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Alien Crosstalk for the Inexperienced User

Alien Crosstalk for the Inexperienced User. Agenda. What is alien crosstalk Where does alien crosstalk occur in the link Standards & guidelines defining alien crosstalk Creating a quality plan to address requirements Link performance requirements Link certification.

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Alien Crosstalk for the Inexperienced User

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  1. Alien Crosstalk for the Inexperienced User

  2. Agenda • What is alien crosstalk • Where does alien crosstalk occur in the link • Standards & guidelines defining alien crosstalk • Creating a quality plan to address requirements • Link performance requirements • Link certification

  3. What is Alien Crosstalk

  4. What is Alien Crosstalk • Alien crosstalk (AXT) is a unwanted disturbing signal coupling from one balanced twisted-pair component, channel or permanent link to another • The term “Alien” is used because unlike pair to pair crosstalk, alien crosstalk is a disturbing noise source that originates from outside the affected link’s cable and components

  5. History - Alien Crosstalk • In 2006 the IEEE ratified 10GBASE-T and later published IEEE 802.3-2008 defining a version of Ethernet with a nominal data rate of 10 Gbit/s, ten times faster than Gigabit Ethernet • Achieving 10GBASE-T over copper required new encoding schemes, 500MHz bandwidth and full duplex transmission • Due to these changes alien crosstalk, which has always been present in twisted pair copper networks and cannot currently be cancelled, became a significant noise source capable of disrupting 10GBASE-T • In response the industry defined new standards and guidelines for acceptable levels of alien crosstalk and developed test methods for measuring alien crosstalk

  6. Reflected Mode of Alien Crosstalk • Near end alien crosstalk is a reflected mode that is sourced and received at the same ends of the disturbing and disturbed links

  7. Transmitted Mode of Alien Crosstalk • Far end alien crosstalk is a transmitted mode that is sourced and received at opposite ends of the disturbing and disturbed links

  8. Where Does Alien Crosstalk Occur in the Link

  9. Where Does Alien Crosstalk Occur • Alien crosstalk occurs between the cables and components of a disturber link and a disturbed (victim) link • Alien crosstalk coupling increases as the components and cables of the two links approach each other • Alien crosstalk is extremely dependent upon installation practices such as patch cord positioning, cable bundling, use of tie-wraps, pathway fills and component placement • Alien crosstalk is not simply limited to a single disturbing link, multiple disturbing links may add to the total alien crosstalk present on a disturbed link

  10. Alien Crosstalk in the Horizontal Link • Alien crosstalk occurs when different cables run in parallel for an extended distance in close proximity • Long, tightly bound cable bundles present an ideal location for significant levels of alien crosstalk • A worst case condition exists when a disturbed (victim) cable is surround by six disturbing cables

  11. Alien Crosstalk in Cords • Alien crosstalk occurs when different equipment and patch cords are routed together in close proximity • Bound cords present an ideal location for significant levels of alien crosstalk in the first few metres of the link • Management bar lay and waterfalls also present opportunity for alien crosstalk

  12. Alien Crosstalk in Components • Alien crosstalk occurs where components of different links come into close proximity • Patch panels present an ideal location for significant levels of alien crosstalk • A worst case condition exists when a disturbed port is surrounded on three or four sides by disturber ports

  13. Standards & Guidelines Defining Alien Crosstalk

  14. Standards Defining Alien Crosstalk • ISO/IEC 11801 Ed 2.0 Amendment 1 provides channel and alien crosstalk requirements for Class EA, Class F and Class FA • BS EN 50173-1 A1 provides channel and alien crosstalk requirements for Class EA, Class F and Class FA • ANSI/TIA-568-C.2 provides channel, permanent link and alien crosstalk requirements for Category 6A

  15. Guidelines Defining Alien Crosstalk • Guidelines provide methods for re-characterizing installed Class E and Category 6 cabling to ensure 10GBASE-T operation • ISO/IEC TR 24750 and CLC/TR 50173-99-1:2007 both provide channel and alien crosstalk recommendations for installed Class E • TIA TSB-155 provides channel, permanent link and alien crosstalk recommendations for installed Category 6 • Class E and Category 6 cabling is not recommended for new installations supporting 10GBASE-T operation

