IEC TR 62691:2016

IEC TR 62691 ®
Edition 2.0 2016-06
TECHNICAL
REPORT
colour
inside
Optical fibre cables –
Guidelines to the installation of optical fibre cables

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IEC TR 62691 ®
Edition 2.0 2016-06
TECHNICAL
REPORT
colour
inside
Optical fibre cables –
Guidelines to the installation of optical fibre cables

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.180.10 ISBN 978-2-8322-3497-6

– 2 – IEC TR 62691:2016 © IEC 2016
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references. 8
3 Installation planning . 8
3.1 Installation specification . 8
3.2 Route considerations . 9
3.3 Cable installation – Tension considerations . 9
3.4 Duct installations – Cable tension predictions . 10
3.5 Maximum tension or compression force exerted on cable . 10
3.5.1 General . 10
3.5.2 Total cable tension – pulling applications . 10
3.5.3 Total cable tension – pushing, blowing, or pulling applications . 12
3.6 Installation temperature . 17
3.7 Information and training . 17
4 Cable installation methods . 18
4.1 General considerations . 18
4.2 Safety in confined spaces . 18
4.3 FTTX installation . 18
4.4 Pre-installation procedures . 19
4.5 Installation of optical cables in underground ducts . 19
4.5.1 Application . 19
4.5.2 Installation using trenchless technique . 20
4.5.3 Cable overload protection methods . 20
4.5.4 Cable bending and guiding systems . 20
4.5.5 Winching equipment and ropes . 20
4.5.6 Cable friction and lubrication . 21
4.5.7 Cable handling methods to maximise installed lengths . 22
4.5.8 Jointing length allowance . 23
4.5.9 Blowing techniques for the installation of fiber optic cables into ducts. 23
4.5.10 Optical fibre cable installation by floating technique . 23
4.6 Installation of aerial optical cables . 23
4.6.1 Application . 23
4.6.2 Installation methods . 26
4.6.3 Cable protection methods . 26
4.6.4 Winching and guiding systems. 27
4.6.5 Methods to maximise lengths . 27
4.6.6 Jointing length allowance . 27
4.6.7 In-service considerations . 27
4.6.8 Lashed aerial applications . 28
4.7 Installation of buried cable . 31
4.7.1 Installation methods . 31
4.7.2 Cables in trenches . 31
4.7.3 Installing cables by ploughing . 33
4.7.4 Methods to maximise lengths . 33
4.7.5 Jointing length allowance . 33

4.8 Installation in special situations . 33
4.8.1 Tunnel and building lead-in . 33
4.8.2 Bridges . 33
4.8.3 Underwater . 33
4.8.4 Storm and sanitary sewers . 34
4.8.5 High pressure gas pipes (fiber-in-gas) . 38
4.8.6 Drinking water pipes . 39
4.8.7 Industrial environments . 41
4.9 Installation of indoor cables . 41
4.9.1 General considerations . 41
4.9.2 Cable routing . 41
4.9.3 Confined spaces . 42
4.9.4 Installation of cables in the vertical riser area of buildings . 42
4.10 Blown systems . 42
4.10.1 General considerations . 42
4.10.2 Tube installation . 43
4.10.3 Fibre and cable installation . 43
4.11 Cable location . 44
5 Lightning protection . 44
Bibliography . 45

Figure 1 – Cable tension calculations (Equations (1) to (3)) . 11
Figure 2 – Cable tension calculations (Equations (4) to (9)) . 14
Figure 3 – Cable tension calculations . 17
Figure 4 – FTTX applications . 19
Figure 5 – Cable with fitted sock-type grip . 21
Figure 6 – The "figure-8" system . 22
Figure 7 – Optical fibre cabling in an underground duct . 23
Figure 8 – Aerial cable parameters . 24
Figure 9 – Analysis of forces acting on an aerial cable with ice formation . 25
Figure 10 – Example of calculated forces for an aerial operation cable design . 26
Figure 11 – Aerial cable joint point . 27
Figure 12 – Aerial cable applications . 28
Figure 13 – Drive-off (moving reel) method . 28
Figure 14 – Stationary reel method . 29
Figure 15 – Minimum bend radius for the optical cable at dead ends (single fixing) and
at directional changes (double anchorage) situations . 31
Figure 16 – Conduit robotized installation . 35
Figure 17 – Spring loaded stainless-steel ring – Conduit fastening . 35
Figure 18 – Schematic drawing robotized installation – Drilling . 36
Figure 19 – Schematic drawing – Spanning of optical fibre cables within sewers . 37
Figure 20 – Schematic drawing – Laying on the ground of optical fibre cables within
sewers. 37
Figure 21 – Picture of an the I/O-port . 38
Figure 22 – Schematic drawing of cable installation within gas pipe . 39
Figure 23 – I/O-port for optical fibre installation in water drinking pipes . 40

