You’re reading an outdated article. Please go to the recent issues to find up-to-date content.
A recent article in Electrical Contractor restated a number of common beliefs about fiber and copper cabling. Copper is slow, fiber is fast. Copper is rugged, fiber is fragile. Copper is cheap, fiber is expensive. Well, at one time, everybody believed that the world was flat and the sun revolved around the Earth, too. Let's disprove the first two beliefs right away. Copper is no longer slow. Networks like Gigabit Ethernet have versions that run on enhanced Cat 5 (1000Base-TX) already. However the electronics to make this happen are extremely powerful - as powerful as a PC itself - and will be very expensive, even when available in quantity. Secondly, the Cat 5 cables are limited to 25 pounds of pulling tension, to prevent damage to the delicate mechanical structure that provides the high performance necessary for high bit rate systems. Kinking during installation kills performance. Fiber optic cable, with a minimum pulling strength of 200 pounds, can be tied in knots without harming it. The final issue is the topic of this article - the economics of fiber versus copper in the premises network. If you directly replace Cat 5 and its electronics with fiber optics and the necessary electronics in a local area network (LAN), usually Ethernet, fiber will be more expensive. However, there are few circumstances where you would want to do that. You might take this approach if you are having electromagnetic interference problems, such as on a factory floor, and the cost would be justifiable. But proper design can make fiber comparable or even less expensive than copper. Your telephone and community antenna television (CATV) systems use fiber because it is less expensive. The designers of those networks learned early on that fiber offers new ways of designing networks. It's higher speeds and longer distance capabilities allowed new network architectures and protocols that made copper look expensive - very expensive. With today's networks, a telephone conversation costs about 1 percent as much on fiber as it does on copper. Fiber is even beginning to look cost effective for direct connections to the home if high-speed Internet connections are desired. In premises networks, most comparisons of fiber and copper ignore the technological differences between fiber and copper wiring. So lets consider the two more correctly and see what the cost issues are. Fiber's immunity to electromagnetic interference (EMI) saves you the cost of putting fiber optic cable in conduit in order to get past sources of EMI, which saves money right there. But the biggest advantage of fiber optics is its distance capability. Cat 5 (or enhanced Cat 5 or Cat 6) has a 90-meter distance limitation, which equals 295 feet. That includes the length of the cable running up and down walls to avoid HVAC systems, fluorescent lights, electrical cables, etc. Within an office building, this distance limitation requires a telecommunications closet close to the desktop to site electronics that connect all the desktops, multiplex the data onto a backbone (which is almost always fiber optics), and connect with the LAN servers or outside connections. This layout requires considerable electronics in each telecommunications closet. (See Figure 1). These electronics require space to situate them, racks to hold them, power to power them, and often heating and air conditioning to provide a suitable environment. Power quality is a major concern for computer networks. Everyone has a surge suppressor on their computers and many of us also have an uninterruptable power supply (UPS). The electronics in the telecommunications closet have equal needs. Power must be conditioned and sufficient UPS capability is necessary for an orderly shutdown of the system in the event of a power failure. Grounding is yet another concern. Noisy grounds and ground loops can cause errors in digital systems that slow down the network, so a dedicated data ground is required for each telecommunications closet. Each closet then connects to a computer room via backbone cabling. Most of the large premises networks already have fiber backbones, usually due to the length limitations on Cat 5, but grounding and electromagnetic interference (EMI) concerns are also a problem. The computer room has hubs and switches that connect all the hubs in the telecommunications closets to the servers. The same network looks a lot different on a centralized fiber optic cable system (Figure 2), since you no longer need local electronics in the telecommunications closet. Fiber optic cables can allow most network connections to be 2 km (6600 feet) long. Only gigabit Ethernet is limited to shorter lengths, 300 to 500 meters (1,000 to 1,700 feet), because all fiber does not have infinite bandwidth. The desktop is now connected on a small duplex fiber cable to a backbone cable - there are no local electronics. The connecting box is so small it can be mounted on a wall or above a ceiling. The backbone cable can contain up to 288 fibers, yet is still smaller than a bundle of a half-dozen Cat 5 cables. You need no local electronics in a telecommunications closet. All electronics are now moved to the central computer facility, where they are easier to site and manage when problems arise. You already have conditioned power, an uninterruptible power supply (UPS), and data grounds in the computer room, so handling the electronics is simple. Two very different solutions to connecting desktops are optimized now for each cabling solution. The choice is between copper (Cat 5) with local hubs versus a centralized