IEC 60728-6:2011

Cable networks for television signals, sound signals and interactive services - Part 6: Optical equipment

IEC 60728-6:2011 lays down the measuring methods, performance requirements and data publication requirements of optical equipment of cable networks for television signals, sound signals and interactive services. This third edition cancels and replaces the second edition published in 2003 of which it constitutes a technical revision. It includes the following significant technical changes with respect to the previous edition:
- The normative references were updated.
- The methods of measurement for optical power and return loss were substituted by references to other standards.
- The method of measurement for polarization dependent loss was deleted.
- A method of measurement for carrier-to-crosstalk ratio (CCR) was added.
- The methods of measurement for CSO and CTB of optical amplifiers were substituted by a method of measurement for microscopic gain tilt of optical amplifiers.
This parameter can be used for calculating the second order distortion of optical amplifiers according to the method described in the new Annex B. New classes for optical transmitters and receivers have been defined.

Réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonore et services interactifs – Partie 6: Matériels optiques

L'IEC 60728-6:2011 présente les méthodes de mesure, les exigences de performance et les exigences de publication de données des matériels optiques des réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonore et services interactifs.
La présente norme
• s'applique à tous les émetteurs, récepteurs, amplificateurs, coupleurs directifs, isolateurs, dispositifs de multiplexage, connecteurs et épissures, optiques, utilisés dans les réseaux de distribution par câbles;
• couvre la gamme de fréquences de 5 MHz à 3 000 MHz;
• identifie les exigences de performance garanties pour certains paramètres;
• présente les exigences de publication des données avec une performance garantie;
• décrit les méthodes de mesure pour l'essai de conformité.
Toutes les exigences et les données publiées concernent les niveaux de performance minimums dans la gamme de fréquence spécifiée et dans des conditions d'adaptation correcte, tels que pouvant s'appliquer aux réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonore et services interactifs.
L'IEC 60728-6:2011 annule et remplace la deuxième édition parue en 2003, dont elle constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente.
• Les références normatives ont été mises à jour.
• Les méthodes de mesure de la puissance optique et de l’affaiblissement de réflexion ont été remplacées par des références à d’autres normes.
• La méthode de mesure de l’affaiblissement dépendant de la polarisation a été supprimée.
• Une méthode de mesure du rapport porteuse sur diaphonie (CCR) a été ajoutée.
• Les méthodes de mesure de CSO (Distorsion composite d’ordre deux) et de CTB (Battement triple composite) des amplificateurs optiques ont été remplacées par une méthode de mesure de la variation de gain microscopique des amplificateurs optiques. Ce paramètre peut être utilisé pour calculer la distorsion d’ordre deux des amplificateurs optiques selon la méthode décrite à la nouvelle Annexe B.
• De nouvelles classes d’émetteurs et récepteurs optiques ont été définies.

General Information

• Status: Published
• Publication Date: 10-Apr-2011
• ICS: 33.060.40 - Cabled distribution systems
• ICS: 33.160.99 - Other audio, video and audiovisual equipment
• Technical Committee: TC 100 - Audio, video and multimedia systems and equipment
• Drafting Committee: WG 3 - TC 100/TA 5/WG 3
• Current Stage: PPUB - Publication issued
• Start Date: 11-Apr-2011
• Completion Date: 31-May-2011

Relations

• Revises: IEC 60728-6:2003 - Cable networks for television signals, sound signals and interactive services - Part 6: Optical equipment
• Effective Date: 05-Sep-2023

Overview

IEC 60728-6:2011 - "Cable networks for television signals, sound signals and interactive services - Part 6: Optical equipment" - is the third edition of the IEC international standard that specifies measurement methods, performance requirements and data‑publication requirements for optical equipment used in cable networks. It replaces the 2003 edition and incorporates technical updates such as revised normative references, new measurement parameters and updated classification and data‑sheet requirements for optical transmitters, receivers and amplifiers.

Key topics and technical requirements

This standard focuses on practical, reproducible test and specification practices for optical components in TV/sound/interactive cable systems. Important technical topics include:

• Measurement methods: procedures for optical power, loss, isolation, directivity, coupling ratio, saturation output power, centroidal wavelength, spectral width, linewidth and chirping of laser transmitters, optical modulation index, slope and flatness.
• Distortion and interference metrics: methods for CSO/CTB of transmitters, composite cross‑modulation, receiver intermodulation and a newly added method for carrier‑to‑crosstalk ratio (CCR).
• Optical amplifier parameters: introduction of microscopic gain tilt measurement (replacing earlier CSO/CTB approaches) and Annex B calculation method for estimating second‑order distortion from microscopic gain tilt.
• Noise and dynamic performance: relative intensity noise (RIN), equivalent input noise current, noise figure of amplifiers, SBS threshold and other noise parameters.
• Classification and data publication: defined classes for optical transmitters and receivers, required published data (data sheets/product specification worksheets - Annex A for amplifiers), plus recommendations for safety, EMC and environmental handling.
• Changes vs. previous edition: updated normative references, substitution of some measurement methods by references to other standards, deletion of polarization dependent loss measurement, and addition of CCR and microscopic gain tilt metrics.

Practical applications

IEC 60728-6:2011 is directly applicable to:

• Design and engineering of cable-TV optical links (HFC and fiber-fed headend/distribution).
• Manufacturing and factory acceptance testing (optical transmitters, receivers, EDFAs/amplifiers).
• Test labs and certification bodies performing standardized measurements for product compliance.
• Network operators and system integrators specifying supplier data sheets and verifying installed equipment performance.
• Procurement teams using the standard’s data‑publication requirements to compare products consistently.

Who should use this standard

• Optical component and equipment manufacturers
• Test laboratories and QA engineers
• Cable network designers and operators
• Procurement/specification engineers and standards/compatibility teams

Related standards

IEC 60728‑6:2011 references other normative documents for certain measurement techniques; users should consult associated IEC/ITU‑T optical measurement standards and industry test standards for complementary procedures and traceability.

Keywords: IEC 60728-6:2011, optical equipment, cable networks, optical amplifiers, optical transmitters, optical receivers, CCR, microscopic gain tilt, measurements, CSO, CTB, RIN, data publication.

