A generalized analysis of multiple-clad cylindrical dielectric structures with step-index profiles is presented. This analysis yields unified expressions for fields, dispersion equation and cutoff conditions for weakly guiding optical fibers with step-index but otherwise arbitrary profiles. The formulation focuses on triple-clad fibers, but can accommodate single and double-clad fibers as special limiting cases. Using the generalized solutions, transmission properties of several types of specialty fibers for broadband applications, including dispersion-shifted, dispersion-flattened, and dispersion compensating fibers, are studied. Improved designs for dispersion-shifted and dispersion compensating fibers are achieved. Fiber parameters and material compositions for the improved designs are provided. The proposed design for the dispersion-shifted fiber yields zero second-order as well as third-order dispersion at the 1.55 micrometer wavelength. The dispersion compensating fiber proposed here provides a large negative dispersion of about -400 ps/nm.km at the 1.55 micrometer wavelength for the fundamental mode. Numerical results for dispersion characteristics, cutoff wavelengths, and radial field distributions are provided. / Master of Science