IEC 61291-1:2018
(Main)Optical amplifiers - Part 1: Generic specification
Optical amplifiers - Part 1: Generic specification
IEC 61291-1:2018 applies to all commercially available optical amplifiers (OAs) and optically amplified assemblies. It applies to OAs using optically pumped fibres (OFAs based either on rare-earth doped fibres or on the Raman effect), semiconductors (SOAs), and waveguides (POWAs). The object of this document is
- to establish uniform requirements for transmission, operation, reliability and environmental properties of OAs, and
- to provide assistance to the purchaser in the selection of consistently high-quality OA products for his particular applications.
Parameters specified for OAs are those characterizing the transmission, operation, reliability and environmental properties of the OA seen as a "black box" from a general point of view. In the sectional and detail specifications a subset of these parameters will be specified according to the type and application of the particular OA device or assembly. This fourth edition cancels and replaces the third edition published in 2012. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- terms have been added for parameters from IEC 61290-4-3 and IEC 61290-10-5;
- Clause 4 Classification has been removed, since this system is judged to be unused;
- the definition of polarization mode dispersion (PMD) has been simplified.
Keywords: optical amplifiers (OAs)
Amplificateurs optiques - Partie 1: Spécification générique
IEC 61291-1:2018 s’applique à tous les amplificateurs optiques (OA) et systèmes à amplification optique, disponibles sur le marché. Elle s’applique aux OA utilisant des fibres pompées optiquement (OFA basés sur des fibres dopées aux terres rares ou sur l’effet Raman), des semiconducteurs (SOA) et des guides d’ondes (POWA). Le présent document a pour objet
- d’établir des exigences uniformes pour la transmission, le fonctionnement, la fiabilité et les propriétés liées à l'environnement des OA, et
- d’aider les acheteurs à sélectionner des produits OA de qualité élevée et constante pour leurs applications.
Les paramètres spécifiés pour un OA sont ceux qui caractérisent les propriétés de transmission, de fonctionnement, de fiabilité et d’environnement de l’OA, considéré globalement comme une "boîte noire". Dans les spécifications intermédiaires et particulières, un sous-ensemble de ces paramètres sera spécifié d’après le type et l’application d’un module OA ou d’un système d’OA particulier. Cette quatrième édition annule et remplace la troisième édition parue en 2012. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- des termes ont été ajoutés pour des paramètres de l'IEC 61290-4-3 et de l'IEC 61290-10-5;
- la classification de l'Article 4 a été retirée car elle n'est pas utilisée;
- la définition de la dispersion du mode de polarisation a été simplifiée.
Mots clés: amplificateurs optiques (OA)
General Information
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Standards Content (Sample)
IEC 61291-1 ®
Edition 4.0 2018-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical amplifiers –
Part 1: Generic specification
Amplificateurs optiques –
Partie 1: Spécification générique
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IEC 61291-1 ®
Edition 4.0 2018-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Optical amplifiers –
Part 1: Generic specification
Amplificateurs optiques –
Partie 1: Spécification générique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.30 ISBN 978-2-8322-5404-2
– 2 – IEC 61291-1:2018 © IEC 2018
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and abbreviated terms . 6
3.1 Overview. 6
3.2 Terms and definitions . 8
3.2.1 OA devices and distributed amplifiers . 9
3.2.2 OA assemblies . 23
3.3 Abbreviated terms . 26
4 Requirements . 26
4.1 Preferred values . 27
4.2 Sampling. 27
4.3 Product identification for storage and shipping . 27
4.3.1 Marking . 27
4.3.2 Labelling . 27
4.3.3 Packaging. 27
5 Quality assessment . 27
6 Electromagnetic compatibility (EMC) requirements . 27
7 Test methods . 27
Bibliography . 29
Figure 1 – OA device and assemblies . 7
Figure 2 – Optical amplifier in a multichannel application . 8
Table 1 – Grouping of parameters and corresponding test methods or references . 28
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL AMPLIFIERS –
Part 1: Generic specification
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
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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
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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
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services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
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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 61291-1 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 2012. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) terms have been added for parameters from IEC 61290-4-3 and IEC 61290-10-5;
b) Clause 4 Classification has been removed, since this system is judged to be unused;
c) the definition of polarization mode dispersion (PMD) has been simplified.
