IEC 61977:2015

Fibre optic interconnecting devices and passive components - Fibre optic filters - Generic specification

IEC 61977:2015 applies to the family of fibre optic filters. These components have all of the following general features:
- they are passive for the reason that they contain no optoelectronic or other transducing elements which can process the optical signal launched into the input port;
- they modify the spectral intensity distribution in order to select some wavelengths and inhibit others;
- they are fixed, i.e. the modification of the spectral intensity distribution is fixed and cannot be tuned;
- they have input and output ports or a common port (having both functions of input and output) for the transmission of optical power;
- the ports are optical fibre or optical fibre connectors;
- they differ according to their characteristics.
They can be divided into the following categories:
- short-wave pass (only wavelengths lower than or equal to a specified value are passed);
- long-wave pass (only wavelengths greater than or equal to a specified value are passed);
- band-pass (only an optical window is allowed);
- notch (only an optical window is inhibited).
It is also possible to have a combination of the above categories. This standard establishes uniform requirements for the following: optical, mechanical and environmental properties. This third edition cancels and replaces the second edition published in 2010. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- harmonization of a number of terms and definitions with other generic specifications;
- deletion of the quality assessment level clause. Keywords: fibre optic filters generic specification

Dispositifs d'interconnexion et composants passifs fibroniques - Filtres fibroniques - Spécification générique

L'IEC 61977:2015 s'applique à la famille des filtres fibroniques. Ces composants possèdent l'ensemble des caractéristiques générales suivantes:
- ils sont passifs du fait qu'ils ne contiennent aucun élément optoélectronique ou autres éléments transducteurs susceptibles de traiter le signal optique injecté dans le port d'entrée;
- ils modifient la distribution d'intensité spectrale afin de sélectionner certaines longueurs d'onde et en neutraliser d'autres;
- ils sont fixes, c'est-à-dire que la modification de la distribution de l'intensité spectrale est constante et ne peut donc être accordée;
- ils comportent des ports d'entrée et de sortie ou un port commun (comportant à la fois les fonctions d'entrée et de sortie) pour la transmission de la puissance optique;
- les ports correspondent à la fibre optique ou aux connecteurs à fibres optiques;
- ils comportent des différences selon leurs caractéristiques.
Ils peuvent être répartis selon les catégories suivantes:
- passe-bas (seules les longueurs d'onde inférieures ou égales à une valeur spécifiée sont transmises);
- passe-haut (seules les longueurs d'onde supérieures ou égales à une valeur spécifiée sont transmises);
- passe-bande (seule une fenêtre optique est autorisée);
- coupe-bande (seule une fenêtre optique est neutralisée).
Une combinaison des catégories ci-dessus est également possible. La présente norme établit les exigences uniformes suivantes: les propriétés optiques, mécaniques et d'environnement. Cette troisième édition annule et remplace la deuxième édition parue en 2010. Elle constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- harmonisation d'un certain nombre de termes et définitions avec d'autres spécifications génériques;
- suppression de l'article relatif à l'évaluation de la qualité. Mots clés: filtres fibroniques spécification generique

General Information

• Status: Published
• Publication Date: 27-Aug-2015
• ICS: 33.180.20 - Fibre optic interconnecting devices
• Technical Committee: SC 86B - Fibre optic interconnecting devices and passive components
• Drafting Committee: WG 7 - TC 86/SC 86B/WG 7
• Current Stage: DELPUB - Deleted Publication
• Start Date: 09-Apr-2020
• Completion Date: 30-Nov-2018

Relations

• Revises: IEC 61977:2010 - Fibre optic interconnecting devices and passive components - Fibre optic filters - Generic specification
• Effective Date: 05-Sep-2023
• Revised: IEC 61977:2020 - Fibre optic interconnecting devices and passive components - Fibre optic fixed filters - Generic specification
• Effective Date: 05-Sep-2023

Overview

IEC 61977:2015 is an international standard published by the International Electrotechnical Commission (IEC) that specifies the generic requirements for fibre optic filters used in fibre optic interconnecting devices and passive components. This third edition replaces the 2010 version and provides a harmonized, updated framework defining the optical, mechanical, and environmental properties of fibre optic filters.

