IEC 61300-3-7:2009
(Main)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
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
IEC 61300-3-7:2009 describes the various methods available to measure the wavelength dependence of attenuation and return loss, of single-mode passive optical components (POC) used in fibre-optic (FO) telecommunications. This second edition cancels and replaces the first edition published in 2000. Changes from the previous edition of this standard are to reflect changes made to IEC 61300-1 and covers unidirectional and bi-directional methods of measurement.
Dispositifs d'interconnexion et composants passifs fibroniques - Méthodes fondamentales d'essais et de mesures - Partie 3-7: Examens et mesures - Dépendance par rapport à la longueur d’onde de l’affaiblissement et de l’affaiblissement de réflexion des composants unimodaux
IEC 61300-3-7:2009 décrit les diverses méthodes disponibles de mesure de la dépendance par rapport à la longueur d’onde de l’affaiblissement A(l) et de l’affaiblissement de réflexion RL(l), pour les composants optiques passifs (POC, passive optical components) unimodaux utilisés dans les télécommunications à fibres optiques. (FO). Toutefois, elle ne s'applique pas aux dispositifs à multiplexeur par répartition en longueur d'onde à forte densité (DWDM – dense wavelength division multiplexing). Les méthodes de mesure de la dépendance par rapport à la longueur d’onde de l’affaiblissement des dispositifs DWDM sont décrites dans l’IEC 61300-3-29. L’IEC 62074-1 donne une définition des types de dispositifs WDM. Trois cas de mesure sont pris en considération dans le présent document:
- Mesurage de A(l) seulement;
- Mesurage de RL(l) seulement;
- Mesurage simultané de A(l) et RL(l).
Ces mesurages peuvent être effectués dans une seule direction (unidirectionnel) ou de manière bidirectionnelle. Cette deuxième édition annule et remplace la première édition parue en 2000. Elle constitue une révision technique. Les modifications par rapport à l’édition précédente de la présente norme visent à refléter les modifications apportées à l’IEC 61300-1 et traitent des méthodes de mesure unidirectionnelles et bidirectionnelles.
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IEC 61300-3-7
Edition 2.0 2009-01
INTERNATIONAL
STANDARD
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
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IEC 61300-3-7
Edition 2.0 2009-01
INTERNATIONAL
STANDARD
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
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
U
ICS 33.180.20 ISBN 978-2-88910-498-7
– 2 – 61300-3-7 © IEC:2009(E)
CONTENTS
FOREWORD.4
1 Scope.6
2 Normative references .6
3 Abbreviations and acronyms.6
4 General .8
4.1 General description .8
4.2 Spectral conditions.9
4.3 Definition.9
4.3.1 Attenuation .9
4.3.2 Return loss .10
4.4 Device under test .10
4.5 Measurement methods .11
4.5.1 Method A – Broadband light source (BBS).11
4.5.2 Method B – Tuneable narrowband light source (TLS).12
4.5.3 Method C – Set of multiple fixed narrowband light sources (NLS) .12
4.5.4 Method D – Tuneable OTDR.13
4.5.5 Reference method .13
5 Apparatus.13
5.1 Wavelength source.13
5.1.1 Method A – Broadband light source .13
5.1.2 Method B – Tuneable narrowband light source .13
5.1.3 Method C – Set of N narrowband light sources .14
5.1.4 Method D – Tuneable OTDR.14
5.1.5 Depolarizer.14
5.2 Detection system.15
5.2.1 Method A, Method B.2 and Method C.2 tuneable narrowband
detection spectrum .15
5.2.2 Method B.1 and Method C.1 broadband detection spectrum .15
5.3 Branching devices .15
5.4 Termination .16
6 Procedure .16
6.1 Method A – broadband light source .16
6.1.1 Attenuation-only .16
6.1.2 Return-loss-only .17
6.1.3 Attenuation and return loss.18
6.2 Method B – Tuneable narrowband light source .19
6.3 Method C – Set of multiple fixed narrowband light sources .20
6.3.1 Attenuation-only .20
6.3.2 Return-loss-only .22
6.3.3 Attenuation and return loss.23
6.4 Test results .25
7 Details to be specified .25
7.1 Source .25
7.1.1 Broadband source .25
7.1.2 Tuneable or discrete narrowband light source.26
7.1.3 Depolarizer.26
61300-3-7 © IEC:2009(E) – 3 –
7.2 Detection system.26
7.2.1 Optical power meter .26
7.2.2 Optical spectrum analyser .26
7.3 Reference branching device .26
7.4 Termination .26
Annex A (informative) Device under test configurations, terminations and product
types .27
Annex B (informative) Typical light source characteristics.29
Figure 1 – Wavelength dependence of attenuation and return loss .10
Figure 2 – Method A – Attenuation-only measurement .17
Figure 3 – Method A – Return-loss-only measurement .18
Figure 4 – Method A – Attenuation and return loss measurement.19
Figure 5 – Method C – Attenuation-only measurement .21
Figure 6 – Method C Return-loss-only measurement.22
Figure 7 – Method C – Attenuation and return loss measurement .24
Figure 8 – Wavelength dependent attenuation .25
Table 1 – Test methods and characteristics .11
Table 2 – Wavelength dependent attenuation and return loss .25
Table A.1 – Device under test configurations/terminations .27
Table A.2 – Possible types of passive optical components (POC) .27
Table B.1 – Types of broadband light source (BBS) and main characteristics .29
Table B.2 – Types of tuneable light source (TLS) and main characteristics .30
– 4 – 61300-3-7 © IEC:2009(E)
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
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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.
