IEC 62496-2:2017

Optical circuit boards - Basic test and measurement procedures - Part 2: General guidance for definition of measurement conditions for optical characteristics of optical circuit boards

IEC 62496-2:2017 specifies a method of defining the conditions for measurements of optical characteristics of optical circuit boards. The method comprises the use of code reference look-up tables to identify different critical aspects of the measurement environment. The values extracted from the tables are used to construct a measurement identification code, which, in itself, captures sufficient information about the measurement conditions, so as to ensure consistency of independently measured results within an acceptable margin. Recommended measurement conditions are specified to minimise further variation in independently measured results.

Cartes à circuits optiques - Méthodes fondamentales d'essais et de mesures - Partie 2: Recommandations générales pour la définition des conditions de mesure des caractéristiques optiques des cartes à circuits optiques

IEC 62496-2:2017 spécifie une méthode pour définir les conditions de mesure des caractéristiques optiques des cartes à circuits optiques. La méthode inclut l'utilisation de tableaux présentant des références à des codes pour identifier différents aspects critiques de l'environnement de mesure. Les valeurs extraites des tableaux sont utilisées pour construire un code d'identification des mesures qui contient suffisamment d'informations sur les conditions de mesure, afin d'assurer la cohérence des résultats mesurés de manière indépendante avec une marge acceptable. Des conditions de mesure recommandées sont spécifiées pour réduire le plus possible les variations des résultats mesurés de manière indépendante.
Mots clés: densités de largeur de bande, caractéristiques optiques des cartes à circuits optiques

General Information

• Status: Published
• Publication Date: 23-May-2017
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: TC 86 - Fibre optics
• Drafting Committee: JWG 9 - TC 86/JWG 9
• Current Stage: PPUB - Publication issued
• Start Date: 24-May-2017
• Completion Date: 27-Jun-2017

Overview

IEC 62496-2:2017 - part of the IEC 62496 series - provides general guidance for defining measurement conditions for the optical characteristics of optical circuit boards. The standard specifies a systematic method using code reference look‑up tables to capture source, launch, coupling and capturing conditions. Values from these tables form a Measurement Identification Code (MIC) that documents measurement conditions so independently measured results are reproducible and comparable within an acceptable margin. Recommended measurement conditions are also given to minimise variability.

Key Topics and Requirements

• Measurement definition system - requirements for accuracy, accountability, efficiency, convenience, independence, scalability and customisation to support consistent testing.
• Measurement definition criteria - defined groups of parameters covering:
  • Source characteristics (e.g., wavelength, polarization)
  • Launch conditions (modal profile, fibre or collimated launch)
  • Input coupling conditions (alignment, position, interface details)
  • Output coupling conditions (capture optics, distances)
  • Capturing conditions (detectors, integrating spheres, angular acceptance)
• Measurement Identification Code (MIC) - structured code (e.g., AAA‑BBB‑CCC‑DDD‑EEE) built from coordinate tables to identify exact test conditions.
• Coordinate lookup tables - predefined entries (AAA, BBB, CCC, DDD, EEE) and optional customisation placeholders to standardise reporting.
• Reference measurements and recommended setups to reduce inter-laboratory variation and support traceability.
• Scope of technologies - applies across optical circuit board varieties such as fibre‑optic laminates, polymer waveguides, planar glass waveguides and free‑space optics (see Annex A).

Practical Applications

• Create repeatable, traceable test procedures for R&D and production verification of embedded optical interconnects.
• Standardise test reports and data exchange between suppliers, test labs and system integrators using the MIC.
• Support supplier qualification, acceptance testing and cross‑laboratory comparisons by locking down launch/capture and source parameters.
• Reduce measurement uncertainty and improve interoperability of optical circuit boards in high‑bandwidth systems (backplanes, motherboards, peripheral cards).

Who Should Use This Standard

• Optical circuit board manufacturers and material suppliers
• Test and calibration laboratories validating optical characteristics
• System integrators and OEMs specifying embedded optical interconnect performance
• R&D engineers working on waveguide design, packaging and optical I/O
• Quality & compliance managers implementing measurement traceability

Related Standards

• Other parts of the IEC 62496 series (basic test and measurement procedures for optical circuit boards)
• Standards and guidance from IEC TC 86 (Fibre optics) for optical test methods and terminology

Keywords: IEC 62496-2, optical circuit boards, measurement identification code, MIC, measurement conditions, launch conditions, source characteristics, optical interconnect testing, optical measurement standard.

Standards Content (Sample)

IEC 62496-2 ®
Edition 1.0 2017-05
INTERNATIONAL
STANDARD
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Optical circuit boards – Basic test and measurement procedures –
Part 2: General guidance for definition of measurement conditions for optical
characteristics of optical circuit boards
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IEC 62496-2 ®
Edition 1.0 2017-05
INTERNATIONAL
STANDARD
colour
inside
Optical circuit boards – Basic test and measurement procedures –

Part 2: General guidance for definition of measurement conditions for optical

characteristics of optical circuit boards

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.01 ISBN 978-2-8322-4404-3

– 2 – IEC 62496-2:2017  IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Measurement definition system for optical circuit boards . 9
4.1 General . 9
4.2 Measurement definition system requirements. 9
4.2.1 Accuracy . 9
4.2.2 Accountability . 9
4.2.3 Efficiency . 10
4.2.4 Convenience . 10
4.2.5 Independent . 10
4.2.6 Scalable . 10
4.2.7 Customised requirements . 10
4.2.8 Prioritised structure . 10
4.3 Measurement definition criteria . 10
4.3.1 General . 10
4.3.2 Source characteristics . 11
4.3.3 Launch conditions . 11
4.3.4 Input coupling conditions . 14
4.3.5 Output coupling conditions . 15
4.3.6 Capturing conditions . 16
4.4 Launch and capturing position . 16
4.5 Launch and capture direction . 17
5 Measurement identification code . 19
5.1 General . 19
5.2 Measurement identification code construction . 19
5.2.1 General . 19
5.2.2 AAA – Source characteristics. 19
5.2.3 BBB(b1) – Launch conditions . 19
5.2.4 CCC – Input coupling conditions . 20
5.2.5 DDD – Output coupling conditions . 20
5.2.6 EEE – Capturing conditions . 20
5.3 Extended measurement identification code with customisation parameters . 20
5.3.1 General . 20
5.3.2 Customisation parameters with placeholders . 20
5.4 Reference measurements . 21
5.5 Coordinate table AAA – Source characteristics . 21
5.5.1 Mandatory parameters . 21
5.5.2 Customisation parameters . 21
5.6 Coordinate table BBB – Launch conditions. 24
5.6.1 Mandatory parameter. 24
5.6.2 Customisation parameters . 24
5.7 Coordinate table CCC – Input coupling conditions. 27

