Bound rays of fibers

Abstract

In Chapter 1 we established the basic concepts for the ray analysis of planar waveguides. Here we extend the analysis to optical fibers, which are used for high-capacity communication over long distances. As far as ray tracing is concerned, the only difference between fibers and planar waveguides is the introduction of the third dimension. Thus, although the ray concepts are the same as in Chapter 1, the analysis and resulting expressions are generally more complicated because of the fiber geometry. Nevertheless, one of the important results of this chapter shows that the ray transit times for step and clad power-law profile fibers of both circular and noncircular cross-sections are identical to those of the corresponding planar waveguides. If this remarkable simplification is acceptable without proof, then pulse spreading in such fibers can be studied directly by proceeding to Chapter 3 and omitting this chapter at a first reading.