IEC 61290-1-1:2020

IEC 61290-1-1 ®
Edition 4.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical amplifiers – Test methods –
Part 1-1: Power and gain parameters – Optical spectrum analyzer method

Amplificateurs optiques – Méthodes d'essai –
Partie 1-1: Paramètres de puissance et de gain – Méthode de l'analyseur de
spectre optique
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et
les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and once 67 000 electrotechnical terminology entries in English and
a month by email. French extracted from the Terms and Definitions clause of IEC
publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or need CISPR.

further assistance, please contact the Customer Service

Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - Le premier dictionnaire d'électrotechnologie en ligne au monde,
webstore.iec.ch/advsearchform avec plus de 22 000 articles terminologiques en anglais et en
La recherche avancée permet de trouver des publications IEC français, ainsi que les termes équivalents dans 16 langues
en utilisant différents critères (numéro de référence, texte, additionnelles. Egalement appelé Vocabulaire
comité d’études,…). Elle donne aussi des informations sur les Electrotechnique International (IEV) en ligne.

projets et les publications remplacées ou retirées.
Glossaire IEC - std.iec.ch/glossary
IEC Just Published - webstore.iec.ch/justpublished 67 000 entrées terminologiques électrotechniques, en anglais
Restez informé sur les nouvelles publications IEC. Just et en français, extraites des articles Termes et Définitions des
Published détaille les nouvelles publications parues. publications IEC parues depuis 2002. Plus certaines entrées
Disponible en ligne et une fois par mois par email. antérieures extraites des publications des CE 37, 77, 86 et
CISPR de l'IEC.
Service Clients - webstore.iec.ch/csc
Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
Electropedia - www.electropedia.org

IEC 61290-1-1 ®
Edition 4.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical amplifiers – Test methods –

Part 1-1: Power and gain parameters – Optical spectrum analyzer method

Amplificateurs optiques – Méthodes d'essai –

Partie 1-1: Paramètres de puissance et de gain – Méthode de l'analyseur de

spectre optique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.30 ISBN 978-2-8322-8749-1

– 2 – IEC 61290-1-1:2020 © IEC 2020
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions, and abbreviated terms . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms . 6
4 Apparatus . 6
4.1 Test setup . 6
4.2 Characteristics of test equipment . 9
5 Test sample . 11
6 Procedure . 11
6.1 Gain and nominal output signal power . 11
6.2 PDG variation . 12
6.3 Maximum output signal power . 12
6.4 Maximum total output power . 12
6.5 Gain ripple . 12
6.5.1 General . 12
6.5.2 Method 1 – Signal gain method . 13
6.5.3 Method 2 – ASE method . 13
6.6 Detail requirements of apparatus . 14
7 Calculation . 14
7.1 Nominal output signal power . 14
7.2 Gain . 14
7.3 Polarization-dependent gain. 14
7.4 Maximum output signal power . 15
7.5 Maximum total output power . 15
7.6 Gain ripple . 15
7.6.1 Method 1 – Signal gain test method . 15
7.6.2 Method 2 – ASE method . 16
8 Test results . 17
Bibliography . 19

Figure 1 – Typical arrangement of optical spectrum analyzer test apparatus for gain
and power measurements . 7
Figure 2 – Typical arrangement of optical spectrum analyzer test apparatus for gain
ripple measurements . 8
Figure 3 – Example of gain ripple spectrum with the signal gain method . 16
Figure 4 – Example of gain ripple spectrum with ASE method . 17

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL AMPLIFIERS – TEST METHODS –

Part 1-1: Power and gain parameters –
Optical 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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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 61290-1-1 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
This fourth edition cancels and replaces the third edition published in 2015 and constitutes a
technical revision.
This edition includes the following significant technical change with respect to the previous
edition: addition of techniques to test gain ripple of SOAs.
The text of this International Standard is based on the following documents:
FDIS Report on voting
86C/1673/FDIS 86C/1687/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.

