Core-less End Caps | previous | next | feedback |
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Definition: end pieces attached to fibers, containing no fiber core
For some applications, it can be helpful to use optical fibers with core-less end caps, i.e., to attach small pieces of glass without a waveguide structure (fiber core) to the fiber ends. The possible advantages are:
- As a laser beam coming out of the fiber diverges before reaching the air, the optical intensities at the glass/air interface are reduced. In this way, optical damage of fiber end faces, e.g. in Q-switched fiber lasers or in pulsed fiber amplifiers, can be avoided.
- Any Fresnel reflections at the glass/air interface cannot efficiently couple back into the fiber core, since the reflected beam diverges further on the way back to the core. This effect, possibly combined with an angled end face, can help e.g. to suppress parasitic lasing in high-gain fiber amplifiers.
- For photonic crystal fibers, an end cap (hermetically sealed end facet) can prevent fluids (e.g. water) from getting into the air holes, from which they could hardly be removed due to strong capillary forces. One possibility is to splice an end cap to such a fiber. Alternatively, it is possible to heat the fiber end e.g. with a fusion splicer, so that the microscopic holes collapse.
See also: fibers, fiber lasers, fiber amplifiers, photonic crystal fibers
Categories: fibers and other waveguides, lasers