Standards Content (Sample)

IEC 60728-6 ®
Edition 3.0 2011-04
INTERNATIONAL
STANDARD
Cable networks for television signals, sound signals and interactive services –
Part 6: Optical equipment
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IEC 60728-6 ®
Edition 3.0 2011-04
INTERNATIONAL
STANDARD
Cable networks for television signals, sound signals and interactive services –
Part 6: Optical equipment
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 33.060.40; 33.160.99 ISBN 978-2-88912-427-5
– 2 – 60728-6 © IEC:2011(E)
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references. 9
3 Terms, definitions, symbols and abbreviations . 11
3.1 Terms and definitions . 11
3.2 Symbols . 18
3.3 Abbreviations . 19
4 Methods of measurement . 20
4.1 Measurement requirements . 20
4.1.1 General . 20
4.1.2 Input specification . 20
4.1.3 Measurement conditions . 20
4.2 Optical power . 21
4.3 Loss, isolation, directivity and coupling ratio . 21
4.3.1 General . 21
4.3.2 Measurement requirements . 21
4.3.3 Principle of measurement . 21
4.4 Return loss . 22
4.5 Saturation output power of an optical amplifier . 22
4.5.1 Purpose . 22
4.5.2 Procedure . 22
4.6 Centroidal wavelength and spectral width under modulation . 22
4.7 Linewidth and chirping of transmitters with single mode lasers . 23
4.7.1 Purpose . 23
4.7.2 Equipment required . 23
4.7.3 General measurement requirements . 23
4.7.4 Procedure . 23
4.7.5 Potential sources of error . 25
4.8 Optical modulation index . 25
4.8.1 Purpose . 25
4.8.2 Equipment required . 25
4.8.3 Procedure . 25
4.8.4 Potential sources of error . 26
4.9 Reference output level of an optical receiver . 26
4.9.1 Purpose . 26
4.9.2 Equipment required . 26
4.9.3 General measurement requirements . 27
4.9.4 Procedure . 27
4.9.5 Potential sources of error . 27
4.10 Slope and flatness . 28
4.10.1 Purpose . 28
4.10.2 Equipment required . 28
4.10.3 Procedure . 28
4.10.4 Potential sources of error . 29

60728-6 © IEC:2011(E) – 3 –
4.11 Composite second order distortion (CSO) of optical transmitters . 29
4.11.1 Purpose . 29
4.11.2 Equipment required . 30
4.11.3 Procedure . 30
4.11.4 Potential sources of error . 30
4.12 Composite triple beats (CTB) of optical transmitters . 30
4.12.1 Purpose . 30
4.12.2 Equipment required . 31
4.12.3 Procedure . 31
4.12.4 Potential sources of error . 31
4.13 Composite crossmodulation of optical transmitters . 31
4.13.1 Purpose . 31
4.13.2 Equipment required . 32
4.13.3 Procedure . 32
4.13.4 Potential sources of error . 34
4.14 Receiver intermodulation . 34
4.14.1 Purpose . 34
4.14.2 Equipment required . 34
4.14.3 General measurement requirements . 35
4.14.4 Procedure . 35
4.14.5 Potential sources of error . 36
4.15 Microscopic gain tilt of optical amplifiers . 36
4.15.1 Purpose . 36
4.15.2 Equipment required . 36
4.15.3 Procedure . 37
4.15.4 Potential sources of error . 38
4.16 Noise parameters of optical transmitters and optical receivers . 38
4.16.1 Purpose . 38
4.16.2 Equipment required . 38
4.16.3 General measurement requirements . 39
4.16.4 Procedure . 40
4.16.5 Relative intensity noise . 42
4.16.6 Equivalent input noise current density . 42
4.16.7 Potential sources of error . 42
4.17 Method for combined measurement of relative intensity noise (RIN), optical
modulation index and equivalent input noise current . 43
4.17.1 Purpose . 43
4.17.2 Equipment required . 43
4.17.3 General measurement conditions . 44
4.17.4 Procedure . 44
4.17.5 Potential sources of error . 45
4.18 Noise figure of optical amplifiers . 45
4.19 Influence of fibre . 45
4.19.1 Purpose . 45
4.19.2 Equipment required . 45
4.19.3 Procedure . 45
4.19.4 Potential sources of error . 45
4.20 SBS threshold . 46

– 4 – 60728-6 © IEC:2011(E)
4.20.1 Purpose . 46
4.20.2 Equipment required . 46
4.20.3 Procedure . 46
4.20.4 Potential sources of error . 47
4.21 Carrier-to-crosstalk ratio (CCR) . 47
4.21.1 Purpose . 47
4.21.2 Equipment required . 47
4.21.3 Procedure . 47
4.21.4 Potential sources of error . 48
5 Universal performance requirements and recommendations . 48
5.1 Safety . 48
5.2 Electromagnetic compatibility (EMC) . 48
5.3 Environmental . 48
5.3.1 Requirements . 48
5.3.2 Storage . 49
5.3.3 Transportation . 49
5.3.4 Installation or maintenance . 49
5.3.5 Operation . 49
5.4 Marking . 49
6 Active equipment . 49
6.1 Optical forward path transmitters . 49
6.1.1 Classification . 49
6.1.2 Data publication requirement. 50
6.1.3 Recommendations . 50
6.1.4 Performance requirements . 51
6.2 Optical return path transmitters . 53
6.2.1 Classificaton . 53
6.2.2 Data publication requirement. 53
6.2.3 Recommendations . 53
6.2.4 Performance requirements . 54
6.3 Optical receivers . 54
6.3.1 Classification . 54
6.3.2 Data publication requirements . 54
6.3.3 Recommendations . 55
6.3.4 Performance requirements . 55
6.4 Optical amplifiers . 56
6.4.1 Classification . 56
6.4.2 Data publication requirements . 56
6.4.3 Performance requirements . 56
7 Connectors and splices . 57
Annex A (normative) Product specification worksheet for optical amplifiers . 58
Annex B (informative) Calculation of second-order distortion caused by microscopic
gain tilt of optical amplifiers . 59
Bibliography . 60