– 4 – IEC 61291-1:2018 © IEC 2018
The text of this International Standard is based on the following documents:
CDV Report on voting
86C/1460/CDV 86C/1498/RVC
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.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61291 series, published under the general title Optical amplifiers,
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 –
Part 1: Generic specification
1 Scope
This part of IEC 61291 applies to all commercially available optical amplifiers (OAs) and
optically amplified assemblies. It applies to OAs using optically pumped fibres (OFAs based
either on rare-earth doped fibres or on the Raman effect), semiconductors (SOAs), and
waveguides (POWAs).
The object of this document is
– to establish uniform requirements for transmission, operation, reliability and environmental
properties of OAs, and
– to provide assistance to the purchaser in the selection of consistently high-quality OA
products for his particular applications.
Parameters specified for OAs are those characterizing the transmission, operation, reliability
and environmental properties of the OA seen as a "black box" from a general point of view. In
the sectional and detail specifications a subset of these parameters will be specified
according to the type and application of the particular OA device or assembly.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60050-731, International Electrotechnical Vocabulary – Chapter 731: Optical fibre
communication (available at http://www.electropedia.org)
IEC 61290 (all parts), Optical amplifiers – Test methods
IEC 61290-1-1, Optical amplifiers – Test methods – Part 1-1: Power and gain parameters –
Optical spectrum analyzer method
IEC 61290-1-2, Optical amplifiers – Test methods – Part 1-2: Power and gain parameters –
Electrical spectrum analyzer method
IEC 61290-1-3, Optical amplifiers – Test methods – Part 1-3: Power and gain parameters –
Optical power meter method
IEC 61290-3-1, Optical amplifiers – Test methods – Part 3-1: Noise figure parameters –
Optical spectrum analyzer method
IEC 61290-3-2, Optical amplifiers – Test methods – Part 3-2: Noise figure parameters –
Electrical spectrum analyzer method
IEC 61290-4-1, Optical amplifiers – Test methods – Part 4-1: Gain transient parameters –
Two wavelength method
– 6 – IEC 61291-1:2018 © IEC 2018
IEC 61290-4-2, Optical amplifiers – Test methods – Part 4-2: Gain transient parameters –
Broadband source method
IEC 61290-4-3, Optical amplifiers – Test methods – Part 4-3: Power transient parameters –
Single channel optical amplifiers in output power control
IEC 61290-5-1, Optical amplifiers – Test methods – Part 5-1: Reflectance parameters –
Optical spectrum analyzer method
IEC 61290-5-2, Optical amplifiers – Test methods – Part 5-2: Reflectance parameters –
Electrical spectrum analyzer method
IEC 61290-5-3, Optical fibre amplifiers – Basic specification– Part 5-3: Test methods for
reflectance parameters – Reflectance tolerance using an electrical spectrum analyzer
IEC 61290-6-1, Optical fibre amplifiers – Basic specification – Part 6-1: Test methods for
pump leakage parameters – Optical demultiplexer
IEC 61290-7-1, Optical amplifiers – Test methods – Part 7-1: Out-of-band insertion losses –
Filtered optical power meter method
IEC 61290-10-1, Optical amplifiers – Test methods – Part 10-1: Multichannel parameters –
Pulse method using an optical switch and optical spectrum analyzer
IEC 61290-10-2, Optical amplifiers – Test methods – Part 10-2: Multichannel parameters –
Pulse method using a gated optical spectrum analyzer
IEC 61290-10-3, Optical amplifiers – Test methods – Part 10-3: Multichannel parameters –
Probe methods
IEC 61290-10-4, Optical amplifiers – Test methods – Part 10-4: Multichannel parameters –
Interpolated source subtraction method using an optical spectrum analyzer
IEC 61290-10-5, Optical amplifiers – Test methods – Part 10-5: Multichannel parameters –
Distributed Raman amplifier gain and noise figure
IEC 61290-11-1, Optical amplifiers – Test methods – Part 11-1: Polarization mode dispersion
parameter – Jones matrix eigenanalysis (JME)
IEC 61290-11-2, Optical amplifiers – Test methods – Part 11-2: Polarization mode dispersion
parameter – Poincaré sphere analysis method
IEC 61291-5-2, Optical amplifiers – Part 5-2: Qualification specifications – Reliability
qualification for optical fibre amplifiers
IEC TR 61931, Fibre optic – Terminology
3 Terms, definitions and abbreviated terms
3.1 Overview
The definitions listed in 3.2 refer to the meaning of the terms used in the specifications of
OAs. Only those parameters listed in the appropriate specification template, as in
IEC 61291-2 and IEC 61291-4, are intended to be specified.
