IEC 61280-2-8:2021

Fibre optic communication subsystem test procedures - Part 2-8: Digital systems - Determination of low BER using Q-factor measurements

IEC 61280-2-8:2021 specifies two main methods for the determination of low BER values by making accelerated measurements. These include the variable decision threshold method (Clause 5) and the variable optical threshold method (Clause 6). In addition, a third method, the sinusoidal interference method, is described in Annex B. This second edition cancels and replaces the first edition published in 2003. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- correction of errors in Formula (8) in 5.5.2 and in a related formula in 5.5.3;
- correction of errors in the references to clauses, subclauses, figures, procedures, and in the Bibliography;
- alignment of the terms and definitions in 3.1 with those in IEC 61281-1.

Procédures d'essai des sous-systèmes de télécommunication fibroniques - Partie 2-8: Systèmes numériques - Détermination de faibles valeurs de BER en utilisant des mesures du facteur Q

L'IEC 61280-2-8:2021 spécifie deux méthodes principales permettant de déterminer de faibles valeurs de BER en réalisant des mesures accélérées. Ces méthodes utilisent soit un seuil de décision variable (Article 5), soit un seuil optique variable (Article 6). De plus, une troisième méthode fondée sur le brouillage sinusoïdal est décrite à l’Annexe B. Cette deuxième édition annule et remplace la première édition parue en 2003. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente:
- correction d’erreurs dans la Formule (8) en 5.5.2 et dans une formule associée en 5.5.3;
- correction d’erreurs dans les références aux articles, paragraphes, figures et procédures, ainsi que dans la bibliographie;
- alignement des termes et définitions en 3.1 sur ceux de l’IEC 61281-1.

General Information

• Status: Published
• Publication Date: 01-Mar-2021
• ICS: 33.180.10 - Fibres and cables
• Technical Committee: SC 86C - Fibre optic systems and active devices
• Drafting Committee: WG 1 - TC 86/SC 86C/WG 1
• Current Stage: PPUB - Publication issued
• Start Date: 26-Mar-2021
• Completion Date: 02-Mar-2021

Relations

• Revises: IEC 61280-2-8:2003 - Fibre optic communication subsystem test procedures - Digital systems - Part 2-8: Determination of low BER using Q-factor measurements
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61280-2-8 ®
Edition 2.0 2021-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Fibre optic communication subsystem test procedures – Digital systems –
Part 2-8: Digital systems – Determination of low BER using Q-factor
measurements
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
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IEC 61280-2-8 ®
Edition 2.0 2021-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Fibre optic communication subsystem test procedures – Digital systems –

Part 2-8: Digital systems – Determination of low BER using Q-factor

measurements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.10 ISBN 978-2-8322-9530-4

– 2 – IEC 61280-2-8:2021 RLV © IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, and abbreviated terms . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms . 7
4 Measurement of low bit-error ratios . 7
4.1 General considerations . 7
4.2 Background to Q-factor . 9
5 Variable decision threshold method . 11
5.1 Overview. 11
5.2 Apparatus . 14
5.3 Sampling and specimens . 14
5.4 Procedure . 15
5.5 Calculations and interpretation of results . 16
5.5.1 Sets of data . 16
5.5.2 Convert BER using inverse error function . 17
5.5.3 Linear regression . 18
5.5.4 Standard deviation and mean . 19
5.5.5 Optimum decision threshold . 20
5.5.6 BER optimum decision threshold . 20
5.5.7 BER non-optimum decision threshold . 20
5.5.8 Error bound . 20
5.6 Test documentation . 20
5.7 Specification information . 21
6 Variable optical threshold method . 21
6.1 Overview. 21
6.2 Apparatus . 21
6.3 Items under test . 22
6.4 Procedure for basic optical link . 22
6.5 Procedure for self-contained system . 22
6.6 Evaluation of results . 23
Annex A (normative) Calculation of error bound in the value of Q . 25
Annex B (informative) Sinusoidal interference method . 27
B.1 Introduction Overview . 27
B.2 Apparatus . 27
B.3 Sampling and specimens . 27
B.4 Procedure . 28
B.4.1 Optical sinusoidal interference method . 28
B.4.2 Electrical sinusoidal interference method . 29
B.5 Calculations and interpretation of results . 30
B.5.1 Mathematical analysis . 30
B.5.2 Extrapolation . 30
B.5.3 Expected results . 31
B.6 Documentation . 32

B.7 Specification information . 32
Bibliography . 33

Figure 1 – Sample eye diagram showing patterning effects . 10
Figure 2 – More accurate measurement technique using a DSO that samples noise
statistics between eye centres . 10
Figure 3 – Bit error ratio as a function of decision threshold level . 12
Figure 4 – Plot of Q-factor as a function of threshold voltage . 13
Figure 5 – Set-up for the variable decision threshold method . 15
Figure 6 – Set-up of initial threshold level (approximately at the centre of the eye) . 15
Figure 7 – Effect of optical bias . 21
Figure 8 – Set-up for optical link or device test . 22
Figure 9 – Set-up for system test . 23
Figure 10 – Extrapolation of log BER as a function of bias . 24
Figure B.1 – Set-up for the sinusoidal interference method by optical injection . 28
Figure B.2 – Set-up for the sinusoidal interference method by electrical injection . 30
Figure B.3 – BER result from the sinusoidal interference method (data points and
extrapolated line) . 31
Figure B.4 – BER versus optical power for three methods . 32

