Optical ray movement inside dielectric sphere

The paper presents results of numerical investigations of electromagnetic ( optical) ray propagation inside a sphere, made of optically uniaxial crysta l. The types of caustics formed by the ray trajectory inside the sphere are cleared up. It has been demonstrated the difference between the types of c austics formed by the extraordinary ray trajectory inside the sphere made o f optically positive and negative crystals. Results are discussed on the ba sis of one-to-one mapping of 2D billiard problem inside isotropic region bo unded by ellipse onto anisotropic one.