– 4 – IEC TR 62691:2016 © IEC 2016
Figure 24 – Schematic drawing of OF cable installation within drinking water lines . 40
Figure 25 – Installation of I/O-ports on high pressure PE drinking water pipes . 41
Figure 26 – Cable installation by cascade blowing . 44

Table 1 – Calculation for total tension . 12
Table 2 – Calculation for pulling force in Figure 2 . 14
Table 3 – Calculation for pushing force in Figure 2 . 15
Table 4 – Calculation for blowing force in Figure 2 . 16
Table 5 – Minimum installation depths . 32

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPTICAL FIBRE CABLES –
Guidelines to the installation of optical fibre 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
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
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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
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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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
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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.
IEC TR 62691, which is a Technical Report, has been prepared by subcommittee 86A: Fibres
and cables, of IEC technical committee 86: Fibre optics.
This second edition cancels and replaces the first edition published in 2011. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) more details have been added on cables for lashed applications (transferred from
IEC 60794-3-10);
b) more details have been added on cables for storm and sanitary sewer applications
(transferred from IEC 60794-3-40);
c) more details have been added on cables for high pressure gas pipe applications
(transferred from IEC 60794-3-50);

– 6 – IEC TR 62691:2016 © IEC 2016
d) more details have been added on cables for drinking water pipe applications (transferred
from IEC 60794-3-60);
e) a reference to IEC TR 62263 has been included, concerning optical cables installation on
high voltage power lines;
f) a revision, and an update when applicable, has been done on the referred documents.
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
86A/1721/DTR 86A/1730/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.
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.
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
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
INTRODUCTION
Optical fibre cabling provides a high performance communications pathway whose
characteristics can be degraded by inadequate installation. This Technical Report provides
guidance to assist the user and installer with regard to the general aspects of the installation
of optical fibre cables covered by the IEC 60794 series, and the particular aspects of the
"blowing" technique.
Optical fibre cables are designed so that normal installation practices and equipment can be
used wherever possible. They do, however, generally have a strain limit rather lower than
metallic conductor cables and, in some circumstances, special care and arrangements can be
needed to ensure successful installation.
It is important to pay particular attention to the cable manufacturer's recommendations and
stated physical limitations and not exceed the given cable tensile load rating for a particular
cable. Damage caused by overloading during installation may not be immediately apparent
but can lead to failure later in its service life.
This document does not supersede the additional relevant standards and requirements
applicable to certain hazardous environments, for example electricity supply and railways.

– 8 – IEC TR 62691:2016 © IEC 2016
OPTICAL FIBRE CABLES –
Guidelines to the installation of optical fibre cables

1 Scope
IEC TR 62691, which is a Technical Report, gives recommendations for handling and
installing optical fibre cables on metropolitan communication networks. Installation methods
covered by this document include underground ducts, trenchless technique, blowing in
microducts, aerial installation on poles, lashed aerial in metropolitan networks, direct buried
and use of trenches.
Special installation situations such as tunnelling and lead-in installations, on-bridges,
underwater, use of sanitary sewers, high pressure gas pipes and drinking water pipes are
commented and detailed.
Installation and maintenance of optical fibre cables on overhead power lines including the
following are not covered by this document and are referred to in IEC TR 62263:
• optical ground wire (OPGW) fibre cable;
• optical phase conductor (OPPC) fibre cable;
• optical attached fibre cable (OPAC);
• all dielectric self-supporting (ADSS) optical fibre cable.
IEC TR 62263 includes an extensive coverage on recommendations to ensure the safety of
personnel and equipment when installing or maintaining these types of optical fibre cables on
overhead power lines.
2 Normative references
There are no normative references in this document.
3 Installation planning
3.1 Installation specification
The successful installation of an optical fibre cable can be influenced significantly by careful
planning and assisted by the preparation of an installation specification by the user. The
installation specification should address the cabling infrastructure, cable routes, potential
hazards and installation environment and provide a bill of materials and technical
requirements for cables, connectors and closures.
The installation specification should also detail any civil works, route preparation (including
drawpits, ductwork, traywork and trunking) and surveying that are necessary, together with a
clear indication of responsibilities and contractual interfaces, especially if there are any site or
access limitations.
Post-installation requirements for reinstatement, spares, ancillary services and regulatory
issues should also be addressed.

