47 specifies 18 inches as the minimum depth for direct burial of network-powered broadband communication systems, which includes fiber optic cables. However, this represents the absolute minimum, and most professional installations exceed this requirement. The short answer, based on general industry standards and the National Electrical Code (NEC), is that fiber optic cable is typically buried between 24 inches (60 cm) and 30 inches (76 cm) deep. However, simply hitting this depth isn't enough to guarantee your network survives. What are underground fiber optic cable installation standards? What is the minimum burial. eCFR :: 7 CFR 1755. 903 -- Fiber optic service entrance cables. Title 7 was last amended 5/08/2026.