Optical amplifiers - Part 1: Parameters of optical fibre amplifier components

IIEC TR 61292-1:2022 which is a Technical Report, applies to optical components of optical fibre amplifiers (OFAs). This document provides information about the most relevant parameters of these optical components, especially for erbium doped fibre amplifiers (EDFAs) and fibre Raman amplifiers (FRAs). It provides introductory information for a better understanding operation and applications of EDFAs and FRAs. NOTE IEC TR 61292-6 provides more technical information on FRAs. This third edition cancels and replaces the second edition published in 2009. This edition constitutes a technical revision.  This edition includes the following significant technical changes with respect to the previous edition:  
Change of document title from "Parameters of amplifier components" to "Parameters of optical fibre amplifier components";
Addition of parameters for optical components used in fibre Raman amplifiers;
Addition of Table 1, listing various documents that specify terms and definitions for optical components used in optical fibre amplifiers;
Addition of Figure 2 and Figure 3, showing typical component layouts for distributed and lumped fibre Raman amplifiers;
Harmonization of the descriptions of optical component parameters with the definitions in other standards on optical components.

General Information

Status
Published
Publication Date
10-May-2022
Current Stage
PPUB - Publication issued
Completion Date
11-May-2022
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IEC TR 61292-1
Edition 3.0 2022-05
TECHNICAL
REPORT
Optical amplifiers –
Part 1: Parameters of optical fibre amplifier components
IEC TR 61292-1:2022-05(en)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC TR 61292-1
Edition 3.0 2022-05
TECHNICAL
REPORT
Optical amplifiers –
Part 1: Parameters of optical fibre amplifier components
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.160.10; 33.180.30 ISBN 978-2-8322-0299-9

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 61292-1:2022 © IEC 2022
CONTENTS

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

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

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

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

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

3.1.1 Parameters for active fibres ............................................................................. 6

3.1.2 Parameters for pump lasers ............................................................................. 8

3.1.3 Parameters for WDM couplers ....................................................................... 11

3.1.4 Parameters for pump WDM couplers.............................................................. 12

3.1.5 Parameters for optical isolators ..................................................................... 12

3.1.6 Parameters for ASE rejection filters ............................................................... 14

3.1.7 Parameters for pump rejection filters ............................................................. 14

3.1.8 Parameters for gain flattening filters .............................................................. 15

3.1.9 Parameters for tap couplers ........................................................................... 16

3.1.10 Parameters for PIN-photodiodes .................................................................... 17

3.1.11 Parameters for variable optical attenuators (VOAs) ....................................... 18

3.1.12 Parameters for optical connectors ................................................................. 19

3.2 Abbreviated terms ................................................................................................. 19

3.3 Symbols ................................................................................................................ 20

4 OFA components ........................................................................................................... 21

5 Parameters of optical fibre amplifier components ........................................................... 24

5.1 Active fibre............................................................................................................ 24

5.1.1 Function and technical outline ....................................................................... 24

5.1.2 Parameters for active fibres ........................................................................... 24

5.2 Gain fibre for FRA ................................................................................................. 25

5.2.1 Function and technical outline ....................................................................... 25

5.2.2 Parameters for gain fibres of FRAs ................................................................ 25

5.3 Pump laser ........................................................................................................... 25

5.3.1 Function and technical outline ....................................................................... 25

5.3.2 Parameters for pump lasers ........................................................................... 25

5.4 WDM coupler (for combining signal light and pump light) ...................................... 26

5.4.1 Function and technical outline ....................................................................... 26

5.4.2 Parameters for WDM couplers ....................................................................... 26

5.5 Pump WDM coupler .............................................................................................. 26

5.5.1 Function and technical outline ....................................................................... 26

5.5.2 Parameters for pump WDM couplers.............................................................. 26

5.6 Polarization beam combiner (PBC) ....................................................................... 26

5.6.1 Function and technical outline ....................................................................... 26

5.6.2 Parameters for PBC ....................................................................................... 26

5.7 Optical isolator ...................................................................................................... 27

5.7.1 Function and technical outline ....................................................................... 27

5.7.2 Parameters for optical isolators ..................................................................... 27

5.8 ASE rejection filter ................................................................................................ 27

5.8.1 Function and technical outline ....................................................................... 27

5.8.2 Parameters for ASE rejection filters ............................................................... 27

5.9 Pump rejection filter .............................................................................................. 27

5.9.1 Function and technical outline ....................................................................... 27

---------------------- Page: 4 ----------------------
IEC TR 61292-1:2022 © IEC 2022 – 3 –

5.9.2 Parameters for pump rejection filter ............................................................... 27

5.10 Gain flattening filter (GFF) .................................................................................... 28

