IEC TR 62627-04:2012

IEC/TR 62627-04 ®
Edition 1.0 2012-07
TECHNICAL
REPORT
Fibre optic interconnecting devices and passive components –
Part 04: Example of uncertainty calculation: Measurement of the attenuation
of an optical connector
IEC/TR 62627-04:2012(E)
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IEC/TR 62627-04 ®
Edition 1.0 2012-07
TECHNICAL
REPORT
Fibre optic interconnecting devices and passive components –

Part 04: Example of uncertainty calculation: Measurement of the attenuation

of an optical connector
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
S
ICS 33.180.20 ISBN 978-2-83220-212-8

– 2 – TR 62627-04 © IEC:2012(E)
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Measurement of attenuation . 6
3.1 General . 6
3.2 Attenuation measurement for optical connectors . 7
3.3 Insertion loss measurement using a reference connector . 8
4 Uncertainty estimation . 8
4.1 General . 8
4.2 Uncertainty calculation . 9
4.3 Evaluation of uncertainty . 9
4.4 Combined and expanded uncertainty . 12
Annex A (informative) Uncertainty of measurements . 14
Annex B (informative) The uncertainty budget for attenuation measurements. 17
Bibliography . 21

Figure 1 – Schematic representation of an attenuation measurement . 7
Figure 2 – Measurement of P . 7
in
Figure 3 – Measurement of P . 8
out
Table 1 – Evaluation of the uncertainty contribution due to the power meter for the
measurement of the attenuation of an optical connection . 10
Table 2 – Evaluation of uncertainty contribution due to the light source for the
measurement of the attenuation of an optical connection . 11
Table 3 – Evaluation of uncertainty contribution due to the device under test for the
measurement of the attenuation of an optical connector against reference connector
(u included) . 11
ref
Table 4 – Evaluation of uncertainty contribution due to the device under test for the
measurement of the attenuation of an optical connection (u excluded) . 12
ref
Table 5 – Evaluation of uncertainty contribution for the measurement of the attenuation
of an optical connector against reference connector (u included in u ) . 12
ref DUT
Table 6 – Evaluation of uncertainty contribution for the measurement of the attenuation
of an optical connection (u excluded in u ). 13
ref DUT
Table 7 – Expanded combined uncertainty . 13

TR 62627-04 © IEC:2012(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC INTERCONNECTING DEVICES
AND PASSIVE COMPONENTS –
Part 04: Example of uncertainty calculation:
Measurement of the attenuation of an optical connector

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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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 62627-04, which is a technical report, has been prepared by subcommittee 86B: Fibre
optic interconnecting devices and passive components, of IEC technical committee 86: Fibre
optics.
– 4 – TR 62627-04 © IEC:2012(E)
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
86B/3374/DTR 86B/3427/RVC
Full information on the voting for the approval of this technical report 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 the parts in the IEC 62627 series, published under the general title Fibre optic
interconnecting devices and passive components 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 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.
A bilingual version of this publication may be issued at a later date.

TR 62627-04 © IEC:2012(E) – 5 –
INTRODUCTION
The IEC 61300-3 series is a library of measurement methods for fibre optic passive
components.
These standards describe the necessary equipment and procedures to measure a specific
quantity. The uncertainty budget of every measurement is a key parameter, which should be
determined by applying dedicated statistical methods as extensively presented in reference
documents like ISO/IEC Guide 98-3:2008.
This technical report shows a possible simple application of these methods for the
determination of the measurement uncertainty of optical low loss connector attenuation
measurements as defined in IEC 61300-3-4. A detailed analysis of the main uncertainty
contributions for single and for repeated measurements is shown, and a full mathematical
development of the uncertainty budget is given in Annex B. The difference in uncertainty
estimation for the measurement of an optical connection compared to the measurement of an
optical connector against a reference connector is also discussed.
The reference document for general uncertainty calculations is ISO/IEC Guide 98-3:2008 and
this report does not intend to replace it, it only represents an example and should be used in
combination with ISO/IEC Guide 98-3:2008. A brief introduction to the determination of a
measurement uncertainty according to ISO/IEC Guide 98-3:2008is given in Annex A.
Uncertainty calculations should preferably be performed using a linear representation of the
relevant quantities. In this document all calculations are performed using linear scales but
results are also presented in logarithmic scale, since logarithmic units such as dB or dBm are
in common use in fibre optics. This analysis assumes uncorrelated quantities, which is usually
an acceptable assumption when considering simple attenuation measurements.
All numbers presented in this document are related to this particular example and should not
be taken as standard values.
– 6 – TR 62627-04 © IEC:2012(E)
FIBRE OPTIC INTERCONNECTING DEVICES
AND PASSIVE COMPONENTS –
Part 04: Example of uncertainty calculation:
Measurement of the attenuation of an optical connector

