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Cim 20071001 oct_2007

  1. 1. Contents Zoom In Zoom Out For navigation instructions please click here Search Issue Next Page Solutions for Premises and Campus Communication Systems Worldwide October 2007 www.cablinginstall.com _____________________ UTP cabling performance up close The not so intimidating OTDR Contents Zoom In Zoom Out For navigation instructions please click here Search Issue Next Page
  2. 2. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F Exceptional optical performance comes naturally. Nothing is more treasured in field termination than exceptional optical performance. The secret to UniCam® Pretium™- Performance Connectors is inside – a laser-cleaved, factory-polished fiber stub that ensures outstanding connectivity in a no-epoxy/no-polish (NENP) connector. UniCam Pretium-Performance Multimode Connectors offer 0.1 dB insertion loss. And UniCam Pretium-Performance Single-Mode Connectors enable 0.2 dB insertion loss. That’s exceptional optical performance in less than a minute per fiber, from the most widely deployed NENP connector on the market. Naturally ... Customer-focused innovation is second nature at Corning. www.corning.com/cablesystems/cimls © 2007 Corning Cable Systems LLC / LS-02413 C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F
  3. 3. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F ICC’s delivery! Competitor’s delivery. ALL NEW 10 Gig Fiber Optic Jumpers! Polarization-Maintaining alignment...better than 0.1° Lowest Insertion Loss of 0.2dB 10Gig laser optimized 100% individually tested Meets ANSI/UL 1666-1997 standards MPO, LC, and SC styles Save 40% or more... The difference? Excellent customer service, Toll Free: 888.ASK.4.ICC E-mail: csr@icc.com technical support, and product delivery! Web: www.icc.com PremiumProducts • ProvenPerformance • CompetitivePrices...ICC © Copyright 2007, ICC. ICC and ICC logo are registered trade name and trademark. All rights reserved. 1007 C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  4. 4. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F Our U.S. delivery area. No matter where you’re located, our fiber optic cable products are there. Optical Cable Corporation has built a network of reliable stocking distributors and a dedicated sales team committed to getting you the best fiber optic cables for your requirements when you need them...where you need them. For over 20 years, we have been manufacturing the broadest range of top-performing tight-buffered fiber optic cables for most applications in the government, military, and commercial markets. Your order is our top priority. Contact Optical Cable Corporation for a stocking distributor nearest you. We are where you are. 1-800-622-7711 5290 Concourse Drive • Roanoke, Virginia 24019 Phone 540-265-0690 • www.occfiber.com C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F
  5. 5. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F COVER CONCEPT BY DAN RODD OCTOBER 2007 VOL. 15, NO. 10 ABOUT THE COVER Used primarily in long- haul OSP applications, features 9 fusion splicing is now an alternative to field A close examination of terminations in the data UTP cabling performance center due to its effectiveness Answers to many of the”why” questions associated in meeting critical density with the installation and maintenance of unshielded and performance demands. TO LEARN MORE, twisted-pair systems. JAMES ANDRESS SEE PAGE 27. 21 Using an OTDR: How to keep it simple Not just for use in public networks, the optical time- domain reflectometer no longer has to be an intimidating tool. CHRISTIAN SCHILLAB 27 The ins and outs of fusion splicing Still primarily for use in the outside plant, the technology is now seeing deployment in premises applications. BETSY ZIOBRON 35 Enclosures play a role in thermal management Dealing with heat close to its source takes several forms. PATRICK MCLAUGHLIN 39 Surveillance market seeing many IP rumblings Acquisitions, alliances, and increasing attention are more evidence of the shift to Internet Protocol-based systems. PATRICK MCLAUGHLIN departments 6 Editorial 45 INDUSTRY SPOTLIGHT ■ Berk-Tek unveils smaller diameter LEED by example 51 New Products fiber cable for data centers 58 Product Focus: ■ A pioneering 40-Gbit optical active cable PATCH PANELS ■ Hybrid connector solution developed for harsh environments ■ Structured cabling system aimed at home, small office markets CABLING INSTALLATION & MAINTENANCE (ISSN 1073-3108), a trademark, is published 12 times a year, monthly, by PennWell Corporation, 1421 South Sheridan Road, Tulsa, OK 74112; telephone (918) 835-3161; fax (918) 831-9497; Web address www.pennwell.com. Editorial offices: 98 Spit Brook Road, Nashua, NH 03062-5737; telephone (603) 891-0123. © 2007 CABLING INSTALLATION & MAINTENANCE. All rights reserved. Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by CABLING INSTALLATION & MAINTENANCE (ISSN 1073-3108), provided that the appropriate fee is paid directly to Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923 USA; (978) 750-8400. Prior to photocopying items for educational classroom use, please contact Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923 USA; (978) 750-8400. For further information, check CCC Online at the following address: http://www.copyright.com/. All rights reserved. No material may be reprinted. Bulk reprints can be ordered from Diane Troyer, telephone (603) 891-9135. Corporate officers: Frank T. Lauinger, Chairman; Robert F. Biolchini, President and CEO. POSTMASTER: Send address changes to: CABLING INSTALLATION & MAINTENANCE, Circulation Dept., P.O. Box 3280, Northbrook, Il 60065-3280. Return undeliverable Canadian Addresses to: P.O. Box 1632, Windsor, ON N9A 7C9. Periodicals postage paid at Tulsa, OK 74101 and other additional offices. Subscriptions: In the U.S.: one year $74; Canada/Int’l surface : one year $84; International via air: one year $100. If available, back issues can be purchased for $16 in the U.S. and $21 elsewhere. We make portions of our subscriber list available to carefully screened companies that offer products and services that may be important for your work. If you do not want to receive those offers and/or information, please let us know by contacting us at List Services, CABLING INSTALLATION & MAINTENANCE, 98 Spit Brook Road, Nashua, NH 03062-5737-“Canada return address: PO Box 122, Niagara Falls, ON L2E 6S4”. www.cablinginstall.com ______________ Cabling Installation & Maintenance ■ October 2007 ■ 3 C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F
  6. 6. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F Chief Editor / Patrick McLaughlin (603) 891-9222 • patrick@pennwell.com Executive Editor / Steve Smith LEED by example (603) 891-9139 • stevesm@pennwell.com Senior Editor / Matt Vincent (603) 891-9262 • mattv@pennwell.com At the most recent BICSI Conference, tions, it would be in their best inter- Circulation Manager / Michelle Blake held the second week of September in est to acquire the ability to bid on and (603) 891-9360 • michellb@pennwell.com Las Vegas, I enjoyed the presentation carry out LEED-based contracts. Art Director / Kelli Mylchreest delivered by Bill Weekes, a Registered Even so, I couldn’t shake the irony Lead Illustrator / Dan Rodd Communications Distribution Design- of my own actions immediately fol- er with Fancom Network Integrators lowing that presentation. I got out of Senior Vice President/Group Publishing Director Mark Finkelstein (www.fancomni.com). He provided my chair, grabbed my empty water (603) 891-9133 • mark@pennwell.com firsthand, practical information on a bottle, and looked for something I Associate Publisher/National Sales Manager topic that might knew I wouldn’t find—a recycle bin. Ed Murphy (603) 891-9260 • edm@pennwell.com not be extremely So, I threw the bottle in the trash bar- familiar to many rel, on top of paper products and alu- CABLING INSTALLATION & MAINTENANCE in the cabling in- minum cans that also occupied it. EXECUTIVE AND EDITORIAL OFFICES dustry—the Unit- A few years ago, at a different con- PennWell ATD 98 Spit Brook Road ed States Green ference in Las Vegas, I wanted to Nashua, NH 03062-5737 Tel: (603) 891-0123, fax: (603) 891-9245 Building Council’s deposit my empty aluminum can Internet: www.cablinginstall.com Leadership in En- into a recycle bin, so I asked a ergy and Environ- member of the convention center’s SUBSCRIPTION INQUIRIES: For subscriptions or to change your format to print mental Design (LEED) program. maintenance staff where I could find or digital, please go to: www.cim-subscribe.com. Weekes was not familiar with one. Based on the look she gave me, I Subscriptions outside the USA are available in digital format only. LEED when he first got involved in initially believed she did not under- it, as he freely admitted during his stand English. In fact, she spoke the presentation. In fact, if I remember language fluently as far as I could his story correctly, he was commit- tell; it was the notion of a recycle bin CORPORATE OFFICERS ted to carrying out a certain project that put such a perplexed look on her Chairman / Frank T. Lauinger before learning it would be LEED- face. That’s when I realized the city’s certified, so had to take a crash course punchline of a motto was true on sev- President and Chief Executive Officer Robert F. Biolchini in the topic to go along with on-the- eral levels, and in this case could be Chief Financial Officer / Mark C. Wilmoth job training. That’s where much of the changed to, “What happens here, gets value in his BICSI presentation comes landfilled here.” ADVANCED TECHNOLOGY DIVISION from. Here was an RCDD speaking Expecting a place known as Sin Senior Executive Assistant Carol Woodward to other RCDDs about what it’s really City to provide a positive example of Tel: (603) 891-9112, fax: (603) 891-9287 going to mean to them when they get environmental stewardship is unre- carolw@pennwell.com involved in a project that is gunning alistic. But, as Weekes’ presentation VP Audience