IEC 61300-3-47:2014

IEC 61300-3-47 ®
Edition 1.0 2014-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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

Dispositifs d’interconnexion et composants passifs fibroniques – Procédures
fondamentales d’essais et de mesures –
Partie 3-47: Examens et mesures – Géométrie de l’extrémité des férules PC/APC
polies de façon sphérique par interférométrie

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IEC 61300-3-47 ®
Edition 1.0 2014-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
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

Dispositifs d’interconnexion et composants passifs fibroniques – Procédures

fondamentales d’essais et de mesures –

Partie 3-47: Examens et mesures – Géométrie de l’extrémité des férules PC/APC

polies de façon sphérique par interférométrie

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.20 ISBN 978-2-8322-7188-9

– 2 – IEC 61300-3-47:2014 © IEC 2014
CONTENTS
CONTENTS . 2
FOREWORD . 3
1 Scope . 5
2 Terms and definitions . 5
3 Measurement by interferometer . 7
3.1 General . 7
3.2 Ferrule/connector holder . 7
3.3 Optical interferometric system . 8
3.4 Microscope with camera. 8
4 Requirements for the interferometer . 8
4.1 XY calibration (radius of curvature) . 8
4.2 Z calibration (fibre height) . 8
4.3 Alignment of ferrule axis with the interferometer’s optical axis (apex offset
calibration) . 8
4.4 Tilt and key angle . 8
5 Measurement method . 8
5.1 General . 8
5.2 Measurement regions . 8
5.3 Measurement procedure for the radius of curvature . 9
5.4 Measurement procedure for the dome eccentricity (apex offset) . 10
5.5 Measurement procedure for fibre height . 10
6 Details to be specified . 13
Annex A (normative) Calibration for the interferometer . 14
A.1 XY calibration . 14
A.2 Z calibration . 14
A.3 Alignment of the ferule axis with the optical axis of the interferometer (“apex
offset calibration”) . 14
A.4 Tilt and key angle . 14
Annex B (informative) Measurement procedure for end face “angle error” of angled
convex polished ferrules . 15
Annex C (informative) Formula for calculating ferrule end face geometry . 17

Figure 1 – Radius of curvature of a spherically polished ferrule end face . 5
Figure 2 – Apex offset of a spherically polished ferrule end face . 6
Figure 3 – Fibre height of a spherically polished ferrule end face . 6
Figure 4 – Ferrule end face angle for spherically polished ferrules . 7
Figure 5 – Interferometer . 7
Figure 6 – Ferrule end face and measurement regions . 9
Figure 7 – Ferrule end face surface . 11
Figure 8 – Fitting region and averaging region of the ferrule end face surface . 11
Figure 9 – Converted end face surface of the ferrule . 12
Figure 10 – Converted ferrule end face surface without the extracting region . 12
Figure B.1 – Example of key error calculated from interference pattern for a convex
polished ferrule . 15

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
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

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61300-3-47 has been prepared by subcommittee 86B: Fibre optic
interconnecting devices and passive components, of IEC technical committee 86: Fibre optics.
This standard merges IEC 61300-3-15, IEC 61300-3-16, IEC 61300-3-17 and IEC 61300-3-23.
After publication of this standard IEC 61300-3-15, IEC 61300-3-16, IEC 61300-3-17 and
IEC 61300-3-23 will be withdrawn.

– 4 – IEC 61300-3-47:2014 © IEC 2014
This bilingual version (2019-07) corresponds to the English version, published in 2014-07.
The text of this standard is based on the following documents:
FDIS Report on voting
86B/3773/FDIS 86B/3805/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 web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
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

1 Scope
This part of IEC 61300 describes a procedure to measure the end face geometry of a
spherically polished ferrule or connector. Within this standard the words “ferrule” and
“connector” can be used interchangeably.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
radius of curvature
B
radius of curvature of the portion of the spherically polished ferrule end face which is domed
for physical contact
Note 1 to entry: It is assumed that the end face is spherical, although in practice the end face is often aspherical
(see Figure 1).
Figure 1 – Radius of curvature of a spherically polished ferrule end face
2.2
apex offset
C
distance between the axis of the ferrule and the line parallel to the axis which passes through
the vertex (or highest point on the dome), formed by spherically polishing the ferrule, as
shown in Figure 2
– 6 – IEC 61300-3-47:2014 © IEC 2014

Figure 2 – Apex offset of a spherically polished ferrule end face
2.3
fibre height
average distance between the fibre end face and a virtual spherical surface which is fitted to
the spherically polished ferrule end face (see Annex C)
Note 1 to entry: It is assumed that a circular region of the ferrule end face, which is centred to the ferrule axis, is
spherical although in practice the end face is often aspherical. A positive value indicates fibre undercut (see
Figure 3a). A negative value indicates fibre protrusion (see Figure 3b).