60728-6 © IEC:2011(E) – 5 –
Figure 1 – Tilt and microscopic gain tilt of optical amplifiers . 17
Figure 2 – Measurement of optical loss, directivity and isolation . 21
Figure 3 – Optical saturation output power . 22
Figure 4 – Measurement of the chirping and the linewidth of transmitters . 24
Figure 5 – Measurement of the optical modulation index . 26
Figure 6 – Measurement of the reference output level of an optical receiver . 27
Figure 7 – Measurement of the slope and flatness . 28
Figure 8 – Evaluation of the slope . 29
Figure 9 – Evaluating the flatness . 29
Figure 10 – Device under test for measuring CSO of optical transmitters . 30
Figure 11 – Device under test for measuring CTB of optical transmitters . 31
Figure 12 – Arrangement for measuring composite crossmodulation of optical
transmitters . 33
Figure 13 – Arrangement of test equipment for measuring receiver intermodulation . 35
Figure 14 – Arrangement of test equipment for measuring microscopic gain tilt . 37
Figure 15 – System with internal noise sources . 38
Figure 16 – PIN diode receiver . 39
Figure 17 – Optical transmission system under test . 40
Figure 18 – Arrangement of test equipment for carrier-to-noise measurement . 40
Figure 19 – Measurement set-up for determination of the noise parameters and the

optical modulation index . 44
Figure 20 – Arrangement for measuring the SBS threshold . 46
Figure 21 – Arrangement for measuring the CCR . 47
Figure 22 – Classification of return path transmitters . 53

Table 1 – Noise correction factors C for different noise level differences D . 41
n
Table 2 – Classes of optical forward path transmitters . 50
Table 3 – Data publication requirements for optical forward path transmitters . 50
Table 4 – Recommendations for optical forward path transmitters . 51
Table 5 – Requirements for optical forward path transmitters . 52
Table 6 – Data publication requirements for optical return path transmitters . 53
Table 7 – Recommendations for optical return path transmitters . 53
Table 8 – Requirements for optical return path transmitters . 54
Table 9 – Classification of optical receivers . 54
Table 10 – Data publication requirements for optical receivers . 55
Table 11 – Recommendations for optical receivers . 55
Table 12 – Performance requirements for optical receivers . 56
Table 13 – Classification of optical amplifiers . 56
Table 14 – Performance requirements for optical amplifiers . 57
Table A.1 – Parameters of optical amplifiers . 58

– 6 – 60728-6 © IEC:2011(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
CABLE NETWORKS FOR TELEVISION SIGNALS,
SOUND SIGNALS AND INTERACTIVE SERVICES –

Part 6: Optical equipment
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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6) All users should ensure that they have the latest edition of this publication.
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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
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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 60728-6 has been prepared by technical area 5: Cable networks for
television signals, sound signals and interactive services, of IEC technical committee 100:
Audio, video and multimedia systems and equipment.
This third edition cancels and replaces the second edition published in 2003 of which it
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition.
• The normative references were updated.
• The methods of measurement for optical power and return loss were substituted by
references to other standards.
• The method of measurement for polarization dependent loss was deleted.

60728-6 © IEC:2011(E) – 7 –
• A method of measurement for carrier-to-crosstalk ratio (CCR) was added.
• The methods of measurement for CSO and CTB of optical amplifiers were substituted by a
method of measurement for microscopic gain tilt of optical amplifiers. This parameter can
be used for calculating the second order distortion of optical amplifiers according to the
method described in the new Annex B.
• New classes for optical transmitters and receivers have been defined.
The text of this standard is based on the following documents:
CDV Report on voting
100/1654/CDV 100/1789/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.
The list of all the parts of the IEC 60728 series, under the general title Cable networks for
television signals, sound signals and interactive services, 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.
A bilingual version of this publication may be issued at a later date.

– 8 – 60728-6 © IEC:2011(E)
INTRODUCTION
Standards of the IEC 60728 series deal with cable networks including equipment and
associated methods of measurement for headend reception, processing and distribution of
television signals, sound signals and their associated data signals and for processing,
interfacing and transmitting all kinds of signals for interactive services using all applicable
transmission media.
• This covers all kinds of networks that convey modulated RF carriers such as CATV-
networks;
• MATV-networks and SMATV-networks;
• individual receiving networks;
and all kinds of equipment, systems and installations installed in such networks.
NOTE CATV encompasses the Hybrid Fibre Coaxial (HFC) networks used nowadays to provide
telecommunications services, voice, data and audio and video both broadcast and narrowcast.
The extent of this standardisation work is from the antennas and/or special signal source
inputs to the headend or other interface points to the network up to the terminal input.
The standardisation of any user terminals (i.e. tuners, receivers, decoders, multimedia
terminals, etc.) as well as of any coaxial, balanced and optical cables and accessories thereof
is excluded.
The reception of television signals inside a building requires an outdoor antenna and a
distribution network to convey the signal to the TV receivers.

60728-6 © IEC:2011(E) – 9 –
CABLE NETWORKS FOR TELEVISION SIGNALS,
SOUND SIGNALS AND INTERACTIVE SERVICES –

Part 6: Optical equipment
1 Scope
This part of IEC 60728 lays down the measuring methods, performance requirements and data
publication requirements of optical equipment of cable networks for television signals, sound
signals and interactive services.
This standard
• applies to all optical transmitters, receivers, amplifiers, directional couplers, isolators,
multiplexing devices, connectors and splices used in cable networks;
• covers the frequency range 5 MHz to 3 000 MHz;
NOTE The upper limit of 3 000 MHz is an example, but not a strict value.
• identifies guaranteed performance requirements for certain parameters;
• lays down data publication requirements with guaranteed performance;
• describes methods of measurement for compliance testing.
All requirements and published data relate to minimum performance levels within the specified
frequency range and in well-matched conditions as might be applicable to cable networks for
television signals, sound signals and interactive services.
2 Normative references
The following referenced documents are indispensable for the application 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 60068-1:1988, Environmental testing – Part 1: General and guidance
IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-6:2007, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-14, Environmental testing – Part 2-14: Tests – Test N: Change of temperature
IEC 60068-2-27, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60068-2-30, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic (12+
12 h cycle)
IEC 60068-2-31, Environmental testing – Part 2-31: Tests – Test Ec: Rough handling shocks,
primarily for equipment-type specimens

