Abstract: Method of producing glass components and preforms for use in the method. The preform includes a primary rod having a constant outside diameter and a flat bottom portion, wherein the primary rod comprises a core rod surrounded by at least one outer cladding layer; and a cylindrical sacrificial tip having a first end attached to the flat bottom portion of the primary rod, a second end opposite the first end, and a hollow interior region extending fully from the first end to the second end, wherein the sacrificial tip is circular in cross section and the first end of the sacrificial tip has a constant inside diameter and outside diameter along its entire length from the first end to the second end, and wherein the constant outside diameter is equal to the outside diameter of the primary rod. When the preform is heated in a furnace, the sacrificial tip melts and collapses into a drawing bulb which either draws the primary rod directly into the glass fiber or results in a tapered (i.e.

Abstract: An apparatus for producing large glass preforms with minimal clad to-core waveguide distortion from a glass body having a weight, an outer surface, core rods, and a cladding surrounding and separated from the core rods by a gap. The apparatus includes collars affixed to the top and bottom of the cladding; a spacer upon which the core rods rest; a first unit holding and supporting both the bottom collar and the spacer; a second unit holding and supporting the top collar; and a frame defining a heating zone having a heating element to heat the glass body. The weight of the glass body above and below the molten glass in the heating zone is supported by the first and second units without contacting the outer surface of the glass body.

Abstract: A method for determining the refractive index profile of a preform when the RIP is not substantially step-index like. (a) The preform deflection function is measured and transformed into a measured RIP. (b) A RI level and radius are assumed for the preform layer being evaluated and a compensation level RIP is calculated. (c) A theoretical deflection function is generated corresponding to the assumed RI level and radius and the generated data are transformed into a fitting RIP. (d) The fitting RIP is compared to the measured RIP and the comparison is evaluated against a predetermined accuracy level for the preform layer being evaluated. (e) Steps (b) and (c) are repeated iteratively until the predetermined accuracy level has been achieved. Steps (b) through (e) are repeated for each preform layer that needs to be compensated. Finally, a measurement artifact compensated refractive index profile is calculated for the preform.

Abstract: An apparatus and related process for producing a high-strength weld between two glass components. Chucks clamp and move respective first ends of the glass components toward each other inside an enclosure, where the second ends are heated, softened, and welded together in a weld zone. The enclosure has layers of stacked quartz glass bricks and allows the weld zone to cool slowly and avoid stress. A propane quartz melting torch directs a flame inside the enclosure and toward the second ends as the glass components move toward each other. The flame softens the second ends and creates substantially smooth polished surfaces in the weld zone having an increased hydroxide content. At least 80% of the weld zone has a hydroxide content greater than about 10 ppm average in a 10 ?m depth from the surface and the tensile strength of the weld zone is above about 10 MPa.

Abstract: An automated large outside diameter preform tipping process. A zone of the preform is heated inside a furnace and softened. The preform tip is shaped and the process is controlled by the movement of the glass above and below the heating zone and by sensing the weight of the lower part of the preform, which in effect is a measure of the viscosity of the softened material. Once the correct viscosity is reached, the bottom holder is moved away from the top holder with a non-linear, accelerated velocity profile (derived from the FEM simulation of glass flow) which is precisely programmed and controlled so that the preform tip is optimally shaped (usually short and sharp tipped) with minimum waste and waveguide distortion when drawn into a fiber. The same concept of the non-linear, accelerated velocity profile can also be applied to other tipping processes such as horizontal preform tipping processes.

Abstract: Method of producing glass components and preforms for use in the method. The preform includes a primary rod having a constant outside diameter and a square bottom and a sacrificial tip having a first end attached to the bottom of the primary rod, a second end opposite the first end, and a hollow interior region extending from the first end to the second end. The sacrificial tip is circular in cross section and the first end of the sacrificial tip has an outside diameter equal to the outside diameter of the primary rod. When the preform is heated in a furnace, the sacrificial tip melts and collapses into a drawing bulb which either draws the primary rod directly into the glass fiber or results in a tapered (i.e. tipped) preform for subsequent fiber draw. Material waste as well as the drip time is reduced and the cladding-to-core ratio, crucial for waveguide properties, is maintained for the whole preform compared to a square cut preform without the sacrificial tip.

