Spatial multiplexers and demultiplexers for mode group division multiplex

Spatial multiplexer and demultiplexer are beneath the multimode fiber the key components for a transmission system using mode or mode group division multiplexing (MDM or MGDM). The spatial multiplexer converts the LP₀₁ modes of the incoming singlemode fibers into the desired modes or mode groups of the multimode fiber. The spatial demultiplexer performs the inverse operation. This paper gives an overview on different kinds of spatial multiplexers/demultiplexers and introduces a first experimental result of a 4:1 spatial multiplexer in combination with a standard OM4 graded-index multimode fiber.