Coupling of Optical Fibers and Scattering in Fibers*

Abstract

The phenomena of optical coupling of parallel fibers and scattering of light from a fiber due to rough walls are considered from a mode point of view. With the use of a Green’s function, the problems are cast in the form of integral equations. Coupled ordinary differential equations are obtained which are used to study the coupling of modes in parallel fibers, including the case when the diameters are slowly-varying functions of the axial distance. The analysis of the problem of propagation in an optical fiber having rough walls shows that the various modes in a fiber will couple and that the roughness will cause radiation through the walls of the fiber. The character of the radiation may be determined if the spatial spectral density of the surface roughness is known.