Simulation of energy absorption in waveguides with structured impurities

A theory of light propagation in fibers has been devised in sufficient details now but we can´t say the same thing about fibers with statistical inhomogeneity. The presence of impurities and microstructure disturbance in the core and cladding materials may be responsible for propagation losses. Here we shall consider the influence of nonhomogeneity of cladding material on linearly-polarized LP₀₁-mode absorption in weakly guiding single-mode two-layered. The following model of fiber is proposed: a core with refraction index n1=1.45 - 1.445 (including dispersion effect for free wavelength λ=1 16 μm) and radius a=8 μm and microvoids of radius R and concentration no embedded into cladding material. These small spheres have a thin film (size of d so that d/R≈0.01) with hydroxyl (OH-groups). It is known that core and cladding material in modern technology are formed by precipitation from vapour. We consider here the scattering at nonhomogeneities is only into cladding material because a core is formed usually at higher temperature that retard the implantation of hydroxyl. The one-oscillator model with damping have been used for calculation of film dielectric constant. We applied the relation of Maxwell-Garnett-type for calculation of effective dielectric permeability of slightly dispersed cladding material. After series of intricate transformations one may obtain the expression for imaginary part of cladding dielectric function that characterizes the absorption effect in the system. It is known that the parameters of linear-polarized LP₀₁-mode propagation into regular two-layer fibers may be obtained from specific characteristic equation. The approximation of perturbation theory is also used.