IEC 61300-3-53:2015

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 61300-3-53:2015 is intended to characterize the encircled angular flux of measurement step index multimode waveguide light sources, in which most of the transverse modes are excited. The term waveguide is understood to include both channel waveguides and optical fibres but not slab waveguides in this standard. Encircled angular flux (EAF) is the fraction of the total optical power radiating from a step index multimode waveguide's core within a certain solid angle. The EAF is measured as a function of the numerical aperture full angle. The basic approach is to collect, for every measurement, two dimensional far field data using a calibrated camera and to convert them mathematically into encircled angular flux.
Keywords: encircled angular flux (EAF), measurement step index multimode waveguide light sources

Dispositifs d'interconnexion et composants passifs fibroniques - Procédures fondamentales d'essais et de mesures – Partie 3-53: Examens et mesures – Méthode de mesure du flux angulaire inscrit (EAF) fondée sur les données bidimensionnelles de champ lointain d’un guide d’ondes multimodal à saut d’indice (fibre incluse)

IEC 61300-3-53:2015 cette publication est destinée à caractériser le flux angulaire inscrit lors de mesures portant sur des sources de rayonnement lumineux dotées d’un guide d’ondes multimodal à saut d’indice, où la plupart des modes transversaux sont excités. Dans la présente norme, le terme « guide d’ondes » est à considérer comme incluant à la fois des guides d’ondes de canal et des fibres optiques, mais pas les guides d’ondes rectangulaires rigides. Le flux angulaire inscrit (EAF) est la fraction de la puissance optique totale rayonnée par le cœur d’un guide d’ondes multimodal à saut d’indice dans un certain angle solide. L’EAF est mesuré en fonction de l’angle d’ouverture numérique complet. L’approche fondamentale consiste à recueillir pour chaque mesure des données bidimensionnelles de champ lointain en utilisant une caméra étalonnée et à les convertir mathématiquement en flux angulaire inscrit.
Mots clés: flux angulaire inscrit (EAF). mesures portant sur des sources de rayonnement lumineux dotées d’un guide d’ondes multimodal

General Information

• Status: Published
• Publication Date: 04-Feb-2015
• ICS: 33.180.20 - Fibre optic interconnecting devices
• Technical Committee: SC 86B - Fibre optic interconnecting devices and passive components
• Drafting Committee: WG 4 - TC 86/SC 86B/WG 4
• Current Stage: DELPUB - Deleted Publication
• Start Date: 15-Dec-2020
• Completion Date: 21-Dec-2018

Relations

• Revised: IEC 61300-3-53:2020 - 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 multimode waveguide (including fibre)
• Effective Date: 05-Sep-2023

Overview

IEC 61300-3-53:2015 defines a standardized Encircled Angular Flux (EAF) measurement method for step index multimode waveguide light sources (including optical fibres and channel waveguides, but excluding slab waveguides). EAF quantifies the fraction of total optical power radiating from a waveguide core within a given solid angle and is reported as a function of the numerical aperture (NA) full angle. The method uses two‑dimensional far‑field (FFP) data captured with a calibrated camera and converts those images mathematically into EAF values.

Key topics and technical requirements

• Scope and definitions: EAF, FFP, NA and related terms specific to step‑index multimode waveguides.
• Measurement approaches:
  • Method 1 - fθ lens imaging: uses an fθ lens to map angular distribution to image height; requires an FFP optical system, calibrated camera and analyser software.
  • Method 2 - Direct imaging: options include integrating sphere, single‑mode fibre scanning, or direct imaging devices to collect far‑field power distribution.
• Apparatus components: micro‑positioner, FFP optical system, camera/detector, computer with EAF analyser, calibration light source and alignment optics.
• Calibration and geometric correction: procedures for geometric calibration of the imaging system and conversion from image coordinates to polar/angular coordinates.
• Measurement workflow: far‑field image acquisition, background noise removal, centre determination (optical or mechanical), computation of encircled angular flux vs NA.
• Data and reporting: standard EAF charts and optional information available on request (e.g., raw far‑field data, calibration details).
• Safety and normative references: compliance with IEC 60825‑1 for laser safety and IEC 61300‑1 for general fibre test guidance.

Applications and users

IEC 61300-3-53 is practical for:

• Fiber and component manufacturers verifying light‑source angular distributions and launch conditions.
• Test laboratories and OEMs performing acceptance testing, quality control and compliance checks.
• Network integrators and system designers modeling modal coupling, link budgets, and connector/assembly performance where accurate NA‑dependent source characterization is required.
• R&D teams studying mode excitation and far‑field behavior in multimode systems.

Typical uses include source qualification, modal launch validation, connector and assembly evaluation, and supplying standard EAF data for system simulations.

