IEC TR 62901:2016

Guide for the selection of drop cables

IEC TR 62901:2016(E) which is a Technical Report, defines the term "drop cable", describes the application spaces and the performance requirements as a consequence of the different applications. Cable design options which result from specific applications which are not yet described in the existing product specifications will be explained. This technical report also gives some guidance on cable testing with focused attention on cable performance requirements which are not covered by existing standards yet. This technical report is not intended to be used as a product standard. Keywords: drop cable, cable design

General Information

• Status: Published
• Publication Date: 15-Mar-2016
• ICS: 33.180.10 - Fibres and cables
• Technical Committee: SC 86A - Fibres and cables
• Current Stage: PPUB - Publication issued
• Start Date: 16-Mar-2016
• Completion Date: 15-Jun-2016

Overview

IEC TR 62901:2016 - Guidance for the selection of drop cables - is a Technical Report published by the IEC (TC 86 / SC 86A). It defines the term drop cable, describes typical application spaces and the consequent performance requirements, explains cable design options that are not yet covered by existing product specifications, and gives guidance on testing focused on performance aspects not addressed in current standards. This report is informative and not intended as a product standard.

Key Topics and Technical Requirements

• Definitions and scope: Clarifies what constitutes a drop cable in FTTH and related access networks.
• Application spaces: Detailed review of environments where drop cables are used, including:
  • Installation between poles (aerial)
  • Installation in ducts
  • Installation in sewer, water and gas pipes
  • Direct-buried deployment
  • Facade and building wall installations
• Installation options and techniques: Covers self-supporting, lashed and suspended aerial cables; duct techniques (pulling, jetting, blowing, pushing); facade attachment methods.
• Cable design considerations: Explains design options driven by specific applications - for example, strength member arrangements, messenger-integrated designs, removable sheaths for indoor/outdoor drops, and robust low-diameter direct-buried designs.
• Testing and performance guidance: Recommends both standard test procedures and additional tests for performance gaps in existing standards, such as:
  • Abrasion resistance against wind-induced vibration in contact with rough surfaces
  • Tensioning performance tests and other mechanical assessments
• Examples and illustrations: Includes typical cable designs and deployment diagrams for practical selection guidance.

Practical Applications

IEC TR 62901:2016 is directly applicable to:

• FTTH and access network planning and design
• Selection of appropriate drop cables for aerial, duct, facade or buried installations
• Developing supplier specifications where standard product specs do not yet exist
• Defining test regimes for new cable designs and field acceptance testing

Typical use cases:

• Network operators choosing drop cables for last-mile connections
• Cable manufacturers designing drop cable constructions tailored to specific installation environments
• Installation contractors and test laboratories validating mechanical and environmental performance

Who Should Use This Report

• Network planners and engineers (FTTH/ access networks)
• Cable designers and manufacturers
• Installation contractors and field technicians
• Test labs and QA teams
• Standards developers and specification writers within IEC TC 86 / SC 86A

Related Standards

IEC TR 62901 is a Technical Report produced by IEC TC 86 (Fibres and cables). It complements existing product specifications and international standards for fibre optic cables by addressing selection, design variations and additional test requirements where product standards are not yet specified.

Keywords: IEC TR 62901:2016, drop cable, cable design, FTTH, aerial drop, duct installation, direct-buried cable, cable testing.

Standards Content (Sample)

IEC TR 62901 ®
Edition 1.0 2016-03
TECHNICAL
REPORT
colour
inside
Guidance for the selection of drop cables
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IEC TR 62901 ®
Edition 1.0 2016-03
TECHNICAL
REPORT
colour
inside
Guidance for the selection of drop cables

