Uses usually in bus topology and Ethernet networks.



Thicknet – (yellow Ethernet) 13 mm, yellow color, harder to work because has thicker copper core. Can be used as a backbone for small thinnet LANs. More expansive than thinnet, but can be safely installed outside. Uses special N- connectors. Can transmit signal to approximately to 500 m. Twisted cable : A basic twisted-pair cable consists of two strands of copper wire twisted together. This twisting reduces the sensitivity of the cable to EMI and controls the tendency of the wires in the pair to cause EMI in each other.



shielded twisted pair (STP) -13 mm diameter, consists of one or more twisted pairs of cables enclosed in a foil wrap and woven copper shielding. The shield in STP cable results in good EMI characteristics for copper cable. Theoretical capacity is 500 Mbps but the most common rate is 16 Mbps. Limit of cable runs to few hundreds meters but 100 m is quite common.

unshielded twisted pair (UTP) - doesn’t incorporate a braided shield into its structure. Used in telephone lines. offers an excellent balance of cost and performance characteristics, easy to install, divided to five perfomance categories. Common bandwith now days is 100 Mbps, and data can be transfered to few hundred metres but usually used 100 m. Used connectors are RJ -45. Fiber optic : gets name because uses as a central conductor – fiber designed to transmit light signals with little loss. The fiber is coated with a cladding or a gel that reflects signals back into the fiber to reduce signal loss. Cable consists of two strands separately enclosed in plastic sheaths. One strand sends and the other receives.In fiber optic transmission we are not using electrons to send signal but we are using photons. Photons travel thru fiber strands and reflecting from strand’s surface. Strand is hollow so there is no resistance for photon to travels so that bandwith for fiber transmission is very high as 200 Gbs for a long distances if light is not leaking from strands and is good refraction of light.

The main disadvantage is that we must have a components to transfer electrical signal to light on both ends of cable. This makes fiber optic transmission very expensive. As light source is used Laser or LEDs. Figure 5.1



Lasers: A laser is a light source that

produces an especially pure light that

is monochromatic (one color) and

coherent (all waves are parallel). The

most commonly used source of laser

light in LAN devices is called an injection

laser diode (ILD).