SIST EN IEC 61744:2023

SLOVENSKI STANDARD
oSIST prEN IEC 61744:2022
01-junij-2022
Umerjanje pribora za preskušanje kromatične disperzije
Calibration of fibre optic chromatic dispersion test sets
Kalibrierung von Prüfaufbauten zur Bestimmung der chromatischen Dispersion
Etalonnage des ensembles d'essai de la dispersion chromatique fibronique
Ta slovenski standard je istoveten z: prEN IEC 61744:2022
ICS:
33.140 Posebna merilna oprema za Special measuring
uporabo v telekomunikacijah equipment for use in
telecommunications
33.180.01 Sistemi z optičnimi vlakni na Fibre optic systems in
splošno general
oSIST prEN IEC 61744:2022 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN IEC 61744:2022

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oSIST prEN IEC 61744:2022
86/598/CDV

COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61744 ED3
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2022-04-29 2022-07-22
SUPERSEDES DOCUMENTS:
86/586/CD, 86/592/CC

IEC TC 86 : FIBRE OPTICS
SECRETARIAT: SECRETARY:
United States of America Mr Steve Swanson
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:


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:
Calibration of fibre optic chromatic dispersion test sets

PROPOSED STABILITY DATE: 2029

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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1 CONTENTS
2
3 FOREWORD . 4
4 0 Introduction . 6
5 0.1 Chromatic dispersion in optical fibres . 6
6 0.2 Chromatic dispersion (CD) test sets . 6
7 0.3 Overview of calibration procedures described in this standard . 6
8 1 Scope . 8
9 2 Normative references . 8
10 3 Terms and definitions . 8
11 4 Calibration . 12
12 4.1 General . 12
13 4.2 Preparation for calibration . 12
14 4.2.1 General advice and organization . 12
15 4.2.2 Environmental conditions requirements . 12
16 4.2.3 Measurement equipment requirements . 12
17 4.2.4 Traceability . 13
18 4.3 Calibration procedure . 13
19 5 Wavelength and delay calibration procedure . 13
20 5.1 Wavelength calibration procedure . 13
21 5.1.1 General . 13
22 5.1.2 Discrete sources . 14
23 5.1.3 Tuneable sources . 14
24 5.1.4 Uncertainties and reporting . 16
25 5.2 Delay [dispersion] calibration procedure . 17
26 5.2.1 General . 17
27 5.2.2 Equipment and preparation . 17
28 5.2.3 Calibration procedure . 19
29 5.2.4 Uncertainties and reporting . 20
30 6 Calibration using a reference fibre . 20
31 6.1 General . 20
32 6.2 Equipment and preparation . 20
33 6.3 Procedure . 20
34 6.4 Uncertainties and reporting . 21
35 7 Documentation . 21
36 7.1 Calibration certificate contents . 21
37 Annex A (normative) Mathematical basis for measurement uncertainty calculations . 23
38 A.1 General . 23
39 A.2 Deviations . 23
40 A.3 Uncertainties type A . 23
41 A.4 Uncertainties type B . 24
42 A.5 Determining the combined standard uncertainty . 25
43 A.6 Reporting . 26
44 Annex B (normative)  Calibration uncertainty . 27
45 B.1 Introduction . 27
46 B.2 Wavelength and delay calibration uncertainties . 27

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47 B.2.1 Wavelength uncertainties . 27
48 B.2.2 Optical delay calibration uncertainty . 27
49 B.2.3 Effect of dispersion modelling . 27
50 B.3 Uncertainty of a calibration using a reference fibre . 28
51 Annex C (informative) Uncertainty at operating conditions . 29
52 C.1 Introduction . 29
53 C.2 Fibre related uncertainties . 29
54 C.2.1 Axial fibre strain . 29
55 C.2.2 Fibre temperature . 29
56 C.2.3 Second order modes . 29
–
57 C.2.4 OH absorption . 30
58 C.2.5 Total fibre loss . 30
59 C.2.6 Optical reflections . 30
60 Annex D (informative) Chromatic dispersion. 31
61 D.1 Chromatic dispersion in fibres . 31
62 D.2 Description of chromatic dispersion test sets. 31
63 D.3 Measurement techniques . 32
64 D.3.1 Pulse delay method . 32
65 D.3.2 Phase shift method . 32
66 D.3.3 Differential phase shift method . 33
67 D.4 Fibre chromatic dispersion specifications . 33
68 Bibliography . 34
69
70 Figure 1 – Example of a traceability chain . 9
71 Figure 2 – Typical optical delay line artefact for CD test set delay calibration . 18
72 Figure 3 – Typical differential delay [dispersion] simulator for CD test set calibration . 19
73 Figure 4 – Reference fibre comparison . 21
74 Figure A.1 – Deviation and uncertainty type B and how to replace both by an
75 appropriately larger uncertainty . 24
76 Figure D.1 – Schematic diagram of a CD test set . 32
77
78
79