Related standards

• IEC 61300-1 - Fibre optic interconnecting devices and passive components: General and guidance (basic test procedures)
• IEC 60825-1 - Safety of laser products: Equipment classification and requirements

Keywords: encircled angular flux (EAF), measurement step index multimode waveguide light sources, numerical aperture, far‑field pattern, fθ lens, multimode fibre testing.

Standards Content (Sample)

IEC 61300-3-53 ®
Edition 1.0 2015-02
INTERNATIONAL
STANDARD
colour
inside
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)

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from

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IEC 61300-3-53 ®
Edition 1.0 2015-02
INTERNATIONAL
STANDARD
colour
inside
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)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.20 ISBN 978-2-83222-240-9

– 2 – IEC 61300-3-53:2015 © IEC 2015

CONTENTS
FOREWORD . 4

1 Scope . 6

2 Normative references. 6

3 Terms and definitions . 6

4 Standard atmospheric conditions . 7

5 Apparatus . 7

5.1 General . 7

5.2 Measurement method 1: fθ lens imaging . 8
5.2.1 General . 8
5.2.2 Micro-positioner . 8
5.2.3 FFP optical system . 8
5.2.4 Camera . 8
5.2.5 Computer (EAF analyser module) . 9
5.2.6 Calibration light source . 9
5.3 Measurement method 2: direct imaging . 9
5.3.1 General . 9
5.3.2 Micro-positioner . 9
5.3.3 Optical power . 9
5.3.4 Alignment . 9
5.3.5 Detector . 9
5.3.6 Single-mode fibre . 10
5.3.7 Imaging device . 10
6 Sampling and specimens . 11
7 Geometric calibration . 11
8 Measurement procedure . 12
8.1 Safety . 12
8.2 Far field image acquisition . 12
8.2.1 General . 12
8.2.2 Waveguide end-face alignment . 12
8.2.3 Light source image acquisition . 12
8.3 Removal of background noise . 13
8.4 Centre determination . 13

8.4.1 General . 13
8.4.2 Method A: Optical centre determination . 13
8.4.3 Method B: Mechanical centre determination . 14
8.5 Computation of encircled angular flux . 14
9 Results . 16
9.1 Information available with each measurement . 16
9.2 Information available upon request . 16
10 Details to be specified . 16
Annex A (informative) System requirements: measurement method 1 – Field optical
system . 18
A.1 General . 18
A.2 Requirements . 18
Annex B (informative) System requirements: measurement method 2 – Direct imaging . 19
B.1 General . 19

B.2 Requirements . 19

Bibliography . 20

Figure 1 – Apparatus configuration: Measurement method 1: fθ lens imaging . 8

Figure 2 – Far field optical system diagram . 8

Figure 3 – Apparatus configuration: measurement method 2 – Direct imaging using an
integrating sphere . 10

Figure 4 – Apparatus configuration: measurement method 2 – Direct imaging using a

single-mode fibre . 10

Figure 5 – Apparatus configuration: measurement method 2 – Direct imaging using an
imaging device . 11
Figure 6 – Calibration apparatus example. 12
Figure 7 – Acquired far field image . 13
Figure 8 – Acquired far field image with false colour . 13
Figure 9 – Optical centre determination . 14
Figure 10 – Coordinate conversion to polar coordinate on the image sensor plane . 15
Figure 11 – Standard encircled angular flux chart . 16
Figure A.1 – An example of an optical system using an fθ lens . 18

– 4 – IEC 61300-3-53:2015 © IEC 2015

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
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)
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 61300-3-53 has been prepared by subcommittee 86B: Fibre optic
interconnecting devices and passive components, of IEC technical committee 86: Fibre optics.

The text of this standard is based on the following documents:

FDIS Report on voting
86B/3850/FDIS 86B/3875/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.

A list of all parts in the IEC 61300 series, published under the general title, Fibre optic
interconnecting and passive components – Basic test and measurement procedures, can be
found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website 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.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication
indicates that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 61300-3-53:2015 © IEC 2015

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)
1 Scope
This part of IEC 61300 is intended to characterize the encircled angular flux of measurement
step index multimode waveguide light sources, in which most of the transverse modes are
excited. The term waveguide is understood to include both channel waveguides and optical
fibres but not slab waveguides in this standard.
Encircled angular flux (EAF) is the fraction of the total optical power radiating from a step
index multimode waveguide’s core within a certain solid angle. The EAF is measured as a
function of the numerical aperture full angle. The basic approach is to collect, for every
measurement, two dimensional far field data using a calibrated camera and to convert them
mathematically into encircled angular flux.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61300-1, Fibre optic interconnecting devices and passive components − Basic test and
measurement procedures − Part 1: General and guidance
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
encircled angular flux
EAF
fraction of the total optical power radiating from a step index multimode waveguide’s core
within a certain solid angle
3.2
fθ lens
lens converting the angle of incidence of the input beam, θ, into the output beam height, h
Note 1 to entry: The relationship between them is h = fθ, where f is the focal length of the lens.

