Networks and Communications
Characteristics of Wired Transmission Media
Twisted Pair (Unshielded and Shielded)
Twisted pair cables are a type of cable construction used in networking, mostly associated with ethernet cables. Twisted pair cables consist of eight wires that are twisted into 4 sets. The wires are twisted into pairs to mitigate electromagnetic fields created when current is run through wires. These fields can create electromagnetic interference between twisted pairs, which can result in lost data in transmission. Twisted pair cables have a range of approx. 100m before data loss occurs, requiring a repeater to reamplify the signal. Twisted pair cables can be unshielded or shielded: • Unshielded Twisted Pair (UTP) cables are prone to external electromagnetic interference by surrounding high current carrying conductors. This is due to its lack of shielding. • Shielded Twisted Pair (STP) cables are less prone to external electromagnetic interference due to its shielding, designed to reflect or absorb the interference, thus not affecting data transmission. Shielding constructions include copper braid, copper mesh, aluminium mesh, etc
Fibre optic cables are cables that consist of flexible optical fibre/s fibres made of glass that are designed for light signals to travel through in order to transmit data. There are two types of fibre optic cable; single-mode and multi-mode. • Single-mode fibre optic is characterised by a small diameter core that only allows a light signal to propagate. This design allows for data to transmit faster and a further distance (approx. 20km) but carries less bandwidth than multi-mode fibre. • Multi-mode fibre optic is characterised by a larger diameter core that allows multiple light signals to propagate concurrently. Its larger size allows for a higher bandwidth but with a reduced transmission distance (approx. 2.5-5km).