IEC 61300-3-7:2021

IEC 61300-3-7 ®
Edition 3.1 2025-12
INTERNATIONAL
STANDARD
CONSOLIDATED VERSION
Fibre optic interconnecting devices and passive components - Basic test and
measurement procedures -
Part 3-7: Examinations and measurements - Wavelength dependence of
attenuation and return loss of single mode components
ICS 33.180.20  ISBN 978-2-8327-0947-4

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CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, abbreviated terms and quantity symbols . 6
3.1 Terms and definitions. 6
3.2 Abbreviated terms . 6
3.3 Quantity symbols . 8
4 General description . 8
4.1 General . 8
4.2 Light source and detector conditions . 8
4.3 General explanation of attenuation and return loss . 9
4.3.1 Attenuation . 9
4.3.2 Return loss . 9
4.4 Device under test (DUT) . 10
4.5 Measurement methods . 10
5 Apparatus . 11
5.1 General . 11
5.2 Optical source . 12
5.2.1 Method A – Broadband light source (BBS) . 12
5.2.2 Method B – Tuneable narrowband light source (TNLS) . 12
5.2.3 Method C – Set of multiple fixed narrowband light sources (NLS) . 12
5.3 Depolarizer . 12
5.4 Power detection systems . 13
5.4.1 Method A – Tuneable narrowband detection (TND) . 13
5.4.2 Method B and C – Broadband detection (BBD) . 13
5.5 Branching device (BD) . 14
5.6 Termination. 14
5.7 Temporary joint (TJ) . 14
5.8 Test patch cord . 15
5.9 Reference plugs (RP) . 15
5.10 Reference adapters (RA) . 15
6 Procedure . 15
6.1 Method A – Broadband light source . 15
6.1.1 Method A1 – Attenuation only . 15
6.1.2 Method A2 – Attenuation and return loss . 16
6.2 Method B – Tuneable narrowband light source . 20
6.2.1 General . 20
6.2.2 Method B – Attenuation only . 21
6.2.3 Method B – Attenuation and return loss . 21
6.3 Method C – Set of multiple fixed narrowband light sources . 22
6.3.1 General . 22
6.3.2 Method C1 – Attenuation only . 22
6.3.3 Method C2 – Attenuation and return loss . 22
7 Test results . 23
8 Details to be reported . 24
8.1 General . 24
8.2 Total measurement system . 24
8.3 Source . 24
8.3.1 Broadband light source . 24
8.3.2 Tuneable or discrete narrowband light source . 24
8.3.3 Depolarizer . 24
8.4 Detection system . 24
8.4.1 Optical power meter . 24
8.4.2 Optical spectrum analyzer . 25
8.4.3 Branching device . 25
8.4.4 Termination . 25
8.4.5 Temporary joint . 25
8.4.6 Reference plug . 25
8.4.7 Reference adapter . 25
Annex A (informative) Types of passive optical components . 26
Annex B (informative) Typical light source characteristics . 27
B.1 General . 27
B.2 Broadband light source . 27
B.3 Tuneable laser source . 27
Annex C (informative) Terminations . 29
Bibliography . 31

Figure 1 – Generic explanation of attenuation and return loss . 9
Figure 2 – Method A1, attenuation-only, reference measurement set-up . 16
Figure 3 – Method A1, attenuation-only, DUT measurement set-up . 16
Figure 4 – Method A2, attenuation and return loss, reference branching device
measurement set-up . 17
Figure 5 – Method A2, attenuation and return loss, reference measurement set-up . 18
Figure 6 – Method A2, system background measurement set-up . 19
Figure 7 – Method A2, attenuation and return loss, DUT measurement set-up . 20
Figure 8 – Method B, tuneable narrowband light source with and without depolarizer . 21
Figure 9 – Method C, multiple fixed narrowband sources set-up. 22
Figure 10 – Example wavelength dependent attenuation plot . 23

Table 1 – Device under test categories . 10
Table 2 – Measurement methods . 11
Table 3 – Reference test methods . 11
Table 4 – Preferred OPM parameters. 14
Table 5 – Steps of method A1, attenuation only . 15
Table 6 – Steps of method A2, attenuation and return loss . 16
Table 7 – Steps of method B, attenuation only . 21
Table 8 – Steps of method B, attenuation and return loss . 21
Table 9 – Steps of method C, attenuation only . 22
Table 10 – Steps of method C2, attenuation and return loss . 23
Table 11 – Example report for wavelength dependent attenuation and return loss . 23
Table A.1 – Functional summary of common passive optical components . 26
Table B.1 – Types of broadband light source (BBS) and main characteristics . 27
Table B.2 – Types of tuneable light source (TLS) and main characteristics . 28
Table C.1 – Impact on termination values on measured return loss . 29
Table C.2 – Impact on termination values on measured return loss uncertainty . 30

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Fibre optic interconnecting devices and passive components -
Basic test and measurement procedures -
Part 3-7: Examinations and measurements - Wavelength dependence of
attenuation and return loss of single mode components

FOREWORD
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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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
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shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been prepared
for user convenience.
IEC 61300-3-7 edition 3.1 contains the third edition (2021-07) [documents 86B/4337/CDV and
86B/4425A/RVC] and its amendment 1 (2025-12) [documents 86B/4939/CDV and
86B/4978/RVC].
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions are in green text, deletions are in strikethrough red text.
A separate Final version with all changes accepted is available in this publication.

