Tellurite And Fluorotellurite Glasses For Active And Passive

9. Conclusions; MDO 390
• Increasing melting time and fluorination resulted in a significant decrease in OH
bands in the 700 nm to 2.5 µm region for unstructured 70TeO2-10Na2O-20ZnF2
mol. % fibre, from around 40 to 4 dB.m -1 at 2.5 µm as melting time was increased
from 3 to 10 hours [7].
• Loss for the 10 hour melt was relatively flat (≤ 5 dB.m -1 ) over the entire 700 nm
to 2.5 µm region [7].
• This remaining loss is likely to be a combination of reflection, residual OH,
crucible (Au / Pt) impurities, scattering centres, and scattering from the unclad
fibre surface.
9.6. Overall conclusions and recommendations
The aims of this study were to investigate suitable compositions and fabricate low loss
optical fibre from TeO2-based glasses. Processing routes were carefully controlled, which
ultimately manifested as lower optical loss in drawn fibres. Attenuation in the initial fibre
drawn from fluorotellurite glasses in this study was too high to measure; this was reduced
considerably due to a number of factors, primarily: OH reduction in the batch materials
by fluorination, increasing melting times (self-drying) and drying of the processing
atmosphere (melting and drawing). Control of these factors minimised the number of
scattering and absorbing species in the glasses, resulting in fibre which transmitted in the
700 nm to 2.5 µm region with losses of around 5 dB.m -1 .
Fluorotellurite (TeO2-Na2O-ZnF2) glasses provide an attractive alternative to other
candidate infrared fibreoptic materials such as fluorides and chalcogenides due to ease of