A method for manufacturing an optical fiber preform includes: producing a core preform including a core portion made of transparent glass and a first cladding layer obtained by adding fluorine to the core portion; and forming, on an outer periphery of the first cladding layer, a second cladding layer made of glass having a refractive index higher than that of the first cladding layer. Further, a refractive index profile is formed in the first cladding layer due to a fluorine concentration profile, the refractive index profile being provided at least near a boundary surface with the second cladding layer and having a profile such that a refractive index difference between a refractive index of the first cladding layer and a refractive index of the second cladding layer decreases in accordance with a reduction in a distance from the boundary surface with the second cladding layer.

The present disclosure provides optical fiber preforms formed from core canes having large core-clad ratio, intermediate core-cladding assemblies, and methods for making the preforms and core cladding assemblies. The preforms are made with capped core canes. The capping material has a coefficient of thermal expansion less than the coefficient of thermal expansion of the core cane and more closely matched to or lower than the coefficient of thermal expansion of the surrounding cladding monolith in a cane-in-soot process. Presence of the cap reduces stresses that arise from differential thermal expansion of the core cane and cladding materials and leads to preforms having low defect concentration and low probability of failure during subsequent thermal processing steps.

A disclosed multimode optical fiber comprises a core and a cladding surrounding the core. The core has an outer radius r.sub.1 in between 20 μm and 30 μm. The cladding includes a first outer cladding region having an outer radius r.sub.4a and a second outer cladding region having an outer radius r.sub.4b less than or equal to 45 μm. The second outer cladding region comprises silica-based glass doped with titania. The optical fiber further includes a primary coating with an outer radius r.sub.5 less than or equal to 80 μm, and a thickness (r.sub.5−r.sub.4) less than or equal to 30 μm. The optical fiber further includes a secondary coating with an outer radius r.sub.6 less than or equal to 100 μm. The secondary coating has a thickness (r.sub.6−r.sub.5) less than or equal to 30 μm, and a normalized puncture load greater than 3.6×10.sup.−3 g/micron.sup.2.

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.

An optical fiber includes: a central core portion; an intermediate layer; a trench layer; and a cladding portion. Further, relationships Δ1>Δ2>Δ3 and 0>Δ3 are satisfied, where Δ1, Δ2, and Δ3 are a relative refractive-index difference of the central core portion, the intermediate layer, and the trench layer, respectively, with respect to the cladding portion, Δ1 is equal to or larger than 0.34% and equal to or smaller than 0.37%, |Δ3| is equal to or larger than 0.1% and equal to or smaller than 0.25%, Δ1×|Δ3| is equal to or smaller than 0.08%.sup.2, a mode field diameter at a wavelength of 1310 nm is equal to or larger than 8.8 μm, and a transmission loss at a wavelength of 1550 nm is equal to or smaller than 0.195 dB/km.

The present disclosure relates to an optical fiber having a structure that has a low transmission loss and can be produced with high productivity. An optical fiber according to an embodiment includes a core and a cladding. The core is comprised of silica glass to which bromine is added, and the cladding has a refractive index lower than a maximum refractive index of the core. The core has compressive stress.

A method of manufacturing a multimode optical fiber includes specifying a peak wavelength λ.sub.P for the multimode optical fiber. The peak wavelength λ.sub.P corresponds to a wavelength at which the multimode optical fiber has a maximum bandwidth. The multimode optical fiber comprises a core and a cladding surrounding and directly adjacent to the core. The core has a radius r.sub.1 and a maximum relative refractive index Δ.sub.1,MAX>0. The cladding comprises a depressed-index region having a minimum relative refractive index Δ.sub.3,MIN<0 and a volume v. A draw tension T for the multimode optical fiber is selected based on a correlation relating peak wavelength λ.sub.P to draw tension T, the correlation comprising a correlation constant. The correlation constant K is a function of at least one of Δ.sub.1,MAX, r.sub.1, v, Δ.sub.3,MIN, and λ.sub.P. The multimode optical fiber is drawn from a preform at the draw tension T.

A method of manufacturing a tuned optical fiber includes providing a first preform from a set of like preforms each having substantially the same refractive index profile, including amount of axial variation relative to a target refractive index profile. The method includes drawing a reference optical fiber from the first preform and measuring a variation in an optical or physical property as a function of axial position. The method also includes drawing from a second preform from the set of like preforms the tuned optical fiber. The drawing includes using a time-varying tension that reduces the amount of variation of the optical or physical property of interest. The time-varying tension is defined by an amount of axial stress imparted to the tuned fiber needed to alter the refractive index profile and the at least one optical or physical property based on a stress-optic effect.

A device for generating a plasma and detecting a light signal. The plasma being intended to be generated in the vicinity of a study area of a sample and the light signal originating in the study area. The device including a current generator, an analysis unit, and an electrical and optical waveguide including means for transmitting an electric current configured to generate a plasma at one end of the means for transmitting the electric current in the vicinity of the study zone, means for detecting and transmitting configured to detect and transmit the light signal from the study area to the analysis unit, and an optical cladding portion, the means for transmitting the electric current and the means for detecting and transmitting the light signal being accommodated in the optical cladding portion.

Methods for classifying a core cane of an multimode optical fiber are disclosed. In embodiments, the method includes determining a relative refractive index profile Δ(r) of the core cane; fitting the relative refractive index profile Δ(r) to an alpha profile Δ.sub.fit(r) defined by:

[00001]${\Delta }_{\mathrm{fit}}\left(r\right)={\Delta }_{o,\mathrm{fit}}\left(1-{\left(\frac{r}{a_{\mathrm{fit}}}\right)}^{{\alpha }_{\mathrm{fit}}}\right)$

where Δ.sub.o,fit is a relative refractive index at a longitudinal centerline of the core cane, α.sub.fit is a core shape parameter, and a.sub.fit is an outer radius of the core cane; generating a non-alpha residual profile Δ.sub.diff(r)=Δ(r)−Δ.sub.fit(r) for the core cane; computing one or more metrics from Δ.sub.diff(r), and using the one or metrics in a classification of the core cane, the classification comprising a prediction of whether a bandwidth at a pre-determined wavelength of an optical fiber drawn from a preform comprising the core cane exceeds a pre-determined bandwidth at the pre-determined wavelength.