IEC 61300-3-7 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 third edition cancels and replaces the second edition published in 2009. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) reduction of the number of alternative methods proposed to bring in-line with industry
practice;
b) re-statement of the equations for insertion loss and return loss using logarithmic forms more
common in the industry;
c) additional recommendations with respect to the creation of fibre terminations;
d) additional discussion on the characterization of the optical sources used in this document;
e) simplification of bi-directional testing;
f) removal of separate return loss only measurement procedures.
The text of this International Standard is based on the following documents:
Draft Report on voting
86B/4337/CDV 86B/4425A/RVC
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.
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/standardsdev/publications.
A list of all parts in the IEC 61300 series, published under the general title Fibre optic
interconnecting devices and passive components – Basic test and measurement procedures,
can be found on the IEC website.
The committee has decided that the contents of this document and its amendment 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 IEC 61300-3 describes methods available to measure the wavelength dependence
of attenuation and return loss of two-port, single mode passive optical components. It is not,
however, applicable to dense wavelength division multiplexing (DWDM) devices. Measurement
methods of wavelength dependence of attenuation of DWDM devices are described in
IEC 61300-3-29.
There are two measurement cases described in this document:
a) measurement of attenuation only;
b) measurement of attenuation and return loss at the same time.
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 60050-731, International Electrotechnical Vocabulary (IEV) – Part 731: Optical fibre
communication (available at www.electropedia.org)
IEC 60793-2-50, Optical fibres – Part 2-50: Product specifications – Sectional specification for
class B single-mode fibres
IEC 61755-2-4, Fibre optic interconnecting devices and passive components – Connector
optical interfaces – Part 2-4: Connection parameters of non-dispersion shifted single-mode
physically contacting fibres – Non-angled for reference connection applications
IEC 61755-2-5, Fibre optic interconnecting devices and passive components – Connector
optical interfaces – Part 2-5: Connection parameters of non-dispersion shifted single-mode
physically contacting fibres – Angled for reference connection applications
IEC TR 61931, Fibre optic – Terminology
IEC 62074-1, Fibre optic interconnecting devices and passive components – Fibre optic WDM
devices – Part 1: Generic specification
3 Terms, definitions, abbreviated terms and quantity symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-731, IEC TR
61931 and IEC 62074-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp.
3.2 Abbreviated terms
APC angled physical contact
ASE amplified spontaneous emission
BBD broadband detector
BBS  broadband light source
BD  branching device
BPON broadband passive optical network
CC  coherent control
CWDM coarse wavelength division multiplexing
DFB distributed feedback
DOP degree of polarization
DUT device under test
DWDM dense wavelength division multiplexing
ECL  external cavity laser
EDFA erbium doped fibre amplifier
EDFL erbium doped fibre laser
EPON ethernet passive optical network
FBG fibre Bragg grating
FEC forward error correction
FP  Fabry-Perot
GPON gigabit Ethernet passive optical network
IR  infra-red
LD  laser diode
LED light emitting diode
NLS narrow band light source
OADM optical add drop multiplexer
OFA optical fibre amplifier
OPM optical power meter
OSA optical spectrum analyzer
PDL  polarization dependent loss
PON  passive optical network
RA  reference adapter
RBD reference branching device
RBW resolution bandwidth
RL  return loss
RP  reference plug
RTM reference test method
SLED super light emitting diode
SMSR side mode suppression ratio
SOP state of polarization
SSE source spontaneous emission
TJ  temporary joint
TLS tuneable laser source
TND tuneable narrow band detection
TNLS tuneable narrow band light source
UV  ultra violet
WDM wave division multiplexing
3.3 Quantity symbols
λ array of n (k = 1 to n) wavelengths to be measured, expressed in nm
k
th
P (λ ) input optical power to the device under test (DUT) of the k wavelength to be
i k
measured, expressed in dBm
th
P (λ ) output optical power from the output port of the DUT of the k wavelength to be
t k
measured, expressed in dBm
P (λ ) output optical power at the input port of the DUT propagating away from the input
r k
th
port of the k wavelength to be measured, expressed in dBm
P ′(λ ) output optical power at the branching port of the reference branching device (RBD)
r k
th
propagating away from the input port of the RBD of the k wavelength to be
measured, expressed in dBm
th
A(λ ) attenuation of the DUT at k wavelength, expressed in dB
k
th
RL(λ ) return loss of the DUT at k wavelength, expressed in dB
k
th
RL*(λ ) calculated return loss of the DUT at k wavelength corrected for measurement
k
apparatus RL, expressed in dB
th
RL (λ ) return loss of the measurement apparatus at k wavelength, expressed in dB
0 k
4 General description
4.1 General
Attenuation, A(λ ), is the relative decrease of transmitted optical power due to the insertion or
k
addition of a component within a fibre-optic system. Return loss, RL(λ ), is the relative optical
k
power reflected from a component inserted within a fibre-optic system. A(λ ) and RL(λ ) are
k k
expressed in decibels (dB) and are obtained by comparing the optical power incident on the
DUT with the optical powers transmitted or reflected at the ports of the DUT. These terms are
defined in IEC TR 61931.
4.2 Light source and detector conditions
A(λ ) and RL(λ ) are measured over a wavelength range defined by the DUT specifications. The
k k
spectral properties of the measurement system should be selected for the measurement of the
attenuation performance specification of the DUT. These properties should include:
• wavelength setting resolution (wavelength difference between two adjacent data points);
• wavelength setting uncertainty;
• 3 dB spectral bandwidth of the light source or the tuneable narrowband detector (TND);
• source spontaneous emission (SSE) noise floor relative to peak power for the light source;
• degree of polarization (DOP).
The following performance guidelines shall be followed.
– The wavelength setting resolution shall be less than half the smallest resolvable attenuation
feature. For example, when the attenuation changes over 1 nm the wavelength resolution
shall be less than 0,5 nm.
– The 3 dB spectral bandwidth for the light source or the TND shall be less than half the
wavelength resolution of the measurement.
– When the DOP of the source is more than 5 %, the polarization dependence of the detection
system shall be considered as part of the total insertion loss uncertainty.
The impact of the source SSE noise floor on the uncertainty of the measurement depends
strongly on the wavelength dependence of the DUT. For CWDM components, this shall be
considered. The total ASE power over the measurement range limits the dynamic range of the
measurement.
Additional information can be found in Annex B.
4.3 General explanation of attenuation and return loss
4.3.1 Attenuation
Attenuation, A(λ ), is the relative optical power reduction caused by the insertion of the DUT
k
into an optical path and is illustrated in Figure 1. It is a function of wavelength. It is expressed
as shown in Formula (1):
A λ Pλ−P λ dB)
( ) ( ) ( ) (1)
k itkk
where
(λ ) is the optical power, as a function of wavelength, incident on and measured at the input
P
i k
port of the DUT, expressed in dBm;
P (λ ) is the optical power, as a function of wavelength, transmitted through and measured at
t k
the output port of the DUT, expressed in dBm.
4.3.2 Return loss
Return loss, RL(λ ) is the optical power reflected by the DUT relative to the incident power. It is
k
a function of wavelength and is illustrated in Figure 1. It is expressed as shown in Formula (2):
RL λ Pλ−P λ  (dB)
( ) ( ) ( ) (2)
kkkir
where
P (λ ) is the optical power, as a function of wavelength, incident on and measured at the input
i k
port of the DUT, expressed in dBm;
(λ ) is the optical power, as a function of wavelength, reflected by and measured from the
P
r k
input port of the DUT, expressed in dBm.

