OPTICAL FIBER HAVING EXTREMELY LOW LOSS AND METHOD AND APPARATUS FOR MANUFACTURING THE SAME

摘要

An extreme low loss optical fiber comprises a core having a high relative refractive index difference compared to silica, and a cladding having a low relative refractive index difference compared to silica. The relative refractive index difference compared to the refractive index of silica of the core is, for example, 0.0030 or more and 0.0055 or less, and the relative refractive index difference compared to the refractive index of silica of the cladding is -0.0020 or more and -0.0003 or less. The extreme low loss optical fiber has loss characteristics wherein optical loss is 0.324 dB/km or less at a wavelength of 1310 nm, optical loss is 0.320 dB/km or less at a wavelength of 1383 nm, optical loss is 0.184 dB/km or less at a wavelength of 1550 nm, and optical loss is 0.20 dB/km or less at a wavelength of 1625 nm at the same time. The extreme low loss optical fiber is supercooled when the surface temperature of the optical fiber has the temperature range within a glass transition section during a drawing process.