| 摘要 |
PURPOSE:To enhance strength of an optical fiber by exercising compressive force on the surface of the optical fiber and preventing growth of scratches and cracks on the surface. CONSTITUTION:An optical fiber is composed of a core 1 for transmitting light and a clad 2, and a part of it is doped with B, P, F or the like to form a stress giving layer 3. Since this layer 3 has a thermal expansion coefficient higher than that of quartz glass, its volume contracts more due to temp. difference when the fiber is drawn. As a result, compressive stress is exercised on the surface layer 4 made of quartz glass. This compressive stress lessens occurrence of scratches and cracks themselves, and at the same time, also restrains growth of them, and prevents large scratches and cracks causing so-called small strength, and an optical fiber having extremely high strength can be obtained. |
