Structured Cabling Systems - Ten Step Guide
Below we have provided a ten step introductory
guide for the Design of Structured Cabling Systems and IT Network
group of standards will you conform to?
of the World
three principle design standards give the details of how to design and specify a
structured cabling standard, they are;
standards in turn however refer to hundreds of other standards relating to
component specifications, fire performance, testing methods, containment systems
cabling - Basic rules
cables are run from user positions to a patch panel. At the patch panel, patchcords link into the active LAN
equipment or into backbone cabling. The
user position has a wall outlet or floor outlet, and this links into the PC on
your desk via another patchcord. The
outlet is a called a TO (Telecommunications Outlet) and contains an eight way
plug meeting IEC 60603-7, more
commonly referred to as an RJ-45.
Two outlets per work area
outlets per 10 square metres of useable floor space
to be within 3 metres of the user station
outlets to be RJ 45
cable run to be 90 m
total length of patchcords at both ends of the link to be 10 m
and RJ45 to be Cat5e grade
3 or optical fibre can be used
optical fibre, select 50/125 or 62.5/125 multimode
using fibre select SC or ST connectors
6/Class E can be specified
5e Cable can be unscreened, UTP, Foil
screened, FTP, or Foil and Braid screened S-FTP.
fire performance can be:
IEC 332-1, IEC 754, IEC 1034
IEC 332-3-c. IEC 754,
UL 910 plenum
grade, in ascending order, has a better performance in fire situations but at a
correspondingly higher price.
exact density of cables, number of outlets and their position is up to the end
user, or else at the proposal of the installer/designer
All of the horizontal cables
are star-wired back to Telecommunications Closets or Floor Distributors where
they are terminated in patch panels. These
patch panels are connected together via the building backbone cabling which can
be up to 500 metres long. It can be
copper cable but is more likely to be optical fibre, either multimode or
singlemode. The kind of cables and
the number of cores needs to be decided.
The campus cabling links different buildings together.
It can be up to 1500 m long. It can be copper cable but is more likely to
be optical fibre, either multimode or singlemode.
The kind of cables and the number of cores needs to be decided.
and design of Telecommunications Closets to link horizontal and backbone
and design of the equipment room as a central focus for the main computing, LAN
and PABX equipment.
and design of the Service Entrance facility whereby outdoor cables are
terminated and the point of demarcation between customer owned equipment and the
PTT cables is defined.
containment system. How will the
cables be protected? Within
buildings the choices are;
following must be taken into account:
density and volume of cables to be organised
aesthetic appearance of the cabling within offices and other visible areas
of different schemes
to power cables and other potential sources of interference
building standard for
telecommunications pathways and spaces
||Information technology – cabling installation
external applications the choices are;
buried cable trench
supporting aerial cable
aerial cable, i.e. catenary or messenger wire
to building exteriors
all cases the designer must ensure that all civils work has been carried out,
rights of way established and availability of cable ducts and manholes
established. Aerial cable routes
must keep a minimum distance away from power cables and all external cables must
be selected for the environment and temperature ranges in which they are
expected to survive. External
copper cables usually need to be protected by overvoltage and fault current
devices where they enter a building.
Administration system. The cabling
and its containment system need to be clearly identified and their locations,
routes and capabilities recorded in a cable
administration system. This usually
involves a logical numbering scheme that can be applied to all cables, outlets,
patch panels and even containment systems.
Various colour schemes are also available.
schemes can be paper based but for the larger installations then a computer
based system is advisable. There
are several proprietary solutions on the market which offer various database and
graphical methods for keeping track of cabling assets.
Some systems are also active in that they can detect moves and changes
and automatically update the database.
||Administration standard for
the telecommunications infrastructure of commercial buildings
technology – cabling installation
All exposed metallic elements of the cable system and cable containment
system need to be earthed (grounded) for safety and also electromagnetic
compatibility requirements. If
screened cables are used then special attention must be given to effective
bonding of the screening elements. Poorly
earthed screened cabling may behave worse than unscreened cabling.
An electrically ‘clean’
earth must be available at all points where the cabling is terminated, but
especially within telecommunication closets, equipment rooms and service
entrances. A clean earth is usually defined as a conductive element with
not more than 1 volt rms potential difference between it and the real earth down
below. Copper cabling linking two
different buildings can suffer from earth loops if the ground potential is
different. Non-metallic optical
cabling is usually picked for problem areas such as these.
Some useful standards are;
of equipotential bonding and earthing at premises with information
Technology, Cabling installation, part 2, Installation, planning and
practices inside buildings
||Commercial Building Grounding and Bonding Requirements
regime. All cables must be tested
to demonstrate compliance with the standards and specification to which they
were bought. Testing can be split
into copper cable testing and optical fibre testing. Ideally all cables should be 100% tested.
are five manufacturers of hand held copper cable testers that will automatically
test the installed cable plant for all the expected parameters.
By the use of a remote injector, the cabling is tested from both ends,
which is a condition of the standards. The
cabling has to pass all of the suite of tests to be awarded and overall pass. Points to remember are;
is being tested? the channel (i.e. end-to-end including all the patchcords) or
the basic link (i.e. the permanently installed cable from outlet to patchpanel).
The test figures are different for each setting.
It is usually more practical to test the basic link (also referred to as
the permanent link).
level is being tested? The tester
should normally be set to Cat5e link or Class E link if Category 6 cable is
results are stored electronically and must be in a format recognisable by the
cable management software that comes with the tester. There are now numerous test standards and draft standards.
The most influential is likely to be;
specification for the testing of balanced generic cabling in accordance with
tests required are;
NEXT pair to pair
ELFEXT pair to pair
DC Loop Resistance
length and ACR are also useful additions to this set of tests.
All that needs to be tested
with short distance multimode optical cables is attenuation.
This can be achieved by a device called a light source and power meter.
This device will simply measure the absolute loss across the optical
link. This then has to be compared
with the design value of attenuation. If
the tested value is less than the design value then the link can be seen to be
Time Domain Reflectometers can give a great deal of information about optical
fibres, but for short haul multimode fibre they are an expensive overkill that
gives results that need expert interpretation.
An OTDR remains an essential tool for fault finding.
the design of the cabling system in-step with the LAN aspirations of the end
user? For example, Cat5e is the
minimum performance grade suitable for gigabit Ethernet. Standard Cat5 cable may not have sufficient delay skew
performance for RGB video systems however.
Cat 6 cabling will give a longer service life due to its higher
performance, but at an initial higher cost.
optical fibre LANs, e.g. gigabit Ethernet cannot transmit over the full distance
allowed in standards based optical structured cabling.
These LAN limitations have to be taken into account.
The next generation of 10 gigabit Ethernet will need a new generation of
optical fibre to make it work.
best way to ensure success in a structured cabling installation is to use
properly trained people to design, implement and test the system.
The RCDD qualification from BICSI is the only qualification which covers
all aspects of structured cabling design and implementation.
above information is offered as a summary of ISO 11801 and related standards.
It is not a definitive design guide and does not replace study and
implementation of the Standards themselves.
The publisher accepts no responsibility for inaccuracies or omissions.
To purchase the full Standards go to your national standards body, e.g.
British Standards Institution, Nederlands Normalisatie Instituut etc. or ISO.
advice and a free consultation is available from one of our consultants John