– 4 – IEC 61290-1-1:2020 © IEC 2020
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
This document is to be used in conjunction with IEC 61290-1 and IEC 61291-1.
A list of all parts of the 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 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.
OPTICAL AMPLIFIERS – TEST METHODS –

Part 1-1: Power and gain parameters –
Optical spectrum analyzer method

1 Scope
This part of IEC 61290 applies to all commercially available optical amplifiers (OAs) and
optically amplified modules. It applies to OAs using optical fibre amplifiers (OFAs) based on
either rare-earth doped fibres or on the Raman effect, semiconductor OAs (SOAs) and planar
optical waveguide amplifiers (POWAs).
The object of this document is to establish uniform requirements for accurate and reliable
measurements, by means of the optical spectrum analyzer (OSA) test method, of the following
OA parameters, as defined in IEC 61291-1:
a) nominal output signal power;
b) gain;
c) polarization-dependent gain (PDG);
d) maximum output signal power;
e) maximum total output power.
In addition, this document provides the test method of:
f) gain ripple (for SOAs).
NOTE All numerical values followed by (‡) are suggested values for which the measurement is assured.
The object of this document is specifically directed to single-channel amplifiers. Test methods
for multichannel amplifiers are standardized in IEC 61290-10 (all parts) [1] .
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 60793-2-50, Optical fibres – Part 2-50: Product specifications – Sectional specification for
class B single-mode fibres
IEC 61290-1, Optical amplifiers – Test methods – Part 1: Power and gain parameters
IEC 61291-1, Optical amplifiers – Part 1: Generic specification
___________
Numbers in square brackets refer to the Bibliography.

– 6 – IEC 61290-1-1:2020 © IEC 2020
3 Terms, definitions, and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61291-1 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
ASE amplified spontaneous emission
DBR distributed Bragg reflector (laser diode)
DFB distributed feed-back (laser diode)
ECL external cavity laser (diode)
LED light emitting diode
OA optical amplifier
OFA optical fibre amplifier
OSA optical spectrum analyzer
PDG polarization-dependent gain
POWA planar optical waveguide amplifier
SOA semiconductor optical amplifier
4 Apparatus
4.1 Test setup
A diagram of the test set-up for gain and power measurements is given in Figure 1, showing
the set-up for calibration in Figure 1 a), the set-up for input signal power measurement in
Figure 1 b), and the set-up for output power measurement in Figure 1 c).
The test set-up for gain ripple measurements is displayed in Figure 2, showing the set-up for
calibration in Figure 2 a), the set-up for input signal power measurement in Figure 2 b), and two
different set-ups for gain ripple measurement in Figure 2 c) and Figure 2 d).

a) – Calibration
b) – Input signal power measurement

c) – Output power measurement
Key
J1, J2 optical connector
Figure 1 – Typical arrangement of optical spectrum
analyzer test apparatus for gain and power measurements

– 8 – IEC 61290-1-1:2020 © IEC 2020

a) – Calibration
b) – Input signal power measurement

c) – Gain ripple measurement (signal gain method)

d) – Gain ripple measurement (ASE method)
Key
J1, J2 optical connector
Figure 2 – Typical arrangement of optical spectrum
analyzer test apparatus for gain ripple measurements