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.10 ISBN 978-2-8322-3235-4

– 2 – IEC TR 62901:2016 © IEC 2016
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references. 7
3 Terms, definitions and abbreviations . 7
3.1 Terms and definitions . 7
3.2 Abbreviations . 8
4 Application spaces . 8
4.1 General . 8
4.2 Installation between poles . 9
4.2.1 General . 9
4.2.2 Self-supporting cables . 9
4.2.3 Lashed and suspended cables . 11
4.3 Installation in ducts . 12
4.4 Installation in sewer, water and gas pipes . 12
4.5 Direct-buried cables . 12
4.6 Installation on facades . 13
5 Installation options . 14
5.1 General . 14
5.2 Installation between poles . 14
5.2.1 General . 14
5.2.2 Self-supporting cables . 14
5.2.3 Lashed cables . 16
5.2.4 Suspended cables . 16
5.3 Cables in ducts . 16
5.3.1 General . 16
5.3.2 Pulling . 16
5.3.3 Jetting . 16
5.3.4 Blowing . 17
5.3.5 Pushing . 17
5.4 Installation in sewer, water and gas pipes . 17
5.4.1 General . 17
5.4.2 Specific deployment options . 17
5.5 Direct-buried cables . 17
5.6 Installation on facades . 18
5.6.1 General . 18
5.6.2 Specific installation options . 18
6 Testing . 18
6.1 General . 18
6.2 Standard test procedures . 18
6.3 Additional test methods . 19
6.3.1 General . 19
6.3.2 Abrasion resistance against wind induced vibration in contact with
rough surface . 19
6.3.3 Tensioning performance test . 19
7 Examples of commonly used drop cable designs . 20
7.1 General . 20

7.2 Designs to be used for the installation between poles . 20
7.2.1 Self-supporting cables . 20
7.2.2 Lashed and suspended cables . 25
7.3 Designs to be used for the installation in ducts . 26
7.4 Designs to be used for the installation in sewer, water and gas pipes . 27
7.5 Designs to be used for direct-buried cables . 27
7.6 Designs to be used for the installation at facades. 28
Annex A (informative) Installation of fibre optic drop cables along facades . 31
A.1 Method 1: Tensioning the cable using clamps between anchors . 31
A.2 Method 2: Attaching the cable with using crimps on the wall . 31
A.3 Method 3: Installing a duct (e.g. fixed by crimps) and pushing the cable
through the duct . 31
A.4 Method 4: Using of alternative routes through the restricted space of
windows and doors . 31
Annex B (informative) Estimation of the pushing length . 32
Annex C (informative) Additional clamp types for optical drop cables . 34
Bibliography . 36

Figure 1 – Configuration of a typical FTTH network. 8
Figure 2 – Dead ends to be used for the installation of long length self-supporting
cables . 9
Figure 3 – P-clamp . 10
Figure 4 – MCC . 10
Figure 5 – Wedge clamp . 11
Figure 6 – Motor-driven lash machine . 11
Figure 7 – Crimp used to fix a cable to the messenger wire . 12
Figure 8 – Tape armored cable . 13
Figure 9 – Puncture-free installation of drop cable . 14
Figure 10 – Attack of drop cables by cicada . 15
Figure 11 – Tensioning performance test set-up . 20
Figure 12 – Self-supporting dielectric aerial cable . 21
Figure 13 – Stranded self-supporting dielectric aerial cable . 21
Figure 14 – Self-supporting aerial cable with non concentrically- arranged strength
members . 22
Figure 15 – Flat self-supporting aerial cable with strength members on both sides . 23
Figure 16 – Rectangular design with one integrated messenger wire and strength
members . 24
Figure 17 – Indoor / outdoor aerial drop cable with removable sheath . 24
Figure 18 – Lashed cable . 25
Figure 19 – Cables suitables for pushing . 26
Figure 20 – Robust direct-buried cable with low diameter . 27
Figure 21 – Facade cables . 29
Figure C.1 – Droplet type clamp . 34
Figure C.2 – Fish type clamp. 34
Figure C.3 – P-clamp . 35
Figure C.4 – Wedge type clamp . 35

– 4 – IEC TR 62901:2016 © IEC 2016

Table 1 – Self-supporting dielectric aerial cables . 21
Table 2 – Stranded self-supporting dielectric aerial cables . 22
Table 3 – Self-supporting cable with non concentrically-arranged strength members . 22
Table 4 – Flat self-supporting aerial cable with strength members on both sides . 23
Table 5 – Rectangular design with one integrated messenger wire and strength
member . 24
Table 6 – Indoor / outdoor aerial drop cable with removable sheath . 25
Table 7 – Lashed cable . 25
Table 8 – Designs to be used for the installation in ducts . 27
Table 9 – Robust direct-buried cable with low diameter . 28
Table 10 – Designs to be used for the installation at facades . 30
Table 11 – Facade cable for fibre counts up to 4 fibres . 30