5.10.1 Function and technical outline ....................................................................... 28

5.10.2 Parameters for gain flattening filters .............................................................. 28

5.11 Tap coupler ........................................................................................................... 28

5.11.1 Function and technical outline ....................................................................... 28

5.11.2 Parameters for tap couplers ........................................................................... 28

5.12 PIN-photodiode (PIN-PD) ...................................................................................... 29

5.12.1 Function and technical outline ....................................................................... 29

5.12.2 Parameters for PIN-photodiodes .................................................................... 29

5.13 Variable optical attenuator (VOA) .......................................................................... 29

5.13.1 Function and technical outline ....................................................................... 29

5.13.2 Parameters for variable optical attenuators .................................................... 29

5.14 Optical connectors ................................................................................................ 29

5.14.1 Function and technical outline ....................................................................... 29

5.14.2 Parameters for optical connectors ................................................................. 30

Bibliography .......................................................................................................................... 31

Figure 1 – Example of the components inside an EDFA operating in a co-propagating

pumping scheme ................................................................................................................... 23

Figure 2 – Example of the component layout of a distributed Raman amplifier (DRA) ............ 23

Figure 3 – Example of the component layout of a lumped (or discrete) Raman

amplifier ................................................................................................................................ 24

Table 1 – Documents defining terms and definitions of each component ............................... 22

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– 4 – IEC TR 61292-1:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL AMPLIFIERS –
Part 1: Parameters of optical fibre amplifier components
FOREWORD

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

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

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

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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.

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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.

IEC TR 61292-1 has been prepared by subcommittee 86C: Fibre optic systems and active

devices, of IEC technical committee 86: Fibre optics. It is a Technical Report.

This third edition cancels and replaces the second edition published in 2009. This edition

constitutes a technical revision.

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

edition:

a) Change of document title from "Parameters of amplifier components" to "Parameters of

optical fibre amplifier components";
b) Addition of parameters for optical components used in fibre Raman amplifiers;

c) Addition of Table 1, listing various documents that specify terms and definitions for optical

components used in optical fibre amplifiers;

d) Addition of Figure 2 and Figure 3, showing typical component layouts for distributed and

lumped fibre Raman amplifiers;
---------------------- Page: 6 ----------------------
IEC TR 61292-1:2022 © IEC 2022 – 5 –

e) Harmonization of the descriptions of optical component parameters with the definitions in

other standards on optical components.
The text of this Technical Report is based on the following documents:
Draft Report on voting
86C/1775/DTR 86C/1784/RVDTR

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.
The language used for the development of this Technical Report is English.

A list of all parts of the IEC 61292 series, published under the general title Optical amplifiers,

can be found on the IEC website.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/publications.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under 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.
---------------------- Page: 7 ----------------------
– 6 – IEC TR 61292-1:2022 © IEC 2022
OPTICAL AMPLIFIERS –
Part 1: Parameters of optical fibre amplifier components
1 Scope

This part of IEC 61292, which is a Technical Report, applies to optical components of optical

fibre amplifiers (OFAs). This document provides information about the most relevant parameters

of these optical components, especially for erbium doped fibre amplifiers (EDFAs) and fibre

Raman amplifiers (FRAs). It provides introductory information for a better understanding

operation and applications of EDFAs and FRAs.
NOTE IEC TR 61292-6 provides more technical information on FRAs.
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 61291-1:2018, Fibre amplifiers – Generic specification
IEC TR 61931, Fibre optic – Terminology
3 Terms, definitions, abbreviated terms and symbols
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 61291-1,

IEC TR 61931, and the following apply.

ISO and IEC maintain terminology databases for use in standardization at the following

addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1 Parameters for active fibres
3.1.1.1
maximum input signal power

maximum power of the input signal above which the active fibre gets damaged,

causing impossibility of normal operation for a given active fibre
3.1.1.2
insertion loss at out-of-band wavelength

insertion loss for a signal at the specified out-of-band wavelength(s) for a given

active fibre

Note 1 to entry: IEC 61290-7-1 defines the measurement procedure of out-of-band insertion loss.

[SOURCE: IEC 61291-1:2018, 3.2.1.59, modified – Term changed from "out-of-band insertion

loss", the specific use "active fibres" has been added, and Note 1 to entry has been added.]

---------------------- Page: 8 ----------------------
IEC TR 61292-1:2022 © IEC 2022 – 7 –
3.1.1.3
polarization-dependent gain

maximum variation of the active fibre gain due to a variation of the state of

polarization of the input signal

[SOURCE: IEC 61291-1:2018, 3.2.1.12, modified – The notes to entry have been deleted and

the specific use has been added.]
3.1.1.4
polarization mode dispersion
PMD

maximum PMD at the signal wavelength which is launched into the input port of

the active fibre and exits from signal output port of the active fibre
Note 1 to entry: PMD is expressed in ps.