4.2 Characteristics of test equipment
The test equipment listed below, with the required characteristics, is needed.
a) Optical source
The optical source shall be either fixed wavelength or wavelength-tuneable.
– Fixed-wavelength optical source
This optical source shall generate light with a wavelength and optical power specified in
the product specification or equivalent. Unless otherwise specified, the optical source
shall emit a continuous wave with the full width at half maximum of the spectrum
narrower than 1 nm (‡). A distributed feed-back (DFB) laser, a distributed Bragg reflector
(DBR) laser, an external cavity laser (ECL) diode and a light emitting diode (LED) with
a narrow-band filter are applicable, for example. The suppression ratio for the side
modes for the DFB laser, the DBR laser, or the ECL shall be higher than 30 dB (‡). The
output power fluctuation shall be less than 0,05 dB (‡), which may be better attainable
with an optical isolator at the output port of the optical source. Spectral broadening at
the foot of the lasing spectrum shall be minimal for laser sources, and the ratio of the
source power to total spontaneous emission power of the laser shall be more than 30 dB.
– Wavelength-tuneable optical source
This optical source shall be able to generate wavelength-tuneable light within the range
specified in the product specification or equivalent. Its optical power shall be specified
in the product specification or equivalent. Unless otherwise specified, the optical source
shall emit a continuous wave with the full width at half maximum of the spectrum
narrower than 1 nm (‡). An ECL or an LED with a narrow bandpass optical filter is
applicable, for example. The suppression ratio of side modes for the ECL shall be higher
than 30 dB (‡). The output power fluctuation shall be less than 0,05 dB, which may be
more easily attainable with an optical isolator at the output port of the optical source.
Spectral broadening at the foot of the lasing spectrum shall be minimal for the ECL.
Spectral broadening at the foot of the lasing spectrum shall be minimal for laser sources,
and the ratio of the source power to total spontaneous emission power of the laser shall
be more than 30 dB.
– Narrow band wavelength-tuneable optical source
This optical source shall be able to generate wavelength-tuneable light within the range
specified in the product specification or equivalent. Its optical power shall be specified
in the product specification or equivalent. Unless otherwise specified, the optical source
shall emit a continuous wave with the full width at half maximum of the spectrum
narrower (for example, one tenth) than the gain ripple period to be measured. An ECL
or an LED with a narrow bandpass optical filter is applicable, for example. The
suppression ratio of side modes for the ECL shall be higher than 30 dB (‡). The output
power fluctuation shall be less than 0,05 dB, which may be more easily attainable with
an optical isolator at the output port of the optical source. Spectral broadening at the
foot of the lasing spectrum shall be minimal for the ECL. Spectral broadening at the foot
of the lasing spectrum shall be minimal for laser sources, and the ratio of the source
power to total spontaneous emission power of the laser shall be more than 30 dB.
The use of an LED shall be limited to small-signal gain measurements.
b) Optical power meter
It shall have a measurement uncertainty less than 0,2 dB, irrespective of the state of
polarization, within the operational wavelength bandwidth of the OA. A dynamic range 10 dB
higher than the measured gain shall be required (e.g. 40 dB).
c) Optical spectrum analyzer (OSA)
Within the operational wavelength bandwidth of the OA, the linearity of the spectral power
measurement shall be less than the desired gain uncertainty and at most 0,5 dB, and the
amplitude stability of the spectral power measurement shall be less than the desired power
uncertainty and at least less than 0,4 dB over the duration of the measurement. Polarization
dependence of the spectral power measurement shall be less than 1,0 dB. The wavelength
measurement uncertainty shall be less than 0,5 nm. A dynamic range 10 dB higher than the

– 10 – IEC 61290-1-1:2020 © IEC 2020
measured gain shall be required (e.g. 40 dB). The spectral resolution shall be equal or less
than 1 nm.
The amplifier stability is the maximum degree of amplitude fluctuation expressed by the ratio
of the maximum and minimum optical power over the duration of the measurement.
d) Optical isolator
Optical isolators may be used to bracket the OA. The polarization-dependent loss variation
of the isolator shall be less than 0,2 dB (‡). Small wavelength dependent loss is
recommended. Optical isolation shall be more than 40 dB (‡). The reflectance from this
device shall be smaller than –40 dB (‡) at each port.
e) Variable optical attenuator
The attenuation range and stability shall be over 40 dB (‡) and less than 0,2 dB (‡),
respectively. The reflectance from this device shall be smaller than −40 dB (‡) at each port.
The attenuation stability is the maximum degree of attenuation fluctuation expressed by the
ratio of the maximum and minimum optical attenuation over the duration of the measurement
after setting a certain attenuation setpoint.
f) Polarization controller
This device shall be able to provide as input signal light all possible states of polarization
(e.g. linear, elliptical and circular). For example, the polarization controller may consist of a
linear polarizer followed by an all-fibre-type polarization controller or by a linear polarizer
followed by a quarter-wave plate rotatable by minimum of 90° and a half wave plate rotatable
by minimum of 180°. The loss variation of the polarization controller shall be less than 0,2 dB
(‡). The reflectance from this device shall be smaller than −40 dB (‡) at each port. The use
of a polarization controller is considered optional, except for the measurement of PDG, but
may also be necessary to achieve the desired uncertainty of other power and gain
parameters for OA devices exhibiting significant PDG.
g) Optical fibre jumpers
The optical fibre jumpers shall be of the same fibre category defined in IEC 60793-2-50 as
the fibres used as input and output ports of the OA, so that the mode field diameters of the
optical fibre jumpers closely match those of the input and output fibres of the OA. The
reflectance from this device shall be smaller than −40 dB (‡) at each port, and the length of
the jumper shall be shorter than 2 m. Polarization maintaining fibre shall be used for the
input fibre jumper when testing gain ripple in an SOA, if the gain ripple of the SOA is
sensitive to the state of polarization.
h) Optical connectors, J1 and J2
The connection loss repeatability shall be less than 0,4 dB. The repeatability of the
connection loss, ΔL is defined as the range of 3σ of the distribution of measured values
expressed in Formula (1):
(dB) (1)
ΔL= 3σ
where σ is the standard deviation of the measurements calculated by Formula (2):
m