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GUIDANCE FOR THE SELECTION OF DROP CABLES

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
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The main task of IEC technical committees is to prepare International Standards. However, a
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example "state of the art".
IEC TR 62901, which is a Technical Report, has been prepared by subcommittee 86A: Fibres
and cables, of IEC technical committee 86: Fibre optics.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
86A/1676/DTR 86A/1707/RVC
Full information on the voting for the approval of this technical report 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.

– 6 – IEC TR 62901:2016 © IEC 2016
The committee has decided that the contents of this publication will remain unchanged until
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related to the specific publication. At this date, the publication will be
• reconfirmed,
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A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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GUIDANCE FOR THE SELECTION OF DROP CABLES

1 Scope
This Technical Report defines the term "drop cable", describes the application spaces and the
performance requirements as a consequence of the different applications. Cable design
options which result from specific applications which are not yet described in the existing
product specifications will be explained.
This technical report also gives some guidance on cable testing with focused attention on
cable performance requirements which are not covered by existing standards yet.
This technical report is not intended to be used as a product standard.
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.
None
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
drop cables
cables closing the gap between distribution cables (starting at the Network Access Point or
NAP) and the single user´s home (Multi Dwelling Units or MDUs), or other premises
Note 1 to entry: Drop cables are deployed in aerial, in duct, direct-buried, on facades as well as indoor/outdoor
cables.
Note 2 to entry: Drop cables end either outside the building or inside the building. Therefore, often so-called
indoor/outdoor cables are needed to provide the appropriate fire performance.
Note 3 to entry: The Network access point (NAP) or Access Point is connected to the user´s house by aerial drop
cables or underground drop cables, as shown in Figure 1.

– 8 – IEC TR 62901:2016 © IEC 2016
Access point
Closure Aerial cable
Splitter
User's houses
User's buildings Apartment houses
Underground cable
Access point
Feeder Distribution
IEC
Figure 1 – Configuration of a typical FTTH network
3.2 Abbreviations
ADSS All Dielectric Self-Supporting Cable
ARP Aramid Reenforced Plastic
EFL Excess Fibre Length
FRNC Flame Retardant Non Corrosive
FTTH Fiber To The Home
GRP Glass Fibre Reinforced Plastic
HDPE High Density PE
LDPE Low Density PE
LSZH Low Smoke Zero Halogen
MCC Metal Cable Clamp
NOTE MCC are not made of metal anymore.
MDPE Medium Density PE
NAP Network Access Point
PE Polyethylene
PP Polypropylene
FR Flame Retardant
TB Tight Buffered Fibre or Tight Buffer
4 Application spaces
4.1 General
Clause 4 describes most of the different ways commonly used to connect the end user to the
distribution cable.
4.2 Installation between poles
4.2.1 General
In some countries, the installation of fibre optic aerial drop cable is the most preferred option
because of the relatively low effort compared to other methods like installation in ducts, direct
burying, etc. Especially when the distribution cable has been installed between poles, it is
common practice to also use an aerial installation for the last few meters from the NAP to the
building. The connection to the NAP can either be done by splicing individual fibres to the
NAP, or using field-installable connectors, or using preconnectorized cables when the NAP is
designed to access the branched fibres via already installed connectors. Normally, only lower
fibre counts (e.g. 1 to 8 optical fibres) are required. The distances are short (typically between
20 m and 100 m), thus the span lengths between the poles are also short (15 m to 50 m).
Depending on the preferred installation method, fibre optical cables can be installed as self-
supporting cables, lashed cables or suspended cables.
Even though the span length is short, ice and wind loads have to be taken into account
especially when stringent sag requirements are to be fulfilled.
Cables with a black sheath are typically used for outdoor installations. The black colour is the
result of the addition of "carbon black". A concentration of approximately 2,5 % ensures the
long term stability against UV radiation. When other sheath colours are used (e.g. for a better
appearance) UV stabilizers have to be added. The functionality of those stabilizers has to be
demonstrated by appropriate test procedures.
4.2.2 Self-supporting cables
A self-supporting cable contains all required strain carrying elements; thus it can be directly
fixed to the poles with the appropriate equipment. A widely used method which is also
appropriate for the installation of long length self-supporting cables is the use of metallic
spirals (dead ends, see Figure 2).
IEC
Figure 2 – Dead ends to be used for the installation
of long length self-supporting cables
For shorter length of cable, lower tension cable clamps can be used (see Figure 3, Figure 4
and Figure 5). More examples of commonly used clamp systems are shown in Annex C.
Self-supporting cables can contain metallic strength members which may need to have a good
connection to ground. ADSS cables (see also IEC 60794-3-20) do not need this precaution.

