Optical amplifiers - Test methods - Part 10-5: Multichannel parameters - Distributed Raman amplifier gain and noise figure

IEC 61290-10-5:2014 applies to distributed Raman amplifiers (DRAs). DRAs are based on the process whereby Raman pump power is introduced into the transmission fibre, leading to signal amplification within the transmission fibre through stimulated Raman scattering. A detailed overview of the technology and applications of DRAs can be found in IEC TR 61292-6. The object of this standard is to establish uniform requirements for accurate and reliable measurements, using an optical spectrum analyser (OSA), of the following DRA parameters: - channel on-off gain; - pump unit insertion loss; - channel net gain; - channel signal-spontaneous noise figure. Keywords: Raman amplifiers (DRAs), optical spectrum analyser (OSA)

Prüfverfahren für Lichtwellenleiter-Verstärker - Teil 10-5: Mehrkanalparameter - Verstärkung und Rauschzahl von verteilten Raman-Verstärkern

Amplificateurs optiques - Méthodes d'essai - Partie 10-5: Paramètres à canaux multiples - Gain et facteur de bruit des amplificateurs Raman répartis

L'IEC 61290-10-5:2014 s'applique aux amplificateurs Raman répartis (DRA). Les DRA sont fondés sur un processus tel qu'une puissance de pompage Raman est introduite dans la fibre de transmission, conduisant à une amplification du signal au sein de la fibre de transmission par dispersion Raman stimulée. On peut trouver une vue d'ensemble détaillée de la technique et des applications des DRA dans l'IEC TR 61292-6. L'objet de la présente norme est d'établir des exigences uniformes afin d'obtenir des mesures précises et fiables des paramètres de DRA suivants, au moyen d'un analyseur de spectre optique (ASO): - gain du canal en on-off; - affaiblissement d'insertion de l'unité de pompage; - gain du canal net; - facteur de bruit signal/émission spontanée du canal. Mots clés: amplificateurs Raman (DRA), analyseur de spectre optique (ASO)

Optični ojačevalniki - Preskusne metode - 10-5. del: Večkanalni parametri - Razpršeno ojačenje Ramanovega ojačevalnika in šumno število (IEC 61290-10-5:2014)

Ta del standarda IEC 61290 se uporablja za razpršene Ramanove ojačevalnike (DRA). Razpršeni Ramanovi ojačevalniki temeljijo na procesu, pri katerem je moč Ramanove črpalke uvedena v prenosno vlakno, ki vodi do ojačenja signala znotraj prenosnega vlakna prek stimuliranega Ramanovega sipanja. Podroben pregled tehnologije in uporabe razpršenih Ramanovih ojačevalnikov je na voljo v standardu IEC TR 61292-6.
Temeljna razlika med temi ojačevalniki in diskretnimi ojačevalniki, kot so EDFA, je, da se lahko ojačevalniki EDFA opišejo z uporabo pristopa po načelu črne skrinjice z dobro opredeljenimi vhodnimi in izhodnimi vrati. Na drugi strani je razpršeni Ramanov ojačevalnik v bistvu modul črpalke s postopkom dejanskega ojačenja vzdolž prenosnega vlakna. Ta razlika pomeni, da standardnih metod, opisanih v drugih delih standarda IEC 61290 za merjenje parametrov ojačevalnika, kot sta ojačenje in šumno število, ni mogoče uporabiti brez spreminjanja.
Cilj tega standarda je določiti enotne zahteve za točne in zanesljive meritve z uporabo optičnega spektralnega analizatorja (OSA) za naslednje parametre razpršenega Ramanovega ojačevalnika:
a) vklopno-izklopno ojačenje kanala;
b) dodano dušenje črpalke;
c) neto ojačenje kanala;
d) signalno spontano šumno število kanala.
Merilna metoda temelji predvsem na metodi z odvzemanjem interpoliranega vira (ISS) z uporabo analizatorja optičnega spektra, kot je opisano in pripravljeno v standardu IEC 61290-10-4, z ustreznimi spremembami, ki se nanašajo na razpršene Ramanove ojačevalnike. Vse številčne vrednosti, za katerimi je znak (‡), so predlagane vrednosti, za katere se zagotovi merjenje. Druge vrednosti se lahko sprejmejo, vendar naj bi se preverile.
OPOMBA: Splošni vidiki preskusnih metod za šumno število so navedeni v standardu IEC 61290-3.

