Peter C. Schultz

On the ultimate lower limit of attenuation in glass optical waveguides

The fabrication of an extremely‐low‐loss glass optical waveguide, having as little as 4 dB/km total attenuation, has allowed interpretation of the absorption spectrum to a much greater degree than previously possible. It is shown that, beyond about 700 nm, intrinsic ultraviolet absorption will have no effect. Between 700 and 1100 nm, all absorption can be accounted for on the basis of OH to within ±0.7 dB/km. Marked reduction of the water content will leave the scattering as the major loss mechanism, thereby permitting total attenuations of about 2 dB/km.

Investigation of TiO2SiO2 glasses by X-ray absorption spectroscopy☆

The coordination and nearest-neighbor bond distances of Ti in a series of TiO2SiO2 glasses have been quantitatively determined using a combination of XANES and EXAFS measurements about the Ti K-edge at 4966 eV. The glasses covering the range 0.012 to 14.7 wt% TiO2 were prepared by flame hydrolysis of predetermined mixtures of SiCl4 and TiCl4 vapors. At TiO2 concentrations below ∼0.05 wt%, Ti is found in a rutile-like octahedral coordination. With increased TiO2 content in the glass, a two-site model applies, in which Ti is found predominately in a fourfold site. About ∼9 wt% TiO2, t6he sixfold/fourfold ratio increases appreciably and eventually at ∼15 wt% TiO2, crystalline TiO2 segregates out as a second phase. The average TiOSi bond angle in these glasses was estimated to be ∼159 ° which is slightly larger than the most probable value of 152 degrees for SiOSi in vitreous SiO2. Within the accuracy of the edge shift measurements all Ti in the glass is in 4+ valence. Finally, various physical properties such as density, optical transparency and thermal expansion are correlated in light of the new structural data for this interesting binary silicate glass system.

Relationship between composition, density and refractive index for germania silica glasses

Abstract The density and the refractive index for various compositions of binary SiO2GeO2 glass prepared by a flame deposition technique, similar to that used to make low-loss optical waveguides, have been measured by standard Archimedes method and the Becke line method, respectively. The density as a function of composition is calculated considering the effective volume of the ions contained in the glass to be invariant. The refractive index as a function of composition is also calculated, based on the Lorenz-Lorenz equation, by computing the electronic polarizability of fused silica and germania. All calculated results are in good agreement with the observed data.

Coordination of Ti in TiO2SiO2 glass by X-ray absorption spectroscopy☆

Abstract Evidence from both the extended X-ray absorption fine structure (EXAFS) and near-edge regions of the Ti K-edge X-ray absorption spectrum for TiO2SiO2 glasses has been examined to determine the coordination geometry of the Ti4+ ion. It is concluded that this geometry is primarily a four-fold coordination, with a small fraction of the Ti4+ ions having six-fold coordination and a longer TiO bond length. The ratio of six-fold to four-fold coordination is seen to increase with increased TiO2 content in the glass.

Compositional effects on the radiation response of Ge-doped silica-core optical fiber waveguides

The effect of variations in the Ge, B, P, and OH content on the radiation response of Ge-doped silica-core optical fiber waveguides has been measured at 0.82 and 1.3 microm. It has been established that variations in neither OH content nor Ge concentration affect the response of these fibers. B doping increases the loss at short times following pulsed irradiation, whereas P suppresses the intense Ge-related transient absorption at both 0.82 and 1.3 microm while inhibiting long-term recovery. Since there is a minimum in the induced loss near 1.1-1.2 microm in P-doped fibers, the damage at 1.55 microm is significantly higher than that at 1.3 microm.

Progress in optical waveguide process and materials

A brief up-to-date review of the main technologies currently used in the fabrication of optical waveguides and a report on recent process and material advances that affect fiber performance and/or cost are presented. The processes reviewed include vapor phase oxidation as well as direct-melt. Rapid technical progress continues to be made on numerous processes used to fabricate single-mode and multimode fibers. Process strengths are being verified and utilized, and many process problems minimized and eliminated. As fiber performance differences between processes become smaller, manufacturing cost considerations become increasingly important.

Silica-rich glasses in the TiO2Al2O3SiO2 system

Abstract Ternary glasses in the TiO2Al2O3SiO2 system have received only very limited attention, although both Al2O3SiO2 and TiO2SiO2 glasses have been extensively studied and exhibit interesting properties. In this paper, the ternary glass-forming region and physical properties are described. Unusual volume contraction was found for some compositions which allowed strengthening by surface compression.

Vapor Phase Materials and Processes for Glass Optical Waveguides

The first low loss glass optical waveguide fiber, 1 having an attenuation of 17 dB/km, was drawn from a glass blank, or preform, which had been fabricated by a vapor phase process. This success ultimately led to extensive technical efforts worldwide to develop vapor phase processes capable of providing practical glass fibers for the now burgeoning optical communications industry. This has proved to be a very effective and versatile fabrication approach. Single mode, step-index multimode, and graded-index multimode fibers have all been made by vapor phase techniques. Multimode fibers have been fabricated with bandwidths as high as 3 GHz, 2 and with total attenuations as low as 0. 5 dB/km, bordering on the intrinsic limits of the glasses used. 3 Of the more than 56 operating optical waveguide communication systems worldwide, 4 at least 50 use glass fibers made by a vapor phase process. Economic viability of glass fiber communications appears to be rapidly approaching as fabrication technology moves from the research laboratory into the production phase and further process improvements are made. Numerous important variations on vapor phase processes have been developed during the past eight years to achieve such impressive results. The purpose of this paper is to provide a tutorial and contemporaneous review of the key vapor processes under development.

Comparative Examination by EXAFS and WAXS of GeO2- SiO2 Glasses

Germania-silica glasses have been used in the manufacture of low attenuation optical waveguides for communication [1]. Various measurements have been conducted on this type of glass including IR spectra [2], refractive indices and IR spectra [3], linear expansion coefficients and viscosities [4], composition, density and refractive index [5] and UV absorption spectra [6]. The measurements reported here extend the observations to structural determination by EXAFS and WAXS.