Electron Paramagnetic Resonance Study of the Hermetic Carbon Coated Optical Fiber

Recently, a thin carbon film deposited on the surface of silica optical fibers has been shown to improve the fiber's resistance to static fatigue and hydrogen permeation. The carbon film is characterized by electron paramagnetic resonance spectroscopy. A single symmetrical resonance is observed, centered at the g value of 2.002. The lineshape is Lorentzian, suggesting spin delocalization. Intensity measurements ranging from 4K - 800K suggest that both conduction electrons and localized spin centers contribute to the spin resonance. The localized spin centers may arise from point defects in the carbon film. The results are discussed in terms of specific structural models for the defects.