General Information

Status
Published
Publication Date
24-Jul-2014
Current Stage
6060 - Document made available
Due Date
25-Jul-2014
Completion Date
25-Jul-2014

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SLOVENSKI STANDARD
SIST EN 61290-10-5:2015
01-april-2015
2SWLþQLRMDþHYDOQLNL3UHVNXVQHPHWRGHGHO9HþNDQDOQLSDUDPHWUL
5D]SUãHQRRMDþHQMH5DPDQRYHJDRMDþHYDOQLNDLQãXPQRãWHYLOR ,(&


Optical amplifiers - Test methods -- Part 10-5: Multichannel parameters - Distributed

Raman amplifier gain and noise figure (IEC 61290-10-5:2014)
Prüfverfahren für Lichtwellenleiter-Verstärker - Teil 10-5: Mehrkanalparameter -

Verstärkung und Rauschzahl von verteilten Raman-Verstärkern (IEC 61290-10-5:2014)

Amplificateurs optiques - Méthodes d'essai - Partie 10-5: Paramètres à canaux multiples

- Gain et facteur de bruit des amplificateurs Raman répartis (CEI 61290-10-5:2014)

Ta slovenski standard je istoveten z: EN 61290-10-5:2014
ICS:
33.180.30 2SWLþQLRMDþHYDOQLNL Optic amplifiers
SIST EN 61290-10-5:2015 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 61290-10-5:2015
---------------------- Page: 2 ----------------------
SIST EN 61290-10-5:2015
EUROPEAN STANDARD EN 61290-10-5
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2014
ICS 33.180.30
English Version
Optical amplifiers - Test methods - Part 10-5: Multichannel
parameters - Distributed Raman amplifier gain and noise figure
(IEC 61290-10-5:2014)

Amplificateurs optiques - Méthodes d'essai - Partie 10-5: Prüfverfahren für Lichtwellenleiter-Verstärker - Teil 10-5:

Paramètres à canaux multiples - Gain et facteur de bruit Mehrkanalparameter - Verstärkung und Rauschzahl von

des amplificateurs Raman répartis verteilten Raman-Verstärkern
(CEI 61290-10-5:2014) (IEC 61290-10-5:2014)

This European Standard was approved by CENELEC on 2014-06-27. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2014 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 61290-10-5:2014 E
---------------------- Page: 3 ----------------------
SIST EN 61290-10-5:2015
EN 61290-10-5:2014 - 2 -
Foreword

The text of document 86C/1142/CDV, future edition 1 of IEC 61290-10-5, prepared by SC 86C "Fibre

optic systems and active devices” of IEC/TC 86 “Fibre optics" was submitted to the IEC-CENELEC

parallel vote and approved by CENELEC as EN 61290-10-5:2014.
The following dates are fixed:
(dop) 2015-03-27
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2017-06-27
• latest date by which the national
standards conflicting with the
document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such

patent rights.
Endorsement notice

The text of the International Standard IEC 61290-10-5:2014 was approved by CENELEC as a

European Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 61290-3 NOTE Harmonized as EN 61290-3.
IEC 61290-10-4 NOTE Harmonized as EN 61290-10-4.
---------------------- Page: 4 ----------------------
SIST EN 61290-10-5:2015
- 3 - EN 61290-10-5:2014
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

NOTE 1 When an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu
Publication Year Title EN/HD Year
IEC 60825-1 - Safety of laser products -- Part 1: EN 60825-1 -
Equipment classification and requirements
IEC 61291-1 - Optical amplifiers -- Part 1: Generic EN 61291-1 -
specification
IEC 61291-4 - Optical amplifiers -- Part 4: Multichannel EN 61291-4 -
applications - Performance specification
template
IEC/TR 61292-4 - Optical amplifiers -- Part 4: Maximum - -
permissible optical power for the damage-
free and safe use of optical amplifiers,
including Raman amplifiers
---------------------- Page: 5 ----------------------
SIST EN 61290-10-5:2015
---------------------- Page: 6 ----------------------
SIST EN 61290-10-5:2015
IEC 61290-10-5
Edition 1.0 2014-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Optical amplifiers – Test methods –
Part 10-5: Multichannel parameters – Distributed Raman amplifier gain and
noise figure
Amplificateurs optiques – Méthodes d'essai –
Partie 10-5: Paramètres à canaux multiples – Gain et facteur de bruit des
amplificateurs Raman répartis
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX S
ICS 33.180.30 ISBN 978-2-8322-1581-4

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

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 7 ----------------------
SIST EN 61290-10-5:2015
– 2 – IEC 61290-10-5:2014 © IEC 2014
CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope and object ............................................................................................................. 5

2 Normative references ...................................................................................................... 5

3 Terms, definitions and abbreviations ............................................................................... 6

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

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

4 DRA gain and noise figure parameters – Overview .......................................................... 7

5 Apparatus ........................................................................................................................ 9

