
Thus, strong absorptions by Fe
2þ
and Cu
2þ
at near-infrared wavelengths were
diminished. Fibers adequate for commercial systems of the time were made this
way. Losses as low as 5 dB/km were achieved at 0:9 mm, but the lower losses
offered by the 1.3- to 1:5-mm spectral window were unattainable using this
technique. Fundamental electronic vibrations and severe OH
contamination
were intrinsic to the starting materials and could not be appreciably lowered by
improved processing. The method was stillborn as it was introduced to the
market due to the advent of a superior technology.
3.2 VAPOR-DEPOSITION TECHNIQUES
The double-crucible technique was short-lived ...