– 10 – IEC TR 62901:2016 © IEC 2016

IEC
Figure 3 – P-clamp
IEC
Left: open
Right: closed
Figure 4 – MCC
IEC
NOTE A wedge clamp is a clamp with one end contacting the cable below its surface and the other end butting
against a crosspiece so that the tightening of a bolt passing through its center causes the clamp to wedge the
cable in position.
Figure 5 – Wedge clamp
4.2.3 Lashed and suspended cables
Lashed cables do not represent a specific class of cables. Almost all outdoor cable designs
can be installed by that "lashing" technique. A prerequisite is a so-called messenger wire
which needs to be installed up-front between the poles. The cable will be attached to the
messenger wire by either winding a "band" or thread made of a metal or a dielectric material
helically around the messenger and fibre optic cable. The winding process can be done with
the help of a machine pulled from the ground or automatically driven by a motor (see Figure
6).
IEC
Figure 6 – Motor-driven lash machine

– 12 – IEC TR 62901:2016 © IEC 2016
Alternatively, the cable can also be fixed to the messenger wire with metallic crimps (see
Figure 7).
IEC
Figure 7 – Crimp used to fix a cable to the messenger wire
The cable can also directly be wound around the messenger wire. No further "lash band" is
required. However, the installation process is more difficult because the cable (and reel),
which has a relatively high mass, has to be moved around the messenger wire. These cables
may be suitable for mid-span access.
4.3 Installation in ducts
Cable installation in ducts is the most reliable installation method. Normally, the duct consists
of a polymeric tube with a diameter of up to 100 mm. The duct can be regarded as an
additional protection of the fibre optic cable. As a consequence, the strength of a cable (e.g.
lateral crush resistance) can be smaller than the one for direct-buried cables.
A duct may be further sub-divided using sub-duct and/or micro-ducts. Cables may be installed
by pulling, blowing or jetting. More detail is given in IEC TR 62691.
Care has to be taken that the ducts are not deformed at any point along their length. Before
installing the cables (e.g. by blowing, jetting or pulling), the diameter of the duct has to be
checked by means of an appropriate test method (see IEC TR 62691, IEC 60794-5-20:2014,
6.9 and Annex E and IEC 60794-1-21:2015, Clause 28).
4.4 Installation in sewer, water and gas pipes
Cable deployment is normally the most expensive part of the network. Especially, digging is
very labour intensive. Therefore, it would be very beneficial to use already existing
infrastructure, for example sewer, gas and water pipes, for the installation of fibre optical
cables. Even though every household is connected via these (service-) pipes, this practice is
not yet largely used. The main invoked reasons are: the access to these pipes is not allowed
by the owner, the more sophisticated technology needed to enter and exit the pipe system is
either too expensive or seems to be too complicated.
Nevertheless, the technology exists and is described in IEC 60794-3-40, IEC 60794-3-50,
IEC 60794-3-60 and IEC TR 62691.
4.5 Direct-buried cables
Direct-buried cables are cables which are deployed in the soil without any additional external
protection. To withstand the mechanical stress as well as possible chemical contamination,
the cables may need additional protection, for example thicker sheath than a duct cable, steel

