EN IEC 61281-1:2018

Fibre optic communication subsystems - Part 1: Generic specification

IEC 61281-1:2017 is a generic specification for fibre optic communication subsystems (FOCSs). The parameters defined herein form a specifiable minimum set of specifications that are common to all fibre optic subsystems. Additional parameters can be used depending on the particular application and technology. Those additional parameters will be specified in the relevant documents, as appropriate. Each specified parameter is measured using one of the test procedures. The use of these parameters for system design is given in design guides. This second edition cancels and replaces the first edition published in 1999. This edition constitutes a technical revision. This edition includes the following significant technical change with respect to the previous edition: addition of new definitions. Keywords: fibre optic communication subsystems (FOCSs)

Lichtwellenleiter-Kommunikationsuntersysteme - Teil 1: Fachgrundspezifikation

Sous-systèmes de télécommunications fibroniques - Partie 1: Spécification générique

IEC 61281-1:2017 est une spécification générique relative aux sous-systèmes de télécommunications fibroniques (FOCS, fibre optic communication subsystem). Les paramètres définis dans le présent document constituent un ensemble minimal de spécifications, communes à tous les sous-systèmes fibroniques. Des paramètres supplémentaires peuvent être utilisés, selon les spécificités de l'application et des technologies. Ces paramètres supplémentaires seront spécifiés dans les documents appropriés, suivant le cas. Chaque paramètre spécifié est mesuré au moyen de l'un des modes opératoires d'essai. L'utilisation de ces paramètres pour la conception de systèmes est décrite dans les guides de conception. Cette deuxième édition annule et remplace la première édition parue en 1999. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: ajout de nouvelles définitions. Mots clés : sous-systèmes de télécommunications fibroniques (FOCS, fibre optic communication subsystem)

Optični komunikacijski podsistemi - 1. del: Splošna specifikacija (IEC 61281-1:2017)

Ta del standarda IEC 61281 je splošna specifikacija za komunikacijske podsisteme optičnih vlaken (FOCS).
Tu določeni parametri predstavljajo določen minimalni sklop specifikacij, ki so skupne vsem podsistemom optičnih vlaken. Glede na posamezno uporabo in tehnologijo lahko uporabite dodatne parametre. Ti dodatni parametri bodo ustrezno določeni v zadevnih dokumentih.
Vsak od določenih parametrov bo izmerjen s pomočjo enega od preskusnih postopkov. Uporaba teh parametrov za oblikovanje sistema je podana v smernicah za oblikovanje.

General Information

• Status: Published
• Publication Date: 08-Mar-2018
• Withdrawal Date: 18-Jan-2021
• ICS: 33.180.01 - Fibre optic systems in general
• Technical Committee: CLC/SR 86C - Fibre optic systems and active devices
• Drafting Committee: IEC/SC 86C - IEC_SC_86C
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 09-Mar-2018
• Completion Date: 09-Mar-2018
• Ref Project: SIST EN IEC 61281-1:2018 - Fibre optic communication subsystems - Part 1: Generic specification (IEC 61281-1:2017)

Relations

• Replaces: EN 61281-1:1999 - Fibre optic communication subsystems - Part 1: Generic specification
• Effective Date: 23-Jan-2023

Overview

EN IEC 61281-1:2018 (IEC 61281-1:2017) is the international/CENELEC generic specification for fibre optic communication subsystems (FOCSs). It defines a minimum, specifiable set of parameters common to all fibre‑optic subsystems and describes how those parameters are measured. The document is a technical revision of the 1999 edition (Edition 2.0, 2017‑12) and includes additional definitions to clarify terminology. It is intended to support system design, procurement and testing by providing consistent parameter definitions and references to test procedures and design guides.

Key topics and requirements

The standard covers the following technical topics and requirements for FOCSs:

• Subsystem characterization - common characteristics and general aspects for subsystem specification.
• Digital subsystems - required parameters for digital transmitters, receivers and regenerators (e.g., characteristic tables and measurement parameters).
• Analogue subsystems - parameters for analogue transmitters, receivers and repeaters.
• Fibre optic links and cable plant - cable‑plant and cable‑section characteristics, splice and connector characteristics.
• Optical devices and amplifiers - optical device characteristics and optical amplifier (including semiconductor amplifier) characteristics.
• Terms, symbols and acronyms - standardized definitions to ensure consistent interpretation across documents and projects.
• Measurement and test procedures - each specified parameter is tied to a test method; results are intended to be used in design guides.

Note: EN IEC 61281-1 provides a specifiable minimum; additional parameters and application‑specific requirements are to be defined in relevant standards or project documents.