3.2 Route considerations
Whilst optical fibre cables are lighter and installed in longer lengths than conventional metallic
cables, the same basic route considerations apply.
Route planning and cable handling methods shall carefully take into account the specified
minimum bending radius and maximum tensile loading of the particular optical fibre cable
being installed so that fibre damage, giving rise to latent faults, can be avoided.
Some of the most difficult situations for the installation of optical fibre cables are in
underground ducts, and the condition and geometry of duct routes are of great importance.
Where the infrastructure includes ducts in poor condition, excessive curvature, or ducts
already containing cables or access points with abrupt changes of direction, the maximum pull
distance will be reduced accordingly.
As provision of long cable lengths in underground duct or aerial situations may involve
installation methods that require access to the cable at intermediate points for additional
winching or blowing effort, or "figure-8" techniques, these sites should be chosen with care.
Consideration should also be given to factors of time and disturbance. Installation equipment
may be required to run for long periods of time, and the time of day, noise levels, and
vehicular traffic disruption should be taken into account.
Because the condition of underground ducts intended for optical fibre cable is of particular
importance, care should always be taken to ensure that ducts are in sound condition and as
clean and clear as possible. Consideration can also be given to the provision of a subduct
system, either in single or multiple form, to provide a good environment for installation,
segregation of cables, extra mechanical protection and improved maintenance procedures.
Subducts can be more difficult to rope and cable than normal size ducts, particularly over long
lengths, and the diameter ratio between the cable and subduct should be considered. Note
that in ducts or subducts, bundles of microducts can also be installed, for example by pulling
or blowing.
For overhead route sections, a very important consideration is the need to minimise in-service
cable movement. Movement of the cable produced by thermal changes, cable weight, ice
loading, wind, etc. may have a detrimental effect. A stable pole route, with all poles set as
rigidly as possible, is therefore an important element in reducing possible movement, and
consideration should be given to purpose-designed, optical fibre-compatible, pole top fittings
and attachments.
Although optical fibre cables are generally light in weight, their addition to an existing
suspension member can take the optical fibre beyond its recommended strain limit, and the
added dip and extension should be calculated before installation.
Where it is planned for long lengths of optical fibre cable to be directly buried or ploughed,
those sections involving ploughing can, with advantage, be pre-prepared using specialised
slitting or trenching equipment.
3.3 Cable installation – Tension considerations
The potential for providing very long lengths of optical fibre cable can lead to the need for
confidence that a particular installation operation will be successfully achieved, particularly in
underground ducts, and a good indication can be provided, in some cases, by calculating the
maximum cable tension. This maximum tension can be compared with the stated mechanical
performance of the cable and, where these values are close, consideration can be given to
methods for providing a greater margin of safety such as an alternative cable design,
shortening the route, changing the route or direction of cabling, provision of intermediate
winches, or by taking special precautions at particular locations. Calculation considerations
are indicated in 3.4 and 3.5.
– 10 – IEC TR 62691:2016 © IEC 2016
Cable tensions in ploughing or trenching are generally minimal, much smaller than the rated
tension of the cable. Momentary tensions and jerking due to cable reel inertia when paying off
cables, which result in tensions in the immediate area being installed, should be considered.
In ploughing, frictional tension through the plough chute shall be considered, but is generally
small.
Cable compression and buckling in pushing and blowing should also be considered. Cable
compression less than a critical maximum value generally has no effect on cable
performance. Excessive pushing – either due to pushing or blowing – may cause the cable to
corkscrew in the duct or fold over, which will damage the fibre. Considerations to be taken in
account are:
• cable with smaller diameters will require a lower maximum push force;
• the maximum cable push force will also decrease with larger duct inside diameters.
In either case, a crash test per the cable and installation equipment manufacturers’
procedures should be performed to determine the maximum push force.
See 3.5 and 3.6 for guidance on friction forces consideration during installation.
3.4 Duct installations – Cable tension predictions
It should be noted that the tension calculations for duct installations are of inexact necessity
since the actual geometry and characteristics of the ducts are seldom well known. The
calculations, therefore, should be utilized with regard to experience and empirical data from
similar installations.
Two sets of equations are presented below. The first, presented in 3.5.2, is used to calculate
cable tension in pulling applications. The second, presented in 3.5.3, is used to calculate
cable tension in cable pushing and blowing applications; it may also be used for pulling. Note
that the first set, for pulling only, is much simpler and neglects cable weight in Equation (3).
The second set, for any of the duct installation methods, comprises very complex equations
involving much more data, including amplitude and frequency of innerduct undulations. Much
of this data is generally not known and shall be estimated from cable experiments and
empirical data from similar installations.
3.5 Maximum tension or compression force exerted on cable
3.5.1 General
The following main contributory functions need to be considered when calculating cable
forces-tensions or compression:
• the mass per unit length of cable;
• the diameter of the cable;
• the stiffness of the cable;
• the coefficient of friction between cable sheath and surfaces with which it will come in
contact;
• the inner diameter of the duct;
• deviations (bends and undulations) and inclinations.
3.5.2 Total cable tension – pulling applications
The calculated cable tension or compression force should be evaluated with respect to the
maximum rated cable tension (for pulling) or the maximum pushing force or crash force (for
pushing or blowing) for the cable being installed according to the cable specification or the
manufacturer’s declared rating.

