| 摘要 |
PURPOSE:To obtain a polarizing surface maintaining optical fiber which can be manufactured stably and whose characteristic is excellent by setting the second clad of an optical fiber for maintaining a polarizing surface of a four-layer structure to a prescribed component rate and a prescribed refractive index. CONSTITUTION:A core 1 contains SiO2 and a dopant for raising a refractive index, for instance, GeO2. A shape breakdown of the core 1 is prevented by cutting the influence of B2O3 contained in the second clad 3 by the first clad 2 of SiO2 of high purity. The rate of P2O5 of the clad 3 is 3-10mol% and the rate of B2O3 is 2.5-8mol%. The third clad 4 is a guartz glass which contains no dopant. The refractive index distribution is adjusted so that the core 1 is the highest, the clads 2, 4 are almost equal, and the clad 3 is lower than the core 1 and higher than the clad 2. P2O5 of the clad 3 is a little more than B2O3, and the total quantity of both of them is 5.5-18mol%, and in case of <=5.5, the viscosity is high and conversion to a prescribed elliptical shape is difficult, and in case of >=18, the viscosity becomes low. |