Note 2 to entry: When an optical signal travels through an optical fibre, optical component or subsystem (e.g. an

OFA), the change in the shape and width of the pulse due to the differential group delay (DGD) [the propagation

delay difference between the two principal states of polarization (PSPs)] and to the waveform distortion for each PSP,

is due to PMD. PMD, together with polarization dependent loss (PDL) and polarization dependent gain (PDG), can

introduce large waveform distortions leading to an unacceptable bit error ratio increase.

Note 3 to entry: The level of PMD can depend on temperature and operating conditions.

3.1.1.5
mode field diameter
MFD

for a given active fibre, a measure of the transverse width of the guided mode

of a single-mode fibre, given from the far-field intensity distribution F(q) by:
3 2
2 q F q dq
( )
2 ∫
2w=
qF q dq
( )
0
where
q= sinθλ/
( )

Note 1 to entry: For Gaussian distributions in single-mode fibres the mode field diameter is the diameter at the 1/e

points of the optical field amplitude distribution, which is also equivalent to the 1/e points of the optical power

distribution.

Note 2 to entry: Sometimes the MFD of active fibres is smaller than that of conventional single-mode fibres in order

to concentrate the pump power with the signal optical power.

[SOURCE: IEC TR 61931:1998, 2.4.31, modified – Specific use added and Note 2 to entry has

been added.]
3.1.1.6
cut-off wavelength

for a given active fibre, the free space wavelength corresponding to the cut-off

normalized frequency of a mode
[SOURCE: IEC TR 61931:1998, 2.4.38, modified – Specific use has been added.]
3.1.1.7
cladding diameter

for a given active fibre, the diameter of the circle defining the cladding centre

---------------------- Page: 9 ----------------------
– 8 – IEC TR 61292-1:2022 © IEC 2022
[SOURCE: IEC TR 61931, 2.3.39]
3.1.1.8
cladding non-circularity

for a given active fibre, the difference between the diameters of the two circles

defined by the cladding tolerance field divided by the cladding diameter
[SOURCE: IEC TR 61931:1998, 2.3.51, modified – Specific use has been added.]
3.1.1.9
mode field concentricity error

for a given active fibre, the distance between the mode field centre and the

cladding centre
[SOURCE: IEC TR 61931:1998, 2.4.34, modified – Specific use has been added.]
3.1.1.10
composition

composition of the active fibre, intended as the host glass composition as well

as the dopant element and its concentration
3.1.1.11
length
length of the active fibre

Note 1 to entry: Changing fibre length can optimize gain characteristics of EDFA.

3.1.1.12
dopant distribution

concentration of dopant rare-earth ions in the active fibre as a function of the

fibre radial coordinate
3.1.1.13
slope efficiency

for a given active fibre, the slope of the laser output versus pump power curve

under specified operating conditions

Note 1 to entry: IEC TR 63309 defines the measurement procedure of slope efficiency.

3.1.1.14
saturation pump power

for a given active fibre, the minimum pump power above which the small-signal

gain shows no further increase
3.1.1.15
threshold pump power

minimum pump power necessary to reach a small-signal gain equal to 1 in a

given active fibre when the fibre length is short enough so that the pump optical power remains

constant along the fibre

Note 1 to entry: IEC TR 63309 defines the measurement procedure of threshold pump power.

3.1.2 Parameters for pump lasers
3.1.2.1
pumping wavelength

centroidal or peak wavelength of the emission spectrum of the pump laser

---------------------- Page: 10 ----------------------
IEC TR 61292-1:2022 © IEC 2022 – 9 –

Note 1 to entry: In erbium-doped fibre amplifiers (EDFAs), pumping wavelengths of 980 nm and 1 480 nm are

commonly used. In fibre Raman amplifier (FRAs), the pumping wavelength depends on the wavelength of the signal

light. In this case, the frequency of the pump laser should be about 13 THz higher than that of the signal light.

Note 2 to entry: Centroidal wavelength is defined in IEC 61280-1-3.

Note 3 to entry: For multi-longitudinal-mode laser diodes (LD), centroidal wavelength is often used. For single-

longitudinal-mode LD, peak wavelength is often used.

Note 4 to entry: For 980 nm LD, a wavelength stabilizer by FBG is sometimes used to the output pigtail of the LD.

