... 9001, 2000 2.CE certificate C.O.D Corrugated Optic Duct pipes summarized formerly each kind of fiber optics, advantages in ... multiple inner ducts (3 to 9) inside of the outer duct by means of assembling cable ducts in the course of ... reducing considerable consecutive work quantities such as trench excavation, inner duct insertion (no need as it is readily built-in), inner ...