Radio Frequency Interference (RFI) is electromagnetic radiation which is emitted by electrical circuits and causes unwanted interference to be induced in other circuits. This causes corruption or loss of data. It is unintentionally produced as a result of spurious emissions and responses, intermodulation products, and the like. It is also known as Electromagnetic Interference (EMI).

Power limit
The Power Limit is the maximum amount of power that can be allowed to flow through the cable before it begins to cause RFI and the cable to heat internally causing the wire to have less conductivity.

Electrical Properties
The Electrical properties of the cable give an overview of how well the cable can conduct electricity.

Effects on transmission
Distance - over long distances the signal fades and needs to be boosted
Diameter of wire - a thicker cable provides less resistance and offer more protection to RFI
Purity of copper - impurities such as Oxygen degrade the purity of copper.
Screening - The protection the wire gets from RFI such as a Semi-rigid cable, which uses a solid copper outer sheath
Length - The longer the wire, the higher the resistance across it
Connections -

Fibre Optics
The main uses of fibre-optics is to backbone ethernet connections or for long distance telecommunication.
It is used for short backbone connections because:-
Immunity to electromagnetic interference, including nuclear electromagnetic pulses
High electrical resistance , making it safe to use near high-voltage equipment or between areas with different earth potentials.
Low weight, important in aircraft.
No sparks, important in flammable or explosive gas environments.
Not electromagnetically radiating, and difficult to tap without disrupting the signal, important in high-security environments.

Wireless
Wireless connections work in 2 main ways.
Peer-to-peer mode - This is where the computers wireless connect directly to each other. For example in a house to connect two computers to one internet connection.
Access Points - Access point are receivers/transmitters strategicaly place around a building to bridge the wireless network the a backbone connection such as fibre-optics.

The advantages of this are that the network can be accessed from anywhere in the building without the need for cables.
The disadvantages are the signal can be interrupted by even a wall between the two connections. Also this technology has droped in price but is still more expencive than cables.