Plastic-clad chalcogenide glass fibers

Easy handling flexible mid-IR light conductors have been made of GeAsSe chalcogenide glass fibers coated with polyolefin. Optical transmission level is about 10 dB/m in the 4 - 11 micron band. Few watts of CO₂ laser power may be transmitted.     

Nanoindentation of glass wool fibers

The nanoindentation technique is used to analyze the depth dependence of the hardness and the reduced elastic modulus of bulk glasses and glass wool fibers (4-12 μm in diameter) of calcium aluminosilicate composition. In spite of the fiber geometry and the delicate sample mounting-technique, nanoindentation proves to be a relatively accurate method that provides reproducible data for both hardness (H) and reduced elastic modulus (E_r) of thin glass fibers. It is found that H and E_r are generally lower for the fiber than for the bulk sample. Within a given fiber, both H and E_r are approximately constant with increasing indentation depth. However, both of these parameters decrease with diminishing fiber diameter. This trend is attributed to an increase of the free volume of the fibers with decreasing fiber diameter, i.e. to an increase of the fictive temperature.     

Chromium phase behavior in a multi-component borosilicate glass melt

This paper reports the phase behavior of a multi-component borosilicate glass melt with 0–3 mass% Cr₂O₃ at 800–1500 °C in equilibrium with air. Both upper and lower liquidus temperatures were observed. When the temperature was between the upper and lower liquidus temperatures, eskolaite (Cr₂O₃) formed in melts with >2 mass% Cr₂O₃. Below the lower liquidus temperature, a dispersed chromate phase appeared in the melt that eventually became macroscopically segregated. The chemical durability of the glasses was virtually unaffected by chromium concentration. The particular glass studied was prototypic for vitrifying high-Cr high-level radioactive wastes stored in underground tanks at the Hanford site. The results suggest a significant potential cost benefit for Hanford tank waste cleanup through increased waste solubility in glass.     

Interaction of organosilanes with glass fibers

Systematic reaction of a glass surface with monofunctional organosilanes can be achieved by multiple coat-cure treatments. A gradual decrease in the polarity of the glass surface, measured by its wetting properties, monitors this reaction. A saturated surface results after ten coat-cure treatments, yielding a surface whose hydrogen bond component to the work of adhesion against water (W_H2O^H)=25 ergs/cm². This value is in contrast with conventional trifunctional organosilane treated surfaces having W_H2O^H ≈ 50 ergs/cm². The importance of controlling the energetics of the glass surface is discussed for a variety of processes.     

Water-vapor adsorption on calcium-boroaluminosilicate glass fibers

The water-vapor adsorption isotherms of E-glass fibers were measured as a function of their aging in humid and aqueous environments, and of the amount of B₂O₃ in the glass composition. The specific surface area for adsorption was determined, independently, using inert gas adsorption, while X-ray photoelectron spectroscopy (XPS) was used to characterize the surface composition. In contrast to silica, where submonolayer coverage is observed in the low pressure range of the isotherm, these multicomponent glasses adsorbed the equivalent of 1 to 3 layers of water. The shape of the isotherms revealed that multilayer adsorption of water occurs on the fiber surfaces before the formation of a complete monolayer, i.e., water adsorption on these glass fibers was non-uniform, in general. It was found that the aging of these fibers in humid or aqueous environments greatly enhanced their capacity to adsorb water at low pressure, but the B₂O₃ content of the fibers had little effect.     

Crystallization of glass fibers of the system Zn---Fe---Mn---oxides---alumina---silica

A glass composition based on the Zn---Al---silicate ternary system was modified with the addition of Fe and Mn oxides in order to test its feasibility to be drawn as alkaline-corrosion resistant glass fibers.

Their devitrification trend was studied, under dynamic thermal conditions, in order to define after which ternary diagram the resulting phases could be best described.

A beta-quartz structured silica rich phase, alpha-willemite and magnetite have been detected both in the fibers and in the bulk mass after crystallization. However, the differential thermal analysis patterns and the microstructures of the samples revealed very noticeable differences.     

Source of optical loss in tellurite glass fibers

Non-silica-based optical fibers generally suffer from high optical loss and low strength, whereas they have other optical properties superior to that of silica for certain device applications. Tellurite glasses offer one of the best compromises among optical, mechanical, and processing properties. The goal of this study was to achieve low loss tellurite fibers for active and non-linear applications. In this paper, single mode tellurite fibers doped with KNbO₃ were made with losses varying from 1.3 to 6 dB/m. The sources of loss were striation, dust particles, and bubbles. The decrease of striation was observed by employing lower pouring temperature, and the increase of fiber strength was achieved by hydrochloric acid etching of preform.     

