Paul R. Foy

Low-loss rare earth doped single-mode fiber by sol-gel method

Abstract Using a sol-gel process for rare-earth ions doping, a minimum optical loss of less than 2 dB/km in the region of 1.15μm has been reproducibly achieved in Er 3+ doped Al 2 O 3 ue5f8SiO 2 glass single-mode fibers. A wide range of rare earth doping concentrations was successfully introduced into fibers using this technique. In the sol-gel dipcoating to deposit a thick film, the key to achievement of low loss fiber was found to depend critically on a process capable of providing a consistently crack-free film.

Enhanced fatigue and aging resistance using reactive powders in the optical fiber buffer coating

We have shown in previous work that the addition of small quantities of colloidal silica to the UV- curable polymer coating of fused silica optical fiber causes a dramatic improvement in the fatigue and aging resistance both in aqueous and in constant humidity environments. The presence of silica in the coating inhibits the mechanisms responsible for the surface roughening that causes the fatigue knee and strength degradation during zero-stress aging. This work presents results which show the effect of higher concentrations of the silica additive (6 wt%) and of an adhesion promoting agent on both the rheological properties of the polymer coating and the fatigue and zero-stress aging behavior of the fiber. Viscosity measurements show thixotropic behavior which indicates that the silica particles tend to form a network structure in the prepolymer. Filtration of the prepolymer to remove large particles is hampered by this phenomenon. The fiber coated with the silica-containing polymer exhibits substantial improvement in the long term mechanical reliability compared to a reference fiber without additive in the coating.

Optical properties of hollow calcium aluminate glass waveguides.

Calcium aluminate glass has a refractive index less than 1 at 10.6 µ, and therefore it is a good candidate for a hollow fiber for the transmission of CO(2) laser energy. We have drawn hollow calcium aluminate glass fibers with inner diameters ranging from 380 to 500 µ. The loss for our 500-µm inner-diameter hollow glass fibers measured at 10.6 µm is 8.6 dB/m.

Organically modified silicate coatings for optical fibers

Three kinds of UV-curable organically modified silicates have been prepared to be used as protective coatings for optical fibers. The synthesis involves the reaction of the thiol group of 3-mercaptopropyl-trimethoxysilane with a C equals C bond in one of the acrylic groups of three commercially available aliphatic triacrylates. The methoxysilyl groups of the synthesized diacrylate methoxysilanes were subjected to hydrolysis and condensation to form Si-O-Si units. Transparent, viscous, solvent-free resins were obtained that hardened in seconds when exposed to UV radiation. The coating derived from the reaction with glycerol propoxy triacrylate (GPTA) proved to adhere the best of the three to both plastic and glass substrates. It was then tested as a protective coating for silica fibers. Reliability tests were carried out including bending strength and fatigue tests at pH 7 and 10. The results show improved water resistance of the coated fiber in neutral conditions.

Preliminary study of fiber drawing of AlF3-based glasses

Abstract Although AlF 3 -based glasses have shown superior chemical durability and mechanical strength relative to ZrF 4 -based glasses, devitrification problems near the drawing temperature have limited their fiber applications. We have investigated the effect of atmosphere, particularly moisture, on the surface crystallization during the fiber drawing of these glasses. The crystallization behavior has been monitored by optical microscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) techniques. Preforms of AlF 3 -based glasses have also been drawn into long fibers in a tower enclosed by a unique three-stage vertical glove box in which the moisture levels are maintained below 1 ppm.

Mechanical behavior of silica optical fibers coated with low-index low-surface energy perfluorinated polymer

Two formulations based on perfluorinated polymer were prepared for use as UV-curable optical cladding for silica fibers. In the first formulation an adhesion promoting agent based on fluoroacrylate resin was synthesized and mixed with the experimental product Defensa 7702++ in order to promote wetting and chemical adhesion to the silica fibers. In the second formulation, wetting and physical adhesion between the liquid coating and the silica fibers were achieved by increasing the viscosity of the starting coating by addition of unsaturated perfluorinated polymer into Defensa. Both formulations were used as primary coatings on dual coated silica optical fibers. The mechanical behavior of the formulations was characterized by the strip test, the pull-out test and zero stress aging in 90 degrees Celsius pH 7 buffer. The results show that both formulations exhibit better wetting-adhesion characteristics than unmodified starting coating and that the strength degradation during zero- stress aging was lower for the fiber coated with the formulation of higher viscosity.

Loss mechanism analysis of tellurium halide glass optical fibers

New IR glasses transmitting from 1 to 20 im and having low loss potentiality in the 8- 12 pm region have been obtained in the Te-Br-Se and Te-I-Se systems. Single index fibers have been drawn from rods and the attenuation measuredin normal atmospheric conditions. The influence ofthe band gap absorption mechanism appears to be very critical as well as the addition ofelements such as Bi which seems to improve the mechnical properties.

Fabrication Of Heavy Metal Fluoride Glass Fibers Containing Ultra Low Levels Of Oxygen And Water

Although heavy metal fluoride (HMF) glasses potentially offer high intrinsic transparency in the infrared spectral region, losses associated with extrinsic impurity absorption and scattering presently limit their uses in practical applications. This paper focuses on the design of an environmental control chamber and draw facility for minimizing water and oxygen contamination during the drawing of fluoride glass optical fiber. A vertical glove box arrangement of novel design encloses the draw tower area in which the preform and bare optical fiber are susceptible to moisture and water absorption. This area includes the preform chuck, the draw furnace, the fiber diameter monitor, the fiber coating equipment, and diagnostic instrumentation for measuring fiber tension and temperature. Plans for evaluation of various drawing techniques including rf/preform, resistance/preform, and rf/crucible are described, along with fiber coating techniques including oxide and non-oxide glass overcladding and UV-curable polymers.