Fibre optic communication system design guidelines - Part 14: Determination of the uncertainties of attenuation measurements in fibre plants

IEC TR 61282-14:2019 is available as IEC TR 61282-14:2019 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC TR 61282-14:2019 which is a Technical Report, establishes the detailed analysis and calculation of the uncertainties related to the measurement of the attenuation of both multimode and single mode optical fibre cabling using optical light sources and power meters. This second edition cancels and replaces the first edition published in 2016. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- in the title: replacement of "guide" by "guidelines";
- text adaptation to allow both standard grade B and reference grade connectors for termination of test cords;
- addition of values needed for calculation of uncertainties, when standard grade connectors are used, to Annex D;
- correction of minor inconsistencies in Equation (18) and after.
Keywords: measurement uncertainty of the attenuation of fibre optic cabling

General Information

Status
Published
Publication Date
18-Jul-2019
Current Stage
PPUB - Publication issued
Completion Date
19-Jul-2019
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IEC TR 61282-14
Edition 2.0 2019-07
TECHNICAL
REPORT
colour
inside
Fibre optic communication system design guidelines –
Part 14: Determination of the uncertainties of attenuation measurements in fibre
plants
IEC TR 61282-14:2019-07(en)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC TR 61282-14
Edition 2.0 2019-07
TECHNICAL
REPORT
colour
inside
Fibre optic communication system design guidelines –
Part 14: Determination of the uncertainties of attenuation measurements in fibre
plants
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.01 ISBN 978-2-8322-7069-1

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 61282-14:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms, definitions and abbreviated terms ........................................................................ 8

3.1 Terms and definitions .............................................................................................. 8

3.2 Abbreviated terms ................................................................................................. 10

4 Overview of uncertainty ................................................................................................. 10

4.1 What is uncertainty? ............................................................................................. 10

4.2 Origin of uncertainties ........................................................................................... 11

4.3 What may not be considered as uncertainty? ........................................................ 11

5 Fibre cabling attenuation measurement ......................................................................... 11

5.1 Test methods ........................................................................................................ 11

5.2 Sources of uncertainty to be considered ............................................................... 11

5.2.1 Analysis ......................................................................................................... 11

5.2.2 Uncertainties due to the environment ............................................................. 14

5.2.3 Uncertainties due to operator skills ................................................................ 14

5.2.4 Uncertainties due to test methods .................................................................. 14

5.2.5 Uncertainties due to measuring instruments .................................................. 14

5.2.6 Uncertainties due to the setup ....................................................................... 16

5.2.7 Uncertainties due to cabling........................................................................... 16

6 Uncertainties estimation ................................................................................................ 17

6.1 Measurement model.............................................................................................. 17

6.2 Accumulation of uncertainties ............................................................................... 19

7 General representation of the equation using sensitivity coefficients .............................. 19

8 Calculation .................................................................................................................... 23

8.1 Combined standard uncertainty ............................................................................. 23

8.2 Expanded uncertainty ........................................................................................... 23

8.3 Determination of the coverage factor k .................................................................. 23

8.3.1 General approach .......................................................................................... 23

8.3.2 Discussion ..................................................................................................... 23

8.3.3 Typical values of degree of freedom .............................................................. 24

Annex A (informative) Mathematical basis............................................................................ 25

A.1 General ................................................................................................................. 25

A.2 Type A evaluation of uncertainty ........................................................................... 25

A.3 Type B evaluation of uncertainty ........................................................................... 25

A.4 Determining the combined standard uncertainty .................................................... 26

A.5 Reporting .............................................................................................................. 27

Annex B (informative) Test methods .................................................................................... 28

B.1 Test methods as per IEC 61280-4-1 and 61280-4-2 .............................................. 28

B.1.1 General ......................................................................................................... 28

B.1.2 Measurement configuration ............................................................................ 28

B.1.3 One-cord reference configuration .................................................................. 28

B.1.4 Two-cord reference configuration .................................................................. 29

B.1.5 Three-cord reference configuration ................................................................ 29

