Multiplexing techniques
Optical communications: introduction and performance assessment

There are four main approaches to multiplexing, i.e. building up a very-high-speed data stream (called a multiplex) from several lower-speed data streams, known as tributaries. The first three are used commercially, while the fourth is still only a subject of study in research laboratories. Naturally, the amount of information transmitted increases when several multiplexing techniques are used simultaneously. The capacity of a system is defined as the total data rate it is capable of transmitting in a single optical fiber.