To identify the most common medium of communication among satellite signals, cables, and optical fibre, we can assess the performance and usage of each type.
1. The first medium to consider is satellite signals. While satellites are instrumental in long-range communication such as broadcast television and weather monitoring, they do have limitations such as lower speeds compared to other communication mediums, susceptibility to environmental disruptions, and higher latency. Therefore, while satellite signals are extensively utilized, they may not be the most common medium.
2. The second medium is cables. Cable communication, such as those used for traditional landline phones and some types of internet connections, is reliable and widespread. However, the signal strength in cable communication decreases over long distances and requires signal amplifiers for long-range communication. Also, compared to more advanced technologies, data transmission rates over cables may be slower.
3. The final medium is optical fibre. Optical fibre communication employs light signals to transmit data, resulting in extremely high speeds and data transmission capacities. Since fibre optic cables are resistant to electromagnetic interference and offer higher security, they are increasingly being employed in various sectors including telecommunications, cable television services, and internet connections.
Taking these analyses into account, we currently find that optical fibre is the most common medium amongst the three. It is prevalent due to its superior speed, data handling capacity, and resistance to interference. Please note that the most common medium could vary depending on the specific use-case, geographical conditions, and advancements in technology. For now, optical fibre holds the upper hand.