Figure 1 – Generic explanation of attenuation and return loss
=
=
4.4 Device under test (DUT)
The DUT may have more than two ports. Only two ports are relevant for attenuation testing
(input and output port) and only one is relevant for return loss testing (input port). It is not a
requirement to measure attenuation and return loss at the same time.
Eight two-port DUT configurations are described in Table 1. Port connections may consist of
bare fibre, connector plug, or receptacle. IEC 61300-3-4 describes multiple connection methods
in detail. This document focuses on type 4 and type 7. If a multiport DUT is to be measured,
all unused ports shall be terminated. For additional details, refer to Annex C.
A summary of the applicable DUT can be found in Annex A.
Table 1 – Device under test categories
Type Description DUT
Fibre to fibre
(component)
Fibre to fibre
2 (splice or field-mountable connector
set)
3 Fibre to plug
Plug to plug
(component)
Plug to plug
(patchcord)
Single plug
(pigtail)
Receptacle to receptacle
(component)
Receptacle to plug
(component)
Key
C: optical component
NOTE Type 1 can be measured using a temporary joint replacing optical
connectors.
4.5 Measurement methods
The following measurement configurations are defined in Table 2. The applicable reference test
method (RTM) is shown in Table 3.
Table 2 – Measurement methods
Detection
Method Name Light source Example
system
A Broadband light source BBS TND BBS + DUT + OSA
Tuneable narrow band light
B TNLS BBD TLS + DUT + OPM
source
Set of multiple fixed narrow
C NLS BBD N x DFB-LD + DUT + OPM
band light sources
Table 3 – Reference test methods
Resolution bandwidth Wavelength band RTM Alternative
(RBW)
< 0,1 nm Any Method B Method A
≥ 0,1 nm C-band and L-band Method B Method A, method C
≥ 0,1 nm Not C-band and L-band Method A Method B, method C

