<title>Pulse Propagation And Dispersion In Arbitrary Optical Fibers</title>

Abstract

We have developed a general treatment of light propagation and dispersion in arbitrary refractive index profile optical fibers. The method is based on the accurate numerical solution of the scalar wave equation by a combination of operator splitting and Fourier transform techniques. The Fourier representation of the propagating beam allows a dual description of the electric field in both (x,y) and transverse wavenumber space. This dual description affords a precise characterization of such propagation properties as spatial beam confinement, angular confinement (numerical aperture) and losses, all as a function of propagation distance z. In addition, Fourier transformation of the field autocorrelation function with respect to z yields the complete power spectrum containing trapped, leaky, and radiation modes. The trapped modes appear as distinct spectral lines whose position (modal wavenumber) and amplitude (modal weight) are the ingredients needed to characterize the dispersion of the light pulse. The numerical tools developed allow a general characterization of realistic refractive index profiles including, e.g., losses and fiber bends as appropriate. The method has been applied to a fiber having a square law refractive index profile with a central dip. The cladding was surrounded with a strong absorber so that leaky modes would be rapidly attenuated. The central dip is found to profoundly alter the mode spectrum, principally by removing some of the degeneracy of the square law modes. In addition, the spread of modal group delays is increased by nearly two orders of magnitude, leading to much less favorable dispersive properties.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.