An optical fiber having a reduced attenuation includes a silica glass core and a silica glass cladding. The silica glass core has substantially no germanium and includes a first core and a second core. The second core encloses the first core, the refractive index of the second core is larger than the refractive index of the first core, and the average value of halogen concentration of the second core is 5000 ppm or more. The silica glass cladding surrounds the second core and contains substantially no germanium. The refractive index of the cladding is smaller than the refractive index of the first core.

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.

The present invention relates to an MMF with a structure for relaxing wavelength dependence of transmission bandwidth. In the MMF, a doping amount of a dopant for control of refractive index is adjusted, so as to make each of an OFL bandwidth at a wavelength of 850 nm and an OFL bandwidth at a wavelength of at least one of 980 nm, 1060 nm, and 1300 nm become not less than 1500 MHz.Math.km, make the OFL bandwidth at the wavelength of at least one of 980 nm, 1060 nm, and 1300 nm become wider than the OFL bandwidth at the wavelength of 850 nm, and effectively suppress increase in transmission loss.

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.

Hollow ingots of transparent synthetic vitreous silica glass of external diameter greater than 400 mm and internal diameter greater than 300 mm are disclosed. The ingots are substantially free from bubbles or inclusions greater than 100 m in diameter, have no more than 100 ppB of any individual metallic impurity, and have chlorine concentration less than 5 ppM. Also disclosed are methods for producing such ingots, in which a porous soot body of density greater than 0.4 g/cm.sup.3 is deposited on an oxidation resistant mandrel. The soot body is dehydrated on a mandrel comprising graphite, carbon fiber reinforced carbon, silicon carbide, silicon impregnated silicon carbide, silicon carbide-coated graphite or vitreous silica, either under vacuum or in the presence of a reducing gas, and then sintered to transparent pore-free glass under vacuum or in an atmosphere of helium.

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.

An optical fiber having a core comprising silica and greater than 1.5 wt % chlorine and less than 0.5 wt % F, said core having a refractive index .sub.1MAX, and a inner cladding region having refractive index .sub.2MIN surrounding the core, where .sub.1MAX>.sub.2MIN.

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.