Applications and who uses it

EN IEC 61281-1 is applicable for anyone involved in specifying, designing, building, testing or procuring fibre‑optic subsystems:

• System architects and network designers - for consistent subsystem parameter selection and link budgeting.
• Equipment manufacturers - to define transmitter/receiver and amplifier specifications for product datasheets.
• Test and measurement laboratories - to apply standardized test procedures and report parameter results.
• Procurement and specification writers - to create minimum requirements for tenders and contracts.
• Integrators and installers - to ensure components meet subsystem‑level expectations and interoperability.

Using this standard helps reduce ambiguity in technical contracts, supports interoperability testing, and streamlines system design by referencing harmonized parameter definitions.

Related standards

EN IEC 61281-1 is part of a broader IEC family addressing fibre‑optic components and measurements. Related documents include series such as IEC 61280, IEC 61290, IEC 60793, IEC 60794 and others referenced or harmonized in the standard. These specify detailed test methods, fibre characteristics and component requirements that complement the generic FOCS specification.

Keywords: Fibre optic communication subsystems, FOCSs, EN IEC 61281-1:2018, IEC 61281-1, fibre optic subsystem specification, optical transmitter, optical receiver, optical amplifier, fibre optic link characteristics, test procedures, design guides.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2018
1DGRPHãþD
SIST EN 61281-1:2001
2SWLþQLNRPXQLNDFLMVNLSRGVLVWHPLGHO6SORãQDVSHFLILNDFLMD,(&

Fibre optic communication subsystems - Part 1: Generic specification (IEC 61281-
1:2017)
Lichtwellenleiter-Kommunikationsuntersysteme - Teil 1: Fachgrundspezifikation (IEC
61281-1:2017)
Sous-systèmes de télécommunications par fibres optiques - Partie 1: Spécification
générique (IEC 61281-1:2017)
Ta slovenski standard je istoveten z: EN IEC 61281-1:2018
ICS:
33.180.01 6LVWHPL]RSWLþQLPLYODNQLQD Fibre optic systems in
VSORãQR general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61281-1

NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2018
ICS 33.180.01 Supersedes EN 61281-1:1999
English Version
Fibre optic communication subsystems - Part 1: Generic
specification
(IEC 61281-1:2017)
Sous-systèmes de télécommunications fibroniques - Partie Lichtwellenleiter-Kommunikationsuntersysteme - Teil 1:
1: Spécification générique Fachgrundspezifikation
(IEC 61281-1:2017) (IEC 61281-1:2017)
This European Standard was approved by CENELEC on 2018-01-19. 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, Serbia, 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: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61281-1:2018 E

European foreword
The text of document 86C/1408/CDV, future edition 2 of IEC 61281-1, prepared by IEC/SC 86C "Fibre
optic systems and active devices, of IEC technical committee 86: Fibre optics" was submitted to the
IEC-CENELEC parallel vote and approved by CENELEC as EN IEC 61281-1:2018.

The following dates are fixed:
(dop) 2018-10-19
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2021-01-19
standards conflicting with the
document have to be withdrawn
This document supersedes EN 61281-1:1999.

