Patent ID: 6901197

Claim:
An optical fiber comprising a core, an inner cladding surrounding the core, and an outer cladding surrounding the inner cladding, wherein the core is a first main medium having a refractive index n 1 at a wavelength λ between 200 nm and 1700 nm; the inner cladding, for at least a portion of the fiber, comprises a second main medium having a refractive index n 2 lower than n 1 at the wavelength λ, and a plurality of sub medium regions having refractive index n 3 lower than n 2 at the wavelength λ; the outer cladding is a third main medium having a refractive index n 4 higher than an average refractive index N of the inner cladding at the wavelength λ; said core, inner cladding, outer cladding and sub medium regions extending along a fiber axis; a bending loss of a fundamental mode of the fiber at a wavelength λ is lower than 0.1 dB/m at a bending diameter of 15 mm; a mode-field diameter of the fundamental mode at an end portion of the fiber at the wavelength λ is between 8.0 μm and 50 λ; and a bending loss of a first higher-order mode at the wavelength λ is higher than 1 dB/m at a bending diameter of 30 mm.