SIST EN 61290-3-2:2008

Optical amplifiers - Test methods - Part 3-2: Noise figure parameters - Electrical spectrum analyzer method (IEC 61290-3-2:2008)

This part of IEC 61290 applies to all commercially available optical amplifiers (OAs), including OAs using optically pumped fibres (OFAs based on either rare-earth doped fibres or on the Raman effect), semiconductor optical amplifiers (SOAs) and planar waveguide optical amplifiers (PWOAs). The object of this standard is to establish uniform requirements for accurate and reliable measurements, by means of the electrical spectrum analyzer (ESA) method, of the noise figure, as defined in IEC 61291-1. The present test method is based on direct electrical noise measurement and it is directly related to its definition including all relevant noise contributions. Therefore, this method can be used for all types of optical amplifiers, including SOA and Raman amplifiers which can have significant contributions besides amplified spontaneous emission, because it measures the total noise figure. For further details of applicability, see IEC 61290-3. An alternative test method based on the optical spectrum analyzer can be used, particularly for different noise parameters (such as the signal-spontaneous noise factor) but it is not included in the object of this standard.

Lichtwellenleiter-Verstärker - Prüfverfahren - Teil 3-2: Rauschzahlparameter - Verfahren mit elektrischem Spektralanalysator (IEC 61290-3-2:2008)

Amplificateurs optiques - Méthodes d'essais - Partie 3-2: Paramètres du facteur de bruit - Méthode de l'analyseur spectral électrique (IEC 61290-3-2:2008)

La CEI 61290-3-2:2008 s'applique aux amplificateurs à fibres optiques (AFO) qui utilisent des fibres actives, dopées aux terres rares, qui sont actuellement disponibles sur le marché. Etablit des prescriptions uniformes en vue de mesures précises et fiables du facteur de bruit défini en 3.1.17 de la CEI 61291-1, en utilisant la méthode d'essai d'analyseur de spectre électrique (ASE). Cette révision technique inclut des mises à jour permettant de s'adresser à tout type d'amplificateur optique - pas seulement les amplificateurs à fibres optiques. Il convient que la présente norme soit lue conjointement avec la CEI 61290-3 et la CEI 61291-1.

Optični ojačevalniki - Preskusne metode - 3-2. del: Parametri hrupa - Metoda analizatorja električnega spektra (IEC 61290-3-2:2008)

General Information

• Status: Published
• Publication Date: 26-Oct-2008
• ICS: 33.180.30 - Optic amplifiers
• Technical Committee: iTEL - Communication cables
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 22-Oct-2008
• Due Date: 27-Dec-2008
• Completion Date: 27-Oct-2008
• Ref Project: EN 61290-3-2:2008 - Optical amplifiers - Test methods - Part 3-2: Noise figure parameters - Electrical spectrum analyzer method

Relations

• Replaces: SIST EN 61290-3-2:2004 - Optical amplifiers -- Part 3-2: Test methods for noise figure parameters - Electrical spectrum analyzer method
• Effective Date: 01-Dec-2008
• Replaces: SIST EN 61290-3-2:2004 - Optical amplifiers -- Part 3-2: Test methods for noise figure parameters - Electrical spectrum analyzer method
• Effective Date: 28-Jan-2023
• Replaces: SIST EN 61290-3-2:2004 - Optical amplifiers -- Part 3-2: Test methods for noise figure parameters - Electrical spectrum analyzer method
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61290-3-2:2008
01-december-2008
1DGRPHãþD
SIST EN 61290-3-2:2004
2SWLþQLRMDþHYDOQLNL3UHVNXVQHPHWRGHGHO3DUDPHWULKUXSD0HWRGD
DQDOL]DWRUMDHOHNWULþQHJDVSHNWUD,(&
Optical amplifiers - Test methods - Part 3-2: Noise figure parameters - Electrical
spectrum analyzer method (IEC 61290-3-2:2008)
Lichtwellenleiter-Verstärker - Prüfverfahren - Teil 3-2: Rauschzahlparameter - Verfahren
mit elektrischem Spektralanalysator (IEC 61290-3-2:2008)
Amplificateurs optiques - Méthodes d'essais - Partie 3-2: Paramètres du facteur de bruit -
Méthode de l'analyseur spectral électrique (IEC 61290-3-2:2008)
Ta slovenski standard je istoveten z: EN 61290-3-2:2008
ICS:
33.180.30 2SWLþQLRMDþHYDOQLNL Optic amplifiers
SIST EN 61290-3-2:2008 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61290-3-2:2008