International Standard IEC 61300-3-7 has been prepared by subcommittee 86B: Fibre optic
interconnecting devices and passive components, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2000. It constitutes a
technical revision.
Changes from the previous edition of this standard are to reflect changes made to IEC 61300-
1 and covers unidirectional and bi-directional methods of measurement.
61300-3-7 © IEC:2009(E) – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
86B/2771/FDIS 86B/2803/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 of 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 publication will remain unchanged until
the maintenance result 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 standard may be issued at a later date.
– 6 – 61300-3-7 © IEC:2009(E)
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 the various methods available to measure the wavelength
dependence of attenuation A(λ) and return loss RL(λ), of single-mode passive optical
components (POC) used in fibre-optic (FO) telecommunications. 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.
Definition of WDM device types is given in IEC 62074-1.
Three measurement cases are herein considered:
• Measurement of A(λ) only;
• Measurement of RL(λ) only;
• Measurement of A(λ) and RL(λ) at the same time.
These measurements may be performed in one direction (unidirectional) or bi-directionally.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced (including any amendments) applies.
IEC 61300-3-29, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-29: Examinations and measurements – Measurement
techniques for characterising the amplitude of the spectral transfer function of DWDM
components
IEC 62074-1, Fibre optic WDM devices – Part 1: Generic specification
3 Abbreviations and acronyms
For the purposes of this document, the following abbreviations and acronyms apply:
A attenuation
A(λ) wavelength dependent attenuation
ASE amplified spontaneous emission
BBD broadband detection
BBS broadband source
61300-3-7 © IEC:2009(E) – 7 –
BD branching devices
CWDM coarse wavelength division multiplexing
DFB distributed feedback (laser)
DOP degree of polarization
DUT device under test
DWDM dense wavelength division multiplexing
DWS discrete wavelength source
ECL external cavity (tuneable) laser
EDFL erbium-doped fibre laser
FA fibre amplifier
FP Fabry-Perot (laser)
G(λ) test system constant
IL insertion loss
IL(λ) wavelength dependent insertion loss
λ wavelength
NLS narrowband light sources
OPM optical power meter
OSA optical spectrum analyser
P (λ) wavelength dependent power incident on the DUT
i
P (λ) wavelength dependent power reflected by the DUT (from the input port of the DUT)
r
P (λ) wavelength dependent power transmitted through the DUT
t
RL
P ( λ ) wavelength dependent reflected power measured for the determination of the test
G
set-up constant
RL
P (λ ) wavelength dependent incident power measured for the determination of the test
Gi
set-up constant
A
P (λ ) wavelength dependent power incident on the DUT in case of the wavelength
i
dependent attenuation measurement
– 8 – 61300-3-7 © IEC:2009(E)
RL
P (λ ) wavelength dependent power incident on the DUT in case of the wavelength
i
dependent return loss measurement
PDL polarization dependent loss
POC passive optical components
PON passive optical network
RBD reference branching device
RBW resolution bandwidth
RL return loss
RL(λ) wavelength dependent return loss
RTM reference test method
SMSR side mode suppression ratio
SOA semiconductor amplifier
SOP state of polarization
T termination
TJ temporary joint
TND tuneable narrowband detection (system)
TLS tuneable narrowband light source
TN-OTDR tuneable OTDR
WDM wavelength division multiplexing
4 General
4.1 General description
A(λ) and RL(λ) are expressed in decibels (dB), transmitted by or reflected from a device
under test (DUT) resulting from its insertion within a fibre-optic (FO) telecommunication
system. A(λ) and RL(λ) are obtained by comparing the optical power incident on the DUT with
the optical power
• transmitted at the output port of the DUT;
• reflected from the input port of the DUT.
The DUT is inverted in order to get a bi-directional measurement. Measurements should be
taken in both directions and averaged expect where the device is intentionally not
bidirectional no averaging shall be done.
The term “return loss” should not be used as equivalent to reflectance. Both have completely
different meanings.
61300-3-7 © IEC:2009(E) – 9 –
4.2 Spectral conditions
A(λ) and RL(λ) measurements are made over a wavelength range defined in the DUT
specifications. The DUT spectral characteristics also defined in the DUT specifications should
be used in turn to define the spectral characteristics of the measurement system, such as its
wavelength resolution (spectral difference between two adjacent data points) and uncertainty
(spectral uncertainty around each data point) which in turn will define the bandwidth of the
measurement system.
4.3 Definition
4.3.1 Attenuation
A(λ) refers to the power decrease of light transmitted by the DUT as a function of wavelength.
It is expressed as follows:
⎡ P()λ ⎤
t
[dB] (1)
A( λ ) = − 10 × log
⎢ ⎥
P()λ
⎣ i ⎦
where
P (λ) is the optical power, as a function of wavelength, transmitted through the input
t
port of the DUT and measured at the output port of the DUT, expressed in watt;
P (λ) is the optical power, as a function of wavelength, incident on and measured at
i
the input port of the DUT, expressed in watt;
for bi-directional measurement,
P (λ) is the optical power, as a function of wavelength, transmitted through the output
t
port of the DUT and measured at the input port of the DUT, expressed in watt;
P (λ) is the optical power, as a function of wavelength, incident on and measured at
i
the output port of the DUT, expressed in watt.
Figure 1 illustrates the process.
