A low-attenuation single-mode fiber

The present invention relates to a low-attenuation single-mode optical fiber comprising a core and a cladding layer, wherein a first inner cladding layer are sequentially coated and the second inner cladding outside the core layer, the core layer of the radius R1 is 3.5μm ~ 5μm, the relative refractive index difference? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? From 0.2% to 0.4%, said first inner cladding radius R2 of 6.5μm ~ 11μm, the relative refractive index difference of -0.06% and 0%, the second inner cladding radius R3 is 15μm ~ 30μm, relative refractive index difference in the range of 0.02% to 0.05%; outer layer is the outermost layer, layer is a pure silica outer vitreous silica layer. The present invention uses a dual structure of the inner cladding, the refractive index profile of the optical fiber so that the design is more reasonable. And the dopant for the core cladding were optimized, such that the viscosity of the core layer material is reduced, the viscosity can match core and cladding and effectively reduce the stress caused by drawing tension is concentrated in the core portion of the optical fiber caused by the increase in attenuation . In the optical fiber is fully compatible with G.652 standard, based on the attenuation performance is far superior to conventional G.652 fiber.