---------------------- Page: 2 ----------------------

SIST EN 61290-3-2:2008

EUROPEAN STANDARD
EN 61290-3-2

NORME EUROPÉENNE
October 2008
EUROPÄISCHE NORM

ICS 33.180.30 Supersedes EN 61290-3-2:2003


English version


Optical amplifiers -
Test methods -
Part 3-2: Noise figure parameters -
Electrical spectrum analyzer method
(IEC 61290-3-2:2008)


Amplificateurs optiques -  Lichtwellenleiter-Verstärker -
Méthodes d'essais - Prüfverfahren -
Partie 3-2: Paramètres du facteur de bruit - Teil 3-2: Rauschzahlparameter -
Méthode de l'analyseur spectral électrique Verfahren mit elektrischem
(CEI 61290-3-2:2008) Spektralanalysator
(IEC 61290-3-2:2008)




This European Standard was approved by CENELEC on 2008-10-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61290-3-2:2008 E

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SIST EN 61290-3-2:2008
EN 61290-3-2:2008 - 2 -
Foreword
The text of document 86C/784/CDV, future edition 2 of IEC 61290-3-2, prepared by SC 86C, Fibre optic
systems and active devices, of IEC TC 86, Fibre optics, was submitted to the IEC-CENELEC parallel vote
and was approved by CENELEC as EN 61290-3-2 on 2008-10-01.
This European Standard supersedes EN 61290-3-2:2003.
EN 61290-3-2:2008 includes updates to specifically address all types of optical amplifiers, not just optical
fibre amplifiers.
This standard is to be used in conjunction with EN 61290-3 and EN 61291-1.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2009-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2011-10-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61290-3-2:2008 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60793 NOTE  Harmonized in EN 60793 series (modified).
IEC 60825-1 NOTE  Harmonized as EN 60825-1:2007 (not modified).
IEC 60825-2 NOTE  Harmonized as EN 60825-2:2004 (not modified).
IEC 60874-1 NOTE  Harmonized as EN 60874-1:2007 (not modified).
__________

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SIST EN 61290-3-2:2008
- 3 - EN 61290-3-2:2008
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

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
document (including any amendments) applies.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.

Publication Year Title EN/HD Year

1) 2)
IEC 60728-6 - Cable networks for television signals, sound EN 60728-6 2003
signals and interactive services -
Part 6: Optical equipment


1) 2)
IEC 61290-3 - Optical amplifiers - Test methods - EN 61290-3 2008
Part 3: Noise figure parameters


1) 2)
IEC 61291-1 - Optical amplifiers - EN 61291-1 2006
Part 1: Generic specification



1)
Undated reference.
2)
Valid edition at date of issue.

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SIST EN 61290-3-2:2008

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SIST EN 61290-3-2:2008
IEC 61290-3-2
Edition 2.0 2008-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE


Optical amplifiers – Test methods –
Part 3-2: Noise figure parameters – Electrical spectrum analyzer method

Amplificateurs optiques – Méthodes d’essais -
Partie 3-2: Paramètres du facteur de bruit – Méthode de l’analyseur spectral
électrique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
Q
CODE PRIX
ICS 33.180.30 ISBN 2-8318-9898-6
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 61290-3-2:2008
– 2 – 61290-3-2 © IEC:2008
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope and object.6
2 Normative references .6
3 Symbols, acronyms and abbreviations.7
4 Apparatus.8
5 Test specimen .10
6 Procedure .10
6.1 Frequency-scanning technique: calibration.11
6.2 Frequency-scanning technique: measurement.12
6.3 Selected-frequency technique: calibration and measurement .13
6.4 Measurement accuracy limitations.13
7 Calculation .14
7.1 Calculation of calibration results.14
7.2 Calculation of test results for the frequency-scanning technique.15
7.3 Calculation of test results for the selected-frequency technique.15
8 Test results .16
Bibliography.17

Figure 1 – Scheme of a measurement set-up .9

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SIST EN 61290-3-2:2008
61290-3-2 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

OPTICAL AMPLIFIERS –
TEST METHODS –

Part 3-2: Noise figure parameters –
Electrical spectrum analyzer method


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 61290-3-2 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2003 and constitutes a
technical revision. It includes updates to specifically address all types of optical amplifiers –
not just optical fibre amplifiers.
This standard should be read in conjunction with IEC 61290-3 and IEC 61291-1.

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SIST EN 61290-3-2:2008
– 4 – 61290-3-2 © IEC:2008
The text of this standard is based on the following documents:
CDV Report on voting
86C/784/CDV 86C/828/RVC

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 61290 series, published under the general title Optical amplifiers –
Test methods, 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.