  16. Creating a Quality Plan

  17. Cable Considerations • UTP Class EA and Category 6A cables with improved alien crosstalk performance may be constructed with an inner seperator, a larger outside wall thikness and an increased cable diameter. • Cable alien crosstalk performance can be compromised by deforming the outer jacket or inner separator due to tie wraps, excessive conduit/pathway fill or exceeding recommended bend radius • Pathway and conduit fill ratios increase for the same number of cables if the cable diameter increases

  18. Cord and Component Considerations • UTP Class EA and Category 6A equipment and patch cords typically have a larger outside wall thickness to reduce alien crosstalk • Cord alien crosstalk performance can be compromised by deforming the outer jacket due to tie wraps and exceeding recommended bend radius • Compacting cords in management bars and trays brings cords into closer proximity increasing alien crosstalk in the critical first few meters of the link • UTP Class EA and Category 6A patch panels are typically lower density than Class E and Category 6

  19. Reducing Alien Crosstalk • Minimize the number of cables in a bundle, reducing the number of possible disturbers • Un-bundle the horizontal link in the first 15 metres allowing the cables to separate • Eliminate cable ties if possible, if not reduce cable tie tension and space cable ties farther apart • Randomly lay cable in trays to prevent any two cables from running in close proximity their entire length • Use F/UTP or S/FTP cables and cords to significantly reduces alien crosstalk

  20. Reducing Alien Crosstalk (cont) • Separate equipment and patch cords and eliminate cable ties to reduces the alien crosstalk coupling in the first few metres of the link • Lay cords randomly in management bars to prevent any two cords from running in close proximity their entire length • Reduce the number of cords in a waterfall and maximize the radius to reduce cord compaction • Use fully shielded components to significantly reduce alien crosstalk

  21. Alien Crosstalk Consideration • Alien crosstalk is extremely dependent upon installation practices such as patch cord positioning, cable bundling, use of tie-wraps, pathway fills and component placement • Alien crosstalk certification is unique, its a selective process using statistical data about the installation to identify and certify the links deemed most prone to alien crosstalk interference • Certifying alien crosstalk on each Class EA/F/FA and Category 6A link or re-certifying alien crosstalk on each Class E or Category 6 link may not be necessary nor plausible due to test times

  22. Alien Crosstalk Consideration (cont) • Alien crosstalk testing consumes significantly more time than channel or link testing • Worst case instrument test time for a single disturbed link testing PSANEXT and PSAACRF at both ends of the link

  23. Additional Guidance • Seek guidance from cable and component manufacturers for installing and certifying Class EA/F/FA or Category 6A links • Seek additional guidance from cable and component manufacturers for identifying and selecting disturbed and disturbing links for alien crosstalk certification • Consult ISO/IEC TR 24750, CLC/TR 50173-99-1:2007 or TIA TSB-155 for determining the Class E or Category 6 alien crosstalk environment and alien crosstalk mitigation techniques

  24. Create a Quality Plan • Create a quality plan that considers how the selection and installation of cable and components affects the alien crosstalk environment • The quality plan should identify changes to the installation brought on by Class EA/F/FA or Category 6A components • The quality plan should address alien crosstalk certification, including identification & selection of test links and criteria for obtaining satisfactory performance • A Class E and Category 6 quality plan should address alien crosstalk mitigation practices • Obtain agreement from all parties

  25. Create a Quality Plan (cont) • A good quality plan that considers and incorporates the elements in the previous slides will reduce installation and certification time while increasing confidence in installation’s ability to meet alien crosstalk requirements

  26. Link Performance Requirements

  27. Pair measurements Wiremap Delay/Delay Skew/Length* Resistance** Pair to pair performance extended to 500MHz Insertion Loss Return Loss NEXT & PSNEXT ACR-N & PSACR-N** ACR-F & PSACR-F Alien crosstalk added 1-500MHz PSANEXT Average PSANEXT PSAACRF Average PSAACRF Marginal Computation Performance 10GBASE-T Class E & Category 6 * Not a recognized Class E measurement ** Not a recognized Category 6 measurement

  28. Pair measurements Wiremap Delay/Delay Skew/Length* Resistance** Pair to pair performance 1-500MHz Insertion Loss Return Loss NEXT & PSNEXT ACR-N & PSACR-N** ACR-F & PSACR-F Alien crosstalk 1-500MHz PSANEXT Average PSANEXT PSAACRF Average PSAACRF Performance Class EA & Category 6A * Not a recognized Class EA measurement ** Not a recognized Category 6A measurement