– 10 – 60728-6 © IEC:2011(E)
IEC 60068-2-40, Environmental testing – Part 2-40: Tests – Test Z/AM: Combined cold/low air
pressure tests
IEC 60169-24, Radio-frequency connectors – Part 24: Radio-frequency coaxial connectors
with screw coupling, typically for use in 75 ohm cable distribution systems (Type F)
IEC 60417, Graphical symbols for use on equipment
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60617, Graphical symbols for diagrams
IEC 60728-1, Cable networks for television signals, sound signals and interactive services –
Part 1: System performance of forward paths
IEC 60728-2, Cable networks for television signals, sound signals and interactive services –
Part 2: Electromagnetic compatibility for equipment
IEC 60728-3:2010, Cable networks for television signals, sound signals and interactive
services – Part 3: Active wideband equipment for coaxial cable networks
IEC 60728-11, Cable networks for television signals, sound signals and interactive services –
Part 11: Safety
IEC 60728-13:2010, Cable networks for television signals, sound signals and interactive
services – Part 13: Optical systems for broadcast signal transmissions
IEC 60793-2-50:2008, Optical fibres – Part 2-50: Product specifications – Sectional
specification for class B single-mode fibres
IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61280-1-1, Fibre optic communication subsystem basic test procedures – Part 1-1: Test
procedures for general communication subsystems – Transmitter output optical power
measurement for single-mode optical fibre cable
IEC 61280-1-3, Fibre optic communication subsystem basic test procedures – Part 1-3:
General communication subsystems – Central wavelength and spectral width measurement
IEC 61282-4, Fibre optic communication system design guides – Part 4: Accomodation and
utilization of non-linear effects
IEC 61290-1 (all parts), Optical amplifiers – Test methods – Part 1: Power and gain
parameters
IEC 61290-1-3, Optical amplifiers – Test methods – Part 1-3: Power and gain parameters –
Optical power meter method
IEC 61290-3-2:2003, Optical amplifiers – Part 3-2: Test methods for noise figure parameters
– Electrical spectrum analyzer method
IEC 61290-5 (all parts), Optical amplifiers – Test methods – Part 5: Reflectance parameters

60728-6 © IEC:2011(E) – 11 –
IEC 61290-6 (all parts), Optical fibre amplifiers – Basic specification – Part 6: Test methods
for pump leakage parameters
IEC 61290-11 (all parts), Optical amplifiers – Test methods – Part 11: Polarization mode
dispersion parameter
IEC 61291-1, Optical amplifiers – Part 1: Generic specification
IEC 61291-5-2, Optical amplifiers – Part 5-2: Qualification specifications – Reliability
qualification for optical fibre amplifiers
IEC 61300-3-6, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-6: Examinations and measurements – Return loss
IEC 61754-4, Fibre optic connector interfaces – Part 4: Type SC connector family
IEC/TR 61931:1998, Fibre optic – Terminology
IEC 80416 (all parts), Basic principles for graphical symbols for use on equipment
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60728-1,
IEC/TR 61931 and the following apply.
3.1.1
optical transmitting unit
optical transmitter
TX
transmit fibre optic terminal device accepting at its input port an electrical signal and providing
at its output port an optical carrier modulated by that input signal
[IEC/TR 61931:1998, definition 2.9.6]
NOTE For the purposes of this standard, optical transmitters may have more than one input port accepting
electrical RF signals.
3.1.2
optical receiving unit
optical receiver
Rx
receive fibre optic terminal device accepting at its input port a modulated optical carrier, and
providing at its output port the corresponding demodulated electrical signal (with the associated
clock, if digital)
[IEC/TR 61931:1998, definition 2.9.7]
NOTE For the purposes of this standard, optical receivers may have more than one output port providing electrical
RF signals.
– 12 – 60728-6 © IEC:2011(E)
3.1.3
optical amplifier
OA
optical waveguide device containing a suitably pumped, active medium which is able to amplify
an optical signal
[IEC/TR 61931:1998, definition 2.7.75]
3.1.4
(optical) isolator
two port non-reciprocal optical device intended to suppress backward reflection, while having
minimum insertion loss in the forward direction, based on Faraday effect
NOTE 1 An isolator is commonly used to prevent return reflections along a transmission path.
NOTE 2 An isolator is generally polarization dependent; however fibre optic polarization independent isolators exist.
[IEC/TR 61931:1998, definition 2.6.30]
3.1.5
(optical (fibre)) splice
permanent, or semi permanent, joint whose purpose is to couple optical power between two
optical fibres
[IEC 60050-731:1991, 731-05-05, modified] and [IEC/TR 61931:1998, definition 2.6.8]
3.1.6
fibre optic branching device
(optical) (fibre) branching device
(optical) (fibre) coupler (deprecated)]
optical fibre device, possessing three or more optical ports, which shares optical power among
its ports in a predetermined fashion, at the same wavelength or wavelengths, without
wavelength conversion
NOTE The ports may be connected to fibres, sources, detectors, etc.
[IEC/TR 61931:1998, definition 2.6.21]
3.1.7
directional branching device
directional coupler (deprecated)
device which distributes an optical signal among the output ports in a predetermined fashion
only when light is launched into one preselected input port
[IEC/TR 61931:1998, definition 2.6.22]
NOTE For the purposes of this standard, directional coupler is the preferred term because this is also the term for
its electrical equivalent.
3.1.8
multiplexing device
WDM device
wavelength selective branching device (used in WDM transmission systems) in which optical
signals can be transferred between two predetermined ports, depending on the wavelength of
the signal
[IEC/TR 61931:1998, definition 2.6.51]

60728-6 © IEC:2011(E) – 13 –
3.1.9
reference output level of an optical receiver
offset x by which the electrical output level of an optical receiver can be calculated from the
optical input level at a modulation index of m = 0,05 using the following equation:
(1)
U = 2 P + x dB(µV)
opt,RX
where
U
is the electrical output level in dB(µV);

P is the optical input level in dB(mW);
opt,RX
x is the reference output level in dB(µV).
3.1.10
optical modulation index
optical modulation index is defined as

