IEC 60728-106:2023

Cable networks for television signals, sound signals and interactive services - Part 106: Optical equipment for systems loaded with digital channels only

IEC 60728-106:2023 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 loaded with digital channels only.
This document
• 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 3 300 MHz;
• 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.

Réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonores et services interactifs – Partie 106: Matériel optique pour systèmes soumis à une charge de porteuses exclusivement numériques

L'IEC 60728-106:2023 définit les méthodes de mesurage, les exigences de performance et les exigences de publication des données des matériels optiques des réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonore et services interactifs soumis à une charge de porteuses exclusivement numériques.
Le présent document:
- s'applique à l'ensemble des émetteurs, récepteurs, amplificateurs, coupleurs directifs, isolateurs, multiplexeurs, connecteurs et épissures optiques, utilisés dans les réseaux de distribution par câbles;
- couvre la plage de fréquences de 5 MHz à 3 300 MHz;
- identifie les exigences de performances assurées pour certains paramètres;
- établit les exigences de publication des données avec les performances assurées;
- décrit les méthodes de mesurage pour les essais de conformité.
Toutes les exigences et données publiées se rapportent aux niveaux de performance minimale dans la plage de fréquences spécifiée et dans des conditions bien adaptées qui peuvent s'appliquer aux réseaux de distribution par câbles pour signaux de télévision, signaux de radiodiffusion sonore et services interactifs.

General Information

• Status: Published
• Publication Date: 29-May-2023
• ICS: 33.060.40 - Cabled distribution systems
• Technical Committee: TA 5 - Cable networks for television signals, sound signals and interactive services
• Drafting Committee: WG 5 - TC 100/TA 5/WG 5
• Current Stage: PPUB - Publication issued
• Start Date: 30-May-2023
• Completion Date: 23-Jun-2023

Overview

IEC 60728-106:2023 is an international standard published by the International Electrotechnical Commission (IEC) focusing on optical equipment for cable networks that handle exclusively digital channels. This standard is part 106 of the IEC 60728 series, which covers cable networks for television signals, sound signals, and interactive services.

The standard details the measuring methods, performance requirements, and data publication mandates for optical components such as transmitters, receivers, amplifiers, couplers, isolators, multiplexers, connectors, and splices used in these cable networks. It covers the frequency range from 5 MHz to 3 300 MHz and establishes minimum guaranteed performance levels to ensure consistent and reliable network operation under well-matched conditions.

By adhering to IEC 60728-106:2023, manufacturers and operators can ensure high-quality optical equipment performance, promoting interoperability and supporting the efficient delivery of digital television, audio, and interactive services via cable.

---

Key Topics

• Scope and Applicability
  Applies exclusively to digital channel-loaded cable networks and the optical equipment therein, encompassing active and passive devices.

• Measurement Methods
  Defines precise test procedures for critical parameters such as optical power, loss, isolation, return loss, saturation output power, spectral characteristics, modulation index, non-linearity, and noise parameters.

• Performance Requirements
  Specifies minimum guaranteed levels for factors including:

  • Optical transmitter and receiver performance
  • Amplifier gain, noise figure, and saturation level
  • Coupling ratio, directivity, and isolation of passive components
  • Signal-to-crosstalk ratio and intermodulation distortion

• Data Publication
  Mandates transparent reporting of guaranteed performance data by manufacturers to facilitate informed selection and compliance verification.

• Safety, Electromagnetic Compatibility (EMC), and Environmental Recommendations
  Includes general guidelines to ensure equipment reliability and safe operation within cable networks.

---

Applications

IEC 60728-106:2023 plays a crucial role in the design, testing, and deployment of cable network infrastructure delivering digital television and audio services. Its practical applications include:

• Cable Network Equipment Manufacturing
  Providing manufacturers with standardized criteria for the development and quality assurance of optical transmitters, receivers, amplifiers, and passive optical components.

• Network Operators and Service Providers
  Assisting in selecting compliant optical equipment to maintain high signal quality and service reliability in digital cable networks.

