| 摘要 |
PURPOSE:To manufacture a preform for an optical fiber retaining the plane of polarization with high reproducibility, by making the relative positional relation among four burners arranged around a base material for a preform constant and by providing a uniform temp. difference between flames from the adjacent burners. CONSTITUTION:Four burners 2, 3, 4, 5 are symmetrically arranged around a base material 1 for a preform formed by depositing glass films for a clad and a core on the inner wall of a glass pipe. The burners 2-5 are controlled so that flames from the opposite burners 2, 4 and 3, 5 are kept at the same temp. and that flames from the adjacent burners 2, 3, etc. have a uniform temp. difference. The material 1 is heated with the flames from the burners 2-5 while rotating the burners 2-5 without changing the relative positional relation among the material 1 and the burners 2-5 to obtain a preform for an optical fiber having an elliptical clad or core and retaining the plane of polarization. |