Figure 1 shows an example of routes and common tension formulae (see Equations (1) to
(3)):
Feed end
A
Pulling end
30°
200 m
G
45°
1 in 8 down
1 in 10 up
250 m
F
60 m
Level
90°
20 m
E
100 m
160 m
B
Level
1 in 6 up Level
C D
IEC
Figure 1 – Cable tension calculations (Equations (1) to (3))
Equation (1) is used for straight sections, Equation (2) for inclined sections and Equation (3)
for deviated sections and bends.
T = T + µlwg (1)
i
T = T + lwg (µ cosθ + sinθ) (2)
i
T = T exp (µθ) (3)
i
where
T is the tension at end of section (N);
T is the tension at beginning of section (N);
i
µ is the coefficient of friction (between cable and duct or guide);
l is the length of section (m);
w is the cable specific mass (kg/m);
θ is the inclination (radians, + up, – down) or deviation (radians, horizontal plane);
g is the acceleration due to gravity (9,81 m/s );
The resulting total tensions calculations are shown in Table 1:

– 12 – IEC TR 62691:2016 © IEC 2016
Table 1 – Calculation for total tension
Section Length Tension at Inclination Deviation Equation Tension at
beginning of end of
section T section
i
(cumulative)
T
m N rad rad N
A – 0 – – – 0
A – B 250 0 0,100 – 2 1 460
B – 1 460 – 1,571 3 3 464
B – C 160 3 464 0,165 – 2 4 484
C – 4 484 – – – 4 484
C – D 100 4 484 – – 1 4 980
D – 4 980 – – – 4 980
D – E 20 4 980 0,785 3 7 669
E – 7 669 – – – 7 669
E – F 60 7 669 – – 1 7 967
F – 7 967 0,524 3 10 628
F – G 200 10 628 0,124 – 2 11 390
Where more than one cable per duct is installed, tension can be greatly raised, and it is necessary to take
account of this by applying a factor before the deviation calculation. Factors vary with the number of cables,
sheath/cable materials, cable/duct sizes, cable flexibility, etc. Values can be in the order of 1,5 to 2 for two
cables, 2 to 4 for three cables and 4 to 9 for four cables.

3.5.3 Total cable tension – pushing, blowing, or pulling applications
3.5.3.1 General
Total tension can be calculated on a cumulative basis working through each section from one
end of the route to the other. Calculation is done using the common tension and blowing
formulae listed below:
 
 
WP 8πAfl 8πA 3AB 48B
−1
 
F= sinh + sinh F+ − (4) (horizontal pulling)
i
2  2 4 2
8πA
P WP 2W(P / 4) πP
 
 
 
8πfA
2 l 2
 
WP 48B 2 WP 48B
  P
F= F ± + e  − (+ . – for upwards) (5) (vertical pulling)
i
2 2
 
fA
8π 8πfA
πP πP
 
2Bf
fθ
F= F e + (6) (deviations and bends)
i
6(D − D )R )
d c
b
 
dF 3AB 8πA
= f (W cosα) + + F + W sinα (7) (inclined pulling)
 