Quantitative calculation of immiscibility ranges of multi-component borate, silicate and borosilicate glass systems

Using the phase diagram data of binary systems, in this paper a great number of binary immiscibility equations have been calculated by computer. Based on those equations, the formulae for the calculation of ternary and multi-component systems have been derived. Generally, the results of the calculation agree with the experimental data.     

Tm-doped aluminate glass fibers for S-band optical amplification

Thulium-doped fiber amplifiers (TDFAs) have been proposed as practical devices for the amplification of light signals in the so-called S-band (1460–1530 nm) of the transparency window of standard telecommunications fiber. As the quantum efficiency of the desired ³H₄ → ³F₄ luminescence of Tm³⁺ is adversely affected by non-radiative decay when high maximum phonon energy (MPE) host glasses are used, a practical TDFA requires an active fiber made from a glass with intermediate to low MPE. We have explored the possibility of using aluminate fibers for this application, as bulk samples of Tm-doped alkaline earth aluminate glass are characterized by a MPE of 780 cm⁻¹ and a quantum efficiency for the 1460 nm fluorescence of ∼35%. Despite the high devitrification tendency of aluminate glass, pure aluminate core fibers with minimum losses of ∼0.5 dB/m have been successfully fabricated by the rod-in-tube technique using viscosity- and expansion-matched alkaline earth aluminosilicate cladding glasses.     

Synthesis and characterization of boron silicon oxycarbide glass fibers

Boron silicon oxycarbide fiber mats have been obtained through pyrolysis in inert atmosphere of sol–gel derived hybrid materials. The characterization of the preceramic hybrid fibers and the pyrolysis process reveals different boron incorporation depending on the composition. The ceramic conversion involves a series of reactions governed by the presence of the mixed bonds that implies larger phase segregation and higher graphite nanodomain size with the decrease of the number of borosiloxane bridges in the preceramic material. The formation of a mixed structure, where both Si and B are taking part on the ceramic network occurs with the excess of B that precipitates as boric acid in the surface of the fibers. These precipitates can cause pores in the surface of the pyrolyzed fiber.     

Influence of drawing temperature on the strength of fluoride glass fibers

The tensile strength of fluorozirconate glass fibers was measured as a function of fiber drawing temperature, and strengths ranging from 60–220 MPa were observed. Statistical analysis of the strength data points to a bimodal behavior in the fibers drawn at high temperatures, while the mode of fracture is essentially unimodal for fibers drawn at lower temperatures. SEM examination of the fibers drawn at high temperatures revealed the presence of crystals in the fibers, and these crystals were associated with flaws which gave rise to the observed low strength distribution.     

Compound glass preparation for optical fibers using Brazilian natural quartz

We present studies related to the investigation of Brazilian natural quartz as a basic raw material for production of optical multicomponent glasses for optical fibers. The work includes characterization and selection of quartz, preparation, the melting process and glass characterization.     

Fabrication, spectroscopy and laser performance of Nd-doped lead-silicate glass fibers

The fabrication of a highly efficient Nd³⁺-doped single-mode fiber laser operating at 1.06 μm is described. The Nd₃₊ is introduced by doping Nd₂O₃ into a multicomponent (flint) lead-silicate glass host, Schott commercial optical glass F7. A fabrication technique for doping rare-earth evenly into commercial optical glasses is demostrated. Spectroscopic properties relevant to laser operation in the Nd³⁺-doped lead-silicate glass fibers were measured and the influence of Pb₂₊ ions on the spectral properties was analyzed. Owing to the long lifetime and large absorption and emission cross-sections of Nd₃₊ in this lead-silicate glass host, a high-performance Nd³⁺-doped lead-silicate fibre laser device operating at 1.06 μm has been successfully demonstrated.     

Extrusion of chalcogenide glass preforms and drawing to multimode optical fibers

We report on viscosity of a Ge₁₇As₁₈Se₆₅ glass over the temperature range of 280-420 °C and the successful co-extrusion and fiber-drawing of two chalcogenide glass boules to form a core/clad. pair. The co-extrusion produces a preform with optimum diameter stability and core/clad. glass ratio, and minimum defects at the core/clad. interface in the middle 120-200 mm region of a 270 mm long preform. Core/clad. fiber is drawn successfully from the extruded preform. An optical loss of 1.7 dB m⁻¹ at 1666 cm⁻¹ (6.0 μm) and 6.7 dB m⁻¹ at 6649 cm⁻¹ (1.55 μm) is reported.     