5.1 General ................................................................................................................... 9

5.2 Multi-channel signal source ................................................................................... 10

5.3 Polarization controller ........................................................................................... 11

5.4 Optical spectrum analyser ..................................................................................... 11

5.5 Optical power meter .............................................................................................. 12

5.6 Tuneable narrowband source ................................................................................ 12

5.7 Broadband optical source ..................................................................................... 12

5.8 Optical connectors and jumpers ............................................................................ 12

6 Test sample ................................................................................................................... 12

7 Procedure ...................................................................................................................... 12

7.1 Overview............................................................................................................... 12

7.1.1 Channel on-off gain ....................................................................................... 12

7.1.2 Pump module channel insertion loss and channel net gain ............................ 13

7.1.3 Channel equivalent noise figure (NF) ............................................................. 13

7.2 Calibration ............................................................................................................ 13

7.2.1 Calibration of optical bandwidth ..................................................................... 13

7.2.2 Calibration of OSA power correction factor .................................................... 15

7.3 Measurement ........................................................................................................ 15

7.4 Calculation ............................................................................................................ 17

7.4.1 Channel on-off gain ....................................................................................... 17

7.4.2 Channel net gain ........................................................................................... 17

7.4.3 Channel equivalent NF................................................................................... 17

8 Test results ................................................................................................................... 17

Annex A (informative) Field measurements versus laboratory measurements ...................... 19

Annex B (informative) Pump depletion and channel-to-channel Raman scattering ................ 20

Bibliography .......................................................................................................................... 21

Figure 1 – Distributed Raman amplification in co-propagating (left) and count-

propagating (right) configurations ........................................................................................... 9

Figure 2 – Measurement set-up without a pump module........................................................ 10

Figure 3 – Measurement set-up for counter-propagating configuration .................................. 10

Figure 4 – Measurement set-up for co-propagating configuration .......................................... 10

Figure 5 – Possible implementation of a multi-channel signal source .................................... 11

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SIST EN 61290-10-5:2015
IEC 61290-10-5:2014 © IEC 2014 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL AMPLIFIERS –
TEST METHODS –
Part 10-5: Multichannel parameters –
Distributed Raman amplifier gain and noise figure
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 61290-10-5 has been prepared by 86C: Fibre optic systems and

active devices, of IEC technical committee 86: Fibre optics.
The text of this standard is based on the following documents:
CDV Report on voting
86C/1142/CDV 86C/1233/RVC

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

---------------------- Page: 9 ----------------------
SIST EN 61290-10-5:2015
– 4 – IEC 61290-10-5:2014 © IEC 2014

A list of all parts in 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 publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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.
---------------------- Page: 10 ----------------------
SIST EN 61290-10-5:2015
IEC 61290-10-5:2014 © IEC 2014 – 5 –
OPTICAL AMPLIFIERS –
TEST METHODS –
Part 10-5: Multichannel parameters –
Distributed Raman amplifier gain and noise figure
1 Scope and object

This part of IEC 61290 applies to distributed Raman amplifiers (DRAs). DRAs are based on

the process whereby Raman pump power is introduced into the transmission fibre, leading to

signal amplification within the transmission fibre through stimulated Raman scattering.

A detailed overview of the technology and applications of DRAs can be found in
IEC TR 61292-6.

A fundamental difference between these amplifiers and discrete amplifiers, such as EDFAs, is

that the latter can be described using a black box approach with well-defined input and output

ports. On the other hand, a DRA is basically a pump module, with the actual amplification

process taking place along the transmission fibre. This difference means that standard

methods described in other parts of IEC 61290 for measuring amplifier parameters, such as

gain and noise figure, cannot be applied without modification.

The object of this standard is to establish uniform requirements for accurate and reliable

measurements, using an optical spectrum analyser (OSA), of the following DRA parameters:

a) channel on-off gain;
b) pump unit insertion loss;
c) channel net gain;
d) channel signal-spontaneous noise figure.

The measurement method is largely based on the interpolated source subtraction (ISS)

method using an optical spectrum analyser, as described and elaborated in IEC 61290-10-4,

with relevant modifications relating to a DRA.

All numerical values followed by (‡) are suggested values for which the measurement is

assured. Other values may be acceptable but should be verified.
NOTE General aspects of noise figure test methods are reported in IEC 61290-3.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.

IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements

IEC 61291-1, Optical amplifiers – Part 1: Generic specification

IEC 61291-4, Optical amplifiers – Part 4: Multichannel applications – Performance

specification template
---------------------- Page: 11 ----------------------
SIST EN 61290-10-5:2015
– 6 – IEC 61290-10-5:2014 © IEC 2014

IEC TR 61292-4, Optical amplifiers – Part 4: Maximum permissible optical power for the

damage-free and safe use of optical amplifiers, including Raman amplifiers
3 Terms, definitions and abbreviations
3.1 Terms and definitions
3.1.1
Raman pump power

optical power produced by the DRA to enable Raman amplification of signal channels

Note 1 to entry: The Raman pump power shall be at a lower wavelength than the signal channels.

3.1.2
fibre span

length of fibre into which signal channels and Raman pump power are introduced, and Raman

amplification of the signal channels takes place via stimulated Raman scattering
3.1.3
co-propagating configuration
forward pumping configuration

configuration whereby the Raman pump power is coupled to the input of the fibre span such

that the signal channels and Raman pump power propagate in the same (forward) direction

3.1.4
counter-propagating configuration
backward pumping configuration

configuration whereby the Raman pump power is coupled to the output of the fibre span such

that the signal channels and Raman pump power propagate in opposite directions
3.1.5
pump module

module that produces Raman pump power and couples it into the connected fibre span

Note 1 to entry: If the pump module is connected to the input of the fibre span, then both the incoming signal

channels and Raman pump power are coupled to the fibre span.

Note 2 to entry: If the pump module is connected to the output of the fibre span, then the pump power is coupled

into the fibre span, while the signal channels exiting the fibre span pass through the pump module from the input

port to the output port.

Note 3 to entry: In this standard, the convention will be used whereby the input port of the pump module is

defined as the port into which the signal channels enter, while the output port is defined as the port through which

the signal channels exit. Thus, in co-propagating configuration the Raman pump power exits the pump module from

the output port, while in counter-propagating configuration the Raman pump power exits the pump module from the

input port.
3.1.6
channel on-off gain
on-off

ratio of the channel power at the output of the fibre span when the pump module is

operational to the channel power at the same point when the pump module is not operational

3.1.7
pump module channel insertion loss

ratio of the channel power at the input of the pump module to the channel power at the output

of the pump module
---------------------- Page: 12 ----------------------
SIST EN 61290-10-5:2015
IEC 61290-10-5:2014 © IEC 2014 – 7 –
3.1.8
channel net gain
net
channel on-off gain minus the pump module channel insertion loss, in dB
3.1.9
channel equivalent noise figure
sig-ASE,eq

channel noise figure due to signal-spontaneous beat noise (see IEC 61290-3) of an equivalent

discrete amplifier placed at the output of the fibre span which has the same channel gain as

the DRA channel on-off gain, and generates the same amount of ASE as that generated by

the DRA at the output of the fibre span.
3.2 Abbreviated terms
ASE amplified spontaneous emission
DRA distributed Raman amplifier
EDFA Erbium doped fibre amplifier
FWHM full-width half-maximum
GFF gain flattening filter
ISS interpolated source subtraction
NF noise figure
RBW resolution bandwidth
OSA optical spectrum analyser
OSNR optical signal-to-noise ratio
PCF power correction factor
SMF single-mode fibre
SSE source spontaneous emission
VOA variable optical attenuator
4 DRA gain and noise figure parameters – Overview

NOTE Unless specifically stated otherwise, all equation and definitions in this clause and onwards are given in

linear units, and not dB.

Figure 1 shows the application of DRAs in co-propagating (forward pumping) and counter-

propagating (backward pumping) configurations. As a general rule, counter propagating

configuration is much more widely used compared to co-propagating configuration.

As with any amplifier, one of the main parameters of interest is the channel gain (see

IEC 61291-1 and IEC 61291-4). However, unlike discrete amplifiers, where the channel gain

is simply defined as the ratio of the channel power at the output port to the channel power at

the input port, with a DRA, the situation is more complex. In principle, the DRA includes both

the pump module, which supplies the pump power, and the fibre span, where the actual

amplification takes place. Thus, one option for defining channel gain is to define it as the ratio

of the channel power at point C (Figure 1) to the channel power at point A, while the pumps

are operational. However, since this definition also include the fibre span loss, which is often

larger than the gain supplied by the Raman pumps, this definition is not very useful.

A much more useful quantity is the channel on-off gain, which is defined as the ratio of the

channel power at the output of the fibre span when the Raman pumps are on to the channel

power at the same point but when the pumps are off (see the graphs in Figure 1).
---------------------- Page: 13 ----------------------
SIST EN 61290-10-5:2015
– 8 – IEC 61290-10-5:2014 © IEC 2014
G =
(1)
on−off
off

In practice, the channel on-off gain may be measured at any point following the fibre span, for

example point C for co-propagating configuration, or points B and C for the counter-

propagating configuration.

