Optical fiber

An optical fiber, comprising:

• a glass fiber including a core and a cladding,
• wherein the cladding includes an inner cladding surrounding the core, a trench surrounding the inner cladding, and an outer cladding surrounding the trench,
• an average value of a refractive index of the core is larger than an average value of a refractive index of the inner cladding and a minimum value of a refractive index of the outer cladding,
• an average value of a refractive index of the trench is smaller than the average value of the refractive index of the inner cladding and the minimum value of the refractive index of the outer cladding,
• the core contains germanium dioxide,
• a relative refractive index difference of the core with respect to a refractive index of pure silica glass is 0.12% or more and 0.30% or less,
• a value obtained by subtracting a relative refractive index difference of the outer cladding with respect to the refractive index of pure silica glass from the relative refractive index difference of the core is 0.25% or more,
• a diameter of the core is 4.0 μm or more and 9.2 μm or less,
• a mode field diameter for light having a wavelength of 1310 nm is 8.2 μm or more and 9.6 μm or less,
• a zero dispersion wavelength is 1300 nm or more and 1324 nm or less,
• a zero dispersion slope is 0.073 ps/(nm2·km) or more and 0.092 ps/(nm2·km) or less,
• a cable cut-off wavelength is 1260 nm or less, and
• a bending loss for light having a wavelength of 1625 nm when the optical fiber is wound around a mandrel having a diameter of 60 mm is 0.1 dB or less per 100 turns.