CLC/TR 50510:2012

SLOVENSKI STANDARD
01-februar-2013
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SIST-TP CLC/TR 50510:2008
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Fibre optic access to end-user - A guideline to building of FTTX fibre optic network
Lichtwellenleiter Anschluß beim Endkunden - Leitfaden für die Erstellung von FTTx-
Lichtwellenleiternetzen
Accès à l’utilisateur par fibres optiques - Lignes directrices relatives à la construction
d’un réseau en fibres optiques de type FttX
Ta slovenski standard je istoveten z: CLC/TR 50510:2012
ICS:
33.180.99 'UXJDRSUHPD]DRSWLþQD Other fibre optic equipment
YODNQD
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CLC/TR 50510
RAPPORT TECHNIQUE
November 2012
TECHNISCHER BERICHT
ICS 33.180.99 Supersedes CLC/TR 50510:2007

English version
Fibre optic access to end-user -
A guideline to building of FTTX fibre optic network

Accès à l’utilisateur par fibres optiques -  Lichtwellenleiterzugang zum Endkunden -
Lignes directrices relatives à la Leitfaden für die Erstellung von FTTx-
construction d’un réseau en fibres Lichtwellenleiternetzen
optiques de type FttX
This Technical Report was approved by CENELEC on 2012-10-15.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,
Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2012 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. CLC/TR 50510:2012 E
Contents
Executive summary . 6
1 Introduction to Broadband . 8
2 Network Structure and Nodes . 9
2.1 General . 9
2.2 Network Layers . 9
2.2.1 Overview . 9
2.2.2 Physical routing . 10
2.2.3 Passive transmission media . 10
2.2.4 Transmission-, IP- and application layer. 10
2.2.5 Ownership, operating and maintenance . 10
2.3 Network topology – Terminology . 10
2.3.1 Overview on Infrastructure . 10
2.3.2 National network . 11
2.3.3 Regional network . 11
2.3.4 Municipality connecting network . 12
2.3.5 Metropolitan or urban network . 12
2.3.6 Access network . 13
2.4 Nodes – Topology and Terminology . 13
2.4.1 Overview . 13
2.4.2 National node . 14
2.4.3 Regional node . 14
2.4.4 Main node . 14
2.4.5 Access node . 14
2.5 Examples of FTTx topologies . 15
2.6 FTTx in the access network . 18
2.6.1 Overview . 18
2.6.2 FTTx in access networks . 18
3 FTTx passive network products and system implementations . 19
3.1 General . 19
3.2 Optical fibres . 19
3.2.1 Triple play and general about new fibres . 19
3.2.2 Choice of optical fibre type . 19
3.2.3 Number of optical fibres provided to each end-user . 21
3.3 Cables and ducts. 21
3.3.1 Cables . 21
3.3.2 Hybrid cables . 22
3.3.3 Outdoor . 23
3.3.4 Indoor . 23
3.3.5 Blown fibre units . 23
3.3.6 Microduct optical fibre cables for blowing . 24
3.3.7 Cables for blowing . 24
3.3.8 Dimensions for microducts and multi duct bundles . 24
3.4 Connectivity products . 26
3.4.1 Connectors in the FTTx-network . 26
3.4.2 Optical fibre splicing . 28
3.4.3 Pre-connectorised fibre . 29