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IEC TR 61282-14:2019 © IEC 2019 – 3 –

B.2 Test methods defined in ISO/IEC 14763-3:2014 .................................................... 29

B.2.1 General ......................................................................................................... 29

B.2.2 Channels ....................................................................................................... 30

B.2.3 Links.............................................................................................................. 31

Annex C (informative) Uncertainties evaluation .................................................................... 32

C.1 Type A uncertainties ............................................................................................. 32

C.1.1 General ......................................................................................................... 32

C.1.2 Evaluation of optical source instability and associated uncertainties .............. 32

C.2 Type B uncertainties ............................................................................................. 32

C.2.1 General ......................................................................................................... 32

C.2.2 Evaluation of the power meter noise .............................................................. 32

C.2.3 Elements to be considered for power meter stability analysis ......................... 33

C.2.4 Evaluation of the centre wavelength dependence .......................................... 33

C.2.5 Spectral width dependence ............................................................................ 35

C.2.6 Evaluation of the uncertainties due to MM launch conditions ......................... 35

C.2.7 Evaluation of the PDL .................................................................................... 36

C.2.8 Uncertainty of absolute power measurement ................................................. 37

Annex D (informative) Typical values of uncertainties .......................................................... 38

Annex E (informative) Linear to dB scale conversion of uncertainties ................................... 40

E.1 Definition of decibel .............................................................................................. 40

E.2 Conversion of relative uncertainties ...................................................................... 40

Bibliography .......................................................................................................................... 41

Figure 1 – Fishbone analysis ................................................................................................ 13

Figure 2 – Measurement model ............................................................................................. 17

Figure B.1 – Measurement configuration ............................................................................... 28

Figure B.2 – One-cord reference measurement ..................................................................... 28

Figure B.3 – Two-cord reference measurement ..................................................................... 29

Figure B.4 – Three-cord reference measurement .................................................................. 29

Figure B.5 – Measurement on channel .................................................................................. 30

Figure B.6 – Channel reference measurement ...................................................................... 30

Figure B.7 – Link measurement configuration ....................................................................... 31

Figure B.8 – Link reference measurement ............................................................................. 31

Figure C.1 – Typical spectral response of a fibre .................................................................. 34

Figure C.2 – Uncertainties due to the launch conditions for a given loss ............................... 36

Table 1 – Source of uncertainty (raw list) .............................................................................. 12

Table 2 – Uncertainties due to measuring instruments .......................................................... 15

Table 3 – Uncertainties due to the setup ............................................................................... 16

Table 4 – Uncertainties due to cabling .................................................................................. 16

Table 5 – Sensitivity coefficients for IEC 61280-4-1 and IEC 61280-4-2 methods .................. 21

Table 6 – Sensitivity coefficients for ISO/IEC 14763-3:2014 methods.................................... 22

Table 7 – Values of k for different values of ν .................................................................... 24

Table 8 – Typical values of ν ............................................................................................... 24

Table C.1 – Spectral attenuation coefficients ........................................................................ 34

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– 4 – IEC TR 61282-14:2019 © IEC 2019

Table C.2 – Sensitivity coefficients ....................................................................................... 35

Table D.1 – Typical values of uncertainties ........................................................................... 39

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IEC TR 61282-14:2019 © IEC 2019 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC COMMUNICATION
SYSTEM DESIGN GUIDELINES –
Part 14: Determination of the uncertainties
of attenuation measurements in fibre plants
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

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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

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

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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.

The main task of IEC technical committees is to prepare International Standards. However, a

technical committee may propose the publication of a technical report when it has collected

data of a different kind from that which is normally published as an International Standard, for

example "state of the art".

IEC 61282-14, which is a Technical Report, has been prepared by subcommittee 86C: Fibre

optic systems and active devices, of IEC technical committee 86: Fibre optics.

This publication contains an attached file titled "Supplemental Data for Section 8" in the form

of an Excel spread sheet. This file is intended to be used as a complement and does not form

an integral part of the standard.

