Abstract: An optical fiber-based sensor is described that is suitable for operation in a gas-rich environment. The sensor comprises a chamber into which are mounted one or more segments of optical fiber, into which are inscribed a plurality of sensor gratings. Each of the plurality of sensor gratings is configured to have the same wavelength shift over time in response to a change in gas diffusion, such that gas diffusion parameters are excluded in the determination of the respective amount of change in temperature, applied strain, and gas diffusion. Also described is a fiber, and techniques for making same, comprising of cores extend through a common cladding. The cores are doped so as to create, in conjunction with the cladding, a plurality of waveguides having the same wavelength shift over time is response to a change in gas diffusion, but different wavelength shifts in response to changes in other parameters.

Abstract: An optical fiber-based sensor is described that is suitable for operation in a gas-rich environment. The sensor comprises a chamber into which are mounted one or more segments of optical fiber, into which are inscribed a plurality of sensor gratings. Each of the plurality of sensor gratings is configured to have the same wavelength shift over time in response to a change in gas diffusion, such that gas diffusion parameters are excluded in the determination of the respective amount of change in temperature, applied strain, and gas diffusion. Also described is a fiber, and techniques for making same, comprising of cores extend through a common cladding. The cores are doped so as to create, in conjunction with the cladding, a plurality of waveguides having the same wavelength shift over time is response to a change in gas diffusion, but different wavelength shifts in response to changes in other parameters.

Abstract: A twin core fiber for sensor applications is developed. It is particularly useful in de-coupling the strain and temperature and thus obtaining both measurement parameters at the same time and location. It is also particularly useful for measuring the temperature in a high humidity environment. The twin core fiber has two cores and each of the cores having a different dopant regime. Also, each of the cores includes a grating having substantially the same grating period.

Abstract: A twin core fiber for sensor applications is developed. It is particularly useful in de-coupling the strain and temperature and thus obtaining both measurement parameters at the same time and location. It is also particularly useful for measuring the temperature in a high humidity environment. The twin core fiber has two cores and each of the cores having a different dopant regime. Also, each of the cores includes a grating having substantially the same grating period.

Abstract: A method of forming an optical fiber. A solution (12) is prepared in which are dissolved both a ladder siloxane and one or more dopants which are to be incorporated into the final silica or silicate glass. The solution is drawn into the interior of a silica tube (10) and is left as a coating (26) on the inside wall. The solvent is evaporated, and the rigid coating is cured at 150.degree. C. The filling and curing process may be repeated for multiple layers. The cured coating is then oxidized and fused into doped silica. The resultant tube preform is collapsed and drawn into a fiber. The method allows the introduction of nearly arbitrary constituents into the silica, including glass-forming elements and low-level dopants. The core-cladding interface is improved if a layer of glass-forming soot particles (28) is first deposited and the liquid is soaked into and over the soot.

Abstract: A glass body having a graded (substantially Gaussian) index profile is produced by a process that comprises providing a doped porous body (e.g., having a uniform dopant distribution), heat treating the porous body in a halogen-containing atmosphere, and consolidating the porous body into the glass body. The heat treatment removes a predetermined portion of the dopant from the porous body, such that the radial dopant profile in the glass body differs from the initial profile in the porous body, and such that the Gaussian index profile results. Exemplarily, the porous body is a uniformly germania-doped, VAD-produced, high-silica rod having radially decreasing density, and the heat treatment comprises an 8-hour densification soak at 1300.degree. C. in 20% Cl, 80% He. In a preferred embodiment, silica overcladding is deposited on a graded index core rod produced according to the invention, and fiber drawn from the resulting composite glass body.

Abstract: A technique for fabricating a lightguide soot-boule. Gaseous reactants are directed through an inner tube of a torch having a plurality of coaxially aligned tubes. A glassy soot is formed at the output of the torch by a flame hydrolysis reaction and at least a portion of the soot is deposited on a forming soot-boule. The inner tube may be axially moved during the soot deposition process to alter or maintain the refractive index of the boule.

Abstract: A high frequency induction furnace (10) for reflowing a portion of a lightguide preform (44) in order to draw a fiber (52) therefrom. The furnace (10) has a centrally located tubular susceptor (34) therein having a thin coating of the preform material (e.g., silica) on at least a portion of the inside surface thereof. A cylinder (62) is positioned in concentric, spaced relation about the susceptor (34) and is surrounded by an insulating grain (36). A high frequency coil (38) is energized to couple its electromagnetic field to the susceptor (34) to heat and reflow a portion of the preform (44) in order to draw the fiber (52) therefrom. The thin coating prevents contaminating particulates from migrating from small cracks in the inside surface of the susceptor (34) onto the preform (44) while the cylinder (62) prevents small particulate emanating from the insulating grain (36) from being drawn through larger cracks in the susceptor and onto the preform and/or the fiber 52.

Abstract: A vapor-phase axial deposition system (5) for fabricating a lightguide soot boule (16). The system (5) is comprised of a short cylindrical housing (10) having end plates (26--26) affixed thereto. A starting member (58) is radially directed into the central portion of the housing (10) and a torch (12) is activated to direct a stream of glassy soot thereat. The member (58) is simultaneously rotated and withdrawn from the housing (10) as a cylindrical, porous, soot boule is formed on the end thereof. The housing (10) having a substantially two-dimensional character eliminates secondary gas flow within the housing (10) resulting in enhanced deposition rates and repeatability.

Abstract: A reactant deposition torch (10) has a plurality of concentric glass tubes (16, 18, 20, 24 and 26). Various gases pass through the tubes (18, 20, 24 and 26) while particle producing reactants pass through the inner tube (16). The concentricity of the tubes is accurately maintained by a plurality of precision machined splines located on the outer periphery of the inner and intermediate tubes (16, 18, 20 and 24). Additionally, the inner tube (16) is movable in the axial direction during the deposition process to controllably alter the amount of reactant to be deposited.

Abstract: A method of practicing the MCVD process is disclosed. In the inventive process, the core deposition is completed prior to completion of the cladding. An intermediate preform structure with a core-to-clad ratio greater than that desired in the ultimate fiber is consequently obtained. Subsequent to internal core deposition, additional material is added externally to complete the cladding thereby yielding an optical fiber preform with the desired core-to-clad ratio.