– 3 – CLC/TR 50510:2012
3.5 Optical splitters . 29
3.5.1 General . 29
3.5.2 Fused biconic taper technology . 29
3.5.3 Planar splitter technology . 29
3.6 Fibre organisers and closures . 30
3.6.1 Closures . 30
3.6.2 Optical Distribution Frame (ODF) . 31
3.6.3 Connectivity Products for Indoor FTTx Networks . 32
3.7 Access Node . 32
3.7.1 Design of the POP housing (a room for an access node) . 32
3.7.2 Power feeding an access node . 35
3.7.3 Earthing in an access node . 35
3.8 System design . 36
3.8.1 Link dimensioning . 36
3.8.2 Calculation of an optical power budget . 36
3.9 Cabling implementation . 37
3.9.1 Optical fibre cabling . 37
3.9.2 Pulling, burying and blowing . 38
3.9.3 Right of Way (RoW) solution . 39
3.9.4 Access and jointing chambers . 43
4 Network design . 44
4.1 Overview . 44
4.2 Areas with block(s) of Multi-Dwelling Units (MDUs) . 44
4.3 Areas with detached houses . 45
4.4 Rural areas . 47
4.5 General considerations when designing a network . 48
5 Planning. 49
5.1 General . 49
5.1.1 Outline planning . 49
5.1.2 Development of outline plans . 49
5.1.3 Detailed planning . 51
5.2 Installation – General advice . 51
5.2.1 Drilling . 51
5.2.2 Lift shaft . 51
5.2.3 Messages to residents . 51
5.2.4 Insurance and compensation for damage . 51
5.2.5 Certificate . 51
5.3 Installation in node areas . 51
5.3.1 Access node . 51
5.3.2 Area for splice cabinet – Optical fibre concentration point . 52
5.3.3 In a flat, a house or similar area (user node – subscriber node) . 53
6 Installation . 54
6.1 Underground work . 54
6.1.1 Material for ducts, cables and microduct optical fibre cables . 54
6.1.2 Ploughing for installation of ducts (cables) . 55
6.1.3 Digging and milling for installations of ducts (cable) . 56
6.1.4 Warning tape or ribbon . 56
6.1.5 Installation in ducts . 57
6.1.6 Sub-ducts . 57

6.1.7 Various techniques to install cables into ducts . 58
6.1.8 Installation of cable into ducts with compressed air or floating with water . 58
6.1.9 Installation with pulling rope . 59
6.1.10 Preventive protection of ducts and cables in manholes . 61
6.2 Aerial installation . 61
6.2.1 General . 61
6.2.2 Self-supported cables/microducts . 61
6.2.3 Installation of cables with lashing and wrapping . 61
6.3 Indoor installation . 62
6.4 Commission and acceptance of completed networks . 62
6.5 Safety, risks and risk elimination . 62
7 Measurements, documentation and operation. 65
7.1 Measurements . 65
7.2 Labels and marking . 65
7.2.1 General . 65
7.2.2 Notation . 66
7.2.3 Format of documentation . 67
7.2.4 Purpose of documentation . 69
7.3 Operation and maintenance . 69
8 Quality . 70
9 Glossary . 71
Annex A List of standards . 72
Annex B Examples of fibre optic cables – designs vs. application . 81
Annex C Examples of ducts and microducts . 89
Annex D Example of multi-dwelling premises . 91
Annex E Example of areas with private detached or terraced houses . 99
Bibliography . 105

– 5 – CLC/TR 50510:2012
Foreword
This document (CLC/TR 50510:2012) has been prepared by CLC/TC 86A, "Optical fibres and optical fibre
cables".
This document supersedes CLC/TR 50510:2007.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights.

