IEC 63267-3-61:2025

IEC 63267-3-61 ®
Edition 1.0 2025-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic interconnecting devices and passive components - Fibre optic
connector optical interfaces for enhanced macrobend multimode fibres -
Part 3-61: Connector parameters of physically contacting 50 μm core diameter
fibres - Non-angled 2,5 mm and 1,25 mm diameter cylindrical full zirconia
ferrules for reference connection applications

Dispositifs d'interconnexion et composants passifs fibroniques - Interfaces
optiques des connecteurs fibroniques pour fibres multimodales améliorées en
macrocourbures -
Partie 3-61: Paramètres de connexion des fibres d’un diamètre de cœur de 50
μm en contact physique - Férules cylindriques non inclinées en zircone plein de
2,5 mm et 1,25 mm de diamètre, pour les applications de connexion de référence
ICS 33.180.20  ISBN 978-2-8327-0505-6

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CONTENTS
FOREWORD . 2
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Attenuation grade . 5
5 Description . 5
6 Criteria for a fit within the reference performance grade . 6
6.1 Geometry of reference plug after termination . 6
6.2 Use of selected fibre in reference-grade connectors . 8
7 Reference adapter . 9
Annex A (informative) Attenuation test limits of reference grade R connectors to
m1
grade B connectors . 10
m
A.1 General . 10
A.2 Performance grade B test limit against R reference connector . 10
m m1
A.3 Calculated attenuation of random mated Grade R reference connections . 10
m1
Annex B (normative) Maximum allowed spherical fibre undercut . 12
Bibliography . 14

Figure 1 – Geometrical requirements for fibre core location after termination relative to
the ferrule axis and the connector plug key . 6
Figure 2 – Interface dimensions for PC ferrule . 7
Figure A.1 – Calculated attenuation of random mated Grade R reference connectors . 11
m1
Figure B.1 – Allowable undercut as a function of endface radius and apex offset –
4,9 N minimum contact force . 13
Figure B.2 – Allowable undercut as a function of end face radius and apex offset –
2,9 N minimum contact force . 13

Table 1 – Multimode attenuation grade at 850 nm . 5
Table 2 – Optical interface parameter values for 2,5 mm diameter PC ferrules for
multimode reference connectors grade R . 8
m1
Table 3 – Optical interface parameter values for 1,25 mm diameter PC ferrules for
multimode reference connectors grade R . 8
m1
Table A.1 – Performance grade test limits at 850 nm . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Fibre optic interconnecting devices and passive components - Fibre optic
connector optical interfaces for enhanced macrobend multimode fibres -
Part 3-61: Connector parameters of physically contacting 50 μm core
diameter fibres - Non-angled 2,5 mm and 1,25 mm diameter cylindrical
full zirconia ferrules for reference connection applications

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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IEC 63267-3-61 has been prepared by subcommittee 86B: Fibre optic interconnecting devices
and passive components, of IEC technical committee 86: Fibre optics. It is an International
Standard.
This first edition and the first edition of IEC 63267-2-2 cancel and replace the first edition of
IEC 61755-6-2 published in 2018. This edition constitutes a technical revision. The document
includes the following significant technical changes with respect to the previous edition:
a) Definition of a reference grade, R interface;
m1
b) Inclusion of A1-OM2b to A1-OM5b fibres;
c) Updates to normative references;
d) The addition of Annex A, which describes the attenuation test limits of reference grade R
m1
connectors to grade B connectors;
m
e) A new Annex B that describes the allowable fibre undercut.
The text of this International Standard is based on the following documents:
Draft Report on voting
86B/5030/FDIS 86B/5075/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
A list of all parts in the IEC 63267-3-61 series, published under the general title Fibre optic
interconnecting devices and passive components – Fibre optic connector optical interfaces for
enhanced macrobend multimode fibres, can be found on the IEC website.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
1 Scope
This part of the IEC 63267 series defines the dimensional limits of an optical interface for
reference connectors with 2,5 mm or 1,25 mm diameter cylindrical zirconia (ZrO ) ferrules
necessary to meet specific requirements for fibre-to-fibre interconnection of non-angled
polished multimode reference connections as defined in IEC 63267-2-2.
Ferrule dimensions and features are contained in the IEC 61754 series of fibre optic connector
interface standards.
One grade of reference connector, R , is defined in this document. The reference connector
m1
is terminated to restricted IEC 60793-2-10 using A1-OM2b to A1-OM5b fibre in 850 nm band
only.
The geometrical dimensions and tolerances of the specified reference connector have been
developed primarily to limit the variation in measured attenuation between multiple sets of
reference connectors, and therefore to reduce the variation in measured attenuation between
an arbitrarily chosen reference connector when mated with a connector in the field or factory.
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 60793-2-10, Optical fibres – Part 2-10: Product specifications – Sectional specification for
category A1 multimode fibres
IEC 61300-3-4, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-4: Examinations and measurements – Attenuation
IEC 61300-3-42, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-42: Examinations and measurements – Attenuation of single
mode alignment sleeves and or adapters with resilient alignment sleeves
IEC 63267-1, Fibre optic interconnecting devices and passive components – Fibre optic
connector optical interfaces – Part 1: Enhanced macro bend loss multimode 50 µm core
diameter fibres – General and guidance
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 63267-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
4 Attenuation grade
This document currently only specifies one attenuation grade, however, the construction of the
document allows inclusion for other multimode reference grades for cylindrical ferrules in the
future, if necessary.
The performance grade for physical contact non-angled polished reference connectors detailed
in this document is shown in Table 1.
The specified attenuation for the grade is obtained when the reference plug is connected to
other reference plugs in a reference adapter, and the attenuation is measured in accordance
with IEC 61300-3-4 (insertion method B).
Table 1 – Multimode attenuation grade at 850 nm
Reference grade Attenuation Contribution to measurement
a
uncertainty
(dB)
(dB)
R ≤ 0,1 ± 0,071
m1
NOTE The maximum attenuation of reference grade connections mated to standard grade connections is
described in Annex A.
a
As described in IEC 63267-2-2, related to the measurement of the attenuation between any connector
according the IEC optical interface standards and a population of reference connectors.

