EN 3745-202:2018

SLOVENSKI STANDARD
01-januar-2019
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SIST EN 3745-202:2006
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Aerospace series - Fibres and cables, optical, aircraft use - Test methods - Part 202:
Fibre dimensions
Luft- und Raumfahrt - Faseroptische Leitungen für Luftfahrzeuge - Prüfverfahren - Teil
202: Faserabmessungen
Série aérospatiale - Fibres et câbles optiques à usage aéronautique - Méthodes d'essais
- Partie 202: Dimensions de la fibre
Ta slovenski standard je istoveten z: EN 3745-202:2018
ICS:
33.180.10 2SWLþQDYODNQDLQNDEOL Fibres and cables
49.060 /HWDOVNDLQYHVROMVND Aerospace electric
HOHNWULþQDRSUHPDLQVLVWHPL equipment and systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 3745-202
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2018
EUROPÄISCHE NORM
ICS 49.060 Supersedes EN 3745-202:2005
English Version
Aerospace series - Fibres and cables, optical, aircraft use -
Test methods - Part 202: Fibre dimensions
Série aérospatiale - Fibres et câbles optiques à usage Luft- und Raumfahrt - Faseroptische Leitungen für
aéronautique - Méthodes d'essais - Partie 202: Luftfahrzeuge - Prüfverfahren - Teil 202:
Dimensions de la fibre Faserabmessungen
This European Standard was approved by CEN on 12 June 2017.

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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey 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
© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 3745-202:2018 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Preparation of specimens . 4
5 Apparatus. 4
6 Method . 5

European foreword
This document (EN 3745-202:2018) has been prepared by the Aerospace and Defence Industries
Association of Europe - Standardization (ASD-STAN).
After enquiries and votes carried out in accordance with the rules of this Association, this Standard has
received the approval of the National Associations and the Official Services of the member countries of
ASD, prior to its presentation to CEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2019, and conflicting national standards shall be
withdrawn at the latest by April 2019.
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 3745-202:2005.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands,
Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
1 Scope
This European Standard specifies several methods for measuring the diameter of an optical fibre or cable,
the non-circularity and the concentricity of the fibre core/cladding on an optical fibre.
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 2591-100, Aerospace series — Elements of electrical and optical connection — Test methods —
Part 100: General
EN 3745-100, Aerospace series — Fibres and cables, optical, aircraft use — Test methods —
Part 100: General
3 Terms and definitions
No terms and definitions are listed in this document.
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
4 Preparation of specimens
4.1 The specimen shall comprise a length of the optical fibre or cable to be measured. The fibre ends
shall be prepared in accordance with EN 2591-100. The length of specimen shall be (3 ± 0,5) m unless
otherwise specified in the product standard.
lf not yet at standard test conditions, the specimens shall be subjected to standard test conditions and
stabilized at these conditions for 24 h as defined in EN 3745-100.
4.2 The following detail shall be specified if not already included in the product standard:
• type of fibre/cable from which the specimen was taken.
5 Apparatus
For method B, the Light Launch System used shall be as specified in EN 2591-100 with an angular size
> 110 % of the fibre numerical aperture and a spot size > 110 % of fibre core diameter.

