IEC 62614-1:2020

IEC 62614-1 ®
Edition 1.0 2020-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Fibre optics – Multimode launch conditions –
Part 1: Launch condition requirements for measuring multimode attenuation

Fibronique – Conditions d’injection en multimodal –
Partie 1: Exigences des conditions d’injection pour la mesure de
l’affaiblissement en multimodal

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IEC 62614-1 ®
Edition 1.0 2020-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Fibre optics – Multimode launch conditions –

Part 1: Launch condition requirements for measuring multimode attenuation

Fibronique – Conditions d’injection en multimodal –

Partie 1: Exigences des conditions d’injection pour la mesure de

l’affaiblissement en multimodal

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.01 ISBN 978-2-8322-8958-7

– 2 – IEC 62614-1:2020 © IEC 2020
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Background on multimode launch conditions . 6
5 Test source launch . 7
5.1 General . 7
5.2 Encircled flux . 7
5.3 Encircled flux template illustration . 7
5.4 Encircled flux target for attenuation measurement . 8
5.5 Harmonization of multimode launch conditions to eliminate wavelength bias . 9
5.6 Uncertainties expectations . 10
5.7 Encircled flux limits . 10
5.8 Practical limitations of multimode launch conditions . 11
Bibliography . 12

Figure 1 – EF template illustration for 50 µm core fibre cabling at 850 nm . 8
Figure 2 – Wavelength comparison . 9

Table 1 – EF target for 50 µm core fibre at 850 nm . 8
Table 2 – EF target for 50 µm core fibre at 1 300 nm . 8
Table 3 – EF target for 62,5 µm fibre at 850 nm . 9
Table 4 – EF target for 62,5 µm fibre at 1 300 nm . 9
Table 5 – Attenuation, threshold tolerance and confidence level . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTICS – MULTIMODE LAUNCH CONDITIONS –

Part 1: Launch condition requirements for
measuring multimode attenuation

FOREWORD
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62614-1 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
This first edition cancels and replaces IEC 62614, published in 2010, and constitutes a technical
revision.
This edition includes the following significant technical changes with respect to IEC 62614:
a) increase of the value of the uncertainty attenuation variation coefficient Y for 50 µm core
fibre at 1 300 nm, due to launch conditions, to twice the previous value;
b) changes to 3.4, 5.6, including Table 5, and some references to remain consistent with
IEC 61280-4-1:2019;
c) changes to multimode fibre references to be consistent with IEC 60793-2-10:2019.

– 4 – IEC 62614-1:2020 © IEC 2020
The text of this International Standard is based on the following documents:
CDV Report on voting
86C/1625/CDV 86C/1654A/RVC
Full information on the voting for the approval of this International Standard 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 62614 series, published under the general title Fibre optics –
Multimode launch conditions, can be found on the IEC website.
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.
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.

FIBRE OPTICS – MULTIMODE LAUNCH CONDITIONS –

Part 1: Launch condition requirements for
measuring multimode attenuation

1 Scope
This part of IEC 62614 describes the launch condition requirements used for measuring
multimode attenuation in passive components and in installed cable plants.
In this document, the fibre types that are addressed include category A1-OMx, where x = 2, 3,
4 and 5 (50 µm/125 µm), and A1-OM1 (62,5 µm/125 µm) multimode fibres, as specified in
IEC 60793-2-10. The nominal test wavelengths detailed are 850 nm and 1 300 nm. This
document can be suitable for multimode attenuation measurements for other multimode
categories and/or other wavelengths, but the source condition for other categories and
wavelengths are not defined here.
The purpose of these requirements is as follows:
• to ensure consistency of field measurements when different types of test equipment are
used;
• to ensure consistency of factory measurements when different types of test equipment are
used;
• to ensure consistency of field measurements when compared with factory measurements.
This document describes launch condition requirements for optical attenuation using sources
with a controlled encircled flux (EF).
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 61280-1-4, Fibre optic communication subsystem test procedures – Part 1-4: General
communication subsystems – Light source encircled flux measurement method
3 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