5 Description
Optical reference connectors are connectors manufactured with restricted dimensional
tolerances on dimensions that contribute to lateral and angular offset of such optical
connections. These connectors are mainly used for attenuation measurement purposes and
shall be considered as part of the measurement setup. The goal is to strongly reduce the
measurement uncertainty. The attenuation uncertainties due to the reference connectors are
defined in IEC 63267-2-2.
The performance of a multimode optical interface is not only determined by the alignment
accuracy of the optical datum targets of two mating fibres, but also by any fibre parameter
mismatches. There are three conditions affecting the alignment of two optical datum targets:
lateral offset, angular offset and longitudinal offset.
Parameters influencing the lateral and angular offset of the optical fibre axes include the
following:
• ferrule outside diameter;
• fibre hole true position;
• fibre hole angle relative to ferrule axis;
• fibre cladding diameter to fibre hole inner diameter;
• alignment sleeve inside diameter;
• fibre core eccentricity relative to the fibre cladding diameter.
Parameters influencing the fibre-to-fibre intrinsic attenuation include:
• core diameter mismatch (CD);
• numerical aperture mismatch (NA);
• core non-circularity;
• alpha profile mismatch;
• refractive index mismatch.
The last three parameters are not considered in the development of this standard.
Parameters influencing the connector plug end face deformation requirements necessary to
maintain the physical contact of the ferrules within a mated connection are as follows:
• end face spherical radius;
• end face spherical radius apex offset;
• fibre undercut;
• axial force on ferrule end face;
• ferrule and fibre material physical constants;
• alignment sleeve frictional force.
6 Criteria for a fit within the reference performance grade
6.1 Geometry of reference plug after termination
The end face dimensions for meeting the performance grade as listed in Table 1, are shown
Figure 1 and Figure 2. The parameter requirements are defined in Table 2 for 2,5 mm diameter
ferrules and Table 3 for 1,25 mm diameter ferrules. All multimode reference connectors shall
be terminated on restricted multimode (MM) A1-OM2b to A1-OM5b, as specified in
IEC 60793-2-10 and subclause 6.2.
The end face geometry for radius, dome offset and fibre protrusion after polishing shall meet
the requirements as specified in Table 2 for 2,5 mm ferrules and Table 3 for 1,25 mm ferrules.
Fibre undercut limits for both ferrule types are given in Annex B.