5.7.1 Mandatory parameters . 27
5.7.2 Customisation parameters . 27
5.8 Coordinate table DDD – Output coupling conditions . 29
5.8.1 Mandatory parameters . 29
5.8.2 Customisation parameters . 29
5.9 Coordinate table EEE – Capturing conditions . 31
5.9.1 Mandatory parameters . 31
5.9.2 Customisation parameters . 31
5.10 Examples of deployment . 34
5.10.1 General . 34
5.10.2 MIC-042-113(400)-001-001-112 (integrating sphere device details
including supplier and model number). 34
5.10.3 MIC-072-123(205)-053(1.56, X,X)-001-042 (integrating sphere device
details including supplier and model number) . 34
5.10.4 Fast polarisation axis: MIC-091-072(150)-042(1.53, 25, -30)-051-004;
slow polarisation axis: MIC-091-072(75)-042(1.53, 25, -120)-051-004 . 35
Annex A (informative) State of the art in optical interconnect technologies . 36
A.1 Diversity of optical interconnect technologies . 36
A.2 Fibre-optic circuit laminates . 36
A.3 Polymer waveguides . 36
A.4 Planar glass waveguides . 36
A.5 Free space optics . 37
A.6 Target applications . 37
Bibliography . 38

Figure 1 – Optical circuit board varieties . 6
Figure 2 – Recommended test setup for single-mode fibre launch conditions . 13
Figure 3 – Recommended test setup for multimode fibre launch conditions . 13
Figure 4 – Cross-sectional views of channel under test at input . 15
Figure 5 – Cross-sectional views of the channel under test at output . 16
Figure 6 – Measurement setup with collinear launch and capture direction . 17
Figure 7 – Measurement setup with orthogonal launch and capture direction . 18
Figure 8 – Measurement setup with oblique launch and capture direction . 18
Figure 9 – Measurement identification code construction . 19
Figure 10 – Reference measurements with the same MIC . 21

Table 1 – Recommended modal launch profiles . 12
Table 2 – AAA coordinate reference for source characteristics . 22
Table 3 – BBB coordinate reference for launch conditions . 25
Table 4 – CCC coordinate reference for input coupling conditions . 28
Table 5 – DDD coordinate reference for output coupling conditions . 30
Table 6 – EEE coordinate reference for capturing conditions . 32

– 4 – IEC 62496-2:2017  IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL CIRCUIT BOARDS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 2: General guidance for definition of measurement conditions for
optical characteristics of optical circuit boards

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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International Standard IEC 62496-2 has been prepared by IEC technical committee 86: Fibre
optics.
The text of this document is based on the following documents:
CDV Report on voting
86/509/CDV 86/515/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 62496 series, published under the general title Optical circuit
boards – Basic test and measurement procedures, 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
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– 6 – IEC 62496-2:2017  IEC 2017
INTRODUCTION
Bandwidth densities in modern data communication systems are driven by interconnect
speeds and scalable input/output (I/O) and will continue to increase over the coming years,
thereby severely impacting cost and performance in future data communication systems,
bringing increased demands in terms of signal integrity and power consumption.
The projected increase in capacity, processing power and bandwidth density in future
information communication systems will need to be addressed by the migration of embedded
optical interconnects into system enclosures. In particular, this would necessitate the
deployment of optical circuit board technologies on some or all key system cards, such as the
backplane, motherboard and peripheral circuit boards.
Many varieties of optical circuit board technology exist today, which differ strongly from each
other in terms of their intrinsic waveguide technology. As shown in Figure 1, these varieties
include, but are not limited to: a) fibre-optic laminate, b) polymer waveguides and c) planar
glass waveguides. Annex A provides a detailed overview of the state of the art of such optical
interconnect technologies.
IEC IEC IEC
a) Fibre-optic laminate b) Polymer waveguides c) Planar glass waveguides
Figure 1 – Optical circuit board varieties
One important prerequisite to the commercial adoption of optical circuit boards is a reliable
test and measurement definition system that is agnostic to the type of waveguide system
under test and, therefore, can be applied to different optical circuit board technologies as well
as being adaptable to future variants. A serious and common problem with the measurement
of optical waveguide systems has been lack of proper definition of the measurement
conditions for a given test regime, and consequently strong inconsistencies ensue in the
results of measurements by different parties on the same test sample. To date, no
methodology has been established to ensure that test and measurement conditions for such
optical waveguide systems are properly identified.
This document specifies a method of capturing sufficient information about the measurement
conditions for a given optical circuit board to ensure consistency of measurement results
within an acceptable margin.
Given the substantial variety in properties and requirements for different optical circuit board
types, some test environments and conditions are more appropriate than others for a given
optical circuit board. It is, therefore, crucial that this measurement identification standard
encompass a comprehensive range of test and measurement scenarios for all known types of
optical circuit boards and their waveguide systems, while also being sufficiently adaptable and
extendable to accommodate future waveguide technologies. In addition, a degree of
customisation is possible to account for arbitrary test parameters.

OPTICAL CIRCUIT BOARDS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 2: General guidance for definition of measurement conditions for
optical characteristics of optical circuit boards

1 Scope
This part of IEC 62496 specifies a method of defining the conditions for measurements of
optical characteristics of optical circuit boards. The method comprises the use of code
reference look-up tables to identify different critical aspects of the measurement environment.
The values extracted from the tables are used to construct a measurement identification code,
which, in itself, captures sufficient information about the measurement conditions, so as to
ensure consistency of independently measured results within an acceptable margin.
Recommended measurement conditions are specified to minimise further variation in
independently measured results.
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 61300-1, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 1: General and guidance
IEC 61300-3-53, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-53: Examinations and measurements – Encircled
angular flux (EAF) measurement method based on two-dimensional far field data from step
index multimode waveguide (including fibre)
IEC 62614, Fibre optics – Launch condition requirements for measuring multimode
attenuation
IEC 62496-2-1:2011, Optical circuit boards – Part 2-1: Measurements – Optical attenuation
and isolation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62496-2-1 and the
following 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

