Measurements of OH Diffusion in Optical-Fiber Cores

A color-center laser was used at 0.95 μm to determine the activation energy for OH diffusion in the cores of current multimode fibers. The temperature range of 600 to 800°C was investigated and the activation energy determined to be 19,700 ± 1600 cal/mole in agreement with previous values reported for bulk silica. Based on this value, some 23,000 years would be necessary at 90°C to produce a 3-percent change in the 0.95-μm OH absorption at the core center. Apparently, OH diffusion over a service life of optical fibers should not be a problem in presently envisioned lightwave applications.