Submittal

0711CIMinstallF1
PSANEXT performance comparison
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PSANEXT
(db)
Frequency (MHz)
Category 6
IEEE limit
Category 6A UTP
Category 6 ASTP
100 200 300 400 500 600
installation
W
ith the publica-
tion of the IEEE 802.3an
10GBase-T standard in 2006,
Augmented Category 6 (i.e., Category 6A) cabling sys-
tems are being deployed in data centers. Due to the high
electrical frequency needed to support 10-Gbit/sec
data rates over copper cabling, the mitigation of signal
coupling between cables in close proximity, known as
alien crosstalk (alien near-end crosstalk or NEXT, and
alien equal-level far-end crosstalk or ELFEXT, which
is also called alien attenuation-to-crosstalk-ratio at
the far end, or AACRF), is critical to meet 10GBase-T
performance standards.
Shielded Category 6A links oer clear performance
benets at 10 Gbits/sec by reducing or eliminating the
eect of alien crosstalk and providing superior immunity
to electromagnetic interference (EMI), such as radio-fre-
quency interference (RFI). But it is impor tant that shielded
cabling systems be properly bonded and grounded to
ensure the highest level of performance and to protect
expensive IT equipment. If shielded cabling systems are
not properly designed and/or installed, transmission
errors may occur due to unwanted additional noise.
Let’s consider the performance benets of shielded
twisted-pair structured cabling, and answer the follow-
ing top-of-mind user questions on bonding and ground-
ing best practices:
•Where,andhowoen,shouldtheshieldedcabling
system be bonded?
•Howcan I tell ifmyexistinggrounding system is
adequate for shielded cable?
•HowcanItellifground-loopproblemsexistatthe
workstation, and what can be done about the loops?
Performance benefits of 6A
Copper is the preferred structured cabling medium
for most connections in the data center and horizontal
links to the workstation due to its easy termination and
installation in the eld, and cost-eective electronics. Of
the available copper cabling types, unshielded twisted-
pair (UTP) Category 6A copper solutions are specically
designed to reduce the eect of alien crosstalk by incor-
porating innovative features into both the cable (such as
increased separation between cables and tighter twist
rates) and the connectors (such as crosstalk suppression
within the printed circuit board).
Shielded Category 6A systems oer a dierent tech-
nique to suppress alien crosstalk, using foil and/or
braided shielding within the cable to prevent signals
from coupling between cables. ese screens provide
signicant margin over IEEE 802.3an specications for
power-sum alien near-end crosstalk (PSANEXT) and
power-sum alien attenuation-to-crosstalk ratio at the
far end (PSAACRF), virtually eliminating the eect of
alien crosstalk and providing more than 20 dB of head-
room over comparable UTP systems. is impact is sim-
ilar whether the cable contains individual shields around
each pair or a single foil around all pairs.
e increased suppression of ANEXT and AACRF by
shielded cables also eliminates the need for costly and
Power-sum alien near-end crosstalk performance characteristics
of copper cabling systems over a 100-meter channel.
Make the right connection:
Bonding a shielded system
Bonding the system to ground helps ensure
optimum performance of your shielded system.
TOM TURNER is business development manager and ROBERT
DENNELLY is product line manager at Panduit Corp. (www.panduit.com).
Reprinted with revisions, from the November 2007 edition of CABLING INSTALLATION & MAINTENANCE
Copyright 2007 by PennWell Corporation