These fibre optic filters are passive components designed to selectively modify the spectral intensity distribution of optical signals transmitted via optical fibers. Their fixed filtering functionality allows certain wavelengths to be passed while others are inhibited, enhancing the performance and versatility of fibre optic systems.

Key Topics

• Passive Fibre Optic Filters: Components without optoelectronic or active transducing elements. Their operation is purely optical with no electrical signal processing.
• Spectral Intensity Modification: Filters target specific wavelength ranges to either pass or block them according to predefined criteria.
• Fixed Filtering Characteristics: The filters are non-tunable, providing consistent wavelength selection defined at manufacturing.
• Port Configuration: Filters include input/output ports or a common port that function as both input and output, compatible with optical fibers or fiber connectors.
• Filter Types:
  • Short-wave pass filters: Pass wavelengths less than or equal to a cutoff.
  • Long-wave pass filters: Pass wavelengths greater than or equal to a cutoff.
  • Band-pass filters: Pass a designated optical window of wavelengths.
  • Notch filters: Inhibit a particular optical wavelength range.
• Combined Filter Categories: The standard accommodates filters formed by combining the above fundamental types.
• Standard Harmonization and Definitions: Alignment of terminology with related generic specifications to ensure coherence across optical component standards.
• Optical, Mechanical, and Environmental Requirements: The standard rigorously defines testing, marking, documentation, storage, and safety procedures to ensure performance reliability.
• Technical Annexes: Include detailed examples of etalon filters, fibre Bragg grating (FBG) filters, and thin film filter technologies to provide practical guidance on filter design and applications.

Applications

IEC 61977:2015-compliant fibre optic filters are critical in numerous telecommunications and data transmission applications:

• Wavelength Division Multiplexing (WDM): Precise wavelength selection enables multiplexing and demultiplexing of data channels, facilitating high-capacity fibre optic networks.
• Optical Signal Conditioning: Filters help stabilize laser sources, mitigate signal noise, and improve signal fidelity in fiber optic systems.
• Sensing and Monitoring: Fibre Bragg grating filters are utilized in optical sensors for strain, temperature, and other environmental parameters.
• Optical Amplifiers: Thin film and band-pass filters optimize the gain profile and wavelength selectivity within fibre amplifiers.
• Passive Optical Networks (PONs): Reliable fixed filters ensure consistent optical signal routing without active tuning components, reducing complexity and maintenance.

The standard's classification and strict quality and performance requirements help designers and manufacturers choose the appropriate filter type and ensure compatibility and interoperability in complex optical systems.

Related Standards

IEC 61977:2015 is connected with various other IEC and ISO/IEC standards covering fibre optic components and systems, including:

• IEC 60793 Series: Optical fibres specifications.
• IEC 60794 Series: Optical fibre cables.
• IEC 61754 Series: Fibre optic connector interfaces.
• IEC 61300 Series: Fibre optic interconnecting devices and passive components test procedures.
• Related Generic Specifications: The standard aligns with IEC generic specifications for fibre optic components to ensure consistency in terms, definitions, and quality criteria.
• Optical Performance and Reliability Standards: Referenced to evaluate insertion loss, return loss, environmental durability, and mechanical integrity of fibre optic filters.

By adhering to IEC 61977:2015, manufacturers and system integrators benefit from internationally accepted criteria that improve system reliability, performance, and maintainability while facilitating global trade and standard conformity.

---

Keywords: IEC 61977, fibre optic filters, generic specification, passive fibre optic components, optical filter types, fibre Bragg grating, thin film filters, wavelength selection, optical networking, fibre optic standards, IEC fibre optic.