Figure 3a – Fibre height +A
Figure 3b – Fibre height –A (protrusion)
Figure 3 – Fibre height of a spherically polished ferrule end face

2.4
end face angle
angle (θ) between the plane perpendicular to the axis of the ferrule, and the straight line
tangent to the polished surface at the fibre centre in the direction of the nominal angle (see
Figure 4)
Figure 4 – Ferrule end face angle for spherically polished ferrules
3 Measurement by interferometer
3.1 General
A typical interferometer configuration is shown in Figure 5. The apparatus consists of a
suitable ferrule/connector holder, an optical interferometric system combined with a
microscope and a camera.
Figure 5 – Interferometer
3.2 Ferrule/connector holder
This is a suitable device to hold the ferrule/connector in a fixed alignment position with
respect to the optical axis of the interferometer. The holder is designed such that the portion
of the ferrule closest to the end face is secured by the holder. The ferrule shall be aligned by
holding it over a distance of at least twice the ferrule diameter. The ferrules axis should be
adjustable in order to make it parallel to the optical axis of the interferometer. Alternatively,
this can be carried out by positioning the reference mirror of the interferometer. For angled
polished ferrules adjustments are necessary to align the polish angle axis with the optical axis
of the interferometer.
– 8 – IEC 61300-3-47:2014 © IEC 2014
3.3 Optical interferometric system
A suitable optical interferometric system (for example a Michelson interferometer) displays an
image with interference fringes of the ferrule’s end face.
3.4 Microscope with camera
The image of the end face is projected on to the camera with a minimum field of view of
250 µm. Software processes the image(s) and calculates the required parameters.
4 Requirements for the interferometer
4.1 XY calibration (radius of curvature)
The interferometer shall have the ability to measure the radius of curvature with measurement
uncertainty better than ±0,1 mm for radii from 5 mm to 30 mm. See Annex A.
4.2 Z calibration (fibre height)
The interferometer shall have the ability to measure the fibre height with measurement
uncertainty better than ±10 nm. See Annex A.
4.3 Alignment of ferrule axis with the interferometer’s optical axis (apex offset
calibration)
The interferometer shall have the ability to measure the apex offset with a maximum
difference of less than 5 µm between two measurements where the second measurement is
made after rotating the ferrule by 180°. See Annex A.
NOTE This test is only possible with non-angled ferrules.
4.4 Tilt and key angle
When measuring angled connectors, calibration of the holder position is required.
Measurement of a flat polished ferrule should have a measurement uncertainty better than
±0,1° for the key angle and ±0,03° for the tilt angle.
NOTE The key angle is the angular rotational misalignment between the ferrule mating surface of an angled end
face connector, and its design orientation angle with respect to its key (see Annex B).
5 Measurement method
5.1 General
For all measurements, the instrument should be adjusted such that
a) a sample is placed in the measurement holder,
b) the image of the ferrule end face in the fibre zone is seen on the monitor,
c) the interference fringes appear on the ferrule end face,
d) the ferrule axis is correctly aligned with the optical axis of the interferometer (“apex offset
calibration”),
e) all other instrument calibrations have been performed,
f) the system is configured according to the type of measurement to be performed (e.g. PC
or APC ferrule/connector).
5.2 Measurement regions
Three regions shall be defined on the ferrule end face for the measurement (see Figure 6).

a) Fitting region: the fitting region is set on the ferrule surface, and defined by a circular
region having a diameter, D, minus a circular region having a diameter, E, (the extracting
region). The fitting region shall be defined in order to cover the contact zone of the ferrule
end face when the ferrule is mated.
b) Extracting region: the extracting region, which includes the fibre end face region and the
adhesive region, is defined by a circle having a diameter E.
c) Averaging region: the averaging region is set on the fibre surface, and defined by a
circular region “having a diameter F”. This region is used for fibre height A averaging.
The 3 regions should be concentric on the ferrule axis. For connectors with 125 µm nominal
fibre diameter and a radius of curvature of nominally 5 mm to 30 mm, the values of the
diameters D, E and F are as follows:
D = 250 µm
E = 140 µm
F = 50 µm
Figure 6 – Ferrule end face and measurement regions
5.3 Measurement procedure for the radius of curvature
The following steps shall be taken:
a) Measure the surface of the end face with the interferometer, recording the three-
dimensional surface measurement data on its surface data processing unit (see Figure 7).

