The present disclosure is directed to a method of making an optical fiber with improved bend performance, the optical fiber having a core and at least one cladding layer, and a chlorine content in the in the last layer of the at least one cladding layer that is greater than 500 ppm by weight. The fiber is prepared using a mixture of a carrier gas, a gaseous chlorine source material and a gaseous reducing agent during the sintering of the last or outermost layer of the at least one cladding layer. The inclusion of the reducing gas into a mixture of the carrier gas and gaseous chlorine material reduces oxygen-rich defects that results in at least a 20% reduction in TTP during hydrogen aging testing.

A single mode optical fiber having a core made from silica and less than or equal to about 11 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 first outer cladding surrounding the inner cladding and a second outer cladding surrounding the first outer cladding. The viscosity at 1650 C. of the second outer cladding minus the viscosity at 1650 C. of the first outer cladding is greater than 0.1e.sup.7 Poise, 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 first outer cladding has a maximum relative refractive index .sub.3MAX, and .sub.3MAX>.sub.2MIN.

A single mode optical fiber having a core made from silica and less than or equal to about 11 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 first outer cladding surrounding the inner cladding and a second outer cladding surrounding the first outer cladding. The viscosity at 1650 C. of the second outer cladding minus the viscosity at 1650 C. of the first outer cladding is greater than 0.1e.sup.7 Poise, 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 first outer cladding has a maximum relative refractive index .sub.3MAX, and .sub.3MAX>.sub.2MIN.

This ultra-low-loss optical fiber comprises a core having a higher relative refractive index difference than silica and a cladding having a lower relative refractive index difference than silica. The relative refractive index difference of the core with respect to the refractive index of silica is 0.0030 to 0.0055, for example, and the relative refractive index difference of the cladding with respect to the refractive index of silica is 0.0020 to 0.0003. The ultra-low-loss optical fiber has the loss characteristic of simultaneously having optical losses of at most 0.324 dB/km at a wavelength of 1310 nm, at most 0.320 dB/km at a wavelength of 1383 nm, at most 0.184 dB/km at a wavelength of 1550 nm, and at most 0.20 dB/km at a wavelength of 1625 nm. The ultra-low-loss optical fiber is supercooled when the surface temperature of the optical fiber has a temperature range in a glass transition section during drawing.

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.

An optical fiber package is described comprising a light transmitting core having a core diameter, a coating layer surrounding the core, and wherein the amount of chlorine in the light transmitting core region is homogeneous and comprises at least 3000 ppm. The fiber package is such that the optical fiber core exhibits a reduction in the hydrogen induced attenuation losses. A method for fabricating the optical fiber package is also disclosed.

The present disclosure is directed to a method of making an optical fiber with improved bend performance, the optical fiber having a core and at least one cladding layer, and a chlorine content in the in the last layer of the at least one cladding layer that is greater than 500 ppm by weight. The fiber is prepared using a mixture of a carrier gas, a gaseous chlorine source material and a gaseous reducing agent during the sintering of the last or outermost layer of the at least one cladding layer. The inclusion of the reducing gas into a mixture of the carrier gas and gaseous chlorine material reduces oxygen-rich defects that results in at least a 20% reduction in TTP during hydrogen aging testing.

Bromine doping of silica glass is demonstrated. Bromine doping can be achieved with SiBr.sub.4 as a precursor. Bromine doping can occur during heating, consolidation or sintering of a porous silica glass body. Doping concentrations of bromine increase with increasing pressure of the doping precursor and can be modeled with a power law equation in which doping concentration is proportional to the square root of the pressure of the doping precursor. Bromine is an updopant in silica and the relative refractive index of silica increases approximately linearly with doping concentration. Bromine can be used as a dopant for optical fibers and can be incorporated in the core and/or cladding regions. Core doping concentrations of bromine are sufficient to permit use of undoped silica as an inner cladding material in fibers having a trench in the refractive index profile. Co-doping of silica glass with bromine and chlorine is also demonstrated.

One embodiment of the disclosure relates to a method of making an optical fiber comprising the steps of: (i) exposing a silica based preform with at least one porous glass region having soot density of to a gas mixture comprising SiCl.sub.4 having SiCl.sub.4 mole fraction y.sub.SiCl4 at a doping temperature T.sub.dop such that parameter X is larger than 0.03 to form the chlorine treated preform, wherein $X=\frac{1}{1+\left[\left(\frac{}{{}_s-}\right)\frac{0.209748T_{\mathrm{dop}}\mathrm{Exp}\left[-5435.33/T_{\mathrm{dop}}\right]}{y_{\mathrm{SiCl}4}^{3/4}}\right]}$
and .sub.s is the density of the fully densified soot layer; and (ii) exposing the chlorine treated preform to temperatures above 1400 C. to completely sinter the preform to produce sintered optical fiber preform with a chlorine doped region; and (iii) drawing an optical fiber from the sintered optical preform.

A method for producing a multicore optical fiber includes: forming a common cladding tube by providing a first glass rod with a plurality of first holes and one or more second holes passing through the first glass rod in an axial direction, the one or more second holes having a diameter different from a diameter of the plurality of first holes; subjecting inner surfaces of the plurality of first holes and inner surfaces of the one or more second holes to a gas-phase process; and inserting a plurality of core rods into the plurality of first holes subjected to the gas-phase process, respectively, inserting a refractive index changing part rod into each of the one or more second holes subjected to the gas-phase process, and performing thermal integration to form a second glass rod. The common cladding tube is formed such that the diameter of the plurality of first holes is no more than 4 times the diameter of the one or more second holes.