Outside Plant Fiber Optic Cable Types and Hardware
The cable and hardware domain tests selection: which construction suits aerial, duct, direct-buried or drop service, and which closure, messenger, pedestal or grounding part goes with it. Expect questions that pair a route condition with a cable or hardware choice.
Cable constructions
- Stranded loose tube: 6-12 fibers per tube around a central strength member, gel-filled or dry water-blocked; the OSP workhorse for duct and aerial.
- Central tube: compact, lower fiber count, useful where diameter matters.
- Ribbon: 12-fiber ribbons in a flat matrix, high fiber count in a small cable; designed for mass fusion splicing.
- ADSS: all-dielectric, self-supporting, no messenger; span tension and ice/wind loading must be engineered.
- Armored (steel tape) for direct burial; toneable drop has a copper tracer for locating; figure-8 has a messenger built in; flat drop is for aerial service.
Hardware
- Closures: dome, inline and butt types, plus pedestals; splice trays hold splices and manage bend radius. Re-enterable closures matter on routes that will change.
- Aerial: messenger, lashing wire, suspension clamps, dead-ends, spiral vibration dampers.
- Underground: vaults, handholes, innerduct, cable racks, pulling eyes and grips.
- Bonding and grounding hardware, locate wire and cable tags complete the plant.
Worked example
A 288-fiber ribbon cable carries 12-fiber ribbons, so it has 288/12 = 24 ribbons. If each splice tray holds 12 ribbons, the closure needs at least two trays for a straight splice, plus space for slack and a possible future branch. Mass fusion splices all 12 fibers at once, but the tray count and closure size must still be planned; a 24-ribbon closure is not a 12-splice closure.
Traps
- Specifying ADSS where span tension, ice or wind exceeds its rating; ADSS is not a universal aerial cable.
- Lashing cable to a messenger that cannot carry the added load.
- Direct-burying unarmored cable or indoor cable outdoors without UV and water protection.
- Confusing gel-filled and dry-blocked cables when choosing closure and splicing practice.