An optical fiber including a core and a cladding including an inner cladding layer and an outer cladding layer is provided. The refractive index of the core 1, the refractive index of the inner cladding layer 2, and the refractive index of the outer cladding layer 3 have a relationship denoted by the following expressions: 1max>2min and 1max>3, and 0.01%<|2min3|<0.03%. An outer circumference radius r1 of the core, an outer circumferential radius r2 of the inner cladding layer, and an outer circumferential radius r3 of the outer cladding layer have a relationship denoted by the following expressions: r1<r2<r3, and 0.2r1/r20.5. A cable cut-off wavelength cc 1260 nm or less. A mode field diameter at a wavelength of 1310 nm is 8.6 m or more and 9.5 m or less.

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.

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.

An optical fiber with low fictive temperature along with a system and method for making the optical fiber are provided. The system includes a reheating stage that heats the fiber along the process pathway to a temperature sufficient to lower the fictive temperature of the fiber by relaxing the glass structure and/or driving the glass toward a more nearly equilibrium state. The fiber is drawn from a preform, conveyed along a process pathway, cooled and subsequently reheated to increase the time of exposure of the fiber to temperatures conducive to lowering the fictive temperature of the fiber. The process pathway may include multiple reheating stages as well as one or more fiber-turning devices.

Described is a process for the production of synthetic fused silica in which the deposition surface is located for a period of at least 50% of the build-up time of the soot body at a burner distance in which the horizontally integrated luminous intensity of the flame of the burner used in the targetless state is still at least of the maximum horizontally integrated luminous intensity of the flame.

The production of a quartz glass grit comprises the granulation of pyrogenetically produced silicic acid, and the formation of a SiO.sub.2 granulate and the vitrification of the SiO.sub.2 granulate using a treatment gas, which contains at least 30% by volume of helium and/or hydrogen. Said process is time consuming and cost intensive. In order to provide a method which makes it possible, starting from a porous SiO.sub.2 granulate, to manufacture, in a cost effective manner, a dense, synthetic quartz glass grit, which is suitable for melting bubble-free components made of quartz glass, according to the invention the vitrification of the SiO.sub.2 granulate occurs in a rotary kiln having a mullite-containing ceramic rotary kiln, for the manufacture of which a starting powder, which contains a molar proportion of at least 45% SiO.sub.2 and Al.sub.2O.sub.3 is applied by means of a thermal powder spraying method, forming a mullite-containing layer on a mold core, and the mold core is subsequently removed, and wherein the ceramic rotary kiln is flooded with a treatment gas or rinsed with a treatment gas, and wherein the ceramic rotary kiln is flooded with a treatment gas or rinsed with a treatment gas, which contains at least 30% by volume of helium and/or hydrogen.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50 C., preferably 50 C.<T.sub.h<250 C.

A preform for optical fiber made of a quartz glass sintered body which is made from quartz glass powder as a main raw material, in which at least a portion of the quartz glass sintered body is an opaque body, the opaque body has a visible light transmittance of 90% or less at a length of 5 mm or less in one direction, and the opaque body has a bulk density of 2.1 g/cm.sup.3 or more, or the opaque body has a visible light transmittance of 90% or less at a length of 5 mm or less in one direction, and the opaque body has an open porosity of 3.5% or less.

A fabricating method for a quartz vial having a body for containing a substance, a bottom closing a lower end of the body, a cylindrical neck disposed above the body, and a cylindrical mouth disposed above the neck and having an outer diameter larger than that of the neck includes the steps of forming an outer peripheral surface of the neck by shaving, and joining by thermal fusion, to the neck, the body that is separately fabricated. Thus, quartz vials having a predetermined shape can be mass-fabricated.

An optical sensor that includes a photonic crystal fiber (PCF) and an optical coupler. The PCF includes a hollow core with a first diameter (Dc), an inner cladding section, and an outer layer surrounding the inner cladding section. The inner cladding section includes a cladding material and a plurality of spaced apart circular-shaped channels disposed in the cladding material surrounding the hollow core. The cladding material includes at least one of glass, ceramic, and glass-ceramic. Each spaced apart circular-shaped channel has substantially the same size and an average diameter (d). A first end of the PCF is in optical communication with a light source and a second end of the PCF is in optical communication with the optical coupler.