Guide to Network Cabling
Fundamentals
Chapter 8
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Chapter 8 - Testing and Troubleshooting
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Understand the necessity for testing your cable
system
Define and perform tests on copper and fiber
Understand troubleshooting methods and general
techniques
Identify and use testing and troubleshooting tools
Design a disaster avoidance plan
Manage your documentation
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Testing Your Cabling System
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After the cabling is in place, a final critical step
remains in the installation: testing the system
Three types of cable testing exist:
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Operational testing ensures that a system is working
properly and includes these procedures: checking all
cables for continuity; performing polarity tests of cable
pairs; running a connectivity test; testing for cable shorts
and opens
Performance testing is designed to ensure that a system
complies with all applicable codes and standards
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Testing Your Cabling System
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Three types of cable testing (cont.):
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Acceptance testing is designed to demonstrate
functionality, prove conformity to specifications, and
ensure performance based on customer’s measurement
criteria, called parameters
Acceptance testing serves to satisfy the contract with the
customer and these requirements: the types of cable to
use for each portion of the installation; the acceptable
means for running the cable; various types of termination
equipment; the performance expected from each type of
cable; complete documentation of the installation and test
results
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Testing Copper and Fiber Media
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Test copper UTP cable in accordance with the TIA
TSB-67 standard, which specifies methods,
parameters, and minimum requirements for testing
installed Category 3, 4, and 5 cabling
There are several benefits of testing and certifying
according to TSB-67:
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Verifying that no faults occurred during the installation,
and ensure that the system will perform according to the
user’s requirements
Protecting the installer from blame if a problem occurs
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Testing Copper and Fiber Media
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TSB-67 defines two types of tests for UTP:
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The basic link is the permanent part of a cable run that
includes 90 meters of horizontal cable, the
telecommunications outlet, and the first punch-down in
the telecommunications room
The channel encompasses the basic link plus all patch
cords and equipment cords
These tests should both be performed; they are important
in verifying proper workmanship, and they provide a future
reference for the system’s proper state of operation or
performance (or baseline)
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Testing Copper and Fiber Media
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TSB-67 tests for copper UTP cable:
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The wire map test identifies wiring errors (opens and
shorts, crossed-pair, reversed-pair, split-pair), and checks
connectivity
The length test verifies that cable length is within the
specifications for maximum allowable length
The attenuation test measure a cable’s signal loss from
end to end; all cable pairs must be tested
The near-end crosstalk (NEXT) test measures the signal
coupling from one pair of wires to another pair within the
same cable
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Testing Copper and Fiber Media
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Proposed new tests for copper UTP cable are
known as TSB-95:
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Propagation delay measures the time, in nano-seconds
(nS), it takes a signal to travel a cable
Attenuation-to-crosstalk ratio (ACR) is the difference
between the NEXT and attenuation measurements
The power sum measurement compares the crosstalk
effects on all pairs in a cable
Return loss is a measurement of the signal that echoes or
reflects back into the transmitter
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Testing Copper and Fiber Media
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General testing rules for copper UTP cable:
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Do not move any cable or equipment during testing
Record pass/fail indications and always record the actual
measured values and the date
If any part of the system is reconfigured, retest it
Always perform the NEXT test and record the
measurements from both ends of the cable
When performing channel tests, always test with the enduser cords and patch cords in place
If a cable barely passes a test, record this marginal result
in the report of actual test measurements
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Testing Copper and Fiber Media
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Test fiber-optic cable to demonstrate that any
exhibited loss does not exceed the acceptable
limits defined by ANSI/EIA/TIA-568-B.3
Testing ensures that the cabling system:
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Meets the customer’s attenuation specifications
Provides documentation of baseline readings, which are
an essential gauge for future troubleshooting
When testing, test the power levels on the
transmitter and receiver to ensure proper operation
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Testing Copper and Fiber Media
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Attenuation testing of fiber is crucial after
installation because interruptions in the cable
(splices and connections) provide more
opportunities for signal loss
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During attenuation testing, measure cables in both
directions and at both available wavelengths
A wavelength is the measure of the color of light,
expressed in nanometers (nm)
Spare fibers or unterminated fibers do not require
attenuation testing, but the do need to be tested for
continuity
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Testing Copper and Fiber Media
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Attenuation testing must be done on every link
segment of cable
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Link segments consist of cable, connectors, other
connections, and splices between two fiber-optic
termination units in the system
The three basic link segment types are horizontal,
backbone, and composite
To compute the acceptable attenuation value for any link
segment, use this equation:
acceptable link attenuation = cable attenuation +
connector attenuation + splice attenuation
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Testing Copper and Fiber Media
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Optical connectors, adapters, and cable
assemblies must comply with the requirements of
ANSI/EIA/TIA-604-3-1997, FOCIS 3; also test the
system in accordance with TIA FOTP
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Follow these procedures before testing begins: read the
equipment manufacturer’s testing instructions; ensure that
all connectors, jumpers and adapters are properly
cleaned; ensure that the light source or optical domain
reflectometer (OTDR) operates within the range of
850±30 nm for multimode cable and
1300 ±20 nm for single-mode cable
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Testing Copper and Fiber Media
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The steps for testing end-to-end attenuation:
1. Take a reference reading by connecting a test jumper
from the power meter to the optical source
2. Take a check reading by connecting a second jumper to
the first with an interconnection sleeve
3. Subtract the reference from the check reading
4. If attenuation is acceptable, proceed, otherwise, clean
connectors and return to step 2
