الفهرس 
General IntroductionOnly 14 pages are availabe for public view
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Abstract
The electromagnetic tunneling loss of leaky modes is calculated in graded index biquadrate multimode fibers. The factors affecting the attenuation are investigated for the three dominant modes Showing less attenuation in fibers with greater radii. The obtained results show also that the propagation of the fundamental mode (LPol) is accompanied by a large attenuation in ’he other modes and so, it is suitable for mode filtering operation. This type of fiber reduces bending loss and well confines optical power in clad. Due to this feature, the fiber is suitable for nonlinear wave propagation. A W-fiber doped with erbium is. used as an amplifier for optical pulses with different duration The described model of Maxwell-Bloch for the wave equation of the carrier envelope and the two energy level system is used to study the evolution of solitons in this fiber amplifier. We adapted the Fourier-split method to include the polarization-induced term representing the effect of doping atoms on the propagating optical field. This adapted method is used. to solve the system of Maxwell-Bloch equations saving computation time compared to any finite difference method Third order dispersion coefficient, self steepening and the effect of delayed nonlinear response during pulse propagation are considered. We studied also the effect of modulation instability of the medium of anomalous dispersion at λ = 1.55 µm on amplification of optical pulses in the fiber. The results show that amplification is affected by the doping level, pulse duration, relaxation time of the induced dipole polarization, atomic dipole moment of the doping atom, dispersion and nonlinearity of the fiber material rather than the fiber core index profile. The obtained system can be used as an optical repeater within the optical communication system, with a recommended length not more than the dispersion length.