This edition constitutes a technical revision. With respect to the previous edition, several new
definitions are added.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 61281-1:2017 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 61280-1-1 NOTE Harmonized as EN 61280-1-1.
IEC 61280-1-3 NOTE Harmonized as EN 61280-1-3.
IEC 61280-1-4 NOTE Harmonized as EN 61280-1-4.
IEC 61280-2-1 NOTE Harmonized as EN 61280-2-1.
IEC 61280-2-2 NOTE Harmonized as EN 61280-2-2.
IEC 61280-2-3 NOTE Harmonized as EN 61280-2-3.
IEC 61280-2-8 NOTE Harmonized as EN 61280-2-8.
IEC 61280-2-9 NOTE Harmonized as EN 61280-2-9.
IEC 61280-2-10 NOTE Harmonized as EN 61280-2-10.
IEC 61280-2-11 NOTE Harmonized as EN 61280-2-11.
IEC 61280-2-12 NOTE Harmonized as EN 61280-2-12.
IEC 61280-4-1 NOTE Harmonized as EN 61280-4-1.
IEC 61280-4-2 NOTE Harmonized as EN 61280-4-2.
IEC 61280-4-4 NOTE Harmonized as EN 61280-4-4.
IEC 62614 NOTE Harmonized as EN 62614.
IEC 61290-1-1 NOTE Harmonized as EN 61290-1-1.
IEC 61290-1-2 NOTE Harmonized as EN 61290-1-2.
IEC 61290-1-3 NOTE Harmonized as EN 61290-1-3.
IEC 61290-3-1 NOTE Harmonized as EN 61290-3-1.
IEC 61290-3-2 NOTE Harmonized as EN 61290-3-2.
IEC 61290-3-3 NOTE Harmonized as EN 61290-3-3.
IEC 61290-4-1 NOTE Harmonized as EN 61290-4-1.
IEC 61290-4-2 NOTE Harmonized as EN 61290-4-2.
IEC 61290-4-3 NOTE Harmonized as EN 61290-4-3.
IEC 61290-5-1 NOTE Harmonized as EN 61290-5-1.
IEC 61290-5-2 NOTE Harmonized as EN 61290-5-2.
IEC 61290-5-3 NOTE Harmonized as EN 61290-5-3.
IEC 61290-6-1 NOTE Harmonized as EN 61290-6-1.
IEC 61290-7-1 NOTE Harmonized as EN 61290-7-1.
IEC 61290-10-1 NOTE Harmonized as EN 61290-10-1.
IEC 61290-10-2 NOTE Harmonized as EN 61290-10-2.
IEC 61290-10-3 NOTE Harmonized as EN 61290-10-3.
IEC 61290-10-4 NOTE Harmonized as EN 61290-10-4.
IEC 61290-10-5 NOTE Harmonized as EN 61290-10-5.
IEC 61290-11-1 NOTE Harmonized as EN 61290-11-1.
IEC 61290-11-2 NOTE Harmonized as EN 61290-11-2.
IEC 60793-1-41 NOTE Harmonized as EN 60793-1-41.
IEC 60793-2 NOTE Harmonized as EN 60793-2.
IEC 60793-2-10 NOTE Harmonized as EN 60793-2-10.
IEC 60793-2-50 NOTE Harmonized as EN 60793-2-50.
IEC 60794-1-1 NOTE Harmonized as EN 60794-1-1.
IEC 60869-1:2012 NOTE Harmonized as EN 60869-1:2013 (not modified).
IEC 60874-1:2011 NOTE Harmonized as EN 60874-1:2012 (not modified).
IEC 60875-1:2015 NOTE Harmonized as EN 60875-1:2015 (not modified).
IEC 60876-1:2014 NOTE Harmonized as EN 60876-1:2014 (not modified).
IEC 61073-1 NOTE Harmonized as EN 61073-1.
IEC 61274-1 NOTE Harmonized as EN 61274-1
IEC 61291 (series) NOTE Harmonized as EN 61291 (series).
IEC 61291-1:2012 NOTE Harmonized as EN 61291-1:2012 (not modified).
IEC 61291-2 NOTE Harmonized as EN 61291-2.
IEC 61291-4 NOTE Harmonized as EN 61291-4.
IEC 61703 NOTE Harmonized as EN 61703.
IEC 61753 (series) NOTE Harmonized in EN 61753 (series).
IEC 62149 (series) NOTE Harmonized in EN 62149 (series).
IEC 62149-1 NOTE Harmonized as EN 62149-1.
IEC 62343-1 (series) NOTE Harmonized as EN 62343-1 (series).
IEC 62343-3 (series) NOTE Harmonized as EN 62343-3 (series).

IEC 61281-1 ®
Edition 2.0 2017-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic communication subsystems –

Part 1: Generic specification
Sous-systèmes de télécommunications fibroniques –

Partie 1: Spécification générique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.01 ISBN 978-2-8322-5188-1

– 2 – IEC 61281-1:2017 © IEC 2017

CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols and acronyms . 22
4.1 Symbols . 22
4.2 Acronyms . 22
5 Subsystem characteristics . 23
5.1 General aspects . 23
5.2 Digital fibre optic subsystems . 26
5.2.1 General description . 26
5.2.2 Digital subsystem characteristics . 26
5.2.3 Digital transmitter characteristics . 26
5.2.4 Digital receiver characteristics . 27
5.2.5 Digital regenerator characteristics . 28
5.3 Analogue fibre optic subsystems . 29
5.3.1 General description . 29
5.3.2 Analogue subsystem characteristics . 29
5.3.3 Analogue transmitter characteristics . 30
5.3.4 Analogue receiver characteristics . 31
5.3.5 Analogue repeater characteristics . 31
5.4 Fibre optic links . 32
5.4.1 General description . 32
5.4.2 Fibre optic cable plant characteristics . 32
5.4.3 Fibre optic cable section characteristics . 33
5.4.4 Optical fibre splice and connector characteristics . 33
5.4.5 Optical device characteristics . 33
5.4.6 Optical amplifier characteristics . 34
Bibliography . 36

