| A transmission medium is required to carry information | | | | protected by a plastic cover. |
| from a source to a destination. The information is | | | | These cables are categorized by RG (radio |
| usually a signal that has to travel a long distance. For | | | | government) ratings. RG-59 used for Cable TV, |
| this, the transmission media can be wired or wireless. In | | | | RG-58 for thin Ethernet and RG-11 for thick Ethernet. |
| wired transmission, the signal travels along the cable | | | | The connector used in these cables is called BNC |
| from one device to another. But in wireless | | | | connector; it is used to connect the end of the cable to |
| transmission the electromagnetic waves are | | | | a device. |
| transmitted without using a physical conductor. There | | | | Though the coaxial cable has higher bandwidth, but its |
| are three types of cables such as. | | | | attenuation is much higher compare to twisted-pair |
| 1- Twisted pair cable | | | | cables. It is widely used in digital telephone networks |
| 2- Coaxial cable | | | | where a single cable can carry data up to 600 Mbps. |
| 3- Fiber optic cable | | | | Cable TV networks use RG-59 coaxial cable. |
| Twisted-Pair Cable | | | | Traditional Ethernet LANs also use this cable. |
| A twisted pair cable consists of two copper | | | | Fiber-Optic Cable |
| conductors, each one with its own plastic insulation and | | | | A fiber optic cable transmits signals in the form of light. |
| twisted together. One wire carries the signal and other | | | | Optical fiber use reflection to guide light through a |
| is used as ground reference. The advantage of | | | | channel. It consists of two main parts: core and |
| twisting is that both wires are equally affected by | | | | cladding. Core is denser compare to cladding and is |
| external influences. So the unwanted signals are | | | | made up of plastic or glass. Cladding acts as a |
| canceled out as the receiver calculates the difference | | | | protective cover to core. The difference in density of |
| between signals in two wires. | | | | core and cladding is such that a beam of light moving |
| This cable is of two types such as. | | | | through the core is reflected off the cladding, instead |
| 1- UTP (unshielded twisted pair) | | | | of being refracted into it. |
| 2- STP (shielded twisted pair) | | | | Two modes of propagation of light are possible in |
| STP cable has one extra metal shield covering the | | | | optical fiber such as: multimode and single mode. |
| insulated twisted pair conductors. But this is absent in | | | | Multimode fiber allows multiple beams from a light |
| UTP cables. The most common UTP connector is | | | | source move through the core. In multimode step-index |
| RJ45. | | | | fiber, the core density remains constant from the |
| The unshielded twisted pair cable is classified into | | | | center to the edges. But in multimode graded-index |
| seven categories based on cable quality. Category 1 | | | | fiber, core density gradually decreases from the center |
| of cables is used in telephone lines with data rate | | | | of the core to its edge. Graded-index fiber creates |
| around 0.1 Mbps. Whereas Category 5 used in LANs | | | | less distortion in the signal compare to step-index. |
| having 100 Mbps data rate. | | | | There are two types of connectors for fiber optic |
| Performance of twisted-pair cable is measured by | | | | cables. The SC connector is used for cable TV, and |
| comparing attenuation versus frequency. Attenuation | | | | ST connector used for connecting cable to networking |
| increases with frequency above 100 kHz. | | | | devices. Attenuation in fiber optic cable is very low |
| These cables are used in telephone lines to provide | | | | compare to other two types of cable. It provides very |
| voice and data channels. DSL lines and Local area | | | | high bandwidth and immunity to electromagnetic |
| networks also use twisted pair cables. | | | | interference. Light weight and greater immunity to |
| Coaxial Cable | | | | tapping makes it more preferable cable. |
| Coaxial cable (coax) carries high frequency signals | | | | Fiber optic cable is often used in backbone networks |
| than twisted-pair cables. Coax has a central core | | | | because of its wide bandwidth and cost effectiveness. |
| conductor of solid wire enclosed in an insulator, which | | | | Local area networks such as 100Base-FX network |
| is covered by an outer conductor of metal foil. This | | | | and 100Base-X use this cable. Also it is used by cable |
| outer conductor completes the circuit. Outer conductor | | | | TV companies. |
| is also enclosed in an insulator, and the whole cable is | | | | |