– 10 – IEC 61300-3-47:2014 © IEC 2014
b) Correct the surface data, taking into account the refractive indices and the absorption
coefficients of the fibre and the ferrule.
c) Using the data from the fitting regions, calculate the “best fit” radius of curvature
(Annex C).
5.4 Measurement procedure for the dome eccentricity (apex offset)
The following steps shall be taken:
a) Measure the surface of the end face with the interferometer, recording the three-
dimensional surface measurement data on its surface data processing unit (see Figure 7).
b) Correct the surface data, taking into account the refractive indices and the absorption
coefficients of the fibre and the ferrule.
c) From the analysis of the interference image(s) the normal distance between the centre of
the sphere (Annex C) fitted to the surface over the fitting region and the fibre axis shall be
measured. This value corresponds to the apex offset.
5.5 Measurement procedure for fibre height
The following steps shall be taken:
a) Measure the surface of the end face with the interferometer, recording the three-
dimensional surface measurement data on its surface data processing unit (see Figure 7).
b) Correct the surface data, taking into account the refractive indices and the absorption
coefficients of the fibre and the ferrule.
c) Using only the data within the averaging region and the fitting region evaluate A (see
Figure 7 to Figure 10 and Annex C).
The calculation shall be as follows:
1) Create a converted surface from the corrected surface data by subtracting the “best fit”
radius of curvature from the spherical surface data between the fitting region. The fitting
region of the converted surface may be flat when the ferrule end face has an ideal
spherical surface (See Figure 9).
2) Calculate an average surface height on the fibre averaging region and an average surface
height on the fitted ferrule portion from the converted surface. The fibre height, A, is
measured as the difference between the two average surface heights, as shown in
Figure 10. A positive value indicates fibre undercut. A negative value indicates fibre
protrusion.
Figure 7 – Ferrule end face surface

Figure 8 – Fitting region and averaging region of the ferrule end face surface

– 12 – IEC 61300-3-47:2014 © IEC 2014

Figure 9 – Converted end face surface of the ferrule

Figure 10 – Converted ferrule end face surface without the extracting region
The difference in refractive indices and the absorption coefficients between the ferrule and
the fibre should be taken into account when processing the measured surface data. If the
procedure is done without consideration of the difference, the procedure described in this
clause may not accurately show the fibre undercut or protrusion.

6 Details to be specified
The following details, as applicable, shall be specified in the relevant specification:
– Type of interferometry;
– Nominal angle of tilt, e.g. PC/APC;
– Instrument configuration (keying adapter, ferrule holder, etc.);
– Rotational tolerance of the ferrule position in the holder (key angular error);
– Any deviation from this method;
– Measurement uncertainty.
– 14 – IEC 61300-3-47:2014 © IEC 2014
Annex A
(normative)
Calibration for the interferometer
A.1 XY calibration
An XY calibration is required when the requirements of Clause 4 cannot be met.
The interferometer shall be calibrated in XY directions (if a Z calibration has already been
performed beforehand), by measuring an artifact with a spherical surface – previously
measured with a mechanical method. Example: contact gauge.
Alternatively an etched wafer with a calibrated grid pattern for the XY calibration can be used.
A.2 Z calibration
If the interferometer is based on the monochromatic phase-shifting method: use a step height
artifact with a nominal step height less than one-quarter of the wavelength of the light source
used in the interferometer.
If the interferometer uses the white-light interferometry method, use step height artifact with a
nominal step height of approximately one-quarter to three-quarters of the Z scanning range of
the interferometer.
A.3 Alignment of the ferule axis with the optical axis of the interferometer
(“apex offset calibration”)
The calibration for non-angled PC connectors is to measure the apex offset positions while
rotating the ferrule by (for example) 60° steps and calculating the centre made by the 6 apex
offset measurements by fitting a circle using the least-square fit method. Once calculated,
translate this point to the centre of the fibre by aligning the ferrule/connector holder or the
reference mirror of the interferometer. For angled connectors, see Clause A.4.
A.4 Tilt and key angle
Tilt and key angle calibration is required when angled connectors are measured and the
requirements of 4.4 cannot be met.
Two methods are used (reference procedure is b):
a) Calibrate the instrument as per Clause A.3 then rotate the connector holder or the optical
system by a calibrated nominal angle (e.g. 8°).
b) Calibrate the holder or mirror orientation with an artifact measured with a mechanical
method. Example: contact gauge. This artifact should simulate a connector with its
orientation key and compose of a flat tilted surface. For the key error compensation, a
software based compensation may be used.

Annex B
(informative)
Measurement procedure for end face “angle error”
of angled convex polished ferrules
For a convex polished ferrule, the radius of curvature, B, and the apex offset component in
the direction of the angle K are calculated from the analysis of the interferometric fringes (see
Figure B.1). The value of the angle error is calculated from the value of B and K (Equation
x
[B.1]). The value of the key error is calculated from the values of B and K (Equation [B.2]).
y
When measuring angled convex polished ferrules, in addition to tilting the connector with
respect to the interferometer, an adapter or keying mechanism should also be installed on the
interferometer. This keying mechanism is designed to constrain the rotational orientation of
the ferrule with respect to its k
...