The Specification of Field Test Requirements
for a Balanced Twisted-Pair Cabling System
Cat 6 Installation: field test requirements upon completion
of the installation
A. General Requirements1.
Every cabling link in the installation shall be tested in
accordance with the field test specifications defined in the
most recent draft of the "Transmission Performance Specifications
for 4-pair 100 ohm Category 6 Cabling" under development
by the Telecommunications Industry Association (TIA). At the
time of this writing, PN-3727 TIA/EIA Draft Standard - Draft
7, dated August 23, 2000 represents the most recent version.
This document will be referred to as the "TIA Cat 6 Draft
Standard."
2. The installed twisted-pair horizontal links shall
be tested from the IDF in the telecommunications room to the
telecommunication wall outlet in the work area against the
"Permanent Link " performance limits specification
as defined in the TIA Cat 6 Draft Standard.
3. 100% of the installed cabling links must be tested
and must pass the requirements of the standards mentioned
in I.A.2 above and as further detailed in Section I.B. Any
failing link must be diagnosed and corrected. The corrective
action shall be followed with a new test to prove that the
corrected link meets the performance requirements. The final
and passing result of the tests for all links shall be provided
in the test results documentation in accordance with Section
I.C below.
4. Trained technicians who have successfully attended
an appropriate training program and have obtained a certificate
as proof thereof shall execute the tests. Appropriate training
programs include but are not limited to installation certification
programs provided by BICSI or the ACP (Association of Cabling
Professionals).
5. The test equipment (tester) shall comply with the
accuracy requirements for the proposed level III field testers
as defined in the TIA Cat 6 Draft Document. The tester including
the appropriate interface adapter must meet the specified
accuracy requirements. The accuracy requirements for the permanent
link test configuration (baseline accuracy plus adapter contribution)
are specified in Table B.2 of Annex B of the TIA Cat 6 Draft
Standard. (Table B.3 in this TIA document specifies the accuracy
requirements for the Channel configuration.)
6. The tester shall be within the calibration period
recommended by the vendor in order to achieve the vendor-specified
measurement accuracy.
7. The tester interface adapters must be of high quality
and the cable shall not show any twisting or kinking resulting
from coiling and storing of the tester interface adapters.
In order to deliver optimum accuracy, preference is given
to a permanent link interface adapter for the tester that
can be calibrated to extend the reference plane of the Return
Loss measurement to the permanent link interface. The contractor
shall provide proof that the interface has been calibrated
within the period recommended by the vendor. To ensure that
normal handling on the job does not cause measurable Return
Loss change, the adapter cord cable shall not be of twisted-pair
construction.
8. The Pass or Fail condition for the link-under-test
is determined by the results of the required individual tests
(detailed in Section I.B). Any Fail or Fail* result yields
a Fail for the link-under-test. In order to achieve an overall
Pass condition, the results for each individual test parameter
must Pass or Pass*.
9. A Pass or Fail result for each parameter is determined
by comparing the measured values with the specified test limits
for that parameter. The test result of a parameter shall be
marked with an asterisk(*) when the result is closer to the
test limit than the accuracy of the field tester. The field
tester manufacturer must provide documentation as an aid to
interpret results marked with asterisks.
10. A representative of the end-user shall be invited
to witness field testing. The representative shall be notified
of the start date of the testing phase 5 business days before
testing commences.
11. A representative of the end-user will select a
random sample of 5% of the installed links. The representative
(or his authorized delegate) shall test these randomly selected
links and the results are to be stored in accordance with
the prescriptions in Section I.C. The results obtained shall
be compared to the data provided by the installation contractor.
If more than 2% of the sample results differ in terms of the
pass/fail determination, the installation contractor under
supervision of the end-user representative shall repeat 100%
testing and the cost shall be borne by the installation contractor.
B. Performance Test Parameters
The test parameters for Cat 6 are defined in TIA Cat 6 Draft
standard, which refers to the TIA/EIA-568-B.2 standard. The
test of each link shall contain all of the following parameters
as detailed below. In order to pass the test all measurements
(at each frequency in the range from 1 MHz through 250 MHz)
must meet or exceed the limit value determined in the above-mentioned
draft standard.