– 10 – 61300-3-7 © IEC:2009(E)
Port A Port B
DUT
Incident spectrum P(λ)
i Transmitted spectrum P (λ)
t
Input
Output
a) Unidirectional measurement
Incident spectrum P(λ)
i
Transmitted spectrum P (λ)
t
Reflected spectrum P (λ)
r
Port B
DUT Output
Port A
/Input Incident spectrum P(λ)
i
Transmitted spectrum P (λ)
t
Reflected spectrum P (λ)
r
b) Bi-directional measurement
IEC 2334/08
Figure 1 – Wavelength dependence of attenuation and return loss
4.3.2 Return loss
RL(λ) refers to the power decrease of light reflected by the DUT as a function of wavelength.
It is expressed as follows:
⎡ P()λ ⎤
r
RL(λ ) = − 10 × log [dB] (2)
⎢ ⎥
P()λ
⎣ i ⎦
where
P (λ) is the optical power, as a function of wavelength, reflected by and measured from
r
the input port of the DUT, expressed in watt;
P (λ) is the optical power, as a function of wavelength, incident on and measured at
i
the input port of the DUT, expressed in watt;
for bi-directional measurement,
P (λ) is the optical power, as a function of wavelength, reflected by and measured from
r
the output port of the DUT, in units of W;
P (λ) is the optical power, as a function of wavelength, incident on and measured at
i
the output port of the DUT, in units of W.
Figure 1 illustrates the process.
4.4 Device under test
The DUT may have more than two ports. However, since measurement of A(λ) is made across
only two ports, be they unidirectional or bi-directional, the DUT in this standard shall be
61300-3-7 © IEC:2009(E) – 11 –
described as having two ports. The same is true for measurement of RL(λ), except that in this
case, the measurement is made from only one port at a time.
Eight different DUT configurations are herein considered and described in Table B.1 of
Annex B. The differences between these configurations are primarily in the terminations of the
optical ports. Terminations may consist of bare fibre, connector plug, or receptacle. The
various types of product that are herein under consideration are illustrated in Table B.2 of
Annex B.
4.5 Measurement methods
The characterization of the DUT spectral response can be carried out on several discrete
wavelengths along a wavelength range of interest, continuously over the range or a
combination of the above. The way this characterization is performed defines the various test
methods.
Four methods, A to D, are described for measuring A(λ) and RL(λ). The methods are listed
below in the order of their introduction. For some methods, multiple configurations are
possible.
Table 1 summarizes the different test methods and their main characteristics.
NOTE Different test configurations and methods will result in different accuracies of the attenuation being
measured. In cases of dispute, the RTM should be used.
Table 1 – Test methods and characteristics
Method Name Light source Detection Example Comments
system
A BBS BBS TND BBS + DUT + OSA Alternate
B TLS To be depolarised +
coherence control
B.1 TLS + BBD TLS BBD TLS + DUT + OPM
B.1.1 TLS in start-stop-measure TLS in start-stop- BBD TLS + DUT + OPM Alternate
mode + BBD measure mode
B.1.2 TLS in sweep mode + BBD TLS in sweep mode BBD TLS + DUT + OPM Alternate
B.2 TLS + TND TLS TND TLS + DUT + OSA
B.2.1 TLS in start-stop-measure TLS in start-stop- TND TLS + DUT + OSA RTM
mode + TND measure mode
B.2.2 TLS in sweep mode + TND TLS in sweep mode TND TLS + DUT + OSA Alternate
C Set of N NLS To be depolarised +
coherence control
C.1 N NLS + BBD N NLS BBD N NLS + N x 1 coupler + Alternate
DUT + OPM
C.2 N NLS + TND N NLS TND N NLS + N x 1 coupler + Alternate
DUT + OSA
D TN-OTDR TN OTDR TN-OTDR TN-OTDR + DUT Alternate
4.5.1 Method A – Broadband light source (BBS)
In Method A, a broadband light source (BBS) is used with a tuneable narrowband filtering
detection system (TND).
A possible implementation of Method A is the use of the BBS with an optical spectrum
analyser (OSA). Method A has the advantage of providing all the required wavelength range
– 12 – 61300-3-7 © IEC:2009(E)
in a single test and the test sampling rate is defined by the TND. Measurement of the
wavelength dependence should be done using the BBS having high quality spectral power density.
Use of a suitable TND spectral filter is recommended for an accurate measurement.
4.5.2 Method B – Tuneable narrowband light source (TLS)
In Method B, a tuneable narrowband light source (TLS) is used with two possible different
detection systems.
4.5.2.1 Method B.1 – Tuneable narrowband light source and broadband detection
system
In Method B.1, a TLS is used with a broadband detection system (BBD).
A possible implementation of Method B.1 is the use of the TLS with an optical power meter
(OPM). The TLS can be used in two different modes with the BBD:
a) Method B.1.1 – Step-by-step tuneable narrowband light source and broadband
detection system
In this method, the bandwidth of the measurement is defined by the TLS linewidth. A linewidth
too narrow will create spurious noise, coherence interference effects and unnecessary
amount of data; a linewidth too wide will not provide enough resolution to the DUT spectral
response. An estimate of the DUT bandwidth and the application of the Nyquist criterion are
required in order to properly define the TLS linewidth.
b) Method B.1.2 – Swept tuneable narrowband light source and broadband detection
system
In this method, the bandwidth of the measurement is defined by the bandwidth of the
detection system, not by the TLS linewidth. An estimate of the DUT bandwidth and the
application of the Nyquist criterion are required in order to properly define the bandwidth of
the detection system.
4.5.2.2 Method B.2 – Tuneable narrowband light source and tuneable narrowband
detection system
In Method B.2, a TLS is used with a TND. Synchronization between both ends of the
measurement system is required. This method is particularly useful for very narrowband
components.