Table 1 – Mean time for the accumulation of 15 errors as a function of BER and bit rate . 7
Table 2 – BER as a function of threshold voltage . 17
Table 3 – f as a function of D . 18
i i
Table 4 – Values of linear regression constants . 19
Table 5 – Mean and standard deviation . 19
Table 6 – Example of optical bias test . 23
Table B.1 – Results for sinusoidal injection . 29

– 4 – IEC 61280-2-8:2021 RLV © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC COMMUNICATION SUBSYSTEM TEST PROCEDURES –
DIGITAL SYSTEMS –
Part 2-8: Digital systems –
Determination of low BER using Q-factor measurements

FOREWORD
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...

IEC 61280-2-8 ®
Edition 2.0 2021-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Fibre optic communication subsystem test procedures –
Part 2-8: Digital systems – Determination of low BER using Q-factor
measurements
Procédures d’essai des sous-systèmes de télécommunications fibroniques –
Partie 2-8: Systèmes numériques – Détermination de faibles valeurs de BER en
utilisant des mesures du facteur Q

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
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International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC online collection - oc.iec.ch
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variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
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Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
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IEC 61280-2-8 ®
Edition 2.0 2021-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Fibre optic communication subsystem test procedures –

Part 2-8: Digital systems – Determination of low BER using Q-factor

measurements
Procédures d’essai des sous-systèmes de télécommunications fibroniques –

Partie 2-8: Systèmes numériques – Détermination de faibles valeurs de BER en

utilisant des mesures du facteur Q

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.10 ISBN 978-2-8322-9497-0

– 2 – IEC 61280-2-8:2021 © IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, and abbreviated terms . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms . 7
4 Measurement of low bit-error ratios . 7
4.1 General considerations . 7
4.2 Background to Q-factor . 8
5 Variable decision threshold method . 10
5.1 Overview. 10
5.2 Apparatus . 13
5.3 Sampling and specimens . 13
5.4 Procedure . 13
5.5 Calculations and interpretation of results . 15
5.5.1 Sets of data . 15
5.5.2 Convert BER using inverse error function . 16
5.5.3 Linear regression . 17
5.5.4 Standard deviation and mean . 18
5.5.5 Optimum decision threshold . 18
5.5.6 BER optimum decision threshold . 18
5.5.7 BER non-optimum decision threshold . 19
5.5.8 Error bound . 19
5.6 Test documentation . 19
5.7 Specification information . 19
6 Variable optical threshold method . 19
6.1 Overview. 19
6.2 Apparatus . 20
6.3 Items under test . 20
6.4 Procedure for basic optical link . 20
6.5 Procedure for self-contained system . 21
6.6 Evaluation of results . 22
Annex A (normative) Calculation of error bound in the value of Q . 24
Annex B (informative) Sinusoidal interference method . 26
B.1 Overview. 26
B.2 Apparatus . 26
B.3 Sampling and specimens . 26
B.4 Procedure . 27
B.4.1 Optical sinusoidal interference method . 27
B.4.2 Electrical sinusoidal interference method . 28
B.5 Calculations and interpretation of results . 29
B.5.1 Mathematical analysis . 29
B.5.2 Extrapolation . 29
B.5.3 Expected results . 30
B.6 Documentation . 31

B.7 Specification information . 31
Bibliography . 32

Figure 1 – Sample eye diagram showing patterning effects . 9
Figure 2 – More accurate measurement technique using a DSO that samples noise
statistics between eye centres . 10
Figure 3 – Bit error ratio as a function of decision threshold level . 11
Figure 4 – Plot of Q-factor as a function of threshold voltage . 12
Figure 5 – Set-up for the variable decision threshold method . 14
Figure 6 – Set-up of initial threshold level (approximately at the centre of the eye) . 14
Figure 7 – Effect of optical bias . 20
Figure 8 – Set-up for optical link or device test . 21
Figure 9 – Set-up for system test . 21
Figure 10 – Extrapolation of log BER as a function of bias . 23
Figure B.1 – Set-up for the sinusoidal interference method by optical injection . 27
Figure B.2 – Set-up for the sinusoidal interference method by electrical injection . 29
Figure B.3 – BER result from the sinusoidal interference method (data points and
extrapolated line) . 30
Figure B.4 – BER versus optical power for three methods . 31

Table 1 – Mean time for the accumulation of 15 errors as a function of BER and bit rate . 7
Table 2 – BER as a function of threshold voltage . 16
Table 3 – f as a function of D . 17
i i
Table 4 – Values of linear regression constants . 18
Table 5 – Mean and standard deviation . 18
Table 6 – Example of optical bias test . 22
Table B.1 – Results for sinusoidal injection . 28

– 4 – IEC 61280-2-8:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
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