[Optional Requirement - can only be combined with option
(a) in Section I.C.6.] Each parameter shall be measured
from 1 through 350 MHz and all of these measurement points
are to recorded in the test results information as detailed
in Section I.C.6.
1. Wire Map Wire Map shall report Pass if the wiring
of each wire-pair from end to end is determined to be correct.The
Wire Map results shall include the continuity of the shield
connection if present.
2. Length The field tester shall be capable of measuring
length of all pairs of a basic link or channel based on the
propagation delay measurement and the average value for NVP
(1). The physical length of the link shall be calculated using
the pair with the shortest electrical delay. This length figure
shall be reported and shall be used for making the Pass/Fail
decision. The Pass/Fail criteria are based on the maximum
length allowed for the Permanent Link configuration (90 meters
- 295 feet) plus 10% to allow for the variation and uncertainty
of NVP.
3. Insertion Loss (Attenuation) Insertion Loss is a
measure of signal loss in the permanent link or channel. The
term "Attenuation" has been used to designate "Insertion
Loss." Insertion Loss shall be tested from 1 MHz through
250 MHz in maximum step size of 1 MHz. It is preferred to
measure insertion loss at the same frequency intervals as
NEXT Loss in order to provide a more accurate calculation
of the Attenuation-to-Crosstalk ratio (ACR) parameter.
Minimum test results documentation (summary results): Identify
the worst wire pair (1 of 4 possible). The test results for
the worst wire pair must show the highest attenuation value
measured (worst case), the frequency at which this worst case
value occurs, and the test limit value at this frequency
4. NEXT Loss Pair-to-pair near-end crosstalk loss (abbreviated
as NEXT Loss) shall be tested for each wire pair combination
from each end of the link (a total of 12 pair combinations).
This parameter is to be measured from 1 through 250 MHz. NEXT
Loss measures the crosstalk disturbance on a wire pair at
the end from which the disturbance signal is transmitted (near-end)
on the disturbing pair. The maximum step size for NEXT Loss
measurements shall not exceed the maximum step size defined
in the draft standard as shown in Table 1, column 2.
Minimum test results documentation (summary results): Identify
the wire pair combination that exhibits the worst case NEXT
margin (2) and the wire pair combination that exhibits the
worst value of NEXT(worst case). NEXT is to be measured from
each end of the link-under-test. These wire pair combinations
must be identified for the tests performed from each end.
Each reported case shall include the frequency at which it
occurs as well as the test limit value at this frequency.
1 Nominal Velocity of Propagation (NVP) expresses the speed
of the electrical signals along the cabling link in relation
to the speed of light in vacuum (3x108 m/second). Insulation
characteristics and twist rate of the wire pair influence
NVP in minor ways. Typically, an 'average' value for NVP is
published for all four wire-pairs in a data cable.
2 'Margin' designates the difference between the measured
value and the corresponding test limit value. For passing
links, 'worst case margin' identifies the smallest margin
over the entire frequency range; the point at which the measured
performance is "closest" to the test limit.
TABLE 1
| Frequency Range(MHz) |
Maximum Stepsize (MHz) |
| 1 - 31.25 |
0.15 |
| 31.26 - 100 |
0.25 |
| 100 - 250 |
0.50 |
| 250 - 350 |
- |
5. PSNEXT Loss Power Sum NEXT Loss shall be evaluated
and reported for each wire pair from both ends of the linkunder-test
(a total of 8 results). PSNEXT Loss captures the combined near-end
crosstalk effect (statistical) on a wire pair when all other
pairs actively transmit signals. Like NEXT this test parameter
must be evaluated from 1 through 250 MHz and the step size may
not exceed the maximum step size defined in the draft standard
as shown in Table 1, column 2.