– 8 – IEC 62496-2:2017  IEC 2017
3.1
optical channel measurement identification code
MIC
numerical code used to capture sufficient information about the measurement conditions on a
waveguide under test in an optical circuit board, such as to ensure independent repeatability
of the measurement and consistency of measured results on an identical sample
3.2
optical channel under test
optical circuit board channel subjected to test and measurement regime
3.3
parabolic profile parameter
parameter which describes the refractive index profile of waveguide according to the following
equation
 g 
 r
 
n 1− 2∆ r< a
   
n(r)=
a
 
 
 
n 1− 2∆ r> a
 
where
g is the parabolic profile parameter;
a is the core radius;
r is the radial distance from core centre;
n is the refractive index at r = 0;
2 2 2
Δ is given by the relation ∆=(n − n )/ 2n , where n again is the refractive index at r = 0,
1 2 1 1
i.e. at the axis, and n is the refractive index at the outer edge of the core, i.e. at r = a
3.4
launch conduit
structure or mechanism which guides light from the measurement test source to the input
facet of the optical channel under test
Note 1 to entry: Examples include optical fibres, optical waveguides or optical trains.
3.5
capturing conduit
structure or mechanism which guides light from the output facet of the optical channel under
test to a measurement device
3.6
top input axis of channel under test
axis defined by the tester within the plane of the input facet used as a reference, against
which the polarisation axis of the launch conduit can be defined
3.7
top output axis of channel under test
axis defined by the tester within the plane of the output facet used as a reference, against
which the polarisation axis of the capturing conduit can be defined
3.8
polarisation maintaining optical fibre
single-mode optical fibre in which linearly polarized light, if properly launched into the fibre,
maintains a linear polarisation during propagation, exiting the fibre in a specific linear

polarisation state with little or no cross-coupling of optical power between the two polarisation
modes
Note 1 to entry: Such fibre is used in special applications where preserving polarisation is essential and is
characterised by a fast axis and a slow axis.
3.9
refractive index matching material
compliant or fixed material with a refractive index equal to the refractive index of the core of
the channel under test at the measurement wavelength and measurement conditions, which,
unless otherwise stated, is the standard atmospheric conditions as according to IEC 61300-1
3.10
refractive index damping material
compliant or fixed material with a refractive index within 0,05 of the refractive index of the
core of the channel under test at the measurement wavelength and measurement conditions,
which, unless otherwise stated, is the standard atmospheric conditions as according to
IEC 61300-1
4 Measurement definition system for optical circuit boards
4.1 General
A reliable test and measurement definition system for optical interconnect is a crucial
prerequisite for future commercial adoption of optical circuit board technology.
Independent repeatability of waveguide measurements is still very difficult to achieve due to
the lack of clarity on how measurement conditions are specified.
Therefore, such a definition system shall capture sufficient information about the
measurement conditions to ensure that the results of measurement on an identical test
sample by independent parties will be consistent within an acceptable margin of error.
Given the large number of measurement parameter permutations possible, the amount of
information required to describe sufficiently the measurement conditions is prohibitive. It
would be impractical for testers to provide a full textual description for each type of
measurement, especially in situations where optical circuit boards are subjected to a variety
of different measurement regimes, for instance, as part of a comprehensive quality assurance
regime in a commercial optical circuit board foundry.
IEC 62496-2-1 provides details on various types of measurements that can be carried out on
optical circuit boards.
4.2 Measurement definition system requirements
4.2.1 Accuracy
The measurement definition system shall capture sufficient information to ensure variability in
independently measured results within an acceptable margin.
4.2.2 Accountability
The measurement definition system shall force testers to be accountable to provide sufficient
information about the measurement conditions. The system shall therefore comprise a
formalised framework to capture the required amount of information about the measurement
conditions.
– 10 – IEC 62496-2:2017  IEC 2017
4.2.3 Efficiency
The measurement definition system shall allow the entirety of the measurement condition
information to be abbreviated into an optical channel measurement identification code (MIC)
such that it can be contained within no more than one line of text.
4.2.4 Convenience
The measurement identification code should be easy to construct and deconstruct using the
references look-up tables in this document.
4.2.5 Independent
The measurement definition system shall be independent of the type of optical circuit board
under test in order to accommodate different varieties of optical interconnect. To this end, the
type of optical channel under test will not be included in the information to be specified; it will
be treated as a "black box" bounded by the input facet and output facet of the optical channel
under test.
4.2.6 Scalable
The measurement definition system shall be scalable to accommodate new measurement
conditions appropriate to existing or as yet unknown optical interconnect types. To this end,
the system will have placeholders to allow easy addition of new information in future.
4.2.7 Customised requirements
Where the parameters of a measurement condition are not explicitly provided in the
corresponding look-up tables, the MIC shall be extendable to accommodate user-defined
parameters.
4.2.8 Prioritised structure
The measurement definition system shall give preference to measurement configurations that
are
• accessible, favouring the use of available and affordable equipment,
• viable, favouring measurements which can be easily carried out by most organisations
without the requirement for specialised or restricted equipment or expertise, and
• useful, favouring measurement of optical channel characteristics, which are most common
and relevant to its deployment and operation, for example insertion loss.
4.3 Measurement definition criteria
4.3.1 General
The measurement definition system shall provide information on the following five critical
aspects of the measurement environment:
• source characteristics (4.3.2);
• launch conditions (4.3.3);
• input coupling conditions (4.3.4);
• output coupling conditions (4.3.5);
• capturing conditions (4.3.6).