Development / Gloria S. Adams for LEED certification. pointed out, when those controlling It doesn’t matter where a project’s the purse strings are thinking envi- ATD PUBLISHING SERVICES DEPARTMENTS tradespeople stand on the sociopo- ronmentally, the dynamic changes. Art Director / Meg Fuschetti litical spectrum when it comes to I’ll be interested to hear more about Production Director / Mari Rodriguez (603) 891-9193 • marir@pennwell.com environmental causes; if the project our industry’s take on LEED. is aiming for LEED certification, and Marketing Communication Manager Kristen Jones these trades want to be paid, they’ll (603) 891-9425 • kristenj@pennwell.com comply with the building owner’s Ad Traffic Manager / Jackie Linker demands for enviro-friendly materi- (918) 832-9314 • jackiel@pennwell.com als, processes, and systems. So, while PATRICK McLAUGHLIN Mc some who saw Weekes present last Chief Editor PRINTED IN THE USA GST NO. 126813153 month might scoff at LEED’s inten- patrick@pennwell.com Publications Mail Agreement Number 40052420 4 ■ October 2007 ■ Cabling Installation & Maintenance www.cablinginstall.com C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  7. 7. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F THE PRESENTATION. THE SIGN-OFF. THE LAST HURDLE TO THE FINAL APPROVAL OF WHAT YOU BELIEVED WAS ALREADY OVER. There comes a moment in every project when each decision you’ve made is put to the test. Success and failure hang in the balance, as closing one deal takes longer than pitching the next. At moments like these, your most crucial decision was actually one of your first: your distributor. If it’s Graybar, you’re not on your own. Our nationwide supply chain, local support network and trusted suppliers stand ready for any ‘moment of truth’ you encounter. So keep pushing forward; we’ll be right there. FOR MORE INFORMATION, VISIT GRAYBAR.COM/CORNING OR CALL 1-800-GRAYBAR (472-9227). ___________ C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F
  8. 8. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F Turn your cable tester into an OTDR N E T W O R K S U P E R V I S I O N C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F
  9. 9. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F and watch the transformation begin. See how the DTX Compact OTDR Module can turn your cable tester into an OTDR and your staff into fiber experts – to completely transform your fiber business. Imagine. A cable tester that becomes a compact, easy-to-use, full-featured OTDR. Better yet, imagine what that means for your business. A single tool to test copper and fiber. An OTDR your current tech- nicians can easily use. Fiber jobs you couldn’t do before. Just snap the DTX Compact OTDR module onto a DTX mainframe – the industry’s benchmark for cable certification – now you’re ready to test like a fiber expert. Perform Basic (Tier 1) and Extended (Tier 2) fiber certification. Perform powerful single-ended troubleshooting. Deliver professional documentation. Win jobs that require OTDR testing and watch your revenue and profits increase. Get the new DTX Compact OTDR and watch the transformation begin. Go to www.flukenetworks.com/seehow to enter to win a DTX Compact OTDR and see a live demo. ©2007 Fluke Corporation. All rights reserved. 02177 C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  10. 10. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F Mohawk’s pre-terminated fiber optic Plug’n Play solutions combine ease of installation with the flexibility to work with any corresponding fiber cassette. Whether long runs or short runs, Mohawk’s Plug’n Play fiber solutions complement data center performance with its compact cable size and maximum flexibility. Features and Benefits: • Pre-terminated cables for premium performance. • Small diameter and bend radius for installation in high density environments. • The MPO terminations allow the cables to plug into any corresponding fiber cassette. • Compliant to TIA-568-C.3. MOHAWK For more information or a copy of our Application Note visit www.mohawk-cable or call 800-422-9961. Cabling Excellence for Open Architecture C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F
  11. 11. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F www.cablinginstall.com design A close examination of UTP cabling performance M ost of us are fa- miliar with the installation specifications that have been Answers to many of the “why” questions associated with the installation and maintenance of UTP systems. written for unshielded twisted-pair (UTP) cabling sys- Any information that is transmitted involves the use tems. These specifications include such topics as pair of frequencies or bits, even including 60-hertz alternat- untwist, bend radius, and pulling tension. And while ing current (AC) power. Information includes voice, mu- we are familiar with these standard requirements, sic, radio, data, video, television, or even light, as in fiber many—especially those new to the trade—may wonder optics. The more information we have