Figure 1 – Simplest basic fibre optic system . 24
Figure 2 –More complex BFOS . 24
Figure 3 – Interconnected BFOSs forming a fibre optic subsystem . 25
Figure 4 – BFOS with multiport terminal devices . 25

Table 1 – Digital subsystem characteristics . 26
Table 2 – Digital transmitter characteristics. 27
Table 3 – Digital receiver characteristics . 28
Table 4 – Digital regenerator characteristics . 29
Table 5 – Analogue subsystem characteristics . 30
Table 6 – Analogue transmitter characteristics . 30
Table 7 – Analogue receiver characteristics . 31
Table 8 – Analogue repeater characteristics . 32

IEC 61281-1:2017 © IEC 2017 – 3 –
Table 9 – Fibre optic cable plant characteristics . 33
Table 10 – Optical device characteristics . 33
Table 11 – Optical fibre amplifier characteristics . 34
Table 12 – Semiconductor optical amplifier characteristics . 35

– 4 – IEC 61281-1:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIBRE OPTIC COMMUNICATION SUBSYSTEMS –

Part 1: Generic specification
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 61281-1 has been prepared by subcommittee 86C: Fibre optic
systems and active devices, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 1999. This edition
constitutes a technical revision.
This edition includes the following significant technical change with respect to the previous
edition: addition of new definitions.
The text of this International Standard is based on the following documents:
CDV Report on voting
86C/1408/CDV 86C/1468/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.

IEC 61281-1:2017 © IEC 2017 – 5 –
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 61281-1 series, published under the general title Fibre optic
communication subsystems, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 61281-1:2017 © IEC 2017
FIBRE OPTIC COMMUNICATION SUBSYSTEMS –

Part 1: Generic specification
1 Scope
This part of IEC 61281 is a generic specification for fibre optic communication subsystems
(FOCSs).
The parameters defined herein form a specifiable minimum set of specifications that are
common to all fibre optic subsystems. Additional parameters can be used depending on
the particular application and technology. Those additional parameters will be specified in the
relevant documents, as appropriate.
Each specified parameter is measured using one of the test procedures. The use of these
parameters for system design is given in design guides.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE Within a definition, terms defined elsewhere in Clause 3 are in italics.
3.1
active optical device
optical device, other than an optical dynamic device, exhibiting one or more of the following
functions:
• generation or detection of optical power;
• conversion of an electronic signal to a corresponding optical one or vice versa;
• optical amplification or optical regeneration (2R or 3R) of an optical signal;
• direct conversion of the optical frequency of an optical signal
Note 1 to entry: Active optical devices may comprise passive optical elements.
[SOURCE: IEC TS 62538:2008, 2.1.2, modified – The term "optical active device" has been
replaced by "active optical device".]

IEC 61281-1:2017 © IEC 2017 – 7 –
3.2
amplified spontaneous emission
ASE
optical power associated to spontaneously emitted photon amplified by an active medium in
an optical amplifier
Note 1 to entry: This note applies to the French language only.
[SOURCE: IEC TR 61931:1998, 2.7.87 – The note has been added.]
3.3
analogue input signal bandwidth
bandwidth at the electrical input to the transmitter
3.4
attenuation
reduction of optical power induced by transmission through a medium, given as L (dB) where
L = 10 log (P /P ), and P and P are the power into and out of the transmission medium
10 in out in out
Note 1 to entry: P and P are typically expressed in mW.
in out
3.5
bandwidth
difference (expressed in Hz) between the highest and lowest modulation frequencies at which
the modulus of the power spectrum or of the complex transfer function is one-half of the peak
value of the modulus
3.6
basic fibre optic system
BFOS
serial combination of a transmit terminal device, a fibre optic link, and a receive terminal
device
Note 1 to entry: This note applies to the French language only.
3.7
bit-error ratio
BER
number of errored bits divided by the total number of bits, over some stipulated period of time
Note 1 to entry: This note applies to the French language only.
3.8
branching device
BD
passive device whose purpose is to transfer optical power between two or more ports in a
predetermined manner
Note 1 to entry: The ports may be connected to waveguides, sources, detectors etc.
Note 2 to entry: This note applies to the French language only.
[SOURCE: IEC 60050-731:1991, 731-05-10, modified – The other terms "optical fibre coupler"
and "optical coupler" have been deleted, and the acronym "BD" has been added. Note 2 has
also been added.]
– 8 – IEC 61281-1:2017 © IEC 2017
3.9
carrier-to-noise ratio
CNR
ratio of carrier power to noise power in a channel of defined bandwidth, prior to any non-linear
processing
Note 1 to entry: Carrier-to-noise ratio is expressed in dB.
Note 2 to entry: This note applies to the French language only.
3.10
centre wavelength
mean of the closest spaced half-power wavelengths, one above and one below the peak
wavelength of an optical spectrum
Note 1 to entry: Other spectral wavelengths are centroidal wavelengths, half-power wavelengths, and peak
wavelengths.
3.11
centroidal wavelength
mean or average wavelength of an optical spectrum
Note 1 to entry: Other spectral wavelengths are centre wavelengths, half-power wavelengths, and peak
wavelengths.
3.12
chirping
change of the wavelength or optical frequency of an intensity-modulated transmitter as a
function of the instantaneous intensity of the modulating signal
Note 1 to entry: When chirped signals are transmitted through an optical fibre, the signal waveform is distorted by
chromatic dispersion. This process may cause a degradation in the quality of performance, designated as a
chirping penalty.
3.13
chromatic dispersion
dispersion
rate of change in group delay to wavelength between the end points of the fibre optic cable
plant
Note 1 to entry: Chromatic dispersion is usually expressed in ps/nm.
3.14
encircled flux
fraction of cumulative power to total output power as a function of radial distance from the
centre of the multimode optical fibre’s core
3.15
environmental condition
characteristic of the environment that may affect performance of a device or system
Note 1 to entry: Examples of ambient conditions are pressure, temperature, humidity, radiation, and vibration.
[SOURCE: IEC 60050-151:2001, 151-16-03, modified – The other term "ambient condition"
has been deleted.]
3.16
extinction ratio
ratio of the average power level of logical "1" to the average power level of logical "0", in a
digital transmission system
Note 1 to entry: Extinction ratio is expressed in dB.

