Copper Cabling Troubleshooting Handbook
Contents
1. Fail fail or pas Resistance Test Res Likely ise of Result e Incorrect patch cord type F LLIJKE networks Advanced troubleshooting diagnostics The automated DTX Series diagnostics discussed above represent a distillation of a more complex analysis of the test results data In this section we discuss the lower level more detailed diagnostics information that the DTX Series testers generate This section is provided to enhance the understanding of the diagnostic analysis of link failures In many cases the automated diagnostics provide a clear description of the locations of defects or poor cable termination Knowledge of the advanced diagnostics techniques may be able to distinguish cases in which the automated diagnostics fall short The basis of the tester s ability to report the distance to a location along the link under test where crosstalk is excessive or where Return Loss is excessive is the conversion of the test results data collected in the frequency domai techniques The data in the ti to a profile of the meas at dist the linkt The two parameter are HDTDX High De HDTDR High Definiti name indicates the ome too big and cted exceeds the maximum The tester software further analyzes this information to generate the graphical results discussed earlier The user can view the HDTDR and HDTDX information Figure 8 shows the two diagnostic parameters on the tester s scre2. The unigue value of the DTX Series diagnostics come to the forefront in the testers ability to locate performance problems such as return loss or NEXT Figure 4 shows the test result screen of a failing Class E link Return Loss shows a marginal failure whereas Near End Crosstalk NEXT Power Sum NEXT PSNEXT Attenuation to Crosstalk Ratio ACR and Power Sum ACR PSACR show outright failures The numbers in parentheses on the right hand side of the screen show the worst case margin for the corresponding test parameter By pressing the FAULT INFO key the tester offers four diagnostic possibilities Figures 5a though 5d show these different possible scenarios for the failure The user should evaluate all of these possibilities inspect the cable for what is described and when a problem is confirmed perform the corrective action In figure 5a the tester entertains that the lin more than four connectors A first possibili after analyzing the test res contains four connecto diagnostic does not tester screen segment at 18 m fro defect that causes t either the wire the source of The message Verify the cable is the correct type Cable appears to be category 5 warns that the source of the failure could be that the 8 meter cord is a Cat 5 cable in a link in which all component should rate as Cat 6 in order to obtain Class E performance Note that this screen tells us that the second connector at the end of the patch
3. When the test technician locates this point along the physical link the defect indeed stands out The most expedient and typically best remedy for a failing patch cord is to obtain and install a good Cat 6 replacement cord At that time you should retest the link to ensure that all defects have been corrected and that the link passes The actual time to execute this repair should not exceed a few minutes depicted in figure in figure 5a is also 2 Pair Combos NEXT failure correct type Cable appears to be category 5 Verify installed cable is the p 3 Location 4 gt Failure 1 1 Figure 5d The last diagnostic suspects the cable between the two middle connections You learn in this text that the real cause of the link failures is the untwist of the wires at the end of the patch cord bleshooting techniques will show you how you and interpret the underlying diagnostic informa PPanel TO Main Unit Smart Remote L1 15 m Figure 6 The map of the permanent link under test The wire pairs of patch cord 1 are unt termination as indicated in the schematic diagram A r gt Figure 7 This photo sh clo of the wi ermination is the defect in the teste gt end of the 2 meter patch cord This NETWORKSUPER Causes of cabling faults For each of the required TIA and ISO structured cabling measurements you will find trou bleshoot
4. and Accessories Technical Documentation Support and Downloads Home Solutions Center Datacom Cabling Cabling Resources for Consultants and Designers Cabling Resources for Consultants and Designers Verifying Network A E ore i Service Availability Designing instaling and maintaining a reliable physical Application Note cable plant is essential to the well being of today s PRODUCTS mission critical LANs End user organizations builders DTX CableAnalyzer See how to verify and property owners and contractors hire you as a OptiFiber Certifying OTDR document the availability professional consultant to analyze design and LinkWare Stats of network services over a recommend telecommunications products and AnalyzeAir cabling link with the DTX services CableAnalyzer TECHNICAL PAPERS Your success depends on your ability to stay New How to test to TIA EIA 568 B 2 10 up to date with new standards performance Guide to choosing the Right Cable Test Tool requirements the latest technology and industry Updated 10Gigabit Ethernet White Paper information The Permanent Link in Field Certification Advanced OTDR Trace Analysis White Paper This Solution Center focuses on the latest trends and Ensuring the Health of your Fiber technologies available to design and test next Demystifyi Interference Problems in the RF generation cabling systems as well as relevant national Spectrum White Pap