Standards Content (Sample)

IEC 61977 ®
Edition 3.0 2015-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic interconnecting devices and passive components – Fibre optic filters –
Generic specification
Dispositifs d'interconnexion et composants passifs fibroniques – Filtres
fibroniques – Spécification générique

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IEC 61977 ®
Edition 3.0 2015-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fibre optic interconnecting devices and passive components – Fibre optic filters –

Generic specification
Dispositifs d'interconnexion et composants passifs fibroniques – Filtres

fibroniques – Spécification générique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.180.20 ISBN 978-2-8322-2876-0

– 2 – IEC 61977:2015  IEC 2015

CONTENTS
FOREWORD . 4

1 Scope . 6

2 Normative references . 6

3 Terms and definitions . 7

3.1 Basic terms . 7

3.2 Component terms. 7

3.3 Performance terms . 9

4 Requirements . 12
4.1 Classification . 12
4.1.1 General . 12
4.1.2 Type . 13
4.1.3 Style . 13
4.1.4 Variant . 14
4.1.5 Normative reference extensions. 14
4.2 Documentation . 15
4.2.1 Symbols . 15
4.2.2 Specification system . 15
4.2.3 Drawings . 16
4.2.4 Test and measurements . 17
4.2.5 Test report . 17
4.2.6 Instructions for use . 17
4.3 Standardisation system . 17
4.3.1 Interface standards . 17
4.3.2 Performance standards . 18
4.3.3 Reliability standards . 18
4.3.4 Interlinking . 19
4.4 Design and construction . 20
4.4.1 Materials . 20
4.4.2 Workmanship . 21
4.5 Performance requirements . 21
4.6 Identification and marking . 21
4.6.1 General . 21

4.6.2 Variant identification number . 21
4.6.3 Component marking . 21
4.6.4 Package marking . 21
4.7 Packaging . 22
4.8 Storage conditions . 22
4.9 Safety . 22
Annex A (informative) Example of etalon filter technology . 23
A.1 Operating principle of etalon filter . 23
A.2 Transmission characteristics of etalon filter . 23
Annex B (informative) Example of fibre Bragg grating (FBG) filter technology . 25
B.1 Operating principle of FBG . 25
B.2 Example of usage of an FBG . 25
Annex C (informative) Example of thin film filter technology . 27
C.1 Example of thin film filter technology . 27

C.2 Example of application of thin film filters . 27

Bibliography . 29

Figure 1 – Illustration of passband ripple . 9

Figure 2 – Illustration of a stopband . 10

Figure 3 – Illustration of maximum insertion loss within a passband . 11

Figure 4 – Illustration of minimum insertion loss within a passband . 11

Figure 5 – Illustration of X dB bandwidth . 12

Figure 6 – Optic filter style configurations . 14

Figure 7 – Standards currently under preparation . 20
Figure A.1 – Schematic diagram of an etalon . 23
Figure A.2 – Transmission characteristic of an etalon . 24
Figure B.1 – Technology of a fibre Bragg grating . 25
Figure B.2 – Application of an optical add/drop module . 26
Figure B.3 – Application of an OTDR sensor . 26
Figure B.4 – Application of the wavelength stabilizer for a 980 nm pump LD . 26
Figure C.1 – Structure of a multilayer thin-film . 27
Figure C.2 – Application for a GFF for an optical fibre amplifier . 28
Figure C.3 – Application for a BPF for an optical fibre amplifier . 28

Table 1 – Example of a typical filter classification . 13
Table 2 – The IEC specification structure . 15
Table 3 – Standards interlink matrix . 20
Table 4 – Quality assurance options . 20

– 4 – IEC 61977:2015  IEC 2015

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
FIBRE OPTIC INTERCONNECTING DEVICES

AND PASSIVE COMPONENTS –
FIBRE OPTIC FILTERS – 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 61977 has been prepared by subcommittee 86B: Fibre optic
interconnecting devices and passive components, of IEC technical committee 86: Fibre optics.
This third edition cancels and replaces the second edition published in 2010. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) harmonization of a number of terms and definitions with other generic specifications;
b) deletion of the quality assessment level clause.

