Optical fiber

The invention provides an optical fiber. The optical fiber comprises an inner core layer, an outer core layer, a middle cladding layer, an inner cladding layer, a sunken cladding layer and an outer cladding layer which are sequentially arranged from inside to outside. The refractive indexes of the inner core layer, the outer core layer, the middle cladding layer, the inner cladding layer and the sunken cladding layer are different, and the refractive index of the sunken cladding layer is smaller than that of any one of the inner core layer, the outer core layer, the middle cladding layer and the inner cladding layer. The radius of the inner core layer is 1.40 [mu] m to 4.80 [mu] m, and the relative refractive index difference between the inner core layer and the outer cladding layer is 0.08% to 0.24%; the radius of the outer core layer is 4.58 [mu] m-7. 50 [mu] m, and the relative refractive index difference between the outer core layer and the outer cladding layer is 0.16%-0.48%; the radius of the middle cladding is 5.50 [mu] m to 9.00 [mu] m, and the relative refractive index difference between the middle cladding and the outer cladding is-0.08% to 0.20%; the radius of the inner cladding layer is 7.57 [mu] m to 10.00 [mu] m; the radius of the sunken cladding layer is 9.21 [mu] m to 18.00 [mu] m, and the relative refractive index difference between the sunken cladding layer and the outer cladding layer is-1.00% to-0.02%. The radius and the refractive index of each layer in the optical fiber are reasonably designed, so that the effective mode field area of the optical fiber is increased, the cut-off wavelength is reduced, and the performance of the optical fiber is improved.