4.3.2 Source characteristics
4.3.2.1 General
Typical sources for common measurements on optical circuit board channels include LEDs,
laser diodes and white light sources, while less common sources include amplified
spontaneous emission devices. In order to accommodate a comprehensive range of available
source types and characteristics, the measurement identification system will define most
sources in terms of permutations of key properties including wavelength and spectral width.
Source optical power or modal profile need not be specified as only the optical power, and
modal profile at the launch facet need be specified as part of the launch conditions. Table 1 in
IEC 62496-2-1:2011 provides a list of recommended source characteristics.
4.3.2.2 Modulated sources
According to this document, the source amplitude and phase is considered un-modulated.
Optical modulation is a large and complex area with many possible permutations of
modulation type, duty cycle and data characteristics. Modulation schemes include standard
on-off keying (OOK) and multi-level modulation schemes such as phase amplitude modulation
(PAM), in-phase and quaternary (IQ) modulation schemes such as quadrature phase shift
keying (QPSK), multi-level quadrature amplitude modulation (nQAM), multi-pulse modulation
schemes, and discrete multi-tone (DMT). Data characteristics would include pseudo random
binary sequence (PRBS) data with various correlation lengths, as well as test data associated
with real data transmission protocols. Modulation will not be included in the measurement
definition system described in this document. In the event of a modulated source, the
modulation characteristics shall be stated explicitly.
4.3.2.3 Wavelength division multiplexed sources
According to this document, the source is considered to be centred on a single wavelength
with varying spectral widths, or white, which is consistent with the use of common commercial
sources including laser diodes, LEDs or amplified spontaneous emission devices. It may be
desirable to characterise the performance of the channel under test with wavelength division
multiplexed (WDM) light in which multiple wavelengths are superposed onto the launch
conduit in accordance with various WDM schemes. For example, the coarse wavelength
division multiplexing (CWDM) scheme allows on the order of ten signals to be encoded onto
separate wavelengths. The dense wavelength division multiplexing (DWDM) scheme allows
on the order of hundreds of signals to be encoded onto separate, more closely spaced,
wavelengths.
WDM sources are not included in this document, as the possible permutations would be
prohibitively complex. In the event of a wavelength division multiplexed source, the
wavelength division multiplexing characteristics shall be explicitly stated. Preferably, if
convenient, each wavelength-encoded channel can be uniquely specified using the
measurement identification system outlined in this document.
4.3.3 Launch conditions
4.3.3.1 General
Launch conditions have the greatest effect on variability of measurement results on optical
circuit board channels. It is, therefore, crucial that these be sufficiently defined.
Launch conditions shall include the following information that determines how light propagates
through the optical channel under test and, therefore, determines the independent
reproducibility of the measurement:
a) launch facet size and shape, which is typically defined by the core of the launch conduit –
for a standard fibre, it would be sufficient to specify the fibre type;
b) total optical power amplitude at the launch facet;

– 12 – IEC 62496-2:2017  IEC 2017
c) spatial (near-field) and angular (far-field) optical power distribution of light at the launch
facet. The launch conditions for multimode fibres should preferably comply with encircled
flux (EF) requirements defined in IEC 61300-1 or encircled angular flux (EAF)
requirements defined in IEC 61300-3-53. Such launch conditions can be reliably achieved
by deploying appropriate mode filtering equipment around or in-line with the launch
conduit. The launch conditions for single-mode fibres should comply with IEC 61300-1.
4.3.3.2 Recommended launch conditions
Table 1 defines key recommended launch profiles, including underfilled profiles, various mode
filtered multimode profiles and overfilled profiles, as well as recommendations on how to
reproduce some of these modal profiles.
Table 1 – Recommended modal launch profiles
Designation Modal distribution at launch Recommended measurement setup to achieve modal
facet distribution
Single-mode launch
UF Preferably, optical isolator between source and OS1 launch
fibre
Underfilled launch complies with
L1
single-mode launch 2 m long OS1 single-mode fibre (SMF) provides a single-mode
requirements in IEC 61300-1. launch profile.
Multimode launch
The source is passed into a 5 m graded index multimode fibre
(GI-MMF), which is wrapped 20 times around a 38 mm diameter
mandrel. The output of the mandrel is then passed through a
EF/EMD
mode controller/filter producing a mode filtered optical intensity
a)
L2 profile, which complies with EF requirement of IEC 61280-4-1.
Complies with EF requirements
This is then used as the input to a 5 m GI-MMF, which is
in IEC 61300-1.
wrapped 20 times around a 38 mm diameter mandrel to
produce a mode-stripped optical intensity profile at the GI-MMF
launch facet.
5 m graded index multimode fibre (GI-MMF) is passed through
EF
a mode controller/filter producing a mode filtered optical
a)
L3
Complies with EF requirements
intensity profile at the GI-MMF launch facet, which complies
in IEC 61300-1.
with EF requirement of IEC 61280-4-1.
5 m 50 µm graded index OM3 multimode fibre (GI-MMF) is
EMD
wrapped 20 times around a 38 mm diameter mandrel to
a)
L4
produce a mode-stripped optical intensity profile at the GI-MMF
Equilibrium modal distribution
launch facet.
OF
5 m 105 µm step index multimode fibre (SI-MMF) is wrapped 20
times around a 38 mm diameter mandrel to create a mode-
a)
Overfilled distribution – uniform
L5
scrambled, overfilled optical intensity profile at the SI-MMF
near-field optical intensity
launch facet.
distribution
VOF/EAF
5 m 200µm core step-index fibre (SI-MMF) is passed through a
Very overfilled distribution
mode controller producing a mode filtered optical intensity
a
L6
profile at the launch facet, which complies with the EAF
Complies with EAF
requirement of IEC 61300-3-53.
requirements in IEC 61300-3-
53.
a)
Bend insensitive fibre is not recommended for MM or SM test leads.

4.3.3.3 Recommended single-mode fibre launch measurement setup
The recommended measurement setup for single-mode fibre launch conditions is shown in
Figure 2. A single-mode optical source should be connected with a single-mode optical fibre,
first through a single-mode optical isolator to shield the source from unwanted back-
reflections occurring at different interfaces further on down the test link, especially the
interface between the launch facet and the input facet of the channel under test. The output
from the optical isolator should then be connected through a variable single-mode optical
attenuator. This will allow the tester to adjust the optical power at the launch facet to match

the required optical power as defined in the measurement identification code. This can
alternatively be achieved by using a power tuneable source.
AAA BBB
Single-mode Variable optical
Source optical isolator attenuator
SM fibre SM fibre SM fibre
IEC
Figure 2 – Recommended test setup for single-mode fibre launch conditions
4.3.3.4 Recommended multimode fibre launch measurement setup
A single-mode or multimode optical source should be connected with a single-mode or
multimode optical fibre, first through a single-mode or multimode optical isolator to shield the
source from unwanted back-reflections occurring at different interfaces further on in the test
link, especially the interface between the launch facet and the input facet of the channel
under test. If the source is a coherent source, it will be important to use a speckle filter to
average out the effects of speckle at the launch facet. One device can be an
electromechanical shaker applied after the source but before the variable optical attenuator. If
using such a device, it is important that the fibre be completely mechanically decoupled from
the launch facet, so the device should be applied between the source and the variable optical
attenuator. The photodetector used to measure the received light would need to be configured
to record average values over an appropriate time period, rather than immediate values. The
output from the optical isolator should then be connected with single-mode or multimode fibre
to the input of a variable single-mode or multimode optical attenuator. This will allow the
tester to adjust the optical power at the launch facet to match the required optical power as
defined in the measurement identification code. Alternatively, this can be achieved by using a
power tuneable source. Then the output of the variable optical attenuator will be connected
with multimode fibre to the input of a modal conditioning or filtering system, the output of
which will be connected with multimode fibre to the launch facet. The purpose of the modal
conditioning or filtering system is to ensure that the modal profile of the launch facet is
defined according to L2, L3, L4, L5 or L6 in Table 1. Figure 3 shows the recommended test
setup.
L2 is the preferred launch condition, in which a modal profile is generated, which complies
with the restricted launch EF requirements of IEC 61300-1, and this in turn is injected into a
GI-MMF fibre mandrel to produce a normalised output.
AAA BBB
Speckle filter
Variable optical Modal
single-mode/multimode
attenuator conditioner
optical isolator
Source
SM/MM SM/MM MM fibre MM fibre
fibre fibre
IEC
Figure 3 – Recommended test setup for multimode fibre launch conditions