Key
F Fibre core eccentricity
Figure 1 – Geometrical requirements for fibre core location after termination
relative to the ferrule axis and the connector plug key
Key
A Fibre undercut or protrusion
B End face spherical radius
C End face spherical radius apex offset
D Ferrule outside diameter
E Angle of fibre axis
Figure 2 – Interface dimensions for PC ferrule
Table 2 – Optical interface parameter values for 2,5 mm diameter
PC ferrules for multimode reference connectors grade R
m1
Dimensions
Reference Unit Remarks
Min. Max.
a b
–100 nm Fibre undercut or protrusion
A
B 5 30 mm Spherical radius
C 0 50 µm Apex offset
D 2,498 5 2,499 5 mm Outside diameter
E 0 0,2 ° Angle of fibre axis
F 0 0,000 5 mm radius
NOTE 1 The core location (F) and tilt angle (E) values specified in this standard have been calculated to ensure
that the attenuation values for Grade R are met under all circumstances.
m1
NOTE 2 Limiting the fibre core/cladding eccentricity of the fibre can be necessary to achieve the required
maximum core location (F).
NOTE 3 Refer to IEC 61300-3-47 for end face geometry measurement of PC spherically polished ferrules using
interferometry.
a
A as a negative value indicates fibre protrusion.
b
See Annex B for details.
Table 3 – Optical interface parameter values for 1,25 mm diameter PC
ferrules for multimode reference connectors grade R
m1
Dimensions
Reference Unit Remarks
Min Max
a b
– 100 nm Fibre undercut or protrusion
A
B 5 30 mm Spherical radius
C 0 50 µm Apex offset
D 1,248 5 1,249 5 mm Outside diameter
E 0 0,2 Angle of fibre axis
°
F 0 0,000 5 mm radius
NOTE 1 The core location (F) and tilt angle (E) values specified in this standard have been calculated to ensure
that the attenuation values for Grade R are met under all circumstances.
m1
NOTE 2 Limiting the fibre core/cladding eccentricity of the fibre can be necessary to achieve the required
maximum core location (F).
NOTE 3 Refer to IEC 61300-3-47 for end face geometry measurement of PC spherically polished ferrules using
interferometry.
a
A as a negative value indicates fibre protrusion.
b
See Annex B for details.
6.2 Use of selected fibre in reference-grade connectors
Restricted A1-OM2b to A1-OM5b fibre of IEC 60793-2-10 shall be used with a core diameter of
50 µm ± 0,5 µm and a numerical aperture of 0,200 ± 0,002 to minimise the variability of
attenuation measurements using reference connectors.
7 Reference adapter
To qualify reference adapters, it is recommended to use reference connector plugs as defined
in this document and measure the attenuation of the adapter in accordance with IEC 61300-3-42
with an attenuation variation smaller than 0,03 dB.
Although the title of IEC 61300-3-42 refers to single mode alignment sleeves, the method also
applies to multimode types.
Annex A
(informative)
Attenuation test limits of reference grade R
m1
connectors to grade B connectors
m
A.1 General
Reference connectors are specified with tight tolerances for the purpose of reducing
measurement uncertainty and are used mainly as a quality assurance screening tool in
production or in the field to validate an installation. Use of these reference connectors is not
normative; however, when the reference connectors described in this document are used, the
specified test limit for grade B connectors is normative.
m
NOTE This can be used to inspect for failure modes such as fractured fibres, mechanical stresses, microbending
or macrobending (assuring optical functionality).
A.2 Performance grade B test limit against R reference connector
m m1
The specified attenuation test limit for connector performance grade B against reference
m
connectors, R , measured in accordance with IEC 61300-3-4 (insertion method B), is given in
m1
Table A.1.
Table A.1 – Performance grade test limits at 850 nm
Reference grade Reference connector-to- grade B
m
standard connector attenuation test limit
(dB)
R 0,40
m1
A.3 Calculated attenuation of random mated Grade R reference connections
m1
The attenuation of random mated Grade R reference connections for 2,5 mm and 1,25 mm
m1
PC ferrules is expected to be lower than 0,1 dB, when measured using a reference adapter.
See Figure A.1.
The selected fibre geometry parameters NA and CD, as well as the eccentricity of the fibre core
in the reference plug are assumed to be uniformly distributed.
Figure A.1 – Calculated attenuation of random mated Grade R reference connectors
m1
Annex B
(normative)
Maximum allowed spherical fibre undercut
The maximum allowed spherical fibre undercut, A (see Figure B.1 and Figure B.2), is
maximum
determined by the interaction of the parameters influencing the longitudinal offset of the optical
fibre axes as defined by Formula (B.1).
k 6 26 2 3
A =kB⋅ − B⋅+10 B⋅−10 C ⋅10− D − D
 (B.1)
maximum 1 DTE PFW

where
A is the maximum spherical undercut for physical contact (nm);
maximum
k is the coefficient based on ferrule contact force and material properties;
k is the exponent based on ferrule contact force and material properties;
B is the endface spherical radius (mm);
C is the apex offset from fibre axis (μm);
D is the differential thermal expansion between the ferrule material and the silica fibre
DTE
at maximum operating temperature (nm);
D is the permanent fibre withdrawal that exceeds the transient fibre movement
PFW
predicted by the first three terms in Formula (B.1) (nm).
Endface deformation term as a function of contact force, endface radius and material properties
is shown in Formula (B.2):
k
(B.2)
kB⋅
Geometric compensation term for the offset of the ferrule apex from the fibre axis is shown in
Formula (B.3):
6 26 2 3
B⋅+10 BC⋅−10 ⋅10
(B.3)


-0,795
( ) 6  2 62 3
A =1 988× B − B×+10 BC×−10 ×10 − 60
 
Maximum
 
Figure B.1 – Allowable undercut as a function of endface radius and apex offset –
4,9 N minimum contact force
-0,795 6 2 6 2 3
A =1 798× BB− ×+10 B ×−10 C ×10 − 60

Maximum

Figure B.2 – Allowable undercut as a function of end face radius and apex offset –
2,9 N minimum contact force
Bibliography
IEC 61300-3-47, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-47: Examinations and measurements – End face geometry
of PC/APC spherically polished ferrules using interferometry
IEC 61754 (all parts), Fibre optic interconnecting devices and passive components – Fibre optic
connector interfaces
IEC 63267-2-1, Fibre optic interconnecting de
...