FTTH Installation and Construction Practices
What this domain tests
The construction domain tests code knowledge and physical workmanship: how deep cable is buried, how much conduit it may fill, how tightly it may be bent or pulled, how aerial plant is attached and bonded, and how the drop enters the building. Marks are lost on numeric limits and on code citations.
Standards and codes
- ANSI/TIA-758 for outside-plant optical cable, TIA-568 for premises cabling, TIA-570 for residential.
- NEC Article 770 governs optical fiber cables, listing, and bonding/grounding of conductive strength members and metallic armor at the building entrance.
- NESC rules govern aerial clearances, sag and loading; the local one-call service (811 in the US) must be notified before any excavation.
Burial and conduit
Direct-buried drop and distribution cable is typically placed 0.75–1.0 m deep depending on local code and surface use, with warning tape above it; microtrenching is shallower (roughly 300–450 mm) and needs a hardened cover. Conduit fill is limited to about 40 % of the duct's internal cross-section. Rod and mandrel new ducts before pulling.
Aerial work
Choose ADSS or lashed cable per span and wind/ice loading, set sag to NESC, keep the specified clearance above roads and communications plant, bond and ground metallic members at designated poles, and leave expansion slack.
Pulling and handling
Keep the installed bend radius at 10× cable OD or greater and 20× during a pull. Stay under the manufacturer's tensile rating, use a swivel and tension monitor, and never staple flat drop cable - use clips that do not pinch. Leave slack coils at handholes and about 1 m at the ONT. Firestop and seal every penetration, and keep optical cable separated from power conductors.
Worked example
Three flat drop cables of 5 mm OD go into a 25 mm ID innerduct. Cable area = 3 × π × 2.5² = 58.9 mm²; duct area = π × 12.5² = 490.9 mm²; fill = 12 %, well inside the 40 % limit. Twenty such cables would be 392.7 mm², or 80 % - clearly a violation, so a second duct is required.
Traps
Exceeding bend radius at the wall penetration or ONT; using indoor cable outdoors where UV and water attack the jacket; skipping the locate call; leaving connectors uncapped in dirt; winching without monitoring tension; and omitting bonding/grounding at the entrance.