σ Lj−L
( )
(dB) (2)
∑

m
j=1
where
m is the number of measurements;
L(j) is the measurement value of the connector loss;
L is the mean value of the measurement value of the connector loss.
A minimum of ten times (m = 10) is recommended to provide a reasonable estimate of σ.
=
i) Analyzer
This device shall be able to provide linear polarized light from the power emitted from the
DUT and adjust to an arbitrary polarization axis. The polarization extinction ratio shall be
more than 20 dB.
j) Non-reflective terminator
A non-reflective terminator shall be used for the ASE method of gain ripple measurement
when the SOA module does not have an isolator at the input side. The reflectance from this
device shall be smaller than −40 dB (‡) at each port.
5 Test sample
The OA under test shall operate at nominal operating conditions. If the OA is likely to cause
laser oscillations due to unwanted reflections, optical isolators shall be used to bracket the OA
under test. This will reduce signal instability and measurement uncertainty.
Except for the SOA, standard optical fibres type B-652.B or B-652.D, as defined in
IEC 60793-2-50, are recommended. However, other fibre types may be used as input/output
fibre. If fibre types other than B-652.B or B-652.D are used as input/output fibre, the mode field
diameter of the optical fibre jumpers shall closely match those of the input and output fibres of
the OA (see 4.2 g)). For measurements of the parameters of Clause 1, care shall be taken to
maintain the state of polarization of the input light during the measurement. Changes in the
polarization state of the input light can result in input optical power changes because of the
slight polarization dependency expected from all the optical components used, thus leading to
increased measurement uncertainty.
6 Procedure
6.1 Gain and nominal output signal power
This method permits the determination of gain through measurements of OA input signal power,
P , OA output power, P , and OA amplified spontaneous emission (ASE) power, P , at the
in out ASE
signal wavelength. The measurement procedures described below shall be followed:
a) set the optical source to the test wavelength specified in the product specification or
equivalent; set the optical source and the variable optical attenuator in such a way as to
provide, at the input port of the OA, the optical power P specified in the product
in
specification or equivalent;
b) measure P with the optical power meter, as shown in Figure 1 a), to calibrate the OSA;
in
c) measure P with the OSA, as shown in Figure 1 b);
in
d) measure P with the OSA, as shown in Figure 1 c);
out
e) measure P with the OSA, as shown in Figure 1 c), according to the technique specified
ASE
in the product specification or equivalent.
In cases using a polarization controller, the following procedure shall be used:
f) measure P by adjusting the polarization controller until a minimum P is achieved and
out out
repeat step e).
Various techniques for P measurements are applicable. One technique makes use of an
ASE
interpolation procedure to evaluate the ASE level at the signal wavelength by measuring the
ASE level at the wavelength offset to both sides of the signal wavelength on the OSA display.
Another technique employs a polarizer, placed between the variable optical attenuator and the
OA under test, to eliminate the signal component from the OA output to measure the ASE level
without being affected by the amplified signal spectrum. In the latter case, the input optical
signal shall be linearly polarized with an extinction ratio more than 30 dB (‡), and P shall be
out
– 12 – IEC 61290-1-1:2020 © IEC 2020
calculated as an average value over all the polarization states. If the polarizer technique cannot
sufficiently eliminate the signal power, the interpolation technique can be used in addition to
the polarizer technique.
Optical connectors J1 and J2 shall not be disconnected during the measurement except
between measurement steps c) and d) to avail measurement uncertainty due to reconnection.
6.2 PDG variation
As in 6.1, but use a polarization controller between the variable optical attenuator and the
connector J1 (see Figure 1), repeat all procedures at different states of polarization as specified
in the product specification or equivalent, and replace procedure a) with the following:
a) set the optical source to the test wavelength specified in the product specification or
equivalent; set the polarization controller to a given state of polarization as specified in the
product specification or equivalent; set the optical source and the variable optical attenuator
in such a way as to provide, at the input port of the OA, the optical power P specified in
in
the product specification or equivalent.
6.3 Maximum output signal power
As in 6.1, but this parameter is determined by repeating all steps at different wavelengths
specified in detailed specification, and replace steps a), d), and f) with the following:
a) set the wavelength-tuneable optical source to the test wavelength specified in the product
specification or equivalent; set the optical source and the variable optical attenuator in such
a way as to provide, at the input port of the OA, the maximum input optical power P
in max
specified in the product specification or equivalent;
d) activate the OA and adjust the maximum pump power or maximum pump current of the OA
to the nominal condition as specified in the product specification or equivalent; when the
OA under test is integrated with control circuitry, the OA shall be tested with constant pump
power mode or constant pump current mode and measure P with the OSA, as shown in
out
Figure 1 c);
f) measure maximum output signal power by adjusting the polarization controller until a
maximum P is achieved and repeat step e) in 6.1.
out
6.4 Maximum total output power
Same procedure as for 6.3.
The state of polarization of the input signal shall be changed after each measurement of P ,
in
P , and P by means of the polarization controller, so that substantially all the states of
out ASE
polarization, in principle, are successively launched into the input port of the OA under test.
6.5 Gain ripple
6.5.1 General
This document provides two test methods for measuring the gain ripple of SOAs:
– method 1 – signal gain method;
– method 2 – ASE method.
The signal gain method is the way to measure the gain spectrum directly under the condition of
an actual signal input, whereas the ASE method is the way to measure the ASE spectrum
without any input signal. It should be noted that the gain ripple result in an SOA that is measured
by the ASE method is theoretically equal to that which is measured by the signal gain method
only in the case when the gain in the medium is considered to be uniform throughout the gain
medium. High input power or high bias current could lead to inaccurate results.

