Fiber optic cable transmits light (photons) instead of electricity, and this light is transmitted over glass or plastic. Glass is known as the media for fiber optics, just like copper is known as the media for twisted-pair cabling. The glass or plastic strands in fiber optic cabling are extremely small; in fact, they are measured in microns.

Because fiber optic cable is rarer than twisted-pair cable in networks, and because it is expensive, we will search the Internet for the various types of cables and connectors.
If you happen to have fiber optic cables, connectors, and devices available, attempt to identify those after you have completed the following steps:
1. Execute a Bing search in the Images section for “optical fiber.”
2. Run Bing searches for the following connector images:
• FC connector
• LC connector
• MT-RJ connector
• SC connector
• ST connector
3. Execute a Bing image search for the following devices:
• Fiber optic network adapter
• Fiber optic switch
• Fiber optic router
4. If you do have any fiber optic equipment handy, go ahead and identify it now, based on what you have seen on the Internet.
Fiber optic cable can be either single mode or multi-mode:

• Single-mode (SM) optic is a cable with an optical fiber that is meant to carry a single ray of light—one ray of light, one mode. This type of cable is normally used for longer distance runs, generally 10 km and up to 80 km.
• Multi-mode (MM) optic is a cable with a larger fiber core, capable of carrying multiple rays of light. This type of cable is used for shorter distance runs, up to 600 meters.Though much shorter than single mode fiber runs, this is still six times the distance of twisted-pair cable runs.

Usually, fiber optic cable is used for high-speed connections, backbone connections, storage area networks (SANs), and direct connections between servers. 1 Gbps and 10 Gbps speeds are common, although you will still see 100 Mbps connections. Table 3-3 defines some of the 100 Mbps, 1 Gbps, and 10 Gbps versions of fiber optics, as well as their medium type and typical maximum distance.



When it comes to interference, a cable itself can be its worst enemy. Generally, fiber optic cables are not affected by EMI, because they are inherently light based, not electricity based.Although a fiber optic cable will still produce a type of electromagnetic radiation, the cable is not traditionally affected by EMI in the same way copper-based cables are. However, if a fiber run is installed improperly, it can give strange results when it comes to the data signal. Exact installation rules must be followed including proper termination, specific radii for turns, avoiding bunching, and so on. Improper installation results in the signal becoming “bent,” which causes data loss. Chromatic dispersion is also a factor, as opposed to attenuation on twisted-pair cables. If the light is refracted too often, again, the signal will degrade. Fiber optic cable in general is the most secure cable, allows for the longest runs, and offers data transfer rates that are equal to or greater than twisted-pair cable. However, due to the complexity of installation, cost, and so on, fiber optic cable is not usually a first choice for all of the individual client computer runs. Instead, it is used for backbone connections; switch connections at the top of hierarchical star topologies, and other high-bandwidth or long-distance applications.

Note: Fiber optic cable is employed when longer distance runs and even higher data transfer rates are needed. Fiber optic cables are used as part of the backbone of the fastest networks. However, they are far more difficult to install and to maintain, as well as to troubleshoot.