The text of this standard is based on the following documents:

CDV Report on voting
86B/3861/CDV 86B/3917/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 committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website 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.
– 6 – IEC 61977:2015  IEC 2015

FIBRE OPTIC INTERCONNECTING DEVICES AND PASSIVE

COMPONENTS – FIBRE OPTIC FILTERS – GENERIC SPECIFICATION

1 Scope
This International Standard applies to the family of fibre optic filters. These components have

all of the following general features:
– they are passive for the reason that they contain no optoelectronic or other transducing
elements which can process the optical signal launched into the input port;
– they modify the spectral intensity distribution in order to select some wavelengths and
inhibit others;
– they are fixed, i.e. the modification of the spectral intensity distribution is fixed and cannot
be tuned;
– they have input and output ports or a common port (having both functions of input and
output) for the transmission of optical power; the ports are optical fibre or optical fibre
connectors;
– they differ according to their characteristics. They can be divided into the following
categories:
• short-wave pass (only wavelengths lower than or equal to a specified value are
passed);
• long-wave pass (only wavelengths greater than or equal to a specified value are
passed);
• band-pass (only an optical window is allowed);
• notch (only an optical window is inhibited).
It is also possible to have a combination of the above categories.
This standard establishes uniform requirements for the following:
– optical, mechanical and environmental properties.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050-731, International Electrotechnical Vocabulary – Chapter 731: Optical fibre
communication (available at http://www.electropedia.org)
IEC 60617 (all parts), Graphical symbols for diagrams (available at http://std.iec.ch/iec60617)
IEC 60695-11-5, Fire hazard testing – Part 11-5: Test flames – Needle-flame test method –
Apparatus, confirmatory test arrangement and guidance
IEC 60825 (all parts), Safety of laser products

IEC 61300 (all parts), Fibre optic interconnecting devices and passive components – Basic

test and measurement procedures

IEC TR 61930, Fibre optic graphical symbology

ISO 129-1, Technical drawings – Indication of dimensions and tolerances – Part 1: General

principles
ISO 286-1, Geometrical product specifications (GPS) – ISO code system for tolerances on

linear sizes – Part 1: Basis of tolerances, deviations and fits

ISO 1101, Geometrical product specifications (GPS) – Geometrical tolerancing – Tolerances
of form, orientation, location and run-out
ISO 8601, Data elements and interchange formats – Information interchange –
Representation of dates and times
3 Terms and definitions
For the purposes of this document the terms and definitions given in IEC 60050-731 and the
following apply.
3.1 Basic terms
3.1.1
port
optical fibre or optical fibre connector attached to a passive component for the entry and/or
exit of the optical power (input and/or output port)
3.2 Component terms
3.2.1
BPF
band-pass filterfibre optic filter designed to allow signals between two specific wavelengths to
pass
Note 1 to entry: This note applies to the French language only.
3.2.2
etalon
device consisting of a transparent plane-parallel plate with two reflecting surfaces, or two

parallel reflecting mirrors
Note 1 to entry: The varying transmission function of an etalon is caused by interference between the multiple
reflections of light between the two reflecting surfaces.
Note 2 to entry: Annex A describes the outline of etalon technology.
3.2.3
FBG
fibre Bragg grating
fibre optic device which has a short periodic variation to the refractive index of the fibre core
along the fibre
Note 1 to entry: An FBG can reflect particular wavelengths of light and transmit other wavelengths.
Note 2 to entry: Annex B describes the outline of FBG technology.
Note 3 to entry: This note applies to the French language only.

