الفهرس 
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Abstract
Fiber optics communication system is a medium for carrying information from one point to another in the form of light. Unlike the copper form of transmission, fiber optics is not electrical in nature. A basic fiber optic system consists of a transmitting device that converts an electrical signal into a light signal, an optical fiber cable that carries the light, and a receiver that accepts the light signal and converts it back into an electrical signal. so, there is many advantages for using optical fibers in optical communication systems. Most of the optical communication systems consist of many devices including multiplexer-demultiplexers, power couplers, filters and polarization splitters. The photonic crystal technology has the extreme ability to control the flow of light in a fashion way not possible with the conventional optical fiber technology. In the present thesis, two designs of photonic crystal fibers (PCFs) polarization filter are suggested and simulated using COMSOL multiphysics software package. A square lattice PCF polarization filter and a modified D-shaped PCF polarization filter design are proposed and analyzed, where different types of propagation characteristics are determined. The cross talk (CT) and the propagation characteristics such as effective refractive index for the x- and y-polarized modes, and confinement losses of these two types of PCF polarization filter are calculated. These characteristics are analyzed when varying the geometrical parameters of these two types of structures and when changing the operating wavelength. A comparative analysis between these two suggested PCF polarization filter designs and the previous verified work is also shown in the presented thesis. For the first design, a compact surface plasmon PCF polarization filter is proposed and analyzed at the two communication windows of 1310 and 1490 nm, respectively. The x-polarized mode can be filtered out at wavelength of 1310 nm, while the y-polarized mode can be excluded at λ = 1490 nm. Therefore, the reported PCF design can be used as x-polarized or y-polarized filters using the same design. The effects of the geometrical parameters of the PCF on the performances of the polarization filter are studied by the full vectorial finite-element method (FVFEM). The numerical simulations reveal that the suggested polarization filter with a compact length of 150 μm can achieve good CT of −78 and −80.7 dB at the communication wavelengths of 1310 and 1490 nm, respectively. Further, bandwidths (BW) of 97 nm and 580 nm can be obtained around wavelengths of 1310 and 1490 nm, respectively, where the cross talk is better than −20 dB. Therefore, the reported design has advantages in terms of low cross talk, large BW, short device length, and multifunctionality.