Optical networking

Optical networking is a means of communication that uses signals encoded onto light to transmit information among various nodes of a telecommunications network. They operate from the limited range of a local-area network (LAN) or over a wide-area network (WAN), which can cross metropolitan and regional areas all the way to national, international and transoceanic distances. It is a form of optical communication that relies on optical amplifiers, lasers or LEDs and wave division multiplexing (WDM) to transmit large quantities of data, generally across fiber-optic cables. Because it is capable of achieving extremely high bandwidth, it is an enabling technology for today’s Internet and the communication networks that transmit the vast majority of all human and machine-to-machine information.

Components of an optical networking system include: • Fiber. Multi-mode or single-mode. • Laser or LED light source. • Multiplexer/demultiplexer, also called mux/demux, filter, or prism. These can include Optical Add/Drop Multiplexer (OADM) and Reconfigurable Optical Add/Drop Multiplexer (ROADM). • Optical switch, to direct light between ports without an optical-electrical-optical conversion • Optical splitter, to send a signal down different fiber paths. • Circulator, to tie in other components, such as an OADM. • Optical amplifier.

At its inception, the telecommunications network relied on copper to carry information. But the bandwidth of copper is limited by its physical characteristics—as the frequency of the signal increases to carry more data, more of the signal’s energy is lost as heat. Additionally, electrical signals can interfere with each other when the wires are spaced too close together, a problem known as crosstalk. In 1940, the first communication system relied on coaxial cable that operated at 3 MHz and could carry 300 telephone conversations or one television channel. By 1975, the most advanced coaxial system had a bit rate of 274 Mbit/s, but such high-frequency systems require a repeater approximately every kilometer to strengthen the signal, making such a network expensive to operate.

...
Wikipedia