Optical fiber is the most frequently used medium for the longer, high bandwidth, point-to-point transmissions required on LAN backbones and on WANs. Using optical media, light is used to transmit data through thin glass or plastic fiber. Electrical signals cause a fiber-optic transmitter to generate the light signals sent down the fiber. The receiving host receives the light signals and converts them to electrical signals at the far end of the fiber. However, there is no electricity in the fiber-optic cable itself. In fact, the glass used in fiber-optic cable is a very good electrical insulator.

Physical connectivity allowed an increase in productivity by allowing the sharing of printers, servers, and software. Traditional networked systems require that the workstation remains stationary permitting moves only within the limits of the media and office area.

The introduction of wireless technology removes these restraints and brings true portability to the computing world. Currently, wireless technology does not provide the high-speed transfers, security, or uptime reliability of cabled networks. However, flexibility of wireless has justified the trade off.

Administrators often consider wireless when installing a new network or when upgrading an existing network. A simple wireless network could be working just a few minutes after the workstations are turned on. Connectivity to the Internet is provided through a wired connection, router, cable or DSL modem and a wireless access point that acts as a hub for the wireless nodes. In a residential or small office environment these devices may be combined into a single unit.

Students completing this module should be able to:

• Discuss the electrical properties of matter.
• Define voltage, resistance, impedance, current, and circuits.
• Describe the specifications and performances of different types of cable.
• Describe coaxial cable and its advantages and disadvantages over other types of cable.
• Describe shielded twisted-pair (STP) cable and its uses.
• Describe unshielded twisted-pair cable (UTP) and its uses.
• Discuss the characteristics of straight-through, crossover, and rollover cables and where each is used.
• Explain the basics of fiber-optic cable.
• Describe how fibers can guide light for long distances.
• Describe multimode and single-mode fiber.
• Describe how fiber is installed.
• Describe the type of connectors and equipment used with fiber-optic cable.
• Explain how fiber is tested to ensure that it will function properly.
• Discuss safety issues dealing with fiber-optics.