Patent ID: 7953309

Claim:
An optical fiber composed of tellurite glass with a material zero-dispersion wavelength equal to or greater than 2 μm the optical fiber comprising: a core region; a first cladding section that is formed in such a manner as to enclose said core region, and has a plurality of air holes in a circumferential direction of said core region and along an axial direction of said core region; and a second cladding section that is formed in such a manner as to enclose said first cladding section, and has a refractive index approximately equal to an equivalent refractive index of said first cladding section; and wherein a relative refractive-index difference between said core region and said first cladding section is equal to or greater than 2%, thereby controlling a zero dispersion wavelength at a 1.55 μm band which is an optical telecommunication window.