| 摘要 |
PURPOSE:To obtain the title fiber having a high extinction ratio irrespective of the absence of a stress imparting part by inserting a quadrangular prismatic core into the quadrangular prismatic hollow part formed at the center of a clad vitrifying the materials, regulating the clad outer diameter, and then drawing the materials. CONSTITUTION:The sooty clad 21 of fiber made by the CVD, VAD, duplex crucible methods, etc., is bored at its center to form the part 22 in the form of a quadrangular prism. The core 11 in the form of a quadrangular prism is inserted into the hollow part. The materials are heated in a high-temp. furnace, and vitrified to obtain a preform. The preform is then pressed from the outside, if necessary, to eliminate the gap between the hollow part 22 and the core 11, ground into a circle, and further heated to shape the surface. The preform is drawn while keeping its circular profile, and the fiber having the rectangular core 11 is obtained. The clad is then coated, as required, with a protective primary coat, a buffer layer, a jacket layer, etc. |