4 2
dx
 2(P / 4) P 
 
 
dF 3AB 8πA  D − D 
2 2
d c
= f (W cosα) + + F + F  + W sinα (8) (inclined pushing)
 
 
4 2 2
dx
2(P / 4) P π B
   
 
2 2
 
dF 3AB 8πA  D − D  πD D (p − p )
2 d c 2 c d i
 
= f (W cosα) + + F + F + W sinα−
 
 
4 2 2
dx
 2(P / 4) P   π B x

  2 2 2
8l p −(p − p )
i i
l
(9) (blowing; inclined)
where
F is the force at end of section (N);
F is the force at beginning of section (N);
i
f  is the coefficient of friction, COF (between cable and duct or guide);
m is the cable specific mass (kg/m);
l is the length of duct (m);
W is the cable specific weight = gm (N/m);
g is the acceleration of gravity (9,81 m/s );
B is the cable stiffness (Nm );
D is the cable diameter (m);
c
D is the duct inner diameter (m);
d
A is the amplitude of duct-undulations (m);
P is the period of duct-undulations (m);
R is the bending radius of bend (m);
b
θ is the deviation of bend (radians, horizontal plane);
α is the inclination (radians, + up, – down);
p is the air pressure (absolute) at beginning of section (N/m );
i
p is the air pressure (absolute) at end of section (N/m );
x is the position in the section (m).
Equations (4), (5) and (6) are analytical solutions; Equations (7), (8) and (9) have to be solved
numerically.
Figure 2 shows an example of a cable with diameter of 18 mm, weight of 2 N/m and stiffness
5 Nm , which is installed in a 40/33 mm duct of 2 000 m total length laid in the trajectory
below (the red sections are vertical):

– 14 – IEC TR 62691:2016 © IEC 2016
400 600
1 950 1 990
2 000
1 960 1 980
1 850
1 900
1 600
1 800
10 50
20 40
1 000 1 400
IEC
Figure 2 – Cable tension calculations (Equations (4) to (9))
The coefficient of friction (COF) between cable and duct is 0,1, the (right-angled) bends in the
trajectory are of radius of 1,2 m and the straight sections still make undulations with amplitude
of 5 cm and period of 8 m.
IEC TR 62470 describes techniques to measure the coefficient of friction between cables and
ducts.
3.5.3.2 Pulling force
The pulling force is calculated for the situation where the winch is placed at the beginning of
the trajectory. The cable is placed somewhere in the field. The pulling force is calculated for
one location of the cable, at 1 100 m, with the boundary condition that the cable enters the
duct without any tension as shown in Table 2.
Table 2 – Calculation for pulling force in Figure 2
Position Pulling force
m N
1 100 0
1 000, before bend 20
1 000, after bend 26
600, before bend 127
600, after bend 151
400, before bend 236
400, after bend 279
200, before bend 421
200, after bend 495
150, before bend 547
150, after bend 642
100, before bend 709
100, after bend 833
50, before bend 920
50, after bend 1 079
40, before bend 1 080
40, after bend 1 266
Position Pulling force
m N
20, before bend 1 317
20, after bend 1 544
10, before bend 1 595
10, after bend 1 869
5, before bend 1 887
5, after bend 2 210
0 2 232
In Figure 3, the pulling force is also plotted for other lengths.
3.5.3.3 Pushing force
The pushing force is calculated for the situation where the pushing device is placed at the
beginning of the trajectory. The cable is placed at the same location. The pushing force is
calculated for one location of the cable, at 450 m, with the boundary condition that the
pushing force at the cable end is zero as shown in Table 3.
Table 3 – Calculation for pushing force in Figure 2
Position Pushing force
m N
450 0
400, before bend 10
400, after bend 14
200, before bend 59
200, after bend 72
150, before bend 86
150, after bend 103
100, before bend 131
100, after bend 156
50, before bend 202
50, after bend 239
40, before bend 282
40, after bend 333
20, before bend 415
20, after bend 488
10, before bend 558
10, after bend 655
5, before bend 720
5, after bend 845
0 950
NOTE The available software only gives the end-result of 950 N.

In Figure 3, the pushing force is also plotted for other lengths.

