Abstract: An apparatus is provided for applying a tensile force along the longitudinal axis of a cane assembly during the deposition of soot thereon to produce an optical fiber preform. Fiber drawn from such a preform exhibits improved core/clad concentricity. The tensile force may be applied at one or both ends of the cane assembly, with application at both ends being preferred. The tensile force may be varied during the deposition of soot. The cane assembly may be annealed prior to beginning the deposition of soot thereon.

Abstract: A precision burner for oxidizing halide-free, silicon-containing compounds, such as, octamethyl-cyclotetrasiloxane (OMCTS), is provided. The burner includes a subassembly (13) which can be precisely mounted on a burner mounting block (107) through the use of an alignment stub (158), a raised face (162) on the burner mounting block (107), and a recess (160) in the back of the subassembly (13). The burner's face includes four concentric gas-emitting regions: a first central region (36, 90) from which exits a mixture of OMCTS and O.sub.2, a second innershield region (38, 92) from which exits N.sub.2, a third outershield region (40, 42, 94, 96) from which exits O.sub.2, and a fourth premix region (44, 98) from which exits a mixture of CH.sub.4 and O.sub.2. The burner provides more efficient utilization of halide-free, silicon-containing raw materials than prior burners.

Abstract: An apparatus for producing a glass preform by VAD, includes a rotational drive device for rotating soot material, a detection device for detecting vibrations of the soot material, and a control device for controlling rotational speed of the rotational drive device. The control drive device changes the rotational speed of the rotational drive device on the basis of a detection output of the detection device.

Abstract: The invention concerns the method and apparatus to fabricate an oval cross-sectional optical waveguide which only allows light to propagate in one direction of polarization. The optical waveguide preform for such an optical waveguide according to the modified chemical vapor deposition (MCVD) process is produced in such a way, that cooling is used to provide the substrate tube with an oval or elliptical temperature cooling profile. The apparatus for carrying out the fabrication method includes a cooling device (5) mounted to a support (3) beside a gas burner (4) and consists of two nozzles (10) directed toward the substrate tube (2) so as to direct cooling gas toward the substrate tube as glass layers are deposited thereon to produce core and cladding of the optical waveguide. The nozzles rotate synchronously with the substrate tube.