A Multicore Fiber(MCF) is an optical fiber that has multiple microfine fiber cores.
The multicore fiber belongs to the group of microstructure optical fibers( MOF) and can simultaneously transmit different information via the individual microfine fibers. In this case, the transmission bandwidth of the individual microfine fiber cores corresponds to that of single- mode fibers. This means that the data rate in space multiplex is many times higher than that of monomode fibers.
Multicore fiber can consist of a few or many individual core fibers embedded in the multicore fiber. The refractive index of the cladding glass is higher than that of the fiber core, which causes the light beam to be reflected back into the fiber. There is also a version with hollow holes that have a slightly larger diameter than the core fiber. These designs are called Hollow-Core Fiber( HCF).