– 6 – IEC 62614-1:2020 © IEC 2020
3.1
encircled flux
EF
fraction of cumulative near-field power to the total output power as a function of radial distance
from the optical centre of the core
3.2
multimode attenuation
attenuation pertaining to multimode fibres and/or multimode fibre components, systems and
subsystems
3.3
reference grade launch cord
launch cords constructed with a reference grade termination at the interface to the device under
test
3.4
reference grade termination
connector and plug with tightened tolerances terminated onto an optical fibre with tightened
tolerances such that the expected attenuation of a connection formed by mating two such
assemblies is lower and more repeatable than a standard-grade termination
Note 1 to entry: An adapter, required to assure the reduced attenuation, may be considered part of the reference
grade termination where required by the test configuration.
Note 2 to entry: IEC 61755-6-2 defines reference grade terminations for 50/125 µm fibre.
4 Background on multimode launch conditions
There have been a wide range of launch conditions used for testing multimode fibre components
and systems. Light sources, typically used in measuring attenuation, can produce varying modal
distributions when launched into multimode fibre. These differing modal distributions, combined
with the differential mode attenuation (DMA) inherent in most multimode components,
commonly cause measurement variations when measuring attenuation of multimode
components. For example, attenuation measurement variations can occur when two similar light
sources or different launch cords are used.
Legacy (LED based) applications had a wide power budget, which in most cases masked the
variance in results between the factory and field measurement. As technology has evolved, the
system requirements for attenuation have become more stringent. Demanding application
requirements are driving the need for accurate and reproducible multimode attenuation
measurements over a variety of field-test instruments. Attenuation measurement experiments,
with different instruments having the same standards compliant set up, produce measurement
variations that are induced by their differing launch conditions.
Experts have concluded that the launch condition should be expressed at the interface between
the test instrument launch cord and the terminated fibre to be tested. That is, the launch
condition should be based in part on the measured near field at the output of the launch cord.
The key to making reproducible attenuation measurements across various sources is to
narrowly constrain the range of power distribution at large radii so that all compliant sources
produce closely agreeing attenuation measurement results. This is because the variation in the
allowed power distribution at large radii across different sources translates directly into
variability of attenuation measurements. Smaller power variations enable more reproducible
attenuation measurements.
5 Test source launch
5.1 General
The source launch conditions are described at the output of the reference grade launch cord. It
is expected that the source and launch cord, as supplied, have been verified by the test
equipment manufacturer to produce the specified launch measured according to
IEC 61280-1-4. For reference grade fibre, core diameter tolerances of ±0,7 µm have been
evaluated with some success. Variance of other parameters, such as numerical aperture and
core concentricity, need more study.
5.2 Encircled flux
The EF shall be determined from the near field measurement of the light coming from the end
of the reference grade launch cord in accordance with IEC 61280-1-4.
The measured near field result is a function of the near field profile, I(r), of radius r, away from
the optical centre of the core, and the edge of the near field profile, R, which is used to generate
the EF function as shown in Formula (1):
r
xI x dx
( )
∫
(1)
EF r =
( )
R
xI x dx
( )
∫
5.3 Encircled flux template illustration
An illustration of an EF template is shown in Figure 1. A target EF value for a set of particular
radial control points is defined. Upper and lower limit of EF values for a set of particular radial
control points may also be defined. A compliant launch is a launch that falls within the template
at the particular radial control points.

– 8 – IEC 62614-1:2020 © IEC 2020

Figure 1 – EF template illustration for 50 µm core fibre cabling at 850 nm
5.4 Encircled flux target for attenuation measurement
For the purposes of this document, the EF requirement is defined as a target EF value for a set
of particular radial control points for each of four combinations of fibre core diameter and
wavelength, as tabulated in Table 1 through Table 4.
Table 1 – EF target for 50 µm core fibre at 850 nm
Radial offset Target
µm
10 0,335 0
15 0,655 0
20 0,919 3
22 0,975 1
Table 2 – EF target for 50 µm core fibre at 1 300 nm
Radial offset Target
µm
10 0,336 6
15 0,656 7
20 0,918 6
22 0,972 8
Table 3 – EF target for 62,5 µm fibre at 850 nm
Radial offset Target
µm
10 0,210 9
15 0,439 0
20 0,692 3
26 0,935 0
28 0,978 3
Table 4 – EF target for 62,5 µm fibre at 1 300 nm
Radial offset Target
µm
10 0,211 9
15 0,440 9
20 0,694 5
26 0,935 7
28 0,978 2
5.5 Harmonization of multimode launch conditions to eliminate wavelength bias
Efforts were taken to harmonize the expected component attenuation at 850 nm and 1 300 nm
wavelengths for a given fibre core diameter. This was accomplished by adjustment of the
850 nm and 1 300 nm EF targets to produce comparable extrinsic component attenuation. An
example of matching the attenuation characteristics at the two wavelengths is illustrated in
Figure 2. This elimination of bias provides an opportunity to ensure dual wavelength compliance
of a passive component or short cable plant link using a single source condition.