This second edition cancels and replaces the first edition published in 2016. This edition

constitutes a technical revision.
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– 6 – IEC TR 61282-14:2019 © IEC 2019

This edition includes the following significant technical changes with respect to the previous

edition:
a) in the title: replacement of "guide" by "guidelines";

b) text adaptation to allow both standard grade B and reference grade connectors for

termination of test cords;

c) addition of values needed for calculation of uncertainties, when standard grade connectors

are used, to Annex D;
d) correction of minor inconsistencies in Equation (18) and after.
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
86C/1572/DTR 86C/1584/RVDTR

Full information on the voting for the approval of this Technical Report can be found in the

report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 61282 series, published under the general title Fibre optic

communication system design guides, can be found on the IEC website.

Future standards in this series will carry the new general title as cited above. Titles of existing

standards in this series will be updated at the time of the next edition.

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

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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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IEC TR 61282-14:2019 © IEC 2019 – 7 –
INTRODUCTION

The determination of the uncertainty of every measurement is a key activity, which should be

performed by applying dedicated methods as extensively presented in reference documents

such as ISO/IEC Guide 98-3:2008, Guide to the uncertainty of measurement (GUM).

This document shows a practical application of these methods for the determination of the

measurement uncertainty of the attenuation of fibre optic cabling using optical light sources and

power meters as defined in IEC 61280-4-1 and IEC 61280-4-2.

It includes the review of all contributing factors to uncertainty (such as launch conditions,

spectral width, stability of source, power meter polarization, resolution, linearity, quality of test

cord connectors) to determine the overall measurement uncertainty. This part of IEC 61282

applies to the measurement of single mode or multimode fibres without restrictions to the fibre

parameters, including mode field diameter, core diameter and numerical aperture. However,

numerical values given in Clause C.2 and typical values given in Annex D are not valid for

multimode fibres types A2, A3 and A4.

The list of uncertainties presented in this document is related to this particular application and

should be reconsidered if measurement conditions are not compliant to measurement

requirements defined by IEC 61280-4-1 and IEC 61280-4-2.

The reference document for general uncertainty calculations is ISO/IEC Guide 98-3:2008, and

this document does not intend to replace it; it only represents an example and should be used

in conjunction with ISO/IEC Guide 98-3:2008. A brief introduction to the determination of

measurement uncertainty according to ISO/IEC Guide 98-3:2008 is given in Annex A.

This document is associated with a calculation spreadsheet (Excel) containing practical

calculations.
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– 8 – IEC TR 61282-14:2019 © IEC 2019
FIBRE OPTIC COMMUNICATION
SYSTEM DESIGN GUIDELINES –
Part 14: Determination of the uncertainties
of attenuation measurements in fibre plants
1 Scope

This part of IEC 61282, which is a Technical Report, establishes the detailed analysis and

calculation of the uncertainties related to the measurement of the attenuation of both multimode

and single mode optical fibre cabling using optical light sources and power meters.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document (including any

amendments) applies.

IEC 61280-4-1:2009, Fibre-optic communication subsystem test procedures – Part 4-1:

Installed cable plant – Multimode attenuation measurement

IEC 61280-4-2:2014, Fibre-optic communication subsystem test procedures – Part 4-2:

Installed cable plant – Single-mode attenuation and optical return loss measurement

ISO/IEC Guide 98-3:2008, Uncertainty of measurement – Part 3: Guide to the expression of

uncertainty in measurement (GUM:1995)
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1.1
attenuation

reduction of optical power induced by transmission through a medium such as cabling

L = 10 × log (P /P )
dB 10 in out
where
P and P are the power, typically measured in mW, into and out of the cabling
in out
Note 1 to entry: Attenuation is expressed in dB.
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IEC TR 61282-14:2019 © IEC 2019 – 9 –
3.1.2
calibration

set of operations that establish, under specified conditions, the relationship between the values

of quantities indicated by a measuring instrument and the corresponding values realized by

standards
3.1.3
encircled flux

fraction of the radial-weighted cumulative near field power to the total radial-weighted output

power as a function of radial distance from the optical centre of the core
3.1.4
measurement repeatability
measurement precision under a set of repeatability conditions of measurement
3.1.5
measurement reproducibility
reproducibility
measurement precision under reproducibility conditions of measurement
3.1.6
polarization dependent loss
PDL

maximum variation of attenuation to a variation of the state of polarization (SOP) over all the

