Optical fiber with high pressure resistance and low bend loss

The invention provides an optical fiber with high pressure resistance and low bend loss. The optical fiber comprises a core layer, an inner cladding layer, a sunken layer and an outer cladding layer,wherein SiO2 and GeO2 are doped in the core layer; the radius of the core layer is formed by the outward extending distance R1 of the center of the core layer; the refractive index of the core layer is n1; the width of the inner cladding layer is the outward extending distance R2-R1 at the edge R1 of the core layer; the section of the inner cladding layer is formed by doping a small amount of Ge and F; the refractive index of the inner cladding layer is n2; the sunken layer is formed by deeply doping F outwards from the outer edge of the inner cladding layer; the width and the refractive indexof the sunken layer are R3-R2 and n3 respectively; the thickness and the refractive index of the outer cladding are Rc-R3 and nc respectively; and the refractive index profile of the optical fiber isdistributed in a stepped m