Abstract: A method of forming an optical element is provided. The method includes producing silica-based soot particles using chemical vapor deposition, the silica-based soot particles having an average particle size of between about 0.05 ?m and about 0.25 ?m. The method also includes forming a soot compact from the silica-based soot particles and doping the soot compact with a halogen in a closed system by contacting the silica-based soot compact with a halogen-containing gas in the closed system at a temperature of less than about 1200° C.

Abstract: A method of processing an optical fiber includes drawing the optical fiber from an optical fiber preform within a draw furnace, the optical fiber extending from the draw furnace along a process pathway, the optical fiber comprising at least one halogen-doped core; and drawing the optical fiber through at least one slow cooling device positioned downstream from the draw furnace at a draw speed. The at least one slow cooling device exposes the optical fiber to a slow cooling device process temperature greater than or equal to 800° C. and less than or equal to 1600° C. The draw speed is such that the optical fiber has a residence time of at least 0.1 s in the at least one slow cooling device. An optical fiber made by such a process is also disclosed.

Abstract: A method for forming an optical quality glass is provided. The method includes contacting silica soot particles with a basic additive, forming a silica soot compact, and removing the basic additive from the silica soot compact. A method of forming a cladding portion of an optical fiber preform is also provided.

Abstract: A method of fabricating an optical fiber, the method including providing a core portion including a doped portion having greater than or equal to 1.6 wt. % of a halide dopant and eliminating seed precursor sites at an exterior surface of the core portion, the seed precursor sites forming seeds in the optical fiber, wherein the eliminating the seed precursor sites includes one or more of: (i) fabricating the core portion by densifying an exterior portion of a silica soot body prior to exposing the silica soot body to the halide dopant, and (ii) exposing the exterior surface of the core portion to a reactive etchant. The method further including forming an optical fiber preform by applying cladding material to the exterior surface of the core portion and drawing the fiber preform into the optical fiber.

Abstract: Apparatuses and methods for processing an optical fiber preform are disclosed. According to one aspect, an apparatus may generally include a muffle defining an interior volume enclosed by at least one sidewall and a handle assembly for supporting the optical fiber preform in the muffle. The handle assembly may be removably coupled to the muffle and extend into the interior volume. At least one baffle may be positioned in the interior volume and define an upper portion of the interior volume and a lower portion of the interior volume. The at least one baffle may define at least one flow channel between the upper portion of the interior volume and the lower portion of the interior volume.

Abstract: Apparatuses and methods for processing optical fiber preforms are disclosed. According to one aspect, an apparatus generally includes a furnace body and a muffle disposed within the furnace body. A space between the muffle and the furnace body defines a first interior volume. The muffle defines a second interior volume sealed from the first interior volume. An annulus gas is supplied to the first interior volume and a process gas is supplied to the second interior volume. A differential pressure gauge is coupled to the interior volumes. A flow controller is coupled to at least one of the gas sources and to the differential pressure gauge. The flow controller receives a differential pressure signal from the differential pressure gauge and adjusts a flow of a gas such that the pressure differential between the first interior volume and the second interior volume is minimized.

Abstract: A method of forming an optical fiber preform includes: flowing a silicon halide and an oxidizer inside of a substrate tube, wherein a molar ratio of the silicon halide to the oxidizer is from about 1.5 to about 5.0; applying a plasma to the substrate tube to heat the substrate tube to a temperature of from about 1000° C. to about 1700° C.; and depositing silica glass comprising a halogen inside the substrate tube.

Abstract: Preparation of halogen-doped silica is described. The preparation includes doping silica with high halogen concentration, sintering halogen-doped silica to a closed-pore state, and subjecting the closed-pore silica body to a thermal treatment process and/or a pressure treatment process. The temperature of thermal treatment is sufficiently high to facilitate reaction of unreacted doping precursor trapped in voids or interstices of the glass structure, but is below temperatures conducive to foaming. Core canes or fibers drawn from halogen-doped silica subjected to the thermal treatment and/or pressure treatment show improved optical quality and possess fewer defects. The thermal treatment and/or pressure treatment is particularly advantageous when used for silica doped with high concentrations of halogen.

Abstract: Preparation of halogen-doped silica is described. The preparation includes doping silica with high halogen concentration and sintering halogen-doped silica to a closed-pore state in a gas-phase environment that has a low partial pressure of impermeable gases. Impermeable gases are difficult to remove from halogen-doped fiber preforms and lead to defects in optical fibers drawn from the preforms. A low partial pressure of impermeable gases in the sintering environment leads to a low concentration of impermeable gases and a low density of gas-phase voids in densified halogen-doped silica. Preforms with fewer defects result.

Abstract: A method for forming an optical quality glass is provided. The method includes contacting silica soot particles with a basic additive, forming a silica soot compact, and removing the basic additive from the silica soot compact. A method of forming a cladding portion of an optical fiber preform is also provided.

