| 摘要 |
PURPOSE:To allow the title optical core fiber to have sufficiently a lateral pressure resisting characteristic and a heat resisting property by providing a high heat resistance resin film layer of a multilayer structure formed by providing a polyimide compound resin single layer whose covering thickness is within a prescribed range value and a fluororesin layer on the outer layer of the polyimide compound resin, on the outside periphery of an optical fiber. CONSTITUTION:As for a cross-sectional structure of an optical fiber core 3, a covering layer 2 of a double layer structure formed by providing a primary covering layer 21 of a polyimide compound resin layer and a secondary covering layer 22 of a fluororesin layer on the outer layer of the layer 21 is provided on an optical fiber 1. Subsequently, with regard to a heat resisting optical core fiber, when a heat resisting optical whose covering outside diameter is different is manufactured by executing wire drawing from the same optical fiber base material, the increase quantity of a transmission loss decreases together with a drop of generated stress. Also, by thickening it to some extent, the transmission loss increase quantity tends to be saturated to a prescribed value, as well, and for instance, when the covering thickness exceeds 300mum, a temperature characteristic of the optical fiber tends to become unstable due to the influence of thermal contraction of the covering material, therefore, as for optimum covering thickness, 25mum-300mum is desirable. |
