A dispersion optimized fiber having higher spot area comprising a center
core region, a cladding region, a ring core region and an outer glass
region is provided, wherein the cladding is provided onto the outer
periphery of the center core, and the ring core is provided onto the
outer periphery of the cladding, and the outer glass region surrounds the
ring core region, and the center core and the ring core have refractive
indices higher than the outer glass region and the cladding region has
lower refractive index than the outer glass region, and the refractive
indices are constrained by the equation
n.sub.1>n.sub.3>n.sub.4>n.sub.2. In accordance with the
preferred embodiment, the cladding region is divided into two
regions--inner cladding region and an outer cladding with the ring core
disposed therebetween, wherein the inner cladding is provided onto the
outer periphery of the center core, and the ring core is provided between
the inner cladding and the outer cladding is provided onto the outer
periphery of the ring core, and the outer glass region surrounds the
outer cladding, and the refractive indices are constrained by the
equation: n.sub.1>n.sub.3>n.sub.5>n.sub.2=n.sub.4.