3.3
numerical aperture
NA
sine of the vertex half-angle of the largest cone of meridional rays that can enter or leave the

core of an optical waveguide, multiplied by the refractive index of the medium in which the

cone is located.
3.4
far field pattern
FFP
angular distribution of light radiating from a waveguide’s core, which corresponds to the

optical power distribution on a plane normal to the waveguide axis some distance from its end

facet.
Note 1 to entry: The distance depends on the largest waveguide cross section, a, the wavelength, lambda and the
angle,ϕ, to the optical axis. It is abbreviated to FFP. In the far field region the shape of the distribution does not
change as the distance from the waveguide end facet increases; the distribution only scales in size with distance, L.
2a(cosϕ)
L>>
λ
3.5
far field image
far field pattern formed on an imaging device
3.6
centroid
optical centre of the far field image
3.7
neutral density filter
ND
filter that attenuates light of all colours equally
4 Standard atmospheric conditions
The standard atmospheric conditions are specified in IEC 61300-1.
5 Apparatus
5.1 General
The optical source multimode waveguide shall be long enough to ensure that all cladding
modes are stripped by passage through the waveguide. Often the fibre coating or tight buffer
is sufficient to perform this function. Alternatively a cladding mode stripper shall be used in
the source launch optical multimode fibre. An example of a typical cladding mode stripper
which would be suitable for optical fibre is sufficient windings of the fibre around a mandrel of
an appropriate diameter. The windings also have a more important essential effect to fully fill
the transverse modes across the maximum mode field diameter. It should be checked that all
of the transverse modes of the fibre are sufficiently well excited. This can be done by
comparing the FFPs for different lengths of the launch fibre or different light sources. Once
the FFP no longer changes in form as the launch fibre length is increased there is no need to
increase the length further.
– 8 – IEC 61300-3-53:2015 © IEC 2015

5.2 Measurement method 1: fθ lens imaging

5.2.1 General
In theory, this measurement method, which is effectively a coherent optical method to Fourier
Transform the near field to the far field using a lens, does not operate well using very
wideband optical sources. Experimentally it has been shown to operate sufficiently well
...

IEC 61300-3-53 ®
Edition 1.0 2015-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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)

Dispositifs d’interconnexion et composants passifs fibroniques – Procédures
fondamentales d’essais et de mesures –
Partie 3-53: Examens et mesures – Méthode de mesure du flux angulaire inscrit
(EAF) fondée sur les données bidimensionnelles de champ lointain d’un guide
d’ondes multimodal à saut d’indice (fibre incluse)

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IEC 61300-3-53 ®
Edition 1.0 2015-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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)

Dispositifs d’interconnexion et composants passifs fibroniques – Procédures

fondamentales d’essais et de mesures –

Partie 3-53: Examens et mesures – Méthode de mesure du flux angulaire inscrit

(EAF) fondée sur les données bidimensionnelles de champ lointain d’un guide

d’ondes multimodal à saut d’indice (fibre incluse)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.20 ISBN 978-2-8322-7194-0

– 2 – IEC 61300-3-53:2015 © IEC 2015
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Standard atmospheric conditions . 7
5 Apparatus . 7
5.1 General . 7
5.2 Measurement method 1: fθ lens imaging . 8
5.2.1 General . 8
5.2.2 Micro-positioner . 8
5.2.3 FFP optical system . 8
5.2.4 Camera . 8
5.2.5 Computer (EAF analyser module) . 9
5.2.6 Calibration light source . 9
5.3 Measurement method 2: direct imaging . 9
5.3.1 General . 9
5.3.2 Micro-positioner . 9
5.3.3 Optical power . 9
5.3.4 Alignment . 9
5.3.5 Detector . 9
5.3.6 Single-mode fibre . 10
5.3.7 Imaging device . 10
6 Sampling and specimens . 11
7 Geometric calibration . 11
8 Measurement procedure . 12
8.1 Safety . 12
8.2 Far field image acquisition . 12
8.2.1 General . 12
8.2.2 Waveguide end-face alignment . 12
8.2.3 Light source image acquisition . 12
8.3 Removal of background noise . 13
8.4 Centre determination . 13
8.4.1 General . 13
8.4.2 Method A: Optical centre determination . 13
8.4.3 Method B: Mechanical centre determination . 14
8.5 Computation of encircled angular flux . 14
9 Results . 16
9.1 Information available with each measurement . 16
9.2 Information available upon request . 16
10 Details to be specified . 17
Annex A (informative) System requirements: measurement method 1 – Field optical
system . 18
A.1 General . 18
A.2 Requirements . 18

