Fiber
Fiber-optic cabling is the most expensive type of those discussed for this exam. Although it's an excellent medium, it's often not used because of the cost of implementing it. It has a glass core within a rubber outer coating and uses beams of light rather than electrical signals to relay data. Because light doesn't diminish over distance the way electrical signals do, this cabling can run for distances measured in kilometers with transmission speeds from 100Mbps up to 1Gbps or higher.

Often, fiber is used to connect runs to wiring closets where they break out into UTP or other cabling types, or as other types of backbones. Fiber-optic cable can use a number of different connectors but three you need to know for exam are: ST, SC, and LC. ST is a barrel-shaped connector, while SC is squared and easier to connect in small spaces. The LC connector looks similar to SC but adds a flange on the top (much like an RJ-45 connector) to keep it security connected. The following figure shows fiber connectors: ST, SC, and LC.

NOTE: FC connectors may also be used but are not as common. MT-RJ is a popular connector for two fibers in a small form factor. Neither of these are tested on the A+ exam.

Because fiber-based media use light transmissions instead of electronic pulses, such problems as EMI, crosstalk, and attenuation become nonissues. Fiber gets around the limitations on almost everything else expect cost and is well suited for transferring data, video, and voice transmissions. Since anyone trying to access data signals on a fiber-optic cable must physically tap into the medium, it is the most secure of all cable media.

Two types of fiber-optic cable are available: single-mode and multi-mode.  As the name implies, single-mode uses a single direct beam of light, thus allowing for greater distances and increased transfer speeds. With multi-mode, a lot of light beams travel through the cable, bouncing off the cable walls; this weakens the signal, reducing the length and speed at which the data signal can travel.

The most common types of fiber-optic cable include the following:

• 8.3-micron core/125-micron cladding single mode
• 50-micron core/125-micron cladding multimode
• 62.5-micron core/125-micron cladding multimode

Twisted Pair
There are two primary types of twisted pair cabling (with categories beneath each: shielded twisted pair (STP) and unshielded twisted pair (UTP). In both cases, it is made up of pairs of wires twisted around each other. UTP offers no shielding (hence the name) and is the network cabling type most prone to outside interference. The interference can be from a fluorescent light ballast, electrical motor, or other such source (known as electromagnetic interference [EMI]) or from wires being too close together and signals jumping across them (known as crosstalk). STP adds a foil shield around the twisted wires to protect against EMI.

STP cable uses IBM data connector (IDC) or universal data connector (UDC) ends and connects to token ring networks. While you need to know STP for the exam, you are not required to have any knowledge of the connectors associated with it. You must, however, know that most UTP cable uses RJ-45 connectors that look like telephone connectors (RJ-11) but have eight wires instead of four.  The following figure shows both RJ-45 (left) and RJ-11 (right) connectors.

There are two wiring standards commonly used with twisted pair cabling: T568A and T568B (sometimes referred to simply as 568A and 568B). These are telecommunications standards from TIA and EIA that specify the pin arrangements for the RJ-45 connectors on UTP or STP cables. The number "568" refers to the order in which the wires within the Category 5 cable are terminated and attached to the connector. The signal is identical for both.

T568A was the first standard, and released in 1991. Ten years later, in 2001, T568B was released. Pin numbers are read left to right, with the connector tab facing down. The pinouts stay the same and the only difference is in the color coding of the wiring.

There are different grades, which are given as categories; and as you may guess, the higher the grade, the more expensive the cabling, and the higher the data rate it can support. You do not need to know all of the categories for the exam, but the breakout on the ones you do need to know is as follows:

CAT3: Transmits data at speeds up to 10Mbps with a possible bandwidth of 16MHz It contains four twisted pairs of wires with three twists per foot. This is the lowest-level cabling you can safely use in a network. For many years, it was the standard used, but since cabling today considers 100Mbps to be a minimum, CAT3 has been pushed to legacy installations.

CAT5: Transmits data at speeds up to 100Mbps and was used with Fast Ethernet (operating at 100Mbps) with a transmission range of 100 meters. It contains four twisted pairs of copper wire to give the most protection. Although it had its share of popularity (being used primarily for 10/100 Ethernet networking), it is now an outdated standard. Newer implementations use the 5e standard.

CAT5e: Transmits data at speeds up to 1Gbps (1000Mbps). Category 5e cabling can be used up to 100 meters, depending on the implementation and standard used and provides a minimum of 100MHz of bandwidth. It also contains four twisted pairs of copper wire, but they're physically separated and contain more twists per foot than Category 5 to provide maximum interference protection.

CAT6: Transmits data at speed up to 10Gbps, has a minimum of 250MHz of bandwidth and specifies cable lengths up to 100 meters. It contains four twisted pairs of copper wire and is used in 10GBaseT networks. Category 6 cable typically is made up of four twisted pairs of copper wire, but its capabilities far exceed those of other cable types. Category 6 twisted pair uses a longitudinal separator, which separates each of the four pairs of wires from each other, reduces the amount of crosstalk possible.

Coaxial
Coaxial cable, or coax, is one of the oldest media used in networks. Coax is built around a center conductor or core that is used to carry data from point to point. The center conductor has an insulator wrapped around it, a shield over the insulator, and a nonconductive sheath around the shielding. This construction allows the conducting core to be relatively free from outside interference. The shielding also prevents the conducting core from emanating signals externally from the cable.

NOTE: Before you read any further, accept the fact that the odds are incredibly slim that you will ever need to know about coax for a new installation in the real world (with the possible exception of RG-6, which is used from the wall to a cable modem). If you do come across it, it will be in an existing installation and one of the first things you'll recommend is that it be changed. That said, you do need to know about coax for this exam.

Connections to a coax occur through a wide variety of connectors, often referred to as plumbing. These connectors provide a modular design that allows for easy expansion. The three primary connections used in this case are the T-connector, the inline connector, and the terminating connector (also known as a terminating resistor or terminator).

In addition to these, there are also F-connectors (commonly called F-type connectors). These are screw-on connectors used to attach coaxial cable (including RG-59 and RG-6) to devices. They have a "nut" on the connection that provides something to grip as the connection is tightened by hand (or, if necessary, pliers to aid with disconnecting). F-connectors are most commonly associated with connecting Internet modems to cable or satellite Internet service providers' (ISPs') equipment. However, F-Type connectors are also used to connect to some proprietary peripherals.

In a coax network, some type of device must terminate all the coax ends. Coax is present in many older networks and tends to provide reliable service once it's installed. However, if a terminator, NIC, T-connector, or inline connector malfunctions or becomes disconnected, the entire segment of wire in that network will malfunction and network services will cease operation. Coax tends also to become brittle over time, and it can fail when handled. In addition, coax is expensive per foot when compared to UTP cable. These are the primary reasons that coax is falling from favor as a primary network media.