A possible implementation of Method B.2 is the use of the TLS with an OSA. The TLS can be
used in two different modes with the TND:
a) Method B.2.1 – Step-by-step tuneable narrowband light source and tuneable
narrowband detection system
The measurement bandwidth for Method B.2.1 is the same as in Method B.1.1.
b) Method B.2.2 – Swept tuneable narrowband light source and tuneable narrowband
detection system
The measurement bandwidth for Method B.2.2 is the same as in Method B.1.2.
4.5.3 Method C – Set of multiple fixed narrowband light sources (NLS)
In Method C, a set of N narrowband light sources (NLS) is used with two possible different
detection systems. This method is particularly useful when the DUT spectral response is
expected to be quite non-uniform and the regions of non-uniformity need to be carefully
assessed.
61300-3-7 © IEC:2009(E) – 13 –
A possible implementation of Method C is the use of a set of N DFB lasers with N x 1 coupler
and/or 1 x N splitter on each side of the DUT with one OPM for each DFB.
4.5.3.1 Method C.1 – NLS and BBD
Method C.1 is a variation of Method B.1 in which the TLS is replaced by the set of N NLS.
4.5.3.2 Method C.2 – NLS and TND
Method C.2 is a variation of Method B.2 in which the TLS is replaced by the set of N NLS.
4.5.4 Method D – Tuneable OTDR
In Method D, a tuneable narrowband light is emitted by TN-OTDR and appropriate detection
by the TN-OTDR is used.
4.5.5 Reference method
The reference test method (RTM) for measuring A(λ) and RL(λ) shall be Method B.2.1.
5 Apparatus
The following subclauses describe the test set-up components.
5.1 Wavelength source
The followin
...
IEC 61300-3-7 ®
Edition 2.0 2009-01
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 – Méthodes
fondamentales d'essais et de mesures –
Partie 3-7: Examens et mesures – Dépendance par rapport à la longueur d’onde
de l’affaiblissement et de l’affaiblissement de réflexion des composants
unimodaux
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IEC 61300-3-7 ®
Edition 2.0 2009-01
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 – Méthodes
fondamentales d'essais et de mesures –
Partie 3-7: Examens et mesures – Dépendance par rapport à la longueur d’onde
de l’affaiblissement et de l’affaiblissement de réflexion des composants
unimodaux
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.20 ISBN 978-2-8322-9338-6
– 2 – IEC 61300-3-7:2009 IEC 2009
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Abbreviations and acronyms . 6
4 General . 8
4.1 General description . 8
4.2 Spectral conditions . 9
4.3 Definition . 9
4.3.1 Attenuation . 9
4.3.2 Return loss . 10
4.4 Device under test . 10
4.5 Measurement methods . 11
4.5.1 Method A – Broadband light source (BBS) . 11
4.5.2 Method B – Tuneable narrowband light source (TLS) . 12
4.5.3 Method C – Set of multiple fixed narrowband light sources (NLS) . 12
4.5.4 Method D – Tuneable OTDR . 13
4.5.5 Reference method . 13
5 Apparatus . 13
5.1 Wavelength source . 13
5.1.1 Method A – Broadband light source . 13
5.1.2 Method B – Tuneable narrowband light source . 13
5.1.3 Method C – Set of N narrowband light sources . 14
5.1.4 Method D – Tuneable OTDR . 14
5.1.5 Depolarizer . 14
5.2 Detection system . 15
5.2.1 Method A, Method B.2 and Method C.2 tuneable narrowband
detection spectrum . 15
5.2.2 Method B.1 and Method C.1 broadband detection spectrum . 15
5.3 Branching devices . 15
5.4 Termination . 16
6 Procedure . 16
6.1 Method A – broadband light source . 16
6.1.1 Attenuation-only . 16
6.1.2 Return-loss-only . 17
6.1.3 Attenuation and return loss . 18
6.2 Method B – Tuneable narrowband light source . 19
6.3 Method C – Set of multiple fixed narrowband light sources . 20
6.3.1 Attenuation-only . 20
6.3.2 Return-loss-only . 22
6.3.3 Attenuation and return loss . 23
6.4 Test results . 25
7 Details to be specified . 25
7.1 Source . 25
7.1.1 Broadband source . 25
7.1.2 Tuneable or discrete narrowband light source . 26
7.1.3 Depolarizer . 26
7.2 Detection system . 26
7.2.1 Optical power meter . 26
7.2.2 Optical spectrum analyser . 26
7.3 Reference branching device . 26
7.4 Termination . 26
Annex A (informative) Device under test configurations, terminations and product
types . 27
Annex B (informative) Typical light source characteristics . 29
Figure 1 – Wavelength dependence of attenuation and return loss . 10
Figure 2 – Method A – Attenuation-only measurement . 17
Figure 3 – Method A – Return-loss-only measurement . 18
Figure 4 – Method A – Attenuation and return loss measurement. 19
Figure 5 – Method C – Attenuation-only measurement . 21
Figure 6 – Method C Return-loss-only measurement . 22
Figure 7 – Method C – Attenuation and return loss measurement . 24
Figure 8 – Wavelength dependent attenuation . 25
Table 1 – Test methods and characteristics . 11
Table 2 – Wavelength dependent attenuation and return loss . 25
Table A.1 – Device under test configurations/terminations . 27
Table A.2 – Possible types of passive optical components (POC) . 27
Table B.1 – Types of broadband light source (BBS) and main characteristics . 29
Table B.2 – Types of tuneable light source (TLS) and main characteristics . 30
– 4 – IEC 61300-3-7:2009 IEC 2009
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 in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for 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
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
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.
