When Installing Fiber to the Desktop Makes Sense

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According to conventional wisdom, fiber-to-the-desk (FTTD) architecture will be cost-effective "in a few years." However, evidence from contractors, system designers, and installers, along with results obtained by interactive cost models, shows that FTTD is already cost-effective in many scenarios.

Not only is the installed first cost of a fiber-based system often within 20% of a copper-based system, but in some cases fiber is also at cost parity or even less expensive. In addition, fiber users can enjoy the long-term benefits of fiber cable—higher bandwidth, easy scalability, and lower maintenance over a network life of 10-15 years.

Why does unshielded twisted-pair (UTP) copper cable still dominate to the desktop? Perhaps the largest barrier to entry is perception. Although multimode fiber (MMF) is used extensively in building backbones, when end users consider cabling options for the horizontal, they often choose traditional copper paths rather than take new information about fiber into account. Once users are more educated, they should become more comfortable with installing FTTD, especially realizing that fiber will take them seamlessly to their next-generation network and support the high-bandwidth applications and high data rates that are just around the corner.

Today, unlike several years ago, fiber cable costs less, electronics prices are down, and installers are more comfortable with fiber installation techniques, thus lowering labor costs. Many new products are now available that facilitate fiber deployment and reduce overall system cost. They include small-form-factor (SFF) connectors, which increase port density because of their small size, and media converters, which allow users to continue using legacy copper equipment until the end of its useful life.

Network designers are also learning to take advantage of fiber's high bandwidth and low attenuation to support fiber-friendly architectures such as centralized cabling. MMF can support gigabit-level speeds over distances up to 300 m using 62.5/125-µm fiber and up to 500 m using 50/125-µm MMF. The new generation of laser-optimized 50-µm MMFs support applications from 10 Mbits/sec to 10 Gbits/sec at distances of 600 m. In comparison, Category 5E and 6 UTP are restricted to 1 Gbit/sec for 100 m.

Finally, users have a clear and cost-effective migration path from 10-Mbit/sec fiber Ethernet to 100-Mbit/sec fiber Fast Ethernet (FE) with 100Base-SX products compliant with the new TIA/EIA-785 standard for short-wavelength FE. Using low-cost 850-nm short-wavelength LED optoelectronics, these products allow users to support 100 Mbits/sec over distances of 300 m with auto-negotiation and parallel detection capabilities to ensure interoperability with older 10-Mbit/sec-only fiber Ethernet electronics.

Another element working in fiber's favor is that the cost and complexity of installing new grades of UTP copper are increasing. Cat 5E and 6 cable and components are more expensive. Getting full throughput on the system requires extremely precise installation techniques, which installers must learn, and specifically tuned test equipment. In contrast, fiber-optic cable offers greater pulling strength and is immune to electromagnetic interference (EMI), radio-frequency interference (RFI), and crosstalk. Fiber is also smaller in diameter, lighter in weight, and considerably easier to test.

When evaluating the installed first costs of structured cabling systems, many experts rely on a cost-per-port analysis. That levels the playing field because UTP and fiber-based systems are often designed in very different ways. Simply costing out a fiber overlay of a typical copper system does not always provide an accurate comparison.

UTP networks are typically designed using a hierarchical star or distributed architecture, which have multiple telecommunications rooms (TRs) on every floor of a building. This design suits copper systems because of the cable's distance limitations and the relatively low cost of the electronics.

Even so, research conducted by the Tolly Group (Manasquan, NJ) showed that TR costs could exceed $30,000, especially considering that TRs often need to have dedicated environmental control systems and uninterruptible power supplies. One result of a distributed network is that copper-based networks often only use about 70% of their switch ports. Since switch ports are one of the most costly elements of a structured cabling system, it is desirable to have as few unused ports as possible.

Fiber-based networks are most efficient when designed using centralized cabling or collapsed backbone architectures. In a fiber system, TRs and related equipment can be eliminated or significantly reduced in size and scope by locating the electronics in a single, centralized equipment room (ER).

Fiber enables a centralized cabling architecture because MMF can support cabling runs of 300 m or longer for most applications. Using centralized cabling also reduces the number of unused ports, since ports can be aggregated from multiple locations (different floors). Switch-port use in centralized designs is typically 90%—the 20% differential results in real and immediate savings.

SFF connectors can also help increase port use in fiber-based networks. Because of their small footprint, they enable network designers to increase port densities up to 100%. They are generally considered easier to install and terminate than previous generations of fiber connectors, greatly reducing installation time.

Media converters are frequently used as a way to leverage a company's legacy investment in copper switch ports and network-interface-controller cards. The use of media converters allows companies to upgrade their networks incrementally, bringing fiber to the areas that need it first.

So who's installing FTTD today? There are many types of companies that understand the new economics of fiber and are installing FTTD today. They span many vertical industries, including education and manufacturing, that share the need for reliable performance, low maintenance, and scalability.

Schools—from elementary to universities—are one of the largest proponents of fiber for a very important reason. Since funding is so limited for facility upgrades, administrators are compelled to find a solution that will support their network needs well into the future. These "power users" are implementing very-high-bandwidth applications such as streaming video and media retrieval. Even ubiquitous applications like e-mail are consuming large amounts of bandwidth.

According to the director of systems programming at Binghampton University (Binghampton, NY), the number of e-mails received at the university doubled in only three years, from 50,000 in 1997 to 100,000 in 2000. Many network managers are concerned that if they install copper, their networks will need a costly upgrade in three to five years. Fiber gives them a longer network life and often costs the same or less than copper.

