| Summary: | 碩士 === 逢甲大學 === 材料科學研究所 === 85 === Metal-coated optical fibers exhibit higher resistance to
moisture attack and show higher mechanical strength than
polymer-jacketed optical fibers, and can withstand the damage in
a higher temperature environment. In this paper, copper-coated
optical fibers are studied. First, in a zero axial force
condition, the thermal stresses in copper-coated optical fibers
have been analyzed by the thermoelastic approach. In these
thermal stresses, the maximum interfacial radial stress at the
interface of glass fiber and copper coating induces microbending
losses; the maximum thermal stress induces the breaking of
copper coating along the axial direction; the maximum
interfacial shear stress induces the spalling of copper coating
at both ends of fibers; and the maximum axial force induces the
buckling of optical fibers and results in an additional
microbending losses. The thermal stresses can be minimized by
properly selecting the material properties of copper coating and
its thickness. Secondly, copper-coated optical fibers are
fabricated by the magnetron direct-current sputtering method,
and the mechanical strength of fibers treated in various
environments is evaluated. The untreated copper-coated optical
fibers exhibit the highest tensile strengh and their average
strength is 55.70 MPa. By the same treating time, the strength
of copper-coated optical fibers exposed in an atmosphere is
higher than that immersed in a water bath; and the average
strength of copper-coated optical fibers decreases with
increasing the treating time. Additionally, the fractography of
copper-coated optical fibers is observed by the scanning
electron microscope and the crack length of copper-coated
optical fibers is measured to estimate the critical stress
intensity factor. The critical stress intensity factor of
copper-coated optical fibers treated in various environments do
not obey a general rule. Finally, in a plane strain condition,
the thermal stresses in triply metal-coated optical fibers have
been analyzed by the thermoelastic approach. The thermal
stresses in triply metal-coated optical fibers can reduce to
those of singly or doubly metal-coated optical fibers. The
derivation in a plane strain condition is simpler than that in a
zero axial force condition, and the difference of interfacial
radial stress between these two methods is small. In the special
case of singly aluminum-coated optical fibers, the thermal
stresses in aluminum-coated optical fibers are proportional to
the temperature change, and are a function of the material
properties of aluminum coating and its thickness. Microbending
losses and breaking of aluminum-coated optical fibers can be
minimized by optimally selecting the material properties of
aluminum coating and its thickness.
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