International Standard IEC 61300-3-7 has been prepared by subcommittee 86B: Fibre optic
interconnecting devices and passive components, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2000. It constitutes a
technical revision.
Changes from the previous edition of this standard are to reflect changes made to IEC 61300-
1 and covers unidirectional and bi-directional methods of measurement.
The text of this standard is based on the following documents:
FDIS Report on voting
86B/2771/FDIS 86B/2803/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 of 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 publication will remain unchanged until
the maintenance result 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.
– 6 – IEC 61300-3-7:2009 IEC 2009
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 the various methods available to measure the wavelength
dependence of attenuation A(λ) and return loss RL(λ), of single-mode passive optical
components (POC) used in fibre-optic (FO) telecommunications. 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.
Definition of WDM device types is given in IEC 62074-1.
Three measurement cases are herein considered:
λ) only;
• Measurement of A(
• Measurement of RL(λ) only;
• Measurement of A(λ) and RL(λ) at the same time.
These measurements may be performed in one direction (unidirectional) or bi-directionally.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced (including any amendments) applies.
IEC 61300-3-29, Fibre optic interconnecting devices and passive components – Basic test
and measurement procedures – Part 3-29: Examinations and measurements – Measurement
techniques for characterising the amplitude of the spectral transfer function of DWDM
components
IEC 62074-1, Fibre optic WDM devices – Part 1: Generic specification
3 Abbreviations and acronyms
For the purposes of this document, the following abbreviations and acronyms apply:
A attenuation
A(λ) wavelength dependent attenuation
ASE amplified spontaneous emission
BBD broadband detection
BBS broadband source
BD branching devices
CWDM coarse wavelength division multiplexing
DFB distributed feedback (laser)
DOP degree of polarization
DUT device under test
DWDM dense wavelength division multiplexing
DWS discrete wavelength source
ECL external cavity (tuneable) laser
EDFL erbium-doped fibre laser
FA fibre amplifier
FP Fabry-Perot (laser)
G(λ) test system constant
IL insertion loss
IL(λ) wavelength dependent insertion loss
λ wavelength
NLS narrowband light sources
OPM optical power meter
OSA optical spectrum analyser
Pi(λ) wavelength dependent power incident on the DUT
Pr(λ) wavelength dependent power reflected by the DUT (from the input port of the DUT)
P (λ) wavelength dependent power transmitted through the DUT
t
RL
P (λ ) wavelength dependent reflected power measured for the determination of the test
G
set-up constant
RL
wavelength dependent incident power measured for the determination of the test
P (λ )
Gi
set-up constant
A
P (λ ) wavelength dependent power incident on the DUT in case of the wavelength
i
dependent attenuation measurement
– 8 – IEC 61300-3-7:2009 IEC 2009
RL
wavelength dependent power incident on the DUT in case of the wavelength
P (λ )
i
dependent return loss measurement
PDL polarization dependent loss
POC passive optical components
PON passive optical network
RBD reference branching device
RBW resolution bandwidth
RL return loss
RL(λ) wavelength dependent return loss
RTM reference test method
SMSR side mode suppression ratio
SOA semiconductor amplifier
SOP state of polarization
T termination
TJ temporary joint
TND tuneable narrowband detection (system)
TLS tuneable narrowband light source
TN-OTDR tuneable OTDR
WDM wavelength division multiplexing
4 General
4.1 General description
A(λ) and RL(λ) are expressed in decibels (dB), transmitted by or reflected from a device
under test (DUT) resulting from its insertion within a fibre-optic (FO) telecommunication
system. A(λ) and RL(λ) are obtained by comparing the optical power incident on the DUT with
the optical power
• transmitted at the output port of the DUT;
• reflected from the input port of the DUT.
The DUT is inverted in order to get a bi-directional measurement. Measurements should be
taken in both directions and averaged expect where the device is intentionally not
bidirectional no averaging shall be done.
The term “return loss” should not be used as equivalent to reflectance. Both have completely
different meanings.
4.2 Spectral conditions
A(λ) and RL(λ) measurements are made over a wavelength range defined in the DUT
specifications. The DUT spectral characteristics also defined in the DUT specifications should
be used in turn to define the spectral characteristics of the measurement system, such as its
wavelength resolution (spectral difference between two adjacent data points) and uncertainty
(spectral uncertainty around each data point) which in turn will define the bandwidth of the
measurement system.
4.3 Definition
4.3.1 Attenuation
A(λ) refers to the power decrease of light transmitted by the DUT as a function of wavelength.
It is expressed as follows:
P(λ)
t
[dB] (1)
A(λ )=− 10× log
P(λ)
i
where
P (λ) is the optical power, as a function of wavelength, transmitted through the input
t
port of the DUT and measured at the output port of the DUT, expressed in watt;
P (λ) is the optical power, as a function of wavelength, incident on and measured at
i
the input port of the DUT, expressed in watt;
for bi-directional measurement,
P (λ) is the optical power, as a function of wavelength, transmitted through the output
t
port of the DUT and measured at the input port of the DUT, expressed in watt;
P (λ) is the optical power, as a function of wavelength, incident on and measured at
i
the output port of the DUT, expressed in watt.
Figure 1 illustrates the process.
– 10 – IEC 61300-3-7:2009 IEC 2009
Port A Port B
DUT
Incident spectrum P(λ)
i Transmitted spectrum P (λ)
t
Input
Output
a) Unidirectional measurement
Incident spectrum P(λ)
i
Transmitted spectrum P (λ)
t
Reflected spectrum P (λ)
r
Port B
DUT Output
Port A
/Input Incident spectrum P(λ)
i
Transmitted spectrum P (λ)
t
Reflected spectrum P (λ)
r
b) Bi-directional measurement
IEC 2334/08
Figure 1 – Wavelength dependence of attenuation and return loss
4.3.2 Return loss
RL(λ) refers to the power decrease of light reflected by the DUT as a function of wavelength.
