Optical amplifiers - Part 3: Classification, characteristics and applications

IEC TR 61292-3:2020 which is a Technical Report, establishes the classification of optical amplifiers (OAs). It also includes a brief description of each amplifier, its general properties, performance, configurations and applications. This second edition cancels and replaces the first edition published in 2003. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:  
document architecture now focuses on EDFA, FRA and SOA;
the description of PDFA and TDFA has been moved to the annexes;
the EDWA description has been deleted;
information on single channel amplification, multi-channel amplification, configuration and control method for EDFA, FRA and SOA has been added;
information on future amplifiers, arrayed amplifiers and SDM amplifiers has been added.

General Information

Status
Published
Publication Date
24-Mar-2020
Current Stage
PPUB - Publication issued
Completion Date
25-Mar-2020
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IEC TR 61292-3
Edition 2.0 2020-03
TECHNICAL
REPORT
colour
inside
Optical amplifiers –
Part 3: Classification, characteristics and applications
IEC TR 61292-3:2020-03(en)
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IEC TR 61292-3
Edition 2.0 2020-03
TECHNICAL
REPORT
colour
inside
Optical amplifiers –
Part 3: Classification, characteristics and applications
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.10; 33.180.30 ISBN 978-2-8322-8014-0

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 61292-3:2020 © IEC:2020
CONTENTS

FOREWORD ........................................................................................................................... 4

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms, definitions and abbreviated terms ........................................................................ 6

3.1 Terms and definitions .............................................................................................. 6

3.2 Abbreviated terms ................................................................................................... 7

4 Classification ................................................................................................................... 8

4.1 Types of OA ............................................................................................................ 8

4.2 Amplification forms ............................................................................................... 10

4.2.1 Lumped (or discrete) amplification and distributed amplification ..................... 10

4.2.2 Single channel and multichannel amplification ............................................... 10

4.2.3 Fixed and variable gain amplification ............................................................. 10

4.3 Application of optical amplifiers ............................................................................. 11

5 General properties, performance and configurations ...................................................... 12

5.1 Erbium-doped fibre amplifiers (EDFAs) ................................................................. 12

5.1.1 General properties ......................................................................................... 12

5.1.2 Typical performance ...................................................................................... 13

5.1.3 Configurations ............................................................................................... 14

5.1.4 Control scheme ............................................................................................. 16

5.1.5 Product configurations and application .......................................................... 17

5.2 Fibre Raman amplifiers (FRAs) ............................................................................. 18

5.2.1 General properties ......................................................................................... 18

5.2.2 Typical performance ...................................................................................... 19

5.2.3 Configuration ................................................................................................. 20

5.2.4 Control scheme ............................................................................................. 20

5.2.5 Product configurations and application .......................................................... 20

5.3 Semiconductor amplifiers (SOAs).......................................................................... 20

5.3.1 General properties ......................................................................................... 20

5.3.2 Typical performance ...................................................................................... 21

5.3.3 Configurations ............................................................................................... 21

5.3.4 Product configurations and applications ......................................................... 22

Annex A (informative) Other rare earth-doped fibre amplifiers .............................................. 23

A.1 General ................................................................................................................. 23

A.2 Praseodymium-doped fibre amplifier (PDFA) ......................................................... 23

A.3 Thulium-doped fibre amplifier (TDFA) ................................................................... 24

Annex B (informative) SDM amplifiers .................................................................................. 26

Bibliography .......................................................................................................................... 27

Figure 1 – Classification of optical amplifiers .......................................................................... 9

Figure 2 – Amplification bandwidth of each type of amplifier ................................................. 10

Figure 3 – Application forms of optical amplifiers in an optical transmission system .............. 11

Figure 4 – Application forms of optical amplifiers in optical network (ROADM with

colourless, directionless and contention-less function and arrayed amplifier) ........................ 12

Figure 5 – Abridged and primary energy levels for erbium ion ............................................... 13

Figure 6 – Pumping configurations of optical fibre amplifier .................................................. 14

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IEC TR 61292-3:2020 © IEC:2020 – 3 –

Figure 7 – Core and cladding pumping configurations ........................................................... 15

Figure 8 – Configuration of ROPA ......................................................................................... 15

Figure 9 – Single stage and double stage configurations ...................................................... 16

Figure 10 – Control schemes of EDFA .................................................................................. 17

Figure 11 – Product configurations ....................................................................................... 18

Figure A.1 – Abridged and primary energy levels for praseodymium ion ................................ 23

Figure A.2 – Abridged and primary energy levels for thulium ion ........................................... 25

Figure B.1 – Space division multiplexing amplifiers ............................................................... 26

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– 4 – IEC TR 61292-3:2020 © IEC:2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL AMPLIFIERS –
Part 3: Classification, characteristics and applications
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international

co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and

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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.

