| 摘要 |
PURPOSE:To obtain an optical fiber which has a small spread angle of light and superior transmitting power by providing an optical material with a temperature gradient in its extrusion direction, and thus decreasing the crystal grain size successively from the center part of the core to the external circumferential part of the fiber. CONSTITUTION:When an optical crystalline material 1(TeBr-TeI) is to be spinned into an optical fiber by a heat extruding method, a die 5 is set at 300 deg.C and a nozzle 3 is set at 220 deg.C in spinning to obtain a polycrystalline optical fiber 2. The section of the fiber 2 is shown in Fig. (A) by the extruding method wherein the temperature gradient is provided, and in Fig. (B) when no temperature difference is given. Namely, there are crystals 12 having larger grain size at the core center part and the crystal grain size decreases successively to the external circumference like fine crystals 13. Then, infrared rays are caused to enter the fiber 2. In this case, the spread angle of light emitted from the output terminal is about 6 deg.. As compared with the section in Fig. (B) of uniform grain size, the spread angle of the light is nearly halved, obtaining superior transmittivity. |
