Transcript Finish Phase

Finish Phase Overview
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Testing
Troubleshooting
Certification
Documentation
© 2002, Cisco Systems, Inc. All rights reserved.
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Finish Phase
• Steps
• Testing
• Troubleshooting
• Certification
• Documentation
• Testing
• Testing verifies that all wires are working so that
the customer does not find that there are problems
later
• Testing is for functionality, that is, it determines if
the wire can carry the signal from end to end
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Finish Phase
• Common Test Errors
Phases of testing
• Wire-mapping errors – Wires in a
multi-pair cable do not terminate at
the appropriate contacts in the
connector at the far end
• Opens – Wires in cables fail to make
a continuous path from end to end.
This is usually due to improper
termination or breakage.
Occasionally it is due to faulty cable
• Shorts – Wires in cables touch each
other, thus shorting the circuit
• Split pairs – Wires are mixed among
pairs
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Finish Phase - Common Test Errors
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Finish Phase
• Common Testers
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tone generators
cable and jack testers
telephone test sets
multimeters
TDR and OTDR
• Two methods of testing
• Channel Test
• Link Test
• Channel Test
• The channel test goes truly end-to-end from the
workstation or telephone to the device in the TR
• The channel test includes the line cord from the jack to the
user equipment
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Finish Phase
• Channel Test
• Goes from workstation/phone to the TR device
• The channel test includes the patch cord from the patch
panel to the communications equipment
• Officially eliminated by TIA/EIA-568-B.1
• Link Test
• Tests cable from the wall back to the patch panel
• There are two types: basic and permanent
• Only permanent link test is acceptable per TIA/EIA568-B.1
• Permanent Link Test
• Excludes the cable portions of the adapters, but
includes the mated connection at each end
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Finish Phase
• Permanent Link Test
• Allows for a consolidation point, which is
desirable for open office cabling installations and is
therefore more practical
• The problems that should be tested for are foreign
voltage, shorts, reversals, split pairs, and crosstalk
• Testing for Foreign Voltage
• A voltage that does not belong on the wire
• Sources of foreign voltage can be dangerous
• Cross-connects, insulation failures, static electricity
• Inductive currents formed by routing signal wires too
close to wires carrying large voltages
• Multimeters can test for foreign voltage.
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Finish Phase
• Testing for Shorts
• A short is formed when the two wires in a pair touch
each other
• Tests to determine if there is a short measure the
continuity or resistance between the wires
• Make these measurements with an ohmmeter using a
low-resistance scale
• Testing for Reversals
• A cable tester is needed
to determine reversals
• A reversal occurs when the tip (or
ring) side of a pair is terminated on
the ring (or tip) position at the
opposite end of the wire
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Finish Phase
• Testing for Split Pairs
• Split pairs happen when wires are mixed
• Test for splits with an ohmmeter & tone generator
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Finish Phase
• Testing for Crosstalk
• Crosstalk occurs when the signal from a
transmitting pair is coupled to the receiving pair or
other pairs in the cable
• Cable testers are used to detect crosstalk
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Finish Phase
• Fiber-optic
Testing
• Fiber-optic cables
are tested using a
calibrated light
source and an
optical power meter
to measure the loss
in the cable being
tested
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Finish Phase
• Testing Grounding Systems
• Grounding systems tests are generally performed
using a special purpose instrument - a megger
• Megger checks performance of grounding and bonding
• The NEC states that if the grounding systems
resistance to ground is 25 ohms or greater
• The installer has to add a second ground rod
• Reading of 5 ohms or less is considered
commercially acceptable
• Troubleshooting Copper Connections
• Hard faults
• Problems that make communication virtually impossible
• Are relatively easy to identify and clear
• Opens, split pairs, and shorts are examples of hard faults
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Finish Phase
• Troubleshooting Copper Connections
• Intermittent faults
• Come and go and cause problems such as:
• Dropped packets
• Packets with errors
• Often, these problems are caused by crosstalk
• Troubleshooting Fiber-optics
• Most problems are found with the connectors
• Fiber connector end faces can become scratched:
• With repeated connecting and disconnecting
•Dirt and dust on the end faces of the connectors
can also add attenuation that will impede a fiberoptic signal
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Finish Phase
• Certification
• The certification process forms a baseline
measurement for the cabling system
• It allows the installer to say unequivocally that at a
certain day and time the cables performed
• Any later change in cable performance must be attributable
to some cause
• it will be easier to troubleshoot
• Minimum Test Results
• To pass, cables must meet the minimum grade test results
• The difference between the actual test results and the
minimum test results is known as headroom.
• If the results show lots of headroom
• There should be less cable maintenance needed in the future
• More tolerant of poor grade patch cords and equipment cables
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Finish Phase
• Certification
• Testing is for functionality, that is, it determines if
the wire can carry the signal from end to end.
Certification, or performance testing, is a statement
about cable performance
• Performance test systems usually use a receiver
on the far end that communicates over the wire to
the main test unit.
• Category 5e cable is tested at 100 MHz and
Category 6 at 250 MHz.
• Performance testing per TIA/EIA-568-B
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Finish Phase - Certification Testing
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Finish Phase
• Common Test Specifications
• Specified Frequency Range
• Attenuation
• Near End Crosstalk (NEXT)
• Return Loss
• Propagation Delay
• Delay Skew
• Documentation
• After the cabling has been tested and certified,
documentation is created
• These are called as-built documents
• As-builts show the client and future technicians exactly the
layout of the cable installation.
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Finish Phase
• Documentation
•These are called as-built documents
• It may vary from the original plans since obstacles or
problems may have occurred during installation
• Diagrams showing the cable runs, locations of outlets, and
identity of each outlet should be created and presented to
the client
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