Aerial Optical Fibre Cables Description The cable is of Central Loose Tube (CLT)structure. Single Mode Optical Fibres are placed in a Loose Tube and filled with jelly. Over the loose tube a thin layer of jelly is applied during the extrusion process. Three FRPs are embedded in the sheathing. To make it suitable for aerial Application Aramide Yarn is raped over the sheathing and then it is jacketed with Nylon. Application Trunk & Junction Network in hilly areasData Link in hilly areas.