Abstract

When sufficient power is launched into an optical fiber, the fields can be high enough to cause breakdown and catastrophic destruction of the core. The consequence is an intense white spot of light traveling at speeds of 1-5 m/s along the fiber toward the laser: the fiber fuse. The mechanisms behind the phenomenon are not yet fully understood; however, it seems likely that runaway thermal self-focusing plays a role leading to extremely high local intensities that are ultimately limited by the onset of a variety of different nonlinear processes.^1,2 One might expect that very high-power densities would be required to start the fiber fuse. However, we have been able to initiate it at relatively modest power levels in a number of differently doped single-mode and multimode fibers by heating the fiber locally using the flame of a match. The fibers that most readily exhibited the effect had cores which were Na-doped, cw power densities of only 50 mW/µm² (all lines from an argon-ion laser) being sufficient to initiate the fuse.

© 1988 Optical Society of America