Mode group multiplexing over graded-index multimode fiber

Data transmission over multi-mode fibers (MMF) has the potential to increase considerably the capacity limit of singlemode fibers (SMF) by exploiting the spatial dimension. Spatial multiplex using standard graded-index multimode fibers (GI-MMF) in combination with OOK modulation and direct detection might be advantageous for short haul transmission systems. The application of principal mode groups provides the possibility to eliminate the need for multiple-input multiple-output (MIMO) processing, especially if a fiber supporting a large number of modes is used for the transmission. Spatial multiplex using principal mode groups as individual transmission channels has been experimentally investigated at the example of a data transmission over a 2 km long OM4 graded-index multi-mode fiber. Eight principal mode groups have been identified being suitable as spatially separated transmission channels for 10 Gbit/s data at a wavelength of 1550 nm.