in some applications, we need a Laser beam to form a special
pattern. For example, we need a ring pattern laser beam for
correcting Cornea in Ophthalmology experiment. In this paper ie
introduce a method to create a ring pattern by use of a muitimode
fiber. The arrangement is very simple that we create different
diameter ring pattern by adjusting the fiber angle with
corresponding to incident light rays or by changing different
distance that is away from the output end of the fiber.