Dispersion shifted fiber having low dispersion slope

Dispersion shifted fiber having low dispersion a slope comprising a centre core, two claddings, a ring core and the outer glass region, wherein the first cladding is provided onto the outer periphery of the centre core, the second cladding is provided onto outer periphery of the first cladding and the ring core is provided onto outer periphery of the second cladding, and the outer glass region surrounds the ring core, and the centre core and the ring core have higher refractive indices, and the claddings have lower refractive indices than the outer glass region, and the refractive indices are constrained by the equation n 1 >n 4 >n 5 >n 2 >n 3 . In accordance with preferred embodiment the fibre comprises of a centre core, two claddings, two ring cores, and an outer glass region, wherein the first cladding is provided onto the outer periphery of the centre core, the second cladding 3 is provided onto the outer periphery of the first cladding, the first ring core is provided onto the outer periphery of the second cladding, the second ring core 5 is provided onto the outer periphery of the first ring core and the outer glass region surrounds the second ring core, and the refractive indices are constrained by the equation n 1 >n 4 >n 5 >n 2 >n 3 .