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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. - PowerPoint PPT Presentation
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Alien Crosstalk for the Inexperienced User
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Agenda
What is alien crosstalkWhere does alien crosstalk occur in
the linkStandards & guidelines defining alien
crosstalkCreating a quality plan to address
requirementsLink performance requirementsLink certification
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What is Alien Crosstalk
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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
ComponentAXT
ComponentAXT
CableAXT
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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
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Reflected Mode of Alien Crosstalk
Signal onDisturbing
LinkComponent AXT Cable AXT
Near end alien crosstalk is a reflected mode that is sourced and received at the same ends of the disturbing and disturbed links
Noise onDisturbed
Link
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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
Signal onDisturbing
Link
ComponentAXT
CableAXT
ComponentAXT
Noise onDisturbed
Link
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Where Does Alien Crosstalk Occur in the
Link
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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
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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
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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
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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
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Standards & Guidelines Defining Alien Crosstalk
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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
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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
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Creating a Quality Plan
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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
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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
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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
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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
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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
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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
# of Disturbing Links
Worst Case Instrument Test Time
1 1.5 minutes
2 3 minutes
4 6 minutes
8 12 minutes
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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
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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
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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
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Link Performance Requirements
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Performance 10GBASE-T Class E & Category 6
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
* Not a recognized Class E measurement ** Not a recognized Category 6 measurement
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Performance Class EA & Category 6A 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
* Not a recognized Class EA measurement ** Not a recognized Category 6A measurement
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Performance Class F
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
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Performance Class FA
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
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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
Signal onDisturbing
LinkComponent AXT Cable AXT
Noise onDisturbed
Link
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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
Signal onDisturbing
Link
ComponentAXT
CableAXT
ComponentAXT
Noise onDisturbed
Link
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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
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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
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Link Certification
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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
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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
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Typical PSANEXT Test Setup
Disturber Link
100 OhmTerminators
Patch Cord ConnectingSycronization Ports
USB Cord
Near End DeviceFar End Device
Disturbed (Victim) Link
PC RunningResult Manager
User Patch orCAT6A Test Cord
User Patch orCAT6A Test Cord
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Typical PSAACRF Test Setup
User Patch orCAT6A Test Cord
Disturber Link100 Ohm
Terminator
USB Cord
Near End Device Far End Device
100 OhmTerminator
Disturbed (Victim) Link
Patch Cords and 3rd Link ConnectingSynchronization Ports
PC RunningResult Manager
User Patch orCAT6A Test Cord
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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
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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
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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
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Thank you
