Preform
143170
225791824
2008-07-15T12:36:06Z
Rlboyce
5465760
I'm assuming that there is no such a thing as "fross-section"
{{split}}
A '''preform''' is material that has undergone preliminary shaping but is not yet in its final form.
== Fiber optics ==
[[Image:DShaped1.png|right|120px|right|thumb|Cross-section of a fiber drawn from a D-shaped '''preform''']]
In [[fiber optics]], a preform is a piece of glass used to draw an [[optical fiber]].
The preform may consist of several pieces of a glass with different [[refractive index]],
to provide the core and [[cladding]] of the fiber. The shape of the preform may be circular, although for some applications such as [[double-clad fiber]]s another form is preferred.<ref name="Kouznetsov">{{cite journal|title=Highly efficient, high-gain, short-length, and power-scalable incoherent diode slab-pumped fiber amplifier/laser| author= Kouznetsov, D.| coauthors=Moloney, J.V.| journal=[[IEEE Journal of Quantum Electronics]]| url=http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=1242365&isnumber=27838|volume=39 | year=2003 | issue=11 | pages=1452–1461 | doi=10.1109/JQE.2003.818311}}</ref> In [[fiber laser]]s based on double-clad fiber, an asymmetric shape improves the [[filling factor]] for [[laser pumping]].
Due to the surface tension, the shape is smoothed during the drawing process, and the shape of the
resulting fiber does not reproduce the sharp edges of the preform.
Nevertheless, the careful polishing of the '''preform''' is important, any defects of the '''preform'''
surface affect the optical and mechanical properties of the resulting fiber. In particular, the preform
for the test-fiber shown in the figure was not polished well, and the cracks are seen with confocal optical microscope.
==Archeology ==
In [[archeology]], a preform is the rough, incomplete and unused basic form of a [[stone tool]] formed by [[lithic reduction]]. Typically, a preform is the shaped remnant of a [[lithic core]]. Larger and thicker than the intended tool, it lacks the final trimming and refinement that is present in the completed [[Artifact (archaeology)|artifact]]. Sometimes basic features such as stems and notches have been initiated. In most cases, the term refers to incomplete [[projectile point]].
==Soldering ==
A solder preform is a speciallly designed shape of solder adjusted to the application where it is used. Although there are many methods that are used to manufacture the solder preform, stamping is probably the most common method. The solder preform can be manufactured including the solder flux needed for the soldering process. This can be an internal flux, inside the solder preform, or external, where the solder preform is coated.
== See also ==
{{wiktionary|preform}}
*[[Blank (archeology)]]
==References==
<references/>
[[Category:Lithics]]
[[Category:Fiber optics]]