of the fibre optic
286 sensor
287 Note 1 to entry: The final end of the fibre optic sensor can be either a purposely cut or terminated end of the fibre,
288 physically located far from the interrogation unit (in a single-ended configuration), or the end of a loop consisting of
289 a connector that is connected to the same interrogation unit (in a loop configuration).
290 Note 2 to entry: This parameter is either equal to or greater than the distance measurement range and usually
291 expressed in km.
292 [SOURCE: IEC 61757-2-2:2016, 3.19, modified − adapted to distributed strain measurement]
293 3.1.16
294 warm-up time
295 time interval between the time when the DSS interrogation unit is switched on and the time
296 when the unit is fully operational as specified by the manufacturer
297 Note 1 to entry: Warm-up time is usually expressed in seconds or minutes.
298 Note 2 to entry: The warm-up time helps to upload software and to stabilize operating temperatures of optical and
299 electronic components.
300 [SOURCE: EN 50244:2016, 3.20, modified − adapted to distributed strain measurement]
301 3.2 Abbreviated terms
302 DSS distributed fibre optic strain sensing system
303 FAT factory acceptance test
304 LVDT linear variable differential transformer
305 VOA variable optical attenuator
306 3.3 Symbols
307 A cross-sectional area
308 E Young’s modulus
309 F force
310 L optical distance from the output connector to a desired strain sample point
311 L , L fibre lengths
F,opt F,short
312 L , L fibre lengths
F,loop F,long
313 L total fibre length
F,tot
314 ΔL length of fibre optic sensor to be strained (strained spot)
315 δL small change in length of ΔL
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316 N, n number of traces, number of data points
317 S standard deviation
318 T temperature
319 T , T , T minimum, typical, and maximum DSS operating temperature
low op high
320 T ambient operating temperature of the strain test section
STC
321 ε strain
322 ε strain repeatability
rep
323 ε spatial strain uncertainty
unc
324 σ stress
325 4 General test setups for measurement of performance parameters
326 4.1 General and test setup requirements
327 General test setups for single-ended and loop configurations are schematically shown in
328 Figure 2 and Figure 3, respectively. The aim of these setups is to provide a common base for
329 determining the measurement specifications while at the same time minimizing complexity, cost,
330 reconfiguration requirements, and test execution time. Temperature stabilisation is used to
331 avoid crosstalk from temperature.
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332
333 Key
334 1 Temperature-controlled encasement (e.g. temperature chamber)
335 2 DSS interrogation unit
336 3 DSS interrogation unit output connector
337 4 Fibre fusion splice
338 5 Optional variable optical attenuator
339 6 Optional long fibre length L (normal spool)
F,opt
340 7 Temperature-controlled environment for stable ambient conditions
341 8 Long fibre length L (loose and strain free wound)
F,long
342 9 Strain test section with temperature-controlled environment for stable ambient conditions
343 10 Fixed fibre clamping unit
344 11 Movable fibre clamping unit
345 12 Short fibre length L (loose wound), longer than 5 times the spatial resolution
F,short
346 13 Fibre termination
347 Figure 2 – General test setup for single-ended configuration
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348
349 Key
350 1 Temperature-controlled encasement (e.g. temperature chamber)
351 2 DSS interrogation unit
352 3 DSS interrogation unit output connector
353 4 Fibre fusion splice
354 5 Optional variable optical attenuator
355 (normal spool)
6 Optional long fibre length L
F,opt
356 7 Temperature-controlled environment for stable ambient conditions
357 (loose and strain free wound)
8 Long fibre length L
F,long
358 9 Strain test section with
...
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