A fused-biconical-taper bend-insensitive single mode optical fiber includes a core and a cladding. The core is a fluorine-germanium co-doped silicon-dioxide quartz glass layer, a diameter D.sub.core thereof is 7-10 m, and a relative refractive index difference 1 thereof is 0.20% to 0.40%. A range of Ge is 0.30% to 0.60%, and a range of F is 0.05% to 0.15%. The cladding includes three layers. A first layer is a fluorine-germanium co-doped silicon-dioxide quartz glass layer, a relative refractive index difference 31 thereof is 0.02% to 0.10%, and a diameter D31 thereof is 15-30 m. A second layer is a fluorine-doped silicon-dioxide quartz glass layer, a relative refractive index difference 32 thereof is 0.01% to 0.05%, and a diameter D32 thereof is 30-50 m. A third layer is a pure silicon-dioxide quartz glass layer, and a diameter D33 thereof is 124-126 m.

The present embodiment relates to an MCF and the like suitable for fabricating an FBG with improved ripple characteristics. The MCF is mainly composed of silica glass, and comprises a plurality of light guiding structures and a common cladding. Each of the light guiding structures includes a core, a first cladding, and a second cladding. The refractive index of the second cladding is higher than that of the first cladding and is lower than those of the core and the common cladding. Further, at least a part of an inner cladding region, constituted by the first cladding and the second cladding, contains a photosensitive material having photosensitivity of changing a refractive index of a glass region containing the photosensitive material in response to irradiation of light with a specific wavelength.

An optical fiber comprises, from a center to a periphery, a fiber core of undoped silica; a cladding layer; and a coating of polyacrylate, wherein the fiber core has a radius of 5 to 7 m and an ellipticity of less than 1.5%, the cladding layer with an ellipticity of less than 0.4% comprises inner, intermediate, and outer cladding layers, the inner cladding layer being doped with fluorine of 5 to 12 m thickness, and refractive index difference to fiber core of 0.4 to 0.2%, the outer cladding layer being undoped quartz of 25 to 45 m thickness, and the coating comprises an inner coating of 25 to 40 m thickness, and an outer coating of 25 to 35 m thickness and an ellipticity of less than 2%. The optical fiber has high durability and large effective transmission area, a method and system for preparing such optical fiber are also disclosed.

An optical fiber according to an embodiment comprises, as a structure suitable for large capacity transmission over a long haul, a core, a cladding having an outer diameter of 80 m or more and 130 m or less, a primary coating, and a secondary coating having elasticity higher than that of the primary coating and an outer diameter of 210 m or less. The optical fiber having the structure as described above has an MFD of 10 m or more at a wavelength of 1550 nm, a cable cutoff wavelength longer than 1260 nm, and a microbending loss of 0.6 dB/km or less at a wavelength of 1550 nm.

An optical fiber comprises, from a center to a periphery, a fiber core of undoped silica; a cladding layer; and a coating of polyacrylate, wherein the fiber core has a radius of 5 to 7 m and an ellipticity of less than 1.5%, the cladding layer with an ellipticity of less than 0.4% comprises inner, intermediate, and outer cladding layers, the inner cladding layer being doped with fluorine of 5 to 12 m thickness, and refractive index difference to fiber core of 0.4 to 0.2%, the outer cladding layer being undoped quartz of 25 to 45 m thickness, and the coating comprises an inner coating of 25 to 40 m thickness, and an outer coating of 25 to 35 m thickness and an ellipticity of less than 2%. The optical fiber has high durability and large effective transmission area, a method and system for preparing such optical fiber are also disclosed.

The present embodiment relates to an MCF and the like suitable for fabricating an FBG with improved ripple characteristics. The MCF is mainly composed of silica glass, and comprises a plurality of light guiding structures and a common cladding. Each of the light guiding structures includes a core, a first cladding, and a second cladding. The refractive index of the second cladding is higher than that of the first cladding and is lower than those of the core and the common cladding. Further, at least a part of an inner cladding region, constituted by the first cladding and the second cladding, contains a photosensitive material having photosensitivity of changing a refractive index of a glass region containing the photosensitive material in response to irradiation of light with a specific wavelength.

A co-doped optical fiber is provided having an attenuation of less than about 0.17 dB/km at a wavelength of 1550 nm. The fiber includes a core region in the fiber having a graded refractive index profile with an alpha of greater than 5. The fiber also includes a first cladding region in the fiber that surrounds the core region. Further, the core region has a relative refractive index of about 0.10% to about +0.05% compared to pure silica. In addition, the core region includes silica that is co-doped with chlorine at about 1.2% or greater by weight and fluorine between about 0.1% and about 1% by weight.

A fused-biconical-taper bend-insensitive single mode optical fiber includes a core and a cladding. The core is a fluorine-germanium co-doped silicon-dioxide quartz glass layer, a diameter D.sub.core thereof is 7-10 m, and a relative refractive index difference 1 thereof is 0.20% to 0.40%. A range of Ge is 0.30% to 0.60%, and a range of F is 0.05% to 0.15%. The cladding includes three layers. A first layer is a fluorine-germanium co-doped silicon-dioxide quartz glass layer, a relative refractive index difference 31 thereof is 0.02% to 0.10%, and a diameter D31 thereof is 15-30 m. A second layer is a fluorine-doped silicon-dioxide quartz glass layer, a relative refractive index difference 32 thereof is 0.01% to 0.05%, and a diameter D32 thereof is 30-50 m. A third layer is a pure silicon-dioxide quartz glass layer, and a diameter D33 thereof is 124-126 m.

An optical fiber comprising: (i) a chlorine doped silica based core comprising a core alpha ()>10, and maximum refractive index delta .sub.1max % and Cl concentration >1 wt %; (ii) a cladding surrounding the core, the cladding comprising: (a) an inner cladding region adjacent to and in contact with the core and having a refractive index delta .sub.2 and a minimum refractive index delta .sub.2min such that .sub.2min<.sub.1max, the inner cladding region comprising fluorine doped silica and the refractive index delta .sub.2 with region that decreases with radial position, and (b) an outer cladding region surrounding the inner cladding region and having refractive index delta .sub.3, such that .sub.2min<.sub.3. The fiber has mode field diameter MFD at 1310 nm of 9 microns, a cable cutoff of 1260 nm, zero dispersion wavelength of 1300 nmzero dispersion wavelength 1324 nm and bend loss at 1550 nm for a 20 mm mandrel of less than 0.5 dB/turn.

The present invention provides a large-effective-mode-area low-loss optical fiber with optimized cladding components, which comprises a core layer and a cladding comprising, from the inside to the outside, a first sinking layer, a second sinking layer, an optional third sinking layer, and an outer cladding. In the present invention, phosphorus and aluminum are co-doped in the optical fiber cladding, to form a tetrahedron [AlPO.sub.4] in glass, thus optimizing the viscosity of the cladding while effectively reducing the refractive index of the cladding, without causing increased hydrogen loss. The process is simple, and highly repeatable.