IEC 61281-1:2017 © IEC 2017 – 9 –
3.17
fibre optic cable plant
FOCP
serial combination of fibre optic cable sections, connectors, and splices providing the optical
path between two terminal devices, between two optical devices, or between a terminal
device and an optical device
Note 1 to entry: This note applies to the French language only.
3.18
fibre optic cable section
single optical fibre cable which can be unjointed
3.19
fibre optic communication system
assembly of fibre optic subsystems for transmitting information
3.20
fibre optic link
FOL
serial combination of a fibre optic cable plant and optical devices, providing the optical path
between a transmit terminal device and a receive terminal device
Note 1 to entry: This is equivalent to a basic fibre optic subsystem minus the transmitter and receiver.
Note 2 to entry: This note applies to the French language only.
3.21
fibre optic subsystem
assembly of interconnected basic fibre optic subsystems
Note to entry: The assembly is specified at defined interfaces within the fibre optic system.
3.22
fibre optic terminal device
device that converts one or more electrical signals into one or more optical signals, or vice-
versa, and that is connected to at least one optical fibre
Note 1 to entry: A fibre optic terminal device always has one or more integral connectors or pigtails.
Note 2 to entry: Examples include a receive terminal device, a transmit terminal device, a transmitter, and a
receiver.
3.23
full-width at half-maximum
FWHM
positive difference of the closest spaced half-power wavelengths, one above and one below
the peak wavelength of an optical spectrum
Note 1 to entry: Other spectral widths are N-dB-down widths and root-mean-square widths.
Note 2 to entry: The FWHM equals the N-dB-down width where N = 3.
Note 3 to entry: This note applies to the French language only.
3.24
half-power wavelength
wavelength corresponding to a half peak power value of the optical spectrum
Note 1 to entry: Other spectral wavelengths are central wavelengths, centroidal wavelengths, and peak
wavelengths.
– 10 – IEC 61281-1:2017 © IEC 2017
3.25
harmonic distortion
distortion in a system or transducer characterized by the presence at the output of spectral
components which are harmonically related to the spectral components of the input signal
Note 1 to entry: See IEEE Dictionary Online.
3.26
input power range
range of optical power levels such that, for any input signal power of the OFA which lies within
this range, the corresponding output signal power lies in the specified output power range,
where the OFA performance is ensured
[SOURCE: IEC 61291-1:2012, 3.2.1.36, modified – In the definition, the two occurrences of
the term "OA" have been replaced by "OFA".]
3.27
intermodulation distortion
IMD
distortion characterized by the appearance of spectral components with frequencies equal to
the sums and differences of integral multiples of two or more component frequencies of the
input signal
Note 1 to entry: See IEEE Dictionary Online.
Note 2 to entry: This note applies to the French language only.
3.28
intersymbol interference
ISI
overlap of adjacent pulses as caused by the limited bandwidth characteristics of the optical
devices in a fibre optic link
Note 1 to entry: This note applies to the French language only.
3.29
jitter
random or data-induced short-term non-cumulative variations of the phases or of the
significant instants of a digital signal from their ideal positions in time relative to a reference
(clock) signal
Note 1 to entry: In practice, "short-term" embraces all spectral components of 10 Hz and above.
Note 2 to entry: Jitter is expressed in terms of absolute time or as a fraction of a unit interval.
3.30
jitter tolerance
maximum jitter amplitude that a digital receiver can accept for a given penalty or alternatively
without the addition of a given number of errors to the digital signal
Note 1 to entry: The maximum jitter amplitude tolerated is generally dependent on the frequency of the jitter.
3.31
jitter transfer function
ratio of the output jitter to the applied input jitter as a function of modulation frequency
3.32
light source
device or instrument that emits light that is coupled into a fibre under test

