Cisco® CCNA Exam Cram Notes : Single-mode fiber, multimode fiber, copper

I. Networking Fundamentals

3. Compare physical interface and cabling types

3.1 Single-mode fiber, multimode fiber, copper

Cabling and Infrastructure: Media is the actual physical environment through which data travels as it moves from one component to another, and it connects network devices. The most common types of net-work media are twisted-pair cable, coaxial cable, fiber-optic cable, and wireless. Each media type has specific capabilities and serves specific purposes.

Twisted-pair cable: Twisted-pair is a copper wire-based cable that can be either shielded or unshielded. Twisted- pair is the most common media for network connectivity.

STP stands for Shielded Twisted Pair and UTP stands for Unshielded Twisted Pair.

Shielded Twisted Pair(STP): STP cables reduce electrical noise and electromagnetic radiation. In other words, they help to keep the signal steady, and reduce interference with other devices. Given below is a diagram showing a typical shielded twisted pair cable

Shielded Twisted Pair(STP)

Unshielded Twisted Pair(UTP): UTP cables do not have shielding to reduce interference. They are designed to cancel electromagnetic interference with the way the pairs are twisted inside the cable. Unshielded twisted cables are most widely used for office LANs, though recently wireless LANs are more widely used. Unshielded cables are lightweight, thin and flexible. They are also versatile and inexpensive. A typical UTP cable cross section is shown in the figure below:

Unshielded Twisted Pair(UTP)

Coaxial cable: Coaxial cable consists of a hollow outer cylindrical conductor that surrounds a single inner wire conducting element. Coaxial cable offers several advantages for use in LANs. It can be run with fewer boosts from repeaters, which regenerate the signals in a network so that they can cover greater distances between network nodes than either STP or UTP cable. Coaxial cable is less expensive than fiber-optic cable, and the technology is well known. It has been used for many years for all types of data communication.

Fiber-optic cable: Fiber-optic cable is a networking medium capable of conducting modulated light trans-mission. Fiber-optic cable used for networking consists of two fibers encased in separate sheaths. That is each optical fiber is surrounded by layers of protective buffer material usually a plastic shield, then a plastic such as Kevlar, and finally, an outer jacket that provides protection for the entire cable. The plastic conforms to appropriate fire and building codes. The purpose of the Kevlar is to furnish additional cushioning and protection for the fragile, hair-thin glass fibers. Where buried fiber-optic cables are required by codes, a stainless steel wire is sometimes included for added strength. Several connectors can connect fiber to the networking device the most common is a SC connector, which has two optics, one connecting to transmit and the other connecting to receive.

Fiber-optic cable

Fiber-optic cable does not carry electrical impulses as copper wire does. Instead, signals that represent bits are converted into pulses of light. Two types of fiber-optic cable exist:

Single-mode: Single-mode fiber-optic cable allows only one mode (or wavelength) of light to propagate through the fiber. This type of cable is capable of higher band-width and greater distances than multimode and is often used for campus backbones. Single-mode cable uses lasers as the light-generating method and is more expensive than multimode cable. The maximum cable length of single-mode cable is 60+ km (37+ miles).

Multimode: Multimode fiber-optic cable allows multiple modes of light to propagate through the fiber. Multimode cable is often used for workgroup applications, using Light Emitting Diodes (LEDs) as light-generating devices. The maximum length of multimode cable is 2 km (1.2 miles).

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