space division multiplexing (SDM)
Space Division Multiplexing (SDM), space multiplexing, is the aggregation of physical transmission media in a cable, fiber, frequency band or broadcast area.
Inwire-based space division multiplexing, entire transmission media are connected and disconnected: Instead of one cable, several are used; instead of one optical fiber, transmission is via several parallel ones, as in Ribbon Fiber, via Microstructured Optical Fiber( MOF) such as Multimode Fiber( MMF) or Multicore Fiber( MCF). These can be individual separate channels or overlapping channels.
The switching on and off of transmission media, for example, via coupling fields or crossbar distributors is a relatively coarse form for the expansion of transmission capacities; much finer ones are scaling and bandwidth management.
Practical applications of wireline space multiplexing include bundling, parallel operation of multiple lanes in Gigabit Ethernet and 10-Gigabit Ethernet, and space switching of optical fibers in optical networks, where it is implemented using the electromechanical components of microsystems technology( MST). Optical space division multiplexing ( OSDM) is also under discussion for 100- gigabit Ethernet. Here, several parallel optical fibers of a loose tube are used for parallel transmission.
In wireless space division multiplexing, additional radio links are added to an existing radio link. The arrangement of radio cells is also a type of space multiplex, since each individual radio cell illuminates a regional area with a radio frequency. In this context, reference should also be made to the MIMO method, Multiple Input Multiple Output (MIMO), in which several radio links, Spatial Streams( SS), are operated in a spatial multiplex.