| Eliminating alien crosstalk - June 09 |
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Page 2 of 2 Field testing Alien crosstalk testing involves testing various combinations of links that are identified as ‘victims’ and ‘disturbers’. Performing a test on a single victim cable involves at least six different testing configurations, and as many as 12—depending on the manufacturer of the field test equipment. Given that multiple tests are required for each victim link, requiring 100% testing of every link as a victim is not practical. During testing, when the first three victim/disturber combinations reveal a condition known as ‘insignificant alien crosstalk’, the test can be stopped without finishing the 1% or minimum five victim links. Insignificant alien crosstalk is a condition where the measurement is below a certain level and may not be detectable by some field test instruments. The selection of disturber links has to be done individually for every victim link. Select all links that run in the same cable bundle or are most consistently positioned relative to the victim cable. These bundles may be found in the patch panel, crossconnect or conduit. Add any additional links that occupy adjacent positions in the patch panel or outlet. When selecting links to test, the routing of links should also be considered in addition to the location of the links in the patch panel. The disturber links should be run in the same pathway as the victim link to have the most impact on alien crosstalk measurements. The proper selection of links for alien crosstalk testing is critical and requires a certain degree of knowledge about the topology of the cabling plant. Without knowing where the various links are routed to within the building, the process of testing can be inaccurate, since the chosen disturber links may not be close enough to the victim to provide any significant data. After deciding on the victim and disturber links to check, the field tester needs to be connected to the cabling according to the manufacturer’s directions. Some field testers require a personal computer to be attached to the field tester during the measurement process to gather the data and compute the alien crosstalk results. Additionally, the tester and computer may need to be moved to the opposite side of the link for the second half of the alien crosstalk testing process. Because the number of links to test and the time to test each victim/disturber combination can be significant, choosing the right field tester can save time and trouble. A field tester that does not require a computer for data acquisition or double-testing of each victim/disturber combination can cut 75% of the total alien crosstalk testing time while eliminating the need to bring a computer into the field. Dan Payerle is business unit manager with Ideal Industries Inc., and has been actively involved in the LAN cabling business, providing network design, testing, troubleshooting, consulting and training services for a variety of companies over the last decade. Working with several national training companies, Dan developed training programs for copper and fiber optic installation courses, and created curricula for trade schools to use in the process of becoming nationally accredited. CLICK HERE for Ideal Industries Inc |
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