Infrared optical loss increase in silica fibers due to hydrogen

Hydrogen-related optical loss increases in silica fibers in the infrared wavelength region are discussed. The loss increase phenomena mainly consist of two features: one originated from H2absorption loss and the other from OH absorption loss. The origin of these loss increases has been clarified in view of H2gas diffusion in fiber and OH bond formation by a chemical reaction via defects in glass network. Countermeasures to suppress the loss increase to a sufficiently low level have been established by preventing the use of P2O5dopant and by selecting the fiber coating material and the coating condition.