-
φ φ
h l
m =
(2)
φ + φ
h l
where φ is the highest and φ is the lowest instantaneous optical power of the intensity
h l
modulated optical signal
NOTE 1 This term is mainly used for analogue systems.
NOTE 2 This definition does not apply to systems where the input signals are converted and transported as digital
baseband signals. In this case, the terms modulation depth or extinction ratio defined in 2.6.79 and 2.7.46 of
IEC/TR 61931 are used. A test procedure for extinction ratio is described in IEC 61280-2-2.
3.1.11
noise figure
decrease of the signal-to-noise ratio (SNR), at the output of an optical detector with unitary
quantum efficiency, due to the propagation of a shot noise-limited signal through the optical
amplifier (OA), expressed in dB
[IEC 61291-1:2006, definition 3.2.38]
NOTE The noise figure of optical amplifiers depends on the optical input power and on the wavelength used.
3.1.12
relative intensity noise
RIN
ratio of the mean square of the intensity fluctuations in the optical power of a light source to the
square of the mean of the optical output power
−1
NOTE 1 The RIN is usually expressed in dB(Hz ) resulting in negative values.
NOTE 2 The value for the RIN can be calculated from the results of a carrier-to-noise measurement for the system
(see 4.16).
3.1.13
equivalent input noise current density
notional input noise current density which, when applied to the input of an ideal noiseless
device, would produce an output noise current density equal in value to that observed at the
output of the actual device under consideration

– 14 – 60728-6 © IEC:2011(E)
NOTE It can be calculated from the carrier-to-noise ratio C/N (see 4.18) of a device or system using:

C
=
I
r
(3)
C/N
Z
where
C is the power of the carrier at the input of the device or system;
Z is its input impedance.
The equivalent input noise current density is expressed in units of A/√Hz.
3.1.14
responsivity
ratio of an optical detector’s electrical output to its optical input at a given wavelength
[IEC 60050-731:1991, 731-06-36, modified]
NOTE 1 The responsivity is generally expressed in amperes per watt or volts per watt of incident radiant power.
NOTE 2 Sensitivity is sometimes used as an imprecise synonym for responsivity.
NOTE 3 The wavelength interval around the given wavelength may be specified.
[IEC/TR 61931:1998, definition 2.7.56]
3.1.15
chromatic dispersion
total dispersion (deprecated)
spreading of a light pulse per unit source spectrum width in an optical fibre caused by different
group velocities of the different wavelengths composing the source spectrum.
NOTE The chromatic dispersion may be due to the following contributions: material dispersion, waveguide
dispersion, profile dispersion.
[IEC/TR 61931:1998, definition 2.4.54]
3.1.16
wavelength
distance covered in a period by the wavefront of a harmonic plane wave
[IEC/TR 61931:1998, definition 2.2.9]
NOTE 1 The wavelength λ of light in vacuum is given by

c
λ=
(4)
f
where
c
is the speed of light in vacuum (c ≈ 2,997 92 × 10 m/s);
f is the optical frequency.
NOTE 2 Although the wavelength in dielectric material such as fibres is shorter than in vacuum, only the
wavelength of light in vacuum is used.
3.1.17
chirping
rapid change of the emission wavelengths of a directly intensity-modulated optical source as
a function of the intensity of the modulating signal
NOTE 1 Chirping should not be confused with long-term wavelength drift.

60728-6 © IEC:2011(E) – 15 –
NOTE 2 Due to the fibre chromatic dispersion, using a single-mode laser, chirping can cause either degradation or
improvement of the total bandwidth.
[IEC/TR 61931:1998, definition 2.7.44]
3.1.18
polarization
orientation of the electric field vector of the electromagnetic radiation
[IEC/TR 61931:1998, definition 2.1.44]
3.1.19
linewidth
spectral bandwidth of an individual mode of a laser, defined as the difference between those
optical frequencies at which the amplitude reaches or first falls to half of the maximum
amplitude
3.1.20
coherence time
time over which a propagating light may be considered to be coherent radiation
NOTE 1 The coherence time is equal to coherence length divided by the phase velocity of light in a medium.
NOTE 2 The coherence time is given approximately λ /(c⋅∆λ) where λ is the central wavelength, ∆λ is the
0 0
spectral linewidth and c is the velocity of light in vacuum.
[IEC 60050-731:1991, 731-01-18] and [IEC/TR 61931:1998, definition 2.1.68]
3.1.21
amplified spontaneous emission
ASE
optical power associated to spontaneously emitted photons amplified by an active medium in
an optical amplifier
[IEC/TR 61931:1998, definition 2.7.87]
3.1.22
directivity
in a generic optical branching
...

IEC 60728-6 ®
Edition 3.0 2011-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Cable networks for television signals, sound signals and interactive services –
Part 6: Optical equipment
Réseaux de distribution par câbles pour signaux de télévision, signaux de
radiodiffusion sonore et services interactifs –
Partie 6: Matériels optiques
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IEC 60728-6 ®
Edition 3.0 2011-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Cable networks for television signals, sound signals and interactive services –

Part 6: Optical equipment
Réseaux de distribution par câbles pour signaux de télévision, signaux de

radiodiffusion sonore et services interactifs –

Partie 6: Matériels optiques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.060.40; 33.160.99 ISBN 978-2-8322-1036-5

– 2 – IEC 60728-6:2011 © IEC:2011
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, symbols and abbreviations . 11
3.1 Terms and definitions . 11
3.2 Symbols . 18
3.3 Abbreviations . 19
4 Methods of measurement . 20
4.1 Measurement requirements . 20
4.1.1 General . 20
4.1.2 Input specification . 20
4.1.3 Measurement conditions . 20
4.2 Optical power . 21
4.3 Loss, isolation, directivity and coupling ratio . 21
4.3.1 General . 21
4.3.2 Measurement requirements . 21
4.3.3 Principle of measurement . 21
4.4 Return loss . 22
4.5 Saturation output power of an optical amplifier . 22
4.5.1 Purpose . 22
4.5.2 Procedure . 22
4.6 Centroidal wavelength and spectral width under modulation . 23
4.7 Linewidth and chirping of transmitters with single mode lasers . 23
4.7.1 Purpose . 23
4.7.2 Equipment required . 23
4.7.3 General measurement requirements . 23
4.7.4 Procedure . 24
4.7.5 Potential sources of error . 25
4.8 Optical modulation index . 25
4.8.1 Purpose . 25
4.8.2 Equipment required . 25
4.8.3 Procedure . 25
4.8.4 Potential sources of error . 26
4.9 Reference output level of an optical receiver . 26
4.9.1 Purpose . 26
4.9.2 Equipment required . 26
4.9.3 General measurement requirements . 27
4.9.4 Procedure . 27
4.9.5 Potential sources of error . 27
4.10 Slope and flatness . 28
4.10.1 Purpose . 28
4.10.2 Equipment required . 28
4.10.3 Procedure . 28
4.10.4 Potential sources of error . 29