• Testing and Certification Laboratories
  Guiding testing methodologies to verify compliance with performance standards, ensuring optical devices meet minimum required levels.

• Installation and Maintenance
  Offering benchmarks for installation practices and ongoing equipment performance monitoring to uphold network integrity.

Keywords such as optical cable networks, digital channel equipment, optical transmitters and receivers, and performance measurement are integral for companies optimizing their digital cable infrastructures.

---

Related Standards

IEC 60728-106:2023 is part of the broader IEC 60728 series, which addresses cable networks for television, sound, and interactive services. Related standards include:

• IEC 60728-1 to IEC 60728-5: Addressing coaxial and hybrid optical/coaxial cable systems supporting analog and digital signals.

• IEC 60728-109: Optical equipment performance for hybrid fiber-coaxial networks with both digital and analog channels.

• IEC 60728-10x series: Covering measurement methods and performance for other cable network equipment components.

Additionally, compliance with international EMC and safety standards such as IEC 61000 series may be necessary to satisfy operational requirements.

---

IEC 60728-106:2023 facilitates high-performance, reliable optical transmission in digital cable networks, supporting efficient delivery of television, sound, and interactive services aligned with modern digital broadcasting demands.

Standards Content (Sample)

IEC 60728-106 ®
Edition 1.0 2023-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Cable networks for television signals, sound signals and interactive services –
Part 106: Optical equipment for systems loaded with digital channels only

Réseaux de distribution par câbles pour signaux de télévision, signaux de
radiodiffusion sonore et services interactifs –
Partie 106: Matériel optique pour systèmes soumis à une charge de porteuses
exclusivement numériques
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IEC 60728-106 ®
Edition 1.0 2023-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Cable networks for television signals, sound signals and interactive services –

Part 106: Optical equipment for systems loaded with digital channels only

Réseaux de distribution par câbles pour signaux de télévision, signaux de

radiodiffusion sonore et services interactifs –

Partie 106: Matériel optique pour systèmes soumis à une charge de porteuses

exclusivement numériques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.060.40  ISBN 978-2-8322-7053-0

– 2 – IEC 60728-106:2023 © IEC 2023
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions, graphical symbols and abbreviated terms. 9
3.1 Terms and definitions . 9
3.2 Graphical symbols . 16
3.3 Abbreviated terms . 18
4 Methods of measurement . 19
4.1 Measurement requirements . 19
4.1.1 General . 19
4.1.2 Input specification . 19
4.1.3 Measurement conditions . 19
4.2 Optical power . 19
4.3 Loss, isolation, directivity and coupling ratio . 19
4.3.1 General . 19
4.3.2 Measurement requirements . 19
4.3.3 Measurement procedure . 20
4.4 Return loss . 20
4.5 Saturation output power of an optical amplifier . 20
4.5.1 Purpose . 20
4.5.2 Measurement procedure . 21
4.6 Centroidal wavelength and spectral width under modulation. 21
4.7 Linewidth and chirping of transmitters with single mode lasers . 21
4.7.1 Purpose . 21
4.7.2 Equipment required . 21
4.7.3 General measurement requirements . 22
4.7.4 Measurement procedure . 22
4.7.5 Potential sources of error . 23
4.8 Optical modulation index . 23
4.8.1 Purpose . 23
4.8.2 Equipment required . 23
4.8.3 Measurement procedure . 23
4.8.4 Potential sources of error . 24
4.9 Reference output level of an optical receiver . 24
4.9.1 Purpose . 24
4.9.2 Equipment required . 25
4.9.3 General measurement requirements . 25
4.9.4 Measurement procedure . 25
4.9.5 Potential sources of error . 25
4.10 Slope and flatness . 26
4.10.1 Purpose . 26
4.10.2 Equipment required . 26
4.10.3 Measurement procedure . 26
4.10.4 Potential sources of error . 27
4.11 Transmitter non-linearity . 27
4.11.1 Purpose . 27

