Leaky-ray theory of optical waveguides of circular cross section
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- Snyder, A.W. Appl. Phys. (1974) 4: 273. doi:10.1007/BF00928381
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The methods and most important results required to study light transmission within optical waveguides are given. Only those techniques that are simple and that lead to concise analytic expressions are presented. Special emphasis is given to the importance of leaky modes on the fiber of circular cross section and to the use of rays for the analysis of multimode fibers. It is shown thatunlike the slab, the radiation field within the circular fiber propagates for enormous distances. Both coherent and incoherent illumination are treated.Radiation loss and mode conversion due to scattering from irregularities are found by a method much simpler than coupled mode theory. A generalized Fresnel's law is presented to account for radiation loss due to boundary curvature. This loss is shown to be caused by electromagnetic tunnelling.