4.11 Composite second order distortion (CSO) of optical transmitters . 29
4.11.1 Purpose . 29
4.11.2 Equipment required . 30
4.11.3 Procedure . 30
4.11.4 Potential sources of error . 30
4.12 Composite triple beats (CTB) of optical transmitters . 30
4.12.1 Purpose . 30
4.12.2 Equipment required . 31
4.12.3 Procedure . 31
4.12.4 Potential sources of error . 31
4.13 Composite crossmodulation of optical transmitters . 31
4.13.1 Purpose . 31
4.13.2 Equipment required . 32
4.13.3 Procedure . 32
4.13.4 Potential sources of error . 34
4.14 Receiver intermodulation . 34
4.14.1 Purpose . 34
4.14.2 Equipment required . 34
4.14.3 General measurement requirements . 35
4.14.4 Procedure . 35
4.14.5 Potential sources of error . 36
4.15 Microscopic gain tilt of optical amplifiers. 36
4.15.1 Purpose . 36
4.15.2 Equipment required . 36
4.15.3 Procedure . 37
4.15.4 Potential sources of error . 38
4.16 Noise parameters of optical transmitters and optical receivers . 38
4.16.1 Purpose . 38
4.16.2 Equipment required . 38
4.16.3 General measurement requirements . 39
4.16.4 Procedure . 40
4.16.5 Relative intensity noise . 42
4.16.6 Equivalent input noise current density . 42
4.16.7 Potential sources of error . 43
4.17 Method for combined measurement of relative intensity noise (RIN), optical
modulation index and equivalent input noise current . 43
4.17.1 Purpose . 43
4.17.2 Equipment required . 43
4.17.3 General measurement conditions . 44
4.17.4 Procedure . 44
4.17.5 Potential sources of error . 45
4.18 Noise figure of optical amplifiers . 45
4.19 Influence of fibre . 45
4.19.1 Purpose . 45
4.19.2 Equipment required . 45
4.19.3 Procedure . 45
4.19.4 Potential sources of error . 46
4.20 SBS threshold . 46

– 4 – IEC 60728-6:2011 © IEC:2011
4.20.1 Purpose . 46
4.20.2 Equipment required . 46
4.20.3 Procedure . 46
4.20.4 Potential sources of error . 47
4.21 Carrier-to-crosstalk ratio (CCR) . 47
4.21.1 Purpose . 47
4.21.2 Equipment required . 47
4.21.3 Procedure . 47
4.21.4 Potential sources of error . 48
5 Universal performance requirements and recommendations . 49
5.1 Safety . 49
5.2 Electromagnetic compatibility (EMC) . 49
5.3 Environmental . 49
5.3.1 Requirements . 49
5.3.2 Storage . 49
5.3.3 Transportation . 49
5.3.4 Installation or maintenance . 49
5.3.5 Operation . 49
5.4 Marking . 50
6 Active equipment . 50
6.1 Optical forward path transmitters . 50
6.1.1 Classification . 50
6.1.2 Data publication requirement . 50
6.1.3 Recommendations . 51
6.1.4 Performance requirements . 51
6.2 Optical return path transmitters . 53
6.2.1 Classification . 53
6.2.2 Data publication requirement . 53
6.2.3 Recommendations . 53
6.2.4 Performance requirements . 54
6.3 Optical receivers . 54
6.3.1 Classification . 54
6.3.2 Data publication requirements . 54
6.3.3 Recommendations . 55
6.3.4 Performance requirements . 55
6.4 Optical amplifiers . 56
6.4.1 Classification . 56
6.4.2 Data publication requirements . 56
6.4.3 Performance requirements . 56
7 Connectors and splices . 57
Annex A (normative) Product specification worksheet for optical amplifiers . 58
Annex B (informative) Calculation of second-order distortion caused by microscopic
gain tilt of optical amplifiers . 59

Figure 1 – Tilt and microscopic gain tilt of optical amplifiers . 17
Figure 2 – Measurement of optical loss, directivity and isolation . 22
Figure 3 – Optical saturation output power . 23

Figure 4 – Measurement of the chirping and the linewidth of transmitters . 24
Figure 5 – Measurement of the optical modulation index . 26
Figure 6 – Measurement of the reference output level of an optical receiver . 27
Figure 7 – Measurement of the slope and flatness . 28
Figure 8 – Evaluation of the slope . 29
Figure 9 – Evaluating the flatness . 29
Figure 10 – Device under test for measuring CSO of optical transmitters . 30
Figure 11 – Device under test for measuring CTB of optical transmitters . 31
Figure 12 – Arrangement for measuring composite crossmodulation of optical
transmitters. 33
Figure 13 – Arrangement of test equipment for measuring receiver intermodulation . 35
Figure 14 – Arrangement of test equipment for measuring microscopic gain tilt . 37
Figure 15 – System with internal noise sources . 38
Figure 16 – PIN diode receiver . 39
Figure 17 – Optical transmission system under test . 40
Figure 18 – Arrangement of test equipment for carrier-to-noise measurement . 40
Figure 19 – Measurement set-up for determination of the noise parameters and the
optical modulation index . 44
Figure 20 – Arrangement for measuring the SBS threshold . 46
Figure 21 – Arrangement for measuring the CCR . 48
Figure 22 – Classification of return path transmitters . 53