Executive summary
The abbreviation FTTx refers to grids using fibres in the terminal area, meaning beyond the last exchange
Central Office. “x” thereby denotes different penetration levels, for instance:
 FTTC = Fibre to the Curb, meaning to the street (to the last cabinet);
 FTTB = Fibre to the Building, meaning to the building, normally into the basement;
 FTTH = Fibre to the Home, meaning into the residential area.
Most FTTx networks are designed without any active equipment in the external network and are therefore
classified as passive optical networks. The only active equipment is at the central office and the customer
premises. FTTH - PON networks can be designed around different architectures.
The purpose of this Technical Report is to be a first guideline for those considering to install a high
bandwidth (high bit-rate) FTTx-network. After studying the Technical Report operators, communities, energy
companies, installers and others will understand the necessary steps to take to plan and install
FTTx-networks with high quality and cost effectiveness, and to secure a uniform structure and a high quality
level on such networks.
The main part of this Technical Report describes the FTTx-networks, but Clause 2 also contains more
general information to give an understanding as to how these networks fit into the planning of other network
infrastructures.
FTTx has for many years been regarded as the most future-proof technique for transmission of broadband
multi-media applications. The building of FTTx-networks has previously been prevented by high costs. New
investigations show, however, that the cost to install a new fibre based network (100 Mbit/s) is a little less
than to install a new copper network. The FTTx-network is also the only structure, which with certainty can
offer both the present and the future needs, which broadband access services require. At the same time the
technique allows efficient operating maintenance and cost savings.
The networks to be presented are usually called FTTx, but with the strategy described here fibre networks
can reach any point in the network. The end-user can be separate homes, houses, office environments,
optoelectrical transitions in equipment for alarms, surveillance, monitoring devices etc.
The Technical Report also describes recommendations and gives basic requirements to be fulfilled by an
optical fibre installation in an FTTx-network to satisfy present and future requirements on capacity,
transmission distance and network quality. As a target, the minimum capacity is set to 1 Gbit/s (1 000 Mbit/s)
up to 10 km distance. Relevant types of single-mode optical fibres are specified in EN 60793-2-50. However,
in the industry single-mode optical fibre is typically described by the relevant ITU-T recommendations. The
physical network should have an expected lifetime of at least 25 years.
The recommendations are written for a general audience, but in particular for people involved in private and
public enterprises, people responsible for broadband decisions, planning, training and installations.
The Technical Report is divided into eight clauses:
• Clause 1 introduces the term “broadband” and its background.
• Clause 2 introduces the telecommunications infrastructures and provides an overview of the basic
structure for the FTTx network.
• Clause 3 describes system implementations for FTTx including requirements on products and
installation techniques.
• Clause 4 provides guidance on how to create a network and gives an overview of applicable network
topologies.
• Clause 5 provides basic information in relation to various installation practises and the planning
relevant to those practises.
– 7 – CLC/TR 50510:2012
• Clause 6 addresses installation of the FTTx network.
• Clause 7 addresses the testing, documentation and maintenance of the installed network.
• Clause 8 addresses the overall quality.
A number of annexes are included to give deeper knowledge in certain areas. They are broad examples and
can be used to give a better view on the principles for installation of FTTx-networks with cables, microduct
optical fibre cables, microducts and blown fibre units. To some extent these annexes are company specific,
which the reader should be aware of. Annex A (reference [1]) gives a comprehensive list of standards.
References [2], [3], [5] and [6] give a good overview of the present status in ITU-T, IEC and the general
CENELEC view.
Some of the requirements put forward in this Technical Report are unique for an FTTx-network and should
not be used in a general sense for optical networks.

1 Introduction to Broadband
Communication today is digital and therefore sound, pictures, voice, data carried by networks are data
expressed in terms of bit, bytes and their multiples (kilo (k), mega (M), giga (G), tera (T)). A bit (binary digit)
is the smallest digital unit and has only two values: 0 or 1. A byte includes 8 bits and defines the size of a
data file. Transmission capacity of networks and terminals is not expressed by using bytes, but using bit per
second (Bit/s). When a data file is transferred in a network two supplementary bits are necessary. It means
that 10 bits are required for 1 byte.
A subscriber who wants to download or upload a large file must wait for data transfer to be accomplished.
This time depends on the file size; say 100 MB, and transmission speed. In most networks, like VDSL or
cable, transmission speeds are asymmetrical, with download (data transfer towards the user) being faster
than upload (data transfer from the user), e.g. 100 Mbit/s and 4 Mbit/s, respectively commonly offered using
DOCSIS 3.0 technology. At these speeds, it takes just 8 s to download a 100 MB file, but as much as 200 s
(3 min 20 s) to upload it. In ADSL networks, typical download and upload speeds are 15 Mbit/s and 1 Mbit/s,
corresponding file transfer times being 53 s and 800 s (13 min 20 s) respectively.
Actual transmission speed in many networks is lower than advertised and vary with traffic load due to
oversubscription of shared system capacity. This problem does not exist in point-to-point (P2P) fibre
networks without capacity sharing, where 1 Gbit/s symmetrical transmission speed is currently possible.
While users of passively split FTTx network do share common capacity, it is large, for example 2,5 Gbit/s in a
GPON system, so fast and reasonably symmetrical service can be offered, like 100/50 Mbit/s or 100/25
Mbit/s.
The following table gives examples of transmission times for downloading a 6,25 GB file with high quality
DVD movie.
Transmission speed Download time Access technology
0,128 Mbit/s 5 days, 8 h Dial-up
10 Mbit/s 8 h VDSL
100 Mbit/s 48 min DOCSIS 3.0,GPON, EPON
1 000 Mbit/s 50 s P2P fibre access

We do not know all future applications, however existing technologies of today, such as video on demand
and the exchange of medical data e.g. for Ambient Assisted Living (AAL), offer an outlook on the future
usage of broadband networks.
For the purpose of this document the following classifications will be used:
− low bit rate transmission: up to 1 Mbit/s
− medium bit rate transmission: 1 up to 10 Mbit/s
− high bit rate transmission: 10 up to 100 Mbit/s
− Very high bit rate transmission: 1 Gbit/s and more.

