Optical fiber and optical cable

Abstract

Provided is an optical fiber that has a small bending loss, can be securely prevented from being fractured due to accidental bending during installation or other operations, and is compliant with the G. 652 standard. An optical fiberincludes a core, a first cladding, a second cladding, and a third cladding. The relative refractive index difference Δof the coreis in the range of 0.3% to 0.38%, the relative refractive index difference Δof the first claddingis equal to or smaller than 0%, and the relative refractive index difference Δof the second claddingis in the range of −1.8% to −0.5%. The inner radius rand the outer radius rof the second claddingsatisfy the expression '0.4r+10.5<r<0.2r+16', and the inner radius rof the second claddingis equal to or greater than 8 μm. The bending loss at a wavelength of 1550 nm and at a radius of curvature of 7.5 mm is smaller than 0.1 dB/turn, and the bending loss at a wavelength of 1625 nm and at a radius of curvature of 4 mm is greater than 0.1 dB/turn.