Annex B (informative) System requirements: measurement method 2 – Direct imaging . 19
B.1 General . 19
B.2 Requirements . 19
Bibliography . 20

Figure 1 – Apparatus configuration: Measurement method 1: fθ lens imaging . 8
Figure 2 – Far field optical system diagram . 8
Figure 3 – Apparatus configuration: measurement method 2 – Direct imaging using an
integrating sphere . 10
Figure 4 – Apparatus configuration: measurement method 2 – Direct imaging using a
single-mode fibre . 10
Figure 5 – Apparatus configuration: measurement method 2 – Direct imaging using an
imaging device . 11
Figure 6 – Calibration apparatus example . 12
Figure 7 – Acquired far field image . 13
Figure 8 – Acquired far field image with false colour . 13
Figure 9 – Optical centre determination . 14
Figure 10 – Coordinate conversion to polar coordinate on the image sensor plane . 15
Figure 11 – Standard encircled angular flux chart . 16
Figure A.1 – An example of an optical system using an fθ lens . 18

– 4 – IEC 61300-3-53:2015 © IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
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)
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,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
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International Standard IEC 61300-3-53 has been prepared by subcommittee 86B: Fibre optic
interconnecting devices and passive components, of IEC technical committee 86: Fibre optics.
This bilingual version (2019-07) corresponds to the English version, published in 2015-02.

The text of this standard is based on the following documents:
FDIS Report on voting
86B/3850/FDIS 86B/3875/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.
A list of all parts in the IEC 61300 series, published under the general title, Fibre optic
interconnecting and passive components – Basic test and measurement procedures, can be
found on the IEC website.
The French version of this standard has not been voted upon.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website 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.
– 6 – IEC 61300-3-53:2015 © IEC 2015
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)
1 Scope
This part of IEC 61300 is intended to characterize the encircled angular flux of measurement
step index multimode waveguide light sources, in which most of the transverse modes are
excited. The term waveguide is understood to include both channel waveguides and optical
fibres but not slab waveguides in this standard.
Encircled angular flux (EAF) is the fraction of the total optical power radiating from a step
index multimode waveguide’s core within a certain solid angle. The EAF is measured as a
function of the numerical aperture full angle. The basic approach is to collect, for every
measurement, two dimensional far field data using a calibrated camera and to convert them
mathematically into encircled angular flux.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61300-1, Fibre optic interconnecting devices and passive components − Basic test and
measurement procedures − Part 1: General and guidance
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
encircled angular flux
EAF
fraction of the total optical power radiating from a step index multimode waveguide’s core
within a certain solid angle
3.2
fθ lens
lens converting the angle of incidence of the input beam, θ, into the output beam height, h
Note 1 to entry: The relationship between them is h = fθ, where f is the focal length of the lens.

3.3
numerical aperture
NA
sine of the vertex half-angle of the largest cone of meridional rays that can enter or leave the
core of an optical waveguide, multiplied by the refractive index of the medium in which the
cone is located.
3.4
far field pattern
FFP
angular distribution of light radiating from a waveguide’s core, which corresponds to the
optical power distribution on a plane normal to the waveguide axis some distance from its end
facet
Note 1 to entry: The distance depends on the largest waveguide cross-section, a, the wavelength, lambda and the
angle,ϕ, to the optical axis. It is abbreviated to FFP. In the far field region the shape of the distribution does not
change as the distance from the waveguide end facet increases; the distribution only scales in size with distance, L.
2a(cosϕ)
L>>
λ
3.5
far field image
far field pattern formed on an imaging device
3.6
centroid
optical centre of the far field image
3.7
neutral density filter
ND
filter that attenuates light of all colours equally
4 Standard atmospheric conditions
The standard atmospheric conditions are specified in IEC 61300-1.
5 Apparatus
5.1 General
The optical source multimode waveguide shall be long enough to ensure that all cladding
modes are stripped by passage through the waveguide. Often the fibre coating or tight buffer
is sufficient to perform this function. Alternatively a cladding mode stripper shall be used in
the source launch optical multimode fibre. An example of a typical cladding mode stripper
which would be suitable for optical fibre is sufficient windings of the fibre around a mandrel of
an appropriate diameter. The windings also have a more important essential effect to fully fill
the transverse modes across the maximum mode field diameter. It should be checked that all
of the transverse modes of the fibre are sufficiently well excited. This can be done by
comparing the FFPs for different lengths of the launch fibre or different light sources. Once
the FFP no longer changes in form as the launch fibre length is increased there is no need to
increase the length further.
– 8 – IEC 61300-3-53:2015 © IEC 2015
5.2 Measurement method 1: fθ lens imaging
5.2.1 General
In theory, this measurement method, which is effectively a coherent optical method to Fourier
Transform the near field to the far field using a lens, does not operate well using very
wideband optical sources. Experimentally it has been shown to operate sufficiently well for
sources up to 30 nm bandwidth which are most commonly used.
Figure 1 below shows the apparatus configuration. The measurement system consists of a
micro-positioner, a far field broadband optical system, a camera and computer (beam analysis
module). An appropriate type of camera (detector) should be chosen to suit the wavelength.
FFP optical system
Camera
(image sensor)
Optical fibre
Micro-positioner
Computer
(EAF analyser module)
IEC
Figure 1 – Apparatus configuration: Measurement method 1: fθ lens imaging
5.2.2 Micro-positioner
The micro-positioner shall have a function of fixing an optical waveguide and moving in three
directions (X, Y, Z). In addition yaw and pitch controls are recommended.
5.2.3 FFP optical system
As shown in Figure 2, basically, an fθ lens can directly convert input the light from the
multimode waveguide to a far field image, however, scaling the far field image in order to fit
the image sensor in the camera and adjustment of the light intensity in order to prevent
saturation may be required. The FFP optical system shall be chosen to operate at the
measurement wavelength across the required measurement bandwidth to match that of the
detection system. See Annex A for more information.
fθ objective lens Field lens
Imaging relay lens
IEC
Figure 2 – Far field optical system diagram
5.2.4 Camera
Although the detector is typically a charge-coupled device (CCD) or a complementary metal
oxide semiconductor (CMOS) camera, other types of array cameras may be considered. The
type of image sensor shall be chosen by the measurement wavelength. Absolute radiometric
measurement of flux (optical power flow) is not required.