3.1.2.2
pumping scheme

set-up of the OFA characterized by the direction of pump optical power

propagation with respect to signal direction

Note 1 to entry: Usually, three schemes are used: co-propagating, where the pump and the signal propagate

through the active fibre in the same direction; counter-propagating, where the signal and the pump propagate through

the active fibre in opposite directions; bi-directional, where two pumps propagate simultaneously through the active

fibre in both directions. Regarding pumping schemes other than pump direction, a polarization combining scheme

and a wavelength combining scheme are considered in the detailed design to increase pump power. However, a

single laser diode pump scheme is described as a classic example in this technical report.

Note 2 to entry: IEC TR 61292-3 describes the pumping method.
3.1.2.3
pumping power

at the active fibre or at the output of the pump, optical power associated with

the pump, injected into the active fibre
3.1.2.4
centroidal wavelength
mean or average wavelength of an optical spectrum of pump LD

Note 1 to entry: Regarding many pump LDs of 980 nm and 1 480 nm, centroidal wavelength λ is applied for

avg

centre wavelength λ . The definition of centroidal wavelength is described as follows:

 
λ = Pλ
 
avg ∑ ii
 
  i= 1
where
λ is the wavelength of the i peak point (nm);
i corresponds to mode number for output spectra of pump LD;
P is the power of the i peak point (nW); and
P is the total power summed for all peak points (nW):
PP=
0 ∑ i
i= 1
N is the number of peak points.

Note 2 to entry: The pump efficiency of an EDF depends on the overlap integral of the EDF absorption spectrum

and the pump LD spectrum, so the centroidal wavelength of the pump laser is crucial for EDF pumping.

3.1.2.5
peak wavelength

wavelength which corresponds to the maximum power value of the optical

spectrum of pump LD
---------------------- Page: 11 ----------------------
– 10 – IEC TR 61292-1:2022 © IEC 2022

Note 1 to entry: For some pump LDs operating at 980 nm and 1 480 nm with FBG stabilizer, the peak wavelength

λ is used as the centre wavelength λ . The definition of peak wavelength is described as follows:

peak c
λλ=
c peak
Note 2 to entry: Refer to IEC 61280-1-3 for details.
3.1.2.6
root mean square (RMS) spectral width
spectral width defined by RMS

Note 1 to entry: Regarding many pump LDs of 980 nm and 1 480 nm, the RMS spectral width Δλ is used to

rms

characterize spectral width. The definition of RMS spectral width is described as follows:

N 2
Δλ P ()λ−λ
rms ∑ ii c
i= 1

Note 2 to entry: The pump efficiency of an EDF depends on the overlap integral of the EDF absorption spectrum

and the pump LD spectrum, so the pumping spectral width of pump laser is a crucial factor for EDF pumping in order

to quantify the power band width of the pump LD.
3.1.2.7
full-width at half maximum (FWHM) spectral width
spectral width defined by FWHM

Note 1 to entry: Regarding some pump LDs of 980 nm and 1 480 nm with FBG stabilizer, full-width at half maximum

(FWHM) Δλ is used to characterize spectral width. The definition of the FWHM spectral width is described as

fwhm
follows:
λ ,

1) The positive difference of the closest spaced wavelengths, one above and one below the peak wavelength

peak
at which the spectral power density is 3 dB down from its peak value;

2) If the pump laser does not emit light at these half-power wavelengths, the FWHM spectral width can be determined

by interpolation as follows;

3) Connect the tip of each mode to the tips of adjacent modes; draw a horizontal line 3 dB down from the peak

power point;

4) The two or more intersection points define the half-power wavelengths. The maximum difference in half-power

wavelengths is Δλ .
fwhm
Note 2 to entry: See IEC 61280-1-3 for more details.
3.1.2.8
wavelength stability

rate of variation of pumping wavelength with respect to operating and

environmental conditions
3.1.2.9
pumping spectral width
effective width of emission spectrum of the pump laser
Note 1 to entry: Commonly, RMS spectral width is used.
3.1.2.10
threshold current
driving current at which the pump laser starts to lase

Note 1 to entry: Practically, this value is specified as the crossing condition between the spontaneous emission and

lasing regions.
---------------------- Page: 12 ----------------------
IEC TR 61292-1:2022 © IEC 2022 – 11 –
3.1.2.11
maximum allowed current

maximum driving current which can cause irreversible damage to the pump laser

Note 1 to entry: The absolute maximum rated current is generally applied.
3.1.2.12
pump LD chip temperature

temperature of LD chip to be controlled for normal operation, where performance

of pump LD is ensured

Note 1 to entry: The output power and operating wavelength are affected by laser chip temperature. Therefore,

ordinary pump LD modules include a thermoelectric cooler (TEC) so as to maintain a constant LD chip temperature.

A temperature range of 25 ˚C to 45 ˚C is commonl
...

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