The need for optical fibers has emerged for their ability to transmit information with less attenuation over long distances. This work studies four optical fibers with core radii from 1 µm to 4.75 µm in steps of 1.25 µm and a numerical aperture of 0.17. furthermore, The mode properties were calculated at a wavelength of 633 nm by using RP Fiber Calculator (free version 2022). Also, the effect of increasing the core radius on the studied properties has been studied. Multimode fibers can be obtained when the radius of the fiber core is large compared with the fiber's operating wavelength, which is less than the cutoff wavelength of the mode. Moreover, single-mode fiber is obtained. It has been concluded that all the calculated properties increase with increasing core radius, and More than half of the power is contained in the core. Finally, Intensity profiles of all modes were illustrated.