nto the holes. Pulling very long length of microstructured fibers is not easy due to the need of maintaining the cross section constant and in general there is a limit to the length of a piece of such fibers. Cleaving and fusion splicing PCFs is in principle possible, but can be more dif- ficult, particularly for fibers with large air content. During fusion splicing, the air may expand and distort the fiber structure. Connections between fibers are also possible with a variety of mechanical splices, fiber connectors, protected patch cables, beam expansion units, etc. Even when the splicing process works well, there may be a substantial coupling loss due to a mismatch of mode areas, for example, when a small-core PCF is cou- pled to a standard single-mode fiber. There are special tapered single-mode fibers and tapered PCFs for enhancing the coupling efficiency, but these may not be eas- ily available. 4.2.12 Fiber Cables Simply covered by the polymer jacket, an optical fiber is impossible to deploy in the field. In order to be used, an optical fiber has to be packaged in a fiber cable [42]. The major benefits of fiber optic cabling are as follows: Easy handling: Some communication systems require tens or even hundreds of fibers (such as a metro backbone system). However, fibers in a cable make it very easy to install and maintain. Protection from damaging forces: Fiber optic cables have to be pulled into place through ducts (outdoor) or conduits (indoor). Pulling eyes are attached to the strength members or cable outer jackets. This is critical for isolating the fibers from the applied pulling forces. Glass fibers cannot endure more than 0.1%-0.2% elongation during installation. Protection from harsh environment factors: Cable structures protect fibers from mois- ture (outdoor cables), extreme temperature (aerial cables) and influx of hydrogen into the fiber (which causes light absorption peak at 1380 nm, which in turn impair fibers' transmission properties). Telecommunication Networks Jacket Jacket Mylar wrap Ara