cabling
COPPER AWE
The launch of Category 8.2 cable systems is set to transform data centre
infrastructures as a cost effective alternative to fibre optic for 40GBase-T
applications, as Lee Stokes of Draka UC Connect explains.
T
he amount of digital
data in the universe is
growing exponentially
as increasing numbers
of people, businesses
and devices connect to the Internet.
Experts predict the quantity of digital
data will double every two years
heaping pressure on data centres
and their cable infrastructures to
continue to maintain capacity without
a degradation of service.
In July 2012, industry
representatives decided that a copper
cable capable of handling 40Gbps
of data was worth developing. Now,
three years after that announcement,
cable and systems manufacturers are
now launching Category 8.2 copper
cabling systems. The introduction
means some leading manufacturers
can now offer the choice of both
40Gbs copper and 40Gbs fibre optic
data cabling.
The 40GBase-T copper system
is targeted primarily at data centre
applications. It will be particularly
useful for applications where cable
installers are more familiar working
with copper cabling for both endof-row (EoR) and top-of-rack (ToR)
architecture. The system will also
provide operators and installers with
a cost effective alternative to fibre
optic systems by enabling them to
take advantage of the reduced cost of
copper compatible switches.
The preferred way of connecting
servers to switches in data centres is
over twisted-pair cable. It is a fact that
88 per cent of all switch-to-server
links are typically less than 30m. The
standards bodies have recognised
this statistic; as a consequence,
all three bodies – the TIA, ISO and
IEEE – have deemed the maximum
link length for both 25GBase-T and
40GBase-T to be 30m.
At 30m, the Category 8 linklength is shorter than link-lengths for
other cable categories. The shortened
length is necessary, however,
because above 30m attenuation
results in the link’s performance
dropping to an unacceptable level.
For reference, the 30m maximum
length is defined as an assembly of
three cable sections: a 26m long
installation cable and a 2m long patch
cable at each end.
Significant differences
It is important to be aware that while
the maximum length of reach is
broadly similar in all 25GBase-T and
40GBase-T cable standards, there
are significant differences between
the standards when it comes to
defining backwards compatibility.
The North American standards body
the TIA, for example, has broken
with convention with its definition
of Category 8 in that it does not
require the system to be backwards
compatible with Category 7A or
Category 7 systems but it does
have to be compatible with Category
6A, Category 6 and systems with a
lower specification.
21