Investigation of the Diffusion of Water in Optical Fibers at Elevated Temperature and Pressure

摘要

Optical fibers are being used in an increasingly wider range of applications, some of which involve elevated temperature and pressure in the presence of water. Measurements of the penetration rate of water into optical fibers at elevated temperature (300 °C) and pressure (1440 psi) is presented for standard communication grade silica fiber and for "protected" fibers. The penetration rate was monitored in-situ using a broadband light source and an optical spectrum analyzer to measure the change in absorption over the spectral range from 400 to 1700 nm. Methods to protect the optical fibers from water penetration were also evaluated in the elevated temperature and pressure environment. Stress corrosion cracking data for fibers exposed to air at room temperature and pressure as well as "dry" and "wet" fiber treatments is also presented in terms of time to failure versus bend radius for selected environmental conditions. Effect of chemical treatments on the time to failure at fixed bend radius both for pre-water and post-water exposure is presented.