Conduit installation: Fiber cable is pulled through rigid or flexible conduit (PVC, HDPE, RMC) in a trench, on cable tray, or in underground duct banks. This guide provides a side-by-side comparison and explains when each method is appropriate. Installing fiber underground is one of the most durable ways to protect a network's backbone — when it's done right. But because the cable sits in soil exposed to. Direct burial fiber optic installation eliminates conduit cost but demands the right cable construction, proper bedding, and precise depth to meet NEC and Telcordia GR-20 requirements. This article covers cable selection, trench preparation, tracer wire, warning tape, road crossings, and. ion) and “ Installed” (after installation). Split cable guides and split 40-in. 1.