a) Method A – Broadband light source (BBS)
In method A, a broadband light source (BBS) is used with a tuneable narrowband detector
(TND). A common implementation is to use an optical spectrum analyzer (OSA) for the TND.
In this implementation, the OSA controls the wavelength range, the measurement
wavelength and resolution bandwidth. The optical power and bandwidth of the BBS shall be
large enough to cover the attenuation of the DUT and the power measurement dynamic
range of the OSA.
b) Method B – Tuneable narrowband light source (TNLS)
In method B, a tuneable narrowband light source (TNLS) is used with a broadband detection
system (BBD). The most likely implementation of method B is the use of a tuneable laser
source (TLS) with an optical power meter (OPM). In this method, the TLS controls the
wavelength range, the measurement wavelength and resolution bandwidth. Given the
narrow linewidth and high DOP, care shall be taken to minimize the test system background
return loss. This will help to avoid coherent interference in the power measurement.
c) Method C – Set of multiple fixed narrowband light sources (NLS)
In method C, a set of narrowband light sources are used with a broadband detector (BBD).
This method is suitable for a DUT which has a small wavelength dependent loss and is
specified for operation over a wide wavelength range. A common implementation of
method C is the use of a set of fixed laser sources with an N x 1 optical branching device or
optical switch. The use of a switch prevents the need to turn off the light sources not in use.
This can reduce the time needed for laser power stabilization. An OPM is typically used as
the BBD.
5 Apparatus
5.1 General
All methods share a common basic setup:
• optical source;
• source depolarizer (optional);
• return path branching device (for RL measurement);
• temporary joint (TJ);
• fibre;
• reference plug (RP);
• reference adapter (RA);
• termination (for RL measurement);
• power detection system.
5.2 Optical source
5.2.1 Method A – Broadband light source (BBS)
A BBS is used for the source in method A. The BBS emits light over a continuous wavelength
range with various characteristics depending on its type. Examples of a BBS are a white light
source (i.e. tungsten lamp), a light emitting diode (LED), a super-luminescent LED (SLED) or
an optical fibre amplifier (OFA) without an input optical signal.
The wavelength range shall be wide enough to cover the entire specified DUT wavelength
operating range. The output power shall be high enough for A(λ ) and RL(λ ) to be measured.
k k
The spectral power density instability shall be smaller than ±0,05 dB as observed for at least
30 min.
5.2.2 Method B – Tuneable narrowband light source (TNLS)
A TNLS emits a narrow spectrum of light that can be spectrally tuned over the specified
wavelength range. There are various characteristics depending on its type. Examples of
applicable TNLS technologies are a BBS with a tuneable filter, an external cavity tuneable laser,
a tuneable DFB laser diode and a tuneable erbium-doped fibre laser. The wavelength accuracy
and spectral bandwidth shall be specified. Typical values are provided in Annex B.
5.2.3 Method C – Set of multiple fixed narrowband light sources (NLS)
Method C is based on a set of N discrete wavelengths. The wavelengths may be emitted by
sources such as a Fabry-Perot (FP) laser diode (LD) or distributed feedback (DFB) LD.
The set of NLS shall cover the specified wavelength range to be measured. When using a N × 1
fibre optic branching device or fibre optic switch, N is shall be equal to or more than the number
of wavelengths to be measured and the set of NLS used. Other ports to be measured shall be
terminated.
When a TLS is used as the NLS, the requirement for a TLS is same as that for a NLS.
5.3 Depolarizer
The measurement results [A(λ ) and RL(λ )] shall be averaged as a function of the state of
k k
polarization (SOP). Sources based on lasers will be highly polarized (DOP is nearly equal to
100 %) while sources like LED and BBS will be highly depolarized (DOP is less than 5 %). For
sources with high DOP, a depolarizer will be required. The depolarizer shall reduce the DOP to
< 5 %.
There are two approaches for obtaining the polarization averaged value of A(λ ) and RL(λ ).
k k
• Direct approach: A depolarizer based on an active or passive device is connected at the
output port of the source in order to reduce its DOP. This allows direct measurement of the
averaged A(λ ) and RL(λ ). The averaging time of the power detection system shall be
k k
greater than 2 times the quoted de-polarization time.
• Indirect approach: Measure A(λ ) and RL(λ ) as a function of the state of polarization (SOP)
k k
to obtain the average value of A(λ ) and RL(λ ) from the measurement results. This requires
k k
multiple measurements be made and recorded. In this case, the role of the depolarizer is
fulfilled by a polarization controller that either deterministically sets a chosen sequence of
SOP or randomly scans many SOP.
5.4 Power detection systems
5.4.1 Method A – Tuneable narrowband detection (TND)
The measurement system shall be stable within specified limits over the measuring time. For
measurements where the connection to the detector shall be separated between measurements,
the repeatability specification shall be less than 0,02 dB.
The TND (typically an OSA) measures the output optical power at a specified wavelength over
the wavelength range. Generally, an OSA has an optical filter function inside. The resolution
bandwidth (RBW) is typically specified at –3 dB or the full width at half the maximum. The RBW
shall be specified in accordance with the wavelength setting interval. In order to avoid false
interpretation of artefacts in the measurement, the optical rejection ratio shall be specified. An
example of such specification could be –20 dB at 0,1 nm away from the centre wavelength. If
a detailed assessment of the OSA RBW is required, the filter shape of the OSA should be
measured. This is typically achieved by measuring the envelope of a DFB known to have a
spectrum much narrower than the OSA RBW.
The power measurement range and sensitivity shall be high enough for A(λ ) and RL(λ ) to be
k k
measured in accordance with the DUT specification. The amplitude uncertainty due to
polarization dependence of the OSA shall be less than the desired uncertainty to be measured.
5.4.2 Method B and C – Broadband detection (BBD)
The broadband detection system (BBD) measures an integrated optical power over a wide
range. A typical BBD consists of an optical power sensor, a mechanism for coupling a fibre to
it and associated detection electronics. These devices are most commonly referred to as an
OPM.
The performance of the measurement system shall be stable within specified limits over the
measuring time. For measurements where the connection to the detector shall be separated
between measurements, the repeatability specification shall be less than 0,02 dB. A detector
with a large sensitive area may be used to achieve this.
The power measurement range of the BBD shall cover the peak power of the light source and
intended attenuation of the DUT. The minimum detectable power is recommended to be more
than 10 dB smaller than the optical power to be measured. The amplitude uncertainty due to
polarization dependence of the OPM shall be less than the desired uncertainty to be measured.
The preferred OPM parameters are given in Table 4.
Table 4 – Preferred OPM parameters
Type Maximum nonlinearity Relative uncertainty
dB dB
±0,01
(attenuation ≤ 10 dB)
Single mode ≤ 0,02
±0,05
(10 dB < attenuation ≤ 60 dB)
In order to ensure that all light exiting the fibre is detected by the OPM, the sensitive area of the detector and the
relative position between it and the fibre should be compatible with the numerical aperture of the fibre.
NOTE Common sources of relative uncertainty are polarization dependence and interference with reflections from
the OPM and fibre connector surfaces. The sensitivity of the power meter to such reflections can be characterized
by the parameter spectral ripple, determined as the periodic change in responsivity versus the wavelength of a
coherent light source.
5.5 Branching device (BD)
The branching device is used to connect the light source to the DUT. It will split the reflected
light from the DUT to the return loss detection system.
The splitting ratio of the BD shall be stable during the measurement time. The wavelength
dependent loss and return loss of the BD should be smaller than the DUT to be measured. The
uncertainty due to polarization dependence loss of the BD shall be less than the desired
uncertainty of A(λ ) to be measured and in general < 0,05 dB. The return loss should be at least
n
10 dB greater than the maximum RL(λ ) to be measured. The directivity should be at least 10 dB
k
greater than the maximum RL(λ ) to be measured.
k
5.6 Termination
A termination is a device, process or manipulation which induces the maximum attenuation
possible. Terminations shall also have a large return loss. Common terminations are:
a) angled fibre ends such as the use of an angled physical contact (APC) connector or angled
cleave (the angle should be more than 8°);
b) application of a refractive index matching material to the fibre end in air;
c) high return loss achieved with a mandrel wrap (tightly coiling the fibre per the manufacturer’s
recommendation).
The termination return loss shall be 15 dB greater than the maximum RL(λ ) to be measured.
k
Unless otherwise specified, all unused DUT ports (input or outputs) shall be terminated during
the RL measurement.
5.7 Temporary joint (TJ)
This is a method, device, or mechanical fixture for temporarily aligning two fibre ends into a
stable, reproducible, low-loss joint. It is used when direct connection between the DUT and the
measurement system is not achievable by a standard connector. Examples are a precision
V‑groove, vacuum chuck, micromanipulator, fusion splice or mechanical splice. The attenuation
of the temporary joint shall be stable to within 10 % of the required measurement uncertainty in
dB over the time taken to measure P P and P A suitable refractive index matching material
, .
i t r
may be used to improve the stability of the TJ.
5.8 Test patch cord
The test patch cord connects the DUT to the test system using a temporary joint. It shall belong
to the same category of fibre used by the DUT. Fibres shall be in accordance with
IEC 60793‑2‑50.
5.9 Reference plugs (RPs)
Where reference plugs are required to form complete connector assemblies in any of the test
methods, the reference plugs become a part of the DUT during the measurement of attenuation.
RPs shall be specified in the relevant specification. IEC 61755-2-4 for non-angled connector
plugs and IEC 61755-2-5 for angled connector plugs shall be referred to.
5.10 Reference adapters (RAs)
Where reference adapters are required to form complete connector assemblies in any of the
test methods, the reference adapters become a part of the DUT during the measurement of
attenuation. RAs shall be specified in the relevant specification. IEC 61755-2-4 for non-angled
connector plugs and IEC 61755-2-5 for angled connector plugs shall be referred to.
6 Procedure
6.1 Method A – Broadband light source
6.1.1 Method A1 – Attenuation only
6.1.1.1 General
The procedure showed in 6.1.1 shall be used for measuring attenuation and is shown in Table 5.
Generate a wavelength of λ (k = 1 to n), where n indicates the number of wavelengths where

k
optical power is to be measured. The RBW of the TND is set as per the guidance in 5.4.1. The
BBS is energized and allowed to stabilize per the manufacturer’s specification.
Table 5 – Steps of method A1, attenuation only
Step Purpose Result
P (λ )
1 Reference measurement
i k
P (λ )
2 DUT measurement
t k
A(λ )
3 Calculation
k
6.1.1.2 Method A1 – Attenuation-only, reference step 1
Connect the BBS to the TND as shown in Figure 2. The connection may be direct or with an
adapter. Measure and record the optical output power levels P (λ ) for all pre-defined
i k
wavelengths of λ (k = 1 to n).
k
a) Type 4 DUT
b) Type 7 DUT
Figure 2 – Method A1, attenuation-only, reference measurement set-up
6.1.1.3 Method A1 – Attenuation-only, DUT measurement step 2
Insert the DU
...

