Evaluation of High-Temperature Absorption Coefficients of Ionized Gas Plasmas in Optical Fibers

The large absorption coefficient $alpha$ of a fiber core at high temperatures is closely related to the generation of a fiber fuse. When silica glass is heated to a temperature above 4500 K, it forms Si $^{+}$ and O $^{+}$ ions and electrons in the ionized gas plasma state. We estimate the $alpha$ value for the plasma in the fiber core at high temperatures. $alpha$ begins to increase at 3500 K, then increases rapidly with increasing temperature above 4000 K, reaching a value of $1times 10^{7}$ m$^{-1}$ at 6000 K. This value is about 300 times that necessary for initiating a fiber fuse.