Abstract: An optical fiber with a large effective area includes a core layer and a cladding layer. The core layer comprises an inner core layer having a radius of 1-4 ?m and a relative refractive index difference ?12 of ?0.2%??12<0% relative to the outer core layer, and an outer core layer having a radius of 4-7 ?m and a relative refractive index difference ?2 of ?0.15%-0.05%. ?12 remains unchanged or increases as the radius of the inner core layer increases. The cladding layer comprises an inner cladding layer cladding the core layer and having a radius of 7-20 ?m and a relative refractive index difference ?3 of ?0.5%˜?0.1%, a depressed cladding layer has a radius of 12-40 ?m, and a relative refractive index difference ?4 of ?1.0%˜?0.3%, and an outer cladding layer having a relative refractive index difference ?5 of ?0.2%˜?0.4%.