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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

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any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.

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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.

The main task of IEC technical committees is to prepare International Standards. However, a

technical committee may propose the publication of a Technical Report when it has collected

data of a different kind from that which is normally published as an International Standard, for

example "state of the art".

IEC TR 61292-3, which is a technical report, 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. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) document architecture now focuses on EDFA, FRA and SOA;
b) the description of PDFA and TDFA has been moved to the annexes;
c) the EDWA description has been deleted;
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IEC TR 61292-3:2020 © IEC:2020 – 5 –

d) information on single channel amplification, multi-channel amplification, configuration and

control method for EDFA, FRA and SOA has been added;

e) information on future amplifiers, arrayed amplifiers and SDM amplifiers has been added.

The text of this document is based on the following documents:
Draft TR Report on voting
86C/1597/DTR 86C/1630/RVDTR

Full information on the voting for the approval of this document 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 61292 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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct understanding

of its contents. Users should therefore print this document using a colour printer.

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– 6 – IEC TR 61292-3:2020 © IEC:2020
OPTICAL AMPLIFIERS –
Part 3: Classification, characteristics and applications
1 Scope

This part of IEC 61292, which is a Technical Report, establishes the classification of optical

amplifiers (OAs). It also includes a brief description of each amplifier, its general properties,

performance, configurations and applications.
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 – Part 731: Optical fibre

communication (available at www.electropedia.org)
IEC 61291-1, Optical amplifiers – Part 1: Generic specification
IEC TR 61931, Fibre optic – Terminology
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-731,

IEC 61291-1, 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
3.1.1
erbium-doped fibre amplifier
EDFA

rare earth-doped fibre amplifier, where the core of the fibre is doped with erbium ions

3.1.2
semiconductor optical amplifier
SOA
optical amplifier that uses a semiconductor to provide the gain medium

Note 1 to entry: These amplifiers have a similar structure to Fabry-Pérot laser diodes but with anti-reflection design

elements at the end faces. The signal is amplified through the stimulated emission phenomenon of gain medium.

3.1.3
single channel amplifier
optical amplifier amplifying one signal
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IEC TR 61292-3:2020 © IEC:2020 – 7 –
3.1.4
multichannel amplifier
optical amplifier amplifying two or more signals whose wavelengths differ
3.1.5
remote optically pumped amplifier
ROPA

optical fibre amplifier in which pumping light(s) is transmitted remotely to active fibre through a

transmission fibre
3.1.6
space division multiplexing amplifier
SDM amplifier

optical fibre amplifier that uses space division multiplexing (SDM) transmission system

Note 1 to entry: There are two types of SDM amplifier: one is a multi-core fibre amplifier, and the other is a few-

mode fibre amplifier.
3.1.7
multi-core erbium-doped fibre amplifier
multi-core EDFA
space division multiplexing EDFA for multi-core transmission
3.1.8
few-mode erbium-doped fibre amplifier
few-mode EDFA
space division multiplexing EDFA for few-mode transmissions
3.1.9
arrayed amplifier

optical amplifier formed by arranging several semiconductor amplifiers and EDFAs in parallel

3.2 Abbreviated terms
ACC automatic current control
AGC automatic gain control
ALC automatic level control
APC automatic power control
ASE amplified spontaneous emission
DRA distributed Raman amplifier
EDF erbium-doped fibre
EDFA erbium-doped fibre amplifier
EDFFA erbium-doped fluoride fibre amplifier
EDSFA erbium-doped silica fibre amplifier (commonly known as EDFA)
EDTFA erbium-doped tellurite fibre amplifier
EDWA erbium-doped waveguide amplifier
EYDFA erbium ytterbium-doped fibre amplifier
EYDSFA erbium ytterbium-doped silica fibre amplifier (commonly known as EYDFA)
FMF few-mode fibre
FRA fibre Raman amplifier
GFF gain flattening filter
LD laser diode
MCF multi-core fibre
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– 8 – IEC TR 61292-3:2020 © IEC:2020
MQW multiple quantum well
NF noise figure
OA optical amplifier
OFA optical fibre amplifier
OSNR optical signal-to-noise ratio
OWGA optical waveguide amplifier
PD photo diode
PDFA praseodymium-doped fibre amplifier
PDFFA praseodymium-doped fluoride fibre amplifier (also known as PDFA)
PDG polarization-dependent gain
ROADM reconfigurable optical add/drop multiplexer
ROPA remote optically pumped amplifier
SDM space division multiplexing
SMF single-mode fibre
SOA semiconductor optical amplifier
TEC thermo-electric cooler
TDFA thulium-doped fibre amplifier
TDFFA thulium-doped fluoride fibre amplifier (also known as TDFA)
VOA variable optical attenuator
WDM wavelength division multiplexing
WSS wavelength selective switch
4 Classification
4.1 Types of OA

