Passivated Optical Fibers For Harsh Environments

Glass optical fibers have high strengths but under tensile stress and in the presence of aqueous media their strength diminishes through fatigue. Analogous to the semiconductor field, where the electronic properties of chips are protected by passivating coatings, optical fiber strength can be protected by passivating the glass surface. Optical fibers have been developed with such a primary coating/cladding, namely HCS R fibers. These fibers not only have high initial strength but also have excellent fatigue resistance. Their stability to environmental exposure is demonstrated by comparing static fatigue results for exposure to hot water, to boiling water, to steam and to acid/base solutions ranging from 10 M acid to 10 M base to results obtained in ambient water. HCS fibers maintain high static fatigue parameters at elevated temperatures and exposure to these temperatures under low stress does not change their fatigue behavior. Except at the extremes in pH, the static fatigue behavior is unchanged across the acid/base spectrum. This insensitivity to environmental changes and the good fit of the data to the power law model permits the prediction of lifetimes for long term exposure to aqueous environments.