tape or steel wire armouring, special sheathing materials. Figure 8 shows an example of cable
with additional protection.
Cables used for direct deployment in the soil are described in IEC 60794-3-10, and details of
the installation methods are given in IEC TR 62691.
Ripcord
Dielectric central element
Fiber
Buffer tube
Water swellable tape
Corrugated steel armor
Filing element
Polyethylene (PE) outer jacket
IEC
Figure 8 – Tape armored cable
4.6 Installation on facades
During the last years when FTTH deployment became more popular, more and more fibre
optical cables were installed directly at the house walls to access the individual apartments
from the outside by just drilling a hole through the wall and guiding the cable through it to the
interior of the home. Often, aerial drop cables are used to connect the NAP with the building.
On top of the building, a closure could be installed to connect the incoming cable (many
fibres) to the different cables (e.g. 1 to 8 fibres) needed to access the end user´s apartment.
Annex A describes some of the common practices used for the installation on facades. The
main driver for the installation on facades is the relatively low deployment effort. The cable
can easily be installed vertically just by tensioning it between some anchors fixed to the wall
(see Annex A). No special regulations have to be fulfilled with respect to fire protection.
However, care has to be taken to avoid sheath damage caused by vibration. Wind induced
vibration can cause the cable to swing and successively scratch across the rough outer
surface of the house wall. The resistance of the cable against this kind of load shall be tested
if agreed between customer and supplier (see 60794-1-21:2015, 4.4; the felt shall be replaced
by a rough surface similar to a facade surface). Test parameters (force, mass and number of
cycles) need to be determined. Cables with a black sheath are typically used for outdoor
installations. The black colour is the result of the “carbon black” additive included in a
concentration of approximately 2,5 % to ensure the long term stability against UV radiation.
When other sheath colours are used (e.g. for a better appearance), UV stabilizers shall be
added. The functionality of those stabilizers has to be demonstrated by appropriate test
procedures.
In case that the drop cable is installed into the house, the path of cable is required from
outside to inside the residence. Although the existing duct for wiring or puncturing the facade
is often used, a resident can refuse puncturing the facade. In this case, the cable can be
installed into the restricted space through the door or window as shown in Figure 9.

– 14 – IEC TR 62901:2016 © IEC 2016
a) Drop wiring through door b) Drop wiring through window

Restricted space
Optical cable
door
Circle
radius
Wall
Restricted space
2 ∼ 3 mm
About
Circle radius
2 mm
Bend angle 90 degrees
IEC
Figure 9 – Puncture-free installation of drop cable
5 Installation options
5.1 General
Typical installation conditions for drop cables will be described in Clause 5. It will be shown
that for most application spaces, already existing cable standards (e.g. IEC 60794-2,
IEC 60794-3) can be referenced.
Because of the short lengths of drop cables, the ease of termination becomes a more
prominent criteria for selection. Pre-connectorized solutions or use of field-installable
connectors will speed up the installation process remarkably. However, other methods like
fusion splicing or the use of mechanical splices can be used if appropriate.
5.2 Installation between poles
5.2.1 General
Cables to be installed between poles are described in IEC 60794-3-20. Two types of
installation are currently in use: installation of self-supporting cables which include all the load
carrying elements within the cable, and so-called lashed cables which is a technique based on
standard cables which are attached to a load carrying element (see 5.2.2 and 5.2.3). The
tensile load on the cable depends on the cable weight, length of the span and the required
sag. In addition to that, ice and wind loads shall be taken into account. They depend on the
cross section (diameter, shape) of the design, the amount of ice attached to the cable and the
speed of wind. They contribute remarkably to the tensile load of the cable. Software tools are
available to estimate the resulting loads on the cable.
5.2.2 Self-supporting cables
5.2.2.1 General
Cable designs according to IEC 60794-3-20 include sufficient strength elements to ensure
that the optical fibres do not experience excess fibre strain (typically < 0,2 % long term)
during operation when installed, for example between poles. However, higher strain levels
might be acceptable when drop cables are installed in relatively short cable spans (e.g.

