Donald A. Clark

Fatigue behavior of silica fibers with different defects

Comparison of high-speed strength data for weak (abraded, contaminated and indented) and pristine fibers was performed. It was shown that fatigue behavior of abraded fiber practically coincides with that of the fiber contaminated by zirconia powder and is close to that of indented fiber. The fatigue parameters obtained for strong pristine fiber cannot be used to obtain the correct prediction of fiber strength after proof testing. A two-region power law model was used for mathematical description of these results and the fatigue parameters for three types of weak fibers were obtained.

69.3: A Mechanics Framework for Ion‐Exchanged Cover Glass with a Deep Compression Layer

A cover glass that is capable of having a deep ion exchange compression layer enables one to tailor the glass to the intended device application. Key to this effort is having a glass mechanics framework that includes resistance to visible and strength-limiting contact damage as well as maintaining sufficient strength to survive localized glass flexing during contact events.

Effect of environmental conditions on fatigue of weak silica-clad optical fibers

Static fatigue of bare indented fibers in different environments was studied. It was found that the n-value in different pH-solutions did not significantly change and was higher than that for strong fibers and lower than that for bulk samples in similar conditions. All lifetime reduction with a pH increase was due to a change of the B-value. The results obtained were used for evaluation of the lifetime of weak fibers for different service environments.

An indentation method for creating reproducible proof-stress level flaws in commercial optical fiber

A technique was developed for obtaining proof-stress level flaws in commercial optical fiber with low variability in strength. It involves a novel method for stabilizing and protecting the round fiber prior to indentation. Indentation was performed in an automated fashion using a nano-indenter equipped with a cube-corner indenter. A Weibull modulus of 50 was achieved with a value of 100 over the lower portion of the distribution. This method will be useful in static fatigue testing of fiber with proof test level flaws.

Analysis of single mode bent fiber failure under high power conditions

Optical fiber networks are being developed that require higher optical power levels. Examples include long haul communication with Raman amplification and fiber to the premises. Previous studies indicate that tightly bent optical fiber can mechanically fail when exposed to high optical power levels. In an extreme case where fiber is sharply bent and subjected to a power level of 1 to 2 W in the near-infrared wavelength window, optical fiber can fail in minutes. It also has been shown that time to failure decreases with increasing bend stress and optical power. This study is a further investigation of the physical events leading to failure. Previously we demonstrated that the optical signal that escapes the core of bent fiber passes into the coating, where a small amount is absorbed and converted to heat. As a result the coating can be heated to significant temperatures resulting in degradation over time. This paper focuses on several key aspects of the failure kinetics associated with bent fiber under high power. As a result of bending, optical power leaked from the core is distributed in the glass cladding and polymer coating. We have modeled this power distribution and compared it with measured temperature profiles in the coating. The results show that this redistribution of the power is key to establishing the distribution of temperature in the coating and ensuing degradation. This understanding is used to design glass and coating solutions for inhibiting this potential failure mode.

Analysis of optical fiber failures under bending and high power

The failure of tightly bent optical fiber under high optical power is observed dynamically with fine time resolution and explained in terms of the behavior of the polymer coating and underlying glass. An abrupt rise in coating temperature stimulates the viscoelastic deformation of the glass. The abrupt bending of the glass is explained by the ability of highly quenched silica to deform at low temperatures. There is no evidence of thermal runaway of the glass core. Coating decomposition is self limiting with no visible flame.