Specialty Optical Fibers Handbook

are, however, generally not single mode but support a limited number of propa-

gating modes of visible wavelengths and are not covered in this chapter (see

Chapter 23 of this handbook for more information).

Multi-core fibers can be divided into two categories. In the first category, the

fibers are designed for a controlled coupling of the guided modes between

the cores, whereas for the second category, the design is such that the modes

in the different cores are practically decoupled.

6.4.1 Coupled Cores

The coupling of energy between the modes guided in the various cores in multi-

waveguide structures, including fibers, has been extensively analyzed ...