<p>In an optical fiber 10 composed of a core region 1 and a cladding region 2 surrounding the core region 1 and having a plurality of regions made of sub mediums 4 having refractive indices different from a refractive index of a main medium 3 disposed in a main medium 3 constituting this cladding region2, these regions made of the sub mediums 4 are arranged in one given or a plurality of a given circular annular regions 21 to 2m and the centers of the regions made of the sub mediums 4 in respective circular annular regions 21 to 2m are arranged on the same circumference centered at the center of the core. <IMAGE></p>
