Fiber Fuse | previous | next | feedback |
Definition: the effect that an optical fiber "burns" from the output end under the influence of an intense laser beam launched into the other end
The small mode areas for light propagating through fibers lead to rather high optical intensities even for moderate power levels. It is therefore no surprise that particularly a fiber input end, into which a laser beam is launched, can easily be destroyed, particularly when the fiber end is not very clean. The really surprising effect, however, is that a fiber can also burn down starting from the output end. Here, a bright white spot can be seen, which results from a rather hot plasma forming at the fiber end. As this plasma fuses the fiber, it propagates back towards the input end with a velocity which can be several meters per second. In standard single-mode fibers, this phenomenon can occur already for powers below 1 W if something (e.g. a burning dust particle) triggers the plasma at the output end. An important ingredient for the underlying mechanism is that the absorption losses of silica sharply rise at temperatures above 1000°C.
The effect of fiber fuse can be disastrous in a telecom system where kilometers of fiber may be destroyed as a result of a failure at only one point. This is a concern for fiber-optic links with extremely high transmission capacities. A partial remedy may be to reduce the cladding diameter at certain points so that the fiber fuse is stopped at such locations [2].
Note that high-power fiber amplifiers are at particularly high risk of suffering fiber fuse; appropriate measures have to be taken to ensure device reliability.
Bibliography
| [1] | R. Kashyap and K. J. Blow, "Observation of catastrophic self-propelled self-focusing in optical fibres" (first report of fiber fuse effect), Electron Lett. 24, 47 (1988) |
| [2] | E. M. Dianov, I. A. Bufetov, and A. A. Frolov, "Destruction of silica fiber cladding by the fuse effect" (showed that a fiber fuse can be stopped at a point where the cladding diameter is reduced), Opt. Lett. 29 (16), 1852 (2004) |
See also: fibers, fiber lasers, fiber amplifiers
Category: fibers and other waveguides