– 8 – IEC 61977:2015  IEC 2015

3.2.4
fibre optic filter
passive component used in fibre optic transmission to modify the spectral intensity distribution

of a signal in order to transmit or attenuate some wavelengths and block some others

Note 1 to entry: The wavelength band which transmits or attenuates the signal is called the passband. There may
be more than one passband.
3.2.5
GFF
GEQ
gain flattening filter
gain equalizer
device designed to have the inverse characteristic of the wavelength dependent insertion loss
of an optical device
Note 1 to entry: A GFF (GEQ) is used for the purpose of minimizing the wavelength dependent loss of a fibre
optic device.
Note 2 to entry: A GFF (GEQ) is typically used with (in) an optical amplifier.
Note 3 to entry: This note applies to the French language only.
Note 4 to entry: This note applies to the French language only.
3.2.6
long wavelength pass filter
LWPF
fibre optic filter that passes long wavelength signals but reduces the amplitude of short
wavelength signals
Note 1 to entry: This note applies to the French language only.
3.2.7
notch filter
fibre optic filter that passes all wavelengths except those in a stop band centred on a
particular wavelength
3.2.8
reflecting type fibre optic filter
fibre optic filter in which the input and output ports are coincident
3.2.9
short wavelength pass filter
SWPF
fibre optic filter that passes short wavelength signals but reduces the amplitude of long
wavelength signals
Note 1 to entry: This note applies to the French language only.
3.2.10
thin-film filter
TFF
fibre optic filter which passes particular wavelength band(s) and reflects all other
wavelengths by using the interference effect of thin-film
Note 1 to entry: One of the typical TFF is a dielectric multi-layer film filter. Annex C describes the outline of TFF
technology.
Note 2 to entry: This note applies to the French language only.

3.2.11
transmitting type fibre optic filter

fibre optic filter in which the input and output ports are separated

3.3 Performance terms
3.3.1
operating wavelength
nominal wavelength λ , at which a fibre optic filter operates with the specified performances
h
Note 1 to entry: The term "operating wavelength" includes the nominally transmitting wavelength, and designated
attenuation/isolation wavelength.

3.3.2
operating wavelength range
specified range of wavelengths including all operating wavelengths
Note 1 to entry: It includes all passbands and isolation wavelength ranges.
3.3.3
passband
wavelength range within which a passive optical component is required to operate with optical
attenuation less than or equal to a specified optical attenuation value
Note 1 to entry: There may be one or more passbands for a fibre optic filter.
3.3.4
passband ripple
maximum peak-to-peak variation of the insertion loss (absolute value) over the passband
Note 1 to entry: See Figure 1.
Passband
Passband
Passband ripple
Wavelength
IEC
a) – Passband ripple at band edges b) – Passband ripple in band
Figure 1 – Illustration of passband ripple
Note 2 to entry: For a WWDM (wide wavelength division multiplexing) fibre optic filter which has only one
passband, the term spectral ripple or flatness is used instead of passband ripple.
3.3.5
insertion loss
reduction of optical power in a passband, when transmitted between the ports of a two-port
fibre optic filter
Optical attenuation (dB)
Passband ripple
– 10 – IEC 61977:2015  IEC 2015

Note 1 to entry: The insertion loss is expressed in decibels and defined as:

 P 
out
 
a = −10log
 
P
 in 
where
P is the optical power launched into one of the two ports

in
P is the optical power received from the other port

out
Note 2 to entry: The insertion loss is a function of wavelength.