4.11.2 Equipment required . 28
4.11.3 Measurement procedure . 28
4.11.4 Potential sources of error . 28
4.12 Receiver intermodulation . 29
4.12.1 Purpose . 29
4.12.2 Equipment required . 29
4.12.3 General measurement requirements . 29
4.12.4 Measurement procedure . 29
4.12.5 Potential sources of error . 31
4.13 Microscopic gain tilt of optical amplifiers . 31
4.13.1 Purpose . 31
4.13.2 Equipment required . 31
4.13.3 Measurement procedure . 31
4.13.4 Potential sources of error . 32
4.14 Noise parameters of optical transmitters and optical receivers . 32
4.14.1 Purpose . 32
4.14.2 Equipment required . 33
4.14.3 General measurement requirements . 34
4.14.4 Measurement procedure . 34
4.14.5 Relative intensity noise . 37
4.14.6 Equivalent input noise current density . 37
4.14.7 Potential sources of error . 38
4.15 Method for combined measurement of relative intensity noise (RIN), optical

modulation index and equivalent input noise current . 38
4.15.1 Purpose . 38
4.15.2 Equipment required . 38
4.15.3 General measurement conditions . 39
4.15.4 Measurement procedure . 39
4.15.5 Potential sources of error . 40
4.16 Noise figure of optical amplifiers . 40
4.17 Influence of fibre . 40
4.17.1 Purpose . 40
4.17.2 Equipment required . 40
4.17.3 Measurement procedure . 40
4.17.4 Potential sources of error . 40
4.18 SBS threshold . 40
4.18.1 Purpose . 40
4.18.2 Equipment required . 41
4.18.3 Measurement procedure . 41
4.18.4 Potential sources of error . 41
4.19 Signal-to-crosstalk ratio (SCR) . 41
4.19.1 Purpose . 41
4.19.2 Equipment required . 42
4.19.3 Measurement procedure . 42
4.19.4 Potential sources of error . 43
5 Universal performance requirements and recommendations . 43
5.1 Safety . 43
5.2 Electromagnetic compatibility (EMC) . 43
5.3 Environmental . 43

– 4 – IEC 60728-106:2023 © IEC 2023
5.4 Marking . 43
6 Active equipment . 43
6.1 Optical transmitters . 43
6.1.1 Data publication requirement . 43
6.1.2 Recommendations . 44
6.2 Optical receivers . 44
6.2.1 Data publication requirements . 44
6.2.2 Recommendations . 44
6.3 Optical amplifiers . 45
6.3.1 Data publication requirements . 45
6.3.2 Recommendations for optical amplifiers . 45
7 Passive equipment . 46
Bibliography . 47

Figure 1 – Tilt and microscopic gain tilt of optical amplifiers . 12
Figure 2 – Measurement of optical loss, directivity, isolation and coupling ratio . 20
Figure 3 – Saturation output power of an optical amplifier . 21
Figure 4 – Measurement of the chirping and the linewidth of transmitters. 22
Figure 5 – Measurement of the optical modulation index . 24
Figure 6 – Measurement of the reference output level of an optical receiver . 25
Figure 7 – Measurement of the slope and flatness . 26
Figure 8 – Evaluation of the slope . 27
Figure 9 – Evaluating the flatness . 27
Figure 10 – Equipment under test (EUT) for measuring non-linearity of optical
transmitters . 28
Figure 11 – Arrangement of test equipment for measuring receiver intermodulation . 30
Figure 12 – Arrangement of test equipment for measuring microscopic gain tilt. 31
Figure 13 – System with internal noise sources . 32
Figure 14 – PIN diode receiver. 33
Figure 15 – Optical transmission system under test . 34
Figure 16 – Arrangement of test equipment for RF signal-to-noise ratio measurement . 35
Figure 17 – Measurement set-up for determination of the noise parameters and the
optical modulation index . 39
Figure 18 – Arrangement for measuring the SBS threshold . 41
Figure 19 – Arrangement for measuring the SCR . 42

Table 1 – Noise correction factors C for different noise level differences D . 36
n
Table 2 – Recommendations for optical forward path transmitters . 44
Table 3 – Recommendations for optical return path transmitters . 44
Table 4 – Recommendations for optical receivers . 45
Table 5 – Parameters of optical amplifiers . 45
Table 6 – Recommendations for optical amplifiers . 46

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CABLE NETWORKS FOR TELEVISION SIGNALS,
SOUND SIGNALS AND INTERACTIVE SERVICES –

Part 106: Optical equipment for systems loaded with digital channels only

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,
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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
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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 60728-106 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. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
100/3899/FDIS 100/3923/RVD
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 International Standard is English.