Marty Crabill, president of Wire-to-Wire (Mason, OH), sees many educational institutions choosing fiber over copper. He says that 80% of the jobs his firm designs and installs include at least fiber in the backbone and about 30% include fiber in the horizontal. According to Crabill, fiber is not always the solution that his customers first recognize. Many believe the most economical solution will be copper-based. But when they look at the costs associated with Cat 5E and 6, they are surprised that fiber is so economical.

Once convinced that a fiber installation will come within 20% of the cost of copper, Crabill says seven in 10 clients will choose fiber. Optical fiber provides consistent transmission quality and performance. The new fiber installations are more robust than new grades of copper, which need to be installed with great accuracy to perform at their rated throughput.

Crabill designed an installation in 2000 for the Ohio Board of Regents (Columbus, OH) that was originally planned to be Cat 6 UTP. With limited duct space and a need to improve voice and data solutions, the board was intrigued by the benefits of FTTD. Since MMF offered them the solution they needed for essentially the same cost as copper, the board chose to install 50-µm MMF in two buildings, one with 148 drops and the other with 50 drops. A centralized cabling architecture was used that reduced the number of TRs, which in turn enabled a reduction in the number of technicians needed to maintain the network.

Crabill also designed the FTTD system installed by the St. John's County Public School District (St. Augustine, FL). Encompassing 28 schools, Wire-to-Wire began the job in 1999. To date, it has designed systems for 25 schools and completed 22 installations. St. John's wanted to incorporate streaming voice and video into classrooms, and their current network did not have the bandwidth to support it.

The school district was running 10 Mbits/sec over Cat 5 UTP copper at the time they decided to upgrade. They tried to migrate to 100 Mbits/sec over the installed network, but couldn't get it to work properly. Although it worked for 10-Mbit/sec Ethernet, it couldn't support 100-Mbit/sec FE with sufficient quality of service.

Fiber provided a much cleaner signal, with virtually no collisions. Ultimately, the school district chose to install an SFF fiber-compatible system, using a centralized cabling to reduce the number of TRs.

Manufacturing facilities may well seem worlds away from schools and universities. They typically benefit from installing fiber networks because of fiber's immunity to EMI/RFI and because fiber can support such long cabling runs.

The Gleason Works (Rochester, NY), a gearing technology company, ultimately chose fiber for these reasons. Gleason manufactures the machinery used to produce, finish, and test gears. Its facility occupies 700,000 sq ft of production space in a building a quarter-mile long and nearly 700 ft deep. The Gleason Works was ready for an upgrade. Since the early 1980s, it had used a thick Ethernet (heavy coaxial-cable) network for data communications, materials movement, time management, and remote operation of machines within the plant. It had become difficult to locate replacement components for the network. The thick cables occupied too much space in the cable trays, and each backbone cable was limited to about 100 drops. In addtion, the company had decided to implement an enterprise business software solution to streamline its operation.

To find the best solution, network designers spent a year testing and reviewing different plans. They determined copper was not suitable, since cabling distance limitations meant they would need to add 20 more TRs—taking up valuable real estate and increasing the cost of the electronics. Additionally, the high EMI environment would increase the bit-error rate over a copper infrastructure and cause network slowdowns, a problem that would only worsen as network speeds increased.

Network planners also evaluated wireless LAN technology. However, the plant is full of metallic equipment and support structures that impede wireless transmission. The constantly changing physical environment, such as equipment moves and cranes sliding from place to place, would continually change the RFI transmission patterns in the plant. To ensure adequate and complete coverage, a large number of wireless access points would be required.

In the end, Gleason installed a fiber-to-the-machine network with a Gigabit Ethernet backbone consisting of 24 fibers each of MMF and dark singlemode fiber. The installation required adding just three new TRs. Fiber cables carry 100 Mbits/sec switched Ethernet to within 3 m of workstations, where media converters provide short connections via copper to the computers. The fiber cable runs are as long as 335 m, and the fiber drops are as long as 205 m.

To help potential users compare the relative costs of deploying fiber or copper in the horizontal, members of the TIA Fiber Optics LAN Section (FOLS) and Pearson Technologies developed a series of scenarios and interactive cost models available on the FOLS Website at www.fols.org. Used together, these tools compare the cost of a hierarchical star horizontal UTP/vertical fiber network to the cost of a centralized, all-fiber network, where fiber is run to each desktop (see Tables 1 and 2). Th 108703

This cost model for a fiber backbone with unshielded twisted-pair copper cable in the horizontal uses a Cisco 3548 switch linked by fiber to a Gigabit Ethernet switch.

The "building" used in the model is eight stories high and has 48 ports per floor. Costs are calculated on a per-port basis. The model calculates costs for nine different scenarios using different combinations of components. Since the model is flexible, users can also input their own values into the scenarios for comparisons and cost estimates.Th 108704

This cost model for a fiber-to-the-desk solution uses SG network interface controllers at street price (80% of list) and a 48-port SG 100Base-FX switch.

For many scenarios, installed first cost is no longer a barrier to installing fiber. In fact, high-bandwidth applications—and even the ever-increasing glut of e-mail—mean that users in every sector should seriously consider fiber for their new installations or upgrades.

Dave Cook, marketing manager at 3M/Volition Systems, wrote this article on behalf of the Fiber Optics LAN Section of the Telecommunications Industry Association (Arlington, VA).

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