Preform fabrication and drawing of KNbO3 modified tellurite glass fibers

For fiberization of tellurite glasses the 70TeO₂–25ZnO–5Na₂O composition is selected based on its good thermal stability and refractive index compatibility with most of the ferroelectric oxides. A modified built-in casting method is used to fabricate preforms. The fiber drawn by the rod-in-tube technique consists of two layers of cladding glass and a core with 5 mol% ferroelectric KNbO₃. In this study we also address the low mechanical strength problem with tellurite glass fibers, by subjecting the preforms to polishing and wet chemical etching. Apart from the fabrication methods, we also report here a selective core heat-treatment and ferroelectric phase crystallization in a low dimensional system.     

Measurement of the refractive index of glass fibers by the Christiansen-Shelyubskii method

The Christiansen principle was employed to measure the refractive index of borosilicate glass fibers (13–41 μm diameter) over the visible range. The refractive index for glass fibers at 589.3 nm was measured by temperature and wavelength scan and values obtained were in close agreement. The refractive index for glass fibers as a function of wavelength was measured to an accuracy of < 10⁻⁴. The uniformity of the refractive index for a bundle of fibers of slightly different diameter was calculated using the modified Shelyubskii method and compared to experimental values. Theoretical calculations of the transmission by the present work suggest that, for high optical clarity and transmission of Christiansen cell (or transparent composite consisting of glass fiber and polymer), the refractive index must be controlled to the fifth decimal place. For example, the maximum transmission of a fiber/liquid mixture cell at 25°C can increase from 89 to 97% when the standard deviation is reduced from 13 × 10⁻⁵ to 9 × 10⁻⁵.     

Chalcogenide infrared As2−xSe3+x glass fibers

Chalcogenide glasses As_2?xSe_3+x have been prepared. A new technique of preparing the raw material and subsequently drawing fibers has been developed in order to avoid the formation of oxygen compounds. The fibers have been drawn by the crucible and rod method from oxygen free raw material inside an Ar atmosphere glove box. The fibers drawn to date have a diameter of 50–500 μm and lengths of several meters. Preliminary attenuation measurements indicate that the attenuation is better than 0.1 dB/cm at 10.6 μm. The attenuation is not affected even when the fiber is bent to a circular radius of 2 cm. By improving the preparation of materials and the drawing technique, we expect to achieve a better transmission.     

Infrared fibers based on Te-As-Se glass system with low optical losses

Unclad optical fibers based on high-purity Te-As-Se glasses prepared by chemical and physical methods of purification have been drawn. The optical, thermal and mechanical properties of glasses and fibers were investigated. The minimum optical losses were 0.07 dB/m at 7.3 μm for Te₂₅As₄₀Se₃₅ glass fiber and 0.04 dB/m at 6.7 μm for Te₂₀As₃₀Se₅₀ glass fiber. Sixty five percent of input power of a tunable CO₂ laser emitting at 9.3 μm was transmitted through a 1 m long fiber with diameter of 900 μm.     

Mechanical properties of optical glass fibers damaged by nanoindentation and water ageing

Mechanical properties of optical glass fibers are strongly influenced by cracks on glass surface. Cracks may be generated during manufacture and handling. The chemo-mechanical effect due to water may decrease the response of glass fibers because of surface degradation. In this work glass fibers were aged in a wet chamber at humidity of 85% in temperatures lower than 90 °C, during seven weeks. After being aged, the fibers were submitted to tension tests. The fracture loads were investigated by Weibull statistics. An increase in dynamic fatigue parameter was observed. Surface analysis by AFM indicated smooth surfaces. Small cracks on optical fiber glass surface were made by Vickers indentation and nanoindentation using a Berkovich indenter. A decrease on applied load to fracture indicates that the fiber was damaged by indentation. The influence of indentation load was investigated. As the deformation rate was very low during tension tests, the cracks grow during the test and the fiber fracture at loads lower than for not indented fibers. The effect of water and small indentation fracture on glass is discussed considering the surface damage induced by both methods. The size of the cracks from the different indentations and ageing are estimated.     

Effect of some manufacturing conditions on the optical loss of compound glass fibers

The effect of the use of platinum crucibles and gas flow at glass melting and fiber drawing on the optical loss of compound silicate glass fibers have been investigated for the purpose of obtaining low-loss optical fibers. In concentrations of more than 50 ppm, platinum impurity dissolved into the glass from a platinum crucible increases the optical loss. The flow of oxidizing gas decreases the optical loss due to the Fe²⁺ ions. The flow of dry gas also decreases the absorption loss at 0.96 μm by water. The improvement based on these results lowers the total loss of clad fibers to 9.5 dB/km at 0.84 μm and 15 dB/km at 1.06 μm.