Robert D. Maurer

RADIATION LOSSES IN GLASS OPTICAL WAVEGUIDES

Measurements show that single‐mode waveguides can be constructed which have radiation losses of about 7 dB/km—very close to the intrinsic material scattering loss. These waveguides, with total losses between 60 and 70 dB/km, have permitted the measurement of bending losses which become dominant at radii of curvature of a few centimeters. An approximate theory based on bending a rectangular guide appears to represent the circular waveguide results very well.

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.

Glass fibers for optical communications

Glass optical waveguides with attenuations below 20 dB/km have made possible a new approach to optical communications. These glass fibers satisfy requirements for transmission over kilometer lengths with experimental systems utilizing existing devices for sources and detectors. The realization of material and fabrication advances necessary for this accomplishment are the topic of this paper. Basic theoretical principles are introduced in a review fashion. The application of these principles in choice of materials and fabrication is described. Results in fiber performance following this framework are given in a section on evaluation, which includes information capacity, attenuation, and some environmental requirements. Preliminary experiments in bundling and cabling are discussed, followed by concluding remarks.

Tensile strength and fatigue of optical fibers

A method is presented for analyzing laboratory measurements of tensile strength and fatigue failure rates of glass fibers. This method provides the physical basis for extrapolating laboratory data to the multikilometer lengths and long lifetimes which will be characteristic of field use of optical fibers in telecommunication systems.

Crystal Nucleation in a Glass Containing Titania

The mechanism of crystal nucleation in a titania‐magnesia‐alumina‐silica glass has been studied by light scattering. Predominantly isotropic scattering centers become anisotropic during the initial crystallization process. This is interpreted as crystal nucleation within glassy concentrations fluctuation of titania. Titania‐containing glasses nucleate readily because of the tendency of titania to segregate in amorphous regions which are more unstable toward crystallization than the original homogeneous glass. The data can be described by a model of scattering by a center surrounded by a region of polarizability of opposite sign. This model is utilized to obtain measurements of the crystallization rate and average crystal size.

Nucleation and Growth in a Photosensitive Glass

The nucleation and growth of particles can be independently determined by simultaneous measurement of two quantities having different functional dependencies upon particle number and size. Light scattering and optical absorption are the two quantities chosen to observe the precipitation kinetics of a gold colloid. When an exposed photosensitive glass is treated at high temperatures, gold precipitates on a fixed number of sites. On the other hand, increasing the concentration of reactants causes spontaneous gold precipitation in which growth sites form continuously throughout the precipitation process. This indicates that the photosensitive reaction forms nuclei in a supersaturated solution which cannot nucleate spontaneously. In agreement with this, the experiment shows that the number of growth sites increases with exposure while the growth rate is the same for all exposures. Finally, assuming that the particles are spheres, absolute values are derived for the initial change of particle size with time an...

Strength of fiber optical waveguides

Optical waveguides must withstand tensile stresses over kilometers of length where one flaw can be fatal. The strength of long lengths has not been previously studied but this paper presents a few preliminary data and compares them with the more abundant data on short lengths. Weibull statistics provide the logical basis for this comparison. The same Weibull constants adequately describe the long‐length data and the low‐strength portion of the short‐length data. Flaws in 10–100 km lengths, therefore, seem to be of the same class as those found in relatively short gage lengths.

Optical attenuation in titania-silica glasses

Abstract The bleaching of bulk titania-silica glasses in the annealing temperature range is investigated. The sample-size kinetics can be predicted from the hydrogen diffusion coefficient. Hydrogen gas is evolved from both titania-silica and silica glass but in larger amount from the former. In the bleaching process, Ti 3+ ions disappear from the titania-silica glass. These results are consistent with the coloration caused by Ti 3+ which is oxidized by OH- in the glass to produce gaseous hydrogen.

Effect of Neutron- and Gamma-Radiation on Glass Optical Waveguides

Multimode glass optical waveguides with very low attenuation have been made by laboratory techniques. A desirable property of optical waveguides is the resistance to the environmental hazard of nuclear (neutron and gamma) radiation. Experiments were performed on the change in attenuation of the optical waveguides with cumulative 14 MeV neutron irradiation and with /sup 60/Co gamms irradiation. The results of these experiments are presented. (AlP)

Theory of backscattering effects in waveguides.

Associated with a signal transmitted down a waveguide are multiple back and forth scatterings. These produce a delayed decaying interference trailing a sharp signal pulse. An analytical description of this phenomenon enables an estimate of its effect on an optical waveguides information-carrying capacity. For the example of a signal-to-interference ratio of 100 in a 1-km fiber of 20-dB attenuation, a bit rate limitation occurs when the fractional backscattered power captured per unit length exceeds 1.3 dB/km.