It is expressed as follows:
P(λ)
r
RL(λ )=− 10× log [dB] (2)
P(λ)
i
where
P (λ) is the optical power, as a function of wavelength, reflected by and measured from
r
the input port of the DUT, expressed in watt;
P (λ) is the optical power, as a function of wavelength, incident on and measured at
i
the input port of the DUT, expressed in watt;
for bi-directional measurement,
P (λ) is the optical power, as a function of wavelength, reflected by and measured from
r
the output port of the DUT, in units of W;
P (λ) is the optical power, as a function of wavelength, incident on and measured at
i
the output port of the DUT, in units of W.
Figure 1 illustrates the process.
4.4 Device under test
The DUT may have more than two ports. However, since measurement of A(λ) is made across
only two ports, be they unidirectional or bi-directional, the DUT in this standard shall be
described as having two ports. The same is true for measurement of RL(λ), except that in this
case, the measurement is made from only one port at a time.
Eight different DUT configurations are herein considered and described in Table B.1 of
Annex B. The differences between these configurations are primarily in the terminations of the
optical ports. Terminations may consist of bare fibre, connector plug, or receptacle. The
various types of product that are herein under consideration are illustrated in Table B.2 of
Annex B.
4.5 Measurement methods
The characterization of the DUT spectral response can be carried out on several discrete
wavelengths along a wavelength range of interest, continuously over the range or a
combination of the above. The way this characterization is performed defines the various test
methods.
Four methods, A to D, are described for measuring A(λ) and RL(λ). The methods are listed
below in the order of their introduction. For some methods, multiple configurations are
possible.
Table 1 summarizes the different test methods and their main characteristics.
NOTE Different test configurations and methods will result in different accuracies of the attenuation being
measured. In cases of dispute, the RTM should be used.
Table 1 – Test methods and characteristics
Method Name Light source Detection Example Comments
system
A BBS BBS TND BBS + DUT + OSA Alternate
B TLS To be depolarised +
coherence control
B.1 TLS + BBD TLS BBD TLS + DUT + OPM
B.1.1 TLS in start-stop-measure TLS in start-stop- BBD TLS + DUT + OPM Alternate
mode + BBD measure mode
B.1.2 TLS in sweep mode + BBD TLS in sweep mode BBD TLS + DUT + OPM Alternate
B.2 TLS + TND TLS TND TLS + DUT + OSA
B.2.1 TLS in start-stop-measure TLS in start-stop- TND TLS + DUT + OSA RTM
mode + TND measure mode
B.2.2 TLS in sweep mode + TND TLS in sweep mode TND TLS + DUT + OSA Alternate
C Set of N NLS To be depolarised +
coherence control
C.1 N NLS + BBD N NLS BBD N NLS + N x 1 coupler + Alternate
DUT + OPM
C.2 N NLS + TND N NLS TND N NLS + N x 1 coupler + Alternate
DUT + OSA
D TN-OTDR TN OTDR TN-OTDR TN-OTDR + DUT Alternate
4.5.1 Method A – Broadband light source (BBS)
In Method A, a broadband light source (BBS) is used with a tuneable narrowband filtering
detection system (TND).
A possible implementation of Method A is the use of the BBS with an optical spectrum
analyser (OSA). Method A has the advantage of providing all the required wavelength range
– 12 – IEC 61300-3-7:2009 IEC 2009
in a single test and the test sampling rate is defined by the TND. Measurement of the
wavelength dependence should be done using the BBS having high quality spectral power density.
Use of a suitable TND spectral filter is recommended for an accurate measurement.
4.5.2 Method B – Tuneable narrowband light source (TLS)
In Method B, a tuneable narrowband light source (TLS) is used with two possible different
detection systems.
4.5.2.1 Method B.1 – Tuneable narrowband light source and broadband detection
system
In Method B.1, a TLS is used with a broadband detection system (BBD).
A possible implementation of Method B.1 is the use of the TLS with an optical power meter
(OPM). The TLS can be used in two different modes with the BBD:
a) Method B.1.1 – Step-by-step tuneable narrowband light source and broadband
detection system
In this method, the bandwidth of the measurement is defined by the TLS linewidth. A linewidth
too narrow will create spurious noise, coherence interference effects and unnecessary
amount of data; a linewidth too wide will not provide enough resolution to the DUT spectral
response. An estimate of the DUT bandwidth and the application of the Nyquist criterion are
required in order to properly define the TLS linewidth.
b) Method B.1.2 – Swept tuneable narrowband light source and broadband detection
system
In this method, the bandwidth of the measurement is defined by the bandwidth of the
detection system, not by the TLS linewidth. An estimate of the DUT bandwidth and the
application of the Nyquist criterion are required in order to properly define the bandwidth of
the detection system.
4.5.2.2 Method B.2 – Tuneable narrowband light source and tuneable narrowband
detection system
In Method B.2, a TLS is used with a TND. Synchronization between both ends of the
measurement system is required. This method is particularly useful for very narrowband
components.
A possible implementation of Method B.2 is the use of the TLS with an OSA. The TLS can be
used in two different modes with the TND:
a) Method B.2.1 – Step-by-step tuneable narrowband light source and tuneable
narrowband detection system
The measurement bandwidth for Method B.2.1 is the same as in Method B.1.1.
b) Method B.2.2 – Swept tuneable narrowband light source and tuneable narrowband
detection system
The measurement bandwidth for Method B.2.2 is the same as in Method B.1.2.
