Tellurite And Fluorotellurite Glasses For Active And Passive

2. Literature review; MDO 47
5.75×10 15 .exp(-126.67/λ) dB.km -1 [36]. Fig. (2.8) shows the theoretical minimum loss
spectrum of TeO2-Na2O-ZnO glass. Line 1 is the UV edge, 2 the IR edge with OH, 3 IR
edge without OH, and 4 Rayleigh scattering.
Fig. (2.8): Theoretical minimum loss spectrum of TeO2-Na2O-ZnO glass. Line 1 - UV
edge, 2 - IR edge with OH, 3 - IR edge without OH, and 4 - Rayleigh scattering [36].
The calculated minimum intrinsic loss for tellurite glass fibre was 3.6×10 -3 dB.km -1 at
3.02 µm [36]. Due to extrinsic OH absorption bands (at 2.86 and 3.33 µm), this is
pragmatically shifted to 1.8×10 -2 dB.km -1 at 1.9 µm [36]. Actual losses of fibre reported
by Wang are around 900 dB.km -1 at ≈ 1.35 µm [36]. This is likely to be due to other
extrinsic factors such as scattering centres in the glass (undissolved batch material,
crystals etc.), defects in the core/clad structure, and absorbing species (OH, crucible
contamination).