  29. Pair measurements Wiremap Delay/Delay Skew Resistance Pair to pair performance 1-600MHz Insertion Loss Return Loss NEXT & PSNEXT ACR-N & PSACR-N ACR-F & PSACR-F Alien crosstalk added 1-600MHz PSANEXT Average PSANEXT PSAACRF Average PSAACRF Performance Class F

  30. Pair measurements Wiremap Delay/Delay Skew Resistance Pair to pair performance 1-1000MHz Insertion Loss Return Loss NEXT & PSNEXT ACR-N & PSACR-N ACR-F & PSACR-F Alien crosstalk 1-1000MHz PSANEXT Average PSANEXT PSAACRF Average PSAACRF Performance Class FA

  31. Power Sum Alien NEXT (PSANEXT) • PSANEXT sums four near end alien crosstalk measurements from each pair of the disturbing link to a single pair of the disturbed link • Four PSANEXT results are calculated at the end of a disturbed link for a total of 8 results if both ends are tested

  32. Power Sum Alien ACRF (PSAACRF) • PSAACRF sums four far end alien crosstalk measurements from each pair of the disturbing link to a single pair of the disturbed link • Four PSACRF results are calculated at the end of a disturbed link for a total of 8 results if both ends are tested

  33. Average PSANEXT & PSAACRF • Average PSANEXT is the average of the PSANEXT results on each of the disturbed link pairs • Average PSAACRF is the average of the PSAACRF results on each of the disturbed link pairs • One Average PSANEXT or PSAACRF result is calculated at the end of a disturbed link for a total of 2 results if both ends are tested

  34. Alien Crosstalk Margin Computation • The alien crosstalk margin computation is used if the PSANEXT or the PSAACRF limits are not met on Class E or Category 6 links • The alien crosstalk margin computation ensures that the total combined PSAFEXT and PSANEXT that couples into a channel is limited in order to maintain the 10GBASE-T minimum signal to noise ratio • The alien crosstalk margin calculation is a sufficient qualification for suitability of Class E or Category 6 channels to support 10GBASE-T operation

  35. Link Certification

  36. Certifying Class EA/F/FA & Category 6A • Certify the channel or link performance of every link saving the Autotest result and graphical data • Using the test plan criteria and result data, identify the disturbed links deemed most prone to alien crosstalk interference and their associated disturbing links • Per the test plan criteria, select from the identified links those disturbed and disturbing links that require alien crosstalk certification • Certify the alien crosstalk of the selected disturbed links per the test plan

  37. Re-certifying Class E & Category 6 • Re-certify the channel or link performance of every link designated to support 10BASE-T saving the Autotest result and graphical data • Using the test plan criteria and result data, identify the disturbed links deemed most prone to alien crosstalk interference and their associated disturbing links • Re-test the channel or link performance of all identified disturbing links saving the Autotest result and graphical data* • Certify the alien crosstalk of the selected disturbed links per the test plan *Links designated only as a disturber do not have to pass channel or link certification

  38. Typical PSANEXT Test Setup

  39. Typical PSAACRF Test Setup

  40. Alien Crosstalk Testing • Testing is conducted from the PC result manager alien crosstalk (AXT) application • The AXT application provides the tools needed to certify alien crosstalk • The AXT application displays alien crosstalk certification results and link statistics in real time

  41. Conclusion • Alien crosstalk is a unwanted disturbing signal coupling from one balanced twisted-pair component, channel or permanent link to another • Alien crosstalk is extremely dependent upon installation practices and occurs where links come into close proximity such as in cable bundles and patch panels • ISO/IEC 11801 Ed 2.0 Amendment 1 and BS EN 50173-1 A1 provide channel and alien crosstalk performance requirements for Class EA/F/FA links • ANSI/TIA-568-C.2 provides channel or link and alien crosstalk performance requirements for Category 6A links

  42. Conclusion (cont) • ISO/IEC TR 24750 & CLC/TR 50173-99-1:2007 provide guidance for supporting 10GBASE-T on Class E channels • TIA TSB-155 provides guidance for supporting 10GBASE-T on Category 6 channels and links • Create a quality plan addressing the unique requirements for installation, certification and alien crosstalk mitigation prior to starting • A good quality plan will reduce installation and certification time while increasing confidence in installation’s ability to meet alien crosstalk requirements

  43. Thank you

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