5. cord is 17 m removed from the tester remote unit So which one of these automatically generated diagnostics is correct All Pairs Link failure Link may have more than the 4 i gt Failure 1 1 The diagnostics suspects he permanent link may many connections Pair 4 5 Return Loss failure is maintained at the jack and verify jack is the correct category rating 18m i verify wire twist PEA Location 4 gt Failure 1 1 Figure 5b Press the up or down arrows to move from one suspect location in the link to the next Move the right left arrow keys to read multiple diagnostics at a location This location at 18 m from the Smart remote only shows one defect that is expected to be the cause of the marginal return loss results for wire pair 4 5 The tester also posts the recommended inspections and corrections Figure 6 shows the configuration of the link we constructed 2 Pair Combos for this test NEXT failure Figure 7 shows a picture of the actual defect The wire 17m Verify wire twist pairs at the end of the 2 m patch cord are untwisted in ia the jack and an excessive manner and cause the NEXT failures at that connection as well as the marginal return loss problem for ele P pair 4 5 at that same location The diagnostics described above locate the defects at 18 m from the Smart remote unit for return loss and at 17 m for NEXT This is indeed an accurate diagnostic
6. margin is positive when the test passes negative when the measurement fails and zero when the measured value is equal to the limit value A greater margin indicates that the result is further away from the limit A larger positive margin therefore indicates a very good test result A very small margin means that the test result is close to the limit value A test result is marginal when its margin is smaller than the a specification for the test parameter For exa MHz is 0 4 dB That considered very clo diagnostics informa this marginal result right pins at either alts the test and displays the d asks the operator whether or not to e the test It often makes more sense to tackle the before continuing the test The open wire is infinite Any parameter based on a calculation with the insertion loss value is therefore invalid or undefined FAIL 18011801 PL max Class E 4 Insertion Loss 7 4 dB im XX Return Loss 0 2 dB X NEXT 5 9 dB X PSNEXT 4 2 dB X ACR 3 5 dB X PsACR 1 8 dB y ELFEXT 2 3 dB vf PSELFEXT 4 7 dB a Highlight item Y Press ENTER Figure 4 Upon completion of an Autotest the tester s screen shows the list of test parameters executed for the selected test standard Test parameters marked with the red X fail The tester also displays the worst case margin for each parameter in parentheses at the right edge of the screen F LLIJKE networks
7. over For the latest information on cable testing standards news and issues visit the Fluke Networks web site Partner with Fluke Networks Fluke Networks provides the most comprehensive line of premises network test solutions for the inspection verification certification and documentation of high speed copper and fiber cabling systems Advanced certification for premium network testing DTX Series CableAnalyzer has been the preferred tester by cable installers eo ea ee e e e E 04 24 2008 05 41 59pm and network owners worldwide They deliver laboratory accuracy and pro O mu Frequency MHz 469 0 Limit dB 247 Margin as 51 ductivity emote The DTX 1200 and DTX 1800 are the first platform cable test tools that combine in one unit twisted pair ANY cabling certification coaxial gt NERA testing fiber loss len 100 150 aa Gn 350 400 450 500 TIA TSB155 PL Cat 6 UTP are allows you to manage the test re a If you store the graphical data in the tester oad this data into LinkWare This allows the includes documenta LinkWare cable test any time in the future HDTDX and HDTDR data are part of the data stored in LinkWare if they have been gener ated as a result of the link failing This information can be useful if the technicians in the field need assistance with the ana
8. the horizontal axis around the main reflection located at 48 7 m Note that this location is physically the same one gt 1X gt 2X gt 2X gt 2X I m 67 6 Value 235 3 4 gt Cursor Figure 11 To further examine the HDTDX trace and determine what is happening between dif ferent wire pairs we view the traces by wire pair combina tion This screen shows the crosstalk along the link for the combination of the 1 2 and 4 5 wire pairs Two spikes are clearly visible the biggest one at 48 7 m The screen also shows the value of the reflec tion from this location as 253 3 a value that is clearly off the charts F LLIJKE networks as shown in figures 9 and 10 at 49 1 m The conversion from time to distance varies a little from pair to pair because the electrical signals travel at a slightly different speed on each wire pair Each wire pair in the cable is twisted at a different twist rate to improve the NEXT performance of the cable However this difference in twist rate changes both the length of the copper conductor as well as the speed of the signal The tester reports what is called the electrical length or distance which deviates somewhat form the physically length you would obtain with a tape measure along the link We can further analyze what is happening along the cable at the first huge NEXT spike at 48 7 m In the cursor mode of operation press the Set Mark ke