Another parameter of interest for DRAs is the pump module channel insertion loss, which is

defined as the ratio of the channel power at the input port of the pump module to the channel

power at the output port of the pump module (points A and B for co-propagating configuration,

and points B and C for counter propagating configuration).
pump unit input
IL=
(2)
pump unit output

Since no amplification takes place within the pump module, this is just passive insertion loss,

and is not affected by the status of the pumps (on or off).

The channel on-off gain and pump module channel insertion loss can be combined into a

single quantity, the channel net gain, which is defined in dB as
G (dB)=G (dB)−IL(dB) (3)
net on−off

The channel net gain is particularly useful for counter-propagating configuration, as it may be

directly measured in linear units as the ratio of the channel power at point C when the pumps

are on to the channel power at point B when the pumps are off. When the pump module

includes a gain flattening filter (GFF) to tailor the spectral shape of the Raman gain, then the

channel net gain includes the effect of the GFF, as opposed to the channel on-off gain which

does not (i.e. the channel on-off gain has a non-flat dependence on the channel wavelength).

For the co-propagating configuration, the channel net gain has less physical meaning, and it

is more common to separately define the channel on-off gain and pump module channel

insertion loss.

Another important parameter relevant to a DRA is the channel equivalent noise figure (NF)

due to signal-spontaneous beat noise. This quantity is only relevant to counter-propagating

configuration. The channel equivalent NF of a DRA is defined as the NF of an equivalent

discrete amplifier placed at the output of the fibre span, which provides the same amount of

channel gain as the DRA channel on-off gain, and generates the same amount of amplified

spontaneous emission (ASE) as that generated at the fibre span output by the DRA. The

channel equivalent noise figure (in dB) due to signal-spontaneous beat noise is given by (see

IEC 61290-3):
NF = 10log (ρ /(G hν))
(4)
sig−ASE,eq 10 ASE,B on−off
where
ρ is the ASE spectral density at the channel wavelength λ (in both polarization
ASE,B

modes) measured at the output of the fibre span (point B in the counter-propagating

configuration of Figure 1);
ν=c /λ is the channel frequency;
h is Planck’s constant.

Using the relation between the channel on-off gain and the channel net gain, it is easily

shown that the channel equivalent NF is also given by
---------------------- Page: 14 ----------------------
SIST EN 61290-10-5:2015
IEC 61290-10-5:2014 © IEC 2014 – 9 –
NF = 10log (ρ /(G hν))
sig−ASE,eq 10 ASE,C net (5)
where
ρ is now measured at point C.
ASE,C
Counter-propagating configuration
Co-propagating configuration
Fibre span
Fibre span
Signal Signal
A C A C
B B
Pump Pump
module module
Pump Pump
30 30
Pump
Pump
Signal with pump on
Signal with pump on
20 20
Signal with pump off
Signal with pump off
10 10
0 0
–10
–10
–20
–20
On-off On-off
gain gain
–30 –30
0 50 100 150 0 50 100 150
Position along span (km) Position along span (km)
IEC 1389/14
NOTE The graphs show the evolution of pump and signal along the fibre span.
Figure 1 – Distributed Raman amplification in co-propagating (left)
and count-propagating (right) configurations
When measuring DRA gain and NF, the following issues should be considered:
a) The purpose of the measurement: whether the purpose is to measure the DRA

performance in relation to a specific span of fibre in the field, or characterize DRA

performance with respect to a generic fibre type in the laboratory. This is elaborated in

Annex A.

b) Whether or not the input signal configuration can affect the measurement due to pump

depletion and/or signal-signal Raman scattering. This is elaborated in Annex B.
5 Apparatus
5.1 General

Figures 2 through 4 show the measurement set-up for measurement of DRA parameters in

counter-propagating and co-propagating configurations. The various components comprising

the set-up (as well as other components used for calibration) are described in the following

subclauses.
Power (dBm)
Power (dBm)
---------------------- Page: 15 ----------------------
SIST EN 61290-10-5:2015
– 10 – IEC 61290-10-5:2014 © IEC 2014
Fibre span
Signal
Multi-channel Polarization
OSA
signal source controller
IEC 1390/14
Figure 2 – Measurement set-up without a pump module
Fibre span
Signal
Pump
Multi-channel Polarization
OSA
module
signal source controller
Pump
IEC 1391/14
Figure 3 – Measurement set-up for counter-propagating configuration
Fibre span
Signal
Pump
Multi-channel Polarization
OSA
module
signal source controller
Pump
IEC 1392/14
Figure 4 – Measurement set-up for co-
...

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