Calorimetric measurements of the absorption coefficient of fiber-quality glass: experiments

The optical absorption loss coefficient alpha of a compound glass from which a fiber is to be drawn is measured in a calorimeter. The experimental embodiment with a cylindrical sample is described. Using an electrically heated Pyrex rod, the dependence of the relaxation time tau(1) and the temperature T(1) on the length of the glass rod and on the thermal parameters of the glass and the surrounding gas is verified experimentally. Using laser heating, agreement is found for Pyrex, fused and synthetic silica, and alkali-germanosilicate glass rods. Synthetic silica behaves capriciously in helium only. The results are compared with the total loss of a silicone-clad fiber drawn with the same glass as a core material.