To measure the gain ripple, both methods can be done under a small signal condition. In
addition, the signal gain method is sensitive to a stability of wavelength and power of the input
signal. On the other hand, the bias condition of SOAs should be carefully chosen in the ASE
method, because high bias conditions may lead to gain non-uniformity.
6.5.2 Method 1 – Signal gain method
This method permits determination of the gain ripple through the measurements of the OA input
signal power, P , the OA output power, P , and the OA amplified spontaneous emission (ASE)
in out
power, P , at the signal wavelength. The measurement procedures described below shall
ASE
be followed:
a) set the optical source to the test wavelength specified in the product specification or
equivalent;
b) set the variable optical attenuator in a such a way as to provide, at the input port of the
OA, optical power P less than −20 dBm (‡);
in
c) measure P by adjusting the polarization controller until a maximum P is achieved and
out out
repeat step b).
d) measure P with the optical power meter, as shown in Figure 2 a), to calibrate the OSA;
in
e) measure P with the OSA, as shown in Figure 2 b);
in
f) measure P with the OSA, as shown in Figure 2 c);
out
g) measure P with the OSA, as shown in Figure 2 c), according to the technique specified
ASE
in the product specification or equivalent.
Various techniques for P measurements are applicable. One technique makes use of an
ASE
interpolation procedure to evaluate the ASE level at the signal wavelength by measuring the
ASE level at wavelengths that are offset in both directions from the signal wavelength on
the OSA display. Another technique employs a polarizer, placed between the variable optical
attenuator and the OA under test, to eliminate the signal component from the OA output to
measure the ASE level without being affected by the amplified signal spectrum. In the latter
case, the input optical signal shall be linearly polarized with an extinction ratio better than
30 dB (‡). If the polarizer technique cannot sufficiently eliminate the signal power, the
interpolation technique may be used in addition to the polarizer technique.
Optical connectors J1 and J2 shall not be disconnected during the measurement except
between measurement steps e) and f) to avail measurement uncertainty due to reconnection.

