Study on Copper-Coated Optical Fibers

• Main Authors: Lin, Yi-Shyang, 林益祥
• Other Authors: Sham-Tsong Shiue
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/90957051067957285983

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.