to transmit, the why such handling restrictions exist. What happens if the specifications are not followed Hertz vs. bits exactly? And why are the specifications more critical, and 4 Hz 4 bits/sec more restrictive, when transmitting higher data rates? The key point of this entire article is: installation 1 second 1 second quality and correctness. They are vital, and they are entirely up to you. Let’s fi rst consider that the twisted pair was de- signed several decades ago to transmit a voice signal at 4,000 Hz. Over the past 15 to 20 years, to accom- modate computer and data networking traffic, the design has been upgraded to allow transmission rates to go from 4,000 bits/sec to millions and poten- tially billions of bits/second. And, of course, installation Although the relationship between hertz and bits is not always methods have had to be upgraded accordingly. 1:1, there is a correspondence between the two. Shown on the left is a cycle of 4 hertz/second; on the right is a cycle of 4 The lexicon of data transmission bits/second. Throughout this article, I will use the terms “frequency,” “hertz,” “megahertz,” “megabits,” “gigabits.” Let’s more hertz, or bits, it takes to do so, and the more com- ensure we know what they all mean. plex the technology required to transmit it. Hertz, or cycles per second, is an analog term. A hertz In the computer and data business, all of the informa- is one electrical energy cycle, above and below the cen- tion seen on the computer screen is converted to electri- ter line, occurring in one second of time. In digital cal, or ones and zeros—a bit represented by a one and the terminology, we use the term “bit,” which is one elec- absence of a bit represented by a zero. But there are other trical energy pulse, above or below the center line or a types of information sources, such as data transducers, combination of both, occurring in one second of time. industrial devices, and cameras that are frequency-based. Multiple hertz, or bits, can occur—four, forty, thousands, In most of these cases, the frequencies are converted to even millions—in a single second. bits before they are transmitted. Often, there are significant differences between hertz JAMES ANDRESS is an engineering consultant for telecommunications and bits concerning how they are processed and convey at New Mexico State University’s Physical Science Laboratory. information; but considering our discussion on ➤ www.cablinginstall.com Cabling Installation & Maintenance ■ October 2007 ■ 9 C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  12. 12. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F Signal-to-noise ratio examples Resistance (R) is the resistance of the conductor to the pas- sage of electric current. Resistance is constant along the con- Analog signal Digital signal ductor, controlled primarily by the size of the wire (the larger Good Good S/N the wire, the less resistance it has) and the type of material S/N Poor Poor S/N (copper being the almost universal choice), and is measured in S/N ohms(Ω). Another contributing factor to overall resistance is the type, thickness, and density of the insulation. Collectively, these resistance factors result in less signal received at the receiver, a poorer SNR, and a higher bit error rate. Leakage or conductance (G) is the conductance of the insu- Noise Static lation on each conductor to the passage of current leaking out Hum to the adjacent conductor of the pair, or to the other pairs, or Crosstalk to ground. It is almost negligible in its electrical effect on the Signal-to-noise ratio (SNR) is a critical electrical performance parameter, circuit, but it is there nonetheless and needs to be mentioned. and shown here are examples of good and poor SNR in analog trans- Being very high in value, it is measured in megohms, or mil- mission (left) as well as digital transmission (right). lions of ohms. It combines with resistance to weaken the sig- nal along the pair, and is also constant along the conductor as cabling-installation specifications and practices, we can deal well as controlled by the type of insulating material, its thick- with the two terms interchangeably. ness, and its density. Another term we will use when talking about cable perfor- Inductance (L) and its current-flow-inhibiting effect, induc- mance is signal-to-noise ratio, or SNR. This is simply a num- tive resistance (X L), are also significant characteristics. Induc- ber expressing the difference between the power level of the tance is the magnetic effect of alternating current signal flow information signal in a circuit, and the power level of the noise, in a conductor. It opposes the applied signal voltage, which in hum, static, crosstalk, or other undesired interfering signals turn reduces the signal current flow, which then results in less that are also in the circuit. SNR is expressed as a ratio; the signal into the receiver, and then to a poor SNR and poorer larger the number, the better the circuit quality. BER. Inductance is also constant along the