5.2.5 Computer (EAF analyser module)
Since the acquired image contains many thousands of pixels, and the image conversion into
encircled angular flux requires substantial computation, a computer is required. The computer
will usually be connected to the image sensor through an image acquisition board (or with an
embedded image acquisition circuit) and installed beam analysis software.
5.2.6 Calibration light source
Calibration light source is used when calibrating the apparatus in Clause 7. The calibration
source is assumed to be broadband and incoherent so that speckle is not a problem, and to
have a sufficiently symmetrical far field distribution so that the calculated centroid of the far
field indicates the location of the optical centre axis of the waveguide with sufficient accuracy
for the purposes of this standard.
5.3 Measurement method 2: direct imaging
5.3.1 General
There are three alternative methods to detect the far field. One uses a detector, one uses a
single-mode fibre and the other uses a camera.
5.3.2 Micro-positioner
Both the input step index multimode waveguide source and the photo detector (PD) shall be
mounted on high precision motorized translation stages for accurate alignment with sub-
micron step adjustment to maximize the light through the waveguide.
5.3.3 Optical power
The output from the multimode waveguide shall be set to a power level of 0 dBm.
5.3.4 Alignment
Firstly, the input waveguide and detector shall be properly aligned to obtain the maximum
output power.
5.3.5 Detector
An integrating sphere PD preceded by a pinhole shall be placed sufficiently far from the
optical source launch multimode waveguide facet so as to be in the Fraunhofer or far field.
The Fraunhofer far field occurs when L >> D /λ where L is the distance of the detection plane
from the waveguide end facet, D is the diameter of the multimode waveguide core or strictly
mode field diameter and λ is the wavelength. For example, a large area integrating sphere PD
preceded by a pinhole, shown in Figure 3, shall be used to measure the integrated output
optical power so avoiding inconsistencies due to laser speckle and spatial variation of
efficiency across the photodiode detector. In this method the integrating sphere and its
pinhole are moved in X and Y to sample the far field. This has the advantage that a very large
area can be sampled. Moreover, it can also be moved in an arc on a goniometer so that its
input facet always faces the centre of the core of the multimode waveguide output. This
goniometric method can also be used to calibrate the far field in the fθ imaging method as the
far field is measured directly as a function of angle. If the detector aperture is instead moved
across an XY plane then the lateral position from the optical axis shall be converted to an
angle of divergence from the optical axis. The angle is the arctangent of the ratio of the lateral
X or Y position to the distance L. Therefore, considerable care needs to be taken to
accurately measure L.
– 10 – IEC 61300-3-53:2015 © IEC 2015
Pin hole
Integrating
L
Waveguide
sphere PD
(optical fibre)
Controller
Computer
(EAF analyser module)
Micro- Motorized micro-
positioner
positioner
IEC
Figure 3 – Apparatus configuration: measurement method 2 –
Direct imaging using an integrating sphere
5.3.6 Single-mode fibre
The single-mode optical fibre shall be placed sufficiently far from the optical source launch
multimode waveguide facet so as to be in the Fraunhofer or far field. The Fraunhofer far field
occurs when L >> D /λ where L is the distance of the detection plane from the waveguide end
facet, D is the diameter of the multimode waveguide core or strictly mode field diameter and λ
is the wavelength. For example, a single-mode fibre attached to a detector, shown in Figure 4,
shall be placed in the far field and moved in X and Y to sample the far field. This has the
advantage that a very large area can be sampled. Moreover, it can also be moved in an arc
on a goniometer so that its input facet always faces the centre of the core of the multimode
waveguide output. This goniometric method can also be used to calibrate the far field in the fθ
imaging method as the far field is measured directly as a function of angle. If the single-mode
fibre core is instead moved across an XY plane then the lateral position from the optical axis
shall be converted to an angle of divergence from the optical axis. The angle is the arctangent
of the ratio of the lateral X or Y position to the distance L. Therefore, considerable care needs
to be taken to accurately measure L.
Single-mode optical fibre
L
Waveguide
(optical fibre)
PD
Controller
Computer
Micro-
Motorized micro-
(EAF analyser module)
positioner
positioner
IEC
Figure 4 – Apparatus configuration: measurement method 2 –
Direct imaging using a single-mode fibre
5.3.7 Imaging device
An imaging device plane without any lens system shall be placed sufficiently far from the
optical source launch multimode waveguide facet so as to be in the Fraunhofer or far field.
The Fraunhofer far field occurs when L >> D /λ where L is the distance of the detection plane
from the waveguide end facet, D is the diameter of the multimode waveguide core or strictly
mode field diameter and λ is the wavelength. For example, an imaging device, shown in
Figure 5, shall be placed L away from the exit facet of the multimode waveguide. The distance
L between the imaging device and the waveguide end facet is much larger than the core size
of the waveguide, so the field captured is the far field distribution. The imaging device may for
example, be a CCD camera with its lens removed so that the light distribution falls directly on
the CCD chip. The lateral position from the optical axis in the far field shall be converted to an
angle of divergence from the optical axis. The angle is the arctangent of the ratio of the lateral
X or Y position to the distance L. Therefore, considerable care needs to be taken to
accurately measure L.
L
Camera
Waveguide
(optical fibre)
Controller
Computer
Micro-
Motorized micro-
(EAF analyser module)
positioner
positioner
IEC
Figure 5 – Apparatus configuration: measurement method 2 –
Direct imaging using an imaging device
6 Sampling and specimens
Light sources to be tested shall be chosen and prepared by the user of this standard, who
shall document the sampling and preparation procedures used. The only requirements on the
light sources under test are that they have an operating wavelength compatible with the
detector and fθ lens, and have optical connectors or splices compatible with the input port of
the apparatus. The construction details of the light sources are otherwise unspecified.
7 Geometric calibration
Calibration of the apparatus is critical to the accuracy of this measurement procedure.
Calibration shall be performed periodically. If the calibration is known to drift significantly
during a measurement interval, the drift of the source(s) shall be identified and eliminated. If
the apparatus is disassembled or its components in or affecting the optical path are otherwise
manipulated, calibration shall be performed before measurements are made.
The purpose of geometric calibration is to obtain the measurement data needed to compute
the conversion factor. The factor will be used to convert camera coordinates to light launching
angle relative to the optical axis of optical waveguide.
Calibration is performed to measure the conversion factor that relates the light launching
angle to the pixel of the detector corresponding to this angle. The factor has a unit of degree
per pixel, and will be used to convert camera coordinates to far field angle coordinates. The
collimated light source for geometric calibration, shown in Figure 6, shall have a spectral
power distribution similar to that of the measurement light source and the central wavelength
within 30 nm around the nominal wavelength of the measurement light source.
An example of the calibration procedure is stated below:
Step 1 Set a collimated light source whose incident angle relative to the optic axis of the far
field optical system can be precisely controlled. An example of the calibration apparatus is
shown in Figure 6.
Step 2 Measure the conversion factors from the whole range of angles to be measured with
an interval small enough (e.g. 1°) to enable accurate interpolation.

