Pure Silica core fibers (Si)
Single-mode and polarization-maintaining fibers have a core doped with germanium as standard. Short-wavelength radiation interacts with the germanium to produce color centers that cause a non-reversible attenuation of the fiber (solarization effect) that increases with time.
For wavelengths <460 nm, Schäfter+Kirchhoff provides single-mode fibers and polarization-maintaining fibers with a pure silica core. These fibers do not demonstrate radiation-induced attenuation and so have a lower attenuation that is stable over time.
Pure silica core fibers are also more resistant to hard radiation than Ge-doped fibers.