Fiber-optic waveguides with rectangular cores

A theoretical and experimental study was made of the dispersive properties of two-layer waveguides with a rectangular core, which were compared with the corresponding properties of circular waveguides. The method of effective permittivities was used to calculate the dispersion curves, number of propagating modes, and their group delays for rectangular step and graded-index guides. The vapor reaction method was employed in the fabrication of a rectangular multimode waveguide with the following parameters: pulse dispersion ~4 nsec/km, losses ~7 dB/km, numerical aperture ~0.17.