It is well known that silica-based optical fibers contain a variety of defects,1 including nonbridging oxygen hole centers (NBOHCs) and oxygen vacancy centers, which absorb in the vicinity of 640 and 210 nm, respectively. While these defects have little effect on the IR transmission window, it has been shown recently2·3 that, in the presence of hydrogen, these defects can react to form sites that absorb in this window, a permanent loss at 1380 nm (SiOH) and a transient loss at 1520 nm (SiH). However, since the hydrogen concentrations in typical optical fiber cables are low, these phenomena may not be noticeable during initial qualification but may give rise to unacceptably high- loss increases over the projected lifetime of the cables if the defect concentration is high enough. We describe the growth and decay rates of the absorption features indicated above as well as report on the observed conversion of the transient 1520-nm loss to a permanent absorption at 1460 nm. Using the activation energies and oscillator strengths for these various reactions we are able to provide estimates of the long-term losses to be expected.
© 1988 Optical Society of AmericaPDF Article