A technique for computation of propagation characteristics of optical fiber structures

The author presents a powerful technique to treat the problem of wave propagation along weakly guiding optical waveguides. The technique is based on the numerical solution of the scalar wave equation by a forward-marching fast Fourier transform method (SW-FFT). This solution yields the spatial configuration of the fields as well as its modal characteristics in and around the guiding structure. The technique is applicable to dielectric waveguides with arbitrary shape and three-dimensional index variations as long as their weakly guiding character is preserved. This technique is applied to several optical waveguides such as step-index circular fiber, graded-index circular fiber, elliptical, and rectangular dielectric waveguides. The computed dispersion characteristics of these structures are then compared with solutions obtained by using other known techniques, and an excellent agreement is established. It is shown that the scalar wave solutions are extremely accurate for all practical cases where the core refractive index differs from the cladding index by a few percent.<
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