Fiber rarely goes in the ground bare — it rides inside conduit: continuous HDPE duct that protects the glass, marks the route, and makes tomorrow's upgrade a pull instead of a dig. Conduit choices made on build day echo for fifty years.
The hardware
Outside-plant fiber duct is almost always HDPE — smooth or ribbed-wall, on reels for plowing and boring, typically 1.25″ to 2″ for distribution and up to 6″ for backbone packages. Innerduct subdivides larger conduit so multiple cables share it without friction; microduct bundles many small tubes (each taking a blown micro-cable) in one placement. Orange is the near-universal communications color, with tracer wire or toneable duct placed so locators can find non-metallic runs — the quiet hero of damage prevention.
Placed how
Duct is plowed, trenched, or pulled back through a bore in continuous fused or coupled runs between vaults and handholes. After placement it's proofed with a mandrel, pull tape installed, and capped — an empty, proven, documented pathway waiting for glass.
Why spare conduit is the cheapest bet in construction
The machine crossing your site costs the same whether it places one duct or three; the marginal duct is nearly free, and the dig it prevents later costs thousands per foot of disruption. Every dig-once policy, every joint-trench build, and every developer who's been through one street reconstruction reaches the same conclusion: place the spare duct. Then record where it is — undocumented conduit is buried money nobody can find.