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80 INTERNATIONAL ELECTROTECHNICAL COMMISSION
81 ____________
82
83 CALIBRATION OF FIBRE OPTIC CHROMATIC DISPERSION
84 TEST SETS
85
86
87 FOREWORD
88 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
89 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
90 international co-operation on all questions concerning standardization in the electrical and electronic fields. To
91 this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
92 Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
93 Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
94 in the subject dealt with may participate in this preparatory work. International, governmental and non-
95 governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
96 with the International Organization for Standardization (ISO) in accordance with conditions determined by
97 agreement between the two organizations.
98 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
99 consensus of opinion on the relevant subjects since each technical committee has representation from all
100 interested IEC National Committees.
101 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
102 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
103 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
104 misinterpretation by any end user.
105 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
106 transparently to the maximum extent possible in their national and regional publications. Any divergence
107 between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
108 the latter.
109 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
110 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
111 services carried out by independent certification bodies.
112 6) All users should ensure that they have the latest edition of this publication.
113 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
114 members of its technical committees and IEC National Committees for any personal injury, property damage or
115 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
116 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
117 Publications.
118 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
119 indispensable for the correct application of this publication.
120 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
121 patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
122 IEC 61744 has been prepared by IEC technical committee 86: Fibre optics. It is an
123 International Standard.
124 This third edition cancels and replaces the second edition published in 2005. This edition
125 constitutes a technical revision.
126 This edition includes the following significant technical changes with respect to the previous
127 edition:
128 a) updated terms and definitions;
129 b) the use of a reference fibre standard for calibration is now allowed and at the same level
130 as the other calibration method;
131 c) Annex B was split into a new Annex B (on Calibration uncertainty, still normative) and a
132 new Annex C (Uncertainty at operating conditions, informative);
133 d) removed former clause C.3.4 on Interferometric method since this method is no longer
134 supported in IEC 60793-1-42;

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135 e) removed Annex D and other references in text to calibration compensation to align with
136 other calibration documents;
137 f) removed Annex E and other references in text to use of air wavelength since it is not used
138 in the fibre domain.
139 The text of this International Standard is based on the following documents:
Draft Report on voting
86/XX/FDIS 86/XX/RVD
140
141 Full information on the voting for its approval can be found in the report on voting indicated in
142 the above table.
143 The language used for the development of this International Standard is English.
144 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
145 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
146 available at www.iec.ch/members_experts/refdocs. The main document types developed by
147 IEC are described in greater detail at www.iec.ch/standardsdev/publications.
148 The committee has decided that the contents of this document will remain unchanged until the
149 stability date indicated on the IEC website under webstore.iec.ch in the data related to the
150 specific document. At this date, the document will be
151 • reconfirmed,
152 • withdrawn,
153 • replaced by a revised edition, or
154 • amended.
155