Minimum test results documentation (summary results): Identify
the wire pair that exhibits the worst case margin and the wire
pair that exhibits the worst value for PSNEXT. These wire pairs
must be identified for the tests performed from each end. Each
reported case shall include the frequency at which it occurs
as well as the test limit value at this frequency.
6. ELFEXT Loss, pair-to-pair Pair-to-pair FEXT Loss shall
be measured for each wire-pair combination from both ends of
the linkunder-test. FEXT Loss measures the crosstalk disturbance
on a wire pair at the opposite end (far-end) from which the
transmitter emits the disturbing signal on the disturbing pair.
FEXT is measured to compute ELFEXT Loss that must be evaluated
and reported in the test results. ELFEXT measures the relative
strength of the far-end crosstalk disturbance relative to the
attenuated signal that arrives at the end of the link. This
test yields 24 wire pair combinations. ELFEXT is to be measured
from 1 through 250 MHz and the maximum step size for FEXT Loss
measurements shall not exceed the maximum step size defined
in the draft standard as in Table 1, column 2.
Minimum test results documentation (summary results): Identify
the wire pair combination that exhibits the worst case margin
and the wire pair combination that exhibits the worst value
for ELFEXT. These wire pairs must be identified for the tests
performed from each end. Each reported case shall include the
frequency at which it occurs as well as the test limit value
at this frequency.
7. PSELFEXT Loss Power Sum ELFEXT is a calculated parameter
that combines the effect of the FEXT disturbance from three
wire pairs on the fourth one. This test yields 8 wire-pair combinations.
Each wire-pair is evaluated from 1 through 250 MHz in frequency
increments that do not exceed the maximum step size defined
in the draft standard as shown in Table 1, column 2.
Minimum test results documentation (summary results): Identify
the wire pair that exhibits the worst case margin and the wire
pair that exhibits the worst value for PSELFEXT. These wire
pairs must be identified for the tests performed from each end.
Each reported case shall include the frequency at which it occurs
as well as the test limit value at this frequency
8. Return Loss Return Loss (RL) measures the total energy
reflected on each wire pair. Return Loss is to be measured from
both ends of the link-under-test for each wire pair. This parameter
is also to be measured form 1 through 250 MHz in frequency increments
that do not exceed the maximum step size defined in the draft
standard as shown in Table 1, column 2.
Minimum test results documentation (summary results): Identify
the wire pair that exhibits the worst case margin and the wire
pair that exhibits the worst value for Return Loss. These wire
pairs must be identified for the tests performed from each end.
Each reported case shall include the frequency at which it occurs
as well as the test limit value at this frequency.
9. ACR (Attenuation to crosstalk ratio) [This parameter
is not demanded by the draft standard but may be required in
order to obtain the premise wiring manufacturer's warranty]
ACR provides an indication of bandwidth for the two wire-pair
network applications. ACR is a computed parameter that is analogous
to ELFEXT and expresses the signal to noise ratio for a two
wire-pair system. This calculation yields 12 combinations -
six from each end of the link.
Minimum test results documentation (summary results): Identify
the wire pair combination that exhibits the worst case margin
and the wire pair combination that exhibits the worst value
for ACR. These wire pair combinations must be identified for
the tests performed from each end. Each reported case shall
include the frequency at which it occurs as well as the test
limit value at this frequency.
10. PSACR [This parameter is not required by the draft
standard but may be required in order to obtain the premise
wiring vendor's warranty]
The Power Sum version of ACR is based on PSNEXT and takes into
account the combined NEXT disturbance of all adjacent wire pairs
on each individual pair. This calculation yields 8 combinations
-one for each wire pair from both ends of the link.
Minimum test results documentation (summary results): Identify
the wire pair that exhibits the worst case margin and the wire
pair that exhibits the worst value for PSACR. These wire pairs
must be identified for the tests performed from each end. Each
reported case shall include the frequency at which it occurs
as well as the test limit value at this frequency.
11. Propagation Delay Propagation delay is the time required
for the signal to travel from one of the link to the other.
This measurement is to be performed for each of the four wire
pairs.