– 9 – CLC/TR 50510:2012
2 Network Structure and Nodes
2.1 General
This clause provides an overview of the FTTx networks and provides a foundation for any terminology and
references made from subsequent clauses in this Technical Report.
2.2 Network Layers
2.2.1 Overview
For a level-designed view on the components in the build-up of the infrastructure, see Figure 1.

Figure 1 – Network layers
From the bottom up, Figure 1 shows the following network layers:
 Physical routing: Duct for cables, for microduct optical fibre cables, and for microduct fibre unit cables
(blown fibre products) and for structures for antennas
 Passive transmission and interconnecting media: optical fibre cable, connectors, antennas, boxes,
closures and their physical interconnections
 Active transmission systems: Logical connections over a physical connection
 IP: The internet operator network service to the user
 Application: Equipment, program and data bases of the user
Designing the infrastructure in layers makes it possible for different ownership of individual layers. This
creates possibilities for open networks and competition, but also presents risks regarding responsibilities and
long-term interaction.
2.2.2 Physical routing
The lowest layer in the physical network is the physical routing. It consists of ducts in standard dimensions,
antenna structures, network components and microducts among others. Also existing infrastructure tubing
such as sewer-, gas-, and drinking water tubes may be used. The physical routing should have an expected
lifetime of 25 years.
This Technical Report describes the physical routing as applied to FTTx infrastructures. Most of the cost for
a broadband network is in the planning and installation of the routing layer. It is therefore important to be
accurate in planning, installation and documentation, and that the material of the parts used is of high quality.
Applying an advanced Network Software Suite for the design, deployment and registration of the passive
network, as readily available today, is essential to optimize the network design and to reduce costs. Normally
the network owner owns this level.
2.2.3 Passive transmission media
This layer contains optical fibres (cable, microcable, indoor- and outdoor-cable, blown fibre units etc.),
interconnecting devices (connectors, splices, closures etc.), copper cables (not treated here) and antennas
for wireless access (FWA, WLAN, 2G, 3G, 4G, LMDS, LTE) as well not treated here.
This Technical Report describes the passive transmission media as applied to FTTx infrastructures.
The installation of single-mode optical fibres within FTTx-networks provides the longest operational lifetime
due to its transmission performance. Cables containing those optical fibres are expected to have design
lifetimes consistent with those of the physical routing components of 2.2.2.
Cables should be installed in ducts to minimise costs where network growth requires additional cables to be
installed and when cables need to repaired or replaced.
The network owner typically owns the cables and the optical fibres.
2.2.4 Transmission-, IP- and application layer
The transmission-, IP- and application layer will not be described in this Technical Report.
2.2.5 Ownership, operating and maintenance
When all parts in the infrastructure fulfil specified quality requirements regarding transmission and
installation, different ownerships could be possible. Ownership and operation could be split by different
governmental or community companies, jointly owned companies between different communities, energy
companies, building enterprises. Housing co-operatives, house-owner associations, private persons and
landowners may also own the local network closest to the end-users.
Considering operation and maintenance the network level owners have to specify acceptable downtimes.
2.3 Network topology – Terminology
2.3.1 Overview on Infrastructure
To get an overall picture of optical fibre networks it is necessary to explain some of the terminology and
concepts used.
– 11 – CLC/TR 50510:2012
Figure 2 – The network is hierarchically built up
The traffic volumes and requirements for capacity, functionality and availability increase with the network
level. Therefore the strategic significance and requirements for protection and security also increase in the
higher network levels. All IP-traffic can be distributed, which means that this hierarchy may be flattened in a
few years. The present network is a combination of a traditional telephone- and a future IP-network, which
can be described as in Figures 2 to 7. This means that the information can find the best route when
alternative routes are available.
The highest level is the national network, see Figure 2 and the lowest (colour-marked) is the network for
connecting end-users or subscribers and is focussed on in this Technical Report.
2.3.2 National network
The national network connects all regions in the country and is connected to international networks. This
type of network has a very high security level. A national network has normally few owners.
2.3.3 Regional network
A regional network or a community-connecting network connects networks within a region. Networks within a
region often consist of municipality-connecting networks from different communities. A regional network is
then connected to the national network.