– 14 – IEC 62496-2:2017  IEC 2017
4.3.4 Input coupling conditions
4.3.4.1 General
Input coupling conditions provide information on how the launch conduit is connected to the
input facet of the optical channel under test, for example through butt-coupling or imaging
through a lens system, and whether or not the input facet is treated with refractive index
matching or damping materials to mitigate scattering losses.
4.3.4.2 Compliant and fixed refractive index matching material or refractive index
damping material
It is common practice to apply a refractive index matching or damping material to the input
and/or output facet of the channel under test in order to mitigate Fresnel reflection and
scattering effects caused by the roughness of the input and/or output facet surface. The
refractive index material can be in the form of a liquid or gel, which will provide a compliant
buffer, and is best suited to measurement whereby the launch facet is butt-coupled in direct
contact or within a few microns of the input facet, such that the liquid or gel completely fills
the gap between the launch facet and the input facet of the channel under test. The use of
liquid or gel would not be suitable in the case of a free space projection of light onto the input
facet of the channel under test (such as imaging of the output of a fibre facet onto the input
facet of the channel under test using a lens assembly), as the surface tension of the
compliant material would cause it to form a boundary of unpredictable geometry around the
input facet of the channel under test. The alternative to using a compliant refractive index
matching material or refractive index damping material is to use a fixed refractive index
matching or damping material with a defined flat surface, such as a thin film. This is useful
when the input facet of the channel under test has high roughness, but a free space launch is
used.
4.3.4.3 Polarisation dependent input coupling conditions
One important possible measurement parameter for single-mode launch conditions is the fast
or slow polarisation axis of the launch facet relative to the channel under test. For example,
this would be required to characterise the polarisation dependent loss or the birefringence of
the channel under test. For this purpose, a top axis of the input channel under test shall be
defined by the first tester or test sample creator and clearly marked on the sample containing
the one or more channels under test or otherwise described in accompanying literature.
In measurements requiring a defined polarisation, the single-mode fibre could be a
polarisation maintaining optical fibre as defined in IEC TR 62349. The optical power exiting a
polarisation maintaining optical fibre will be divided between the fast axis and the orthogonal
slow axis. The ratio of optical power contained in the fast axis to the optical power contained
in the slow axis depends on a number of conditions, including how the power was launched
into fibre.
In the event that a polarisation maintaining optical f
...

IEC 62496-2 ®
Edition 1.0 2017-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical circuit boards – Basic test and measurement procedures –
Part 2: General guidance for definition of measurement conditions for optical
characteristics of optical circuit boards

Cartes à circuits optiques – Méthodes fondamentales d'essais et de mesures –
Partie 2: Recommandations générales pour la définition des conditions de
mesure des caractéristiques optiques des cartes à circuits optiques

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IEC 62496-2 ®
Edition 1.0 2017-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical circuit boards – Basic test and measurement procedures –

Part 2: General guidance for definition of measurement conditions for optical

characteristics of optical circuit boards

Cartes à circuits optiques – Méthodes fondamentales d'essais et de mesures –

Partie 2: Recommandations générales pour la définition des conditions de

mesure des caractéristiques optiques des cartes à circuits optiques

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.01 ISBN 978-2-8322-5232-1

– 2 – IEC 62496-2:2017  IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Measurement definition system for optical circuit boards . 9
4.1 General . 9
4.2 Measurement definition system requirements . 9
4.2.1 Accuracy . 9
4.2.2 Accountability . 9
4.2.3 Efficiency . 10
4.2.4 Convenience. 10
4.2.5 Independent . 10
4.2.6 Scalable . 10
4.2.7 Customised requirements . 10
4.2.8 Prioritised structure . 10
4.3 Measurement definition criteria . 10
4.3.1 General . 10
4.3.2 Source characteristics . 11
4.3.3 Launch conditions . 11
4.3.4 Input coupling conditions . 14
4.3.5 Output coupling conditions. 15
4.3.6 Capturing conditions . 16
4.4 Launch and capturing position . 16
4.5 Launch and capture direction . 17
5 Measurement identification code . 19
5.1 General . 19
5.2 Measurement identification code construction . 19
5.2.1 General . 19
5.2.2 AAA – Source characteristics . 19
5.2.3 BBB(b1) – Launch conditions . 19
5.2.4 CCC – Input coupling conditions . 20
5.2.5 DDD – Output coupling conditions . 20
5.2.6 EEE – Capturing conditions . 20
5.3 Extended measurement identification code with customisation parameters . 20
5.3.1 General . 20
5.3.2 Customisation parameters with placeholders . 20
5.4 Reference measurements . 21
5.5 Coordinate table AAA – Source characteristics . 21
5.5.1 Mandatory parameters . 21
5.5.2 Customisation parameters . 21
5.6 Coordinate table BBB – Launch conditions . 24
5.6.1 Mandatory parameter . 24
5.6.2 Customisation parameters . 24
5.7 Coordinate table CCC – Input coupling conditions . 27
5.7.1 Mandatory parameters . 27