The list of parameter definitions of OAs, given in 3.2, is divided into two parts: the first part,
3.2.1, lists those parameters relevant for OA devices, namely power, pre-, line- and
distributed amplifiers; the second part, 3.2.2, lists the parameters relevant for optically
amplified, elementary assemblies, namely the optically amplified transmitter (OAT) and the
optically amplified receiver (OAR).
In any case where the value of a parameter is given for a particular device, it will be
necessary to specify certain appropriate operating conditions such as temperature, bias
current, pump optical power. In Clause 3, two different operating conditions are referred to:
nominal operating conditions, which are those suggested by the manufacturer for normal use
of the OA, and limit operating conditions, in which all the parameters adjustable by the user
(e.g. temperature, gain, pump laser injection current) are at their maximum values, according
to the absolute maximum ratings stated by the manufacturer.
The OA shall be considered as a "black box", as shown in Figure 1. The OA device shall have
two optical ports, namely an input and an output port (Figure 1 a)). The OAT and OAR shall
be considered as an OA integrated on the transmitter side or on the receiver side,
respectively. Both kinds of integration imply that the connection between the transmitter or the
receiver and the OA is proprietary and not to be specified. Consequently, only the optical
output port can be defined for the OAT [after the OA, as shown in Figure 1 b)] and only the
optical input port can be defined for the OAR [before the OA, as shown in Figure 1 c)]. The
optical ports may consist of unterminated fibres or optical connectors. Electrical connections
for power supply (not shown in Figure 1) are also necessary. Following this "black box"
approach, the typical loss of one connection and the corresponding uncertainty will be
included within the values of gain, noise figure and other parameters of the OA device.
NOTE 1 For distributed amplifiers, as described in Clause 4, this black-box configuration can be simulated for test
purposes, for example by attaching a reference fibre to test a Raman pump unit.
Input Output Output Input
Tx
OA
OA OA Rx
port port port
port
IEC
IEC
IEC
a) – OA device b) – OAT c) – OAR
Figure 1 – OA device and assemblies
The OA amplifies signals in a nominal operating wavelength region. In addition, other signals
outside of the band of operating wavelength can in some applications, also cross the OA. The
purpose of these out-of-band signals and their wavelength, or wavelength region, can be
specified in the detail specifications.
When signals at multiple wavelengths are incident on the OA, as is the case in multichannel
systems, suitable adjustment of the definitions of some existing relevant parameters is
needed together with the introduction of definitions of new parameters relevant to this
different application.
A typical configuration of an OA in a multichannel application is shown in Figure 2. At the
transmitting side, m signals, coming from m optical transmitters, Tx , Tx , . . . Tx , each with a
1 2 m
unique wavelength, λ , λ , . . . λ , respectively, are combined by an optical multiplexer (OM).
1 2 m
At the receiving side, the m signals at λ , λ , . . . λ , are separated with an optical
1 2 m
demultiplexer (OD) and routed to separate optical receivers, Rx , Rx , . . . Rx , respectively.
1 2 m
To characterize the OA in this multichannel application, an input reference plane and an
output reference plane are defined at the OA input and output ports, respectively, as shown in
Figure 2.
– 8 – IEC 61291-1:2018 © IEC 2018
Input Output
Tx Rx
reference
1 reference 1
plane
plane
Rx
Tx
2 2
OM OD
OA
P OA P
i1 o1
P P
i2 o2
. . . . . .
Tx Rx
P P
m m
im om
P (λ)
ASE
IEC
Figure 2 – Optical amplifier in a multichannel application
At the input reference plane, m input signals at the m wavelengths are considered, each with a
unique power level, P , P , . . . P , respectively. At the output reference plane, m output
i1 i2 im
signals at the m wavelengths, resulting from the optical amplification of the corresponding m
input signals, are considered, each with power level P , P , . . . P , respectively. Moreover,
o1 o2 om
the amplified spontaneous emission, ASE, with a noise power spectral density, P (λ), is
ASE
also to be considered at the OA output port.
