In the research and development of new optical fibre technologies, SDM space division multiplexing has attracted a great deal of attention.There are two main directions for the application of SDM in optical fibres: core division multiplexing (CDM), whereby transmission is carried out through the core of a multi-core optical fibre. Or Mode Division Multiplexing (MDM), which transmits through the propagation modes of a few-mode or multi-mode fibre.
Core Division Multiplexing (CDM) fibre is in principle based on the use of two main schemes.
The first is based on the use of single-core fibre bundles (fibre ribbons), in which parallel single-mode fibres are encapsulated together to form fibre bundles or ribbons that can provide up to hundreds of parallel links.
The second option is based on transmitting data over a single core (single mode per core) embedded in the same fibre, i.e. in an MCF multicore fibre. Each core is treated as a separate single channel.
MDM (Module Division Multiplexing) fibre refers to the transmission of data over different modes of an optical fibre, each of which can be considered as a separate channel.
The two common types of MDM are multimode fibre (MMF) and fractional mode fibre (FMF). The main difference between the two is the number of modes (available channels). Since MMFs can support a large number of modes (tens of modes), intermodal crosstalk and differential mode group delay (DMGD) become significant.
There is also photonic crystal fibre (PCF) which can be said to belong to this type. It is based on the properties of photonic crystals, which confine light through the bandgap effect and transmit it using air holes in its cross-section.PCF is mainly made of materials such as SiO2, As2S3, etc., and air holes are introduced in the area around the core in order to change the contrast in refractive index between the core and the cladding.
CDM fibre can be described as simply the addition of parallel single-mode fibre cores carrying information, embedded in the same cladding (multi-core fibre MCF or single-core fibre bundle).MDM mode division multiplexing is the use of multiple spatial-optical modes in the transmission medium as individual/separate/independent data channels, typically for short-distance interconnected transmission.
Post time: Jun-26-2025