IEC 61300-3-7 ®
Edition 3.0 2021-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures –
Part 3-7: Examinations and measurements – Wavelength dependence of
attenuation and return loss of single mode components

Dispositifs d’interconnexion et composants passifs fibroniques – Procédures
fondamentales d'essais et de mesures –
Partie 3-7: Examens et mesures – Affaiblissement et affaiblissement de réflexion
des composants unimodaux en fonction de la longueur d’onde

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IEC 61300-3-7 ®
Edition 3.0 2021-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic interconnecting devices and passive components – Basic test and

measurement procedures –
Part 3-7: Examinations and measurements – Wavelength dependence of

attenuation and return loss of single mode components

Dispositifs d’interconnexion et composants passifs fibroniques – Procédures

fondamentales d'essais et de mesures –

Partie 3-7: Examens et mesures – Affaiblissement et affaiblissement de réflexion

des composants unimodaux en fonction de la longueur d’onde

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.20 ISBN 978-2-8322-1052-1

– 2 – IEC 61300-3-7:2021 © IEC 2021
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, abbreviated terms and quantity symbols . 7
3.1 Terms and definitions . 7
3.2 Abbreviated terms . 8
3.3 Quantity symbols . 9
4 General description . 9
4.1 General . 9
4.2 Light source and detector conditions . 9
4.3 General explanation of attenuation and return loss . 10
4.3.1 Attenuation . 10
4.3.2 Return loss . 10
4.4 Device under test (DUT) . 11
4.5 Measurement methods . 12
5 Apparatus . 12
5.1 General . 12
5.2 Optical source . 13
5.2.1 Method A – Broadband light source (BBS) . 13
5.2.2 Method B – Tuneable narrowband light source (TNLS) . 13
5.2.3 Method C – Set of multiple fixed narrowband light sources (NLS) . 13
5.3 Depolarizer . 13
5.4 Power detection systems . 14
5.4.1 Method A – Tuneable narrowband detection (TND) . 14
5.4.2 Method B and C – Broadband detection (BBD) . 14
5.5 Branching device (BD) . 15
5.6 Termination . 15
5.7 Temporary joint (TJ) . 15
5.8 Test patch cord . 15
5.9 Reference plugs (RP). 16
5.10 Reference adapters (RA) . 16
6 Procedure . 16
6.1 Method A – Broadband light source . 16
6.1.1 Method A1 – Attenuation only . 16
6.1.2 Method A2 – Attenuation and return loss . 17
6.2 Method B – Tuneable narrowband light source . 20
6.2.1 General . 20
6.2.2 Method B – Attenuation only . 21
6.2.3 Method B – Attenuation and return loss . 21
6.3 Method C – Set of multiple fixed narrowband light sources . 22
6.3.1 General . 22
6.3.2 Method C1 – Attenuation only . 22
6.3.3 Method C2 – Attenuation and return loss . 22
7 Test results . 23

8 Details to be reported . 24
8.1 General . 24
8.2 Total measurement system . 24
8.3 Source . 24
8.3.1 Broadband light source . 24
8.3.2 Tuneable or discrete narrowband light source . 24
8.3.3 Depolarizer . 24
8.4 Detection system . 24
8.4.1 Optical power meter. 24
8.4.2 Optical spectrum analyzer . 25
8.4.3 Branching device . 25
8.4.4 Termination . 25
8.4.5 Temporary joint . 25
8.4.6 Reference plug . 25
8.4.7 Reference adapter . 25
Annex A (informative) Types of passive optical components . 26
Annex B (informative) Typical light source characteristics . 27
B.1 General . 27
B.2 Broadband light source . 27
B.3 Tuneable laser source . 27
Annex C (informative) Terminations . 29
Bibliography . 31

Figure 1 – Generic explanation of attenuation and return loss . 11
Figure 2 – Method A1, attenuation-only, reference measurement set-up . 16
Figure 3 – Method A1, attenuation-only, DUT measurement set-up . 17
Figure 4 – Method A2, attenuation and return loss, reference branching device
measurement set-up . 18
Figure 5 – Method A2, attenuation and return loss, reference measurement set-up. 18
Figure 6 – Method A2, system background measurement set-up . 19
Figure 7 – Method A2, attenuation and return loss, DUT measurement set-up . 20
Figure 8 – Method B, tuneable narrowband light source with and without depolarizer . 21
Figure 9 – Method C, multiple fixed narrowband sources set-up . 22
Figure 10 – Example wavelength dependent attenuation plot . 23

Table 1 – Device under test categories . 11
Table 2 – Measurement methods . 12
Table 3 – Reference test methods . 12
Table 4 – Preferred OPM parameters . 15
Table 5 – Steps of method A1, attenuation only . 16
Table 6 – Steps of method A2, attenuation and return loss . 17
Table 7 – Steps of method B, attenuation only . 21
Table 8 – Steps of method B, attenuation and return loss . 21
Table 9 – Steps of method C, attenuation only . 22
Table 10 – Steps of method C2, attenuation and return loss . 23

– 4 – IEC 61300-3-7:2021 © IEC 2021
Table 11 – Example report for wavelength dependent attenuation and return loss . 23
Table A.1 – Functional summary of common passive optical components . 26
Table B.1 – Types of broadband light source (BBS) and main characteristics . 27
Table B.2 – Types of tuneable light source (TLS) and main characteristics . 28
Table C.1 – Impact on termination values on measured return loss . 29
Table C.2 – Impact on termination values on measured return loss uncertainty . 30

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC INTERCONNECTING DEVICES
AND PASSIVE COMPONENTS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 3-7: Examinations and measurements – Wavelength dependence
of attenuation and return loss of single mode components