4.5.3 Method C – Set of multiple fixed narrowband light sources (NLS)
In Method C, a set of N narrowband light sources (NLS) is used with two possible different
detection systems. This method is particularly useful when the DUT spectral response is
expected to be quite non-uniform and the regions of non-uniformity need to be carefully
assessed.
A possible implementation of Method C is the use of a set of N DFB lasers with N x 1 coupler
and/or 1 x N splitter on each side of the DUT with one OPM for each DFB.
4.5.3.1 Method C.1 – NLS and BBD
Method C.1 is a variation of Method B.1 in which the TLS is replaced by the set of N NLS.
4.5.3.2 Method C.2 – NLS and TND
Method C.2 is a variation of Method B.2 in which the TLS is replaced by the set of N NLS.
4.5.4 Method D – Tuneable OTDR
In Method D, a tuneable narrowband light is emitted by TN-OTDR and appropriate detection
by the TN-OTDR is used.
4.5.5 Reference method
The reference test method (RTM) for measuring A(λ) and RL(λ) shall be Method B.2.1.
5 Apparatus
The following subclauses describe the test set-up components.
5.1 Wavelength source
The following subclauses describe the various available sources for performing the
measurements.
5.1.1 Method A – Broadband light source
The BBS is used in Method A. The BBS emits a broadband light over a wavelength range with
various characteristics depending on its type. The BBS may be a white light source, an LED
(surface emitted or edge emitted), a superluminescent LED (SLED) or an amplified
spontaneous emission (ASE) source from an optical fibre amplifier (FA) or from a
semiconductor amplifier (SOA).
The BBS shall cover the specified wavelength range. The wavelength range shall be wide
enough to cover the specified DUT bandwidth and the output power high enough for A(λ) and
RL(λ) to be measured. The spectral power density stability shall be better than ±0,05 dB
during 8 h consecutive.
The test set-up specifications shall meet the detailed requirements of the DUT A(λ) and RL(λ)
as defined in the DUT specifications. As a consequence, the BBS requirements shall be
carefully defined in order to make sure that Method A and set-up will meet those
specifications. The main BBS characteristics are shown in Clause B.1 of Annex B.
5.1.2 Method B – Tuneable narrowband light source
The TLS is used in Method B. The TLS emits a narrowband light that can be spectrally tuned
over a wavelength range with various characteristics depending on its type. The TLS may be
a BBS with a tuneable filter, an external cavity tuneable laser (ECL), a tuneable DFB laser
(DFB) and a tuneable erbium-doped fibre laser (EDFL). Clause B.2 of Annex B describes the
main characteristics of various TLS types.
The test set-up specifications and the selection of the particular sub-sets of Method B shall
meet the detailed requirements of the DUT A(λ) and RL(λ) as defined in the DUT
specifications. As a consequence, the TLS requirements shall be carefully defined in order to
– 14 – IEC 61300-3-7:2009 IEC 2009
make sure that the selected test method and set-up will meet those specifications. In general,
the main TLS specifications that should be carefully considered are (see Clause B.3 of Annex
B):
• centre wavelength;
• side-mode suppression ratio (SMSR), when applicable;
• linewidth; in relation with coherence interference effects, polarization dependent loss (PDL)
effects and spurious reflections, and Nyquist criterion;
• power stability at any operating wavelength; ≤ ±0,05 dB over a continuous 8 h period.
Coherence control shall be applied to the narrowband light source used in TN-OTDR in order
to avoid coherence interference effects.
5.1.3 Method C – Set of N narrowband light sources
The wavelength of each NLS and the total wavelength range of the set is set to cover the
specified wavelengths and total wavelength range together with the detection system. In all
cases, N × 1 couplers or switches are used where N is equal to the number of NLS used.
Method C is based on a set of N discrete wavelengths. The wavelengths may be emitted by
the following sources:
• Fabry-Perot (FP) laser
• DFB laser.
The same TLS requirements typically apply to each narrowband light source used in the
wavelength set.
Coherence control shall be applied to avoid coherence interference effects.
5.1.4 Method D – Tuneable OTDR
The source light emitted by the TN-OTDR shall have the same characteristics as the TLS.
5.1.5 Depolarizer
In all cases, the TLS output shall be depolarized in order to get A(λ) and RL(λ) independent of
any particular state of polarization (SOP) i.e. the averaged value over all possible SOPs.
Active and passive depolarization methods exist such as the use of polarization scrambler or
a serial set of circulating couplers. Coherence control shall be applied to the TLS in order to
prevent coherence interference effects during the measurement.
For Method B, C and D, the measurement results shall be the averaged A(λ) and RL(λ) as a
function of the state of polarization (SOP). This is particularly critical because these methods
use narrowband polarized light sources and as such the test results may be obtained at
different unknown SOP after the DUT.
The following are two approaches for obtaining the averaged value of A(λ) and RL(λ):
• Direct approach. A depolarizer based on active or passive device is connected at the
output port of the source in order to reduce its degree of polarization (DOP). This allows
the direct measurement of the averaged A(λ) and RL(λ) as a function of the state of
polarization (SOP).
• Indirect approach. The measurement of A(λ) and RL(λ) as a function of the state of
polarization (SOP) and to obtain the average value of A(λ) and RL(λ) from the
measurement results.
5.2 Detection system
The following subclauses describe the various options for the detection system in relation with
the methods described above.