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SIST EN 61290-3-2:2008
61290-3-2 © IEC:2008 – 5 –
INTRODUCTION
This part of IEC 61290 is devoted to the subject of optical amplifiers. The technology of
optical amplifiers is still rapidly evolving, hence amendments and new additions to this
standard can be expected.
Each symbol and abbreviation introduced in this standard is generally explained in the text
the first time it appears. However, for an easier understanding of the whole text, a list of all
symbols and abbreviations used in this standard is given in Clause 3.

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SIST EN 61290-3-2:2008
– 6 – 61290-3-2 © IEC:2008
OPTICAL AMPLIFIERS –
TEST METHODS –

Part 3-2: Noise figure parameters –
Electrical spectrum analyzer method



1 Scope and object
This part of IEC 61290 applies to all commercially available optical amplifiers (OAs), including
OAs using optically pumped fibres (OFAs based on either rare-earth doped fibres or on the
Raman effect), semiconductor optical amplifiers (SOAs) and planar waveguide optical
amplifiers (PWOAs).
The object of this standard is to establish uniform requirements for accurate and reliable
measurements, by means of the electrical spectrum analyzer (ESA) method, of the noise
figure, as defined in IEC 61291-1.
The present test method is based on direct electrical noise measurement and it is directly
related to its definition including all relevant noise contributions. Therefore, this method can
be used for all types of optical amplifiers, including SOA and Raman amplifiers which can
have significant contributions besides amplified spontaneous emission, because it measures
the total noise figure. For further details of applicability, see IEC 61290-3. An alternative test
method based on the optical spectrum analyzer can be used, particularly for different noise
parameters (such as the signal-spontaneous noise factor) but it is not included in the object of
this standard.
NOTE 1 All numerical values followed by (‡) are suggested values for which the measurement is assured. Other
values may be acceptable but should be verified.
NOTE 2 A measurement accuracy for the average noise factor of ±20 %(‡), respectively ±1 dB, should be
attainable with this method (see Clause 6).
NOTE 3 General aspects of noise figure test methods are reported in IEC 61290-3.
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 document (including any amendments) applies.
IEC 60728-6, Cable networks for television signals, sound signals and interactive services –
Part 6: Optical equipment
IEC 61290-3: Optical fibre amplifiers – Basic specification – Part 3: Test methods for noise
1
figure parameters
IEC 61291-1, Optical amplifiers – Part 1: Generic specification
NOTE A list of informative references is given in the bibliography.
___________
1
 The first editions of some of these parts were published under the general title Optical fibre amplifiers – Basic
specification or Optical amplifiers – Test methods. Future editions of these parts will appear under the new
general title listed above. The individual titles of Parts 1-1, 3-1, 5-2, 10-1, 10-2, 10-3, 11-1 and 11-2 will be
updated in future editions of these parts to reflect the overall structure of the series.

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SIST EN 61290-3-2:2008
61290-3-2 © IEC:2008 – 7 –
3 Symbols, acronyms and abbreviations
For the purposes of this document, the following symbols, acronyms and abbreviations apply.
B calibrated, noise equivalent ESA electrical bandwidth (not necessarily the
e
resolution bandwidth)
c speed of light in vacuum
e electron charge
f baseband frequency
F (total) noise factor
F , frequency-independent contribution to total noise factor

non-mpi
F noise factor contribution from multiple path interference noise (OA internal

mpi
reflections)
G OA optical signal gain
h Planck's constant
k optical power reduction factor (default k = 0,5); it can be obtained by taking the
square root of the electrical power reduction factor
ν optical frequency = c/λ
Δν source FWHM linewidth with modulation on

2 –1
H , H (f) S /ΔP = transfer function of receiver in watts
0 0 esa in
I multi-path interference figure of merit, the noise factor contribution caused by
mpi
multiple path interference integrated over all baseband frequencies (0 to
infinity);
I photodetector current
pd
λ wavelength in vacuum
m relative modulation amplitude (the ratio of RMS optical power modulation
amplitude to average optical power)
NF(f) (total) noise figure
N (f) (frequency-dependent) ESA noise contribution caused by the laser relative
,
rin 0
intensity noise, at calibration conditions
N (frequency-dependent) noise caused by the laser relative intensity noise (RIN),
1
rin,
measured with ESA
N (frequency-independent) shot noise caused by the optical input power, at
,0
shot
calibration conditions, measured with ESA
 thermal noise level as measured with ESA (optical input port of receiver
N
thermal
module closed);
N (f) (frequency-dependent) noise power measured with ESA with input and output
0
attenuator set to 0 dB, thermal noise level subtracted, without OA test device
N '(f) (frequency-dependent) noise power measured with ESA with input attenuator
0
set to 3 dB (default) and output attenuator set to 0 dB, thermal noise level
subtracted, without OA test device
N (f) frequency-dependent noise power, with OA inserted, thermal noise level
1
subtracted, measured with ESA
P time-averaged optical input power = T P (with modulation on); optical
,
in in in 0
power radiated from the end of the input jumper cable
P time-averaged optical input power at 0 dB setting of input attenuator (with
,
in 0
modulation on)
ΔP RMS optical power amplitude
in, rms
P total optical power radiated from the output port of the OA, including the ASE
out

