Jr. Clowes et al., EFFECTS OF HIGH-TEMPERATURE AND PRESSURE ON SILICA OPTICAL-FIBER SENSORS, IEEE photonics technology letters, 10(3), 1998, pp. 403-405
We report on the effects of liquids at high temperature and pressure o
n silica optical fibers, sensors, and gratings, We propose that the di
ffusion of molecules into the silica and the resultant expansion of th
e network are responsible for observed fiber expansions of up to 0.2%
and Bragg wavelength increases of 2 nm at 1525 mn, An amorphous carbon
hermetic coating has shown a reduction of these effects by an order o
f magnitude at 300 degrees C, These results have strong implications f
or the deployment of fiber sensors in hostile environments such as oil
wells.