Specialty Optical Fibers Handbook

12.4 CHIRAL INTERMEDIATE-PERIOD GRATING

12.4.1 Symmetry of CIPG Structures

We next consider the differences between propagation in a planar and in a fiber

geometry. Because the sample is no longer uniform in the transverse direction,

core modes may be scattered into modes with propagation vector pointing away

from the fiber axis when the difference between the propagation constant of the

core mode and the scattered wave is compensated by the grating constant associated

with the periodic structure. In FBGs, the forward and backwards propagating core

modes are coupled via the grating constant, which is 2p=a, where a is the grating

period. In chiral fibers, core modes are similarly coupled via the grating condition

above. In single-helix chiral gratings ...