Horizontal cabling costs: Fiber vs. UTP
Since the Telecommunications Industry Association Fiber Optics LAN Section (FOLS) and industry educator and trainer Pearson Technologies introduced their first cost model of fiber versus unshielded-twisted-pair (UTP) copper cabling in May 2002, UTP-component, fiber-component, and switch prices have all dropped. The most exciting result of these cost reductions is they have shifted the balance in favor of the all-fiber, or centralized cabling, network. While our first-generation cost model still showed copper networks to be the lowest-cost solution for some scenarios, in our second-generation model the all-fiber solution offered a lower total initial cost than the UTP-fiber network for all 12 scenarios we examined.
The second-generation cost model includes the following changes: Prices were updated for UTP and fiber components. We "upgraded" the type of UTP cable utilized from Category 5 to 5e in nine of the 12 scenarios to reflect its current popularity and to Category 6 for the remaining scenarios. We expanded the choice of switches beyond tier one manufacturers, because we have noticed a trend for IT managers to purchase the "lowest-cost solution." Finally, we added three new scenarios to address emerging deployment trends.
The FOLS and Pearson Technologies have developed an interactive version of this cost model to help network planners and end users more easily compare the cost of a horizontal UTP/vertical fiber network to the cost of an all-fiber network—one that runs to the desktop. The model is highly flexible, allowing users to input their own values into the scenarios, thus making it completely customizable. Copies of the model, including an Excel spreadsheet, are available at the FOLS Website (www.fols.org).
As you go through this model, you'll see that one of the major differences between the UTP and fiber networks is the cost of building a telecommunications room (TR) and the cost of the related electronic equipment, estimated to total at least $20,000. While that is a necessary cost factor in the UTP part of the model, the TR and related equipment can be eliminated (or vastly reduced in size and scope) in the all-fiber system by centralizing the electronics in a single TR.
The model compares the cost of a horizontal UTP/vertical fiber network (hereafter referred to as "UTP") to the cost of a fiber to the desk network (hereafter "FTTD"). The "building" used in the model is an eight stories with 48 ports per floor. Since the cost analysis is calculated on a cost-per-port basis, this model is realistic and unbiased. In fact, any bias that exists favors the UTP/vertical fiber designs in three aspects:
- The cost of testing, which is significantly lower in the case of the all-fiber network, is not included.
- Long-term network maintenance costs, which are expected to be significantly lower in the case of the all-fiber network, are not included.
- The size of the TR has been reduced, but not as much as would be possible with an all-fiber network. A smaller TR would have further reduced the cost of the all-fiber network.
For the purposes of the model, we have assumed a total loaded labor rate of $60/hr. This rate is consistent for large U.S. cities such as Chicago, New York, and Boston, where the installation work force is unionized. Other assumptions follow.
At the desktop. In the UTP design, we assume that a 100Base-T network interface card (NIC) is installed in each computer. We obtained all UTP costs from current mail order catalogs with what we believe are competitive prices. Also in the UTP design, we assume a horizontal Category 5e plenum cable link with an average length of 150 ft. The cable cost is 30¢/ft. In the FTTD design, we assume the deployment of fiber NICs or media converters with an average horizontal cable length of 150 ft. In this design, we also assume the use of a two-fiber horizontal plenum cable. For scenarios 1–4, we use pricing for an SG-compatible cable at 10¢/ft. For scenarios 5–12, we use generic pricing of 24¢/ft. Be aware that this model is not intended to be used in place of independent pricing.
In the telecom room. In the TRs, the switch price per port reflects the higher port utilization typically experienced with fiber. Values of 70% for UTP and 90% for FTTD are from an article written by Corning. Other studies have reported similar results. The higher fiber-port utilization is due to the fact that in an all-fiber system, the ports can be "aggregated" across multiple offices or floors.
TR support. The UTP model assumes a TR of 6×10 ft on each floor. This size is arbitrary, but we believe it is significantly smaller than the typical TR in medium to large enterprises. For example, a study from the National Institutes of Health indicates a TR size of 10×15 ft is often required for a hierarchical star copper/fiber system.
In the FTTD model, we assume that the TRs on each floor are 50% of the size of the TR required for the UTP model to accommodate the telephone connections that are not part of the data network. As stated previously, we believe this TR size to be conservative. Note that should voice over Internet protocol (VoIP) be implemented, there would be no need for the TR.
The total amortized cost per square foot for the TR is estimated at $150/sq ft. That is believed to be a median value, with a realistic range of $100–$200/sq ft for large cities in the United States.