– 12 – IEC 61300-3-53:2015 © IEC 2015
Collimated light
Far field
Mirror
optical system
Precise goniometer
IEC
Figure 6 – Calibration apparatus example
Alternatively the direct imaging methods described in Clause 5 may be used for calibration.
8 Measurement procedure
8.1 Safety
All procedures in which an LED or a laser source is used as the optical source shall be
carried out using safety precautions in accordance with IEC 60825-1.
8.2 Far field image acquisition
8.2.1 General
Acquiring an image is central to the measurement of encircled angular flux. The approach to
image acquisition depends on the general characteristics of the light source being measured.
8.2.2 Waveguide end-face alignment
A waveguide end-face is placed at the front focal point of the FFP optical system. The live far
field image acquired on the computer display is adjusted to be in the centre of the display
using the X and Y axes of the micro-positioner, and to a minimum diameter and in focus using
the Z axis of the micro-positioner in 5.2.2.
8.2.3 Light source image acquisition
Measurement light sources are sufficiently incoherent and are sufficiently intense to easily get
good dynamic range, although attenuation may be required using ND filter. The acquired
image should be shown in the PC display as in Figure 7. The picture may be displayed with
false colour in Figure 8.
IEC
Figure 7 – Acquired far field image
IEC
Figure 8 – Acquired far field image with false colour
8.3 Removal of background noise
The dark current of the camera which is acquired by obscuring the input light beforehand shall
be removed from the acquired image, or 0,5 % intensity of the peak power in the acquired
image shall be set as a threshold level to keep the parts of the image above this threshold.
8.4 Centre determination
8.4.1 General
One of the two methods needs to be used.
8.4.2 Method A: Optical centre determination
The encircled angular flux is computed with respect to the optical centroid of the FFP
distribution. As shown in Figure 9, the centroid of the acquired image shall be determined with
the use of Equation (1).
– 14 – IEC 61300-3-53:2015 © IEC 2015
y
y’
x
O
O’ x’
IEC
Figure 9 – Optical centre determination