– 16 – IEC TR 62691:2016 © IEC 2016
3.5.3.4 Blowing force
The blowing force is calculated for the situation where the blowing device is placed at the
beginning of the trajectory. The cable is placed at the same location. The calculation is done
for a pressure at the cable inlet of 12 bar relative to atmosphere (13 bar absolute) and the
duct open at 2 000 m. Note that the calculation starts with the cable-end at the "critical point",
the position where the pushing force reaches a maximum, at the bend at 1 000 m (beyond this
position, the airflow propelling forces become larger than the friction forces). The calculation
does not take into account the effect of the filling of the duct with cable on the airflow (which
shifts the critical point to a position further in the trajectory), which makes the calculation
worst case. In this example, the full 2 000 m can be bridged by blowing. This is illustrated in
Table 4.
Table 4 – Calculation for blowing force in Figure 2
Position Pushing force
m N
1 000, before bend 0
1 000, after bend 2,5
600, before bend 5
600, after bend 8
400, before bend 13
400, after bend 18
200, before bend 26
200, after bend 34
150, before bend 38
150, after bend 47
100, before bend 52
100, after bend 64
50, before bend 70
50, after bend 85
40, before bend 108
40, after bend 130
20, before bend 136
20, after bend 161
10, before bend 142
10, after bend 169
5, before bend 171
5, after bend 204
0 208
In Figure 3, the pushing force is also plotted for other lengths. Note that calculation is still
done with the duct open at the corresponding lengths. Also note that the plotted pushing force
in Figure 3 is a little higher than the force in the Table 3. The forces plotted in Figure 3 are
obtained with software that also takes into account that the cable end needs a little higher
pushing force when exactly in the bend than when passed. This is why a bend is picked as
the critical point, while the airflow propelling forces are already a little higher than the friction
forces.
2 000
1 500
1 000
Series 1
Series 2
Series 3
0 500 1 000 1 500 2 000
–500
–1 000
Position x (m)
IEC
Series 1 blowing
Series 2 pushing
Series 3 pulling
Figure 3 – Cable tension calculations
3.6 Installation temperature
Installation temperature may affect installation procedures and it is good practice to install
optical fibre cables, particularly in long lengths only when the temperature is within the limits
set by the particular cable manufacturer.
The mechanical properties of optical cables are also dependent on the temperature and the
materials used in their construction. Typically, cables containing PVC in their construction
should not be installed when their temperature is below 0 °C, whilst cables incorporating
polyethylene can be installed when their temperature is down to –15 °C. For most cables, the
upper installation temperature limit is +50 °C. Unless special measures are taken, cables
should not have been exposed to temperatures outside the specified installation temperature
range for a period of 12 h prior to installation.
NOTE Polyethylene which is used as a common sheath material starts softening around 50 °C. Thus, the
coefficient of friction increases remarkably. This will impact installation performance (pulling, pushing, blowing)
negatively. In general, PVC sheathed cables have a poorer installation capability than PE cables, especially at
elevated temperature.
3.7 Information and training
Methods and practices used in the handling of optical fibre cables during installation can,
without producing any immediately obvious physical damage or transmission loss, affect their
long-term transmission characteristics.
Technicians involved in installation procedures should be made fully aware of the correct
methods to employ, the possible consequences of employing incorrect methods, and have
sufficient information and training to enable cables to be installed without damage to fibres.
Cable tension F (N)
– 18 – IEC TR 62691:2016 © IEC 2016
In particular, installation crews should be made aware of minimum bending criteria, and how
easy it is to contravene these when installing by hand.
4 Cable installation methods
4.1 General considerations
Optical fibre cable can be installed using the same or similar general methods employed for
metallic cables but with more attention required to certain aspects such as long lengths, cable
bending and cable strain. It may be necessary to employ particular methods and equipment in
some circumstances. Optical fibre shall be protected from excessive strains, produced axially
or in bending, during installation; various methods are available to do this. The aim of all
optical fibre, cable-placing methods and systems should be to install the cable with the fibre in
an as near as possible strain-free condition, ready for splicing.
Other general precautions:
• delivery of cable to site should be monitored to ensure that no mechanical damage occurs
during off-loading from vehicles;
• storage conditions should be suitable, taking into account mechanical and environmental
considerations;
• documentation should be checked to ensure that cable delivered is in accordance with the
procurement specification;
• suitable protective caps should be fitted to the exposed ends of the optical cable. End
caps should be handled carefully to avoid damage during installation, and any damaged
caps should be repaired or replaced.
4.2 Safety in confined spaces
During the installation of optical fibre cables, it may be necessary to work in confined spaces
such as manholes, underground passageways, tunnels and cable ways and areas where air
circulation is poor or where entry and exit is difficult.
Where the possibility of workin
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