Phosphor-doped silica cladding v.a.d. fibres

Loss reduction of v.a.d. (vapour-phase axial deposition) fibres at wavelengths of 1.3 ¿m and 1.6 ¿m was investigated. The infrared absorption loss was reduced by applying SiO2-P2O5 cladding instead of SiO2-B2O3 cladding and by minimising the waveguide imperfection loss. The minimum losses of the fabricated v.a.d. fibre were 0.5 dB/km and 0.28 dB/km at wavelengths of 1.3 ¿m and 1.6 ¿m, respectively. This fact indicates that fibres fabricated by the soot process, like those made by the vapour-phase axial-deposition process, can be used as long-wavelength optical transmission media. We have also found the OH absorption abnormality at wavelengths of 0.95, 1.24 and 1.39 ¿m, and the loss peak values are different from those reported.