3.3.6
free spectral range
in the case of a periodic spectral response of a fibre optic filter, difference between two
adjacent operating wavelengths
3.3.7
isolation wavelength
nominal wavelength λ (where λ ≠ λ ), that is nominally suppressed by a fibre optic filter
k h k
3.3.8
isolation wavelength range
stopband
specified range of wavelengths from λ to λ around the isolation wavelength λ , that
kmin kmax k
are nominally suppressed by a fibre optic filter
Note 1 to entry: There may be one or more isolation wavelength ranges (stopbands) for a fibre optic filter.
Note 2 to entry: The term stopband is an antonym of the term passband.
Note 3 to entry: See Figure 2.
Stopband
Wavelength
IEC
Figure 2 – Illustration of a stopband
3.3.9
maximum insertion loss within a passband
maximum value of the insertion loss within a passband
Note 1 to entry: Figure 3 shows passband and maximum insertion loss within a passband.
Insertion loss (dB)
Maximum insertion loss
within passband
Passband
Wavelength
IEC
Figure 3 – Illustration of maximum insertion loss within a passband
3.3.10
maximum slope of passband ripple
maximum value in fibre optic filter of the derivative of the insertion loss (for transmitting type
fibre optic filter) or return loss (for reflecting type fibre optic filter) as a function of wavelength
over the passband
3.3.11
minimum insertion loss within a passband
minimum value of the insertion loss within a passband
Note 1 to entry: Figure 4 shows passband and minimum insertion loss within a passband.
Minimum insertion loss
within passband
Passband
Wavelength
IEC
Figure 4 – Illustration of minimum insertion loss within a passband
3.3.12
return loss
fraction of input power that is returned from a port of a fibre optic filter
Note 1 to entry: The return loss is expressed in decibels and defined as:
Insertion loss (dB)
Insertion loss (dB)
– 12 – IEC 61977:2015  IEC 2015

 P 
refl
 
RL = −10log
 
P
 in 
where
P is the optical power launched into the port;

in
P is the optical power received back from the same port
refl
Note 2 to entry: The return loss is a function of wavelength.

3.3.13
wavelength dependent loss
variation of insertion loss of a fibre optic filter within passband(s).
Note 1 to entry: When there are two or more passbands, the wavelength dependent loss is generally defined as
the maximum value of passband ripples.
3.3.14
X dB bandwidth
minimum band width which the variation of insertion loss is X dB within a passband.
Note 1 to entry: X dB bandwidth shall be determined by considering the temperature dependency of wavelength,
polarization dependency, long term stability of wavelength, etc.
Note 2 to entry: X is typically used as 0,5, 1, 3 or 20.
Note 3 to entry: See Figure 5.
X dB bandwidth
Wavelength
IEC
Figure 5 – Illustration of X dB bandwidth
4 Requirements
4.1 Classification
4.1.1 General
Filters are classified either totally or in part in the following categories:
– type;
– style;
– variant;
– environmental category;
– assessment level;
Optical attenuation (dB)
X dB
X dB
– normative reference extensions.

An example of a typical filter classification is given in Table 1:

Table 1 – Example of a typical filter classification

Type Fixed
Style – Configuration C
– Fibre type: IEC type A1a
– SC connector
Variant Means of mounting
Assessment level A
4.1.2 Type
The optic filter type shall be defined by its intended function and optical performance. There
are several types of filters, for instance:
– long wavelength pass filter (LWPF);
– band-pass filter (BPF);
– short wavelength pass filter (SWPF);
– gain flattening filter (GFF)/ gain equalizer (GEQ);
– notch.
4.1.3 Style
The optic filter style shall be defined on the basis of the following elements:
– the input and output port configuration;
– the connector set type(s), if any.
The seven different input and output configurations can be scheduled as shown in Figure 6:

Filter
Pigtail
IEC
a) Configuration A – Device containing fibre optic pigtails without connector plug

Filter
Connector plug
IEC
b) Configuration B – Device containing integral fibres, with a connector plug on each fibre

Filter
IEC
c) Configuration C – Device containing fibre optic connectors as a part of the device housing

– 14 – IEC 61977:2015  IEC 2015

Filter
Pigtail
IEC
d) Configuration D – Device containing one fibre optic pigtail without connector plug

Filter
Connector plug
IEC
e) Configuration E – Device containing one fibre optic pigtail with a connector plug

Filter
IEC
f) Configuration F – Device containing one fibre optic connector as a part of the device housing
NOTE Configuration G is a device containing some combination of the interfacing features of the preceding
configurations.
Figure 6 – Optic filter style configurations
4.1.4 Variant
The optic filter variant defines the feature that identifies the variety of structurally similar
components. Examples of feature variables which create variants are:
– cable type;
– fibre type;
– housing;
– orientation of ports;
– means of mounting.
4.1.5 Normative reference extensions
Normative reference extensions are used to identify independent standards specifications or
other reference documents integrated into relevant specifications.

