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Installation & Testing

10-GbE over CAT6a.

Augmented Category 6 (CAT6a) and Augmented

Class E (Class E

) cabling are designed to support

10-GbE over a 100-meter horizontal channel.

The TIA/EIA-568B.2-AD10 (draft) extends CAT6

electrical parameters such as NEXT, FEXT, return loss,

insertion loss, and more to 500 MHz. The CAT6a draft

specifies near- and far-end alien crosstalk (ANEXT,

AFEXT) to 500 MHz for closely bundled “six around

one” cable configurations. It also goes beyond IEEE

802.3an by establishing the electrical requirements

for the permanent link and cabling components.

The ISO Class E

standard will be published in a

new edition of the 11801 standard.

These standards specify requirements for

each component in the channel, such as cable and

connecting hardware, as well as for the permanent

link and the channel.

Testing 10-GbE.

Field certification for 10-GbE consists of two

phases. The first is to certify the transmission

capability and quality of each individual link. The

10-GbE test limits are identical to CAT6 and ISO 11801,

but the frequency range is extended from 250 MHz

to 500 MHz. The parameters are insertion loss, return

loss, pair-to-pair near-end crosstalk (NEXT), power-

sum NEXT, pair-to-pair equal-level far-end crosstalk

(ELFEXT), Power-Sum ELFEXT (PS-ELFEXT), propaga-

tion delay, length, delay skew, and wire map.

The second phase is to field certify the cabling

system for compliance with alien crosstalk (ANEXT)

requirements, which are the between-channel

parameters. This should include sample testing

of some links in a bundle to verify compliance.

Measuring ANEXT.

Typically in a laboratory, measuring power sum

alien near-end crosstalk (PS-ANEXT) and power-sum

alien far-end crosstalk (PS-AFEXT) is based on cables

in a “six-round-one” configuration. The central cable

is the victim cable, and all the adjacent cables are the

disturbers. This test configuration provides a worst

case scenario. A total of seven equal length links

are connected to each other at previously defined

distances. Every circuit is measured against the other

so there are 96 individual measurements.

At this point, it's not possible to test all wire-pair

combinations in the field for ANEXT. One strategy

is to use a sampling technique to select a limited

number of links for testing. The chosen links should

be those most likely to fail, such as the longest links,

or shorter links with the shortest distance between

connectors. Limit testing to links that are bundled

together.

Field testing fiber.

Compared to copper, fiber optic cable is relatively

simple to test. Basically, you shine a light down the

cable and measure how much arrives on the other

end. That’s attenuation, and it’s the performance

parameter used for fiber testing. Unfortunately,

attenuation can be affected by the installation,

but it’s easily tested in the field.

The typical fiber test link includes:

– Fiber cable (horizontal or backbone, depending

on application)

– Telecommunications outlet connector

– Consolidation points, if any

When testing fiber, each individual link segment

in both the horizontal and backbone runs must

be tested. Each segment is allowed a budget loss.

Then, the total link insertion loss is the sum of the

individual link segment losses.

The performance standards for fiber optic cable

are listed in the chart on page 12.

Fiber testers.

Don’t worry about trying to test your fiber

system yourself. Again, there are professional

technicians who know how to use advanced fiber test

equipment, which includes a power meter and a light

source. Very advanced equipment can test different

wavelengths, in both directions, eliminating a lot of

legwork for either you or a professional technician.

These testers, like their copper counterparts,

automatically calculate all test results and save

them for future downloading and documentation.

TECH TIP

In a six-around-one

configuration with a

disturbed, or victim,

cable, alien crosstalk

measures the crosstalk

induced in a wire pair

in the victim cable by

wire pairs in adjacent

cables. ANEXT can be

mitigated or eliminated

through the use of

S/FTP or F/UTP cable.

ANEXT

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