Minimum test results documentation (summary results): Identify
the wire pair with the worst case propagation delay. The report
shall include the propagation delay value measured as well as
the test limit value.
12. Delay Skew [as defined in TIA/EIA-568-B.1; Section
11.2.4.11] This parameter shows the difference in propagation
delay between the four wire pairs. The pair with the shortest
propagation delay is the reference pair with a delay skew value
of zero.
Minimum test results documentation (summary results): Identify
the wire pair with the worst case propagation delay (the longest
propagation delay). The report shall include the delay skew
value measured as well as the test limit value.
C. Test Result Documentation1.
The test results information for each link shall be recorded
in the memory of the field tester upon completion of the test.
2. The test results records saved by the tester shall
be transferred into a Windows?-based database utility that
allows for the maintenance, inspection and archiving of these
test records. A guarantee must be made that the measurement
results are transferred to the PC unaltered, i.e., "as
saved in the tester" at the end of each test and that
these results cannot be modified at a later time. Superior
protection in this regard is offered by testers that transfer
the numeric measurement data from the tester to the PC in
a non-printable format.
3. The database for the completed job shall be stored
and delivered on CD-ROM including the software tools required
to view, inspect, and print any selection of test reports.
4. A paper copy of the test results shall be provided
that lists all the links that have been tested with the following
summary information
a) The identification of the
link in accordance with the naming
convention
defined in the overall system documentation
b) The overall Pass/Fail evaluation
of the link-under-test including
the NEXT
Headroom (overall worst case) number
c) The date and time the test
results were saved in the memory of
the tester
5. General Information to be provided in the electronic
data base with the test results information for each link:
a) The identification of the
customer site as specified by the end-
user
b) The identification of the
link in accordance with the naming
convention
defined in the overall system documentation
c) The overall Pass/Fail evaluation
of the link-under-test
d) The name of the standard
selected to execute the stored test
results
e) The cable type and the value
of NVP used for length
calculations
f) The date and time the test
results were saved in the memory of
the tester
g) The brand name, model and
serial number of the tester
h) The identification of the
tester interface
i) The revision of the tester
software and the revision of the test
standards
database in the tester
j) The test results information
must contain information on each of
the required
test parameters that are listed in Section I.B and as
further detailed
below under paragraph I.C.6.
6. The detailed test results data to be provided in
the electronic database for each tested link must contain
the following information (only one of these two formats must
be specified):
a) For each of the frequency-dependent
test parameters, the value
measured at
every frequency during the test is stored. In this
case, the
PC-resident database program must be able to
process the
stored results to display and print a color graph of
the measured
parameters. The PC-resident software must also
provide a
summary numeric format in which some critical
information
is provided numerically as defined by the summary
results (minimum
numeric test results documentation) as
outlined above
for each of the test parameters.
b) For each of the frequency-dependent
test parameters, the
minimum test
results documentation shall be stored for each
wire-pair
or wire-pair combination as observed from each end of
the link.
Length: Identify the wire-pair with the shortest electrical
length, the value of the length rounded to the nearest 0.5
m [optional: foot] and the test limit value
Propagation delay: Identify the pair with the shortest
propagation delay, the value measured in nanoseconds (ns)
and the test limit value
Delay Skew: Identify the pair with the largest value
for delay skew, the value calculated in nanoseconds (ns) and
the test limit value
Attenuation: Minimum test results documentation as
explained in Section I.B for the worst pair
Return Loss: Minimum test results documentation as explained
in Section I.B for the worst pair as measured from each end
of the link
NEXT, ELFEXT, ACR: Minimum test results documentation
as explained in Section I.B for the worst pair combination
as measured from each end of the link
PSNEXT, PSELFEXT, and PSACR: Minimum test results documentation
as explained in Section I.B for the worst pair as measured
from each end of the link
The minimum test results documentation for each test parameter
shall be in compliance with the information in Section I.B.
Link length, propagation delay, and delay skew shall be reported
for each wire pair as well as the test limit for each of these
parameters.
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