<p>A single-mode fiber with a large effective area comprises a fiber core layer and an outer covering layer. The fiber core layer covers a middle covering layer, and a sunk covering layer is disposed outside the middle covering layer. The fiber core layer comprises a first fiber core sublayer and a second fiber core sublayer. The first fiber core sublayer has a radius r1 of 1.5μm to 5μm and a relative refractive index differenceΔn1 of 0.05 to 0.22%; the second fiber core sublayer has a unilateral radial width (r2-r1) of 1.5μm to 5μm and a relative refractive index differenceΔn2 of 0.15% to 0.34%; andΔn1 is less thanΔn2. A larger effective area is obtained by means of a design of a refractive index profile of the fiber, and a better balance is obtained with aspect to a cutoff wavelength and bending performance and the like. The fiber can reach an effective area equal to or greater than 120μm2. The single-mode fiber is suitable for a high-speed large-capacity and long-distance transmission system and a long-distance repeaterless transmission system.</p>
