Abstract: A method and apparatus for non-destructive analysis of canes and preforms which contain "striae" in which the cane or preform is transversely illuminated with a beam of light at a wavelength which is long enough to substantially eliminate the effect of striae resulting from variations in dopant concentration.

Abstract: A method and apparatus is provided for controlling the diameter of a coated optical waveguide fiber. The viscosity profile of the coating material is controlled by adjusting the temperature of a portion of the coating assembly based on a measurement of the diameter of the coated fiber. By controlling the viscosity profile of the coating material, the amount of coating applied to the fiber is controlled,, thereby determining the diameter of the coated fiber.

Abstract: A reactor for applying a carbon coating to an optical waveguide fiber wherein the buildup of reaction by-products within the reactor is reduced by providing internal and external fiber exit ports with the diameter of the internal fiber exit port being greater than the diameter of the external fiber exit port, and gas shielding at the external fiber exit port.

Abstract: An optical waveguide fiber with a core region 1 and a cladding region 2, wherein said cladding region 2 includes an outer cladding region 3 is disclosed wherein said outer cladding region 3 is a very thin (less than 1 .mu.m in thickness) layer of TiO.sub.2 --SiO.sub.2 glass which results in a substantial reduction in the number of fiber breaks resulting from the fiber drawing process and having a predetermined TiO.sub.2 concentration less than or equal to about 10 wt. %. A method for making said fiber is also disclosed.

Abstract: A method for drawing glass objects from glass feedstock, wherein a dimension of the glass object is measured on-line and controlled by a control structure which compensates for the deadtime between a change to the drawing speed and the measurement of the effect of that change to the measured dimension. The model which compensates for the deadtime is preferably nonlinear, and the control gains and model parameters are preferably continuously calculated during the drawing process. The invention is particularly applicable to drawing optical waveguide cane from optical waveguide preforms.

Abstract: A method and apparatus for drawing an optical waveguide fiber which minimizes fiber bow caused by differential stresses in the cladding layer of the fiber are disclosed. The fiber is drawn from a preform which is heated in a draw furnace. Gases introduced at the top of the furnace form a boundary layer adjacent to the fiber which passes through the furnace, along with the fiber, into a tube. The tube isolates the fiber from the ambient atmosphere so that the boundary layer of gases established in the furnace remains substantially uniform until the viscosity of the cladding layer of the fiber is high enough to minimize differential stresses around the circumference of the fiber.

Abstract: An optical waveguide fiber with improved bend loss performance while maintaining cutoff wavelength, .lambda..sub.c, and zero dispersion wavelength, .lambda..sub.0, in practical operating ranges. The fiber includes an inner core region with a refractive index delta higher than the rest of the core and a reduced diffusion tail at the core/cladding interface. Optionally, a ring at the outer portion of the core is provided to compensate for increased .lambda..sub.0 which results from the higher inner core refractive index delta. This ring also contributes to the reduced diffusion tail at the core/cladding interface.

Abstract: A planar optical waveguide comprises a substrate 1, a waveguide core layer 2, at least one planar optical element, wherein said planar optical element comprises at least one optically functional interface 3 which is adjacent to a cavity 4, and an overclad layer 5. The cavity enhances the optical characteristics of the planar optical element because of the substantial difference in the refractive index of the cavity as compared to the refractive index of said waveguide core layer.

Abstract: An optical waveguide fiber with a core region 1 and a cladding region 2, wherein the cladding region 2 includes an outer cladding region 3 is disclosed wherein the outer cladding region 3 is a very thin (less than 1 .mu.m in thickness) layer of TiO.sub.2 -SiO.sub.2 glass which results in a substantial reduction in the number of fiber breaks resulting from the fiber drawing process and having a predetermined TiO.sub.2 concentration less than or equal to about 10 wt. %. A method for making the fiber is also disclosed.