| 摘要 |
PURPOSE:To prevent a transmission loss and a broken line by tension of a core wire, by forming a soft long material which has contained plural optical fiber strands or core wires, so that its section is not circular, and making the inside surface of a metallic pipe press-contact with a projecting part of its surface. CONSTITUTION:An optical fiber unit 1 is constituted by longitudinally adding plural optical fiber core wires (those which have a secondary coating 4B such as nylon, etc. on the outside circumference of a strand 4A) to the outside circumfernce of a tension member 3 having a soft elastic coating 2 such as silicon rubber, etc. on the surface, extruding a soft elastic long material 5 such as silicon rubber, etc. so that its section is not circular, to its outside circumference, coating it, and coating its outside circumference with a metallic pipe. As for coating of the metallic pipe 6, a metallic tape is longitudinally added and coated to the long material 5, joint parts of the metallic tape are welded, by which the metallic pipe 6 is formed, and it is reduced, and a projecting part 5A of the long material 5 is made to press-contact with its inside surface. The long material 5 has allowance to escape in the circumferential direction, therefore, lateral pressure is not put on, and the transmission loss and the broken line by tension of the core wire are prevented. |