IEC 61281-1:2017 © IEC 2017 – 11 –
3.33
line code
sequence of symbols that the binary data is converted into for purposes of transmission
Note 1 to entry: Examples include Manchester, return-to-zero, block codes, digital scrambling.
Note 2 to entry: Line codes are used to recover timing, and in some cases they may be used to detect line errors,
and to convey additional information.
3.34
loss budget
sum of the fibre optic link loss and the power penalty
Note 1 to entry: The loss budget equals the power budget minus the working margin.
Note 2 to entry: The initial/final loss budget is the loss budget at the beginning/end of the life of the link.
Note 3 to entry: The final loss budget equals the sum of the initial loss budget and the reserve margin.
Note 4 to entry: Loss budget is expressed in dB.
3.35
maximum reflectance tolerable at input
maximum fraction of power exiting the input port of the OFA, reflected
into the OFA itself, for which the device still meets its specifications
Note 1 to entry: The measurement is performed with a given input signal optical power.
Note 2 to entry: Maximum reflectance tolerable at input is expressed in dB.
3.36
maximum reflectance tolerable at output
maximum fraction of power exiting the output port of the OFA,
reflected into the OFA itself, for which the device still meets its specifications
Note 1 to entry: The measurement is performed with a given input signal optical power.
Note 2 to entry: Maximum reflectance tolerable at output is expressed in dB.
3.37
maximum total output power
highest optical power level at the output port of the OFA operating
within the absolute maximum ratings
3.38
modal bandwidth
multimode fibre bandwidth due to differential mode attenuation and delay
Note 1 to entry: It does not include chromatic dispersion.
Note 2 to entry: It is measured using a source of narrow spectral width.
3.39
modal noise
noise generated in a fibre optic communication system by the combination of differential
modal attenuation and of fluctuations in the distribution of optical energy among the bound
modes or in the relative phases of the bound modes
3.40
mode partition noise
MPN
noise due to the rapid fluctuation of the power distribution among the longitudinal modes of a
laser
– 12 – IEC 61281-1:2017 © IEC 2017
Note 1 to entry: Due to the chromatic dispersion of the fibre optic cable plant, mode partition noise can produce
signal fluctuations at the receiver.
Note 2 to entry: This note applies to the French language only.
3.41
modulation factor/index
ratio of the peak optical signal of a transmitter modulated by an input analogue signal to the
average optical signal without any input signal
Note 1 to entry: Modulation factor/index is expressed as a percentage.
3.42
multipoint link
two or more fibre optic links that interconnect three or more terminal devices
3.43
N-dB-down width
positive difference of the closest spaced wavelengths, one above and one below the peak
wavelength, at which the spectral power density is N dB down from its peak value
Note 1 to entry: Other spectral widths are full-widths at half-maximum and root-mean-square widths.
3.44
noise figure
NF
decrease of the signal-to-noise ratio (SNR), at the output of the optical detector with unitary
quantum efficiency and zero excess noise, due to the propagation of a shot noise-limited
signal through the OFA
Note 1 to entry: The operating conditions at which the noise figure is specified should be stated.
Note 2 to entry: This property can be described at a discrete wavelength or as a function of wavelength.
Note 3 to entry: The noise degradation due to the OFA is attributable to different contributions, for example:
signal-spontaneous beat noise, spontaneous-spontaneous beat noise, internal reflections noise, signal shot noise,
spontaneous shot noise. Each of these contributions 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 OFAs for analogue applications the noise figure also represents the ratio between
input and the output carrier-to-noise ratios.
Note 6 to entry: The noise figure is expressed in dB.
Note 7 to entry: This note applies to the French language only.
[SOURCE: IEC 61291-1:2012, 3.2.1.38, modified – The information about the unit has been
moved from the definition to the new Note 6. In this entry, the term "OA" has been replaced by
"OFA". Note 7 has been added.]
3.45
non-wavelength-selective branching device
NWSBD
bidirectional passive component possessing three or more ports which operates non-
selectively over a specified range of wavelengths, divides or combines optical power coming
into one or more input port(s) among its one or more output port(s) in a predetermined fashion,
without any amplification, switching, or other active modulation
Note 1 to entry: This note applies to the French language only.