6.5.3 Method 2 – ASE method
a) Set the operating injection current to the value specified in the product specification or
equivalent.
b) Measure P with the OSA, as shown in Figure 2 d).
ASE
If the analyzer is used, procedures c) and d) shall be followed:
c) set the polarization controller to a given state of polarization as specified in the product
specification or equivalent;
d) change the state of polarization of the input signal by means of the polarization controller
and repeat procedure b).
The wavelength resolution of the OSA should be at least 1/10 of the ripple period to be
measured.
– 14 – IEC 61290-1-1:2020 © IEC 2020
6.6 Detail requirements of apparatus
The polarization controller shall be operated as specified in the product specification or
equivalent. A possible way, when using a linear polarizer followed by a quarter-wave rotatable
plate, is the following: the linear polarizer is adjusted so that the OA output power is maximized;
the quarter-wave plate is then rotated by a minimum of 90° continuously. At each step, the half-
wave plate is rotated by a minimum of 180°, step-by-step. Another possible way is to select four
known and specified states of polarization to allow matrix calculation of the resulting PDG.
A short optical jumper at the OA input, kept as straight as possible, shall be used in order to
minimize the change of the state of polarization induced in it by possible stress and anisotropy.
The polarization-dependent loss variation of the optical connector shall be less than 0,2 dB (‡).
7 Calculation
7.1 Nominal output signal power
The nominal output signal power P (in dBm) shall be calculated as in Formula (3):
sig-out-nom
P = 10 log (P – P ) + L (dBm) (3)
sig-out-nom 10 out ASE bj
where
P is the recorded absolute value of output optical signal power (in mW);
out
P is the recorded absolute value of output ASE power through the optical bandpass filter

ASE
(in mW);
L is the insertion loss of the fibre jumper placed between the OA and the optical power
bj
meter (in dB).
NOTE The measurement uncertainty can be less than 1,5 dB (‡), depending on the OSA uncertainty.
7.2 Gain
The gain G at the signal wavelength shall be calculated as in Formula (4):
[(P – P ) / P ] (dB) (4)
G = 10 log
10 out ASE in
NOTE 1 The small-signal regime is a range of input signal power sufficiently small so that the OA under test
operates in the linear regime. This regime can be established by plotting G versus P . The linear regime demands
in
to be in a range where the gain is quite independent from P . An input signal power ranging from −30 dBm to
P
in in
−40 dBm generally is well within this range.
NOTE 2 The measurement uncertainty can be less than 1,5 dB (‡), depending on the OSA uncertainty, mainly in
terms of its polarization dependency. If linearly polarized light (i.e. light generated by a laser) and a polarization
controller are used, the measurement uncertainty can be much reduced by adjusting the state of polarization of the
input signal to the OA so that the OSA always indicates the minimum (or maximum) signal power in each
measurement. On the other hand, an LED and a monochromator can be used as an optical source to reduce the OSA
uncertainty to 0,2 dB, since LEDs emit unpolarized light. However, it is to be noted that the optical power level
obtainable from such a source is much lower than that of a laser.
7.3 Polarization-dependent gain
Calculate the gain values at the different states of polarization, as in 7.2. Identify the maximum,
G , and the minimum, G , gain as the highest and the lowest of all these gain values,
max-pol min-pol
respectively. The PDG variation ∆G shall be calculated as in Formula (5):
p
∆G = G – G (dB) (5)
p max-pol min-pol
NOTE 1 ∆G does not necessarily indicate the possible maximum variation of the polarization dependency. In fact,
p
the evolution of the state of polarization inside the OA depends on temperature and other parameters, and the
attenuation through the OA under test is maximum only when each input state of polarization simultaneously yields
maximum attenuation for each component in the OA under test.
NOTE 2 The measurement uncertainty can be less than 1 dB (‡), depending on the OSA uncertainty, mainly in
terms of its polarization dependency.
7.4 Maximum output signal power
The maximum output signal power P (in dBm) shall be calculated as in Formula (6):
sig-out-max
linear
P = 10 log ( P – P ) (dBm) (6)
sig-out-max 10 out-max ASE
where
linear
P is the recorded absolute maximum value of output optical power (in mW).
out-max
7.5 Maximum total output power
The maximum total output power P (in dBm) shall be calculated as in Formula (7):
out-max
linear
P = 10 log ( P ) (dBm) (7)
out-max 10 out-max
where
linear
P is the recorded absolute maximum value of output optical power (in mW).
out-max
7.6 Gain ripple
7.6.1 Method 1 – Signal gain test method
Calculate the gain values at the specified wavelength range, as in 7.2. The gain ripple is the
maximum difference in gain between adjacent peaks and valleys in the specified wavelength
range (see Figure 3).
– 16 – IEC 61290-1-1:2020 © IEC 2020

