Little vertical in horizontal fiber trends

Sept. 1, 1997

Little vertical in horizontal fiber trends

The fulfillment of forecasts of growth in the use of fiber-optic cable in the horizontal portions of LANs may depend on changing end-user demands.

Steven Bartolutti Lucent Technologies

Great enhancements have been made over recent years in the handling and routing of fiber-optic cables and the connectors that tie these cables to destination points. Fiber advocates say it is the most universal medium--capable of carrying voice, data, and video communications simultaneously with less signal enhancement than that required with copper cable. Furthermore, fiber enthusiasts point out that fiber is sufficiently robust to withstand the bends and stresses prevalent in the horizontal portion of the local area network (lan) environment in addition to the fiber backbone.

So if fiber can perform effectively as part of the lan backbone infrastructure, why isn`t it enjoying greater growth in use in the horizontal, the portion of the lan that ties directly to the desktop?

Better-performing copper

Introduced in 1990, high-performance (Category 5) unshielded twisted-pair (utp) copper now makes up about 70% of lan horizontal cabling. This suggests that end-users have chosen high-performance copper as the preferred medium in lan horizontal applications. While fiber remains the leading cabling medium in building and campus backbones due to its high bandwidth and distance advantages, horizontal applications have not driven bandwidth demand to the point of requiring fiber-to-the-desk. utp`s proven ability to handle bit rates as high as 155 Mbits/sec is sufficient to support even the most demanding horizontal applications. And utp`s ability to provide high-speed transmission was strengthened two years ago with the introduction of 622-Mbit/sec high-speed cable solutions.

The introduction of even higher-speed copper cable offerings, which deliver performance at 1 Gbit/sec (six times faster than standard Category 5 copper cabling), may encourage end-users to use copper in the horizontal until well past the year 2000. Thus, end-user preference for fiber in the backbone and high-performance utp cable in the horizontal may continue for at least the next several years. Combinations of 10Base-T switching and Fast Ethernet are likely to use existing copper infrastructure in the horizontal while enhancing fiber`s use in the backbone network.

Fiber`s proliferation in building riser and campus backbone applications means it has a strong place in the private network. It is likely that end-users will support an increased role for singlemode fiber in campus backbones where long distances and high bit rates are factors. But fiber also has a place in the horizontal. It will continue to appeal to customers in the areas of education, medicine, government, science, and engineering, whose demands are not driven solely by bandwidth considerations. "Fiber drivers" for these users may be demands for enhanced distance, security, centralization of electronics, or immunity from lightning and electromagnetic interference.

So, will the industry see any substantial changes in the premises network market in the immediate future? Probably not. We now see a predominance of high-performance copper in the horizontal segment of the market. End-users have a vested interest in supporting their copper infrastructure and, for the short term, may be comfortable with a high-performance copper solution in the horizontal. Gigabit Ethernet, which has received a tremendous amount of media attention, is, today, exclusively for fiber and may remain a point-to-point switched technology used for server and switch-to-switch interconnection for some time. This will extend the life of copper-based connections in the horizontal. As a result, end-users may not see shared-media Gigabit Ethernet, especially over utp, for at least the next several years.

lan speeds continue to increase

The impact on customers of increasing lan speeds and the development of system applications that necessitate higher performance are impossible to predict. The processing capabilities of personal computers have increased at a rate unforeseen even in the information technology industry, doubling approximately every 18 months since 1991.

lan technology should support the demand for networks that can accommodate more-powerful computer processors and higher-bandwidth applications. These factors will eventually require higher-performance lans, with initial demand for 1-Gbit/sec service to the desk by the end of this decade and demand for multigigabit-per-second transmission to the desk in 10 to 15 years.

Historically, improved performance has fueled demand for higher speed throughout the industry. As a rule of thumb, one million instructions per second (mips) of processor performance has the capability to load 1 Mbit of traffic on a network. Higher demand will come with improved central processing units--beyond Pentiums--that process 200, 300, 400, or 500 mips, along with ever-more-demanding applications.

Technology advances

Recent enhancements in copper technology have tended to be along the lines of improved performance--better cable and connecting hardware and more-sophisticated encoding algorithms--all aimed at higher performance in the horizontal while using the existing copper infrastructure whenever possible.

On the fiber side, the major innovations for premises networks have focused on reducing end-user cost with improved connectors and the adoption of the single-point administration architecture, while continuing to deliver the relatively constant performance of multimode fiber in the backbone. The development of smaller-sized fiber-optic connectors may further reduce the cost of electro-optic components and provide a cost-effective choice in the horizontal. The new fiber-optic connectors should enable an increase in lan electronics port density and provide the ability to serve more users in a reduced amount of space.

A major breakthrough in technology could stimulate growth in the use of either copper or fiber. For example, a revolution in Internet capability that mandates intensive, real-time multimedia and high-bandwidth videoconferencing to the desktop represents an example of a major breakthrough that might favor the increased use of fiber. However, end-users aren`t moving to high-bandwidth multimedia applications as quickly as predicted a few years ago. In the interim, existing copper infrastructures will probably be able to handle most bandwidth requirements for at least several more years before fiber becomes a more widespread requirement because of the demand for additional services.

Education is key

Industry observers are eagerly watching research and development and trends among customers that might forecast significant changes in the use of copper, fiber, and wireless media. Each medium has its merits, and each has an appropriate place within the rapidly growing industry.

Quite simply, end-users often make infrastructure choices based on current and projected network requirements. These requirements should take into account the state of the art in each technology. However, infrastructure medium selection is often informed by an end-user`s experience and may not reflect current technology capabilities. End-users are understandably reluctant to install a cable system that will soon reach its limits, forcing facilities to be recabled within a few years.

Educating, and thus reassuring, end-users about the robustness and long-range economy of fiber is an important step in promoting a migration to fiber in the horizontal. Improved performance and cost-effectiveness will most likely play a role in end-users` decisions to increase the use of fiber beyond its current applications. In time, fiber`s advantages will likely allow it to play a more significant role in the lan horizontal.u

Steven Bartolutti is a distinguished member of the technical staff and new business development manager, global private systems, for Lucent Technologies, Norcross, GA.

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