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End the confusion over cabling choices.

The advantages of fiber give network designers another option.

Technology today is changing at lightning speed. Networks are getting bigger and more sophisticated, with more demand for faster connections to the network and the Internet. Anyone designing or managing these networks is faced with the task of ensuring the system meets today's requirements, while providing the foundation for future needs in the most cost-effective way.

The plethora of choices available for network design can cause confusion, especially with cabling infrastructure. Whether it is a new installation, an expansion or an upgrade to an existing network, selecting the appropriate cabling can make a difference in installation costs, as well as network performance and reliability.

In recent years, copper has gone through several generations to keep up with ever-increasing bandwidth demands. Little of the older installed base, mostly Category 3, can support data rates higher than 10 Mbps, yet many networks need to run Gigabit Ethernet at least on the backbone. To that end, new generations of copper have been developed, each capable of supporting higher data rates (e.g., Category 5 was developed to support speeds higher than 100 Mbps). With the advent of Gigabit Ethernet and its more stringent installation requirements, many Category 5 installations proved to be inadequate for handling the increased bandwidth, thus, enhanced Category 5e evolved.
 Data Rate Cable Type
 Standard (Mbps)

10-Base-T 10 Category 3, 4, 5 UTP
10Base-FL 10 Multimode: 850 nm; 62.5/125[micro]m or 50/125
 Multimode: 1300 nm (nonstandard)
 Single-mode: 1300 nm: 8/125[micro]m
100Base-TX 100 Category 5 UTP
100Base-FX 100 Multimode: 1300 nm; 62.5/125[micro]m or 50/
 Single-mode: 1300 nm: 8/125[micro]m
100Base-SX 100 Multimode: 850 nm; 62.5/125[micro]m or 50/125
 (TIA/EIA-785 standard not formally adopted)
1000Base-T 1000 Category 5e UTP
1000Base-SX 1000 Multimode: 850 nm; 62.5/125[micro]m
 Multimode: 850 nm; 50/125[micro]m
1000Base-LX 1000 Multimode: 1300 nm; 62.5/125[micro]m or 50/
 Single-mode: 1300 nm: 8/125[micro]
1000Base-LH 1000 Single-mode: 1550 nm; 8/125[micro]m

 IEE Max.
 Standard Distance

10-Base-T 100 m
10Base-FL 1 km
 9 km
 20 km
100Base-TX 100 km
100Base-FX 2 km
 20 km
 300 m
1000Base-T 100 m
1000Base-SX 220 m
 550 m
1000Base-LX 550 m
 5 km
1000Base-LH 70 km

There are two additional generations of copper in the works--Category 6 and 7--that are expected to support current high-speed data rates, as well as higher speeds under development, like 10 Gbps ethernet. Backward compatibility issues have arisen with the RJ-45 connectors, however (Category 7 requires a completely new connector). Installation is more difficult, and stringent new parameters--such as equal-level far-end crosstalk (ELFEXT)--have made field testing more complex and expensive.

Reliability is a key issue due to copper's inherent vulnerability to such influences as crosstalk, EMI/RFI and temperature. By some estimates, 60% of copper-based network outages are caused by incorrectly installed cabling. Also, copper distances are limited without the use of enhancement products, such as repeaters.

Even though fiber has been in use for more than 20 years, it has only recently been recognized as a viable solution for LAN backbones and fiber to the desktop. While various organizations are grappling over the standards for the next generations of copper, fiber standards are already here. With its low attenuation, allowing for longer transmission distances and virtually unlimited bandwidth that can support the technological advances expected over the next 20 to 30 years, fiber effectively future proofs an installation and offers more flexibility in network designs.

As the popularity of fiber has grown, costs have decreased, making it nearly as inexpensive to install as copper. Because of its inherent immunity to EMI/RFI, temperature and crosstalk, fiber has been proven to be a reliable and cost-effective alternative. In addition, fiber's expanded data-handling capacity, electrical isolation, enhanced safety and data security can increase a network's reliability by as much as 80%.

Fiber's ability to go longer distances without enhancement devices, the use of small form factor connectors, and its higher pull strength (200 lbs. vs. Category 5's 25 lbs.) reduces the cost of installation and the number of wiring closets required. For example, a large eastern university found that only one central closet was required when upgrading its system with fiber vs. 14 wiring closets required with Category 5e. This translated into considerable cost savings by reducing the amount of active equipment required, lowering the cost of troubleshooting, reducing the need for security and fire-suppression equipment, and increasing network performance.

The type of fiber can make a difference in performance and costs. There are three basic types of fiber that are defined by industry standards--850 nm and 1,300 nm multimode and 1,300 nm single-mode. Long-haul 1,550 nm single-mode is also available but is not part of a formally adopted standard. Consider the following guidelines to make the best selection:

* Multimode: Straightforward migration path to future applications; backward/forward compatibility to LED-based fiber; lends itself to voice/ data applications, premises and intrabuilding networks; typically 40% to 60% lower cost than single-mode. Multimode wavelengths: 850 nm is most widely used for lower speed and shorter distances; used for fiber to the desktop; lowest cost option; 1,300 nm is designed for higher speeds and longer distances; used for high-speed backbones; moderately higher cost than 850 nm.

* Single-Mode: Virtually unlimited bandwidth to support 10 Gbps and beyond; ideal for long-distance telecommunications, interbuilding connections and metropolitan-size networks; costs are considerably higher than multimode. Single-mode wavelengths: 1,300 nm is cost-effective choice for high-speed, long-distance installations (up to 50 km), such as telephone, cable or campus backbones; used for high-speed backbones and LAN-WAN connections; installation costs are high; 1,550 nm is ideal for long-haul (up to 70 km); used for WDM/DWDM systems and high-speed metro fiber; highest cost.

With all the options available for today's cabling infrastructures, designers and installers are still faced with deciding when to recable. With a properly installed copper network, there is no reason the network expansion cannot be accomplished by installing fiber, while maintaining the legacy system using media converters. Media converters simply convert the electrical signal of copper to the optical signal of fiber with low-cost physical layer technology.

Additionally, when employing different types of fiber for different purposes within the same network, single-mode and multimode can easily coexist using low-cost fiber mode converters.

Driving the need for fiber optics is the increasing demand for broadband applications. Satisfying these demands is a critical factor for the competitive stance of most companies. While copper still requires a less expensive, short-term investment, fiber can be a more cost-effective long-term option. With fiber installed, the network is ready to move to higher-speed technology without having to recable.


LASCOMM Optical Fiber to the Desktop fibercable/fibercable.htm

RW Data, Cabling Standards Overview

Cable U training ICC

Optoelectronics Industry Development Association (OIDA)

BICSI Telecommunications Association

Fiber Optic LAN Section (FOLS) of the TIA

Institute of Electrical and Electronic Engineers (IEEE)

American National Standards Institute (ANSI)

Circle 257 for more information from IMC Networks

Bird is VP of engineering, and Morrison, director of channel marketing, at IMC Networks, Irvine, CA.
COPYRIGHT 2001 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2001 Gale, Cengage Learning. All rights reserved.

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Comment:End the confusion over cabling choices.
Author:Bird, Randy; Morrison, Jan
Publication:Communications News
Geographic Code:1USA
Date:Sep 1, 2001
Previous Article:Determine the advantages of copper and fiber.
Next Article:Fiber cable.

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