 x′ I(x′, y′) y′ I(x′, y′)
∑ ∑ ∑ ∑
 
x′ y′ x′ y′
(1)
′ ′ ′
O(x= 0, y= 0)= O(x = 0, y = 0)− ,
 
′ ′ ′ ′
I(x , y) I(x , y)
∑∑ ∑∑ 
x′ y′ x′ y′
 
where
O’ is the origin of FFP optical system;
O is the calculated centroid of the acquired image;
(x’, y’) are the x-y coordinates based on the FFP optical system origin;
I(x’, y’) is the light intensity at coordinate (x’, y’).
8.4.3 Method B: Mechanical centre determination
The encircled angular flux is computed with respect to the optical central axis of the
measurement optics. The optical central axis of the measurement optics, O , shall be
m
determined by measuring the far field pattern of a reference waveguide. The reference
waveguide shall be a single-mode fibre and the end-face of the fibre should be perpendicular
to the optical axis.
 ′ ′ ′ ′ ′ ′ 
x I(x , y ) y I(x , y )
∑ m∑ m m ∑ m∑ m m
 
x′ y′ x′ y′
O (x = 0, y = 0)= O′(x′ = 0, y′ = 0)− , (2)
 
m m m m m m
′ ′ ′ ′
I(x , y ) I(x , y )
 ∑∑ ∑∑ 
m m m m
x′ y′ x′ y′
 
For method B, O’ shall be fixed during a series of measurements.
m
8.5 Computation of encircled angular flux
Before computation of encircled angular flux, the x-y coordinates are converted to polar
coordinates using r and ϕ as shown in Figure 10(b). Applying r and ϕ to the encircled flux
equation, light intensity distribution on an FFP screen is described in Equation (3).

y
r
max
I(r,φ)
r
max
r'
r
φ
SI-MMF
r
θ
x
2θ
max
d
f
a) b)
IEC
Figure 10 – Coordinate conversion to polar coordinate on the image sensor plane

′
2𝜋𝜋 𝑟𝑟
𝐼𝐼(𝑟𝑟,𝜑𝜑)∙𝑟𝑟∙𝑑𝑑𝑟𝑟∙𝑑𝑑𝜑𝜑
∫ ∫
′ 0 0
𝐸𝐸𝐸𝐸(𝑟𝑟 ) = (3)
2𝜋𝜋 𝑟𝑟
𝑚𝑚𝑚𝑚𝑚𝑚
( )
∫ ∫ 𝐼𝐼𝑟𝑟,𝜑𝜑∙𝑟𝑟∙𝑑𝑑𝑟𝑟∙𝑑𝑑𝜑𝜑
0 0
Equation (4) is a simple equation that shows the relationship between r, θ and d , and its
f
differential form (5):
𝑟𝑟 =𝑑𝑑 ·𝑡𝑡𝑡𝑡𝑡𝑡(𝜃𝜃) (4)
𝑓𝑓
2 −3
𝑟𝑟 · d𝑟𝑟 =𝑑𝑑 · 𝑠𝑠𝑠𝑠𝑡𝑡(𝜃𝜃) · 𝑐𝑐𝑐𝑐𝑠𝑠 (𝜃𝜃) · 𝑑𝑑𝜃𝜃 (5)
Replacing r withθ using Equation (4) and (5), Equation (6) is obtained. This shows encircled
angular flux EAF(θ′).
′
2𝜋𝜋 𝜃𝜃 𝑠𝑠𝑠𝑠𝑠𝑠(𝜃𝜃)
𝐼𝐼(𝑟𝑟,𝜑𝜑)∙ ∙𝑑𝑑𝑑𝑑𝑑𝑑𝜑𝜑
∫ ∫
0 0 3
( )
𝑐𝑐𝑐𝑐𝑠𝑠 𝜃𝜃
′
𝐸𝐸𝐴𝐴𝐸𝐸(𝜃𝜃 ) = (6)
2𝜋𝜋 𝜃𝜃 𝑠𝑠𝑠𝑠𝑠𝑠(𝜃𝜃)
𝑚𝑚𝑚𝑚𝑚𝑚
∫ ∫ 𝐼𝐼(𝑟𝑟,𝜑𝜑)∙ ∙𝑑𝑑𝑑𝑑𝑑𝑑𝜑𝜑
0 0
𝑐𝑐𝑐𝑐𝑠𝑠 (𝜃𝜃)
where
r is the radial distance from the origin corresponding to an angle between one ray
emitted from the multimode waveguide and the optical axis of the multimode
waveguide;
r is the radial distance from the origin corresponding to the maximum ray angle
max
which is approximately 30° for category A3 multimode fibre for example;
ϕ  is a circular angle in polar coordinates;
θ is an angle between one ray emitted from the multimode waveguide and the
optical axis;
θ is the maximum ray angle which is approximately 30° for category A3 multimode