1 Scope
This Technical Report represents a selected example that concerns the measurement of the
attenuation of passive optical components (IEC 61300-3-4), particularly focussed on insertion
method B for low-loss optical connectors assembled on SM optical fibre (according to
IEC 60793-2-50, Type B1.3).
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 60793-2-50, Optical fibres – Part 2-50: Product specifications – Sectional specification for
class B single-mode 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 61755-1, Fibre optic connector optical interfaces – Part 1: Optical interfaces for single
mode non-dispersion shifted fibres – General and guidance
IEC 61755-3-9, Fibre optic interconnecting devices and passive components – Fibre optic
connector optical interfaces – Part 3-9: Optical interface, 2,5 mm and 1,25 mm diameter
cylindrical PC ferrule for reference connector, single mode fibre
IEC 61755-3-10, Fibre optic interconnecting devices and passive components – Fibre optic
connector optical interfaces – Part 3-10: Optical interface, 2,5 mm and 1,25 mm diameter
cylindrical APC ferrule for reference connector, single mode fibre
ISO/IEC Guide 98-3:2008, Uncertainty of measurement- Part 3 Guide to the expression of
uncertainty in measurement (GUM)
3 Measurement of attenuation
3.1 General
Attenuation measurement is intended to give a value for the decrease of useful power,
expressed in decibels, resulting from the insertion of a device under test (DUT), within a
length of optical fibre cable as shown in Figure 1.

TR 62627-04 © IEC:2012(E) – 7 –
 
P
out
P (W) P (W)  
in out A[dB]=−10⋅ log
 
DUT P
in
 
IEC  1274/12
where
P and P are expressed in W
in out
attenuation, A, is expressed in dB
Figure 1 – Schematic representation of an attenuation measurement
3.2 Attenuation measurement for optical connectors
The most common method used for the attenuation measurement of optical connectors is
defined in IEC 61300-3-4 as “insertion method B”. This technical report concentrates on the
uncertainty estimation for this particular method.
Insertion method B is based on the use of an input connector (measurement plug) for the
measurement of P (reference power).
in
Light source (S) and power meter (D) properties shall be as defined in IEC 61300-3-4. For the
scope of this document, the source shall be of type S4 or S5 (single mode source at 1 310 nm
or 1 550 nm)
S D
C
IEC  1275/12
Key
S light source
D detector
C measurement plug
Figure 2 – Measurement of P
in
A DUT connector (C ), assembled on a patchcord, is then connected to C , with the second
connector C placed in front of the detector (see Figure 2 and Figure 3). Any change in the

measured power can be attributed to the additional connection between C and C under the

1 2
assumptions that:
The attenuation caused by the additional fibre length of the patchcord is negligible.
as for P measurements.
The situation at the plug – detector interface is the same for P
in out
– 8 – TR 62627-04 © IEC:2012(E)
S D
C C C
1 2 3
IEC  1276/12
Key
S light source
D detector
C measurement plug
C plug connected to C1
C second connector
Figure 3 – Measurement of P
out
Based on the above assumptions, the connection (C – C ) attenuation (also called Insertion
1 2
Loss) can be calculated as follows:
/ P ) for power measurement values expressed in W (1a)
A[dB] = - 10 log (P
out W in W
A[dB] = P - P for power measurement values expressed in dBm (1b)

in out
3.3 Insertion loss measurement using a reference connector
Although the attenuation measurement is the measurement of the additional loss caused by
the insertion of an optical connection in the line, and therefore comprises of 2 optical
connector plugs and one adapter, it is common use in the industry to use this type of
measurement to verify the quality of one single optical connector by performing attenuation
measurement using reference connectors and adapters.
Reference connectors and adaptors are components with tightened tolerances and give more
reproducible results when the same connector is measured in different laboratories using
different reference connectors and adapters. These types of components are currently in the
process of standardization (IEC 61755-3-9 and IEC 61755-3-10).
4 Uncertainty estimation
4.1 General
The relative uncertainty of the attenuation A is derived from the uncertainty of the reference
power P and of P measurements and by considering supplementary contributions, which

in out
will be discussed in the next clauses.
In addition, we shall consider following two situations:
a) The attenuation measurement of a connection (C – C ).
1 2
b) The attenuation measurement of one connector (C ) using a reference connector plug (C ).
2 1
In this case, the attenuation value is attributed to C and measurement may vary when
changing reference connector and or adaptor, thus representing one additional source of
uncertainty.
TR 62627-04 © IEC:2012(E) – 9 –
4.2 Uncertainty calculation
For the calculation of the uncertainty of attenuation measurement according to IEC 61300-3-4,
method B, the following equation is valid (for details of the calculation, see Annex B and more
particularly Formula (B.1b)):
2 2 2 2 2 2 2 2 2
(2)
u ≈ 2⋅u + 2⋅u + 2⋅u + u + u + 2⋅u + 2⋅u + u + u
A TypeA PDR Displ Lin Unif P PDL mating ref
stab
where
u is the type A relative uncertainty in case of repeated measurements of optical power,
TypeA
or is given by the relative repeatability∆P of the power meter in case of a single
rep
measurement, namely u =∆P / 3
TypeA rep
;
is the relative uncertainty arising from the stability of the optical source;
u
Pstab
u is the relative uncertainty arising from the polarization dependency of the
PDR
responsivity of the power meter;
u is the relative uncertainty arising from the polarization dependant losses of the fibre
PDL
and of the connector;
is the relative uncertainty arising from the finite display resolution of the power
u
Displ
meter;
is the relative uncertainty arising from the non-linearity of the power meter;
u
Lin
u is the relative uncertainty arising from the uniformity of the power meter and from
Unif
possible reflection effects between the detector and the ferrule;
u is the uncertainty due to the use of different reference connectors. This contribution
ref
is only relevant when measuring the attenuation of a single connector by comparison
with a reference connector;
is the relative uncertainty related to the repeatability of the connector matin
...