– 6 – IEC 60728-106:2023 © IEC 2023
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.
A list of all parts in the IEC 60728 series, published 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 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.
INTRODUCTION
International Standards and other deliverables of the IEC 60728 series deal with cable networks,
including equipment and associated methods of measurement for headend reception,
processing and distribution of television and sound signals and for processing, interfacing and
transmitting all kinds of data signals for interactive services using all applicable transmission
media. These signals are typically transmitted in networks by frequency-multiplexing techniques.
This includes, for instance:
• regional and local broadband cable networks,
• extended satellite and terrestrial television distribution systems,
• individual satellite and terrestrial television receiving systems,
and all kinds of equipment, systems and installations used in such cable networks, distribution
and receiving systems.
The extent of this standardization work ranges from antennas and/or special interfaces to
headends, or other interface points on the network up to any terminal interface of the equipment
on the customer's premises.
The standardization work will consider coexistence with users of the RF spectrum in wired and
wireless transmission systems.
The standardization of any user terminals (i.e. tuners, receivers, decoders, multimedia terminals)
as well as of any coaxial, balanced and optical cables and accessories thereof is excluded.

– 8 – IEC 60728-106:2023 © IEC 2023
CABLE NETWORKS FOR TELEVISION SIGNALS,
SOUND SIGNALS AND INTERACTIVE SERVICES –

Part 106: Optical equipment for systems loaded with digital channels only

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 loaded with digital channels only.
This document
• 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 3 300 MHz;
NOTE The upper limit of 3 300 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 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 60068-2 (all parts), Environmental testing
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60728-101, Cable networks for television signals, sound signals and interactive services –
Part 101: System performance of forward paths loaded with digital channels only
IEC 60728-3:2017, Cable networks for television signals, sound signals and interactive services
– Part 3: Active wideband equipment for cable networks
IEC 60728-11, Cable networks for television signals, sound signals and interactive services –
Part 11: Safety
IEC 60793-2-50, 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 test procedures – Part 1-3: General
communication subsystems – Measurement of central wavelength, spectral width and additional
spectral characteristics
IEC 61290-1 (all parts), Optical amplifiers – Test methods – Part 1: Power and gain parameters
IEC 61290-3-2:2008, Optical amplifiers – Test methods – Part 3-2: Noise figure parameters –
Electrical spectrum analyser method
IEC 61290-5 (all parts), Optical amplifiers – Test methods – Part 5: Reflectance parameters
IEC 61290-6-1, Optical fibre amplifiers – Basic specification – Part 6-1: Test methods for pump
leakage parameters – Optical demultiplexer
IEC 61290-11 (all parts), Optical amplifiers – Test methods – Part 11: Polarization mode
dispersion parameter
IEC 61300-3-6, Fibre optic interconnecting devices and passive components – Basic test and
measurement procedures – Part 3-6: Examinations and measurements – Return loss
3 Terms, definitions, graphical symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions 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
amplified spontaneous emission
ASE
optical power associated to spontaneously emitted photons amplified by an active medium in
an optical amplifier
[SOURCE: IEC TR 61931:1998, 2.7.87]
3.1.2
stimulated Brillouin scattering
SBS
non-linear scattering of optical radiation characterized by a frequency shift as for the Raman
scattering, but accompanied by a lower frequency (acoustical) vibration of the medium lattice
Note 1 to entry: The light is scattered backward with respect to the incident radiation.
Note 2 to entry: In silica fibres, the frequency shift is typically around 10 GHz.
[SOURCE: IEC TR 61931:1998, 2.1.88, modified – The term and definition have been altered
to comply with the latest version of the ISO/IEC Directives, Part 2.]