< 100 m). Glaesemann [4] has theoretically shown that under the assumption of the same
failure probability, a shorter fibre length (e.g. 100 m) can be tensioned to a remarkably higher
strain (approximately 0,3 % long term) than a fiber with a length of for example 1 km
(approximately 0,2 % long term). The maximum short term load (2 h to 8 h) can be estimated
to be 0,51 % [4, figure 63]. By using the appropriate tensioning assemblies, the cable can be
directly installed between poles and fixed at each end by the appropriate hardware (spirals,
clamps etc.). In case of low diameter central tube cables, special care has to be taken to
ensure that the installation method does not negatively impact the optical properties, for
example the attenuation. Thus, it should be verified that the tensioning devices do not lead to
any attenuation increase when tensioned to the required load (see 5.3.3). Because of the
small diameter, there is a certain risk that the cable is crushed locally by the tensioning
device (e.g. clamps) or the bend radii are too small which also could result in some
attenuation increase.
Cables in Figure 10 do not suffer from that issue because of the separation of the load
carrying strength member (metallic rope) and the fibre optic cable.
Self-supporting cables with a central tube design must address fibre coupling in the design or
deployment procedures to prevent fibre retraction issues associated with cable elongation
caused by ice and/or wind load.
It is known that a biological attack may induce serious problems on the telecommunication
cable and plants (for example, as described in ITU-T L.46). In particular, there is a risk of
damaging the drop cable when cicadas lay eggs by inserting the ovipositor in the cable, as
illustrated in Figure 10. It is important to select the appropriate material for cable sheath to
avoid this problem taking into account the local fauna.
Direction of insertion
Ovipositor
Cicada egg
Cicada
Drop cable
IEC
Figure 10 – Attack of drop cables by cicada
5.2.2.2 Specific installation options
Very often, installation of central tube design cables by using clamps (see Figure 3) is
performed. The suitability of a cable design can be tested by a modified tensile test (see
6.3.3).
Bend insensitive fibres (e.g. B6 fibres as specified in IEC 60793-2-50) will give some
advantage when clamps are used in cases the cable is tightly bent (see Figure 4). In general,
the use of bend optimized fibers is recommended.
___________
Numbers in square brackets refer to the Bibliography.

