| 摘要 |
PURPOSE:To produce an optical branching filter having accurate dimension and shape at low cost in a short period by inserting a bundle of optical fiber into a glass pipe having an inside wall layer having a lowered refractive index and lowered melting point and drawing the optical fiber and the glass pipe by melting integrally. CONSTITUTION:Optical fiber 6 to be branched and a bundle of six branched optical fibers 7 is inserted into a glass pipe 20, and a middle part of the glass pipe is drawn by heating. Light receiving and light emitting elements 31-33 for LD light are provided to one of the optional optical fibers 7 and to both ends of the optical fiber 6. The drawing is ceased at a moment when each monitor power given by the elements 32, 33 coincides. Since an inside wall layer 21 of the pipe 20 is treated with boron doping, the refractive index and the melting point of the inside wall layer are low. The outside wall layer 22 is not melted and flowed out on heating the pipe even if the inside wall 21 is melted earlier, so accurate dimension and shape are retained, and mass production of optical branching filter is possible at low cost. |
