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CERTIFICATION
The third element of a LAN cabling system is the installation of cable and connectors in the field . This is what LAN cable certifiers test , and where the responsibility to check compliance with standards falls on the installer or engineer , rather than the manufacturers .
The cabling standard defines the performance of the completed links and channels when connectors and cable are installed in the field . Quality connectors and cable will provide their advertised performance when properly installed in laboratory environments , but installation in the field is very different from installation in a laboratory . In the field the cable can be stretched , kinked , crushed , installed in hot areas , exposed to water , and terminated with poor workmanship . Therefore , to ensure that the individual quality components form a completed , quality cabling system , installers need to test the performance of that cabling .
LAN cable
certification
By Dan Barrera , Global Product Manager , IDEAL Networks
www . idealnetworks . net
What does a LAN cable certifier test , and when should installers certify LAN cabling ?
LAN cable certifiers continue to evolve and advance as the demands on networks develop . But despite progressing technologies , the reasons to certify cabling remain the same and this is due to cabling standards .
Understanding the standards There are two main standardisation bodies that define the LAN cabling specifications . The ISO / IEC with the 11801 series of standards , and the ANSI / TIA with the 568 series , which define three types of performance requirements : components , cable and cabling .
Put simply , the first two elements of a LAN cabling system are the connectors and the cable . Component standards define the performance of jacks or outlets and plugs ( connectors ) for each performance category . Cable standards define the performance of the bare cable with no connectors attached . Manufacturers design and test their components and cables to these standards to ensure they meet the performance defined by ISO or TIA .
How it works To set up a certifier to test cabling , the installer must select the desired performance standard as well as the configuration of the cable being tested . The two options for certifying commercial cabling are channel and permanent link ( PL ). Channel tests consist of the installed cabling , the patch cords that connect the cabling to the networking equipment and the connector that mates to the patch panel and work area outlet . The connection at the channel adapter is not included in the test .
When testing a PL , the installed cabling is tested using special PL adapters on the certifier . The connection at the patch panel and work area is also tested . This is the most common test performed in the field because it tests the elements of the cabling that the installer is responsible for , not patch cords which the end-user of the network could change , thereby invalidating certification test results .
What does a certifier test ? The key measurements for certifier tests are return loss and crosstalk . This is what separates certifiers from other types of network cable testers .
Crosstalk Crosstalk is the measurement of a signal coupling from the intended pair of cable to another . It ’ s undesirable because it creates interference between the channels of the Ethernet transceiver at either end of the cable . The most common sources of excessive crosstalk are untwisting of the pairs during termination , poor quality connectors and cable or connectors that aren ’ t rated to the frequency at which they ’ re being tested .
Certifiers measure Near End Crosstalk ( NEXT ) for determining component quality in workmanship of the cable ; Far End Crosstalk ( FEXT ) which is used in calculations for other measurements and Powersum NEXT , that ’ s a calculated value to simulate the combined crosstalk of any three pairs on the fourth pair of the cable . A certifier can also measure Alien Crosstalk where signal from one cable coupled onto a different cable , instead of the signal coupled from one pair onto another in the same cable , is measured .
Return loss Return loss is the measurement of the signal reflected from the cabling back into the transmitting device – like an echo . High levels of return loss can create strong echoes that interfere with the transmission of the signal in one direction ,
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