Transient Radiation Effects in Low-Loss Optical Waveguides

Radiation-induced effects in low loss optical waveguides have been studied to determine parameters affecting the use of these materials in plasma diagnostic instrumentation operating in severe radiation environments. Radiation-induced luminescence of fibers was shown to result from the Cerenkov process occurring within the fibers. Both spectral data and angular dependence of luminescence were used to verify the Cerenkov effect. Absolute magnitude of luminescence data were obtained. Different fiber types were shown to exhibit comparable luminescence output. Radiation-induced absorption was measured immediately following a 40 ns radiation pulse at wavelengths of 600 nm and 800 nm. Saturation effects in absorption were observed as well as changes in fiber recovery vs time as a function of radiation dose. Step- and graded-index profile fibers were shown to exhibit comparable absorption. Fibers tested included plastic clad silica fibers, as well as graded- and step-index germanium-doped and boron-doped fibers. Plastic clad silica fibers exhibited much less radiation-induced absorption than any other fiber type. The data presented allow optical fiber data links to be designed for use in severe radiation environments where data transmission is required during, or shortly after, the radiation pulse.