| 摘要 |
PURPOSE:To prepare optical fiber having superior heat resistance and suitability for use in high temp. atmosphere by forming both the core and clad of a heat resistant high melting metal oxide (high m.p. oxide) and adjusting the refractive index of the clad to below the refractive index of the core. CONSTITUTION:The core and the clad are both formed of high m.p. oxides and the refractive index of the clad is adjusted to below the refractive index of the core. The core and the clad are both formed of single crystals of high m.p. oxide, and the clad is formed by the reactive sputtering method, and the single crystal is formed by the laser-annealing method. Preferred high m.p. oxide is either one among CaO, ZrO2, SrO, ThO2, BeO, MgO, Y2O3, and Al2O3; and Al2O3 is preferred for clad because of its smallest refractive index. The optical fiber formed by such constitution has high heat resistance and is useable in high temp. atmosphere upto 1,500 deg.C. An oxide having superior optical characteristics and reactivity with water or CO2, etc. in the air such as CaO, etc. has become usable for optical fiber by forming clad of Al2O3 by the reactive sputtering.
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