Published In March 2001
Fiber optics is always expected to cost much more than copper cabling. Whatever you look at—cable, terminations, or networking electronics—fiber costs more. So isn’t it obvious that fiber networks are more expensive than copper? Maybe not! There is more to consider before deciding this. Why use fiber? If fiber is more expensive, why have all the telephone networks been converted to fiber? And why are all the CATV systems converting to fiber too? Are their networks that different? Is there something they know we don’t? Telcos use fiber because it has thousands of times the bandwidth of copper wire and can carry signals hundreds of times further before needing a repeater. The CATV companies use fiber because it gives them greater reliability and the opportunity to offer new services, like telephone service and Internet connections. Both telcos and CATV operators use fiber for economic reasons, but their cost justification requires adopting new network architectures to take advantage of fiber’s strengths. A well-designed premises cabling network can also be less expensive when done in fiber instead of copper. There are several good examples of fiber being less expensive, so let’s examine them. Industrial networks In an industrial environment, electromagnetic interference (EMI) is often a big problem. Motors, relays, welders, and other industrial equipment generate a tremendous amount of electrical noise that can cause major problems with copper cabling, especially unshielded cable like Cat 5. In order to run copper cable in an industrial environment, it is often necessary to pull it through conduit to provide adequate shielding. With fiber optics, you have complete immunity to EMI. You only need to choose a cable type that is rugged enough for the installation, with breakout cable being a good choice for its heavy-duty construction. The fiber optic cable can be installed easily from point to point, passing right next to major sources of EMI with no effect. Conversion from copper networks is easy with media converters, gadgets that convert most types of systems to fiber optics. Even with the media converters, the cost of the fiber optic network will be less than that of copper cabling in conduit. Long cable runs Most networks are designed around structured cabling installed per EIA/TIA 568 standards. This standard calls for 90 meters (295 feet) of permanently installed unshielded twisted pair (UTP) cable and 10 meters (33 feet) of patch cords. But suppose you need to connect two buildings or more? The distance often exceeds 90 meters by the time you include the runs between the buildings plus what you need inside each building. By the time you buy special aerial or underground waterproof copper cable and repeaters, you will usually spend more than if you bought some outside plant fiber optic cable and a couple of media converters. Exceeding two links (180 meters) guarantees that it will be less expensive. Centralized fiber LANs When most contractors and end users look at fiber optics versus Cat 5e cabling for a local area network (LAN), they compare the same old copper LAN with fiber directly replacing the copper links. The fiber optic cable costs slightly more than Cat 5e, as do terminations, but the big difference is with the electronics, which cost an additional $200 or more per link for fiber. However, the real difference comes if you use a centralized fiber optic network. Since fiber does not have the 90-meter distance limitation of UTP cable, you can place all electronics in one location in or near the computer room. The telecommunications closet is only used for passive connection of backbone fiber optic cables, so no power, UPS, ground or air conditioning is needed. These auxiliary services, necessary with Cat 5 hubs, cost a tremendous amount of money in each closet. In addition, having all the fiber optic hubs in one location means better use of the hardware, with fewer unused ports. Since ports in modular hubs must be added in modules of eight or 16, it’s not uncommon with a hub in a telecommunications closet to have many empty ports in a module. With a centralized fiber system, you can add modules more efficiently as you are supporting many more desktop locations but need never have more than one module with open ports. High-speed networking Over a year after Gigabit Ethernet (GbE) became available on fiber optics, it has finally become available on enhanced Cat 5. But most of today’s GbE installations are 1000Base-SX (GbE on multimode fiber with 850 nm VCSEL sources), as much as 90 percent, according to one of my sources. The problem with the Cat 5e version is cost! In order to get GbE to work over Cat 5e, the electronics must be very complicated, and consequently as expensive as fiber. A newer version is awaiting a Cat 6 standard, but that means the version running over Cat 5e will be obsolete before it even gets started! Finally, at a recent major distributor’s seminar on advanced cabling, the copper marketing representative advised us to use fiber for GbE. Bottom line So, looking at the cabling component costs may not be a good way to analyze total network costs. Consider the total system and fiber may look a lot more attractive. HAYES, a frequent contributor to Electrical Contractor, is president of Fotec in Medford, Mass. He has written widely on fiber optics, including The Fiber Optics Technician’s Manual. He can be reached at email@example.com.