6 Method
6.1 Method A: Refracted near field
6.1.1 Object
The refracted near-field measurement is straightforward, accurate and measures directly the refractive
index variation the fibre (core and cladding). The measurement is capable of good resolution and can be
calibrated to give absolute values of refractive indexes. It can be used to obtain profiles of both single-
mode and multimode fibre.
6.1.2 Test apparatus
A schematic diagram of the test apparatus is shown in Figure 1 and Figure 2.
6.1.2.1 Source
A stable laser giving a few milliwatts of power in the TEM00 mode is required.
A HeNe laser, which has a wavelength of 633 nm, may be used, but a correction factor must be applied to
the results for extrapolation at different wavelengths. It shall be noted that measurement at 633 nm may
not give complete information at longer wavelengths; in particular non-uniform fibre doping can affect
the correction.
A quarter-wave plate is introduced to change the beam from linear to circular polarization because the
reflectivity of light at an air-glass interface is strongly angle and polarization dependent.
A pinhole placed at the focus of lens 1 acts as a spatial filter.
6.1.2.2 Launch optics
The launch optics, which are arranged to overfill the NA of the fibre, brings a beam of light to a focus on
the flat end of the fibre. The optical axis of the beam of light should be within 1° of the axis of the fibre.
The resolution of the equipment is determined by the size of the focused spot, which should be as small
as possible in order to maximize the resolution, for example less than 1,5 µm. The equipment enables to
focused spot to be scanned across the fibre diameter.
6.1.2.3 Liquid cell
The liquid in the liquid cell shall have a refractive index slightly higher than that of the fibre cladding.
6.1.2.4 Sensing
The refracted light is collected and brought to the detector in any convenient manner provided that all
the refracted light is collected. By calculation, the required size of disc and its position along the central
axis can be determined.
6.1.3 Sample preparation
A length of fibre of about 1 m is required.
All fibre coating shall be removed from the section of fibre immersed in the liquid cell.
The fibre ends shall be clean, smooth and perpendicular to the fibre axis.
6.1.4 Procedure
Refer to the schematic diagram of the test apparatus (Figure 2).
6.1.4.1 Fibre index profile plot
The launch end of the fibre to be measured is immersed in a liquid cell hose refractive index is slightly
higher than that of the fibre cladding. The fibre is back illuminated by light from a tungsten lamp. Lenses
2 and 3 produce a focused image of the fibre.
The position of lens 3 is adjusted to centre and focus the fibre image, and the laser beam is simultaneously
centred and focused on the fibre.
The disc is centred on the output cone. For multimode fibre, the disc is positioned on the optical axis to
just block the leaky mode. For single-mode fibre, the disc is positioned to give optimum resolution.
Refracted modes passing the disc are collected and focused onto a photodiode. The focused laser spot is
traversed across the fibre end and a plot of fibre refractive index variation is directly obtained.
6.1.4.2 Equipment calibration
The equipment is calibrated with the fibre removed from the liquid cell. During the measurement the
angle of the cone of light varies according to the refractive index seen at the entry point to the fibre (hence
the change of power passing the disc). With the fibre removed and the liquid index and cell thickness
known, this change in angle can be simulated by translating the disc along the optic axis. By moving the
disc to a number of predetermined positions the profile can be scaled is terms of relative index. Absolute
indices, i.e. n and n , can only be found in the cladding index or the liquid index, at the measurement
1 2
wavelength and temperature is known accurately.
6.1.4.3 Results
The following details shall be presented:
• test arrangement and wavelength correction procedure;
• relative humidity and ambient temperature;
• fibre identification. Depending on specification requirement:
 profile through core and cladding centres calibrated for a given wavelength;
 profile along the core major and minor axes calibrated for a given wavelength;
 profiles along the cladding major and minor axes calibrated for a given wavelength.
By the raster scan of the cross-section of the profile, the following quantities may be calculated:
• diameter of core;
• diameter of cladding;
• concentricity error core/cladding;
• non-circularity of core;
• non-circularity of cladding;
• maximum theoretical numerical aperture;
• index difference;
• relative index difference;
• indication of accuracy and reproducibility.
6.2 Method B: Near field light distribution
6.2.1 Object
The following test is for incoming and/or outgoing inspection. Imaging is made on a cross section at the
end of the fibre under test.
The image is magnified by an output optics, for example microscope and various kinds of sensors can be
used (direct examination, photographic camera, digital video analyzer, scanning detector, etc.).
6.2.2 Sample preparation
The sample shall be a short length of the optical fibre to be measured. This length shall be noted. The fibre
ends shall be clean, smooth and perpendicular to the fibre axis.
6.2.3 Apparatus
6.2.3.1 Light source
The core illumination source shall be incoherent, adjustable in intensity and the type shall be noted. A
second light source can be used to illuminate the fibre for cladding measurement purposes. The light
source selected shall be stable for the required period of measurement.
6.2.3.2 Detection systems
Different detection systems can be used depending on the type of measurement to be done (visual
inspection, photography, calculation on the complete pattern).
6.2.3.2.1 Microscope
An inverted metallurgical microscope or a biological microscope with a resolution near the diffraction
limit shall be used (for example it should have a calibrated magnification of up to 600 x and be equipped
with the filar micrometre).
6.2.3.2.2 Microscope with a photographic camera
The microscope described in 6.2.3.2.1 may be equipped with a camera for micro photography. A suitable
scale shall be used to calibrate the dimensions in the photograph.
6.2.3.2.3 Video analyzer
The microscope described in 6.2.3.2.1 may be equipped with a TV camera. The output signal of the camera
can be sent to a TV monitor for visual inspection or to a video analyzer in order to record the complete
output near of the fibre.
6.2.3
...