Optical Fiber: Coming in from the Cold
Aug 1, 1999 12:00 PM, By Chris Sullivan, fotec, Inc.
Most people lump all fiber-optic applications into one category, the outside plant. But, there's another category: to-the-desk LAN wiring. Here, fiber is an economical alternative.
Fiber is becoming an economical alternative to copper for LAN wiring. Why? First, the cost of fiber itself has dropped about 50% in the last few years, leading to lower prices for cable. Second, a new low-cost standard for Fast Ethernet, called 100BASE-SX, has cut the cost of fiber-optic electronics by as much as 75%. Third, a bunch of new fiber-optic connectors are coming out that offer savings in cost and space, while possibly changing the way installations themselves are done.
But, the biggest change for fiber installation is this: More and more end users are realizing, in an "apples-to-apples" comparison, fiber to the desktop can be significantly cheaper than a copper network.
The traditional UTP LAN. Let's start our comparison by focusing on the tradition UTP LAN. UTP copper cable has a maximum length of 90 m (about 290 ft), so you connect each desktop to a network hub in a nearby telecom closet by a UTP cable. Every hub connects to the main telecom closet with one cable per hub. (See Fig. 1, in original article.)
The backbone of the network can be UTP if the closets are nearby, or fiber-optic if distances are greater or the backbone runs a higher bandwidth network than copper can support.
In the telecom closet, every hub requires power and an uninterruptible power supply (UPS), since the network depends on every hub being able to survive a power outage. The closet also may have a rack (which requires proper grounding) in which to mount everything. And, you'll terminate cables in patch panels and use patch cords to connect cables to hubs.
Fiber-to-the-desk LAN. Fiber-optic cable can go as far as two kilometers (over 6000 ft), making it possible for you to bypass the local hubs and run cable straight to the main telecom closet. (See Fig. 2, in original article.) There will be a small patch panel connecting desktop cables (a fiber cable the size of a lamp cord) to a large fiber-count backbone cable. You can connect at least 72 desktops on one backbone cable, which would be hardly larger than one UTP cable. As you can see, a fiber network only has electronics in the main telecom closet and at the desktop, nothing in-between. That means you don't need power or an UPS in the telecom closet. In fact, you may not even need a closet.
A pricing comparison. In an "apples-to-apples" comparison, let's price the complete networks shown in Figs. 1 and 2. The table, in original article, provides the detailed comparison data.
One estimate on a bank with no building construction costs had fiber about $9 more per desktop. Another estimate had fiber costing about two thirds as much as UTP. A new construction estimate claims savings of millions of dollars, by eliminating all but one closet in a large campus.
On the next job you quote for a customer, consider all comparisons, and if they're interested, calculate costs.
Sidebar: Why Fiber Dominates the OSP Area
Outside plant (OSP) fiber-optic applications include CATV, telephones, and an almost invisible but enormous Internet backbone. What we call "premises cabling" includes local area networks (LANs), CCTV, security, building automation and campus backbones.
In the OSP, fiber dominates. It's used in practically 100% of the long distance telephone network, over half of the local telephone connections, and is rapidly being installed for all CATV backbones. It just proves competition is healthy, as telephone companies, alternative carriers, and CATV companies vie for the communications business of the future by installing all the bandwidth they can afford.
Only the final few hundred feet between the street and the home remain copper in the OSP market. The reason for using fiber-optics in OSP is economics. The higher bandwidth and longer distance capability of fiber-optics makes its cost only a small fraction of any copper wire, wireless, or satellite solutions. Many wireless networks, by the way, are connected by fiber to the antennas.
Sidebar: Premises Cabling Today
Within the premises cabling market today, copper dominates. Practically every desktop on a network relies on copper wire, which is almost exclusively Category 5 (Cat. 5) unshielded twisted pair (UTP.)
Common knowledge is UTP cable is inexpensive, easy to install, and can run any network you need. Besides, it's backed by an extensive standards program (EIA/TIA 568), supported by many vendors, and has a lot of history.
Unfortunately for UTP, it may be reaching a crisis point. Network performance is growing faster than UTP cabling performance. The standards committees are still haggling over the next generation of copper cabling standards, unable to decide what cabling specifications should be and how to test them. Vendors are advertising their next generation products, often with referrals to "Cat. 6"; a standard that's nowhere near written.
At the same time, installing UTP is becoming more and more difficult. The vendors have done their homework well; but, to extract the higher performance from the network, installation must be precise and trouble-free.
UTP testers are offered with performance greater than Cat. 5 and some proposals for Cat. 6. But, the cost is double that of a Cat. 5 tester from last year. There's no guarantee this tester won't be obsolete by the time the standards are finalized.