According to some embodiments a method of processing an optical fiber comprises the steps of: (i) drawing the fiber at a drawing rate of at least 30 m/sec; and (ii) cooling the drawn fiber in a gas at an average cooling rate less than 5000 C./s, such that said cooling reduces the temperature of the fiber from an entering temperature in the range between 1500 C. and 1700 C. to another temperature in the range between 1200 C. and 1400 C., the gas being at a temperature between 800 C. and 1500 C.; and the thermal conductivity of the gas being not greater than 1.510.sup.4 cal/cm-s-K for at least one temperature within a range of 800 C. to 1500 C. at one atm (atmosphere) pressure absolute.

Disclosed herein are optical waveguide fibers comprising: (I) a core comprising an outer radius r.sub.1, a maximum refractive index delta percent .sub.1 max and core alpha, , of larger than 5; and (II) a cladding surrounding the core, the cladding comprising: (i) an inner cladding region having outer radius r.sub.2 and refractive index delta percent .sub.2, wherein .sub.1max>.sub.2; (ii) a trench region surrounding the inner cladding region, the trench region having an outer radius, r.sub.3 where r.sub.310 microns and refractive index delta percent .sub.3; and (iii) an outer cladding region having chlorine concentration of 1.2 wt. % surrounding the trench region and comprising refractive index delta percent .sub.t, wherein .sub.1max>.sub.4 and .sub.2>.sub.3, and .sub.4>.sub.3 and wherein the difference between .sub.4 and .sub.3 is 0.12 percent.

The single-mode optical fibers have a core region that includes an inner core region having a delta value .sub.1 and a radius r.sub.1 immediately surrounded by an outer core region of radius r.sub.2 and a delta value .sub.2<.sub.1, wherein .sub.1-.sub.2 is in the range from 0.3% to 2%. A cladding region of radius r.sub.3 immediately surrounds the core region. The inner and outer regions define an annular width r=r.sub.2r.sub.1. At least one of r.sub.1, r.sub.2, r and r.sub.3 changes with a period p in the longitudinal direction between first and second values each having a corresponding level distance d.sub.F. The change occurs over a transition distance d.sub.T such that d.sub.T/d.sub.F<0.1. The Brillouin frequency shift f changes by an amount [f] that is least 10 MHz over each period p, thereby allowing for Brillouin frequency-shift management in fiber-based sensor systems.

The present invention relates to an optical fiber which can improve OSNR in an optical transmission system in which Raman amplification and an EDFA are combined. With respect to the optical fiber, a predetermined conditional formula is satisfied by an effective area Aeff.sub.1450 [m.sup.2] at a wavelength of 1450 nm, a transmission loss .sub.1450 [/km] at a wavelength of 1450 nm, and a transmission loss .sub.1550.sub._.sub.dB [dB/km] at a wavelength of 1550 nm. Further, with respect to the optical fiber, another predetermined conditional formula is satisfied by an effective area Aeff.sub.1550 [m.sup.2] at a wavelength of 1550 nm, and a transmission loss .sub.1550 [/km] at a wavelength of 1550 nm.

An optical fiber having both low macrobend loss and low microbend loss. The fiber has a central core region, a first (inner) cladding region surrounding the central core region and having an outer radius r.sub.2>16 microns and relative refractive index .sub.2, and a second (outer) cladding region surrounding the first cladding region having relative refractive index, .sub.3, wherein .sub.1>.sub.3>.sub.2. The difference between .sub.3 and .sub.2 is greater than 0.12 percent. The fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm, and r.sub.1/r.sub.2 is greater or equal to 0.24 and bend loss at 1550 nm for a 15 mm diameter mandrel of less than 0.5 dB/turn.

A single-mode fiber with an ultra-low attenuation and a large effective area includes a core layer having a radius of 4.8 to 6.5 and a relative refractive index difference n.sub.1 of 0.06% to 0.10%, and cladding layers. The cladding layers includes an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary cladding layer. The inner cladding layer has a radius of 9 to 15 m and a relative refractive index difference of 0.40% to 0.15%. The trench cladding layer has a radius of 12 to 17 m and a relative refractive index difference of 0.8% to 0.3%. The auxiliary outer cladding layer has a radius of 37 to 50 m and a relative refractive index difference of 0.6% to 0.25%. The outer cladding layer is a pure-silicon-dioxide glass layer.

Disclosed herein are optical waveguide fibers comprising: (I) a core comprising an outer radius r.sub.1, a maximum refractive index delta percent .sub.1 max and core alpha, , of larger than 5; and (II) a cladding surrounding the core, the cladding comprising: (i) an inner cladding region having outer radius r.sub.2 and refractive index delta percent .sub.2, wherein .sub.1max>.sub.2; (ii) a trench region surrounding the inner cladding region, the trench region having an outer radius, r.sub.3 where r.sub.310 microns and refractive index delta percent .sub.3; and (iii) an outer cladding region having chlorine concentration of 1.2 wt. % surrounding the trench region and comprising refractive index delta percent .sub.4, wherein .sub.1max>.sub.4 and .sub.2>.sub.3, and .sub.4>.sub.3 and wherein the difference between .sub.4 and .sub.3 is 0.12 percent.

No core is disposed at the lattice point of a triangular lattice of a first layer LY1. First cores 11a and 11b of the core elements 10a and 10b are disposed at the lattice points of a second layer LY2. A first core 11c of the core element 10c and the second core 21 are alternately disposed at the lattice points of a third layer LY3. In a fourth layer LY4, no core is disposed at six lattice points, and the first cores 11a and 11b of the core elements 10a and 10b are disposed at the other lattice points. The second cores 21 are adjacent to the lattice points of the fourth layer LY4, at which no core is disposed. The effective refractive indexes of the core elements adjacent to each other are different from each other.

An optical fiber having both low macrobend loss and low microbend loss. The fiber has a central core region, a first (inner) cladding region surrounding the central core region and having an outer radius r.sub.2>16 microns and relative refractive index .sub.2, and a second (outer) cladding region surrounding the first cladding region having relative refractive index, .sub.3, wherein .sub.1>.sub.3>.sub.2. The difference between .sub.3 and .sub.2 is greater than 0.12 percent. The fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm, and r.sub.1/r.sub.2 is greater or equal to 0.24 and bend loss at 1550 nm for a 15 mm diameter mandrel of less than 0.5 dB/turn.

A single mode optical fiber having a core made from silica and less than or equal to about 6.5 weight % germania and having a maximum relative refractive index .sub.1MAX. The optical fiber also has an inner cladding surrounding the core and having a minimum relative refractive index .sub.2MIN. A difference between a softening point of the core and a softening point of the inner cladding is less than or equal to about 20 C., and .sub.1MAX>.sub.2MIN. The single mode optical fiber may also have an outer cladding surrounding the inner cladding made from silica or SiON. The outer cladding has a maximum relative refractive index .sub.3MAX, and .sub.3MAX>.sub.2MIN. A method for manufacturing an optical fiber includes providing a preform to a first furnace, the preform, drawing the optical fiber from the preform, and cooling the drawn optical fiber in a second furnace.