IEC 61281-1:2017 © IEC 2017 – 13 –
[SOURCE: IEC 60875-1:2015, 3.2.1, modified – The other terms "optical coupler" and "optical
splitter" have been deleted, and the abbreviated term "NWSBD" and the note have been
added.]
3.46
operating wavelength range
specified interval of wavelengths around a nominal wavelength within which an optical
component is designed to operate with the specified performance
[SOURCE: IEC TR 61931:1998, 2.6.88, modified – The words "the operating wavelength"
have been replaced by "a nominal wavelength" in the definition.]
3.47
optical amplifier
active optical device that receives an optical input and retransmits it as an optical output of
increased power
Note 1 to entry: An example is an optical fibre amplifier (OFA).
3.48
optical attenuator
passive device, which produces a controlled signal attenuation in an optical fibre transmission
line
Note 1 to entry: An attenuator is intended to be wavelength independent.
[SOURCE: IEC 60869-1:2012, 3.2.1, modified – The information in the note was originally in
the definition.]
3.49
optical connection
splice type, connector type and/or fibre type used as input and output ports of an optical
device
3.50
optical device
generic optical unit, either an optical element, optical component, optical assembly, optical
sub-assembly or optical module
Note 1 to entry: Optical devices can reduce the optical power or change the wavelength of the optical input.
Note 2 to entry: There are active optical devices and passive optical devices.
[SOURCE: IEC TS 62538:2008, 2.2.6, modified – The note has been replaced by two new
notes.]
3.51
optical fibre connector
component normally attached to an optical cable or piece of apparatus for the purpose of
providing frequent optical interconnection/disconnection of optical fibres or cables
Note 1 to entry: This usually consists of two plugs mated together in an adaptor.
[SOURCE: IEC 60874-1:2011, 3.14, modified – The information in the note was originally in
the definition.]
– 14 – IEC 61281-1:2017 © IEC 2017
3.52
optical fibre pigtail
short length of optical fibre permanently attached to a component and intended to facilitate
jointing between that component and another optical fibre or component
[SOURCE: IEC TR 61931:1998, 2.6.14]
3.53
optical fibre splice
permanent or semi-permanent joint to couple optical power between two fibre optic cable
sections
3.54
optical line bandwidth
interface signal bandwidth at the boundary between the fibre optic cable plant and the
terminal device
Note 1 to entry: See also transport bandwidth.
3.55
optical line bit rate
interface rate at the boundary between the fibre optic cable plant and the terminal device
Note 1 to entry: See also transport bit rate.
3.56
optical modulator
optical device that modifies the intensity, frequency, phase, or polarization of an optical
carrier in accordance with an input signal
3.57
optical power
amount of radiant energy per unit time that crosses a given section in the transmission path
Note 1 to entry: Optical power is expressed in watts or, on the logarithmic scale, in dBm (where 0 dBm = 1 mW).
3.58
optical receiver
Rx
terminal device with a single optical input and a corresponding single electrical output
3.59
optical regenerator
regenerative repeater
Rg
active optical device that receives, reshapes, retimes, and retransmits a digital optical signal
3.60
optical repeater
Rp
active optical device that receives, improves, and retransmits an analogue optical signal
3.61
optical return loss
ORL
ratio of the incident power to the reflected power from an end point of the fibre optic cable
plant
Note 1 to entry: For reflected power from an optical device or terminal device, "reflectance" is the preferred term.