Table 1 – Noise correction factors C for different noise level differences D . 42
n
Table 2 – Classes of optical forward path transmitters . 50
Table 3 – Data publication requirements for optical forward path transmitters . 51
Table 4 – Recommendations for optical forward path transmitters . 51
Table 5 – Requirements for optical forward path transmitters . 52
Table 6 – Data publication requirements for optical return path transmitters . 53
Table 7 – Recommendations for optical return path transmitters . 53
Table 8 – Requirements for optical return path transmitters . 54
Table 9 – Classification of optical receivers . 54
Table 10 – Data publication requirements for optical receivers . 55
Table 11 – Recommendations for optical receivers . 55
Table 12 – Performance requirements for optical receivers . 56
Table 13 – Classification of optical amplifiers. 56
Table 14 – Performance requirements for optical amplifiers . 57
Table A.1 – Parameters of optical amplifiers . 58

– 6 – IEC 60728-6:2011 © IEC:2011
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
CABLE NETWORKS FOR TELEVISION SIGNALS,
SOUND SIGNALS AND INTERACTIVE SERVICES –

Part 6: Optical equipment
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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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
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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
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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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.
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
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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 60728-6 has been prepared by technical area 5: Cable networks for
television signals, sound signals and interactive services, of IEC technical committee 100:
Audio, video and multimedia systems and equipment.
This third edition cancels and replaces the second edition published in 2003 of which it
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition.
• The normative references were updated.
• The methods of measurement for optical power and return loss were substituted by
references to other standards.
• The method of measurement for polarization dependent loss was deleted.
• A method of measurement for carrier-to-crosstalk ratio (CCR) was added.

• The methods of measurement for CSO and CTB of optical amplifiers were substituted by a
method of measurement for microscopic gain tilt of optical amplifiers. This parameter can
be used for calculating the second order distortion of optical amplifiers according to the
method described in the new Annex B.
• New classes for optical transmitters and receivers have been defined.
The text of this standard is based on the following documents:
CDV Report on voting
100/1654/CDV 100/1789/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.
The list of all the parts of the IEC 60728 series, under the general title Cable networks for
television signals, sound signals and interactive services, 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.
– 8 – IEC 60728-6:2011 © IEC:2011
INTRODUCTION
Standards of the IEC 60728 series deal with cable networks including equipment and
associated methods of measurement for headend reception, processing and distribution of
television signals, sound signals and their associated data signals and for processing,
interfacing and transmitting all kinds of signals for interactive services using all applicable
transmission media.
• This covers all kinds of networks that convey modulated RF carriers such as CATV-networks;
• MATV-networks and SMATV-networks;
• individual receiving networks;
and all kinds of equipment, systems and installations installed in such networks.
NOTE CATV encompasses the Hybrid Fibre Coaxial (HFC) networks used nowadays to provide telecommunications
services, voice, data and audio and video both broadcast and narrowcast.
The extent of this standardisation work is from the antennas and/or special signal source inputs
to the headend or other interface points to the network up to the terminal input.
The standardisation of any user terminals (i.e. tuners, receivers, decoders, multimedia
terminals, etc.) as well as of any coaxial, balanced and optical cables and accessories thereof
is excluded.
The reception of television signals inside a building requires an outdoor antenna and a
distribution network to convey the signal to the TV receivers.

CABLE NETWORKS FOR TELEVISION SIGNALS,
SOUND SIGNALS AND INTERACTIVE SERVICES –

Part 6: Optical equipment
1 Scope
This part of IEC 60728 lays down the measuring methods, performance requirements and data
publication requirements of optical equipment of cable networks for television signals, sound
signals and interactive services.
This standard
• applies to all optical transmitters, receivers, amplifiers, directional couplers, isolators,
multiplexing devices, connectors and splices used in cable networks;
• covers the frequency range 5 MHz to 3 000 MHz;
NOTE The upper limit of 3 000 MHz is an example, but not a strict value.
• identifies guaranteed performance requirements for certain parameters;
• lays down data publication requirements with guaranteed performance;
• describes methods of measurement for compliance testing.
All requirements and published data relate to minimum performance levels within the specified
frequency range and in well-matched conditions as might be applicable to cable networks for
television signals, sound signals and interactive services.
2 Normative references
The following referenced documents are indispensable for the application 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 60068-1:1988, Environmental testing – Part 1: General and guidance
IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-6:2007, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-14, Environmental testing – Part 2-14: Tests – Test N: Change of temperature
IEC 60068-2-27, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60068-2-30, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic (12+
12 h cycle)
IEC 60068-2-31, Environmental testing – Part 2-31: Tests – Test Ec: Rough handling shocks,
primarily for equipment-type specimens

– 10 – IEC 60728-6:2011 © IEC:2011
IEC 60068-2-40, Environmental testing – Part 2-40: Tests – Test Z/AM: Combined cold/low
air pressure tests
IEC 60169-24, Radio-frequency connectors – Part 24: Radio-frequency coaxial connectors
with screw coupling, typically for use in 75 ohm cable distribution systems (Type F)
IEC 60417, Graphical symbols for use on equipment
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60617, Graphical symbols for diagrams
IEC 60728-1, Cable networks for television signals, sound signals and interactive services –
Part 1: System performance of forward paths
IEC 60728-2, Cable networks for television signals, sound signals and interactive services –
Part 2: Electromagnetic compatibility for equipment
IEC 60728-3:2010, Cable networks for television signals, sound signals and interactive
services – Part 3: Active wideband equipment for coaxial cable networks
IEC 60728-11, Cable networks for television signals, sound signals and interactive services –
Part 11: Safety
IEC 60728-13:2010, Cable networks for television signals, sound signals and interactive
services – Part 13: Optical systems for broadcast signal transmissions
IEC 60793-2-50:2008, Optical fibres – Part 2-50: Product specifications – Sectional
specification for class B single-mode fibres
IEC 60825-1, Safety of laser products – Part 1: Equipment classification and requirements
IEC 61280-1-1, Fibre optic communication subsystem basic test procedures – Part 1-1: Test
procedures for general communication subsystems – Transmitter output optical power
measurement for single-mode optical fibre cable
IEC 61280-1-3, Fibre optic communication subsystem basic test procedures – Part 1-3:
General communication subsystems – Central wavelength and spectral width measurement
IEC 61282-4, Fibre optic communication system design guides – Part 4: Accomodation and
utilization of non-linear effects
IEC 61290-1 (all parts), Optical amplifiers – Test methods – Part 1: Power and gain
parameters
IEC 61290-1-3, Optical amplifiers – Test methods – Part 1-3: Power and gain parameters –
Optical power meter method
IEC 61290-3-2:2003, Optical amplifiers – Part 3-2: Test methods for noise figure parameters
– Electrical spectrum analyzer method
IEC 61290-5 (all parts), Optical amplifiers – Test methods – Part 5: Reflectance parameters

