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I am planning the construction of a two-story building and would like some advice on network cabling. We currently run only 10 MHz for approximately 90% of our campus and 100 MHz for the other 10%

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Pathways in healthcare facilities

Q: I am planning the construction of a two-story building and would like some advice on network cabling. We currently run only 10 MHz for approximately 90% of our campus and 100 MHz for the other 10%. I am installing Category 5E components exclusively and have not yet had any problems, but I am not sure what Category of cable to install in the new building. I have heard that I may run into compatibility problems with mismatched components. Also, we may have some video applications in the new building later. Our current plan is to use singlemode fiber for this purpose because of distance considerations, even though our campus backbone is currently multimode. Any suggestions?
Michael G. Jones
LSU Medical Center
Shreveport, LA

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A: Integrated switch routing of Internet-protocol (IP) traffic on a dense wavelength-division multiplexing optical-core network at the OC-192 speed of 10 Gbits/sec per wavelength will soon be coming to a demarcation point near you. And when it does, you do not want your cabling system to be a bottleneck between a device in the work area and the rest of the world. Maybe someday, there will be a standard addressing the unique situations in healthcare facilities like yours, but until then, use the ANSI/TIA/EIA-569A Commercial Building Standards for Telecommu-nications Pathways and Spaces to lay out the cabling pathways and telecommunications room locations. While it is true that a medical center is not a typical commercial office building, the bit streams will not know the difference.

Category 5E is a 100-MHz cabling system, which will accommodate 10, 100, and 1000Base-T. Use Category 5E for horizontal runs to 90 meters. If your horizontal pathway exceeds 90 meters, then use Category 3 for voice and 62.5/125-micron fiber for data.

According to IEEE 802.3, 62.5/125-micron fiber will accommodate 10- Gigabit Ethernet for 100 meters. Use 62.5/125-micron fiber as your intrabuilding backbone unless that backbone pathway exceeds 100 meters; if it does exceed 100 meters, then use 50/125-micron fiber with a bandwidth of 200/500 MHz/km. According to IEEE 802.3, this "next-generation fiber" will accommodate 10-Gigabit Ethernet for up to 300 meters. Between buildings, continue to use singlemode optical fiber.

As for "video" in the future, what kind? Analog baseband video, digital baseband video, analog broadband, broadband video, and digital broadband-each has its own set of requirements and system parameters. Twisted-pair, while ideal with some, is difficult with others. For a good explanation of the various parameters and requirements, visit www.belden.com/products/tpvutp85.htm. Special thanks go to Stephen Lampen, Belden Electronics Div., for posting "Video and UTP."

As for the mismatched-component compatibility rumors, those are with Category 6. And a resolution, or at least guidance, is being addressed within TIA TR-42, where work continues on a Category 6 cabling standard. As for those of you who cannot believe I did not personally recommend installation of Category 6, consider the following questions: Whose Category 6? Verified to what? A Category 6 system to support what applications that Category 5E cannot support? I find it hard to cost-justify bragging rights for all that "headroom."

Migrating to Ethernet

Q: Will IBM Type 2 cabling reliably support Fast Ethernet? Our building, with more than 1,000 employees, is full of Type 2 cabling because we have a Token Ring history. We are trying to make the case for an infrastructure upgrade, including horizontal fiber supporting Gigabit Ethernet and Category 5E runs supporting Fast Ethernet to the desktop. This upgrade would complement our ongoing migration to Ethernet. Upper management would like some authoritative documentation before fully supporting the idea. Our testing to date has yielded mixed results. Printers connected to the old cabling appeared to work without a problem, but when we tested clients, things got ugly. I suspect I know the answer, but any specific references, resources, or suggestions would be much appreciated.
Robert C. Thompson
Florida Department of Education
Florida

A: Yes, IBM Type 2 cabling can reliably support 100Base-T, but it cannot support 1000Base-T because that protocol requires four pairs. My advice: If funding is available, put fiber-to-the-desk throughout the facility. Use what you have for the 100Base-T now, because today, copper switches are still less expensive than fiber switches. Then use fiber for Gigabit Ethernet and beyond.

You see, 100-Mbit/sec Token Ring uses the identical physical coding as does 100Base-T. While the IEEE 802.5 Token Ring Working Group was developing 100-Mbit/sec Token Ring, testing indicated that Type 1A cable was greatly superior to Category 5E cable. Further testing indicated that the cabling served well without bothering to use impedance-matching baluns on the ends.

In fact, most Type 2 cable will operate to 300 MHz. The connectors, however, are another story. Check them. If you have Type 2 rather than Type 2A connectors, reterminate the cable on either Type 2A or your choice of insulation-displacement connector that will accept 22-AWG conductors. Type 2 and Type 2A connectors are "self-shorting," meaning that unterminated connectors will wrap signals so the transmitted signal returns on the receive pair if there is no connection on the other end.

So unless your signaling protocol requires 4-pair cabling, replacing your 150-ohm cabling with Category 5E or somebody's version of Category 6 will be costly and will actually degrade your cabling- performance capabilities.

Temperature/multiduct cable

Q: What is the maximum continuous temperature that multiduct fiber-optic cable can withstand? I am looking for a cable that can survive long-term at 90°F (about 32°C).
Phyllis Sousley
Thermal Energy Cooperative
Houston

A: Multiduct is a term typically used to describe the underground pathway into which you will place the cable. Specify a cable that meets ANSI/ICEA S-87-640 Fiber Optic Outside Plant Communications Cable. This cable will operate in a temperature range of -40° to +75°C.

Circuit points of demarcation

Q: I am working with several clients on communications-infrastructure projects, and I have noticed some differing opinions among us regarding extending circuit points of demarcation to the main crossconnect. Does a single standard address this extension, or does the applicable standard vary depending on the circuit being extended? Do different local-exchange carriers (LECs) have varying standards? Do(es) the standard(s) specify the type of cable and termination hardware to be used?
Erik Nymo, RCDD
Bailiwick Data Systems
Chanhassen, MN

A: The State Public Utility Com-mission sets regulations governing the LECs operating in their respective states. For Minnesota, see www.state.mn.us/ebranch/puc/.

Answers to your specific questions will vary from state to state. Your best bet is to contact the LEC's engineering department and ask. If warranted, they will even send an engineer out to your site.

Donna Ballast is a communications analyst at the University of Texas at Austin and a bicsi reg-istered communications distribution designer (rcdd). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, the University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: ballast@utexas.edu.

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