Unless a specified exception is noted, additional requirements imposed by an extension are
mandatory. Usage is primarily intended to merge associated components to form hybrid
devices, or integrated functional application requirements that are dependent on technical
expertise other than fibre optics.
Some optical fibre filter configurations require special qualification provisions which shall not be
imposed universally. This accommodates individual component design configurations, specialized
field tooling, or specific application processes. In this case requirements are necessary to
guarantee repeatable performance or adequate safety, and provide additional guidance for
complete product specification. These extensions are mandatory whenever used to prepare,
assemble or install an optical fibre splice either for field application usage or preparation of
qualification test specimens. The relevant specification shall clarify all stipulations. However,
design and style dependent extensions shall not be imposed universally.

Some commercial or residential building applications may require direct reference to specific

safety codes and regulations or incorporate other specific material flammability or toxicity

requirements for specialized locations.

Specialized field tooling may require an extension to implement specific ocular safety, elec-

trical shock or burn hazard avoidance requirements, or require isolation procedures to prevent

potential ignition of combustible gases.

4.2 Documentation
4.2.1 Symbols
Graphical and letter symbols shall, whenever possible, be taken from the IEC 60027 series,
the IEC 60617 series and IEC TR 61930.
4.2.2 Specification system
4.2.2.1 General
This specification is part of the IEC specification system. Subsidiary specifications shall
consist of relevant specifications. This system is shown in Table 2. There are no sectional
specifications for filters.
Table 2 – The IEC specification structure
Specification level Examples of information to be included Applicable to
Basic Assessment system rules Two or more component families
or sub-families
Inspection rules
Optical measurement methods
Sampling plans
Identification rule
Marking standards
Dimensional standards
Terminology
Symbol
Preferred number series
SI units
Generic Specific terminology Component family
Specific symbols
Specific units
Preferred values
Marking
Selection of tests
Qualification approval and/or capability
approval procedures
Blank detail Quality conformance test schedule Groups of types having a
common test schedule
Inspection requirements
Information common to a number of types
Detail Individual values Individual type
Specific information
Completed quality conformance test
schedules
– 16 – IEC 61977:2015  IEC 2015

4.2.2.2 Blank detail specifications

The blank detail specification lists all of the parameters and features applicable to a fibre

optic filter, including the type, operating characteristics, housing configurations, test methods,

and performance requirements. The blank detail specification is applicable to any fibre optic

filter design and quality assessment requirement. The blank detail specification contains the
preferred format for stating the required information in the detail specification.

Blank detail specifications are not, by themselves, a specification level. They are associated
with the generic specification.

Each blank detail specification shall be limited to one environmental category.
Each blank detail specification shall contain
– the minimum mandatory test schedules and performance requirements,
– one or more assessment levels,
– the preferred format for stating the required information in the detail specification,
– in case of hybrid components, including connectors, addition of appropriate entry fields to
show the reference normative document, document title and issue date.
4.2.2.3 Detail specifications
A specific fibre optic filter is described by a corresponding detail specification, which is
prepared by filling in the blanks of the blank detail specification. Within the constraints
imposed by this generic specification, the blank detail specification may be filled in by any
national committee of the IEC, thereby defining a particular fibre optic filter as an IEC
standard.
Detail specifications shall specify the following, as applicable:
– type (see 4.1.2);
– style (see 4.1.3);
– variant(s) (see 4.1.4);
– part identification number for each variant (see 4.6.2);
– drawings, dimensions required (see 4.2.3);
– quality assessment test schedules (see 4.2.5);
– performance requirements (see 4.5).
4.2.3 Drawings
4.2.3.1 General
The drawings and dimensions given in the relevant specifications shall not restrict detail
construction nor be used as manufacturing drawings.
4.2.3.2 Projection system
Either first angle or third angle projection shall be used for the drawings in documents
covered by this specification. All drawings within a document shall use the same projection
system and the drawings shall state which system is used.
4.2.3.3 Dimensional system
All dimensions shall be given in accordance with ISO 129-1, ISO 286-1 and ISO 1101. The
metric system shall be used in all specifications. Dimensions shall not contain more than five