5.7.2 Customisation parameters . 27
5.8 Coordinate table DDD – Output coupling conditions . 29
5.8.1 Mandatory parameters . 29
5.8.2 Customisation parameters . 29
5.9 Coordinate table EEE – Capturing conditions . 31
5.9.1 Mandatory parameters . 31
5.9.2 Customisation parameters . 31
5.10 Examples of deployment . 34
5.10.1 General . 34
5.10.2 MIC-042-113(400)-001-001-112 (integrating sphere device details
including supplier and model number) . 34
5.10.3 MIC-072-123(205)-053(1.56, X,X)-001-042 (integrating sphere device
details including supplier and model number) . 34
5.10.4 Fast polarisation axis: MIC-091-072(150)-042(1.53, 25, -30)-051-004;
slow polarisation axis: MIC-091-072(75)-042(1.53, 25, -120)-051-004 . 35
Annex A (informative) State of the art in optical interconnect technologies . 36
A.1 Diversity of optical interconnect technologies . 36
A.2 Fibre-optic circuit laminates . 36
A.3 Polymer waveguides . 36
A.4 Planar glass waveguides . 36
A.5 Free space optics . 37
A.6 Target applications . 37
Bibliography . 38

Figure 1 – Optical circuit board varieties . 6
Figure 2 – Recommended test setup for single-mode fibre launch conditions . 13
Figure 3 – Recommended test setup for multimode fibre launch conditions . 13
Figure 4 – Cross-sectional views of channel under test at input . 15
Figure 5 – Cross-sectional views of the channel under test at output . 16
Figure 6 – Measurement setup with collinear launch and capture direction . 17
Figure 7 – Measurement setup with orthogonal launch and capture direction . 18
Figure 8 – Measurement setup with oblique launch and capture direction . 18
Figure 9 – Measurement identification code construction . 19
Figure 10 – Reference measurements with the same MIC . 21

Table 1 – Recommended modal launch profiles . 12
Table 2 – AAA coordinate reference for source characteristics. 22
Table 3 – BBB coordinate reference for launch conditions . 25
Table 4 – CCC coordinate reference for input coupling conditions . 28
Table 5 – DDD coordinate reference for output coupling conditions . 30
Table 6 – EEE coordinate reference for capturing conditions . 32

– 4 – IEC 62496-2:2017  IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL CIRCUIT BOARDS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 2: General guidance for definition of measurement conditions for
optical characteristics of optical circuit boards

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 in addition to other activities, IEC publishes International Standards, Technical Specifications,
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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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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
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.
International Standard IEC 62496-2 has been prepared by IEC technical committee 86: Fibre
optics.
This bilingual version (2018-01) corresponds to the monolingual English version, published in
2017-05.
The text of this document is based on the following documents:
CDV Report on voting
86/509/CDV 86/515/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.

The French version of this standard has not been voted upon.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62496 series, published under the general title Optical circuit
boards – Basic test and measurement procedures, 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.
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.
– 6 – IEC 62496-2:2017  IEC 2017
INTRODUCTION
Bandwidth densities in modern data communication systems are driven by interconnect
speeds and scalable input/output (I/O) and will continue to increase over the coming years,
thereby severely impacting cost and performance in future data communication systems,
bringing increased demands in terms of signal integrity and power consumption.
The projected increase in capacity, processing power and bandwidth density in future
information communication systems will need to be addressed by the migration of embedded
optical interconnects into system enclosures. In particular, this would necessitate the
deployment of optical circuit board technologies on some or all key system cards, such as the
backplane, motherboard and peripheral circuit boards.
Many varieties of optical circuit board technology exist today, which differ strongly from each
other in terms of their intrinsic waveguide technology. As shown in Figure 1, these varieties
include, but are not limited to: a) fibre-optic laminate, b) polymer waveguides and c) planar
glass waveguides. Annex A provides a detailed overview of the state of the art of such optical
interconnect technologies.
IEC IEC IEC
a) Fibre-optic laminate b) Polymer waveguides c) Planar glass waveguides
Figure 1 – Optical circuit board varieties
One important prerequisite to the commercial adoption of optical circuit boards is a reliable
test and measurement definition system that is agnostic to the type of waveguide system
under test and, therefore, can be applied to different optical circuit board technologies as well
as being adaptable to future variants. A serious and common problem with the measurement
of optical waveguide systems has been lack of proper definition of the measurement
conditions for a given test regime, and consequently strong inconsistencies ensue in the
results of measurements by different parties on the same test sample. To date, no
methodology has been established to ensure that test and measurement conditions for such
optical waveguide systems are properly identified.
This document specifies a method of capturing sufficient information about the measurement
conditions for a given optical circuit board to ensure consistency of measurement results
within an acceptable margin.
Given the substantial variety in properties and requirements for different optical circuit board
types, some test environments and conditions are more appropriate than others for a given
optical circuit board. It is, therefore, crucial that this measurement identification standard
encompass a comprehensive range of test and measurement scenarios for all known types of
optical circuit boards and their waveguide systems, while also being sufficiently adaptable and
extendable to accommodate future waveguide technologies. In addition, a degree of
customisation is possible to account for arbitrary test parameters.

OPTICAL CIRCUIT BOARDS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 2: General guidance for definition of measurement conditions for
optical characteristics of optical circuit boards

1 Scope
This part of IEC 62496 specifies a method of defining the conditions for measurements of
optical characteristics of optical circuit boards. The method comprises the use of code
reference look-up tables to identify different critical aspects of the measurement environment.
The values extracted from the tables are used to construct a measurement identification code,
which, in itself, captures sufficient information about the measurement conditions, so as to
ensure consistency of independently measured results within an acceptable margin.
Recommended measurement conditions are specified to minimise further variation in
independently measured results.
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 61300-1, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 1: General and guidance
IEC 61300-3-53, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-53: Examinations and measurements – Encircled
angular flux (EAF) measurement method based on two-dimensional far field data from step
index multimode waveguide (including fibre)
IEC 62614, Fibre optics – Launch condition requirements for measuring multimode
attenuation
IEC 62496-2-1:2011, Optical circuit boards – Part 2-1: Measurements – Optical attenuation
and isolation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62496-2-1 and the
following 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