IEC 61290-6 (all parts), Optical fibre amplifiers – Basic specification – Part 6: Test methods
for pump leakage parameters
IEC 61290-11 (all parts), Optical amplifiers – Test methods – Part 11: Polarization mode
dispersion parameter
IEC 61291-1, Optical amplifiers – Part 1: Generic specification
IEC 61291-5-2, Optical amplifiers – Part 5-2: Qualification specifications – Reliability
qualification for optical fibre amplifiers
IEC 61300-3-6, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-6: Examinations and measurements – Return loss
IEC 61754-4, Fibre optic connector interfaces – Part 4: Type SC connector family
IEC/TR 61931:1998, Fibre optic – Terminology
IEC 80416 (all parts), Basic principles for graphical symbols for use on equipment
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60728-1,
IEC/TR 61931 and the following apply.
3.1.1
optical transmitting unit
optical transmitter
TX
transmit fibre optic terminal device accepting at its input port an electrical signal and providing
at its output port an optical carrier modulated by that input signal
[IEC/TR 61931:1998, definition 2.9.6]
NOTE For the purposes of this standard, optical transmitters may have more than one input port accepting electrical
RF signals.
3.1.2
optical receiving unit
optical receiver
Rx
receive fibre optic terminal device accepting at its input port a modulated optical carrier, and
providing at its output port the corresponding demodulated electrical signal (with the associated
clock, if digital)
[IEC/TR 61931:1998, definition 2.9.7]
NOTE For the purposes of this standard, optical receivers may have more than one output port providing electrical
RF signals.
– 12 – IEC 60728-6:2011 © IEC:2011
3.1.3
optical amplifier
OA
optical waveguide device containing a suitably pumped, active medium which is able to amplify
an optical signal
[IEC/TR 61931:1998, definition 2.7.75]
3.1.4
(optical) isolator
two port non-reciprocal optical device intended to suppress backward reflection, while having
minimum insertion loss in the forward direction, based on Faraday effect
NOTE 1 An isolator is commonly used to prevent return reflections along a transmission path.
NOTE 2 An isolator is generally polarization dependent; however fibre optic polarization independent isolators exist.
[IEC/TR 61931:1998, definition 2.6.30]
3.1.5
(optical (fibre)) splice
permanent, or semi permanent, joint whose purpose is to couple optical power between two
optical fibres
[IEC 60050-731:1991, 731-05-05, modified] and [IEC/TR 61931:1998, definition 2.6.8]
3.1.6
fibre optic branching device
(optical) (fibre) branching device
(optical) (fibre) coupler (deprecated)]
optical fibre device, possessing three or more optical ports, which shares optical power among
its ports in a predetermined fashion, at the same wavelength or wavelengths, without
wavelength conversion
NOTE The ports may be connected to fibres, sources, detectors, etc.
[IEC/TR 61931:1998, definition 2.6.21]
3.1.7
directional branching device
directional coupler (deprecated)
device which distributes an optical signal among the output ports in a predetermined fashion
only when light is launched into one preselected input port
[IEC/TR 61931:1998, definition 2.6.22]
NOTE For the purposes of this standard, directional coupler is the preferred term because this is also the term for
its electrical equivalent.
3.1.8
multiplexing device
WDM device
wavelength selective branching device (used in WDM transmission systems) in which optical
signals can be transferred between two predetermined ports, depending on the wavelength of
the signal
[IEC/TR 61931:1998, definition 2.6.51]

3.1.9
reference output level of an optical receiver
offset x by which the electrical output level of an optical receiver can be calculated from the
optical input level at a modulation index of m = 0,05 using the following equation:
(1)
U = 2 P + x dB(µV)
opt,RX
where
U
is the electrical output level in dB(µV);

P is the optical input level in dB(mW);
opt,RX
x
is the reference output level in dB(µV).
3.1.10
optical modulation index
optical modulation index is defined as

-
φ φ
h l
m =
(2)
φ + φ
h l
where φ is the highest and φ is the lowest instantaneous optical power of the intensity
h l
modulated optical signal
NOTE 1 This term is mainly used for analogue systems.
NOTE 2 This definition does not apply to systems where the input signals are converted and transported as digital
baseband signals. In this case, the terms modulation depth or extinction ratio defined in 2.6.79 and 2.7.46 of IEC/TR
61931 are used. A test procedure for extinction ratio is described in IEC 61280-2-2.
3.1.11
noise figure
decrease of the signal-to-noise ratio (SNR), at the output of an optical detector with unitary
quantum efficiency, due to the propagation of a shot noise-limited signal through the optical
amplifier (OA), expressed in dB
[IEC 61291-1:2006, definition 3.2.38]
NOTE The noise figure of optical amplifiers depends on the optical input power and on the wavelength used.
3.1.12
relative intensity noise
RIN
ratio of the mean square of the intensity fluctuations in the optical power of a light source to the
square of the mean of the optical output power
−1
NOTE 1 The RIN is usually expressed in dB(Hz ) resulting in negative values.
NOTE 2 The value for the RIN can be calculated from the results of a carrier-to-noise measurement for the system
(see 4.16).
3.1.13
equivalent input noise current density
notional input noise current density which, when applied to the input of an ideal noiseless device,
would produce an output noise current density equal in value to that observed at the output of
the actual device under consideration

– 14 – IEC 60728-6:2011 © IEC:2011
NOTE It can be calculated from the carrier-to-noise ratio C/N (see 4.18) of a device or system using:

C
=
I
r
(3)
C/N
Z
where
C is the power of the carrier at the input of the device or system;
Z is its input impedance.
The equivalent
...