Most definitions of relevant single-channel parameters can be suitably extended to
multichannel applications. When this extension is straightforward, the word "channel" will be
added to the pertinent parameter. In particular, the noise figure and the signal-spontaneous
noise figure may be extended to multichannel applications, channel by channel, by
(λ) at each channel wavelength and the channel signal
considering the value of P
ASE
bandwidth. For each channel wavelength there will be a unique value of noise figure that will
be a function of the input power level of all signals. In this case the parameters, channel noise
figure and channel signal-spontaneous noise figure, are introduced. However, some additional
parameters also need to be defined. For each parameter, the particular multichannel
configuration, including the full set of channel signal wavelengths and input powers, needs to
be specified.
The parameters defined in 3.2.1 will in general depend on temperature and polarization state
of input channels. The temperature and state of polarization should be kept constant or
controlled or be measured and reported together with the measured parameter.
NOTE 2 Except where noted, the optical powers mentioned in 3.2.1 are intended as average powers.
NOTE 3 The measured optical powers are open beam powers: this can result in differences of about 0,18 dB in
the measurement of absolute power levels.
NOTE 4 In the case of the distributed amplifier, all the parameters are related to a suitable reference fibre used to
emulate the transmission fibre in conjunction with the pumping assembly.
3.2 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-731 and
IEC TR 61931 and the following 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
3.2.1 OA devices and distributed amplifiers
NOTE The terms and definitions in 3.2.1 also apply, in general, to optical amplifiers under
IEC 61290 (all parts) and IEC 61291 (all parts).
3.2.1.1
gain
increase of signal optical power from the output end of the jumper fibre to the OA output port
in an OA which is externally connected to an input jumper fibre
Note 1 to entry: The gain includes the connection loss between the input jumper fibre and the OA input port.
Note 2 to entry: It is assumed that the jumper fibres are of the same type as the fibres used as input and output
port of the OA.
Note 3 to entry: Care should be taken to exclude the amplified spontaneous emission power from the signal
optical powers.
Note 4 to entry: Gain is expressed in dB.
3.2.1.2
small-signal gain
gain of the amplifier, when operated in linear regime, where it is essentially independent of
the input signal optical power, at a given signal wavelength and pump optical power level
Note 1 to entry: This property can be described at a discrete wavelength or as a function of wavelength.
3.2.1.3
reverse gain
gain measured using the input port of the OA as output port and vice versa
3.2.1.4
reverse small-signal gain
small-signal gain measured using the input port of the OA as output port and vice versa
3.2.1.5
maximum gain
highest gain that can be achieved when the OA is operated within the stated nominal
operating conditions
3.2.1.6
maximum small-signal gain
highest small-signal gain that can be achieved when the OA is operated within the stated
nominal operating conditions
3.2.1.7
maximum gain wavelength
wavelength at which the maximum gain occurs
3.2.1.8
maximum small-signal gain wavelength
wavelength at which the maximum small-signal gain occurs
3.2.1.9
gain wavelength variation
peak-to-peak variation of the gain over a given wavelength range
3.2.1.10
small-signal gain wavelength variation
peak-to-peak variation of the small-signal gain over a given wavelength range
– 10 – IEC 61291-1:2018 © IEC 2018
3.2.1.11
gain-slope under single wavelength operation
derivative of the gain of a small probe versus wavelength, at the
signal wavelength, in the presence of a signal of given wavelength and input power
Note 1 to entry: The probe total average power level shall be at least 20 dB below the input signal level, to
minimize the effect on the gain wavelength-profile.
3.2.1.12
polarization-dependent gain
PDG
the maximum variation of the OA gain due to a variation of the state of polarization of the
input signal, at nominal operating conditions
Note 1 to entry: A source of PDG in OAs is the polarization dependent loss of the passive components used
inside.
Note 2 to entry: This note applies to the French language only.
3.2.1.13
channel gain
gain for each channel (at wavelength λ) in a specified
j
multichannel configuration
Note 1 to entry: Channel gain, G , can be expressed as G = P – P , where P and P are respectively the input
j j oj ij ij oj
and output power levels, in dBm, of the j-th channel and j = 1, 2, … n; n total number of channels.
