Although with applications like FTP and telnet, the interface was difficult and cumbersome. At the same time, the graphical user interface (GUI) was developed and marketed by companies like Xerox, Apple and Microsoft. .
GUI provided a friendly user interface to computers. This required increased information to generate a graphical image. It was only a matter of time before the GUI concept was applied to computer networking thus the birth of today's Internet and hypertext markup language (HTML). And at times the telecommunications network was being used to connect everyone with a phone line to the Internet and transmit this higher bandwidth, bursty payload. This presented a major problem. The telecommunications network with it's optical backbone was not designed to accommodate the relatively young industry of computer networking and even younger Internet, which both had high packet-based bandwidth requirements.
Nowadays, the computer network and the telecommunications network are converging. Although some argue the American communications infrastructure is already overbuilt, new applications requiring higher bandwidth, such as voice and video transmission, facilitate a need for increased capacity. "An industry survey indicated that in 1995, the amount of embedded fiber already in use in the average network was between 70 percent and 80 percent."* (* Source International Engineering Consortium) Materials and, probably more importantly, labor costs force us to consider other alternatives. Two solutions are TDM and WDM.
Solutions to Bandwidth Demand.
TDM.
TDM improves the efficiency of a single fiber by combining many lower-speed transmissions into a single higher-speed transmission using time slicing. Synchronous Optical Network (SONET) used primarily in North America and Synchronous Digital Hierarchy (SDH) used primarily in Europe and Japan are the current standards for synchronous transmission.