111 © 2002, Cisco Systems, Inc. All rights reserved. Finish Phase Overview Testing Troubleshooting Certification Documentation

111© 2002, Cisco Systems, Inc. All rights reserved.

Finish Phase Overview

• Testing• Troubleshooting• Certification• Documentation


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


Finish Phase

• Common Test Errors • 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

Phases of testing


Finish Phase - Common Test Errors


Finish Phase

• Common Testers• 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


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/EIA-568-B.1

• Permanent Link Test• Excludes the cable portions of the adapters, but includes the mated connection at each end


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.


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


Finish Phase

• Testing for Split Pairs• Split pairs happen when wires are mixed• Test for splits with an ohmmeter & tone generator


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


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


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


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 fiber-optic signal


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


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


Finish Phase - Certification Testing


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.


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

Documents

111 © 2002, Cisco Systems, Inc. All rights reserved. Finish Phase Overview Testing Troubleshooting Certification Documentation