PURPOSE: To obtain an optical fiber having the transmission characteristics which is not affected by the variation of temperature, by giving elongation at rupture of a specific value or more and a specific relation between the dynamic modulus and the loss modulus to a thermosetting resin of a reinforcing coating layer having a specific content of reinforcing fibers and a specific thickness.
CONSTITUTION: In the reinforced optical fiber where an optical fiber 3 is covered with a reinforcing coating layer 2 having 100W2,500μ thickness which contains 60W85wt% reinforcing fibers 3 such as glass fibers and carbon fibers to a thermosetting resin 4 such as an unsaturated polyester or an epoxy resin impregnated in these fibers, ≥2% elongation at rupture is given to the resin 4, and a phase angle δ(tanδ=E"/E') obtained on a basis of a dynamic modulus E' and a loss modules E" in the dynamic viscosity test satisfies the condition of equation. As reinforcing fibers 3, long fibers are used, and short fibers may be mixed in a resin liquid and be entwined round long fibers. Reinforcing fibers 3 and the resin 4 are made adhesive to each other. Thus, the reinforced optical fiber superior in bending strength, flexibility, impact resistance, etc. is obtained.
TAKAHASHI TAKUZOU
SHIRASAKA ARIO
