Network Communications News (NCN) May 2016 | Page 24

S P E C I A L F E AT U R E

copper cabling systems

The cabling supplier should provide reliable materials.

possible and allowing air to circulate. Data
centre cable management is one of the
most important aspects of data centre
design and operation. The performance,
reliability and flexibility of the data centre
are all tied in strongly to the systematic
execution of this ongoing activity. Logical
naming that will uniquely and easily
identify each cabling in the data centre
can greatly accelerate cable tracking and
thus the troubleshooting process. Removal
of unused cables, although all too often
overlooked, is a must. Apart from being a
general inconvenience stray cables raise
more serious concerns such as restricting
airflow thereby reducing cooling efficiency.
Valuable space can be saved with
good cable management to the extent
that energy consumption is improved.
With good strain relief, cables lie in a
straight line and cannot be twisted. This
is an important prerequisite for stable
signal transmission in copper cables and
enhancing cable longevity.

PoE
Facilitated by current network
convergence trends, PoE combines
power and data transmission. This allows
network devices to be powered using
copper data cabling, helping reduce

Matthias Gerber has
been market manager
LAN cabling at Reichle
& De Massari (R&M)
for the past four years
and has worked for the
company in a variety of
different roles since 1994.
He began his career at
R&M as HF development
engineer and manager of
technical laboratory.

installation costs and makes ongoing
maintenance easier and cost effective.
When the PoE standard was
introduced a decade ago it supported
up to 12.95W. The next version was
introduced in in 2009: PoE+ supported
up to 25.5W and today, PoE can power
devices over considerable lengths of
data cable.

Physical limits
Supplying current to Ethernet devices
through data cables that are already in
place seems like a brilliantly simple idea.
The supply current for the Ethernet device
simply flows directly through the data
cable. However, there are certain factors
– physical limitations in particular – that
need to be dealt with in order to make the
most out of Power over Ethernet.
One type of physical limitation is
link length. As the current causes the
cable to warm up, the attenuation
increases which reduces the possible
transmission range. This is particularly
true of the new 4PPoE (4-Pair Power
over Ethernet) with a power of 55 or
100W, where up to one ampere can flow
through each twisted pair.
Category 5e installation cables with
an AWG 24 (0.22mm2) conductor cross
section reach their ‘natural limits’ quite
quickly. They grow hot fairly rapidly,
especially when heat is not being
efficiently conducted away from large
cable bundles. Category 6 or Category
7A cables with AWG 23 (0.26mm2) or
AWG 22 (0.33mm2) cross sections offer
reduced resistance.

Energy saving properties
PoE can help LANs use energy in the
most efficient, environmentally sound
way possible. Its adoption is largely

driven by the increasing availability of
new products that can be powered via
PoE technology. However, if the cabling
doesn’t support the protocol, it could be
a huge disappointment. One method of
avoiding this is by using shielded cabling
and higher categories than might appear
strictly necessary at first.
There are several ways in which
future demand for PoE applications and
requirements could be accommodated.
Increasing efficiency, for example, or
increasing the power load by energising
four available cable pairs, instead of
the two that are normally utilised.
4PPoE has clear benefits in the area of
diminishing cable resistance, thereby
preventing power losses. This not only
reduces the environmental impact of
PoE, but can also deliver significant
savings to operators large networks.
As the role of the LAN continues to
develop, exponential growth of the
number and size of facilities is likely
to continue. Every option for energy
saving, however small, can help.
In most cases, it can be shown that
when realistic framework conditions are
in place with applications up to Power
over Ethernet Plus (PoEP, 26W power),
transmission length restrictions rarely need
to be taken into acco