Tellurite And Fluorotellurite Glasses For Active And Passive

8. Fibre drawing; MDO 338
(a) (b)
Fig. (8.3): Fluorotellurite glass preforms (a) before, and (b) after fibre drawing, with nonadhesive
white tape to protect glass surface from damage from grip of metal clamp.
8.1.4. Optical loss measurements – cut-back method
Fibre optical loss measurements were performed using, the FTIR set-up described in
section 6.1.1, and the cut-back method. The loss over a length of fibre (typically 1 m) was
measured. The fibre was then cut-back a number of times (e.g. in 20 cm segments) and
the loss measured each time. A number of spectra were then obtained, and an average
taken. A defect at one point in the fibre would result in high loss over a 1 m length.
Therefore, if this section of the fibre was cut-back, the loss of the remaining defect free
glass was measured. This method also can allow the characterisation of defects, in
combination with microscopy. Light was brought out of the spectrometer from a tungsten
lamp and focused into the fibre using a parabolic aluminium mirror. The InSb detector
was cooled with liquid nitrogen.