Figure 3 – Example of gain ripple spectrum with the signal gain method
Ripples in the gain spectrum (gain ripples) can be expressed as in Formula (8) (ΔG (λ), j-th
j
gain peak channel, j = 1, 2, . . . n; n total number of gain peak):
ΔG (λ)= G (λ) – G (λ) (8)
j j-peak j-valley
The gain ripple ΔG (λ) is defined as in Formula (9) and is expressed in dB:
ripple
ΔG (λ) = MAX {ΔG (λ)} (9)
ripple j j
7.6.2 Method 2 – ASE method
The gain ripple is the maximum difference in power between adjacent peaks and valleys in a
specified wavelength range (see Figure 4).

Figure 4 – Example of gain ripple spectrum with ASE method
Multiple gain ripple can be expressed as in Formula (10) (ΔP (λ), j-th ASE power peak channel,
j
j = 1, 2, . . . n; n total number of gain peak):
ΔP (λ) = P (λ) – P (λ) (10)
j j-peak j-valley
where
P (λ) is the optical power at j-th ASE power peak channel (in dBm);
j-peak
P (λ) is the optical power at adjacent valleys to j-th ASE power peak channel (in dBm).
j-valley
The gain ripple ΔG (λ) is defined as in Formula (11) and is expressed in dB:
ripple
ΔG (λ) = MAX {ΔP (λ)} (11)
ripple j j
NOTE Gain ripple in an SOA is uncertain in cases where the gain in the medium is non-uniform. Therefore, high
input power could be a factor leading to uncertain results.
8 Test results
The following test setting conditions shall be recorded.
a) Nominal output signal power
The following details shall be presented:

– 18 – IEC 61290-1-1:2020 © IEC 2020
1) arrangement of the test set-up;
2) type of optical source;
3) indication of the optical pump power (if applicable);
4) ambient temperature (when required);
5) case temperature (when required);
6) input signal optical power, P ;
in
7) resolution bandwidth of the OSA;
8) wavelength of the measurement.
b) Gain
Details 1) to 8) listed for nominal output signal power shall be presented and, in addition:
1) gain.
c) Polarization-dependent gain (PDG)
Details 1) to 8) listed for nominal output signal power shall be presented and, in addition:
1) polarization dependency of optical power for the OSA;
2) the maximum and minimum gain, G and G
;
max-pol min-pol
3) PDG variation;
4) change in the state of polarization given to the input signal light.
d) Maximum output signal power
Details 1) to 8) listed for nominal output signal power shall be presented and, in addition:
1) maximum output signal power P .
sig-out-max
e) Maximum total output power:
Details 1) to 8), listed for nominal output signal power, shall be
...