| 摘要 |
PURPOSE:To improve mechanical strength without decreasing detection sensitivity by forming a plastic clad of two plastic layers in such a way that the inside plastic layer has the refractive index equal to the refractive index of a glass fiber and the outside plastic layer is made smaller in refractive index than the inside plastic layer. CONSTITUTION:An optical fiber 10 for detecting liquid leakage is formed of a glass fiber 12 formed of quartz or multi-component type glass and a plastic clad 14, such as silicon, applied on the glass fiber. The clad 14 consists of two plastic layers 14A and 14B, which inside layer 14A has the refractive index n2 equal to the refractive index n1 of the fiber 12 and which outside layer 14B has the refractive index n3 smaller than the refractive indices n1, n2. Then if the outside diameters of the fiber 12 and the layers 14A, 14B are designated respectively as d1, d2, d3, the mechanical strength is improved by the clad 14 having the thickness of (d3-d1)/2 and the detection sensitivity for liquid leakage is thoroughly improved by the layer 14B having the thickness of (d3-d2)/2. |