Note 2 to entry: Since the amplifier saturation power level is determined by the combined effect of the input
signals at all wavelengths, the channel gain is dependent on the input power level of all signals.
Note 3 to entry: Channel gain is expressed in dB.
3.2.1.14
multichannel gain variation
interchannel gain difference
difference between the channel gains of any two of the channels
in a specified multichannel configuration
Note 1 to entry: Multichannel gain variation can be expressed as ΔG = G – G , where G and G are respectively
jl j l j l
the channel gains of j-th and l-th channel and j, l = 1, 2, … n; j ≠ l; n total number of channels):
Note 2 to entry: Normally, this parameter is specified as the maximum multichannel gain variation, intended as
the maximum absolute value of multichannel gain variation, considering all possible combinations of channel pairs.
The input power levels would normally be set to their minimum and maximum specified values. Input power levels
may also be specified to achieve certain gain values or total output power levels. Maximum multichannel gain
variation can be expressed as ΔG = MAX {|ΔG |}.
MAX j,l jl
Note 3 to entry: Maximum multichannel gain variation is expressed in dB.
Note 4 to entry: This parameter is often referred to as "gain flatness".
3.2.1.15
gain cross-saturation
ratio of the change in channel gain of one channel, ΔG , to a
j
given change in the input power level of another channel, ΔP , while the input power levels of
l
all other channels are kept constant, in a specified multichannel configuration
Note 1 to entry: Gain cross-saturation can be expressed as follows (j, l = 1, 2, . . . , n; j ≠ l; n total number of
channels):
GXS = ΔG /ΔP
jl j l
Note 2 to entry: Gain cross-saturation is expressed in dB per dB.
Note 3 to entry: Normally, this parameter is specified for an initial input power distribution among channels in
which each channel is at the minimum allowed power level. Other distributions may be indicated in the appropriate
product specification.
3.2.1.16
multichannel gain-change difference
interchannel gain-change difference
difference of change in gain in one channel, for a specified
channel allocation, with respect to the change in gain of another channel for two specified
sets of channel input powers
(1) (2) (1) (2)
Note 1 to entry: Multichannel gain-change difference can be expressed as follows (G , G and G , G
j j l l
being the channel gains of the j-th and l-th channel at each of the two specified sets of channel input power (1) and
(2) respectively, and j, l = 1, 2, . . . n; n total number of channels):
(1) (2) (1) (2)
GD = [G – G ] – [G – G ]
jl j j l l
Note 2 to entry: Multichannel gain-change difference is expressed in dB.
Note 3 to entry: The two specified sets of channel input power are in general: (1) all input power levels set to the
minimum value and (2) all input power levels set to the maximum value.
Note 4 to entry: Normally, the maximum multichannel gain-change difference will be specified. Different sets of
input conditions could be defined in the appropriate product specification.
Note 5 to entry: Forward ASE power level can be relevant for OAs used as pre-amplifiers or line amplifiers. In this
case the channel input power will include the forward ASE contribution coming from previous OAs.
Note 6 to entry: This parameter can be used instead of the multichannel gain tilt when the definition of the gain tilt
cannot be applied.
3.2.1.17
multichannel gain tilt
interchannel gain-change ratio
dynamic gain tilt
DGT
ratio of the changes in gain in each channel to the change in
gain at a reference channel as the input conditions are varied from one set of input channel
powers to a second set of input channel powers
(1) (2) (1) (2)
Note 1 to entry Multichannel gain tilt can be expressed as follows (G , G and G , G being respectively
j j r r
the channel gains of the j-th and the reference channel at each of the two specified sets of channel input power
and j = 1, 2, . . . n; n total number of channels):
(1) (2) (1) (2)
GT = [G – G ] / [G – G ]
j j j r r
Note 2 to entry: Multichannel gain tilt is expressed in dB per dB.
Note 3 to entry: Multichannel gain tilt is normally used to predict the gains for each channel for various sets of
input channel powers based on observed changes in the reference channel.
Note 4 to entry: The sets of input channel powers are generally those in which (1) all power levels are set equal
to the maximum allowed and (2) all powers are set equal to the minimum allowed.
Note 5 to entry: The reference channel should be specified in the appropriate product specification. The
multichannel gain tilt of the reference channel is by definition equal to 1 dB/dB.
