SIST EN 2591-100:2024

SLOVENSKI STANDARD
01-december-2024
Aeronavtika - Električni in optični spojni elementi - Preskusne metode - 100. del:
Splošno
Aerospace series - Elements of electrical and optical connection - Test methods - Part
100: General
Luft- und Raumfahrt - Elektrische und optische Verbindungselemente - Prüfverfahren -
Teil 100: Allgemeines
Série aérospatiale - Organes de connexion électrique et optique - Méthodes d'essais -
Partie 100 : Généralités
Ta slovenski standard je istoveten z: EN 2591-100:2024
ICS:
49.060 Letalska in vesoljska Aerospace electric
električna oprema in sistemi equipment and systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 2591-100
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2024
EUROPÄISCHE NORM
ICS 49.060; 49.090 Supersedes EN 2591-100:2018
English Version
Aerospace series - Elements of electrical and optical
connection - Test methods - Part 100: General
Série aérospatiale - Organes de connexion électrique et Luft- und Raumfahrt - Elektrische und optische
optique - Méthodes d'essais - Partie 100 : Généralités Verbindungselemente - Prüfverfahren - Teil 100:
Allgemeines
This European Standard was approved by CEN on 3 June 2024.

CEN 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 CEN
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 CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 2591-100:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 5
4 Standard test conditions . 9
5 Test main requirements . 9
5.1 Fibre end preparation . 9
5.1.1 General. 9
5.1.2 Parameters . 9
5.1.3 Methods . 13
5.1.4 Specimen examination and acceptance . 13
5.1.5 Termination cleaning . 14
5.2 Light Launch System (LLS) . 14
5.2.1 General. 14
5.2.2 Generating the correct launch conditions . 15
5.2.3 Launch conditions specification for 62,5 µm/125 µm fibres and cables (NA = 0,275) . 16
5.2.4 Launch conditions specification for 50 µm/125 µm fibres and cables (NA = 0,2) . 19
5.3 Light Detection System (LDS) . 21
5.3.1 General. 21
5.3.2 Method . 22
5.3.3 Special precautions . 22
5.3.4 Documentation . 22
6 List of test methods . 23
7 Test report . 27
Bibliography . 28

European foreword
This document (EN 2591-100:2024) has been prepared by ASD-STAN.
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
This document shall be given the status of a national standard, either by publication of an identical text
or by endorsement, at the latest by April 2025, and conflicting national standards shall be withdrawn at
the latest by April 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 2591-100:2018.
The main changes with respect to the previous edition are as follows:
— EN 2591-100 (P2), 08/2018:
o update of the test requirements for fibre end preparation and light launch conditions for
various sizes and types of fibres;
o addition of new test requirements for light detection systems.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this document: Austria, Belgium, Bulgaria, Croatia, Cyprus,
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
1 Scope
This document specifies the general requirements for the methods of testing elements of electrical,
optical and data transmission system connections used in aerospace applications.
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.
