Practical Industrial Data Networks:Design, Installation and ...

Fiber optics overview 816.5.2 Underground cableUnderground cable experiences less environmental extremes than aerial cables. Cablesare usually pulled into ducts or buried directly in the ground, with the cables being placedin deep narrow trenches, which are backfilled with dirt or else ploughed directly into theground.Cable typeLoose buffering, using loose tube or slotted core construction, is generally used to isolatefibers from external forces including temperature variations.AdvantagesDisadvantages6.5.3 Sub-aqueous cables• Usually, the most cost effective method of installing cables outdoors• Greater environmental protection than aerial cable• Usually, more secure than aerial cable• Can be disrupted by earthquakes, digging, farming, flooding etc.• Rodents biting cables can be a problem in some areas. This is overcomewith the use of steel tape armor or steel braid, or the use of a plastic duct ofmore than 38mm OD for all dielectric cable installations. Also, the use ofTeflon coatings on the sheath make the cable too slippery for the rodent togrip with its teeth.Sub-aqueous cables are basically outdoor cables designed for continuous immersion inwater. While international telecommunications carriers use the most sophisticated cablesfor deep ocean communications, there are practical applications for sub-aqueous cablesfor smaller users. These include cabling along or across rivers, lakes, water races orchannels, where alternatives are not cost effective. Sub-aqueous cable is a preferredoption for direct buried cabling in areas subjected to flooding or with a high water table,where for example, if the cable were buried at say 1 meter depth, it would be permanentlyimmersed in water. These cables are essentially outdoor cable constructions incorporatinga hermetically sealed unit, using a welded metallic layer and encasing the fiber core.AdvantagesDisadvantages6.5.4 Indoor cables• Cheaper installation in some circumstances• Unit cost of cable is higher.Indoor cables are used inside buildings and have properties dictated by the fire codes.Such cables need to minimize the spread of fires and must comply with your relevantlocal fire codes, such as outlined in the National Electrical Codes (NEC) in USA.Outdoor cables generally contain oil-based moisture blocking compounds like petroleum