Optical fiber

An optical fiber 1A comprises an optical transmission member 10 including a core 12 and a clad 14, a primary resin layer 22, and a secondary resin layer 24. The effective area of the optical transmission member 10 is 130 μm2 or larger. The transmission loss of the optical transmission member 10 at a wavelength of 1550 nm is 0.165 dB/km or smaller. The Young's modulus of the primary resin layer 22 is 0.7 MPa or lower, and the Young's modulus of the secondary resin layer 24 is 600 MPa or higher and 1500 MPa or lower. The difference between the transmission loss when the optical fiber 1A is wound at a tension of 80 g around a bobbin on which a metal mesh member having vertical wires of a 50-μm diameter and horizontal wires of a 50-μm diameter are wound and spaced at a pitch of 150 μm, and the transmission loss of an optical fiber coil is 1.0 dB/km or smaller.