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156 0 Introduction
157 0.1 Chromatic dispersion in optical fibres
158 Chromatic dispersion is the variation with optical light wavelength of the light propagation
159 delay time in a length of fibre. This variation can cause bandwidth limitation in the fibre when
160 used to transmit communication signals. For a more detailed explanation, refer to Annex D
161 and IEC 60793-1-42.
162 0.2 Chromatic dispersion (CD) test sets
163 CD test sets are used to measure the chromatic dispersion properties of optical fibres and
164 typically comprise an optical source of known wavelength(s), a fibre light input coupling and
165 output coupling means, optical detection means, and electronic or optical means of
166 determining the optical delay or dispersion at the source wavelength. There are several
167 variants each requiring slightly different calibration techniques. Refer to Annex D for further
168 details.
169 In general, all CD test sets produce an output of fibre delay or dispersion versus the light
170 wavelength, typically in graphical form.
171 In essence, all CD test sets operate with wavelength as a programmed (independent)
172 variable, usually the abscissa (x-axis) and dispersion or time delay as the ordinate (y-axis) as
173 a measured (dependent) variable. By their nature, fibre chromatic dispersion measurements
174 require multiple wavelengths to be programmed. Even in the case of a single dispersion point
175 obtained using the differential phase shift method, two separate wavelength values are used.
176 It is also typical to expect a wide range of dispersion values over a range of wavelengths to be
177 measured.
178 0.3 Overview of calibration procedures described in this standard
179 The requirement to calibrate the CD test set, traceable to known standards, is essential for
180 quality control in fibre optic production, fibre research and similar activities. This standard
181 describes the detailed procedures used to establish calibration of a CD test set.
182 Calibration of a CD test set is established by applying known artefacts or standards
183 (themselves calibrated to reference standards) to the CD test set and measuring its response.
184 Primarily the artefacts or standards used are as follows:
185 a) wavelength artefact(s) or traceable wavelength measuring instruments used to calibrate
186 the light source wavelength(s) used by the CD test set. This is to establish the correct
187 excitation wavelength for the system (the ‘x-axis’);
188 b) delay or dispersion artefact(s) used to calibrate the delay or dispersion response of the
189 CD test set (the ‘y-axis’);
190 c) Traceable chromatic dispersion reference fibre used to calibrate the CD test set. This
191 method allows a simultaneous calibration of the whole CD test set, including the
192 measurement of the delay or dispersion response of the CD test set as a function of
193 wavelength and also the internal data processing part. A proper selection of the type of
194 reference fibre is important, especially for an accurate calibration of the zero dipersion
195 wavelength.
196 Calibration can only be carried out using these artefacts; the use of a known standard fibre
197 (reference fibre described in c)) whose chromatic dispersion is known is recommended as the
198 fibre forms a stable source of known dispersion and may be used as a simple dispersion
199 artefact.

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200 If it is found that the CD test set measurement results have changed significantly compared to
201 the user requirements (i.e. the test set has drifted by more than the repeatability), then
202 adjustment may be carried out depending on the need.
203 In this document, the reference medium for wavelength and the velocity of light is assumed to
204 be in vacuum, and hence define the refractive index =1,0000000.
205

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206 CALIBRATION OF FIBRE OPTIC CHROMATIC DISPERSION
207 TEST SETS
208
209 1 Scope
210 This International Standard provides standard procedures for the calibration of optical fibre
211 chromatic dispersion (CD) test sets.
212 This standard is applicable to all types of CD test sets, with the exception that measurements
213 on multimode optical fibres are excluded.
214 The purpose of this standard is to define a standard procedure for calibrating optical fibre
215 chromatic dispersion (CD) test sets. The detailed calibration steps used vary according to the
216 measurement technique used in the CD test set.
217 Whilst it is acknowledged that chromatic dispersion also occurs in multimode fibre and this
218 fibre may be measured on many CD test sets, this standard will restrict discussion to single
219 mode fibre measurements applications only.
220 The purpose of the procedures outlined in this standard is to focus manufacturers and users
221 of CD test sets toward the reduction of measurement uncertainty in chromatic dispersion
222 determination in optical fibres under all applicable conditions. The procedures apply to
223 calibration laboratories and to the manufacturers or users of CD test sets for the purpose of
224 a) calibrating CD test sets;
225 b) evaluating the level of performance of the instrument.
226 Use of the procedures also allows correct evaluation of CD test set uncertainty, relative and
227 traceable to appropriate (for example, national) standards.
228 2 Normative references
229 The following documents are referred to in the text in such a way that some or all of their
230 content constitutes requirements of this document. For dated references, only the edition cited
231 applies. For undated references, the latest edition of the referenced document (including any
232 amendments) applies.
233 IEC 60050-731, International Electrotechnical Vocabulary (IEV) – Chapter 731: Optical fibre
234 communication

235 IEC 62129-1, Calibration of optical spectrum analyzers
236 3 Terms and definitions
237 For the purposes of this document, the terms and definitions contained in IEC 60050-731 and
238 the following apply.
239 ISO and IEC maintain terminological databases for use in standardization at the following
240 addresses:
241 • ISO Online browsing platform: available at https://www.iso.org/obp
242 • IEC Electropedia: available at http://www.electropedia.org/