significant digits. When units are converted, a note shall be added in each relevant

specification.
4.2.4 Test and measurements
4.2.4.1 Test and measurement procedures

The test and measurement procedures for optical, mechanical, climatic and environmental
characteristics of filters to be used shall be defined and selected preferentially from the

IEC 61300 series. The size measurement method to be used shall be specified in the relevant

specification for dimensions which are specified within a total tolerance zone of 0,01 mm or

less.
4.2.4.2 Reference components
Reference components for measurement purposes, if required, shall be specified in the
relevant specification.
4.2.4.3 Gauges
Gauges, if required, shall be specified in the relevant specification.
4.2.5 Test report
The test reports shall be prepared for each test conducted as required by a relevant
specification. The data sheets shall be included in the qualification report and in the periodic
inspection report.
Data sheets shall contain the following information as a minimum:
– title and date of test;
– specimen description including the variant identification number (see 4.6.2);
– test equipment used;
– all applicable test details;
– all measurement values and observations;
4.2.6 Instructions for use
Instructions for use, when required, shall be given by the manufacturer.
4.3 Standardisation system
4.3.1 Interface standards
Interface standards provide both manufacturers and users with all the information they require
to make or use products conforming to the physical features of that standard interface.
Interface standards fully define the features essential for the mating and unmating of optical
fibre connectors and other components. They also serve to position the optical datum target,
where defined, relative to other reference data.
Interface standards ensure that connectors and adapters that comply with the standard will fit
together. The standards may also contain tolerance grades for ferrules and alignment devices.
Tolerance grades are used to provide different levels of alignment precision.
The interface dimensions may also be used to design other components that will mate with
the connectors. For example, an active device mount can be designed using the adapter
interface dimensions. The use of these dimensions combined with those of a standard plug,
provides the designer with assurance that the standard plugs will fit into the optical device
mount. They also provide the location of the plug’s optical datum target.

– 18 – IEC 61977:2015  IEC 2015

Standard interface dimensions do not, by themselves, guarantee optical performance. They

guarantee connector mating at a specified fit. Optical performance is currently guaranteed via

the manufacturing specification. Products from the same or different manufacturing

specifications using the same standard interface will always fit together. Guaranteed

performance can be given by any single manufacturer only for products delivered to the same

manufacturing specification. However, it can be reasonably expected that some level of

performance will be obtained by mating products from different manufacturing specifications,
although the level of performance cannot be expected to be any better than that of lower

specified performance.
4.3.2 Performance standards
Performance standards contain a series of tests and measurements (which may or may not be
grouped into a specified schedule depending on the requirements of that standard) with
clearly defined conditions, severities and pass/fail criteria. The tests are intended to be run on
a "one-off" basis to prove the ability of any product to satisfy the "performance standards"
requirement. Each performance standard has a different set of tests, and/or severities (and/or
groupings) representing the requirements of a market sector, user group or system location.
A product that has been shown to meet all the requirements of a performance standard can
be declared as complying with a performance standard but should then be controlled by a
quality assurance/quality conformance programme.
It may be possible to define a key point of the test and measurements standards, when these
are applied (particularly with regard to insertion loss and return loss) in conjunction with the
interface standards of inter-product compatibility. Certainly conformance on each individual
product to this standard will be ensured.
4.3.3 Reliability standards
Reliability standards are intended to ensure that a componen
...