Network topologies connect individual devices. Such connections allow the devices to share and exchange information. The most frequently used in the process industries are the star, the bus, and the ring network systems.But we need a transmission media for that lets looks in to the Difference between Twisted Pair,Fiber Optic and Coaxial cables
Twisted Pair (shielded and unshielded)
Twisted pair, as its name implies, consists of a pair of insulated copper wires twisted together to minimize the effects of electromagnetic interference. A cable is a number of such pairs grouped together in a bundle and wrapped in a protective sheath. A shielded pair of wires protects the signal from unwanted noise generated from electromagnetic interference (EMI) and radio frequency interference (RFI). The shield is made of metallized polyester or of a metallic
woven material. EMI is created when the wires are in close proximity to electrical motors and fluorescent lighting. RFI is generated by radio equipment such as walkie-talkies.
Twisted pair is typically used in point-to-point wiring and within a single building. For longer distances, coaxial or fiber optic is used—however, they are more expensive than the twisted pair. Twisted pair can transmit both analog and digital signals and the shielded type has excellent noise immunity. The star, bus, and ring network topologies can all use twisted pair.
Coaxial (and twin axial)
The coaxial cable consists of two conductors, an outer cylinder that can be solid or braided, and an inner conductor that can be solid or stranded. In between the inner conductor and the outer cylinder is a solid dielectric material. The outer cylinder is covered by an insulating jacket. Coaxial cables must be handled carefully during installation. The twin axial is a variation of the coaxial cable. It has two coaxial cables inside a shield and an insulating jacket for
Coaxial cable is a versatile transmission medium as it carries large amounts of data and can be used in point-to-point or multipoint configurations. It is commonly used for the bus network topology (and sometimes for the ring topology). Coaxial cabling is used for analog and digital signaling—known as broadband and baseband respectively. Its noise immunity is better than twisted pair. Coaxial cabling is more expensive than twisted pair but less expensive than fiber optic transmission.
A fiber optic cable consists of a glass or plastic core, a cladding, and a support with an outer protective jacket. The optical fiber transmits a modulated light wave signal by means of internal reflection. Light from a laser or light-emitting diode (LED) source enters the cylindrical core and is propagated. At the other end, the light signal is demodulated into an electronic signal. The laser light source is more efficient and provides greater data rates than the LED. However, the LED light source is less expensive, has a longer life span, and operates over a higher temperature range.
Fiber optic is commonly used in point-to-point links and the signal can travel over very long distances. Since it does not carry electrical signals, it is immune to electrical interference and ground loops. In addition, it can be safely routed through hazardous and explosive environments. Optical fiber links are more expensive than twisted pair or coaxial cables.