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243 3.1
244 accredited calibration laboratory
245 calibration laboratory authorized by the appropriate national standards laboratory to issue
246 calibration certificates with a minimum specified uncertainty that demonstrate traceability to
247 national standards
248 3.2
249 adjustment
250 set of operations carried out on an instrument in order that it provides given indications
251 corresponding to given values of the measurand
252 3.3
253 artefact
254 device, instrument, or equipment used in the process of calibrating a CD test set for
255 wavelength, delay, or chromatic dispersion
256 3.4
257 calibration
258 set of operations that establish, under specified conditions, the relationship between the
259 values of quantities indicated by a measuring instrument and the corresponding values
260 realized by measurement standards
261 Note 1 to entry: The result of a calibration permits either the assignment of values of measurands to the
262 indications or the determination of corrections with respect to indications.
263 Note 2 to entry: A calibration may also determine other metrological properties such as the effect of influence
264 quantities.
265 Note 3 to entry: The result of a calibration may be recorded in a document, sometimes called a calibration
266 certificate or a calibration report.
267 Note 4 to entry: See also ISO/IEC Guide 99:2007, 2.39.
268 3.5
269 traceability chain
270 unbroken chain of comparison using standards (see Figure 1)
271
272 Figure 1 – Example of a traceability chain

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273 3.6
274 centroidal wavelength
275 power-weighted mean wavelength of a light source in vacuum
276 Note 1 to entry: For a continuous source spectrum, the centroidal wavelength λ in vacuum is defined by the
c
277 following integral, where the integration limits enclose the entire spectrum of the source. However, it is usually
278 sufficient to perform the integral or summation over the spectrum where the spectral density p(λ) or power P is
i
279 higher than 0,1 % of the maximum spectral density p(λ) or power P .:
i
280  λ = (1/ P ) × [ p(λ) × λ dλ]   (1)
c total
∫
281 where
282 P = p(λ) dλ is the total optical source power.
total
∫
283 For a spectrum consisting of i discrete lines, the centroidal wavelength in vacuum λ is defined as:
c
 
284   λ = (1/ P ) × pλ   (2)
 
c total ∑ i i
 
 i 
285 where
286 p(λ) is the spectral power spectral density of the source in W/nm;
287 λ is the centroidal wavelength in vacuum in nanometers;
c
th
288 λ is the i discrete line in nm;
i
289 p is the power levels at λ in W;
i i
=
290 P p is the total power in W.
i
total ∑
i
291 3.7
292 chromatic dispersion (CD) test sets
293 instrument capable of measuring the chromatic dispersion of a single mode fibre at various
294 wavelengths in the transmission windows of interest, typically the 1 310 nm and/or 1 550 nm
295 wavebands
296 3.8
297 correction offset
298 CO
299 number that is added to or subtracted from the measurement result of a CD test set to correct
300 for a known physical effect or deviation
301 3.9
302 instrument state
303 complete description of the measurement conditions and state of the CD test set during the
304 calibration process
305 Note 1 to entry: Typical parameters of the instrument state are the wavelength range in use, the data fit model (as
306 applicable), warm-up time, and other instrument settings.
307 3.10
308 measurement result
309 displayed or electrical output of any CD test set, in
–1 –1
310 • dispersion D in units of ps × nm × km ,
311 • lambda zero λ in units of nm,
0
–2 –1
312 • zero dispersion slope S in units of ps × nm × km ,
0

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313 after completing all actions suggested by the operating instructions, for example warm-up
314 3.11
315 national standard
316 standard recognized by a national decision to serve in a country as the basis for assigning
317 values to other standards of the quantity concerned
318 Note 1 to entry: For more information, see ISO/IEC Guide 99:2007, 5.3.
319 3.12
320 national standards laboratory
321 national metrology institute
322 laboratory which maintains the national standard
323 3.13
324 operating range
325 specified range of values of one of a set of operating conditions for which the uncertainty of a
326 measuring instrument is specified
327 3.14
328 reference standard
329 standard, generally having the highest metrological quality available at a given location or in a
330 given organization, from which measurements made therein are derived
331 Note 1 to entry: For more information, see ISO/IEC Guide 99:2007, 5.6.
332 3.15
333 scaling factor
334 SF
335 ratio of known standard values for a standard artefact to the values indicated by the CD test
336 set when no correction offsets are applied
337 Note 1 to entry: The factors can apply to wavelength, delay [dispersion] calibration, as well as to recorded zero
338 dispersion wavelength, slope and actual dispersion data values when using a calibrated reference fibre.
339 3.16
340 spectral bandwidth
341 full-width at half-maximum (FWHM) of th
...