Photonic crystal fiber

The invention discloses a photonic crystal fiber, which is characterized by comprising a core layer, a cladding layer and a coating layer from the inside to the outside, wherein the cross section of the fiber is circular, the core layer, the cladding layer and the coating layer are concentric, the core layer is arranged at the innermost layer of the fiber, the center of the cross section of the core layer is a circular hole, a plurality of semicircular air holes are uniformly formed in the cladding layer, the cladding layer comprises five cladding layer rings, each of the cladding layer ring is formed by sequentially connecting the semicircular air holes of the same size, the sizes of the semicircular air holes in the cladding layer rings are progressively increased in sequence from the inner ring to the outer ring, convex surfaces of the semicircular air holes in every two adjacent rows of cladding layer rings, the coating layer is arranged at the outermost layer, the core layer and the cladding layer are ma