EN 2083, Aerospace series — Copper or copper alloys conductors for electrical cables — Product standard
EN 2084, Aerospace series — Cables, electrical, general purpose, with conductors in copper or copper
alloy — Technical specification
EN 2234, Aerospace series — Cables, electrical, fire-resistant — Technical specification
EN 2346, Aerospace series — Fire resistant electrical cables — Dimensions, conductor resistance and
mass
EN 3745-100, Aerospace series — Fibres and cables, optical, aircraft use — Test methods — Part 100:
General
EN 3745-201, Aerospace series — Fibres and cables, optical, aircraft use — Test methods — Part 201:
Visual examination
EN 4641-100, Aerospace series — Cables, optical 125 μm diameter cladding — Part 100: Tight structure
62,5/125 μm core GI fibre 1,8 mm outside diameter — Product standard
EN 4641-301, Aerospace series — Cables, optical 125 μm diameter cladding — Part 301: Tight structure
50/125 μm GI, fibre nominal 1,8 mm outside diameter — Product standard
EN 60793-1-43, Optical fibres — Part 1-43: Measurement methods and test procedures — Numerical
aperture measurement (IEC 60793-1-43)
EN IEC 60512-1, Connectors for electronic equipment — Tests and measurements — Part 1: General
(IEC 60512-1:2001)
EN IEC 60793-1-45, Optical fibres — Part 1-45: Measurement methods and test procedures — Mode field
diameter (IEC 60793-1-45)
IEC 60050-581, International Electrotechnical Vocabulary — Part 581: Electromechanical components
for electronic equipment
Published as ASD-STAN prEN at the date of publication of this document, available at: https://www.asd-
stan.org/.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-581, EN IEC 60512-1
and EN 3745-100 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
NOTE For the following terms, see EN 3745-100: optical fibre – core – cladding – fibre coating – refractive index
profile – core diameter – cladding diameter – concentricity error core/cladding – non circularity of core – non
circularity of cladding – attenuation – numerical aperture – bandwidth
3.1
element of electrical or optical connection
component the purpose of which is to ensure the connection of circuits
EXAMPLE Connector, module.
Note 1 to entry: In test standards, the term “element of connection” shall be used.
3.2
flight cover
protective cover
accessory designed to ensure, in flight, mechanical protection and sealing of front face of a non-coupled
connector
3.3
connector with built-in protection of contacts
connector with characteristics such that male or female contacts, mounted in a plug or receptacle,
cannot come into contact with the front of the connector to which it is coupled (scoop-proof) and in
which, in the event of accidental coupling of two parts or the connector equipped with male contacts, no
electrical contact can take place
3.4
contact pressure point
point at which a square ended gauge pin of the same basic diameter as the mating contact first engages
the female contact spring member
3.5
initial measurement
examination or measurement of characteristics carried out to determine the magnitude of the
variations produced by the stress or stresses applied
Note 1 to entry: This examination or measurement is carried out at the end of pre-conditioning and under
normal atmospheric conditions for measuring.
3.6
final measurement
examination or measurement of characteristics carried out at the end of the recovery to assess the
condition of the specimen after testing and to determine the magnitude of the variations in
characteristics in relation to the values recorded at initial measuring
3.7
flammability
characteristic of a product which shows resistance when exposed for a given duration to a standard
external flame, combustion remains localized and stops spontaneously after withdrawal of the flame
3.8
fire resistance
characteristic of a product which, when subjected to a standard flame:
— retains its electrical role for six minutes;
— the flame does not propagate to the other side of the support in the first twenty minutes
3.9
values of alternating voltage and current
unless otherwise indicated, alternating voltage and current are indicated in root mean square values
3.10
data bus line
pair of twisted wires, shielded, having a specified impedance, a matched impedance at its two ends and
used for data transport
3.11
branch line
section of twisted wires, shielded, with a specified impedance, which connects equipment to a bus line
3.12
line coupler
element of electrical or optical connection the purpose of which is to shunt the transmission signals
from a bus line to equipment
3.13
line coupler, single
coupler consisting of one line and one branch
3.14
line coupler, double
coupler consisting of one line and two branches
3.15
in-line splice
permanent element of electrical or optical connection for two-wire cables
3.16
line termination
end line component the purpose of which is to match the bus line to its characteristic impedance
3.17
branch termination
end branch termination the purpose of which is to eventually replace equipment
3.18
recovery
treatment of a specimen, after conditioning, so that the properties of the specimen may be stabilized
before measuring
3.19
optical fibre cable
certain number of optical fibres or bundles, coated separately and joined inside a common sheath
3.20
beam splitter
device for dividing an optical beam into two separate beams
3.21
insertion loss
extra optical attenuation caused by the insertion of an extra optical element
into an optical system
3.22
launch angle
angle between the wave propagation vector of the incoming light and the normal vector of an optic fibre
end face
3.23
mode conditioner
device for adapting the light output from a source to produce a defined launch condition for testing an
optical system
3.24
multimode fibre
optical fibre having a large core diameter dimension in relation to the wavelength of the light, and in
which a large number of modes can propagate
3.25
optical port
port which radiates or accepts optical power at the interface
3.26
fibre optic branching device
device possessing three or more optical ports which shares optical power among its ports in a
predetermined fashion
3.27
patch cord
assembly where the cable or fibre is terminated at each end with either a plug or socket connector
3.28
pigtail
short length of fibre between a component and a transmission fibre
Note 1 to entry: It is often permanently secured to the component.