IEC 61281-1:2017 © IEC 2017 – 15 –
Note 2 to entry: Optical return loss is expressed in positive dB.
Note 3 to entry: This note applies to the French language only.
3.62
optical signal-to-noise-ratio
OSNR
ratio of the optical signal power to the noise power measured in reference optical bandwidth
Note 1 to entry: Typically, the reference optical bandwidth is 0,1 nm.
Note 2 to entry: OSNR is expressed in dB.
Note 3 to entry: This note applies to the French language only.
3.63
optical splitter
wavelength-independent branching device in which the number of output ports exceeds the
number of input ports
3.64
optical switch
passive component processing one or more ports which selectively transmits, redirects or
blocks optical power in an optical fibre transmission line
[SOURCE: IEC 60876-1:2014, 3.2.1]
3.65
optical time domain reflectometer
OTDR
instrument to characterize and measure the attenuation and optical return loss of a fibre
under test by backscattering
Note 1 to entry: This note applies to the French language only.
3.66
optical transmitter
Tx
device which transmits terminal device with a single electrical input and a corresponding
single optical output
3.67
output power range
the range of optical power levels within which the output signal optical
power of the OFA lies, when the corresponding input signal power lies within the input power
range, where the OFA performance is ensured
3.68
passive optical device
optical device, other than an optical dynamic device or an active optical device, which does
not require external power for its operation, except to control the stability of its own
characteristics
Note 1 to entry: Passive optical devices may comprise optical detectors for monitoring purposes only.
[SOURCE: IEC TS 62538:2008, 2.1.3, modified – The terms "optical passive device" and
"optical active device" have been replaced by "passive optical device" and "active optical
device" respectively.]
– 16 – IEC 61281-1:2017 © IEC 2017
3.69
peak wavelength
wavelength corresponding to the maximum power value of the optical spectrum
Note 1 to entry: Other spectral wavelengths are central wavelengths, centroidal wavelengths, and half-power
wavelengths.
3.70
point-to-point link
fibre optic link that connects a transmitter to a receiver
3.71
polarization-dependent gain
PDG
maximum variation of the OFA gain due to a variation of the state of polarization of the input
signal, at nominal operating conditions
Note 1 to entry: A source of PDG in OFAs is the PDL (polarization-dependent loss) of the passive components
used inside.
Note 2 to entry: This note applies to the French language only.
[SOURCE: IEC 61291-1:2012, 3.2.1.12, modified – In this entry, the term "OA" has been
replaced by "OFA". Note 2 has been added.]
3.72
polarization mode dispersion
PMD
distortion of the transmitted signal attributable to the different velocities of the polarization
components of the same mode and their dependence on wavelength
[SOURCE: IEC TR 61931:1998, 2.4.65, modified – The acronym "PMD" has been added as an
admitted term, and the note has been deleted.]
3.73
power budget
difference between the transmitted optical power and the receiver sensitivity
Note 1 to entry: The power budget equals the sum of the loss budget and the working margin.
Note 2 to entry: The initial/final power budget is the power budget at the beginning/end of the life of the
transmitter and receiver.
Note 3 to entry: Power budget, transmitted optical power and receiver sensitivity are expressed in dBm.
3.74
powering and control
electrical currents and/or voltages, as well as electrical signals,
necessary for OFA operation within the stated maximum ratings
Note 1 to entry: Necessary tolerances on electrical powering and switching on and off procedures are to be
included.
3.75
power penalty
increase of received optical power required to compensate for optical transmission
impairments at a specified quality of performance
Note 1 to entry: Impairments include distortion of the optical signal, dispersion and modal bandwidth of the fibre
optic cable plant, and modal noise. These include degradation due to reflections and to the combined effects of
intersymbol interference, mode-partition noise, and chirping.

IEC 61281-1:2017 © IEC 2017 – 17 –
Note 2 to entry: Power penalty is expressed in dB.
3.76
pump leakage to input
pump optical power which is emitted from the OFA input port
Note 1 to entry: The measurement is performed with a given input signal optical power.
Note 2 to entry: The maximum pump leakage to input occurs for no input signal.
[SOURCE: IEC 61291-1:2012, 3.2.1.61, modified – In the definition, the term "OA" has been
replaced by "OFA".]
3.77
pump leakage to output
pump optical power which is emitted from the OFA output port
Note 1 to entry: The measurement is performed with a given input signal optical power.
Note 2 to entry: The maximum pump leakage to output occurs for no input signal.
[SOURCE: IEC 61291-1:2012, 3.2.1.60, modified – In the definition, the term "OA" has been
replaced by "OFA"]
3.78
Q-factor
ratio of the difference between the mean voltage of the 1 and 0 rails, to the sum of their
standard deviation values
3.79
quality of performance
criteria used to indicate a measure of transmission performance
Note 1 to entry: The most common criteria for digital fibre optic systems are bit-error ratio, Q-factor, signal-to-
noise ratio and optical signal-to-noise ratio.
Note 2 to entry: The most common criteria for analogue fibre optic systems are signal-to-noise ratio and linearity.
3.80
receive terminal device
terminal device that converts one or more optical input signals into one or more electrical
output signals
3.81
receiver bandwidth
bandwidth of the optical-to-electrical transfer function of an optical receiver
3.82
receiver dynamic range
difference of the receiver overload and the receiver sensitivity
Note 1 to entry:
...