OFC Laying, Ducting, Aerial and Underground Installation
OFC laying, ducting, aerial and underground installation are tested through route engineering, pulling limits, bend radius, duct occupancy and slack calculations.
Core rules
- Underground: trench to the depth specified in the route drawing and local authority requirement, lay HDPE duct (commonly 40/33 mm), maintain duct continuity, install draw pits and joint chambers, place warning tape and route markers. Rod and clean ducts before pulling; use compatible lubricant.
- Pulling: stay below cable rated tension (often 1,500–2,000 N for outside plant); use a swivel and tension gauge; never exceed 20× cable outside diameter bend radius during installation and 10× in service.
- Aerial: ADSS or figure-8; respect span, sag and ground clearance; use dead-end clamps, suspension clamps and armour rods; keep away from power conductors per clearance rules.
- Blown fibre and microduct systems need correct duct fill ratio and air pressure; leave spare ducts and pull cords.
- Record every joint, chamber, slack loop and route deviation as it is built.
Worked example
A duct route is 1,200 m. Specification requires 5% installation slack plus 10 m slack at each of two joint chambers. Cable length = 1,200 × 1.05 + (2 × 10) = 1,260 + 20 = 1,280 m. Order 1,280 m plus drum allowance; do not order exactly 1,200 m.
Traps
- Pulling through a sharp duct bend and exceeding bend radius; loss appears later as macrobend.
- Forgetting joint-chamber slack, then having no fibre to re-splice.
- Using aerial cable in a duct or duct cable on a pole without checking sheath and UV rating.
- Leaving duct ends uncapped so silt and rodents enter.