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SIST EN 61290-3-2:2008
– 8 – 61290-3-2 © IEC:2008
r , r (f) effective photodetector responsivity through output attenuator at 0 dB setting
0 0
RIN (f) source relative intensity noise; generally, the square of the RMS optical power
source
fluctuation divided by the (baseband) bandwidth and the square of the CW
power
S electrical power of the modulation signal at T = 1, measured with ESA,
0 in
without OA inserted
S electrical power of the modulation signal, with OA inserted, measured with ESA
1
T transmission factor of input attenuator relative to transmission at 0 dB setting,
in
expressed in linear form
T transmission factor of output attenuator relative to transmission at 0 dB setting,
out
expressed in linear form
T voltage amplification between detector output and ESA input; this quantity
x
usually depends on the baseband frequency
CW continuous wave
DFB distributed feedback laser
ESA electrical spectrum analyzer
FWHM full width at half maximum
MPI multiple path interference
OA optical fibre amplifier
–1
RIN relative intensity noise of the source, expressed in Hz
RMS root mean square
4 Apparatus
The scheme of a possible implementation of the measurement set-up is shown in Figure 1.
The test equipment listed below, with the required characteristics, is needed.
a) A source module with the following components
1) A laser source with a single-line spectrum, for example: a distributed feedback (DFB)
laser diode. The laser source shall be sine-wave amplitude modulated with one single
frequency that is sufficiently higher than the linewidth of the source. A modulation
frequency at least 3 times higher than the linewidth is advisable. The relative
modulation amplitude, m (that is, the ratio of root mean square, RMS, optical power
modulation amplitude to average optical power) shall be sufficiently small to ensure
operation in the linear regime. A value for m of 2 % to 10 %(‡) is considered adequate.
Direct or external modulation can be used.
An achievable average output power, P , of not less than 0 dBm is advisable, to be
,
in 0
able to generate the desired OA saturation state.
The linewidth FWHM (full width at half maximum) under modulation shall be between
20 MHz(‡) and 100 MHz(‡). This is considered the best range for accurate
determination of the noise contribution from multiple path interference, because it
closely reflects the typical linewidths of DFB lasers, the typical laser source used in
conjunction with OAs. A linewidth of 20 MHz is adequate for a minimum spacing of
7,5 m between the OA internal reflection points. Using narrower linewidths will lead to
the undesired situation that the OA internal reflections interfere in a coherent way and
that substantially different noise figure results are obtained. A linewidth of more than
100 MHz will cause OA noise contributions at frequencies which are higher than the
high end of the ESA bandwidth.
The relative intensity noise (RIN) of the laser source shall be less than –150 dB/Hz(‡)
within the frequency range of interest (for example, 10 MHz to 2 GHz).

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SIST EN 61290-3-2:2008
61290-3-2 © IEC:2008 – 9 –
The spontaneous emission power, relative to the signal power, shall be less than
–40 dB/nm(‡) in order to avoid large noise contributions from spontaneous-
spontaneous mixing of the source spontaneous emission.
2) A built-in or external isolator, so that external reflections have no influence on the
laser spectrum and on the laser relative intensity noise. The isolator shall have an
optical isolation of better than 60 dB(‡). The reflectance at the isolator output port
shall be less than –50 dB(‡).
3) An input attenuator with variable attenuation, >40 dB attenuation range, better than
±0,05 dB(‡) linearity and external/internal reflectances of less than –50 dB(‡). This
attenuator serves as means of changing the source output power without changing its
spectrum, relative intensity noise (RIN) or state of polarization. The purpose of this
attenuator is to control the input power and to allow a distinction of shot noise from
other noise sources during calibration.
NOTE Alternatively, a simpler attenuator with no linearity requirement can be used if the change of loss
is measured with the electrical spectrum analyzer.
4) A polarization controller with the following capabilities: generation of all possible
output polarization states from an arbitrary input polarization state, optical power
dependence on output polarization state less than ±0,01 dB(‡), and reflectances less
than –50 dB(‡).


