Optical networks comprise optical transmitters and receivers, fiber optic cables, optical network switches, and other optical components. Optical and electronic networks can take several different forms. Point-to-point networks make permanent connections among two or more points so any pair of nodes can communicate with each other; point to multipoint networks broadcast the same signals simultaneously to many different nodes; switched networks like the telephone system include switches that make temporary connections among pairs of nodes. The basic building blocks of these networks are fiber-optic cables-the the so-called “pipes”-which carry signals from node to node, with switches directing them to their destination.

 IP telephony (Internet Protocol telephony)

IP telephony (Internet Protocol telephony) is a general term for the technologies that use the Internet Protocol’s packet-switched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). Using the Internet, calls travel as packets of data on shared lines, avoiding the tolls of the PSTN. The challenge in IP telephony is to deliver the voice, fax, or video packets in a dependable flow to the user. Much of IP telephony focuses on that challenge.

IP telephony is an important part of the convergence of computers, telephones, and television into a single integrated information environment. Also see another general term, computer-telephony integration (CTI), which describes technologies for using computers to manage telephone calls.