Figure 2 – Wavelength comparison

– 10 – IEC 62614-1:2020 © IEC 2020
5.6 Uncertainties expectations
The limits for encircled flux templates are derived from a target near field and a set of boundary
conditions designed to constrain the variation in attenuation measurement to ±Y times the dB
attenuation or ±X dB, whichever is largest. The reliability of the possible variation of attenuation
measurement X or Y is another parameter called β.
The variable X is a tolerance threshold. The variable Y is the coefficient of attenuation variation.
These variables X, Y, and β vary with optical fibre core size and wavelength according to the
values in Table 5. They need to be considered for measurement uncertainties calculation.
Please refer to IEC TR 61282-14 for more details.
Table 5 – Attenuation, threshold tolerance and confidence level
Optical fibre Attenuation
nominal core Wavelength Threshold, X variation Reliability level, β
diameter coefficient, Y
µm nm dB
50 850 0,08 0,10 0,368
50 1 300 0,12 0,20 0,333
62,5 850 0,10 0,10 0,170
62,5 1 300 0,15 0,10 0,030
Only coupling attenuations are taken into account for these attenuation values.
This table is referenced to nominal core diameter. Control of the core diameter of the optical fibre in the actual
launch cord to tight tolerances (e.g., ± 0,7 µm) is important to ensure uncertainties expectations.
Re-evaluation of uncertainties has determined the attenuation variation coefficient Y to be 0,20 after adjustment
of 1 300 nm EF targets to produce comparable extrinsic component attenuation for 50 µm fibres and 1 300 nm.
Δu
i
In IEC TR 61282-14, beta parameter, β, is considered as uncertainty of the uncertainties, , to calculate the
u
i
effective degree of freedom and then calculate expanded uncertainty of attenuation uncertainties.

5.7 Encircled flux limits
Upper and lower bounds (i.e. tolerance range) of the encircled flux are chosen to constrain the
measured attenuation variation and are established around a target. These upper and lower
bounds can be determined by modelling the mode coupling through various concatenated
connections (the number of connections and their lateral offset magnitude chosen to be relevant
to the topologies of installed cabling) while searching for all launch conditions that constrain
the attenuation variation to within specific values.
The limits and thresholds differ for each of the four combinations of core size and wavelength
specified in 5.4. The differences are a result of accommodating, to some degree, the variation
of the sources sampled experimentally, the desire to allow the application of a common mode
conditioner to both 850 nm and 1 300 nm nominal wavelength sources, and the recognition that
the tightest constraints are needed for 850 nm applications operating on 50 µm core diameter
fibre.
The limits are chosen to constrain attenuation variation, relative to being exactly on the target
launch, to be no greater than the larger of the attenuation variation coefficient, or the threshold
value. For example, at 850 nm and 50 µm, the threshold value of 0,08 dB means that the
attenuation variation is expected to be within ±10 % for attenuation equal to or greater than
0,8 dB, and within 0,08 dB for attenuation less than 0,8 dB.

5.8 Practical limitations of multimode launch conditions
For field test equipment using a single optical port that launches two wavelengths, a test cord
that is conditioned by a mandrel may not allow an alignment on the target for both wavelengths
simultaneously. Should this be the case, the use of the same mandrel for both wavelengths will
reduce the margin for compliance within the templates and add uncertainty.
Due to the effect of variations in source wavelength, fibre core size and numerical aperture,
mandrel tolerances, temperature changes, other physical variations, and the measurement
equipment itself, launch conditions at the time of factory calibration will not be identical in the
field should any variable change. The use of attenuation artefacts described in Annex J of
IEC 61280-4-1:2019 can help ensure that the equipment produces a launch condition that
performs acceptably.
Although this document is not intended to grant compliance to equipment that predates its
publication, it may be possible to bring such equipment into compliance with the use of an
external mode conditioner designed for this purpose. Unless the equipment, its launch cords,
and the external mode conditioner are verified to produce the intended launch conditions, this
approach will be an additional source of uncertainty, but that uncertainty may be less than
without the use of the external mode conditioner.

– 12 – IEC 62614-1:2020 © IEC 2020
Bibliography
IEC 60793-2-10:2019, Optical fibres – Part 2-10: Product specifications – Sectional
specification for category A1 multimode fibres
IEC 61280-4-1:2019, Fibre-optic communication subsystem test procedures – Part 4-1:
Installed cabling plant – Multimode attenuation measurem
...