DFB laser Electrical
Polarization
Optical
with spectrum
dB OA dB
controller
detector
isolator analyzer
Variable
Electrical
Optical filter
Variable
output
amplifier
OFA under (optional)
input attenuator
attenuator
test
Source module Receiver module
Possibly
Optical
separable
Modulation
power
source
meter
Power meter jumper cable
IEC  1187/08

Figure 1 – Scheme of a measurement set-up
b) A modulation source (that is, a signal generator) capable of generating the frequency and
amplitude stated above.
c) An optical power meter with the following capabilities:
− it shall be capable of measuring the total radiated power from the output connector (or
bare fibre) of the source module. It shall have a measurement accuracy of better than
±0,2 dB, irrespective of the state of polarization, within the operational wavelength
band of the OA. The minimum power level is defined by the source power at 0 dB
attenuator setting. The highest power level is given by the OA output power at the
highest input power;
− it is advisable to make the output port of the output attenuator accessible, because
then the OA output power can alternatively be measured through the output
attenuator, thereby reducing the need for high power measurement.
d) A receiver module with a noise equivalent power (in optical watts/hertz) not larger (‡) than
the RIN-related noise at the output of the source module at the input attenuator 0 dB
setting. The receiver module shall consist of the following components:

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SIST EN 61290-3-2:2008
– 10 – 61290-3-2 © IEC:2008
1) an output attenuator with variable attenuation, with attenuation range greater than
40 dB, linearity better than ±0,05 dB(‡), peak-to-peak polarization dependence better
than 0,05 dB(‡), essentially flat wavelength-response, external/internal reflectances of
less than –50 dB(‡), power level capabilities up to the maximum OA output power. The
purpose of this attenuator is to provide accurate attenuation before the detector input;
2) an O/E converter, preferably a combination of a photodetector with a reflectance of
less than –30 dB(‡) and a peak-to-peak polarization dependence better than
0,05 dB(‡), and an electrical amplifier with high-impedance input (to achieve low
thermal noise);
3) an electrical spectrum analyzer (ESA). It should have a frequency range in which any
multiple path interference (MPI) contribution to the noise figure is decayed to
insignificance. Usually, frequency ranges from 10 MHz to 2 GHz(‡) fulfill this
requirement. The ESA noise floor should be lower than the noise floor at the output of
the (electrical) amplifier when the source module is connected and the input attenuator
is set to 0 dB attenuation (in this case, the amplifier noise floor contains noise from
source RIN, detector shot noise and the electrical amplifier thermal noise).
e) Optical jumper cables with mode field diameters as close as possible to those of the fibres
used as input and output ports of the OA.
f) Optical connectors compatible with those used as optical input ports of the OA test device,
with a loss repeatability of better than ±0,1 dB. Their reflectance shall be less than
–50 dB(‡). Alternatively, optical splicing can be used as a method for connecting the OA to
the measurement set-up (this is considered the most accurate method).
g) Optionally, an optical filter to reduce/exclude the noise contribution from spontaneous-
spontaneous mixing from the measurement results. The filter shall have the following
properties: filter bandwidth sufficiently small to obtain the desired reduction of the
spontaneous-spontaneous noise, input and output reflectances less than −50 dB(‡), peak-
to-peak polarization dependence less than 0,05 dB(‡), stop-band attenuation greater than
30 dB.
5 Test specimen
The OA shall operate at nominal operating conditions. If the OA or the test apparatus is likely
to cause optical interference problems in the set-up, optical isolators should be used to
bracket the OA under test. This will minimize the signal instability and the measurement
uncertainty.
The OA optical ports may be optical connectors or bare fibre pigtails.
Care should be taken in maintaining the state of polarization of the input light during
measurement. Changes in the polarization state may result in changes of the optical input
power and in changes in the noise due to multiple path interference. Therefore, it is necessary
to adjust the input polarization state in order to maximize the noise figure.
6 Procedure
6.1 General remark
All signal and noise measurements with the electrical spectrum analyzer are in electrical
watts. All noise measurement results are to be understood as a function of frequency and
after subtraction of the (possibly frequency dependent) thermal noise (see 6.2, step i)).
Two alternative techniques are possible, namely the frequency-scanning technique and the
selected-frequency technique. The frequency-scanning technique is advisable when the
frequency-dependence of the noise produced by the OA is unknown or non-monotonic. The
selected-frequency technique may be used when t
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