9. F LLJKE networks NETWORKSUPERVISION r 26 6 m Prop Delay v Delay Skew Insertion Logs Return Loss NEXT 15 9 dB 5 0 dB a Highlight item Press EXIT Copper Cabling Troubleshooting Handbook Table of Contents Introduction 2 Troubleshooting Basics Link Models The automated DIX Series diagnostics Causes of Cabling Faults Advanced Troubleshooting Diagnostics Conclusion networks Introduction Certification is the process of comparing the transmission performance of an installed cabling system to a standard using a standard defined method of measuring the performance Certification of the cabling system demonstrates component quality and installation workmanship It is typically a requate obtain the cabling manufacturer s warranty Certification demands that the abti links yield a Passing result Technicians must diagnose the failing links and aft not only include making the certification measurements butials and troubleshooting Why the need for advanced diagnostics Today s cabling installation professionals must therefore know diagnose high performance cabling systems Due to the prs sed and quick 1g al y U Borough th Fluke works DTX Serici petti value ing of advanced structured cabling systems using the aDkeAnalyzer so you can increase your productivity and deliver e to your organi mae on Troubleshoot
10. el requires that the test interface cable tool to the link under test are totally transparent to the measure sense this means that field certification test tools must be muc because they must subtract the test cord effects contributions fi measurement However the permanent link model includes the adapters and the jacks sockets of the link Plug ja inati iver widely varying test results for critical panne Loss To properly asses the performance ofsthe end jacks of the atch panel and e end of the permanent link test adapter shall be a 1 sitive test paramet delivers for all freguency sen nent specifications within a very narrow band of B ore do not vary much one from the other and deliver optimum Telecommunications Figure 1 Patch Panel Consolidation Telecommunications Point 1 1 Beginning of End of channel channel Figure 2 NETWORKSUPER The automated DTX Series diagnostics When an Autotest fails or delivers a marginal pass result the DTX Series testers automatically process the data to produce diagnostic information for the cabling link After the diagnostic process has been completed the user can press the FAULT INFO key soft key F1 to see the results of the diagnostic data processing of the test results First let us review what a marginal test is The margin of a test is the difference between the measured value and the applicable Pass Fail limit value The
11. en Highlight HDTDX and press ENTER to 1 The conversion from time to distance relies on the knowledge of the speed with which the electrical signals travel over the twisted pair copper cabling The cabling characteristic called NVP Nominal Velocity of Propagation expresses this speed with reference to a constant which is the speed of light in vacuum It is desirable that the tester knows the correct value of NVP for each cable type Working with the correct value of NVP allows the tester to report the distance to a cabling defect more precisely FAIL ISO11801 PL max Class E X NEXT 5 9 dB E X PSNEXT 4 2 dB X ACR 3 5 dB X PSACR 1 8 dB y ELFEXT y PSELFEXT HDTDR A a Highlight Y Press Ej gt 1X gt 1X 49 1 m Value 291 4 4 gt Cursor Figure 9 The HDTDX trace depicts the amount of crosstalk that is generated at each location along the link The horizontal axis is labeled in meters or feet not MHz The Main unit is always located at the left of the screen and the distances are measured from the Main unit The spike at 49 1 meters from the Main unit shows the location with an exceptionally high amount of crosstalk NETWORKSUPER see the screen depicted in Figure 9 This figure shows the magnitude of the NEXT coupling along the link for all six wire pair combinations First note that the horizontal axis runs from 0 6 m to 67 6 m or shows the length o
12. er and international telecommunications standards and Wireless Site Survey Best Practices White Paper provide a reference to the most commonly used Wireless Network Access and 802 1x Security White information Paper New How to cable 802 11n Wireless Access Points Fiber Network Installation and Certification Update ARTICLE REPRINTS Network cabling certification is the process of New Fiber Certification Provides a Complete Solution measuring network cabling performance parameters New Q amp A OTDR Traces Versus Loss Length Testing and comparing the results against industry or New OLTS and OTDR A Complete Testing Strategy user defined performance standards Certification recommendations such as TIA s TSB140 bulletin titled CUSTOMER CASE STUDIES Additional Guidelines for Field Testing Length Loss Fiber Testing Heats Up in the Southwest and Polarity of Optical Fiber Cabling Systems provides STATEMENT OF WORK guidelines on how to test fiber optic cabling systems in ANSI TIA EIA 568 B Cat Se Field Test Specifications the field offering two tiers of fiber network certification ANSI TIA EIA 568 B Cat 6 Field Test Specifications Fiber TIA EIA Field Test Specification CENELEC EN50173 Fiber Installation Requirement ISO IEC 11801 Fiber Installation Test Requireme Residential Cabling S O W Specification Basic or Tier 1 fiber certification is required in all fiber optic cabling links The Tier 1 tests are attenuation insertion loss lengt
