Premises cabling and communications cabling
Premises cabling questions test whether you can apply structured-cabling standards inside a building: backbone versus horizontal, media and connector selection, fire ratings, color coding, and labeling. Fiber is common in backbone, riser, and long horizontal runs, so the exam expects TIA-568 and NEC terminology rather than ad hoc wiring.
Structure and standards
TIA-568 defines commercial-building cabling: entrance facility, equipment room, backbone, horizontal, and work area. TIA-606 covers administration/labeling; TIA-607 covers grounding and bonding. Fiber backbone connects entrance/equipment rooms to intermediate distribution frames; horizontal fiber is used where copper's 100 m channel is insufficient or EMI/security demands it. NEC Article 770 governs optical fiber cable, and listed cable ratings matter: OFNP plenum, OFNR riser, OFN general-purpose. Use plenum cable in air-handling spaces and riser-rated cable in vertical shafts; never substitute without code approval.
Media and connectors
OM3/OM4 multimode suits 850 nm VCSEL links; OS2 singlemode suits long runs and 1310/1550 nm optics. 10GBASE-SR reaches about 300 m on OM3 and 400 m on OM4; 10GBASE-LR reaches 10 km on OS2. LC is the dominant small-form-factor connector; SC is common in older and singlemode plants; ST is legacy. APC ferrules are angled and must not be mated to UPC. TIA-598 color code: OS2 yellow, OM1/OM2 orange, OM3/OM4 aqua (OM4 may be violet), OM5 lime. Label both ends with unique identifiers and record them.
Worked example
A 350 m indoor 10 Gbps backbone link is proposed. 10GBASE-SR is specified. OM3 is rated to 300 m, so it fails the distance requirement; OM4 reaches 400 m and passes, but OS2 with 10GBASE-LR also passes with far more headroom. Choose OM4 if SR electronics and cost dominate; choose OS2 if future 40/100G or longer runs dominate. The decision must be documented, not left to the installer.
Traps
Using OM3 for a 350–400 m SR link; confusing orange OM2 with aqua OM3/OM4; installing OFNR in a plenum; mixing APC/UPC; and omitting TIA-606 labels. Also watch for fiber counts that ignore spare capacity.