Optical fiber

An optical fiber comprising:

• a glass fiber including a core and a cladding, the cladding including an inner cladding surrounding an outer periphery of the core, a trench surrounding an outer periphery of the inner cladding, and an outer cladding surrounding an outer periphery of the trench, the inner cladding having a refractive index lower than a refractive index of the core, the trench having a refractive index lower than the refractive index of the inner cladding, and the outer cladding having a refractive index higher than the refractive index of the trench and lower than the refractive index of the core, the core being doped with germanium, the inner cladding having an average chlorine mass concentration of 500 ppm or more and 5000 ppm or less, r2/r1 being 2.2 or more and 3.6 or less, r3−r2 being 3 μm or more and 10 μm or less, Δ1−Δ2 being 0.15% or more and 0.40% or less, |Δ2| being 0.10% or less, and Δ3 being −0.70% or more and −0.10% or less, where Δ1 is a relative refractive index difference of the core with respect to the refractive index of the outer cladding, Δ2 is a relative refractive index difference of the inner cladding with respect to the refractive index of the outer cladding, Δ3 is a relative refractive index difference of the trench with respect to the refractive index of the outer cladding, r1 is a radius of the outer periphery of the core, r2 is a radius of the outer periphery of the inner cladding, and r3 is a radius of the outer periphery of the outer cladding,
• wherein a mode field diameter for light at a wavelength of 1310 nm is 8.8 μm or more and 9.6 μm or less, and
• wherein a bending loss for light at a wavelength of 1625 nm is 1.0 dB or less per turn when the optical fiber is wound on a mandrel having a diameter of 15 mm,
• wherein a bending loss for light at a wavelength of 1625 nm is 0.1 dB or less per 10 turns when the optical fiber is wound on a mandrel having a diameter of 30 mm,
• wherein a zero-dispersion wavelength is 1300 nm or more and 1324 nm or less,
• wherein a cable cutoff wavelength is 1260 nm or less.