5.2.1 Method A, Method B.2 and Method C.2 tuneable narrowband detection spectrum
The TND typically uses an OSA measuring the output optical power at every wavelength over
the specified wavelength range and with a resolution bandwidth (RBW). The RBW is specified
at –3 dB and is a spectral characteristic of the filtering design used in an OSA. The RBW may
be variable but shall be specified in accordance with the required DUT bandwidth and fulfilling
the Nyquist criterion. In order to avoid false interpretation of detectable artefacts in the
measured DUT spectral response, the optical rejection ratio (ORR) shall be specified at a
certain wavelength difference from the centre wavelength. An example of such specification
could be –20 dB at 0,1 nm away from the centre wavelength; other values may be specified
such as –30 dB at 0,2 nm away from the centre wavelength, better defining the required
spectral response of the filter used in the OSA. If a global assessment of the OSA RBW
performance is desired, the overall filter shape response of the OSA may be required. This is
typically achieved by comparing the envelope of a DFB against one obtained from a high-
resolution interferometer.
The power dynamic range and sensitivity shall be high enough for A and RL to be measured
in accordance with the DUT specification. The amplitude uncertainty due to polarization
dependance of the OSA shall be less than desired uncertainty of A (λ) to be measured.
DUT
Where, during the sequence of measurements, an OSA is disconnected and reconnected, the
coupling efficiency for the two measurements shall be maintained.
5.2.2 Method B.1 and Method C.1 broadband detection spectrum
The BBD consists of an optical detector, the associated electronics and means for connecting
to the DUT. The optical connection may be a receptacle for an optical connector, a fibre
pigtail or a bare fibre adapter.
The BBD wavelength range shall be wide enough and power sensitivity high enough for A(λ)
and RL(λ) to be measured. The BBD response shall be linear. Since all of the measurements
are differential, it is however not necessary that the calibration be absolute. Care should be
taken to suppress the reflected power and minimize polarization sensitivity from the BBD
during the measurement.
Where, during the sequence of measurements, the BBD is disconnected and reconnected, the
coupling efficiency for the two measurements shall be maintained. Use of a large area
detector to capture all of the light emanating from the DUT is recommended.
5.3 Branching devices
The branching devices (BD) are used in order to branch the DUT to the source and the
detection system in pigtailed or connectorized configuration depending on their individual
connection design.
BD configurations may be 1X1 connector jumper (also called patchcord), splice, bare-fibre
adaptor, vacuum chuck or micro manipulator. Another configuration may also be a 2X1
coupler used for RL (λ) measurements.
DUT
BD splitting ratio shall be stable and uniform with wavelength. The amplitude uncertainty due
to PDL of the BD shall be less than desired uncertainty of A (λ) to be measured. A (λ)
DUT BD
shall be low enough to allow the minimum RL (λ) to be measured. RL (λ) should be at
DUT BD
least 20 dB higher than the maximum RL (λ) to be measured. The directivity should be at
DUT
least 10 dB higher than the maximum RL (λ) to be measured.
DUT
– 16 – IEC 61300-3-7:2009 IEC 2009
BD shall be selected in accordance with the DUT detail specifications.
Where, during the sequence of measurements, BD is disconnected and reconnected, the
coupling efficiency for the two measurements shall be maintained.
5.4 Termination
Table A.1 in Annex A illustrates a number of DUT configurations for terminations.
Terminations (RL ) shall have a high RL. Three RL types may be considered:
∞ ∞
• angled fibre ends such as the use of angled-polished connector (APC);
• application of an index matching material to the fibre end;
• sufficient fibre attenuation, for example with a mandrel wrap.
RL∞ shall have an RL at least 20 dB greater than the maximum RL (λ) to be measured.
DUT
Reference plugs with pigtails, and as required, reference adaptos, shall be added to the DUT
ports with connector terminations so as to form complete connector assemblies with pigtails.
6 Procedure
The methods herein described are intended to define procedures from which A(λ) and RL(λ)
can be derived.
In each of the following methods, it may be possible to improve the measurement accuracy by
using variants of the basic methods. Phase-sensitive detection of a mechanically modulated
source is an example of an improved test set-up when high loss components are to be
characterized.
Also, power fluctuation of the optical source can be monitored over time and used to
systematically adjust the DUT spectral response, using the terminated output port of the RBD.
NOTE The measurement precision is dependent on the DUT PDL and on the detection system when a Method B
or Method C is used.
6.1 Method A – broadband light source
6.1.1 Attenuation-only
6.1.1.1 Reference measurement
Connect BBS to TND as shown in Figure 2a. Depending on DUT configuration, the connection
may be either direct or with an adaptor. If possible, direct connection should be preferred as it
is less uncertain.
ref
Following Figure 2a, measure and record optical output power levels P (λ ) over the
t
wavelength range.
BBS TND
BD
ref
P (λ) (λ)
P
i
i
Adaptor
BBS
TND
BD BD
IEC 2335/08
Figure 2a – Attenuation reference measurement
BBS
TND
DUT
BD
P (λ) P (λ)
i t
BBS TND
DUT
BD BD
IEC 2336/08
Figure 2b – Attenuation measurement
Figure 2 – Method A – Attenuation-only measurement
6.1.1.2 Attenuation measurement
Insert the DUT as shown in Figure 2b; measure and record optical output power levels P (λ )
t
over the wavelength range.
Calculate A(λ)as follows:
ref
P (λ) P (λ)
t t
A(λ)=−10× log − log [dB] (3)
P (λ) P (λ)
i i
6.1.1.3 Bidirectional measurement
Invert the DUT in order to perform a bidirectional measurement and the measurements taken
in both directions should be averaged. No averag
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