– 16 – IEC TR 62901:2016 © IEC 2016
5.2.3 Lashed cables
5.2.3.1 General
Cables suitable for lashing or overlashing are described in IEC 60794-3-10. Also, the lashing
procedure is described in the same standard. Because of the relatively short spans (typically
around 50 m for drop applications), almost no tensile elements are needed in the cable
design. However, it has to be ensured that a minimum of tensile elements is included in the
cable to reduce the cable elongation during unwinding from the cable reel. Forces can easily
go up to 50 N. Low diameter cables (e.g. 2,5 mm to 5 mm) are less susceptible against wind
load because of the relatively low cross section. The lashing wire can be made of steel or
dielectric material, for example aramid yarns.
5.2.3.2 Specific installation option
Metallic lashing wire is recommended in areas where bird attacks are likely.
5.2.4 Suspended cables
Cables according to IEC 60794-3-10 can also be fixed to a messenger wire or another already
installed cable by using crimps which are applied along the length of the span.
5.3 Cables in ducts
5.3.1 General
Installation of fibre optic cables in ducts is the most common practice for a safe deployment.
The ducts are typically made of a polymeric material like HDPE or PP. Typical duct diameters
range from a few millimeters (5 mm, e.g. for microcables) up to 100 mm for typically
3 subducts. The subducts can be filled individually with cables of different diameters. Cables
suitable for the installation in ducts are described in IEC 60794-3-10.
5.3.2 Pulling
5.3.2.1 General
Pulling of cables into ducts is still common practice. With the help of metallic spiral a pulling
rope is attached to one cable end. Then the cable is pulled through the duct with the help of a
winch. The procedure and the equipment needed is described in IEC TR°62691.
5.3.2.2 Specific installation options
During cable pulling, the maximum force acts at the point where the rope is fixed to the cable.
Depending on the total length of the duct the force can easily go up to several hundreds of
Newtons. Therefore the cable has to have sufficient strength elements (e.g. aramid yarns,
glass yarns, metallic or non-metallic rods) to withstand the relatively high pulling tension.
However, for drop applications it is very unlikely that the duct length is longer than 100 m.
Thus the pulling force only should be in the order of 200 N. Additional tensile load can built up
when the duct is deployed around corners with small bend radii. Because of the short
distances and the deployment in safe ducts designs which are light weight and low diameter
are to be preferred.
5.3.3 Jetting
Even though jetting with the help of an incompressible liquid (e.g. water) is a common method
to install cables in ducts, it seems to be not efficient taken the short deployment distances
into account. Jetting requires sophisticated equipment which is not needed for the installation
of short length cables.
5.3.4 Blowing
5.3.4.1 General
As jetting (see 5.3.3), blowing is a method which minimizes the strain on the cable during
installation. The driving force is distributed along the cable length. Thus, this method does not
require cables to withstand high tensile force. A family of cables which is optimized for
blowing is described in IEC 60794-5-10. Alternatively, blowing of fibre units into micro ducts
can be considered (see IEC 60794-5-20).
5.3.4.2 Specific installation options
Cables and fibre units described in IEC 60794-5-10 and IEC 60794-5-20 are optimized for the
use in low diameter ducts (typically less than 16 mm outer diameter, with examples being
14 mm outer diameter and 10 mm inner diameter, or smaller, for blown cables, and 5 mm
outer diameter and 3,5 mm inner diameter, for microduct fibre units). Nowadays blowing
equipment is small in size, thus it can also be used efficiently for the installation of short
length drop cables.
5.3.5 Pushing
5.3.5.1 General
When the distances are short and the duct route is almost straight, cables can easily be
installed by pushing the cables manually or supported by an appropriate caterpillar through
the preinstalled duct. Cables according to IEC 60794-3-10 and IEC 60794-5-10 are suitable to
be pushed into short ducts. However, normally no information about the total length which
could be reached is specified in the product specification.
5.3.5.2 Specific installation options
To be able to push a cable through a duct, it needs to have a certain stiffness to minimize
buckling which increases the friction of the cable to the inner wall of the duct. Up to now, no
data about the stiffness and thus the friction increase due to buckling for different duct
diameters are given in the product specifications. With the help of the coefficient of friction
and the known cable stiffness, the expected pushing force can be estimated for a given duct
length (see Annex B). From a practical point of view, the supplier should be asked to estimate
the pushing length for a maximum pushing force (e.g. 100 N) for a straight duct configuration.
5.4 Installation in sewer, water and gas pipes
5.4.1 General
Deployment of fibre optic cables in routes guided through sewer, water and gas pipes is
based on cable designs described in IEC 60794-3-10 and IEC 60794-3-20.
5.4.2 Specific deployment options
Special requirements have to be met with respect to chemical resistance and compatability
with drinking waterl (see IEC 60794-3-60:2008, Clause 1). Because of the short distances for
drop cables, special effort has to be undertaken to analyse the effort for implementation.
5.5 Direct-buried cables
When the overall situation requires the installation of cables directly into the soil, the cables
should fulfill the requirements given in the standard IEC 60794-3-10. No additional
requirements are to be expected.

– 18 – IEC TR 62901:2016 © IEC 2016
5.6 Installation on facades
5.6.1 General
The requirements to be fulfilled by drop cables to be installed at facades are mainly
determined by the selected installation method.
The following installation methods were observed in the field (Annex A):
Method 1: Tensioning the cable using clamps between anchors
Method 2: Attaching the cable using crimps on the wall
Method 3: Installing a duct (e.g. fixed by crimps) and pushing the cable through the duct
Method 4: Using alternative routes through the restricted space of windows and doors
(see Figure 9)
Because of the low fibre count (1 to 8) which is normally needed for that application, the cable
diameter can be as low as a few millimeters. Cables to be installed according to Method 1
need to have sufficient strength elements to withstand the applied tensions. When the cables
are manually tensioned by the installers, the maximum tension is around 250 N. At the
maximum specified tensile load, the fibre strain should not exceed 0,2 % (higher values have
to be agreed between customer and supplier). To simplify the installation procedure,
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