Abstract: A method of forming an optical fiber, including: exposing a soot core preform to a dopant gas at a pressure of from 1.5 atm to 40 atm, the soot core preform comprising silica, the dopant gas comprising a first halogen doping precursor and a second halogen doping precursor, the first halogen doping precursor doping the soot core preform with a first halogen dopant and the second halogen precursor doping the soot core preform with a second halogen dopant; and sintering the soot core preform to form a halogen-doped closed-pore body, the halogen-doped closed-pore body having a combined concentration of the first halogen dopant and the second halogen dopant of at least 2.0 wt %.

Abstract: A method of processing an optical fiber includes drawing the optical fiber from an optical fiber preform within a draw furnace, the optical fiber extending from the draw furnace along a process pathway, the optical fiber comprising at least one halogen-doped core; and drawing the optical fiber through at least one slow cooling device positioned downstream from the draw furnace at a draw speed. The at least one slow cooling device exposes the optical fiber to a slow cooling device process temperature greater than or equal to 800° C. and less than or equal to 1600° C. The draw speed is such that the optical fiber has a residence time of at least 0.1 s in the at least one slow cooling device. An optical fiber made by such a process is also disclosed.

Abstract: Small-radius coated optical fibers having large mode field diameter and low bending losses. The coated fiber may have an outer radius of 110 ?m or less, while providing a mode field diameter of 9.0 ?m or greater and a bending loss when wrapped about a 15 mm mandrel of 0.5 dB/km or less at wavelength of 1550 nm. The coated fiber may have a mode field diameter of 9.2 ?m or greater and may have a bending loss at 1550 nm of 0.25 dB/km or less when wrapped about a 20 mm mandrel or a bending loss at 1550 nm of 0.02 dB/km or less when wrapped about a 30 mm mandrel.

Abstract: A method for forming an optical quality glass is provided. The method includes contacting silica soot particles with a basic additive, forming a silica soot compact, and removing the basic additive from the silica soot compact. A method of forming a cladding portion of an optical fiber preform is also provided.

Abstract: Apparatuses and methods for processing an optical fiber preform are disclosed. According to one aspect, an apparatus may generally include a muffle defining an interior volume enclosed by at least one sidewall and a handle assembly for supporting the optical fiber preform in the muffle. The handle assembly may be removably coupled to the muffle and extend into the interior volume. At least one baffle may be positioned in the interior volume and define an upper portion of the interior volume and a lower portion of the interior volume. The at least one baffle may define at least one flow channel between the upper portion of the interior volume and the lower portion of the interior volume.

Abstract: Small-radius coated optical fibers having large mode field diameter and low bending losses. The coated fiber may have an outer radius of 110 ?m or less, while providing a mode field diameter of 9.0 ?m or greater and a bending loss when wrapped about a 15 mm mandrel of 0.5 dB/km or less at wavelength of 1550 nm. The coated fiber may have a mode field diameter of 9.2 ?m or greater and may have a bending loss at 1550 nm of 0.25 dB/km or less when wrapped about a 20 mm mandrel or a bending loss at 1550 nm of 0.02 dB/km or less when wrapped about a 30 mm mandrel.

Abstract: Small-radius coated optical fibers having large mode field diameter and low bending losses. The coated fiber may have an outer radius of 110 ?m or less, while providing a mode field diameter of 9.0 ?m or greater and a bending loss when wrapped about a 15 mm mandrel of 0.5 dB/km or less at wavelength of 1550 nm. The coated fiber may have a mode field diameter of 9.2 ?m or greater and may have a bending loss at 1550 nm of 0.25 dB/km or less when wrapped about a 20 mm mandrel or a bending loss at 1550 nm of 0.02 dB/km or less when wrapped about a 30 mm mandrel.

Abstract: Preparation of halogen-doped silica is described. The preparation includes doping silica with high halogen concentration and sintering halogen-doped silica to a closed-pore state. The sintering includes a high pressure sintering treatment and a low pressure sintering treatment. The high pressure sintering treatment is conducted in the presence of a high partial pressure of a gas-phase halogen doping precursor and densifies a silica soot body to a partially consolidated state. The low pressure sintering treatment is conducted in the presence of a low partial pressure of gas-phase halogen doping precursor and transforms a partially consolidated silica body to a closed-pore state. The product halogen-doped silica glass exhibits little foaming when heated to form fibers in a draw process or core canes in a redraw process.

Abstract: Bromine doping of silica glass is demonstrated. Bromine doping can be achieved with SiBr4 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.

Abstract: Apparatuses and methods for processing optical fiber preforms are disclosed. According to one aspect, an apparatus generally includes a furnace body and a muffle disposed within the furnace body. A space between the muffle and the furnace body defines a first interior volume. The muffle defines a second interior volume sealed from the first interior volume. An annulus gas is supplied to the first interior volume and a process gas is supplied to the second interior volume. A differential pressure gauge is coupled to the interior volumes. A flow controller is coupled to at least one of the gas sources and to the differential pressure gauge. The flow controller receives a differential pressure signal from the differential pressure gauge and adjusts a flow of a gas such that the pressure differential between the first interior volume and the second interior volume is minimized.