5. Take an official attenuation test reading by performing an
end-to-end attenuation test
6. Determine end-to-end attenuation by subtracting the
reference from the official attenuation test reading
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Troubleshooting Methods and
General Techniques
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Successful troubleshooters must be logical,
methodical, and good at problem solving
Perform the following troubleshooting steps:
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Identify the symptoms
Verify user competency
Identify the scope of the problem
Recreate the problem
Verify the physical integrity of all connections
Determine if due to recent system changes
Determine, implement, and test the solution
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Tools for Testing and Troubleshooting
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In many cases, it is more efficient to use a tool
that can analyze and isolate system problems
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Tools for testing copper cable include: multimeters test
shorts, opens, continuity verifications, attenuation
measurements, and electrical outlets; continuity testers
test for proper wiring mapping, opens, shorts, bad
terminations and reversed-pairs; certified field testers
test all parameters required by TSB-67 and TSB-95;
time domain reflectometer (TDR) tests for line
impedance, attenuation, opens, shorts, NEXT, cable
distances, and connector or terminator problems
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Tools for Testing and Troubleshooting
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Tools (cont.):
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Tools for testing fiber-optic cable include: power meters
and optical light sources, which measure a cable’s signal
strength and attenuation, and the light source can also
determine leakage at connectors and bends; optical time
domain reflectometers (OTDRs) measure a cable’s
length and signal strength; jumpers connect the power
meter and the light source; interconnection adapters are
circuit administration points that provide access to a
circuit and mates connectors
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Disaster Avoidance
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A disaster is an event that prevents a business
from performing its critical functions
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Disaster avoidance, or disaster prevention, is a series of
measures designed to prevent, detect, or contain
potentially calamitous incidents
The first priority is to prevent disasters, but since this is
impossible, the next priority is to develop procedures
that minimize a disaster’s impact
Proper planning can greatly reduce the trauma of
rebuilding and repairing systems after a disaster, and it
can help ensure the rebuilding is successful
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Disaster Avoidance
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Disaster planning:
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To ensure disaster avoidance plan soundness, increase
the amount of installed cables in the system, select the
proper equipment, and think through as many “what if”
scenarios as possible
One of the best and easiest disaster avoidance methods
is redundancy, which is built into a system by adding
duplicate parts at any or all points
Another method involves adding diversity to the system,
using both fiber and copper to ensure that service
continues through the copper if fiber is disabled
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Disaster Avoidance
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Disaster planning (cont.):
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Redundancy and diversity can be planned in backbone
cables by running more than one and installing them
along different paths
Other aspects of network planning and installation are
also critical to disaster avoidance, including: grounding,
firestopping, and physical connectivity
Create redundancy for important network data and
applications by mirroring part of the network to another
building, city, or state
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Managing Your Documentation
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Managing test results
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Test results are a critical part of the documentation
Use the following guidelines to manage test results from
cable testers: document the standards used for testing;
ensure the latest software version for the cable tester
and record that too; select a labeling scheme (cable ID)
that matches the label on the patch panel or outlet;
select the format and media to use for test results
Most newer cable testers come with the ability to
download test results - do this every day
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Managing Your Documentation
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Data Management Equipment
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An important part of effective management is selecting
the right tools for the job
Consider the following equipment: label printers range
from simple models that require manual keypad input to
models that connect to test tools and print labels after
each test is performed; software solutions such as
spreadsheets and databases help manage test results,
and mapping software to provide a logical view of the
network
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Chapter Summary
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Test your cable installation before activating the service to
guarantee that the system is working properly. Testing
also ensures that all installed components meet the
customer’s performance specifications, as well as codes
and standards
Operational testing includes continuity testing, verification
of polarity, and connectivity testing to ensure that there are
no shorts or opens. Performance testing ensures that the
system complies with all applicable codes and standards.
Acceptance testing is designed to prove conformity to
specifications and ensure performance based on the
customer’s measurement criteria
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Chapter Summary
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Always test UTP cable systems in accordance
with the TIA TSB-67 standard, which specifies
methods and parameters for testing installed
Category 3, 4, and 5 cabling with a hand-help
instrument. This standard also defines basic link
and channel test configurations for UTP cable.
TSB-67 tests that are currently required for
Category 5 certification include wire map tests,
length tests, attenuation tests, NEXT (near-end
crosstalk) tests, and propagation delay tests
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Chapter Summary
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You must test fiber-optic cable for attenuation to comply
with current standards. You should also test for
attenuation on all link segments, connectors, adapters,
and cable assemblies
Even if you only perform new installations, you still need to
know how to troubleshoot your system. A successful
troubleshooter is logical, methodical, and good at problem
solving. Troubleshooting steps include identifying
symptoms, identifying the scope of a problem, and
recreating the problem
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Chapter Summary
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Many of the tools you use for everyday
installation and maintenance are the same ones
you use to test cables or troubleshoot problems
Disaster avoidance is designed to ensure the
continuous availability of critical business
services in case of disaster. Although you cannot
prevent all disasters, you can minimize their
effects by planning redundancy and diversity into
telecommunications systems
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Chapter Summary
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The documentation manual provides important information
about your network. This information can assist you in
troubleshooting network problems, and it provides an
accurate hardware and software inventory
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