الفهرس 
Introduction and Previous Work of Optical Fibres characterizationOnly 14 pages are availabe for public view
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Abstract
In this study we deal with the characterization of bent optical fibres and graded index optical fibres. Here we use the automatic Fizeau fringe analysis method to calculate the optical parameters of the used fibres with high accuracy. Also, digital holographic phase shifting microscopic interferomtery is used to characterize the graded and bent optical fibres with suitable accuracy. The calculations of refractive index profiles of fibres are performed using the multilayer model and the slabs model. The mechanical bending of the optical fibres leads to the appearance of birefringence. The two states of polarization of the incident beam are used. where, the first polarization state is selected to be parallel to the fibre optical axis. The second polarization state is selected to be perpendicular to the fibre optical axis. The refractive index component in the parallel direction n║ is affected by the bending in contrast to the perpendicular refractive index component n┴, which is not affected. We apply a new mathematical model to calculate the refractive index of bent optical fibres. This model is named as the slabs model. The slabs model is based on the consideration of varying refraction of the incident beam across the bent optical fibre. Also, many cases of the refraction across one slab, two, and three or multi-slabs are described. The slabs model is verified by simulation. Also, it is successfully used to calculate the refractive index profiles of bent optical fibres at different bending radii. The automatic Fizeau fringe analysis technique in aid of the slabs model is used to calculate the refractive index distribution across the bent optical fibres. The accuracy of the calculation is increased due to the use of the slabs model which is based on refraction considerations. In addition, the birefringence profiles of the bent optical fibre are calculated at different bending radii. The numerical aperture and the acceptance angle are calculated across the bent optical fibre at different bending radii. The recommended lowest bending radius to avoid the large loss rate of the propagated waves is calculated. Also, the dispersions and structural parameters of the bent optical fibre at different bending radii are measured across the bent optical fibres. All these calculated optical, dispersive and structural parameters are describing the bending effect on the optical fibre material. More information about the atomic and electronic perturbations may clarify this behaviour. The graded index optical fibres and bent optical fibres are characterized using digital holographic microscopic phase shifting interferometry aided by the multilayer and slabs models. The holographic arrangement is a modified two-beam Mach-Zehnder interferometer. Five Fresnel off-axis digital phase shifted holograms are used to calculate the complex field in the hologram plane instead of the original real hologram. So that, the problems of zero diffraction order and twin image are successfully avoided. Also, the resolution of the reconstructed wavefields is the same as that of the recorded holograms. This helps us to calculate the magnification of the optical system in an accurate and easy way. In addition, the optical focusing of the reconstructed fields can be achieved numerically. Now, we have the ability to obtain the optical focusing of the reconstructed field along the sample depth. A method to extract the optical phase difference due to the graded index fibre at every point in the reconstructed phase map is presented. The combination of phase shifting digital holographic microscopic interferometry with the multilayer model is used to calculate the optical parameters of graded index optical fibres. The measured parameters are compared with the calculated parameters measured by two-beam interferometry. The performance and the accuracy of using phase shifting digital holographic microscopic interferometry to characterize optical fibres are proven. The bent optical fibre is studied by phase shifting digital holographic microscopic interferometry. The phase shifting algorithm with four recording is used to calculate the complex wave field instead of the originally recorded off-axis Fresnel holograms. The phase map of the reconstructed field is enhanced and filtered. The optical phase differences across the bent optical fibre at every pixel point along the bent optical fibre are calculated. Then, the optical phase difference due to the bent optical fibre using different tilting angles for the carrier fringes as well as curved carrier fringes is verified. The refractive index profiles of bent optical fibres at different bending radii are presented using phase shifting digital holographic microscopic interferometry.