13. f the cabling link under test The link starts at 0 m and runs through 67 m The very ends 0 6 m of the trace show the permanent link adapters which do not belong to the tested permanent link This is the same link we discussed earlier and that is depicted in figure 6 The curves show the magnitude of the NEXT coupling at each point along the link When you inspect the curves from left to right it is immediately clear that the NEXT coupling is relatively low until we arrive at 49 1 m A huge spike in the NEXT curves indicates that the coupling at this point is excessive and the probable cause of the link NEXT test failure The cursor is automatically positioned at this spike tester reports the distance at which the cursor 1 Use the Zoom The tester initially the vertical scale sho 100 0 to 100 0 both axes to zoom in on F2 labeled It facilitates XT profile curve is magnified more detailed inspection of The symbol cursor or zoom appears in the e the zoom along the vertical or horizontal scales or ove the cursor position left or right along the The screen in figure 10 remains very busy because it shows the NEXT profile for all wire pair combinations For further analysis you may elect to show the data for each pair combination press F3 labeled Plot by Pair to view each pair combination Figure 11 shows the NEXT profile for the 1 2 4 5 pair combination while at the same time we have zoomed in on
14. gation delay e Cable uses different insulation materials on different pairs Delay skew Insertion Loss Attenuation Test Result Possible Cause of Result Exceeds limits e Excessive length e Non twisted or poor quality patch cables e High impedence connections Use time domain techniques to trouble e Inappropriate cable category e g Cat 3 in a Ca e Incorrect autotest selected for cabling unde NEXT and PSNEXT Test Result Possible Cause of Result Fail fail or pass e Poor twisting at connection Unexpected pass NETWORKSUPER Return Loss Test Result Possible Cause of Result Fail fail or pass e Patch cord impedence not 100 ohms e Patch cord mishandling causes changes in impedence e Installation practices untwists or kinks of cable the original twists should be maintained as much as possible for each wire pair e Excessive amount of cable jammed into the Telecom O tl e Bad connector e Cable impedance not uniform e Cable not 100 ohm e Impedance mismatch at junction between patch cable and horizontal cable e Poorly matched plug and jack e Use of 120 ohm cable e Service loops in telecommunications clo e Inappropriate autotest selected e Defective link adapter Unexpected pass e Fails at low freque Due to the 3 dB rule ACR F and PS ACR F older names EL and PSELFEXT Test Result Likely Cause of Result
15. h and polarity When conducting Tier 1 testing each fiber link is measured for attenuation and results are documented This test TRIAL ARE ensures that the fiber link exhibits less loss than the New ir Trial Software maximum allowable loss budget for the immediate ayia Solara application Extended or Tier 2 fiber certification supplements testing with the addition of an Optical Time Doi Reflectometer OTDR trace of each fiber li OTDR trace is a graphical signature of a fit attenuation along its length You can gain i performance of the link components cab and splices and the quality of the installati examining non uniformities in the trace An does not replace the need for insertion loss measurement but ic weed for comnlementans Nin Calutinn Figure 16 Consult the F s web page for pro nformation as well as updates in standards or white papers on best practices GC vw flukenetworks com design inally passing results In order to deliver a high quality cabling at cause the failures and marginal passes must be uncovered and correct an anomaly an installation error or a defective component Personnel responsible for the networks operation can also benefit from the diagnostic capabilities of a certification test tool with the tester s assistance they can limit the duration of network downtime and restore service quickly Familiarize yourself with the capabilities of your test tool A modest investment that pays for itself many times