For each TR in the model, we assume an uninterruptible power supply with a cost of $1,000. The model also assumes the use of a dedicated temperature control unit in each TR with a cost of $10,000.
We estimate that the cost of lighting/heating and cooling the TR will be $1.50/sq ft/year, with a total TR cost of $20,450. The cost for environmental control appears in the UTP fiber network but not in the all-fiber network. That's because the TR in a UTP-fiber network must include temperature control to provide an environment that maximizes the reliability of the electronics; but in a centralized fiber network, such control is not needed, since the TR on each floor does not contain electronics. We acknowledge that many network TRs do not have dedicated temperature control.
Finally, in the UTP models, we have a UTP switch with a fiber Gigabit Ethernet (GbE) vertical backbone module in the TR on each floor. In the TR on each floor of the FTTD models, the connection between the horizontal and vertical fiber is by mechanical splice or interconnects. The mechanical splices are housed in a wall-mounted enclosure. The splice cost includes the cost of the splice ($7/fiber) plus the cost of the splice tray ($1/fiber).
Main-crossconnect costs. In the UTP cost model, all floors are cabled with fiber to a basement main crossconnect (MC), previously called the "central distribution facility," with a GbE module installed in the GbE switch. The vertical fiber is terminated with legacy ST-compatible or SC connectors. The backbone cable contains 62.5-µm, 160- or 200-MHz-km bandwidth fiber. In the FTTD cost model, all nodes are connected by all-fiber switches or to UTP switches with media conversion. Popular multimode fiber is used in these calculations.
Here are the 12 scenarios with our model: 1. SG-compatible equipment at list price; 2. SG-compatible equipment at 80% list price; 3. K–12 (primary education scenario); 4. Fiber to the zone; 5. Tier two electronics at "street" price; 6. Tier one electronics from mixed price sources; 7. Tier one electronics with reduced-cost switch; 8. Category 6 UTP tier one supplier; 9. Category 6 UTP tier two supplier; 10. Lowest-cost solution; 11. 100Base-SX list price; 12. 100Base-SX street price.
Space prevents us from discussing each of these in detail. (For a full description, visit www.fols.org.) However, the three cases displayed in the Table illustrate how much network managers can save using FTTD. Details of these scenarios follow.
SG-compatible at list prices.The UTP model is based on the Cisco 3550 switch in the TRs at list price. This switch is linked via fiber to a GbE switch in the MC. For the fiber model, we have used 3M's SG-compatible (VF-45) NICs at list price and the 48-port SG-compatible 100Base-F switch (VOL-5000) at list price. The switch is connected to other switches via 3M GbE modules. Horizontal-fiber-cable cost is calculated at 150 ft × 10.8¢/ft. Vertical-fiber-cable cost is calculated at 98.4 ft × 10.8/fiber/ft × 2 fibers.
K–12.The K–12 scenario includes a factor for maintenance labor that is not included in the other scenarios. This labor cost would be required if TRs are installed within 100 m of the node. Such rooms would require a technician or engineer on staff for troubleshooting and maintenance. This labor factor results in additional savings since school administrators are unable to hire a technician for such maintenance. In the model, we have conservatively estimated 1 hr/week of maintenance time per TR.
The UTP model is the same model as in the scenario above. The fiber model uses a UTP patch cord to an eight-port mini switch. This switch has a fiber link to a fiber switch in a central distribution frame.
Fiber to the zone. With one exception, the fiber to the zone (FTTZ) scenario is identical to that of the K–12 scenario. The exception is the maintenance cost, which is excluded in this scenario to make it consistent with all other scenarios (with the exception of K–12, because that is how schools evaluate FTTZ). This scenario is based on eight nodes connected by UTP to a locally installed switch. The switch is located in a typical office environment and does not need environmental control. The switch has a 100-Mbit/sec fiber uplink to an MC, which contains a main fiber switch. If multiple main switches are needed, they would be linked via GbE over UTP, the best possible use of UTP!
These scenarios demonstrate that with fiber now so economical to install and so cost-effective to maintain over the life of a network, there should be no question in the mind of end users and network planners that fiber is the most compelling infrastructure choice in a wide variety of scenarios.
John Struhar is chair of the Fiber Optics LAN Section (FOLS) and Eric Pearson is president of Pearson Technologies and a member of FOLS. Current FOLS members include 3M/Volition, ADC, Berk-Tek,CommScope, Corning, Corning Cable Systems, Fluke Networks, Leviton Voice & Data, OFS, Optek Technology, Ortronics, Panduit, Pearson Technologies, Sumitomo Electric Lightwave, and Tyco Electronics.