– 10 – IEC 60728-106:2023 © IEC 2023
3.1.3
centroidal wavelength
mean or average wavelength of an optical spectrum
Note 1 to entry: Other spectral wavelengths are central wavelengths, half-power wavelengths, and peak
wavelengths
3.1.4
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 to entry: Chirping should not be confused with long-term wavelength drift.
Note 2 to entry: Due to the fibre chromatic dispersion, using a single-mode laser, chirping can cause either
degradation or improvement of the total bandwidth.
[SOURCE: IEC TR 61931:1998, 2.7.44]
3.1.5
chromatic dispersion
DEPRECATED: total dispersion
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 1 to entry: The chromatic dispersion may be due to the following contributions: material dispersion, waveguide
dispersion, profile dispersion.
[SOURCE: IEC TR 61931:1998, 2.4.54]
3.1.6
cladding mode
mode in which the electromagnetic field is confined in the cladding and the core by virtue of
there being a lower refractive index medium surrounding the outermost cladding
[SOURCE: IEC 60050-731:1991, 731-03-60]
3.1.7
coherence time
time over which a propagating light can be considered to be coherent radiation
Note 1 to entry: The coherence time is equal to coherence length divided by the phase velocity of light in a medium.
Note 2 to entry: 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.
3.1.8
directional coupler
directional branching device
device which distributes an optical signal among the output ports in a predetermined fashion
only when light is launched into one preselected input port
Note 1 to entry: For the purposes of this document, directional coupler is the preferred term because this is also
the term for its electrical equivalent.
[SOURCE: IEC TR 61931:1998, 2.6.22, modified – "directional coupler" given preferred term
status instead of deprecated status, and Note 1 to entry has been added.]

3.1.9
directivity
the ratio, usually expressed in decibels, of the power output measured at the appropriate port
of one of the transmission lines of a directional coupler, when power is fed into the other
transmission line in the preferred direction, to the power output measured at the same place
when the same power is fed into the same line in the opposite direction, matched terminations
being connected to all ports
[SOURCE: IEC 60050-726:1982, 726-14-03]
3.1.10
equivalent input noise current density
notional input noise current density which, when applied to the input of an ideal noiseless
device, produces an output noise current density equal in value to that observed at the output
of the actual device under consideration
Note 1 to entry: It can be calculated from the RF signal-to-noise ratio (see 4.14).
3.1.11
fibre optic branching device
optical fibre branching device
DEPRECATED: optical fibre coupler
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 1 to entry: The ports may be connected to fibres, sources, detectors, etc.
[SOURCE: IEC TR 61931:1998, 2.6.21]
3.1.12
flatness
difference between the maximum and the minimum gain or attenuation reduced by the slope
within the specified modulation frequency range of a device or system
3.1.13
optical isolator
isolator
two port non-reciprocal optical device intended to suppress backward reflection, while having
minimum insertion loss in the forward direction, based on the Faraday effect
Note 1 to entry: An isolator is commonly used to prevent return reflections along a transmission path.
Note 2 to entry: An isolator is generally polarization dependent; however, fibre optic polarization-independent
isolators exist.
[SOURCE: IEC TR 61931:1998, 2.6.30]
3.1.14
microscopic gain tilt
slope due to ripples in sub-nanometre intervals in the gain-versus-wavelength characteristic in
the specified wavelength range of optical amplifiers (see Figure 1)