Note 6 to entry: Application of multichannel gain tilt to prediction of channel gain in different conditions could be
impaired in the case of hybrid multistage amplifiers, in homogeneous gain media and in particular for amplifiers
with automatic gain control.
Note 7 to entry: This note applies to the French language only.
– 12 – IEC 61291-1:2018 © IEC 2018
3.2.1.18
on-off gain
effective gain
increase in signal optical power from the output of
an optical fibre providing distributed amplification when the pumping is active compared to
when the pumping is disabled
Note 1 to entry: The on-off gain differs from gain in that it does not compare the output signal power with the
input signal power, since this includes the attenuation of the fibre and this loss can be associated with the
transmission system rather than the amplifier. The value for on-off gain is thus higher than for gain by the amount
of passive loss between the input and output.
Note 2 to entry: On-off gain is expressed in dB.
3.2.1.19
net on-off gain
increase in signal optical power from the output of
an optical fibre providing distributed amplification when the pumping is active compared to
when no additional fibre optic equipment is installed to the fibre for the purpose of providing
distributed amplification
3.2.1.20
wavelength band
wavelength range within which the OA output signal power is maintained in the specified
output power range, when the corresponding input signal power lies within the specified input
power range
3.2.1.21
available signal wavelength band
resulting pre-amplifier wavelength band including
the effect of optical filter(s)
3.2.1.22
tunable wavelength range
wavelength range, of the wavelength
band, within which the tuneable optical filter(s) inside the pre-amplifier can be tuned
3.2.1.23
channel allocation
channel allocation is given by the number of channels, the
nominal central frequencies/wavelengths of the channels and their central
frequency/wavelength tolerance
3.2.1.24
gain stability
degree of gain fluctuation expressed by the ratio of the maximum and minimum gain, for a
certain specified test period, under nominal operating conditions
Note 1 to entry: Gain stability is expressed in dB.
3.2.1.25
small-signal gain stability
degree of small-signal gain fluctuation expressed by the ratio of the maximum and minimum
small-signal gain, for a certain specified test period, under nominal operating conditions
Note 1 to entry: Small-signal gain stability is expressed in dB.
3.2.1.26
maximum gain variation with temperature
change in gain for temperature variation within a specified range
Note 1 to entry: Maximum gain variation with temperature is expressed in dB.
3.2.1.27
maximum small-signal gain variation with temperature
change in small-signal gain for temperature variation within a specified range
Note 1 to entry: Maximum small-signal gain variation with temperature is expressed in dB.
3.2.1.28
large-signal output stability
degree of output optical power fluctuation expressed by the ratio of the maximum and
minimum output signal optical powers, for a certain specified test period, under nominal
operating conditions and a specified large input signal optical power
Note 1 to entry: Large-signal output stability is expressed in dB.
3.2.1.29
saturation output power
gain compression power
optical power level associated with the output signal above which the gain is reduced by N dB
with respect to the small-signal gain at the signal wavelength
Note 1 to entry: The wavelength at which the parameter is specified should be stated.
Note 2 to entry: N = 3 is typically used.
3.2.1.30
nominal output signal power
minimum output signal optical power for a specified input signal optical power, under nominal
operating conditions
3.2.1.31
maximum output signal power
highest optical power associated with the output signal that can be obtained from the OA at
nominal operating conditions
3.2.1.32
input power range
range of optical power levels such that, for any input signal power of the OA which lies in this
range, the corresponding output signal optical power lies in the specified output power range,
where the OA performance is ensured
3.2.1.33
output power range
range of optical power levels in which the output signal optical power of the OA lies when the
corresponding input signal power lies in the specified input power range, where the OA
performance is ensured
3.2.1.34
noise figure
NF
decrease of the signal-to-noise ratio (SNR), at the output of an optical detector with unitary
quantum efficiency and zero excess noise, due to the propagation of a shot noise-limited
signal through the OA
Note 1 to entry: The operating conditions at which the noise figure is specified should be stated.
Note 2 to entry: This property can be described as a discrete wavelength or as a function of wavelength.