EXAMPLE LED, coupler, connection elements.

3.29
power meter
device for measuring the optical power in a fibre optic system
Note 1 to entry: Power measurements are usually made in Watts or dBm. Relative power measurements are
made in dB.
3.30
single mode fibre
optical fibre in which only one mode can propagate
3.31
passive coupler
passive branching device in which power from one or more incoming optical ports is distributed to one
or more outgoing optical ports
3.32
tee coupler
passive coupler or combiner with three optical ports
3.33
return loss
light energy reflected back from discontinuities in a fibre optic link
3.34
light launch system
LLS
device designed to create defined and repeatable light coupling conditions in a test setup
3.35
light detection system
LDS
device designed to take repeatable measurements of light transmitted by a test setup
3.36
temporary joint
non-permanent optical fibre connecting device for use on equipment
3.37
terminator
non-reflective termination of an optical fibre
3.38
test cord
terminated optical fibre cord used to connect the test equipment to the optical span, or to provide
suitable interfaces to the cabling under test
4 Standard test conditions
4.1 The test methods are written so that the test may be carried out either individually or included in
a test sequence.
4.2 Unless otherwise indicated in the test method, technical specification or product standard, the
test conditions shall be as follows:
— temperature: (23 ± 5) °C;
— atmospheric pressure: 86 kPa to 106 kPa (860 mbar to 1 060 mbar);
— relative humidity: 45 % to 75 %.
The temperature and humidity shall remain constant throughout a series of measurements.
Unless otherwise indicated in the technical specification, the cables used for tests shall be in accordance
with EN 2083 and EN 2084 or EN 2234 and EN 2346.
5 Test main requirements
5.1 Fibre end preparation
5.1.1 General
The aim of this subclause is to give recommendations on the acceptable end condition of fibres, whether
terminated or not. It is not intended to describe a precise method for fibre end preparation; instead, it
gives the information necessary to describe and quantify fibre end quality.
This paragraph is applicable therefore to all tests which require the use of at least one optical interface
of this type. It applies to all types of fibre, silica, plastic or a combination of these and other materials,
generally up to a diameter of 125 µm. Comments are made for some other fibre sizes.
5.1.2 Parameters
5.1.2.1 General
The quality of a fibre end can be described in terms of the end face profile and the surface condition.
These terms are now described in more detail.
5.1.2.2 End face profile
If terminated in a connector ferrule or contact, the fibre/ferrule end-face will be required to have a
particular profile depending on the application.
The most common connector profiles are listed below.
The connector end face profile will determine the connector insertion loss and return loss (back
reflection). Minimizing back reflection is of great importance in certain high-speed and analogue fibre
optic links to prevent instability at the source.
Flat Polish — As the name suggests the fibre interface is essentially flat. Usually produced with a very
hard backing material during polishing. A flat polish of the connector surface will result in a back
reflection of about −16 dB (4 %).
PC Polish — A Physical Contact (PC) polish results in a slightly curved connector surface, forcing the
fibre ends of mating connector pairs into physical contact with each other. This produces much lower
back reflection of −30 dB to −40 dB. The PC polish is the most prevalent connector end face in most
applications.