16. ing Basics Most common causes of failures in twisted pair cabling 1 4 5 Connectors that do not meet the required transmission quality Incorrect tester set up Installation errors Proper connections while maintaining the wire pairs and the twist rate in each pair always keep the original twist in each wire pair as much as practical Defects or damage in the installed cable Bad patch cords an automated test or an autotest The tes determine the link model Permanent Link measured the frequency range over wha criteria for each test Has the correct li Are you using telecommunica Steady state operating temperature before setting a reference or executing easurements This may take 10 to 15 minutes or more depending on the tempera ture differential Link models To obtain meaningful results it is essential to select the appropriate autotest and link model The permanent link performance is defined in such a way that after adding good patch cords to a passing link the channel performance is automatically met By good patch cords we mean patch cords that pass the same class or category rating as the link or a higher level of performance For this reason it is recommended that new cabling installation are certified permanent link model and test standard Patch cords and equipment cords ma many times during the life of the permanent link The permanent link test mod
17. ing tips to help quickly pinpoint the cause of failures when they occur In some instances you will find suggested reasons why the measurement does not fail in cases you would expect to see a failure Wiremap Test Result Possible Cause of Result e Wires brocken by stress at connections e Cables routed to wrong connection e Wire is not punched down properly and does the IDC e Damaged connector e Cuts or breaks in cable e Wires connected to wrong pins at conec e Application specific cable e g Ethernet Open e Improper connector termi e Damaged Connector e Conductive material Align reversed pair g pins at connectororpunch block Split pair Length Short Wy Wires connected ong pins at connector or punch block Test Resu Possible Cause of Result mediate break in the cable length Une or more pa e Damage to cable ificantly shorter e Bad connection Note Jractices dictate that the cabling length be defined by the length of the shortest pair NVP varies per pai ing each pair could be reported with a different length These two conditions can result in a cable with T of four pairs over the length limit yet the link result is a Pass e g a channel with 101 99 103 102 meters for the four pairs A Pass in this case is the correct interpretation F LLJKE networ KS Delay Skew Test Result Possible Cause of Result Exceeds limits e Cable is too long Propa
18. lysis of the cabling defects endorse the ke Networks DTX Series CableAnalyzer testers and the LinkWare
19. s are much more sensitive to small reflection values To show a more detailed analysis 2 o ike EX we have increased the zoom for the vertical axis of the same trace to 8X in figure 14 Figure 15 shows the HDTDR trace for wire pair 4 5 We have moved the cursor to the left to show the sharp peak more clearly in the trace at the location of the untwisted wire pairs This picture clearly shows how the HDTRDR trace allows us to identify a location with a Significant return loss problem Upon closer inspection of figure 14 we can also determine that the shorter 15 m link segment L2 in figure 6 to the right of the defective patch cord shows significantly more return loss for several wire pairs than the higher quality cabling segment to the left L1 A KA oat 1X 8X 0 0 12 5 l m 0 6 677 40 9 m Value 0 4 4 gt Cursor Figure 15 This figure shows the reflection for pair 4 5 only To show the spike in the reflec tions more clearly we moved the cursor a bit to the left The more significant points of reflection toward the ends show the location of the connectors The cable segment L2 on the right shows significant reflec tions in the cable itself F LLJKE networks Where to Buy News and Events Training and Workshops Knowledge Base AboutUs Contact Us United States Change location language MyAccount Sign In Create an Account E gt NETWORK VISION Advanced Search Home Products
20. y F1 with the cursor in position at 48 7 m and move the cursor to the left and align it with the second big spike The result showndi figure 12 tells us that this second spike is loca 50 8 m and that the distance between the m cursor is 2 1 m The two bigger spike location of the co patch cord in the Spikes are shown 1 conclude that the 2 problem This concl conclusion we had reache generated le and the remedy may be icated since the cable itself may have to shows the magnitude of reflections The total energy of reflections results in the Return Loss measurement Figure 13 shows the full scale HDTDR plot for the channel we have been analyzing in this booklet Without zooming in the HDTDR trace shows few reflections except at the initial location of the cursor at 47 7 m where the measured reflection is 17 3 The values for HDTDR will generally be gt 2X 2X Ormation to link map shown in figure can see that the HDTDX tified the two con the one with the untwisted wire pairs causes a huge amount of crosstalk A us 1Xx 1X 0 0 400 1 jm 0 47 7 m Value 17 3 4 gt Cursor Figure 13 The HDTDR trace shows the signal reflection on each wire pair Locations show ing an excessive amount of reflected energy are the cause of return loss failures The HDTDR traces typically show fewer and smaller reflections than the HDTDX traces smaller but the link test result
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