Note 3 to entry: The noise degradation due to the OA, is attributable to different factors, for example signal-
spontaneous beat noise, spontaneous-spontaneous beat noise, internal reflections noise, signal shot noise,
– 14 – IEC 61291-1:2018 © IEC 2018
spontaneous shot noise. Each of these factors depends on various conditions which should be specified for a
correct evaluation of the noise figure.
Note 4 to entry: By convention, this noise figure is a positive number.
Note 5 to entry: In the case of OAs for analogue applications, the noise figure also represents the ratio between
input and the output carrier-to-noise ratios.
Note 6 to entry: Noise figure is expressed in dB.
3.2.1.35
noise factor
F
noise figure expressed in linear form
3.2.1.36
channel noise figure
noise figure for each channel in a specified optical bandwidth,
for a specified multichannel configuration
Note 1 to entry: Channel noise figure is expressed in dB.
3.2.1.37
multi-path interference
MPI
figure of merit
noise factor contribution caused by multiple path interference integrated over all baseband
frequencies
Note 1 to entry: For example, multiple path interference can be caused by successive partial reflections in the
optical path.
Note 2 to entry: This note applies to the French language only.
3.2.1.38
double Rayleigh scattering figure of merit
noise factor contribution caused by multiple path interference due to Rayleigh scattering
integrated over all baseband frequencies
Note 1 to entry: Double Rayleigh scattering is particularly relevant to fibre Raman amplifiers, both distributed and
discrete, because of the long amplifying fibre lengths providing substantial amounts of scattered light together with
gain. Other fibre amplifiers with high gain and long fibres can also show this effect. The contribution becomes
larger at higher gain levels.
3.2.1.39
frequency-independent contribution to noise factor
noise factor excluding the noise contribution from multi-path interference
3.2.1.40
signal-spontaneous noise figure
NF
sig-sp
signal-spontaneous beat noise contribution to the noise figure
Note 1 to entry: Signal-spontaneous noise figure is expressed in dB.
3.2.1.41
channel signal-spontaneous noise figure
signal-spontaneous noise figure for each channel in a specified
multichannel configuration
Note 1 to entry: Channel signal-spontaneous noise figure is expressed in dB.
3.2.1.42
equivalent spontaneous-spontaneous optical bandwidth
B
sp-sp
equivalent optical bandwidth by which the square of the ASE spectral power density, ρ , at
ASE
the signal optical frequency, ν , is multiplied in order to obtain the integral of the squared
SIG
ASE spectral power density over the full ASE bandwidth, B , that is:
ASE
−2 2
B =ρ (ν )× ρ (ν)dν
sp−sp ASE sig ASE
∫
B
ASE
Note 1 to entry: The equivalent spontaneous-spontaneous optical bandwidth can be minimized by using an optical
filter at the output of the OA.
Note 2 to entry: This parameter is related to the spontaneous-spontaneous beat noise generation and thus it
requires the use of the squared ASE spectral power density.
3.2.1.43
equivalent total noise figure
decrease of the signal-to-noise ratio (SNR) at the
output of an optical detector with unitary quantum efficiency and zero excess noise, due to the
propagation of a shot-noise-limited signal through an optical fibre providing distributed
amplification when the pumping is active compared to when the pumping is disabled
Note 1 to entry: The effective noise figure differs from the noise figure in that it does not compare the SNR at the
output with the SNR at the input of the amplifier. The increase in signal strength relevant to the change in SNR is
thus the effective gain rather than the gain. In particular, the contribution of signal-spontaneous noise figure, which
can be calculated from the difference between ASE power and gain expressed in dB, is then reduced in the
effective noise figure by the amount of passive loss between the input and output. It is thus possible for the
effective noise figure of distributed amplification to be negative, expressed in dB.
Note 2 to entry: The effective noise figure can be understood as the noise figure of an equivalent discrete optical
amplifier placed at the end of the optical fibre, which produces the effective gain and the same ASE output power
as the distributed amplification. Because the ASE produced within the fibre of the distributed amplifier is also
partially reduced by the attenuation of this fibre, the ASE output power can be lower than physically realisable from
such a discrete amplifier.
Note 3 to entry: Equivalent total noise figure is expressed in dB.
3.2.1.44
equivalent signal-spontaneous noise figure
signal-spontaneous beat noise contribution to the
equivalent total noise figure
3.2.1.45
polarization mode dispersion
PMD
optical transmission property resultin
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