Optical fiber cables for indoor cabling are used for the construction of horizontal subsystem and SCS building backbone cabling subsytems. They differ form cables used for outdoor cabling by two key parameters.
Indoor fiber optic cable is tight buffer design, usually they consist of the following components inside the cable, the FRP which is non-metallic strengthen member, the tight buffer optical fiber, the Kevlar which is used to further strength the cable structure, making it resist high tension, and the cable outer jacket. The trend is to use LSZH or other RoHS compliant PVC materials to make the cable jacket; this will help protect the environment and the health of the end users.
Cables for indoor applications include the following:
* Simplex cables
* Duplex cables
* Multifiber cables
* Heavy-, light-, and plenum-duty cables
* Breakout cables
* Ribbon cables
Although thes categories overlap, they represent the common ways of referring to fibers. Figure 7-5 shows cross sections of several typcial cables types.
A simplex fiber cable consists of a single strand of glass of plastic fiber. Simplex fiber is most often used where only a single transmit and/or receive line is required between devices or when a multiplex data signal is used (bi-directional communication over a single fiber).
A duplex fiber cable consists of two strands of glass or plastic fiber. Typically found in a “zipcord” construction format, this cable is most often used for duplex communication between devices where a separate transmit and receive are required.
Duplex cable is used instead of two simplex cables for aesthetics and convenience. It is easier to handle a single duplex cable, there is less chance of the two channels becoming confused, and the appearance is more pleasing. Remember, the power cord for your lamp is a duplex cable that could eaily be two separate wires. Does a single duplex cord in the lamp not make better sense? The same reasoning prevails with fiber optic cables.
Loose Tube Cables
The loose tube variety contains one or more hard buffer tubes, which house between 1 and 12 coated fibers. The hard buffer tubes are also filled with a gel to provide vibration and moisture protection for the fibers. The fibers lie loosely in the tubes, which are wound into the cable in a reversing helical fashion and are actually longer than the outer sheath of the cable. This arrangement allows for a small amount of stretch in the outer sheath when installing the cable. Loose tube cable is used most often in OSP construction because it is designed for a tough outdorr environment use. See Figure-1 for the physical make-up of a typical loose tube cable.
Breakout cables have several individual simplex cables inside an outer jacket. The breakout cables shown in Figure 2 use two dielectric fillers to keep the cables positioned, while a Mylar wrap surrounds the cables/fillers. The outer jacket includes a ripcord to make its removal fast and easy. The point of the breakout cable is to allow the cable subunits inside to be exposed easily to whatever length is needed. Breakout cables are typically available with two or four fibers, although larger cables also find use.
Ribbon cable uses a number of fibers side by side in a single jacket. Originally, Ribbon fiber cable was used for outdoor cables (see Figure 3). Today they also find use in premises cabling and computer applications. The cables, typically with up to 12 fibers, offer a very small cross section. They are used to connect equipment within cabinets, in network applications, and for computer data centers. In addtion, they are comatible with multifiber array connectors. Ribbon cables are available in both multimode and single-mode versions.
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