Long-distance laser energy transmission optical fiber

The invention discloses a long-distance laser energy transmission optical fiber. A fiber core is made of pure quartz, a cladding is made of fluorine doped quartz, and refractive index distribution of the cladding satisfies that refractive index of a corresponding point, in a distance r from the center of the fiber core, of the cladding is accordant with the equation: n(r)=n1+(n2-n1){(r-a1)/(a2-a1)} , wherein n1 refers to the refractive index of the outer edge of the fiber core, n2 refers to the refractive index of the outer edge of the cladding, a1 refers to the radius of the fiber core, and a2 refers to the radius of the cladding. The refractive index of the cladding is gradually reduced outwards from the center of the optical fiber, mode field diameter of a basic mode can be effectively increased, and optical coupling and reduction of laser damages to the optical fiber are facilitated; by introduction of a gradually-changed refractive index distribution structure to the cladding, energy distribution of low-order modes in highly doped regions is reduced, and accordingly transmission loss is reduced; due to the fact that difference in refractive indexes of the outer edge of the cladding and the fiber core is still high and even can be higher, large numerical aperture of the optical fiber is guaranteed to further guarantee that laser can be effectively inputted and coupled into the optical fiber.