IEC 62614:2010

IEC 62614 ®
Edition 1.0 2010-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Fibre optics – Launch condition requirements for measuring multimode
attenuation
Fibres optiques – Exigences des conditions d’injection pour la mesure de
l’affaiblissement en multimodal

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IEC 62614 ®
Edition 1.0 2010-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Fibre optics – Launch condition requirements for measuring multimode
attenuation
Fibres optiques – Exigences des conditions d’injection pour la mesure de
l’affaiblissement en multimodal

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
M
CODE PRIX
ICS 33.180.01 ISBN 978-2-88912-071-0
– 2 – 62614 © IEC:2010
CONTENTS
FOREWORD.0H3
1 Scope.1H5
2 Normative references.2H5
3 Terms and definitions .3H5
4 Background on multimode launch conditions .4H6
5 Test source launch .5H7
5.1 General .6H7
5.2 Encircled flux.7H7
5.3 Encircled flux template illustration.8H7
5.4 Encircled flux target for attenuation measurement.9H8
5.5 Harmonisation of multimode launch conditions to eliminate wavelength bias.10H9
5.6 Limitations on multimode launch conditions.11H10
5.7 Encircled flux limits.12H10
5.8 Practical limitations of multimode launch conditions .13H10
Bibliography .14H12

Figure 1 – EF template illustration .15H8
Figure 2 – Wavelength comparison .16H9

Table 1 – EF target for 50 μm core fibre at 850 nm .17H8
Table 2 – EF target for 50 μm core fibre at 1 300 nm .18H8
Table 3 – EF target for 62,5 μm fibre at 850 nm.19H9
Table 4 – EF target for 62,5 μm fibre at 1 300 nm.20H9
Table 5 – Tolerance threshold .21H10

62614 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTICS –
LAUNCH CONDITION REQUIREMENTS
FOR MEASURING MULTIMODE ATTENUATION

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
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International Standard IEC 62614 has been prepared by IEC technical committee 86: Fibre
optics.
This standard cancels and replaces IEC/PAS 62614, published in 2009. This first edition
constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
86/367/FDIS 86/368/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – 62614 © IEC:2010
The committee has decided that the contents of this publication will remain unchanged until the
stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to
the specific publication. At this date, the publication 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.

62614 © IEC:2010 – 5 –
FIBRE OPTICS –
LAUNCH CONDITION REQUIREMENTS
FOR MEASURING MULTIMODE ATTENUATION

1 Scope
This International Standard describes the launch condition requirements used for measuring
multimode attenuation in passive components and in installed cable plants.
In this standard, the fibre types that are addressed include category A1a (50 μm /125 μm) and
A1b (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 standard may 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 standard describes launch condition requirements for optical attenuation using sources
with a controlled encircled flux (EF).
2 Normative references
The following referenced documents are indispensable for the application 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 60793-2-10, Optical fibres – Part 2-10: Product specifications – Sectional specification for

category A1 multimode fibres
IEC 61280-1-4, Fibre optic communication subsystem test procedures – Part 1-4: General
communication subsystems – Light source encircled flux measurement method
IEC 61280-4-1:2009, Fibre optic communication subsystem test procedures – Part 4-1:
Installed cable plant – Multimode attenuation measurement
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE In this clause only specific terms and definitions for the purposes of this document are provided. For
common fibre optic terms, reference is made to IEC/TR 61931.

– 6 – 62614 © IEC:2010
3.1
coupled power ratio
CPR
difference, expressed in dB, between the power exiting a multimode fibre and the power exiting
a single-mode fibre concatenated to the same multimode fibre with the same launching
conditions
3.2
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
3.3
mode power distribution
MPD
relative mode power in each of the mode groups of a multimode fibre, often shown graphically
3.4
multimode attenuation
attenuation pertaining to multimode fibres and/or multimode fibre components, systems and
subsystems
3.5
reference grade launch cord
launch cords constructed with a reference grade termination at the interface to the device
under test
3.6
reference grade termination
connector plug with tightened tolerances terminated onto an optical fibre with tightened
tolerances such that the expected loss of a connection formed by mating two such assemblies
is less than or equal to 0,1 dB (an adapter, required to ensure this performance, may be
considered to be part of the reference grade termination where required by the test
configuration)
NOTE 1 As an example, the core diameter tolerance may need to be ± 0,7 μm (under consideration). Other fibre
tolerances are also under consideration.
NOTE 2 This definition remains under study. When a more complete definition is available in another standard,
this definition will be replaced by a reference to that standard.
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, may 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.

62614 © IEC:2010 – 7 –
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 loss measurements across various sources is to narrowly
constrain the range of power distribution at large radii so that all compliant sources produce
closely agreeing loss measurement results. This is because the variation in the allowed power
distribution at large radii across different sources translates directly into variability of loss
measurements. Smaller power variations enable more reproducible loss 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 is 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
r
xI()x dx
∫
EF()r = (1)
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 – 62614 © IEC:2010
EF template
1,0
0,9
Target
Radial offset (μm)
10 0,3350
0,8
15 0,6550
20 0,9200
0,7
22 0,9751
0,6
Template
0,5
Target
0,4
0,3
0,2
0,1
0,0
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Radius  (μm)
IEC  1746/10
Figure 1 – EF template illustration
5.4 Encircled flux target for attenuation measurement
For the purposes of this standard, 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
μm core fibre at 1 300 nm
Table 2 – EF target for 50
Radial offset
Target
μm
10 0,336 6
15 0,656 7
20 0,918 6
22 0,972 8
EF
62614 © IEC:2010 – 9 –
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 losses 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 EF targets to produce comparable extrinsic component losses. 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.
2,00
2.2,0000
1,75
1.1,7575
Actual
Actual
Ideal
Ideal
1,50
1.1,5050
1,25
1.1,2525
1,00
1.1,0000
0,75
0.0,7575
0,50
0.0,5050
0,25
0.0,2525
0,00
0.0,0000
0,00 0,25 0,50 0,75 1,00 1,25 1,50 1,75 2,00
0.0,0000 0.0,2255 0.0,5050 0.0,7575 1.1,0000 1.1,2255 1.1,5050 1.1,7575 2.2,0000
850 nm attenuation  (dB)
850 nm Attenuation (dB)
IEC  1747/10
Figure 2 – Wavelength comparison

1 300 nm attenuation  (dB)
1 300 nm Attenuation (dB)
– 10 – 62614 © IEC:2010
5.6 Limitations on multimode launch conditions
The objective of this launch is to limit the variance to ± a specified percentage (e.g. 10 %) of
target or ± X dB, whichever is larger. X is called the tolerance threshold and varies depending
on core diameter and wavelength. The values in Table 5 have been set for installed cable plant.
Other thresholds may be determined for factory measurements.
Table 5 – Tolerance threshold
Core diameter Wavelength Threshold
nm dB
μm
50 850 0,08
50 1 300 0,12
62,5 850 0,10
62,5 1 300 0,15
5.7 Encircled flux limits
Upper and lower bounds (i.e. tolerance range) of the encircled flux are chosen to constrain the
measured loss 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 loss
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.
In all cases, the limits are chosen to constrain loss variation, relative to being exactly on the
target launch, to be no greater than the larger of a specified percentage, e.g. 10 % (on a dB
basis), or the threshold value. For example, a threshold value of 0,08 dB means that the loss
variation is expected to be within ±10 % for losses equal to or greater than 0,8 dB, and within
0,08 dB for losses 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 descri
...