SPC and UPC Polish — Super PC (SPC) and Ultra PC (UPC) polished connectors are also curved and
physically contact. An extended polishing process enhances the surface quality of the connector,
resulting in back reflections of −40 dB to −55 dB and < −55 dB, respectively. These polish types are used
in high-speed, digital fibre optic transmission systems.
APC Polish — The Angled PC (APC) polish uses an 8-degree angle to the connector end face. Back
reflections of < −60 dB can routinely be accomplished with this type of polish.
For cases where the fibre is not terminated into a connector ferrule, it may be prepared as a nominally
flat interface. This may require cleaving to produce an acceptable end although polishing to a flat profile
is also possible (within a suitable bare fibre adapter). For cases where a ‘flat’ fibre end is to be produced
the flatness of the end-face should be good. In quantitative terms this can be defined in terms of end
face angle (see 5.1.2.2).
It is useful to describe the industry standard parameters for a PC (Physical Contact) profile. These are
shown in Figure 1. This profile is characterized typically by three key parameters namely,
(1) fibre/ferrule radius of curvature, (2) fibre height (undercut or protrusion with respect to the
ferrule) and (3) polish offset (essentially the difference between the fibre centre and any higher polish
apex of the polished end-face. If the system under test has a particular fibre interface profile, then the
light launch system should also have a similar profile.

Key
1 fibre
2 polish apex
Figure 1 — PC parameters for a fibre connection (a) Radius of curvature, (b) Fibre undercut
(planar), (c) Fibre protrusion (planar), (d) Polish offset
The industry standards are typically as follows to ensure a good connection. Radius of curvature values
of between 10 mm to 30 mm are recommended to avoid fibre damage and to ensure low reflectance
and insertion loss. The fibre height specification value is related to specific radius of curvature but the
typical maximum values for undercut and protrusion are ± 50 nm. Fibre apex offset values should be
less than or equal to 50 µm.
5.1.2.3 Surface condition
The requirements of EN 3745-201 shall be applied.
The face of the optical fibre shall be free from large scratches, defects and cracks. For cleaved fibres the
face of the optical fibre shall not exhibit any nicking or lips and internal defects such as cracks. Some
slight chipping may be observed at the cleave point but if it does not extend to the core this should be
acceptable. Typically, a good cleave will have an end face angle of 0,25 degrees (a limit of 0,5 degrees is
sensible). Surface roughness is sometimes used to define condition of a surface. Typical maximum
values for fibre (and ferrule if connectorized) are 50 nm (defined by roughness parameters R and R ).
a q
For connectorized fibres quantitative descriptions of allowable defect and scratch sizes for different
fibre types and sizes can be found in document IEC 61300-3-35. For the purposes of setting
requirements on end face quality the end face of the fibre is divided into measurement regions. These
are reproduced from IEC 61300-3-35 in Table 1. The standard goes on to specify allowable numbers
and sizes of features in each region. Note that, in this document, scratches are defined as permanent
linear features. Defects are all nonlinear features detectable on the fibre. This includes particulates and
other debris, pits, chips, edge chipping, etc.
Table 1 — Measurement regions for single fibre connectors (reproduced from IEC 61300-3-35)
Zone Diameter for single mode Diameter for multimode
A: core 0 µm to 25 µm 0 µm to 65 µm
B: cladding 25 µm to 120 µm 65 µm to 120 µm
C: adhesive 120 µm to 130 µm 120 µm to 130 µm
D: contact 130 µm to 250 µm 130 µm to 250 µm
NOTE 1 All data above assume a 125 µm cladding diameter.
NOTE 2 Multimode core zone diameter is set at 65 µm to accommodate all common core
sizes in a practical manner.
NOTE 3 A defect is defined as existing entirely within the inner-most zone which it touches.