Figure 3 – A regional network, e.g. in a county

Some of the municipality-connecting networks can be connected to nearby regions (Figure 3).
2.3.4 Municipality connecting network
Municipality-connecting networks connect different municipalities (places) within a community. These
networks are in turn connected upwards to regional networks or community-connecting networks and
downwards to access networks. The connection is made through the community main node.

Figure 4 – The municipality-connecting network connects the larger places within a community
In each place there are one or more nodes, access nodes (possibly also distribution nodes), which connects
the end-user – the subscriber (Figure 4).
2.3.5 Metropolitan or urban network
City (metropolitan) or urban networks are networks within a city or in a sparsely populated area. The function
is to give a broadband infrastructure, which meets a long-term need using cost-effective solutions enabling
the access networks to reach subscribers. This can be achieved by using existing or planned networks of
different kinds. These networks are directly connected to the main node or to a distribution node
(redundancy). Access nodes are connected along the ring structure (Figure 5).

Figure 5 – The metropolitan or urban network, the red lines, connects areas in a thinly populated area

– 13 – CLC/TR 50510:2012
2.3.6 Access network
The network levels described in 2.3.2 to 2.3.5 are normally installed on public land. In contrast, parts of the
access network may be installed on private properties or land. Subscribers from houses, terraced houses,
blocks of flats, companies, hospitals and authorities can be connected to the access network. Also masts for
FWA (Fixed Wireless Access) or WLAN (Wireless LAN) and antennas for the mobile network can be
connected. Furthermore equipment for security, surveillance, fire-alarms and control equipment can be
connected.
Figure 6 – The access network connects a large number of end-users
2.4 Nodes – Topology and Terminology
2.4.1 Overview
There are a number of junctions (also known as nodes) in a broadband network, where single traffic flows
are mixed, multiplexed and de-multiplexed to create an efficient flow through the network. In the nodes the
routing and switching of the data packages is performed. Joint traffic between different network owners or
operators is also possible. The largest number of nodes will be used for the connection of the
end-customers.
The nodes are spaces filled with transmission equipment, ODFs (Optical Distribution Frames), cross-connect
devices, splice boxes, uninterruptible power supplies and equipment for climate control.
The design of the access node will be briefly described in the following but other types of nodes will not be
discussed, except for a few comments.

Figure 7 – Node hierarchy
2.4.2 National node
A national node is connected to several national and international networks and therefore have to have a
high security level.
2.4.3 Regional node
A regional node is connected to a national network, regional and municipality network.
2.4.4 Main node
There are main nodes in a community which are connected to a regional network or a municipality-
connecting network in the same community. Such a node should contain equipment and connections to the
higher level network to provide redundancy.
In small places the end-user may be connected directly to a main node through the access network.
2.4.5 Access node
The access node is connecting the metropolitan network with the end-user via the access network.
It will be described more in detail later in the Technical Report.

– 15 – CLC/TR 50510:2012
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Figure 8 – A comprehensive picture over a community network
2.5 Examples of FTTx topologies
The following four pictures give some simple illustrations of to P2P and passive optical networks (PON). P2P
is in general passive, where one fibre from central office is routed directly to the customer and does not use
splitters. For PON (in general point to multi point) one fibre from the central office is shared among a number
of customers (usually 32) by the use of one passive splitter located within the network. For example, in a
“converged PON” a number of passive splitters are located together, whilst in a “distributed PON” each
passive splitter is located separately within the network.
The pictures are examples from different countries in Europe. See also the Glossary. PON can also be
explained as power splitting point-to-multipoint.

