In this thesis, the polarization and phase properties of the side-polished optical fiber (SPOF) are aimed to characterize. The Linearly Polarized (LP) modes of standard optical fibers have been affected by the side-polished geometry which breaking symmetry. At the side-polished area guided modes couple to non-symmetric modes and phase shift occurs due to the birefringent property of the SPOF. That kind of structure has an excellent usage potential as a portable optical sensor or optical fiber communication device. It was primarily concentrated on the LP modes of the standard optical fiber. LP mode field solutions extracted from Maxwell Equations were calculated with MATLAB, and mode intensity distributions were constructed accordingly. The calculated intensity distributions were utilized for figuring out the mode content of the outputs of the twomode experiment. The recorded CCD Camera images were matched with the calculated intensity distributions, and then the best-matched LP mode combination was selected as output mode content. In the single-mode experiment at the side-polished area, quasi-degenerate fundamental modes occur. According to the state of polarization of the modes, they suffer attenuation and phase shift in different levels. Therefore, after the side-polished area, degenerate fundamental modes propagate together with a particular phase difference. This situation composes elliptical polarization at the output. Various modal polarization rotation and phase shifts were observed, and then polarization ellipses were obtained with MATLAB. The resultant ellipses demonstrate that the effect of SPOF on guided modes varies with the angle of input polarization.