Figure 1 shows the classification of optical amplifiers. Optical amplifiers (OAs) are classified as

optical fibre amplifiers (OFAs), semiconductor amplifiers (SOAs) and others (e.g. optical wave

guide amplifiers (OWGA) such as Erbium doped waveguide amplifiers (EDWA)). Furthermore,

OFAs are classified as rare earth-doped optical fibre amplifiers and fibre Raman amplifiers

(FRAs), and rare earth-doped optical fibre amplifiers are classified as erbium-doped optical

fibre amplifiers (EDFAs) and rare earth-doped optical fibre amplifiers with alternative dopants.

From these various OAs, the OAs which are practically used are EDFAs, FRAs and SOAs.

General properties, performance and configurations of EDFAs, FRAs and SOAs are described

in Clause 5. OAs are also classified according to amplification form, application, etc., in addition

to those in Figure 1. The various amplification forms and the application of optical amplifiers

are explained in 4.2 and 4.3, respectively.
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IEC TR 61292-3:2020 © IEC:2020 – 9 –
Figure 1 – Classification of optical amplifiers

Rare earth-doped optical fibre amplifiers other than erbium-doped ones have also been

developed. Various rare earth-doped fibre amplifiers are often expressed as an abbreviation:

X-Y-DFA. "X" indicates the type of rare earth, i.e., E, T, P, and "Y" represent erbium, thulium,

praseodymium, and ytterbium, respectively. "Y" indicates the fibre type, i.e., S, F and T

represent silica fibre, fluoride fibre and tellurite fibre, respectively. So, EDSFA, which is

commonly known as EDFA, EDFFA and EDTFA indicate an erbium-doped silica fibre amplifier,

an erbium-doped fluoride fibre amplifier and an erbium-doped tellurite fibre amplifier,

1 2

respectively. When two kinds of rare earths are added, the notation X -X -Y-DFA is used. For

example, EYSDFA (commonly known as EYDFA) indicates an erbium ytterbium-doped silica

fibre amplifier. Although many rare earth-doped fibres have been developed, EDFA is the rare

earth-doped fibre that is generally commercialized today. In addition, EYDFA is described as

an EDFA that has high output characteristics in this classification. Furthermore, since

praseodymium-doped fluoride fibre amplifiers (PDFFA, also known as PDFA) and thulium-

doped fluoride fibre amplifiers (TDFFA, also known as TDFA) are used in special fields, they

are introduced in Annex A. Furthermore, Annex B introduces SDM amplifiers that have recently

appeared.

Figure 2 shows the amplification bandwidth of each type of amplifier. EDFA is used for

amplification of C-band (amplification bandwidth: approximately 30 nm) and L-band

(amplification bandwidth: approximately 30 nm) optical signals, and it is also applicable to

amplification of a part of the S-band (amplification bandwidth: approximately 20 nm) optical

signal. Rare earth-doped optical fibre amplifiers other than erbium-doped ones can achieve O-

band, S-band and U-band amplification by using praseodymium and thulium as the dopant.

NOTE Spectral bands of O-band, S-band, C-band, L-band and U-band are defined in ITU-T G.Sup39.

FRAs and SOAs can realize amplification in the required band over the whole wavelength region

by selecting the wavelength of the pump source and semiconductor composition. The

amplification bandwidth of FRAs and SOAs is about 100 nm.
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– 10 – IEC TR 61292-3:2020 © IEC:2020
Figure 2 – Amplification bandwidth of each type of amplifier
4.2 Amplification forms
4.2.1 Lumped (or discrete) amplification and distributed amplification

In a transmission system, there are two amplification types: lumped (or discrete) amplification,

which performs optical amplification between transmission fibres, and distributed amplification,

which uses the transmission fibre itself as the amplification medium. EDFAs, other rare earth-

doped optical fibre amplifiers and SOAs are applied to the former, and FRAs are used for both

applications. However, an FRA is used as a distributed Raman amplifier (DRA) rather than a

lumped (or discrete) amplifier because of its advantages and drawbacks. In addition,

amplification in which an EDFA and Raman are combined is also applied in the system.

