| 摘要 |
PURPOSE:To float a loose portion on a water surface so as to prevent it from interrupting water flow or prevent an optical conduit line layed in a water line or optical cable from being subjected to great tension by making the specific gravity of the whole optical cable conduit line or the optical cable. CONSTITUTION:A hollow pipe 22 for an optical cable is coated with a foaming plastic 23, and a protection sheath 24 is applied thereon as a coat, wherein the foaming ratio and the thickness of the plastic 23 are adjusted to make the specific gravity of the whole 1 or less. An optical cable conduit line 21 is formed in this way and after the line 21 is layed in a water line, an optical cable is pulled in the pipe 22. With the specific gravity of 1 or less, a loose portion floats on water surface even if the line 21 or the cable is layed while suspended from the ceiling face of the water line, so that foreign matters and the like do not enter a space between the conduit line 21 or the cable and the ceiling face of the water line, and in laying operation it can be layed according to water flow without a pulling net and the like. |