max
fibre for example;
d  is the distance between the end of multimode optical wave guide and FFP screen.
f
O and O are the calculated centroids discussed in 8.4.
m
An example of EAF is shown in Figure 11.

FFP screen
– 16 – IEC 61300-3-53:2015 © IEC 2015
1,0
0,8
0,6
0,4
0,2
0,0
0 10 20 30
Angle θ°  (deg)
IEC
Figure 11 – Standard encircled angular flux chart
9 Results
9.1 Information available with each measurement
Report the following with each measurement:
• date and time of measurement;
• identification of source;
• nominal wavelength of source;
• method of centre determination;
• the encircled angular flux at each angle shall be reported after a series of measurements
is completed;
• EAF as a graph as a function of angle θ (Figure 11), including any specified template
limits.
For method B specify the single-mode fibre and multimode fibre connectors and their lateral
and angular tolerances, if the measurements are referenced to the connector.
9.2 Information available upon request
The following information shall be available upon request:
• date of most recent calibration of equipment;
• method of calibration of equipment;
• the integration limit parameters (larger than the angle corresponding to the NA of DUT and
less than the field of view);
• the original images used in the computations;
• the derived centre, and if different, the centroid image;
• the angular data functions computed in 8.5.

EAF
10 Details to be specified
The following details, as applicable, shall be stated in the relevant specification:
• type of source to be measured;
• sampling requirements, if any;
• criteria to be met by sources;
• any deviations to the procedure that may apply;
• angle θ at which the EAF is to be reported;
• the EAF template used to report results;
• measurement uncertainty.
– 18 – IEC 61300-3-53:2015 © IEC 2015
Annex A
(informative)
System requirements: measurement method 1 –
Field optical system
A.1 General
An fθ lens can directly convert the distribution of intensity as a function of input light angle to
the distribution of intensity as a function of radius in the far field. However, scaling the far
field image in order to fit the image sensor in the camera may be required. In addition,
adjustment of the input light intensity in order to prevent the saturation of the image sensor
may also be required using an ND filter. Accordingly the far field optical system consists of an
fθ (telecentric) optical system and imaging optical system (relay lens). An ND filter may be
placed at the filter port.
Imaging relay lens
fθ objective lens
Field lens
CCD
Filter port
IEC
Figure A.1 – An example of an optical system using an fθ lens
A.2 Requirements
Requirements of the far field optical system are as follows:
Main lens system:                        fθ objective lens;
Range of measurement angle to the optical axe: ±40° (NA = 0,64);
Resolution of measurement angle:            0,1° or less.

Annex B
(informative)
System requirements: measurement method 2 –
Direct imaging
B.1 General
The principle of this measurement method is that light diverges from the step index multimode
waveguide connected to the light source and this light is allowed to diverge in free space
without passing through any lenses, prisms, apertures or other optical elements before it
impinges on the photodiode or CCD or CMOS detector apart from the case of the integrating
sphere where multiple internal reflections are permitted.
B.2 Requirements
An imaging device plane without any lens system shall be placed sufficiently far from the
optical source launch multimode waveguide facet so as to be in the Fraunhofer or far field.
The Fraunhofer far field occurs when L >> D /λ where L is the distance of the detection plane
from the waveguide end facet, D is the diameter of the multimode waveguide core (or strictly
mode field diameter) and λ is the wavelength. The distance L between the imaging device and
the wa
...