4.2.2 Single channel and multichannel amplification

OAs are classified according to the number of signals to be amplified with a single channel

amplifier and a multichannel amplifier. The single channel amplifier amplifies only one signal,

and the multichannel amplifier amplifies two or more signals whose wavelengths differ (that is,

the WDM signal). EDFAs, other rare earth-doped optical fibre amplifiers and FRAs are applied

as both amplifiers, and SOAs are generally used as single channel amplifiers due to the four

wave-mixing effect.
4.2.3 Fixed and variable gain amplification

Normally, since the gain characteristic of an OA is fixed, it may be called a fixed gain type OA.

However, depending on the application, the OA may change its gain characteristics as

necessary, and it may be called a variable gain type OA. An EDFA that can operate variable

gain functions (this may be called a variable gain EDFA or gain switchable EDFA) can be

achieved by changing EDF length that is used in the EDFA, or by using a multistage

configuration (see 5.1.3.3).
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IEC TR 61292-3:2020 © IEC:2020 – 11 –
4.3 Application of optical amplifiers

There are three application forms of the lumped amplifier for use in a transmission system:

booster, repeater (sometimes called line amplifier) and preamplifier, as shown in Figure 3 a).

The booster amplifies a transmitted signal that is sent out to a transmission fibre. The repeater

enlarges the signal intensity that became weak by fibre transmission and sends it out to the

next transmission fibre. The preamplifier is installed in front of a receiver and amplifies the

signal that became weak by transmission to a receiving level. When distributing a signal to two

or more receiving points, the power amplifier acts as one of the lumped amplifiers and is

installed in front of a branching point, as shown in Figure 3 b).
a) Booster amplifier, repeater (line) amplifier and preamplifier
b) Power amplifier

Figure 3 – Application forms of optical amplifiers in an optical transmission system

Recently, reconfigurable optical add/drop multiplexer (ROADM) technology for combining

wavelength multiplexing and path management technology and successfully operating the ultra-

high-speed/large-capacity optical network requires colourless, directionless and contention-

less function. Details of ROADM are in IEC TR 62343-6-4.

To realize the function, it is necessary to construct a ROADM using a multi-port wavelength

selective switch (WSS) and a multi-cast switch, as shown in Figure 4.

An arrayed amplifier, which is formed by arranging several semiconductor amplifiers and EDFAs

in parallel, is used for loss compensation of WSS and multicast switches. The performance

specification template of the multicast switch is standardized in IEC 62343-3-4.
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– 12 – IEC TR 61292-3:2020 © IEC:2020

Figure 4 – Application forms of optical amplifiers in optical network (ROADM with

colourless, directionless and contention-less function and arrayed amplifier)
5 General properties, performance and configurations
5.1 Erbium-doped fibre amplifiers (EDFAs)
5.1.1 General properties

The concept of the optical fibre amplifier was proposed by Dr Snitzer in 1961. The EDFA

concept was first demonstrated in 1985. Just when conventional un-repeated systems were

approaching their peak performance, a research group at the University of Southampton

showed that optical fibres could exhibit optical gain at wavelengths near 1 550 nm. These fibres

were doped with a rare earth element, erbium, and were activated or pumped with low powers

of visible light. EDFAs have since attracted considerable attention in the field of optical fibre

communications because they conveniently operate in the preferred, i.e. low-loss,

telecommunications spectral window at around 1 550 nm. EDFAs are the most widely used

optical amplifiers today.

An EDFA can be optically pumped at several wavelengths, with optimum performances

achieved at wavelengths of 980 nm and 1 480 nm. They provide gain at wavelengths from

approximately 1 520 nm to 1 625 nm.

In its most basic configuration, a typical EDFA consists of a section of single-mode erbium-

doped fibre, a pump laser, a WDM coupler for combining the signal and the pump power into

the erbium fibre, input and output isolators and tap couplers and control electronics, as

described in IEC TR 61292-1.

There are many energy levels for the erbium ion. However, only a small set of these energy

levels is of interest to optical amplification in telecommunication systems. These include the

ground state and a few of the lowest level states. The higher energy states represent transitions

in the visible and ultra-violet part of the spectrum, and these states are essentially unoccupied

in EDFA applications. Figure 5 shows the abridged energy levels for EDFAs and primary energy

levels used in EDFAs.
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IEC TR 61292-3:2020 © IEC:2020 – 13 –
Figure 5 – Abridged and primary energy levels for erbium ion

EDFAs have been shown to exhibit low polarization-sensitive gain, immunity to inter-channel

cross-talk, a high saturation output power and low noise close to the quantum limit. EDFAs can

simultaneously amplify weak signals at wavelengths across the operating range of 1 520 nm to

1 625 nm. This operating range varies with amplifier design, but this capability is crucial for

wavelength division multiplexing (WDM). EDFAs provide all optical amplification in the 1 550-

nm region, where
...

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