multi-fiber loose buffer
The loose tube, Multi-Fiber Loose Buffer, is a fiber optic cable in which multiple optical fibers are loosely wrapped together by a plastic tube. The sheath may consist of one or more layers of the same or different plastics, usually polyethylene. Depending on whether the cavity inside the sheath is filled with a gel-like mass or not, a distinction is made between filled and unfilled loose tubes.
The filling serves to repel water, but also forms a protection against excessive bending loads on the plastic tube. The bending radius of loose tubes depends on the number of glass fibers and is about 10 times the outer diameter. When laying such a cable outdoors, care should be taken to ensure that the cable is laid in empty conduits and provides protection against rodents.
Filled and unfilled loose tubes can also be identified by the cable designation: for an unfilled loose tube, the second letter for the cable abbreviation is a "B", for the filled one it is a "D". In addition, the individual optical fibers of the loose tube have a color code. Since most loose tubes consist of 12 optical fibers, they have been assigned 12 colors. The same color code is also used for the microducts.