This worksheet presents a demonstration of Maple software's capabilities in the resolution of differential equations governing the propagation of an electromagnetic wave in a step-index optical fiber with a core radius of the order of magnitude of the incident radiation wavelength. It also presents the two and three dimensions graphical functionalities given by Maple which allows : i) To access directly to the eigenvalue equation solutions. ii) To check easily the continuity conditions of the electric E and magnetic H tangent components at the core-cladding boundary. iii) To show in the three dimensions space the E and H vector fields. iv) To show in the fiber transverse plane the light intensity distribution.