– 12 – IEC 60728-106:2023 © IEC 2023

Figure 1 – Tilt and microscopic gain tilt of optical amplifiers
3.1.15
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
[SOURCE: IEC TR 61931:1998, 2.6.51]
3.1.16
noise figure
NF
decrease of the signal-to-noise ratio (SNR), at the output of an optical detector with unitary
quantum efficiency and zero excess noise, due to the propagation of a shot noise-limited signal
through the optical amplifier (OA)
Note 1 to entry: The operating conditions at which the noise figure is specified should be stated, especially since it
depends on the optical input power and on the wavelength used.
Note 2 to entry: This property can be described as a discrete wavelength or as a function of wavelength.
Note 3 to entry: The noise degradation due to the OA, is attributable to different factors, for example signal-
spontaneous beat noise, spontaneous-spontaneous beat noise, internal reflections noise, signal shot noise,
spontaneous shot noise. Each of these factors depends on various conditions which should be specified for a correct
evaluation of the noise figure.
Note 4 to entry: By convention, this noise figure is a positive number.
Note 5 to entry: In the case of OAs for analogue applications, the noise figure also represents the ratio between
input and the output RF signal-to-noise ratios.
Note 6 to entry: Noise figure is expressed in dB.
3.1.17
optical amplifier
OA
optical waveguide device containing a suitably pumped, active medium which is able to amplify
an optical signal
[SOURCE: IEC TR 61931:1998, 2.7.75]

3.1.18
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)
Note 1 to entry: For the purposes of this document, optical receivers can have more than one output port providing
electrical RF signals.
[SOURCE: IEC TR 61931:1998, 2.9.7, modified – Note 1 to entry has been added.]
3.1.19
optical return loss
return loss
ORL
ratio, expressed in dB, of the total reflected power to the incident power from an optical fibre,
optical device, or optical system, and defined as Equation (1):
P
r
−10lg
(1)
P
i
where
P is the reflected power;
r
P is the incident power.
i
Note 1 to entry: When referring to a reflected power from an individual component, "reflectance" is the preferred
term.
Note 2 to entry: For the purposes of this document, the term "reflectance" is used for optical amplifiers only. The
term “optical return loss” is used for ports of all other types of equipment.
Note 3 to entry: The term "return loss" is also used for electrical ports. The definition relates to electrical powers in
this case.
[SOURCE: IEC TR 61931:1998, 2.6.49, modified – Notes 2 and 3 to entry have been added.]
3.1.20
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
Note 1 to entry: For the purposes of this document, optical transmitters can have more than one input port accepting
electrical RF signals.
[SOURCE: IEC TR 61931:1998, 2.9.6, modified – Note 1 to entry has been added.]
3.1.21
polarization
orientation of the electric field vector of the electromagnetic radiation
[SOURCE: IEC TR 61931:1998, 2.1.44]

– 14 – IEC 60728-106:2023 © IEC 2023
3.1.22
optical modulation index
optical modulation index m is defined as Equation (2):
φφ−
hl
m =
(2)
k
φφ+
hl
where
φ is the highest instantaneous optical power of the intensity modulated optical signal
h
φ is the lowest instantaneous optical power of the intensity modulated optical signal
l
Note 1 to entry: 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 61931:1998 are used. A test procedure for extinction ratio is described in IEC 61280-2-2.
[SOURCE: IEC 60728-6:2011, 3.1.10, modified – The definition has been clarified and Notes 1
and 2 to entry have been replaced by a new Note 1 to entry.]
3.1.23
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 (3):
U = 2 P + x dB(μV)
(3)
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)
3.1.24
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 to entry: The RIN is usually expressed in dB(Hz ), resulting in negative values.
Note 2 to entry: The value for the RIN can be calculated from the results of a RF signal-to-noise ratio measurement
for the system (see 4.15).
3.1.25
responsivity
ratio of an optical detector’s electrical output to its optical input at a given wavelength
Note 1 to entry: The responsivity is generally expressed in amperes per watt or volts per watt of incident radiant
power.
Note 2 to entry: "Sensitivity" is sometimes used as an imprecise synonym for responsivity.
Note 3 to entry: The wavelength interval around the given wavelength can be specified.
[SOURCE: IEC TR 61931:1998, 2.7.56]

3.1.26
RF signal-to-noise ratio
SNR
signal-to-noise ratio for a digitally modulated signal in the RF band
[SOURCE: IEC 60728-1:2014, 3.1.80, modified – The term has been replaced.]
3.1.27
saturation output power
gain compression power
optical power level associated with the output signal above which the gain i
...