Specifications

28
Black Box Guide to Structured Cabling
Section NameSection Name
Installation & Testing
Copper testers.
If all these tests seem a little overwhelming,
they are. But there’s help—professional technicians
and professional-grade test equipment. Trained
technicians know how to use the advanced Level III
and IV equipment that automatically tests, calculates,
and certifies your copper cable links in accordance
with TIA and ISO standards. Level III equipment is
designed for measurements to 250 MHz. Level IV
testers certify accuracy up to 600 MHz. Manufacturers
of test equipment are conforming to the changes in
standards with firmware updates.
The results of the tests will tell you if your system
meets all the applicable performance standards.
If there are problems, the technicians and the
* ACRF (Attenuation to crosstalk ratio, far-end) is replacing ELFEXT
in the CAT6a proposed draft.
** PSACR-F (Power sum attenuation to crosstalk ratio, far end) is replacing
PS-ELFEXT in the CAT6a proposed draft.
NOTE: PS-ANEXT (power sum alien near-end crosstalk) and PS-AACRF (power
sum attenuation-to-alien crosstalk ratio, far-end) are new measurements.
Copper Performance Comparison at 100 MHz
CAT5e CAT6 CAT6a ISO Class F (CAT7)
Standard
TIA-568-B.2 TIA-568-B.2-1 TIA-568-B.2-10 ISO/IEC
draft 11180*
Insertion Loss
Channel 24.0 dB 21.3 dB 20.8 dB 20.8 dB
Permanent Link 21.0 dB 18.6 dB 17.9 dB 17.7 dB
NEXT
Channel 30.1 dB 39.9 dB 39.9 dB 62.9 dB
Permanent Link 32.3 dB 41.8 dB 41.8 dB 65.0 dB
PS-NEXT
Channel 27.1 dB 37.1 dB 37.1 dB 59.9 dB
Permanent Link 29.3 dB 39.3 dB 39.3 dB 62.0 dB
ELFEXT (ACRF*)
Channel 17.4 dB 23.3 dB 23.3 dB 44.4 dB
Permanent Link 18.6 dB 24.2 dB 24.2 dB 46.0 dB
PS-ELFEXT (PSACR-F**)
Channel 14.4 dB 20.3 dB 20.3 dB 41.4 dB
Permanent Link 15.6 dB 21.2 dB 21.2 dB 43.0 dB
Return Loss
Channel 10.0 dB 12.0 dB 14.0 dB 12.0 dB
Permanent Link 12.0 dB 14.0 dB 6.0 dB 14.0 dB
PS-ANEXT
Channel — — 60.0 dB —
Permanent Link — — 61.1 dB —
PS-AACRF
Channel — — 37.0 dB —
Permanent Link — — 37.8 dB —
equipment can help isolate the problem. Better
yet, the equipment saves all the test results for
downloading and proper documentation.
10-GbE considerations.
In June 2006, the IEEE approved the standard for
10-Gbps Ethernet, or 10GBASE-T (10-GbE). 10-GbE
transmission requires a bandwidth of 500 MHz. The
industry is using two different cables for 10-GbE
applications: Category 6 (CAT6) cable and
Augmented Category 6 (CAT6a).
Alien crosstalk.
Before discussing how to test CAT6 and CAT6a
in 10-GbE, a definition of alien crosstalk is needed.
Alien crosstalk (ANEXT) is a critical measurement
unique to 10-GbE systems. Crosstalk, measured in
10/100/1000BASE-T systems, is the mixing of signals
between wire pairs within a cable. Alien crosstalk
is the measurement of the signal coupling between
wire pairs in different, adjacent cables.
The amount of ANEXT depends on a number of
factors, including the proximity of adjacent cables
and connectors, cable length, cable twist density, and
EMI. Patch panels and connecting hardware are also
affected by ANEXT.
With ANEXT, the affected cable is called the
disturbed, or victim, cable. The surrounding cables
are the disturbers.
10-GbE over CAT6.
CAT6 cable must meet 10-GbE electrical and
ANEXT specifications up to 500 MHz. However, as of
mid 2007, the CAT6 standard specifies measurements
only to 250 MHz and does not specify an ANEXT
requirement. There is no guarantee CAT6 can support
a 10-GbE system. But the TIA TSB-155, ISO/IEC 24750,
and IEEE 802.3an all characterize 10GBASE-T over UTP
cabling.
The TSB provides guidelines for ways to help
mitigate ANEXT. One way to lessen or completely
eliminate ANEXT is to use shielded equipment and
cables such as Black Box’s S/FTP or F/UTP cables (see
blackbox.com). Another way is to follow mitigation
guidelines, such as using non-adjacent patch panels,
separating equipment cords, unbundling cabling, etc.