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
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 61300-3-7 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 third edition cancels and replaces the second edition published in 2009. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) reduction of the number of alternative methods proposed to bring in-line with industry
practice;
b) re-statement of the equations for insertion loss and return loss using logarithmic forms more
common in the industry;
c) additional recommendations with respect to the creation of fibre terminations;

– 6 – IEC 61300-3-7:2021 © IEC 2021
d) additional discussion on the characterization of the optical sources used in this document;
e) simplification of bi-directional testing;
f) removal of separate return loss only measurement procedures.
The text of this International Standard is based on the following documents:
Draft Report on voting
86B/4337/CDV 86B/4425A/RVC
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.
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/standardsdev/publications.
A list of all parts in the IEC 61300 series, published under the general title Fibre optic
interconnecting devices and passive components – Basic test and measurement procedures,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
FIBRE OPTIC INTERCONNECTING DEVICES
AND PASSIVE COMPONENTS –
BASIC TEST AND MEASUREMENT PROCEDURES –

Part 3-7: Examinations and measurements – Wavelength dependence
of attenuation and return loss of single mode components

1 Scope
This part of IEC 61300-3 describes methods available to measure the wavelength dependence
of attenuation and return loss of two-port, single mode passive optical components. It is not,
however, applicable to dense wavelength division multiplexing (DWDM) devices. Measurement
methods of wavelength dependence of attenuation of DWDM devices are described in
IEC 61300-3-29.
There are two measurement cases described in this document:
a) measurement of attenuation only;
b) measurement of attenuation and return loss at the same time.
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 60050-731, International Electrotechnical Vocabulary (IEV) – Part 731: Optical fibre
communication (available at www.electropedia.org)
IEC 60793-2-50, Optical fibres – Part 2-50: Product specifications – Sectional specification for
class B single-mode fibres
IEC 61755-2-4, Fibre optic interconnecting devices and passive components – Connector
optical interfaces – Part 2-4: Connection parameters of non-dispersion shifted single-mode
physically contacting fibres – Non-angled for reference connection applications
IEC 61755-2-5, Fibre optic interconnecting devices and passive components – Connector
optical interfaces – Part 2-5: Connection parameters of non-dispersion shifted single-mode
physically contacting fibres – Angled for reference connection applications
IEC TR 61931, Fibre optic – Terminology
IEC 62074-1, Fibre optic interconnecting devices and passive components – Fibre optic WDM
devices – Part 1: Generic specification
3 Terms, definitions, abbreviated terms and quantity symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-731, IEC TR
61931 and IEC 62074-1 apply.
– 8 – IEC 61300-3-7:2021 © IEC 2021
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp.
3.2 Abbreviated terms
APC angled physical contact
ASE amplified spontaneous emission
BBD broadband detector
BBS  broadband light source
BD  branching device
BPON broadband passive optical network
CC  coherent control
CWDM coarse wavelength division multiplexing
DFB distributed feedback
DOP degree of polarization
DUT device under test
DWDM dense wavelength division multiplexing
ECL  external cavity laser
EDFA erbium doped fibre amplifier
EDFL erbium doped fibre laser
EPON ethernet passive optical network
FBG fibre Bragg grating
FEC forward error correction
FP  Fabry-Perot
GPON gigabit Ethernet passive optical network
IR  infra-red
LD  laser diode
LED light emitting diode
NLS narrow band light source
OADM optical add drop multiplexer
OFA optical fibre amplifier
OPM optical power meter
OSA optical spectrum analyzer
PDL  polarization dependent loss
PON  passive optical network
RA  reference adapter
RBD reference branching device
RBW resolution bandwidth
RL  return loss
RP  reference plug
RTM reference test method
SLED super light emitting diode
SMSR side mode suppression ratio

SOP state of polarization
SSE source spontaneous emission
TJ  temporary joint
TLS tuneable laser source
TND tuneable narrow band detection
TNLS tuneable narrow band light source
UV  ultra violet
WDM wave division multiplexing
3.3 Quantity symbols
array of n (k = 1 to n) wavelengths to be measured, expressed in nm
λ
k
th
P (λ ) input optical power to the device under test (DUT) of the k wavelength to be
i k
measured, expressed in dBm
th
P (λ ) output optical power from the output port of the DUT of the k wavelength to be
t k
measured, expressed in dBm
P (λ ) output optical power at the input port of the DUT propagating away from the input
r k
th
port of the k wavelength to be measured, expressed in dBm
P ′(λ ) output optical power at the branching port of the reference branching device (RBD)
r k
th
propagating away from the input port of the RBD of the k wavelength to be
measured, expressed in dBm
th
A(λ ) attenuation of the DUT at k wavelength, expressed in dB
k
th
RL(λ ) return loss of the DUT at k wavelength, expressed in dB
k
th
RL*(λ ) calculated return loss of the DUT at k wavelength corrected for measurement
k
apparatus RL, expressed in dB
th
(λ ) return loss of the measurement apparatus at k wavelength, expressed in dB
RL
0 k
4 General description
4.1 General
Attenuation, A(λ ), is the relative decrease of transmitted optical power due to the insertion or
k
addition of a component within a fibre-optic system. Return loss, RL(λ ), is the relative optical
k
power reflected from a component inserted within a fibre-optic system. A(λ ) and RL(λ ) are
k k
expressed in decibels (dB) and are obtained by comparing the optical power incident on the
DUT with the optical powers transmitted or reflected at the ports of the DUT. These terms are
defined in IEC TR 61931.
4.2 Light source and detector conditions
A(λ ) and RL(λ ) are measured over a wavelength range defined by the DUT specifications. The
k k
spectral properties of the measurement system should be selected for the measurement of the
attenuation performance specification of the DUT. These properties should include:
• wavelength setting resolution (wavelength difference between two adjacent data points);
• wavelength setting uncertainty;
• 3 dB spectral bandwidth of the light source or the tuneable narrowband detector (TND);
• source spontaneous emission (SSE) noise floor relative to peak power for the light source;
• degree of polarization (DOP).

