The transverse interference pattern from a fusion-spliced optical fiber is obtained by illuminating the fiber with a laser sheet of light. The buckling on the fiber material in one direction of the spliced point is clear inside the transverse interference pattern. The buckling height ranges from 1 to 10 microns in a waveguide of a 50-micron core and 125 micron clad diameters. The refractive index profile inside the fiber core is calculated using a new method showing the change in the refractive index due to fusion splicing of the fiber. The refractive index profile is calculated by means of the transverse interference patterns obtained at different illumination directions. A CCD camera is used to record the transverse interference pattern from the fusion-spliced optical fiber. In order to calculate the visibility of the obtained fringe patterns and the deflection angle of light through the fiber (displaying the change in the refractive index) it is necessary to measure the fringe maximum and minimum intensities using a special software package.