Guide to Networking Cables

The network cable is also known as the network medium. We use a network cable to interconnect two or more computers, either directly or through a network device. A network cable is a channel through which data flows within a network. It carries electrical pulses (digital signals) from one computer to another, or to any other peripheral connected to the network. In limited media, the signal is contained or carried within a physical cables. In other words, the signals traveling through this type of media will flow in a guided medium from source to destination. There are three common types of bounded media, namely: -

  • Coaxial cable
  • Twisted pair cable
  • Fiber optic cable

A. Coaxial cable

Coaxial cable consists of a solid or stranded copper core (a central conductive core), surrounded by a dielectric (special insulator), a braided or woven copper braid shield layer (which is connected to signal ground and absorbs the electromagnetic interference - EMI), and a protective outer jacket (insulating jacket). All of these layers are concentric around a common axis, hence the name coaxial.

Dielectric insulator: Surrounding the core is a layer of dielectric insulation that separates it from the wire mesh. The braided wire mesh acts as a ground and protects the core from electrical noise and crosstalk. (Crosstalk is the overflow of the signal from an adjacent cable.) Coaxial cable is largely immune to electrical interference and can carry data at higher speeds over long distances than twisted-pair cable. The conductive core and the wire mesh must always be kept separate from each other. If they touch, the wire will short circuit, and noise or stray signals on the screen will flow into the copper wire. An electrical short occurs when two lead wires or a lead wire and a ground come into contact with each other.

A short causes sparks: This contact causes a direct flow of current (or data) in an unwanted path. In the case of household electrical wiring, a short circuit will cause sparks and a blown fuse or circuit breaker. With electronic devices using low voltages, the result is not as dramatic and is often undetectable. These low-voltage shorts generally cause a device to fail; and the short, in turn, destroys the data. An external non-conductive shield, usually made of rubber, Teflon, or plastic surrounds the entire cable, this is for normal server cables protection.

Coaxial Cable Features

  • Coaxial cable is more resistant to interference and attenuation than twisted-pair cabling.
  • Transmits voice, video, and data.

B. The twisted-pair cable

This type of network cable consists of several insulated strands of copper wire twisted together. Torsion cancels electrical noise from adjacent pairs (crosstalk) and from other sources such as motors, relays, and transformers. Twisted-pair cables are often bundled and wrapped in a protective jacket to form a cable. The total number of pairs in a cable varies. They make use of RJ-45 telephone-type connectors (larger than the telephone and consists of eight cables versus the 4 cables for the telephone). They are generally inexpensive. They are easy to install.

There are two types of twisted-pair cables:

  • Unshielded twisted pair (most common)
  • Shielded twisted pair

Unshielded Twisted Pair (UTP)

This type of cable uses the 10Base-T, 100Base-TX (Fast Ethernet), 1000Base-T (Gigabit Ethernet) specifications, it is the most popular type of twisted pair cable and is rapidly becoming the most popular for structured LAN cabling. These pairs of wires are often color-coded to distinguish them. The maximum length of the cable segment is 100 meters, approximately 328 feet. If you exceed this segment length limitation, attenuation occurs. Attenuation is the gradual loss of signal strength as it tends to move away from the point of origin.

Electronic Industries Association Wiring Standard

The Electronic Industries Association and Telecommunications Industry Association (EIA / TIA) Commercial Building Cabling Standard 568A specifies the type of UTP cable to be used in a variety of construction and cabling situations. The goal is to ensure the consistency of products for customers. These standards include five categories of UTP. The higher the number of degrees, the more immune to interference and the faster you can accurately transmit data, the categories are as follows:

C. Optical media

In many parts of Africa, for example, Kenya, the use of fiber cable to route Internet communications to the rest of the world is gradually being implemented. This is a very positive development because we hope that the costs of the Internet will go down and be accessible to everyone, regardless of whether you are in the city or in the town.

So what is this fiber optic cable?

A fiber optic cable consists of an extremely thin glass cylinder called a core that is surrounded by a concentric layer of glass called a cladding. Optical fiber carries digital signals in the form of modulated pulses of light along a flexible glass tube. It uses no electricity except to power the transmit and receive circuits at each end. The outer covering is protective, while the cladding is used to reflect light signals towards the waveguide. The center conductor of a fiber optic cable is a fiber consisting of highly refined glass or plastic designed to transmit light signals with little loss. A glass core supports a longer wiring distance, but a plastic core is usually easier to work with. The fiber is coated with a coating or gel that reflects the signals back to the fiber to reduce signal loss. A plastic sleeve protects the fiber.

-- Raihan Islam - 2021-02-08


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