Ultimately low OH content v.a.d. optical fibres

Ultimately low OH content optical fibres with 1.2% refractive-index difference and 80 ¿m core diameter have been successfully obtained by dehydrating a v.a.d.-made porous preform under optimised conditions. The loss increase at 1.39 ¿m due to residual OH ions was only 0.04 dB/km. Accordingly, the measured attenuation curve can be resolved into contribution from the intrinsic loss mechanism with the additional low waveguide imperfection loss.