conductor. But in Directly related to SNR is bit error rate (BER). As the bit this case, the higher the signal frequency or bit rate, the higher power level gets down close to the noise level, the receiver may the current-inhibiting effect. Although inductance is inherent have difficulty deciding if there is a one or a zero at a given in any conductor, it is significantly increased when the con- period of time. If the receiver makes a mistake and reads ductor is curved or formed into a coil. The sharper the curve, a one instead of a zero, or vice versa, we have a bit error. or more rotations in a coil, or the smaller the diameter of the coil, the greater the inductance. These factors relate problems Twisted path of twisted pair resulting from tight bends or kinks in the cabling. The twisted pair is a rather high-tech precision piece of hard- Capacitance (C)—and its signal coupling effect, capacitive ware. Two areas of concern and how they relate to each other reactance (XC)—is the coupling effect of alternating current are: 1) the physical construction of the cable, and 2) the elec- signal flow between electrical conductors and components. trical characteristics of signal transmission. It allows signal coupling between the wires of a pair and The cable’s physical construction incorporates four signifi- between pairs. The common effect is crosstalk. Capacitance cant characteristics: is inherent in a conductor or component. It is also increased 1. The diameter of the conductor and conductor material; by closer spacing or by a larger-size conductor or component. 2. The type of insulating material along with its density and These factors relate to problems resulting from crushing, twist- thickness; ing, and bends that bring the conductors closer together. 3. The spacing between the insulated conductors of the pair as Impedance (Z) is a frequently discussed characteristic. well as the spacing between the four pairs in the cable; Expressed in ohms (Ω), it is a mathematical result of com- 4. The twist rate, or number of twists per inch, of the two con- bining the values of resistance, inductive reactance, and ductors of a pair—but also the relative twist rate of each of capacitive reactance. It is also a design value of all major the four pairs in the cable, each pair in a given cable having circuit components, such as transmitter, cable pair, and a different twist rate. receiver. In designing and installing a circuit, try to keep all com- The electrical characteristics of signal transmission include ponents and connections as close as possible to the design imped- the following items, each of which is complex and requires ance, which in the case of network circuits is 100 Ω. In contrast, detailed explanation: older data and telephone circuits were 600 and 900 Ω, ➤ 10 ■ October 2007 ■ Cabling Installation & Maintenance www.cablinginstall.com C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  13. 13. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F Panasonic recommends Windows Vista® Business. LEGALLY, WE CANNOT SAY EVERY SINGLE CALL WILL BE A TRIPLE PLAY. A laptop computer like the Toughbook® 19 can help you trounce the competition more than a pencil and paper ever could. At least that’s the word on the street. We built the fully-rugged Toughbook 19 to help you service customers, manage work orders, and increase productivity on-site like never before. It comes with a drop-resistant magnesium alloy case to protect the 80GB shock-mounted hard drive, a water-resistant keyboard and easy-to-read LCD. Plus, it has an optional GPS to get you where you’re going faster. All powered by the Intel® Core™ Duo Processor U2400. The Toughbook 19. It lets you crank out orders more than we can legally say. panasonic.com/toughbook/broadbandcable 1.800.662.3537 THE RUGGED ORIGINAL. Intel, Intel logo, Intel Centrino, Intel Centrino logo, Intel Inside, Intel Inside logo and Pentium are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries. Toughbook notebook PCs are covered by a 3-year limited warranty, parts and labor. To view the full text of the warranty, log on to panasonic.com/business/toughbook/support.asp. Please consult your Panasonic representative prior to purchase. ©2007 Panasonic Corporation of North America. All rights reserved. TriplePlay_CABLE_FY07-1 C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  14. 14. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F the circuit. All of these characteristics working Excess pulling tension together (or, in another sense, working against Correct form and spacing Elongation with reduced density and diameter one another) determine the electrical perfor- mance of the UTP cable. They collectively affect the smooth flow of current, which makes up the data signal, through the cable. High-tech cables are designed and constructed Excess pulling tension elongates a twisted-pair cable’s conductors and insulation which, as very precisely. The dimensions and com- this exaggerated-for-effect illustration shows, reduces the diameter of both components. position of the conductors and insu- lation are carefully controlled. We are respectively. From a practical viewpoint, when installation speaking of dimension tolerances of thousands-of-an- errors occur, such as tight bends and tie wraps, damaged inch and material compositions in parts-per-million. This is cable or components, or poor joints, the component and over- also related to the relative placement of each conductor and all design impedance is changed. And when all circuit com- its placement in the cable. So, any physical factor that distorts ponents are not working at 100 Ω, one or more impedance or affects these tolerances, even ever-so-slightly, changes the mismatches occur. inductive and capacitive design parameters, which in turn These cause, at the location of the mismatch, signal reflec- affect the electrical reactive values, which then affects the flow tions back toward the transmitter and a reduction in signal of signal current through the cable. In these cases, impedance power going to the receiver. The worse the cumulative mis- mismatches and reflections cause crosstalk, signal loss, noise, matches, the less the signal that is actually sent to the receiver, and then bit errors. resulting in poorer SNR or BER. The signal reflections are Let’s look at some of the installation specifications and see called return loss, and are expressed in dB. The higher the how even small mechanical distortions can affect transmis- dB number, the fewer installation problems and the better sion performance. • Excess pulling tension—One action that can adversely affect signal trans- mission is exerting too much pulling tension or, stated differently, stretching the cable. The Telecommunications In- dustry Association sets the maximum pulling tension at 25 pounds. When install- ers exceed that limit, it results in elonga- tion of conductors and insulation, which in turn reduces the diameter and densi- ty of those components (the insulation more so than the conductor). Exerting too much pulling tension also lengthens the twist rate of not only each individual pair but also the relative rate between each of the four pairs. In both cases, it would likely occur in isolated sec- tions, not the total cable length, de- pending on the nature of the pull. • Bend-radius violations—Violating mi- imum bend-radius limits by bending the cable too tightly or even kinking also has deleterious effects on signal transmission. Current specifications call for a minimum bend radius of four times the cable diam- ________ eter in horizontal applications. Often, you will see two values: static and dynamic. The static value is the minimum bending 12 ■ October 2007 ■ Cabling Installation & Maintenance www.cablinginstall.com C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  15. 15. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F radius of the cable after it is positioned or placed in its permanent loca- tion, with no further movement. The dynamic value is the minimum bend radius to be observed when the cable is being pulled and placed into posi- tion. This is the larger of the two num- bers because of the added stress being placed on the cable as it is being in- stalled. Ignoring the bend-radius specification results in stretching or elongating the pair twist on the outer edge of the cable, and compression or buckling of the smooth lay and pair twist on the inner edge. The normal concern is for cable in trays and race- ways in long horizontal runs. The worst problem exists when excess slack is pushed back into a pullbox or outlet box, where very tight bends or even kinking could occur. Kink- ing, which can occur even when pull- ing the cable out of its supply box, is, of course, a severe case; once done, a kink really cannot be completely undone. In any case, a kink produces a severe inductive-reactance spike. It also likely will cause the conductors to be pushed closer together. • Cinching too tightly—Fastening ca- bles too tightly with tie wraps, clamps, or staples is a specification violation. Generally, specifications are rath- er subjective about this matter, but the overall creed is not to cinch the cables so tightly that the cable can- not be gently pulled under the fas- tener, or so that the tie wrap cannot be slid along the bundle. Failing to adhere to this guideline can result in crushing the cable, thereby in- creasing the density and reducing the diameter of the insulation sur- rounding the conductor, as well as the cable sheath. Additionally, it reduces the spacing between the conductors of a pair and the ___________________ spacing among the four pairs of the cable. Finally, in extreme cases (as with a staple), the conductors can be bent or kinked. ➤ www.cablinginstall.com Cabling Installation & Maintenance ■ October 2007 ■ 13 C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  16. 16. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F receiver so that the original signal can be properly detected Example of cinching cables and decoded. If there is too much difference in the rela- Wires kinked and pushed together with insulation diameter and density crushed and reduced tive data length of each of the four pairs, some bits will be delayed too much and get recombined out of their proper order, with resultant bit errors. The specification allows for differences in propagation delays due to the different twist rates on each of the four pairs; however, when cutting the four pairs to the same length, extra care must be taken so that the retained slack does not become kinked nor violate the minimum bend radius specification. • Cable combing—Combing the cable installa- Cinching cable bundles too tightly by any means may kink or crush tion—installing or laying the cables in a tray conductors, adversely affecting their performance. neatly, side by side—is a practice not addressed in specifi- cations yet, but may soon be. It is, without question, a tech- • Insulation, jacket removal—Specifications also address the nical-performance concern. In long runs of several cables, untwisting of the twisted pairs prior to termination. Specif- it is customary to install the runs in an orderly, straight, ically, installers are told to untwist as little as possible, but in and side-by-side manner. This technique provides a very no case exceed ½-inch or extend beyond the rear of the con- neat and professional appearance; however, particularly at nector. And although it is unavoidable at the point of connec- very high data rates, it also allows the inductive reactance torization or punchdown, this action, even for a very short coupling of electric fields surrounding the conductors distance, untwists the conductors of the pair and sometimes increases the spacing between them. This concern is also Combed vs. random bundles true for the four pairs in the cable. Depending on the type of Combed installation Random lay installation connector block, specifications vary concerning how much insulation may be removed from the conductor, as well as how much sheath may be removed from the cable. Generally, specifications say to remove only as much as is absolutely necessary. The ideal case is with punchdown blocks, where no insulation is cut back at all. Disregarding the specifica- tions about insulation removal will cause a small change in the cable’s impedance, because the insulation on a con- ductor is one factor that determines impedance. Addition- ally, the sheath is the key factor in holding the four pairs in place and in relative position to one another. So, removing the sheath also removes this stabilizing factor. • Effects on delay skew—Even delay skew, an electrical char- acteristic most closely associated with the material used to insulate conductors, is subject to variation, depending on installation technique. Workmanship involves terminat- While aesthetically pleasing, neatly combed bundles are proving detri- ing the pairs of the cable in such a way that each pair is cut mental to cable performance. Randomly laid cables may not look pretty, to length in the connector or terminal block. Mechanically, but yield better results. this avoids having extra-length pairs bunched up in the connecting area. In so doing, however, each of the four pairs to more easily combine and build up, and the capacitive ends up having a slightly different length. Specifications call for reactance coupling between the conductors to further mini- a 45-nanosecond maximum delay skew, among the four cable mize. The main concern is not totally between the four pairs pairs, along a 100-meter span. That is the difference in time, in a given cable, but the cable-to-cable coupling directly among the four pairs, one to another, for the signals to prop- affecting alien crosstalk. By using a random lay, the cables agate through the cable from the transmitter to the receiver. are constantly changing their relative spacing and crossover Erroneous installation methods can have a detrimental effect. position. This reduces the chances for a long exposure to Very high data-rate signals that are divided into four parts inductive and capacitive coupling. In fact, coupling fields must be recombined in the proper order, or sequence, at the can actually experience some cancellation as they wander 14 ■ October 2007 ■ Cabling Installation & Maintenance www.cablinginstall.com C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  17. 17. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F Are you ready to feel the speed? Super fast testing with the WireScope Pro LAN Cabling Tester Agilent’s WireScope Pro tester sweeps a full 1GHz in a few seconds, boosting your test speed to new industry leading Cat 6A and Cat 7 autotest times of 9 seconds. It also accelerates your copper and fiber testing with dual- wavelength fiber probes, the elimination of field calibration, and a new auto-increment capability. The WireScope Pro tester is the only handheld to provide Alien Crosstalk (AXT) measurements simultaneously on multiple ‘exciter’ cables, as well as produce final results on the spot, so you can quickly handle any future AXT field testing requirements. Alternative approaches could take hours to complete and require PC post processing to see the results. With simple software upgrades and a robust hardware platform operating at 1 GHz frequency, you’ll save on the cost of test because you’ll stay state-of-the-art for many years, eliminating the need to buy new testers every year or two. u.s. 1-800-829-4444, ext. 5465 Experience the speed of the WireScope Pro tester now at canada 1-877-894-4414, ext. 5465 www.agilent.com/find/wirescope or by talking to one of our _____________________ www.agilent.com/find/wirescope __________________________ engineers by calling our 800 #s. © Agilent Technologies, Inc. 2006 C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  18. 18. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F in a random fashion along the cable tray or rack. the greater the reactance, or current-inhibiting effect, or induc- Even if you have followed the installation specifications per- tive reactance X L. As the data rate, frequency, or inductance fectly, it is more difficult to get good BERs at high data rates increases, XL also increases. than at lower rates. (Please note that the following formulas This can be expressed mathematically with the following for- only illustrate relationships, and should not be used for actual mula: XL=2ΠfL. 2Π is a constant with a value of 6.28; f is the circuit calculations). Critical factors are inductive and capac- data rate or frequency; and L is the inductance of the pair or itive reactance. other component at a given point in the circuit. Remember that inductance is constant along the conduc- XL exists even in all good circuits, but its effect is made worse tor; however, the higher the signal data rate, or frequency, by problems with too-tight bends, kinks and, to some extent, with staples and tie wraps. Capacitance is also constant along the conductors. But in this case, the capacitive resistance, XC, in contrast to XL, decreases as the signal data rate increases. So, with a smaller XC, or opposing effect to signal coupling, crosstalk can increase as the da- ta rate, or frequency, increases. This also can be expressed: XC = 1/2ΠfC. 2Π is the constant 6.28; f is the data rate or frequency; and C is the capacitance be- tween the pairs or other components at a given point in the circuit. Like X L , XC is a factor in well-estab- lished circuits, but its effect can eas- ily be made worse by problems with crushing, twisting, bends that bring the conductors closer together, and long installation runs of combed cable. The resistance effect also increases with higher data rates, although it is not quite as contributory as is inductive reactance. The increasing effect is due to the way the higher-frequency energy propagates along a conductor—a condition called skin effect. Also of importance is the chemical com- position of the insulating materials, which affects the impedance characteristic of an insulated conductor. Higher frequen- cies are attenuated more so than the lower ones. This effect is related to the insulation dielectric constant. (Please note that when discussing signal transmission, most spec- ifications and other literature refer to resis- tance factor as attenuation.) Quality control Installation quality and correctness lead directly to maximum signal-to-noise ratios and minimum bit errors. In that sense, sys- __________________ tem performance is up to you—the install- ers and operators of cabling systems. 16 ■ October 2007 ■ Cabling Installation & Maintenance www.cablinginstall.com C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  19. 19. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F ___________________________ _____________________ C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F
  20. 20. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F WE MADE ROOM FOR A LOT OF INNOVATIONS. INTRODUCING THE 2008 DODGE SPRINTER > The most technologically advanced commercial van on the market† > Adaptive Electronic Stability Program (ESP)‡ on all models which includes Load Adaptive Control and Electronic Roll Mitigation to help assure safer handling > Available front and rear ParkSense® helps reduce the risk of vehicle damage when parking § > Unique cargo securing features and available lashing rails help secure your cargo > For more info, visit dodge.com/sprinter, or call 800-4ADODGE. *2500 models only. †Based on Automotive News classification. ‡Always drive carefully, consistent with conditions. Always wear your seat belt and obey traffic laws. §Always check entire surroundings before backing up. Properly secure all cargo. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue Next Page EMaGS B F
  21. 21. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F Chrysler Financial is a business unit of Chrysler Financial Services. C Previous Page A Installation 7Maintenance Contents Zoom In Zoom Out Front Cover Search Issue B Next Page EMaGS F

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