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When planning a new or upgraded cabling infrastructure, you have two basic choices-fiber or copper. Both offer superior data transmission. The decision on which one to use may be difficult. It will often depend on your current network, your future networking needs, and your particular application, including bandwidth, distances, environment, cost, and more. In some cases, copper may be a better choice; in other situations, fiber offers advantages.

Choosing between copper and fiber optic solutions is sometimes difficult, as distance, cost, required bandwidth, and specialized expertise need to be considered. Although copper cable is currently more popular and much more predominant in structured cabling systems and networks, fiber is quickly gaining momentum. Fiber optic cable is favored for applications that need high bandwidth, long distances, and complete immunity to electrical interference.

It's ideal for high data-rate systems such as Gigabit Ethernet, FDDI, multimedia, ATM, SONET, fiber channel, or any other network that requires the transfer of large, bandwidth-consuming data files, particularly over long distances. A common application for fiber optic cable is as a network backbone, where huge amounts of data are transmitted. To help you decide if fiber is right for your new network or if you want to migrate to fiber, take a look at the following Table.

Fiber Variety
There are three types of fiber available in data networking-50/125 mm multimode fiber, 62.5/125 mm multimode fiber and 9/125 mm single mode fiber. The figures 50 mm, 62.5 mm and 9 mm refer to the diameter of the inner glass core in which light travels. The figure 125 mm refers to the diameter of the glass outer cladding.

As each fiber shares the same outer diameter, the mechanical properties of the fibers are identical. However, the optical properties vary significantly.

Multimode cable comes with two different core sizes: 50 micron or 62.5 micron. Multimode fibers have a large core, which allows less critical alignment and can be used with low cost LED technology. However, because of the core diameter the bandwidth is limited. Multimode fiber optic cable can be used for most general fiber applications. It's ideal to use multimode fiber for bringing fiber to the desktop, for adding segments to your existing network, or in smaller applications such as alarm systems.

Single mode fiber, on the other hand, has almost unlimited bandwidth due to the small core supporting only one light mode. But, this requires very high precision alignment in both joints and connectors and the need to use expensive laser technology to drive the fiber. Single mode is used over distances longer than a few miles. Telcos use it for connections between switching offices. Single mode cable features an 8.5-micron glass core. These factors combine to make a single mode installation approximately four times more expensive than a multimode installation.

Duplex or Simplex?
It is advised to use duplex multimode or single mode fiber optic cable for applications that require simultaneous, bidirectional data transfer. Workstations, fiber switches and servers, fiber modems, and similar hardware require duplex cable. Duplex is available in single-and multimode.

Because simplex fiber optic cable consists of only one fiber link, you should use it for applications that only require one-way data transfer; for instance, an interstate trucking scale that sends the weight of the truck to a monitoring station or an oil line monitor that sends data about oil flow to a central location. Simplex fiber comes in single-and multimode types.

50- vs 62.5-micron Cable
Although 50-micron fiber cable features a smaller core, which is the light-carrying portion of the fiber, both 62.5- and 50-micron cable feature the same glass cladding diameter of 125 microns. You can use both in the same types of networks, although 50-micron cable is recommended for premise applications: backbone, horizontal, and intrabuilding connections, and should be considered especially for any new construction and installations. And both can use either LED or laser light sources.

The big difference between 50-micron and 62.5-micron cable is in bandwidth. A 50-micron cable features three times the bandwidth of standard 62.5-micron cable, particularly at 850 nm. The 850-nm wavelength is becoming more important as lasers are being used more frequently as a light source.

Other differences are distance and speed. A 50-micron cable provides longer link lengths and/or higher speeds in the 850-nm wavelength.