– 8 – IEC 62496-2:2017  IEC 2017
3.1
optical channel measurement identification code
MIC
numerical code used to capture sufficient information about the measurement conditions on a
waveguide under test in an optical circuit board, such as to ensure independent repeatability
of the measurement and consistency of measured results on an identical sample
3.2
optical channel under test
optical circuit board channel subjected to test and measurement regime
3.3
parabolic profile parameter
parameter which describes the refractive index profile of waveguide according to the following
equation
 g 
 r
 
n 1− 2∆ r< a
   
n(r)=
a
 
 
 
n 1− 2∆ r> a
 
where
g is the parabolic profile parameter;
a is the core radius;
r is the radial distance from core centre;
n is the refractive index at r = 0;
2 2 2
Δ is given by the relation ∆=(n − n )/ 2n , where n again is the refractive index at r = 0,
1 2 1
i.e. at the axis, and n is the refractive index at the outer edge of the core, i.e. at r = a
3.4
launch conduit
structure or mechanism which guides light from the measurement test source to the input
facet of the optical channel under test
Note 1 to entry: Examples include optical fibres, optical waveguides or optical trains.
3.5
capturing conduit
structure or mechanism which guides light from the output facet of the optical channel under
test to a measurement device
3.6
top input axis of channel under test
axis defined by the tester within the plane of the input facet used as a reference, against
which the polarisation axis of the launch conduit can be defined
3.7
top output axis of channel under test
axis defined by the tester within the plane of the output facet used as a reference, against
which the polarisation axis of the capturing conduit can be defined
3.8
polarisation maintaining optical fibre
single-mode optical fibre in which linearly polarized light, if properly launched into the fibre,
maintains a linear polarisation during propagation, exiting the fibre in a specific linear

polarisation state with little or no cross-coupling of optical power between the two polarisation
modes
Note 1 to entry: Such fibre is used in special applications where preserving polarisation is essential and is
characterised by a fast axis and a slow axis.
3.9
refractive index matching material
compliant or fixed material with a refractive index equal to the refractive index of the core of
the channel under test at the measurement wavelength and measurement conditions, which,
unless otherwise stated, is the standard atmospheric conditions as according to IEC 61300-1
3.10
refractive index damping material
compliant or fixed material with a refractive index within 0,05 of the refractive index of the
core of the channel under test at the measurement wavelength and measurement conditions,
which, unless otherwise stated, is the standard atmospheric conditions as according to
IEC 61300-1
4 Measurement definition system for optical circuit boards
4.1 General
A reliable test and measurement definition system for optical interconnect is a crucial
prerequisite for future commercial adoption of optical circuit board technology.
Independent repeatability of waveguide measurements is still very difficult to achieve due to
the lack of clarity on how measurement conditions are specified.
Therefore, such a definition system shall capture sufficient information about the
measurement conditions to ensure that the results of measurement on an identical test
sample by independent parties will be consistent within an acceptable margin of error.
Given the large number of measurement parameter permutations possible, the amount of
information required to describe sufficiently the measurement conditions is prohibitive. It
would be impractical for testers to provide a full textual description for each type of
measurement, especially in situations where optical circuit boards are subjected to a variety
of different measurement regimes, for instance, as part of a comprehensive quality assurance
regime in a commercial optical circuit board foundry.
IEC 62496-2-1 provides details on various types of measurements that can be carried out on
optical circuit boards.
4.2 Measurement definition system requirements
4.2.1 Accuracy
The measurement definition system shall capture sufficient information to ensure variability in
independently measured results within an acceptable margin.
4.2.2 Accountability
The measurement definition system shall force testers to be accountable to provide sufficient
information about the measurement conditions. The system shall therefore comprise a
formalised framework to capture the required amount of information about the measurement
conditions.
– 10 – IEC 62496-2:2017  IEC 2017
4.2.3 Efficiency
The measurement definition system shall allow the entirety of the measurement condition
information to be abbreviated into an optical channel measurement identification code (MIC)
such that it can be contained within no more than one line of text.
4.2.4 Convenience
The measurement identification code should be easy to construct and deconstruct using the
references look-up tables in this document.
4.2.5 Independent
The measurement definition system shall be independent of the type of optical circuit board
under test in order to accommodate different varieties of optical interconnect. To this end, the
type of optical channel under test will not be included in the information to be specified; it will
be treated as a "black box" bounded by the input facet and output facet of the optical channel
under test.
4.2.6 Scalable
The measurement definition system shall be scalable to accommodate new measurement
conditions appropriate to existing or as yet unknown optical interconnect types. To this end,
the system will have placeholders to allow easy addition of new information in future.
4.2.7 Customised requirements
Where the parameters of a measurement condition are not explicitly provided in the
corresponding look-up tables, the MIC shall be extendable to accommodate user-defined
parameters.
4.2.8 Prioritised structure
The measurement definition system shall give preference to measurement configurations that
are
• accessible, favouring the use of available and affordable equipment,
• viable, favouring measurements which can be easily carried out by most organisations
without the requirement for specialised or restricted equipment or expertise, and
• useful, favouring measurement of optical channel characteristics, which are most common
and relevant to its deployment and operation, for example insertion loss.
4.3 Measurement definition criteria
4.3.1 General
The measurement definition system shall provide information on the following five critical
aspects of the measurement environment:
• source characteristics (4.3.2);
• launch conditions (4.3.3);
• input coupling conditions (4.3.4);
• output coupling conditions (4.3.5);
• capturing conditions (4.3.6).

4.3.2 Source characteristics
4.3.2.1 General
Typical sources for common measurements on optical circuit board channels include LEDs,
laser diodes and white light sources, while less common sources include amplified
spontaneous emission devices. In order to accommodate a comprehensive range of available
source types and characteristics, the measurement identification system will define most
sources in terms of permutations of key properties including wavelength and spectral width.
Source optical power or modal profile need not be specified as only the optical power, and
modal profile at the launch facet need be specified as part of the launch conditions. Table 1 in
IEC 62496-2-1:2011 provides a list of recommended source characteristics.
4.3.2.2 Modulated sources
According to this document, the source amplitude and phase is considered un-modulated.
Optical modulation is a large and complex area with many possible permutations of
modulation type, duty cycle and data characteristics. Modulation schemes include standard
on-off keying (OOK) and multi-level modulation schemes such as phase amplitude modulation
(PAM), in-phase and quaternary (IQ) modulation schemes such as quadrature phase shift
keying (QPSK), multi-level quadrature amplitude modulation (nQAM), multi-pulse modulation
schemes, and discrete multi-tone (DMT). Data characteristics would include pseudo random
binary sequence (PRBS) data with various correlation lengths, as well as test data associated
with real data transmission protocols. Modulation will not be included in the measurement
definition system described in this document. In the event of a modulated source, the
modulation characteristics shall be stated explicitly.
4.3.2.3 Wavelength division multiplexed sources
According to this document, the source is considered to be centred on a single wavelength
with varying spectral widths, or white, which is consistent with the use of common commercial
sources including laser diodes, LEDs or amplified spontaneous emission devices. It may be
desirable to characterise the performance of the channel under test with wavelength division
multiplexed (WDM) light in which multiple wavelengths are superposed onto the launch
conduit in accordance with various WDM schemes. For example, the coarse wavelength
division multiplexing (CWDM) scheme allows on the order of ten signals to be encoded onto
separate wavelengths. The dense wavelength division multiplexing (DWDM) scheme allows
on the order of hundreds of signals to be encoded onto separate, more closely spaced,
wavelengths.
WDM sources are not included in this document, as the possible permutations would be
prohibitively complex. In the event of a wavelength division multiplexed source, the
wavelength division multiplexing characteristics shall be explicitly stated. Preferably, if
convenient, each wavelength-encoded channel can be uniquely specified using the
measurement identification system outlined in this document.
4.3.3 Launch conditions
4.3.3.1 General
Launch conditions have the greatest effect on variability of measurement results on optical
circuit board channels. It is, therefore, crucial that these be sufficiently defined.
Launch conditions shall include the following information that determines how light propagates
through the optical channel under test and, therefore, determines the independent
reproducibility of the measurement:
a) launch facet size and shape, which is typically defined by the core of the launch conduit –
for a standard fibre, it would be sufficient to specify the fibre type;
b) total optical power amplitude at the launch facet;