all-fiber network. Valid cost comparisons are now possible. However, each installation is unique and many have extenuating circumstances. We'll speak in generalities and try to draw conclusions. Cost comparisons Cabling is where everybody starts, but it is really a fraction of the cost of the network. The cable only comprises a miniscule part of the whole network cost; any valid cost comparison must also include the electronics. Copper termination prices vary slightly, because copper is standardized (at least Cat 5 and Cat 5e), so pricing tends to be similar among manufacturers. Fiber, meanwhile, has several styles of connectors and cables of widely varying costs. For example, connectors cost between $1 to $15 each. The most important factor is the cost of the "drop," the standard pricing method for Cat 5 installations. Fiber is comparable to Cat 6 and only slightly more so than Cat 5e. While copper costs rise with higher performance, fiber costs continue to decline. When and if Cat 7 becomes real, fiber will be much more cost effective than Cat 7. In the backbone, a large fiber count cable will be used in either application. More fibers are needed for an all-fiber network, but incrementally adding fibers to a cable is very inexpensive. The cable installation procedure is the same for any cable, but termination costs will be incurred for every fiber. A new generation of small fiber optic connectors may make big changes in the installation of fiber cabling. These connectors are so small that cables can be terminated in a factory and installed ready to use. This should reduce both material and labor costs, making fiber even more competitive. Note also the cost of test equipment. As copper becomes more sophisticated, so do the testers. And with generations of copper cabling lasting only a couple of years, the cost of a tester, amortized over its useful life, adds considerably to the cost of a Cat 5/5e/6 installation. Fiber testers are less expensive and have a long, useful life. Fiber optic electronics are more expensive, by between $50 and $300 per link. A typical desktop computer network interface card (NIC) for 10 MB/s or 100 MB/s Ethernet on Cat 5 typically costs between $60 and $80, while a fiber network interface card (NIC) costs $100 to $400. However, several factors reduce fiber NIC prices. Small form factor fiber optic connectors are making the electronics less expensive and a new version of Ethernet on fiber will use less expensive optoelectronics. Fiber may actually be less expensive than copper, due to the complexity of the electronics and the difficulty of installing copper wiring that can support gigabit speeds. Facilities - The wild card None of the articles I have read about fiber-to-the-desk pricing compared to copper mention that the infrastructure for fiber and copper are different. Assigning real numbers to these requirements is difficult, because they vary with every installation. Estimates vary from hundreds of dollars to as much as $73,000 per closet at the new Getty Museum, arguably one of the most expensive pieces of real estate ever built! A typical value is $2,000 to $15,000 per closet, plus the cost of the floor space. If a new closet needs to be built to support the Cat 5 network electronics, construction costs escalate $5,000 to $15,000. Support Issues The Cat 5 network will have a central computer facility and telecommunications closets placed throughout the building. Electronics will be distributed throughout the building and isolating failures will be much more difficult to repair and to detect than in an all-fiber network where all electronics are in one location. Power and grounding problems in a copper network can be so localized as to require isolation and repair at individual telecommunications closets. A purely passive fiber network is highly reliable and easy to troubleshoot. This troubleshooting ability does not just apply to power and grounding problems, but also to network electronics problems. Standards In the cabling business, everyone wants to build systems that conform to standards, especially EIA/TIA 568. An all-fiber network is now covered in the 568 standards and soon all the new low-cost fiber optic connectors will be addressed. Fiber's bottom line is near copper's - All things considered If you analyze the complete network, not just its cabling costs, you may be surprised at the cost-effectiveness of fiber optic networks. Cabling costs for fiber are comparable to those of Cat 6 copper cabling. Electronics may be more expensive, but the lower costs for facilities can make fiber equal to or less expensive than copper. Perhaps the biggest cost advantage is escape from the "planned obsolescence" of copper. Right now, three generations of copper cabling, Cat 5, Cat 5e, and Cat 6 are being sold simultaneously. Cat 5 is effectively obsolete, although it is perfectly adequate for most applications. Cat 5e was developed to support Gigabit Ethernet, which is essentially a backbone application, running on fiber that is not for the desktop. Difficulties with Gigabit Ethernet on Cat 5 and Cat 5e have led to Cat 6, still in the early proposal stage, with commercial offerings being proprietary cabling systems. Copper installation means recabling regularly for new network technologies, which is unnecessary with fiber optics. So which one do you really think saves money? HAYES, a frequent contributor to Electrical Contractor, is president of Fotec in Medford, Mass. He has provided fiber optics training since 1982. He has written widely on fiber optics, including The Fiber Optics Technician's Manual. He can be reached at [email protected].