Monomode multicore optical fibre-cable - has core spacing and cladding dimensions designed to give two propagation wavelengths

摘要

Monomode multicore optical fibre has two transmission cores of higher refractive index contained in one cladding of lower refractive index. The differences between the refractive indices of core and cladding and the dimensions and spacings are chosen so that above a certain cut-off wavelength only two orthogonal propagation modes are possible. The modes are of different propagation speeds and there is no cross-coupling between them so if one is used in a fibre the other is prohibited. The multicore design enables one mode in one core and the other in the second core without danger of interraction. A graded index fibre is also available.