– 10 – IEC 61300-3-7:2021 © IEC 2021
The following performance guidelines shall be followed.
– The wavelength setting resolution shall be less than half the smallest resolvable attenuation
feature. For example, when the attenuation changes over 1 nm the wavelength resolution
shall be less than 0,5 nm.
– The 3 dB spectral bandwidth for the light source or the TND shall be less than half the
wavelength resolution of the measurement.
– When the DOP of the source is more than 5 %, the polarization dependence of the detection
system shall be considered as part of the total insertion loss uncertainty.
The impact of the source SSE noise floor on the uncertainty of the measurement depends
strongly on the wavelength dependence of the DUT. For CWDM components, this shall be
considered. The total ASE power over the measurement range limits the dynamic range of the
measurement.
Additional information can be found in Annex B.
4.3 General explanation of attenuation and return loss
4.3.1 Attenuation
), is the relative optical power reduction caused by the insertion of the DUT
Attenuation, A(λ
k
into an optical path and is illustrated in Figure 1. It is a function of wavelength. It is expressed
as shown in Formula (1):
A λ Pλ−P λ dB)
( ) ( ) ( ) (1)
k itkk
where
P (λ ) is the optical power, as a function of wavelength, incident on and measured at the input
i k
port of the DUT, expressed in dBm;
P (λ ) is the optical power, as a function of wavelength, transmitted through and measured at
t k
the output port of the DUT, expressed in dBm.
4.3.2 Return loss
Return loss, RL(λ ) is the optical power reflected by the DUT relative to the incident power. It is
k
a function of wavelength and is illustrated in Figure 1. It is expressed as shown in Formula (2):
RL(λ ) Pλ( )−P(λ )  (dB)
(2)
kkkir
where
P (λ ) is the optical power, as a function of wavelength, incident on and measured at the input
i k
port of the DUT, expressed in dBm;
P (λ ) is the optical power, as a function of wavelength, reflected by and measured from the
r k
input port of the DUT, expressed in dBm.
=
=
Figure 1 – Generic explanation of attenuation and return loss
4.4 Device under test (DUT)
The DUT may have more than two ports. Only two ports are relevant for attenuation testing
(input and output port) and only one is relevant for return loss testing (input port). It is not a
requirement to measure attenuation and return loss at the same time.
Eight two-port DUT configurations are described in Table 1. Port connections may consist of
bare fibre, connector plug, or receptacle. IEC 61300-3-4 describes multiple connection methods
in detail. This document focuses on type 4 and type 7. If a multiport DUT is to be measured,
all unused ports shall be terminated. For additional details, refer to Annex C.
A summary of the applicable DUT can be found in Annex A.
Table 1 – Device under test categories
Type Description DUT
Fibre to fibre
(component)
Fibre to fibre
2 (splice or field-mountable connector
set)
3 Fibre to plug
Plug to plug
(component)
Plug to plug
(patchcord)
Single plug
(pigtail)
Receptacle to receptacle
(component)
Receptacle to plug
(component)
Key
C: optical component
NOTE Type 1 can be measured using a temporary joint replacing optical
connectors.
– 12 – IEC 61300-3-7:2021 © IEC 2021
4.5 Measurement methods
The following measurement configurations are defined in Table 2. The applicable reference test
method (RTM) is shown in Table 3.
Table 2 – Measurement methods
Detection
Method Name Light source Example
system
A Broadband light source BBS TND BBS + DUT + OSA
Tuneable narrow band light
B TNLS BBD TLS + DUT + OPM
source
Set of multiple fixed narrow
C NLS BBD N x DFB-LD + DUT + OPM
band light sources
Table 3 – Reference test methods
Resolution bandwidth Wavelength band RTM Alternative
(RBW)
< 0,1 nm Any Method B Method A
≥ 0,1 nm C-band and L-band Method B Method A, method C
≥ 0,1 nm Not C-band and L-band Method A Method B, method C

a) Method A – Broadband light source (BBS)
In method A, a broadband light source (BBS) is used with a tuneable narrowband detector
(TND). A common implementation is to use an optical spectrum analyzer (OSA) for the TND.
In this implementation, the OSA controls the wavelength range, the measurement
wavelength and resolution bandwidth. The optical power and bandwidth of the BBS shall be
large enough to cover the attenuation of the DUT and the power measurement dynamic
range of the OSA.
b) Method B – Tuneable narrowband light source (TNLS)
In method B, a tuneable narrowband light source (TNLS) is used with a broadband detection
system (BBD). The most likely implementation of method B is the use of a tuneable laser
source (TLS) with an optical power meter (OPM). In this method, the TLS controls the
wavelength range, the measurement wavelength and resolution bandwidth. Given the
narrow linewidth and high DOP, care shall be taken to minimize the test system background
return loss. This will help to avoid coherent interference in the power measurement.
c) Method C – Set of multiple fixed narrowband light sources (NLS)
In method C, a set of narrowband light sources are used with a broadband detector (BBD).
This method is suitable for a DUT which has a small wavelength dependent loss and is
specified for operation over a wide wavelength range. A common implementation of
method C is the use of a set of fixed laser sources with an N x 1 optical branching device or
optical switch. The use of a switch prevents the need to turn off the light sources not in use.
This can reduce the time needed for laser power stabilization. An OPM is typically used as
the BBD.
5 Apparatus
5.1 General
All methods share a common basic setup:
• optical source;
• source depolarizer (optional);