Table 2 — Example of visual requirements (allowable surface features and sizes) for multimode
single fibre connectors (reproduced from IEC 61300-3-35)
Zone name Scratches Defects
A: core No limit ≤ 3 µm 4 ≤ 5 µm
0 > 5 µm None > 5 µm
B: cladding No limit ≤ 5 µm No limit ≤ 2 µm
0 > 5 µm 5 from 2 µm to 5 µm
None > 5 µm
C: adhesive No limit No limit
D: contact No limit None ≥ 10 µm
NOTE 1 For scratches, the requirement refers to width.
NOTE 2 No visible subsurface cracks are allowed in the core or cladding zones.
NOTE 3 All loose particles should be removed. If defects are non-removable, it should be
within the criteria above to be acceptable for use.
NOTE 4 There are no requirements for the area outside the contact zone since defects in
this area have no influence on the performance. Cleaning loose debris beyond this region is
recommended good practice.
NOTE 5 The zone size for multimode fibres has been set 65 µm to accommodate both 50 µm
and 62,5 µm core size fibres. This is done to simplify the grading process.
NOTE 6 Structural features that are part of the functional design of the optical fibre, such as
microstructures, are not considered defects.
Table 3 — Example of visual requirements (allowable surface features and sizes) for low
reflectance (return loss > 45 dB) single-mode fibre optic connectors (reproduced from
IEC 61300-3-35)
Zone name Scratches Defects
A: core None None
B: cladding No limit ≤ 3 µm No limit ≤ 2 µm
None > 3 µm 5 from 2 µm to 5 µm
None > 5 µm
C: adhesive No limit No limit
D: contact No limit None ≥ 10 µm
NOTE 1 For scratches, the requirement refers to width.
NOTE 2 No visible subsurface cracks are allowed in the core or cladding zones.
NOTE 3 All loose particles should be removed. If defects are non-removable, it should be
within the criteria above to be acceptable for use.
NOTE 4 There are no requirements for the area outside the contact zone since defects in
this area have no influence on the performance. Cleaning loose debris beyond this region is
recommended good practice.
NOTE 5 Structural features that are part of the functional design of the optical fibre, such as
microstructures, are not considered defects.
To provide clarity for automated systems, scratches are defined as being less than 4 µm wide, linear in
nature, and with a length that is at least 30 times their width. Defects size is defined as the diameter of
the smallest circle that can encompass the entire defect.
An example of allowable features for a multimode connector is shown in Table 2. As can be seen, no
scratches or defects larger than 5 µm are allowed in the core region. In comparison for a low reflectance
single-mode connector (see Table 3), no scratches are allowed in the much smaller single-mode core.
The reader is referred to this document for inspection criteria for other fibre types such as higher
reflectance single-mode and also angle polished connectors.
5.1.3 Methods
Any method of fibre end preparation is acceptable provided that the parameters specified in 5.1.2 are
within the range specified for the fibre type and end profile required. For cleaved fibres (essentially
flat), cleaving tools are widely available to produce this profile by putting the fibre under tension and
then scribing the fibre, so it breaks to produce a mirror-like finish.
Connectorized fibres are usually prepared by polishing the end face either by manual or
mechanical means.
5.1.4 Specimen examination and acceptance
Any method, optical or otherwise, which enables defects of the size quoted in 5.1.2 (or more generally
in the cited standard reference IEC 61300-3-35) to be assessed, shall be acceptable.
The methods may use systems which are as simple as a microscope with appropriate magnification for
the measurement or as sophisticated as an interferometric system for three-dimensional end face
analysis. For any optical inspection system factors such as field of view, optical resolution and contrast
will be important in being able to detect defects.
For optical inspection (e.g. of surface condition) the simplest techniques may involve direct-view
microscopy with human measurement of observed features. Video microscopy may be used where the
image is displayed on a monitor (after being detected on a sensor or camera). Again measurement may
be made on that image with a calibrated measuring system. Automated microscopy systems are also
available that can reduce human subjectivity by performing digital image capture and software analysis
(with appropriate algorithms). Pass/Fail acce
...