Figure 9 – Example for a Point-to-Point/Access Network

– 17 – CLC/TR 50510:2012
Figure 10 – Example of a Metro/Access Network

Figure 11 – Second example of a Metro/Access Network

Figure 12 – Example for a Passive Optical Network (PON)

2.6 FTTx in the access network
2.6.1 Overview
The network, which connects each end-user to the access node, is called the access network. The network
is normally part of the real property. The access network may consist of a network inside a house and/or a
network between several buildings. It can therefore include an area with block of flats, houses, industrial
areas, schools, hospitals or offices.
The access network is the most complex network within the fibre optic IT-infrastructure. Each access
network is unique and requires special planning to be optimised in all aspects. The reader is assured that
there are a number of solutions, which can be used as a base, see Annexes D and E.
2.6.2 FTTx in access networks
FTTx is often called the fibre access network. Here it is defined as the connection from a USER NODE in
e.g. a private home to an ACCESS NODE. It is therefore the part of the IT-structure, where there is not a
general redundancy requirement the fibres and can be connected like a star from the access node to the
user, see Figure 6.
Note that in many areas with privately owned access networks the active equipment is placed close to the
building in a house property node. This network will therefore be rather short in distance. A number of
property nodes are then concentrated to an access node. This structure implies in many cases lower costs.
Even working and maintenance expenses will increase for an area with active equipment in several nodes.

– 19 – CLC/TR 50510:2012
3 FTTx passive network products and system implementations
3.1 General
This clause provides information on optical fibres, connectors, splices, link designs and optical power
budgets. Although optical fibre cables look similar to copper cables on the outside there are many
differences in relation to design and handling. This clause discusses optical fibre cable technology and
various installation techniques.
3.2 Optical fibres
3.2.1 Triple play and general about new fibres
In telecommunications, triple play service is a marketing term for the provisioning of two bandwidth-intensive
services, high speed internet access and television, and a less bandwidth-demanding (but more latency-
sensitive) service, telephone, over a single broadband connection.
Typical transmission wavelengths used for downstream are 1490 nm and 1550 nm and for upstream
1310 nm. Therefore it is important to understand what kind of problems may occur depending on
wavelength. Is it a microbend or macrobend problem?
Added loss due to microbending occurs when localized lateral forces along the length of the fibre appear.
These may be caused by manufacturing and installation strains, as well as dimensional variations in the
cable materials due to temperature changes. Sensitivity to microbending is a function of the difference of
refractive index of the core and the cladding, and diameters of the core and cladding. Coating structure and
material property have also an influence.
The effect of microbending in single-mode fibres is increasing optical loss at 1310 nm, 1550 nm and 1625
nm wavelength ranges as opposed to macrobend effects in single-mode fibres that are primarily is present at
the longer wavelengths of 1550 nm and 1625 nm.
To reduce microbending losses the cable structure must protect the optical fibres from lateral forces. Loose
tube cable construction should be optimized to prevent buckling of the fibre in the tube during temperature
changes leading to possible macrobending as well as microbending loss.
Cable components such as the cable sheath and the strength member are important because they also help
to reduce the microbending caused by the external mechanical forces on the cable and by temperature
changes.
Microbending losses may also be introduced in aerial cables subjected to excessive elongation (e.g. heavy
ice loading).
Since 2006 an optical bend-insensitive single-mode fibre has been added as a new fibre category: ITU-T
G.657 “Characteristics of a bending-loss insensitive single-mode optical fibre and cable for the access
network”. The rationale behind this new fibre was a demand to install fibres with tighter bends. However, the
most common fibre today is still ITU-T G.652.D.
3.2.2 Choice of optical fibre type
The choice of optical fibre is determined by several parameters. The most important are:
 system costs,
 distance,
 transmission bit-rate.
The advantages of a single-mode fibre are high transmission capacity and low optical attenuation. If a
single-mode fibre is used in FTTx, the same type can be used throughout the network, which gives
transparency and uniformity. This also simplifies service, maintenance and new developments. Another
advantage is that only tools and instruments for single-mode fibres need to be procured.
Table 1 – Single-mode fibre types as defined in ITU and EN/IEC

Single-mode (SM) EN/IEC 60793-2-50 ITU-T
Unshifted dispersion B1.1 G.652.A, B
Cut-off-shifted B1.2 G.654
Low water peak B1.3 G.652.C, D
Bending loss insensitive
B6_a1, a2, b2, b3 G.657.A1, A2, B2, B3
unshifted dispersion
Dispersion-shifted B2 G.653
Nonzero dispersion-shifted B4 G.655, G.656

For FTTx-infrastructures single-mode optical fibre should be used. Recommended types a
...