Connecting the Future With FTTH Cables
Access network Out Side Plant (OSP) cabling can be categorized into three segments, namely feeder cable, distribution cable, drop cable. Figure 1 gives a simple pictorial view of the FTTH network infrastructure elements.
In FTTH network, a feeder cable seen in Figure 2 is usually connected as ring topology extending from the central office to the Local Convergence Point (LCP) to provide connections to one or more distribution cables. A single feeder cable usually serves several distribution cables that will minimize the amount of optical cable, which provides a low initial cost of installing FTTH network. This cable, also called trunk cable, offers the highest packing density, since all the fibers are laid out in rows, typically of 12 fibers, and laid on top of each other. It generally uses a ring structure, which is convenient for expansion of the coverage area on basis of the ensured network security.
In FTTH system, distribution cables (Figure 3) start from LCP and run to the entrance of the neighborhood. They are intermediate link connecting the feeder cable subsystem and the drop cable subsystem. It had better adopt the tree structure with the optical fiber quantities to save the engineering investment. As displayed in figure 2, distribution cable is the most popular FTTH indoor cable for its smaller size and light weight. It contains several tight-buffered fibers bundled under the same jacket with Kevlar strength members and sometimes fiberglass rod reinforcement to stiffen the cable and prevent kinking. These cables are used for short, dry conduit runs, riser and plenum applications.
FTTH drop cable (Figure 4) connects Network Access Point (NAP) to the subscriber premises. Drop cables are designed with attributes such as flexibility, less weight, smaller diameter, ease of fiber access and termination. Their structure as well as their performance is optimized to be able to work with various FTTH applications. Drop cables will contain only 1 or 2 fibers for the connecting circuitry and possibly additional fibers for backup or for other network architecture reasons. This kind of wire is available in less fiber count and provides the only link to the subscriber, with no network diversity. Drop cables can be divided into 3 types: direct buried cable, blown fiber cable and aerial cable.