Optical fiber provides cheaper bandwidth for long distance communication
Bell Labs scientist Claude E. Shannon published A Mathematical Theory of Communication in 1948. This landmark publication was to set the mathematical models used to describe communication systems called information theory. Information theory enables us to evaluate the capacity of a communication channel according to its bandwidth and signal-to-noise ratio.
At the time of publication, telecommunication systems were predominantly based on analog electronic circuit design. The introduction of mass-produced digital integrated circuits has enabled telecom engineers to take full advantage of information theory. From the demands of telecom circuitry, a whole specialist area of integrated circuit design has emerged called digital signal processing.
Possible imperfections in a communication channel are: shot noise, thermal noise, latency, non-linear channel transfer function, sudden signal drops, bandwidth limitations, signal reflections (echos). More recent telecommunications systems take advantage of some of these imperfections to actually improve the quality of the channel.
Modern telecommunication systems make extensive use of time synchronization. There is a link between the development of telecommunications and very fine-grained (microsecond) time-keeping technology. Until the recent rise of the use of IP Telephony, most modern, wide-area telecommunications systems were synchronised to atomic clocks, or to secondary clocks synchronised to atomic time.