– 12 – IEC 62496-2:2017  IEC 2017
c) spatial (near-field) and angular (far-field) optical power distribution of light at the launch
facet. The launch conditions for multimode fibres should preferably comply with encircled
flux (EF) requirements defined in IEC 61300-1 or encircled angular flux (EAF)
requirements defined in IEC 61300-3-53. Such launch conditions can be reliably achieved
by deploying appropriate mode filtering equipment around or in-line with the launch
conduit. The launch conditions for single-mode fibres should comply with IEC 61300-1.
4.3.3.2 Recommended launch conditions
Table 1 defines key recommended launch profiles, including underfilled profiles, various mode
filtered multimode profiles and overfilled profiles, as well as recommendations on how to
reproduce some of these modal profiles.
Table 1 – Recommended modal launch profiles
Designation Modal distribution at launch Recommended measurement setup to achieve modal
facet distribution
Single-mode launch
UF Preferably, optical isolator between source and OS1 launch
fibre
Underfilled launch complies with
L1
single-mode launch 2 m long OS1 single-mode fibre (SMF) provides a single-mode
requirements in IEC 61300-1. launch profile.
Multimode launch
The source is passed into a 5 m graded index multimode fibre
(GI-MMF), which is wrapped 20 times around a 38 mm diameter
mandrel. The output of the mandrel is then passed through a
EF/EMD
mode controller/filter producing a mode filtered optical intensity
a)
L2 profile, which complies with EF requirement of IEC 61280-4-1.
Complies with EF requirements
This is then used as the input to a 5 m GI-MMF, which is
in IEC 61300-1.
wrapped 20 times around a 38 mm diameter mandrel to
produce a mode-stripped optical intensity profile at the GI-MMF
launch facet.
5 m graded index multimode fibre (GI-MMF) is passed through
EF
a mode controller/filter producing a mode filtered optical
a)
L3
Complies with EF requirements
intensity profile at the GI-MMF launch facet, which complies
in IEC 61300-1.
with EF requirement of IEC 61280-4-1.
5 m 50 µm graded index OM3 multimode fibre (GI-MMF) is
EMD
wrapped 20 times around a 38 mm diameter mandrel to
a)
L4
produce a mode-stripped optical intensity profile at the GI-MMF
Equilibrium modal distribution
launch facet.
OF
5 m 105 µm step index multimode fibre (SI-MMF) is wrapped 20
times around a 38 mm diameter mandrel to create a mode-
a)
Overfilled distribution – uniform
L5
scrambled, overfilled optical intensity profile at the SI-MMF
near-field optical intensity
launch facet.
distribution
VOF/EAF
5 m 200µm core step-index fibre (SI-MMF) is passed through a
Very overfilled distribution
mode controller producing a mode filtered optical intensity
a
L6
profile at the launch facet, which complies with the EAF
Complies with EAF
requirement of IEC 61300-3-53.
requirements in IEC 61300-3-
53.
a)
Bend insensitive fibre is not recommended for MM or SM test leads.

4.3.3.3 Recommended single-mode fibre launch measurement setup
The recommended measurement setup for single-mode fibre launch conditions is shown in
Figure 2. A single-mode optical source should be connected with a single-mode optical fibre,
first through a single-mode optical isolator to shield the source from unwanted back-
reflections occurring at different interfaces further on down the test link, especially the
interface between the launch facet and the input facet of the channel under test. The output
from the optical isolator should then be connected through a variable single-mode optical
attenuator. This will allow the tester to adjust the optical power at the launch facet to match

the required optical power as defined in the measurement identification code. This can
alternatively be achieved by using a power tuneable source.
AAA BBB
Single-mode Variable optical
Source optical isolator attenuator
SM fibre SM fibre SM fibre
IEC
Figure 2 – Recommended test setup for single-mode fibre launch conditions
4.3.3.4 Recommended multimode fibre launch measurement setup
A single-mode or multimode optical source should be connected with a single-mode or
multimode optical fibre, first through a single-mode or multimode optical isolator to shield the
source from unwanted back-reflections occurring at different interfaces further on in the test
link, especially the interface between the launch facet and the input facet of the channel
under test. If the source is a coherent source, it will be important to use a speckle filter to
average out the effects of speckle at the launch facet. One device can be an
electromechanical shaker applied after the source but before the variable optical attenuator. If
using such a device, it is important that the fibre be completely mechanically decoupled from
the launch facet, so the device should be applied between the source and the variable optical
attenuator. The photodetector used to measure the received light would need to be configured
to record average values over an appropriate time period, rather than immediate values. The
output from the optical isolator should then be connected with single-mode or multimode fibre
to the input of a variable single-mode or multimode optical attenuator. This will allow the
tester to adjust the optical power at the launch facet to match the required optical power as
defined in the measurement identification code. Alternatively, this can be achieved by using a
power tuneable source. Then the output of the variable optical attenuator will be connected
with multimode fibre to the input of a modal conditioning or filtering system, the output of
which will be connected with multimode fibre to the launch facet. The purpose of the modal
conditioning or filtering system is to ensure that the modal profile of the launch facet is
defined according to L2, L3, L4, L5 or L6 in Table 1. Figure 3 shows the recommended test
setup.
L2 is the preferred launch condition, in which a modal profile is generated, which complies
with the restricted launch EF requirements of IEC 61300-1, and this in turn is injected into a
GI-
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