• return path branching device (for RL measurement);
• temporary joint (TJ);
• fibre;
• reference plug (RP);
• reference adapter (RA);
• termination (for RL measurement);
• power detection system.
5.2 Optical source
5.2.1 Method A – Broadband light source (BBS)
A BBS is used for the source in method A. The BBS emits light over a continuous wavelength
range with various characteristics depending on its type. Examples of a BBS are a white light
source (i.e. tungsten lamp), a light emitting diode (LED), a super-luminescent LED (SLED) or
an optical fibre amplifier (OFA) without an input optical signal.
The wavelength range shall be wide enough to cover the entire specified DUT wavelength
operating range. The output power shall be high enough for A(λ ) and RL(λ ) to be measured.
k k
The spectral power density instability shall be smaller than ±0,05 dB as observed for at least
30 min.
5.2.2 Method B – Tuneable narrowband light source (TNLS)
A TNLS emits a narrow spectrum of light that can be spectrally tuned over the specified
wavelength range. There are various characteristics depending on its type. Examples of
applicable TNLS technologies are a BBS with a tuneable filter, an external cavity tuneable laser,
a tuneable DFB laser diode and a tuneable erbium-doped fibre laser. The wavelength accuracy
and spectral bandwidth shall be specified. Typical values are provided in Annex B.
5.2.3 Method C – Set of multiple fixed narrowband light sources (NLS)
Method C is based on a set of N discrete wavelengths. The wavelengths may be emitted by
sources such as a Fabry-Perot (FP) laser diode (LD) or distributed feedback (DFB) LD.
The set of NLS shall cover the specified wavelength range to be measured. When using a N × 1
fibre optic branching device or fibre optic switch, N is equal to the number of wavelengths to be
measured and NLS used.
When a TLS is used as the NLS, the requirement for a TLS is same as that for a NLS.
5.3 Depolarizer
The measurement results [A(λ ) and RL(λ )] shall be averaged as a function of the state of
k k
polarization (SOP). Sources based on lasers will be highly polarized (DOP is nearly equal to
100 %) while sources like LED and BBS will be highly depolarized (DOP is less than 5 %). For
sources with high DOP, a depolarizer will be required. The depolarizer shall reduce the DOP to
< 5 %.
There are two approaches for obtaining the polarization averaged value of A(λ ) and RL(λ ).
k k
• Direct approach: A depolarizer based on an active or passive device is connected at the
output port of the source in order to reduce its DOP. This allows direct measurement of the
averaged A(λ ) and RL(λ ). The averaging time of the power detection system shall be
k k
greater than 2 times the quoted de-polarization time.

– 14 – IEC 61300-3-7:2021 © IEC 2021
• Indirect approach: Measure A(λ ) and RL(λ ) as a function of the state of polarization (SOP)
k k
to obtain the average value of A(λ ) and RL(λ ) from the measurement results. This requires
k k
multiple measurements be made and recorded. In this case, the role of the depolarizer is
fulfilled by a polarization controller that either deterministically sets a chosen sequence of
SOP or randomly scans many SOP.
5.4 Power detection systems
5.4.1 Method A – Tuneable narrowband detection (TND)
The measurement system shall be stable within specified limits over the measuring time. For
measurements where the connection to the detector shall be separated between measurements,
the repeatability specification shall be less than 0,02 dB.
The TND (typically an OSA) measures the output optical power at a specified wavelength over
the wavelength range. Generally, an OSA has an optical filter function inside. The resolution
bandwidth (RBW) is typically specified at –3 dB or the full width at half the maximum. The RBW
shall be specified in accordance with the wavelength setting interval. In order to avoid false
interpretation of artefacts in the measurement, the optical rejection ratio shall be specified. An
example of such specification could be –20 dB at 0,1 nm away from the centre wavelength. If
a detailed assessment of the OSA RBW is required, the filter shape of the OSA should be
measured. This is typically achieved by measuring the envelope of a DFB known to have a
spectrum much narrower than the OSA RBW.
The power measurement range and sensitivity shall be high enough for A(λ ) and RL(λ ) to be
k k
measured in accordance with the DUT specification. The amplitude uncertainty due to
polarization dependence of the OSA shall be less than the desired uncertainty to be measured.
5.4.2 Method B and C – Broadband detection (BBD)
The broadband detection system (BBD) measures an integrated optical power over a wide range.
A typical BBD consists of an optical power sensor, a mechanism for coupling a fibre to it and
associated detection electronics. These devices are most commonly referred to as an OPM.
The performance of the measurement system shall be stable within specified limits over the
measuring time. For measurements where the connection to the detector shall be separated
between measurements, the repeatability specification shall be less than 0,02 dB. A detector
with a large sensitive area may be used to achieve this.
The power measurement range of the BBD shall cover the peak power of the light source and
intended attenuation of the DUT. The minimum detectable power is recommended to be more
than 10 dB smaller than the optical power to be measured. The amplitude uncertainty due to
polarization dependence of the OPM shall be less than the desired uncertainty to be measured.
The preferred OPM parameters are given in Table 4.

Table 4 – Preferred OPM parameters
Type Maximum nonlinearity Relative uncertainty
dB dB
±0,01
(attenuation ≤ 10 dB)
Single mode ≤ 0,02
±0,05
(10 dB < attenuation ≤ 60 dB)
In order to ensure that all light exiting the fibre is detected by the OPM, the sensitive area of the detector and the
relative position between it and the fibre should be compatible with the numerical aperture of the fibre.
NOTE Common sources of relative uncertainty are polarization dependence and interference with reflections from
the OPM and fibre connector surfaces. The sensitivity of the power meter to such reflections can be characterized
by the parameter spectral ripple, determined as the periodic change in responsivity versus the wavelength of a
coherent light source.
5.5 Branching device (BD)
The branching device is used to connect the light source to the DUT. It will split the reflected
light from the DUT to the return loss detection system.
The splitting ratio of the BD shall be stable during the measurement time. The wavelength
dependent loss and return loss of the BD should be smaller than the DUT to be measured. The
uncertainty due to polarization dependence loss of the BD shall be less than the desired
uncertainty of A(λ ) to be measured and in general < 0,05 dB. The return loss should be at least
n
10 dB greater than the maximum RL(λ ) to be measured. The directivity should be at least 10 dB
k
greater than the maximum RL(λ ) to be measured.
k
5.6 Termination
A termination is a device, process or manipulation which induces the maximum attenuation
possible. Terminations shall also have a large return loss. Common terminations are:
a) angled fibre ends such as the use of an angled physical contact (APC) connector or angled
cleave (the angle should be more than 8°);
b) application of a refractive index matching material to the fibre end in air;
c) high return loss achieved with a mandrel wrap (tightly coiling the fibre per the manufacturer’s
recommendation).
The termination return loss shall be 15 dB greater than the maximum RL(λ ) to be measured.
k
Unless otherwise specified, all unused DUT ports (input or outputs) shall be terminated during
the RL measurement.
5.7 Temporary joint (TJ)
This is a method, device, or mechanical fixture for temporarily aligning two fibre ends into a
stable, reproducible, low-loss joint. It is used when direct connection between the DUT and the
measurement system is not achievable by a standard connector. Examples are a precision
V‑groove, vacuum chuck, micromanipulator, fusion splice or mechanical splice. The attenuation
of the temporary joint shall be stable to within 10 % of the required measurement uncertainty in
dB over the time taken to measure P P and P A suitable refractive index matching materi
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