Loss reduction in fluorine-doped SM- and high N.A.-PCVD fibers

SM and GI fibers have been prepared by the low-pressure PCVD process using fluorine as the main dopant and small amounts of GeO
2
as codopant. Compared to pure fluorine doping, these fibers showed markedly improved optical properties. High N.A. (
\delta \approx 2
percent) GI fibers with Rayleigh scattering losses as low as 1.0 dB μm
⁴
/ km as well as "deeply depressed cladding" SM fibers with scattering coefficients of 0.85 dB μm
⁴
/km have been prepared. Simultaneously, a reduced sensitivity of the optical losses on the drawing conditions and improved mechanical properties have been observed.