EW September 2016

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Technical article
September 2016 70
A New Flat Indoor/Outdoor
Drop Cable for FTTH
Applications
By Qin Yu, Fei Qian, Liming Chen, Qingqing Qi, Shiying Wang, Huiping Shi, Cheng Liu
FiberHome Telecommunication Technologies Co Ltd
Abstract
This paper presents a new flat indoor/
outdoor drop cable for FTTH application.
The flat cable is all dielectric and with an
oblong cross section, and could be applied
to harsh environments with large bending
stress, lateral pressure or wind load.
Therefore, the flat cable is conducive
to the realisation of large-span aerial
installation and is particularly suitable for
the indoor and outdoor drop application
in the FTTH access network.
In this paper, three different combinations
of materials are explored to verify the
processing performance and product
properties of the cable. That is, different
combinations of sub-unit material and
outer sheath material.
Eventually, it was found that the two kinds
of the cable structure could totally satisfy
the users’ requirements and have excellent
transmission, mechanical and flame
retardant characteristics, and could apply
in the FTTH applications.
1 Introduction
In order to realise the tri-networks
integration as soon as possible, operators
in China continue to promote large-scale
FTTH network construction.
A FTTH network can not only provide
higher bandwidth, but also improve the
anti-interference performance of the
access network and integrated access
capacity of service.
To meet the different demands of users,
there are many types of FTTH optical cable
for unceasing requirements from users,
such as different demands of construction
costs, convenience and rapid cable laying,
and the reliability of the optical fibre
communication lines. Therefore, it is very
important to choose an appropriate cable
for different drop applications.
2 Common drop
cables
In general, drop cables are small count
fibres with special designs, and most drop
cables are of self-supported structure with
tight buffer fibres.
The most common shapes of drop cables
are figure-8 bow-type cable, round cable,
or some other special drop cables, such as
low friction bow-type cable and invisible
micro cable and so on. In the present drop
applications, the figure-8 bow-type cable
and round cable were used widely. As new
drop cables, low friction bow-type cable
and invisible micro cable were gradually
accepted by more and more users.
Although drop cables become ever more
diverse, different kinds of drop cables
usually have the following characteristics:
• Diversified and rational structure,
could satisfy the users’ special
requirements
• Smaller size and can save laying space
• Easy to branch and save construction
time and money
• Easy to manufacture and can keep
the continuity and consistency of
processing
• Easy to install, maintain and replace
3 Structure of the
flat cable
3.1 General structure of the flat cable
The flat cable developed for this paper was
to satisfy the customers’ requirements for
indoor and outdoor drop applications with
both aerial and duct construction.
The cable should have good directional
bending properties and excellent ability
to resist lateral pressure. Moreover, the flat
cable with oblong sectional profile should
effectively reduce the destructiveness
induced by wind load, and be adaptable to
various harsh construction conditions and
a complex environment.
Given the specific application
environment, the flat cable was designed
with an outer sheath, sub-unit sheath,
tight buffered fibre, FRP and strength
member. See Picture 1.
Outer sheath
Sub-unit sheath
Tight buffered fibre
FRP
Strength member
▲ ▲ Picture 1: The cross section of the flat cable