Working on optical fibers exposed with high power laser beam.

Illustration showing (1) the ignition, (2) the propagation, and (3) the termination of a fiber fuse. A fiber fuse is initiated by the local heating of a single-mode optical fiber made of silica glass delivering a few watts of light, which generates an optical discharge running along the fiber to the light source at about 1 m/s (see my portrait). This is due to the temperature dependence of the light absorbance of silica glass, which increases rapidly beyond 1300 K and causes light-heat conversion that generates an optical discharge of several thousands of K. This results in the catastrophic destruction of the core region and the formation of periodic voids (see background photo, its interval is about 20 um.) and the damaged fiber no longer transports light.