Abstract: Methods for preform and tube draw based on controlling forming zone viscosity determined by calculating a holding force exerted by the glass component in the forming zone on the strand being drawn below. The holding force may be calculated by determining a gravitational force applied to the strand and a pulling force applied to the strand by a pulling device, where the holding force is equal to the opposite of the algebraic sum of the gravitational and pulling forces. The holding force may also be calculated by measuring a stress-induced birefringence in the strand at a point between the forming zone and the pulling device, determining an amount of force applied to the strand at the point corresponding to the birefringence, and calculating the holding force by correcting the amount of force for a gravitational effect of the weight of the strand between the forming zone and the point.

Abstract: A variable seal for shielding from contaminants both an object to be heated in, and the heating element of, a high-temperature furnace. The seal has a first support ring and a second support ring separated by a distance. One or more components control the distance between the two support rings. A high-temperature fabric cylinder is attached to the support rings, is located where the object enters or exits the furnace, and surrounds at least a portion of the object. A mechanism engages the approximate center of the fabric cylinder to close the fabric cylinder as the one or more components decrease the distance between the two support rings and to open the fabric cylinder as the one or more components increase the distance between the two support rings, whereby the fabric cylinder continuously contacts the circumference of the object regardless of the diameter of the object.

Abstract: An apparatus and related process for producing large glass preforms with minimal clad to-core waveguide distortion from a glass body having a weight, an outer surface, core rods, and a cladding surrounding and separated from the core rods by a gap. The apparatus includes collars affixed to the top and bottom of the cladding; a spacer upon which the core rods rest; a first unit holding and supporting both the bottom collar and the spacer; a second unit holding and supporting the top collar; and a frame defining a heating zone having a heating element to heat the glass body. The weight of the glass body above and below the molten glass in the heating zone is supported by the first and second units without contacting the outer surface of the glass body.

Abstract: Apparatus and method for producing elongated glass components with low bow. The apparatus may include a heating element to heat a bulk glass component where a strand may be drawn from the bulk glass component in a downward direction and a gripper device including a clamping element to support the strand while pulling or drawing it from the bulk glass component in a linear motion, and a low-friction mounting element attached to the clamping element which allows translational movement of the clamping element in an x-y plane. The gripper device may further be used to reduce bow in the strand while it is being drawn by moving the clamping element on the mounting element in a direction opposite the direction of any measured transverse acceleration.

Abstract: Methods for producing glass components and obtainted glass component, e.g. optical fiber preform. A method includes providing a cladding tube (110) with a longitudinal axis including a first and a second bore separated by a chamfered region (114); inserting a spacer (120) into the first bore; inserting a rod (130) into the first bore (116); moving the spacer (120) into the chamfered section (114), causing the spacer (120) to rotate within the chamfered region (114); and rotating the cladding tube (110) into a vertical orientation, whereby the spacer (120) is prevented from entering the second bore (118) and supports the rod (130). Each portion of the chamfered region has a height perpendicular to the longitudinal axis greater than the height of the second bore.

Abstract: An apparatus and a method for measurement of transparent cylindrical articles during their manufacture in high temperature furnaces having openings for viewing the articles as they pass through the furnace. The cylindrical articles may, for example, be optical fiber preforms which have at least two layers of vitreous material and from which optical fibers are made. Measurement is accomplished using a digital camera with a sensing and digital recording device and a lens, and a processor programmed with an algorithm which analyzes the images recorded by the sensing and digital recording device by eliminating noise, identifying and locating the outer edges of the transparent cylindrical article and calculating measurements of the article including the diameter and the axial center of the article.

Abstract: Methods and apparatus for evaluating the geometric properties of optical fiber preforms, which methods include: providing an optical fiber preform having a longitudinal axis, an outer diameter and a circumference; providing a two-dimensional pattern having a length parallel to the longitudinal axis of the preform and a width greater than the outer diameter of the preform; providing an image capturing device disposed such that the preform is aligned between the pattern and the image capturing device; rotating the preform about its longitudinal axis and acquiring a first plurality of images of the pattern viewed through the preform at at least two different points along the circumference of the preform; and determining at least one geometric property of the preform from the first plurality of images.

Abstract: A method of forming a glass preform of predetermined length comprises providing a length of glass material to be separated to form a preform length and a remaining length; forming a notch in the glass material; inducing a tensile stress in excess of the tensile strength of the glass in an area adjacent to the notch; and separating the preform length from the remaining length at the notch.