This post is a continuation of another discussion: Comparison of Jelly Filled Copper Cable and Optical Fiber Cable Constructions-Part 1
Optical fiber cables have clear advantages over copper cables, an obvious reason why telecom operators prefer and switch to optical fiber cables to build their telecommunication networks. Let us see the comparison of construction of jelly filled telephone cable and optical fiber cable. This comparison is made based on my experience in both type of cables, but hope will provide a general idea of both types of cables.
Wrap: The jelly filled copper cable is covered with a layer of non-hygroscopic polyester tape to contain the jelly. This also acts as a mechanical protection to the cable core, and as a dielectric. In optical fiber cabling process also, a non-hygroscopic polyester tape is wrapped around the stranded core to contain the jelly. This wrapping gives thermal protection to the cable. Alternatively, water swellable tape is also used in semi-dry and fully dry cable designs.
Aluminium Poly-Laminate Screen: An aluminium tape coated on both sides with polyethylene is applied longitudinally over the core wrap. This helps in preventing electrical interference induced by other Power Cables laid in parallel. It also acts as a moisture barrier. For optical fiber cables, aluminium tape is not required or not mandatory. There are many cable specifications that are created with the influence of copper telephone cables, demanding application of aluminum tape. Application of aluminum tape can be replaced with alternative materials for moisture protection in optical fiber cables.
Inner Sheath: A tight-fitting sheath of black polyethylene is extruded over the Aluminium Poly-laminated Screen, which offers protection to the cable. Inner sheath is provided for optical fiber cables that are intended for direct buried application. Polyethylene, PVC, LSZH etc can be used for inner sheathing.
Bedding and Armoring: In jelly filled telephone cables, a double polyethylene tape is applied helically over the inner sheath with overlap. This acts as bedding for the steel tape. The cable is then helically armored with double galvanized steel tapes with overlap. This offers mechanical protection to the cable. Corrugated steel tape armoring is popularly used for optical fiber cabling process. Armoring can be directly applied over the stranded core or over the inner sheath.
Outer Jacket: In Jelly filled copper telephone cables, a circular tight fitting sheath of polyethylene is extruded over the armored cable. This acts as a mechanical protection and protection against ultra-violet rays. In Optical fiber cabling process also, an outer sheath of polyethylene or PVC or LSZH etc are applied over the inner sheath or armoring.
Marking: Marking is done on the outer surface of jelly filled telephone cables using ink jet printing, hot foil indentation or embossing techniques. Optical fiber cables are also making use of these methods for marking.
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