SOPs
Note 1 to entry: PDL is expressed in dB.
3.1.7
nonlinearity

relative difference, for a power meter, between the response at a given power P and the

response at a reference power P :
rP( )
nl −1
P/ P
( )
If expressed in decibels, the nonlinearity is:
( )
NL 10×log (dB)
PP/ 10
( )
Note 1 to entry: The nonlinearity is equal to zero at the reference power.
3.1.8
uncertainty of measurement
quantified doubt about the result of a measurement
3.1.9
stability

ability of a measuring instrument to keep its performance characteristics within a specified

range during a specified time interval, all other conditions being the same
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– 10 – IEC TR 61282-14:2019 © IEC 2019
3.1.10
repeatability condition

condition of measurement that includes the same measurement procedure, same operators,

same measuring system, same operating conditions and same location, and replicates

measurements on the same or similar objects over a short period of time
3.1.11
reproducibility condition

condition of measurement that includes different locations, operators, measuring systems, and

replicate measurements on the same or similar objects
3.1.12
standard uncertainty
uncertainty of a measurement result expressed as a standard deviation
Note 1 to entry: For further information, see ISO/IEC Guide 98-3.
3.1.13
type A uncertainty

type of uncertainty obtained by a statistical analysis of a series of observations, such as when

evaluating certain random effects of measurement
Note 1 to entry: See Annex A and ISO/IEC Guide 98-3.
3.1.14
type B uncertainty

type of uncertainty obtained by means other than a statistical analysis of observations, for

example an estimation of probable sources of uncertainty, such as when evaluating systematic

effects of measurement
Note 1 to entry: See Annex A and ISO/IEC Guide 98-3.
3.2 Abbreviated terms
APC angled physical contact (description of connector style)
CW continuous wave
LSPM light source power meter
OPM optical power meter
NA numerical aperture
PC physical contact (description of connector style that is not angled)
4 Overview of uncertainty
4.1 What is uncertainty?

According to ISO/IEC Guide 98-3:2008 (GUM), the uncertainty of a measurement is the

quantified doubt that exists about the result of any measurement. For every measurement, even

the most careful, there is always a margin of doubt.

For example, when measuring the attenuation of fibre optic cabling, the operator may observe

a variation of the displayed power level on the power meter and be unable to know which value

should be recorded. This variation of the displayed value is an element of doubt regarding the

result of the measurement.
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IEC TR 61282-14:2019 © IEC 2019 – 11 –
4.2 Origin of uncertainties

Uncertainties come from measurement devices, the item to be measured, the measurement

process, operator skills, references used, and the environment.
4.3 What may not be considered as uncertainty?

Unknown parameters that contribute directly or indirectly to the quantity to be measured cannot

be considered as uncertainties. For example, when measuring a cabling, mode field diameter

or numerical aperture of different fibres of cabling are unknown; however, mismatch of these

parameters causes the measured attenuation.

Also, poor knowledge of measurement conditions generates uncertainties but is not directly an

uncertainty. A common example is the wavelength of the optical source: if the wavelength of

the source is known with an uncertainty smaller than 1 nm, the measurement condition can be

specified precisely. Conversely, if the wavelength of the source is known to be within a range

of 40 nm, the possible variation of the attenuation of the device under test should be estimated

based on the typical variation of attenuation over the wavelength range for a given length of

fibre.
5 Fibre cabling attenuation measurement
5.1 Test methods

Three attenuation test methods use an optical light source and power meter (LSPM) to measure

input and output power levels of the cabling under test to determine the attenuation. These

methods are designated respectively, one-cord, three-cord and two-cord method.

The main functional difference between these methods is the way the input power level, known

as the reference power level (P ), is measured (see Annex B).
...

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