DIN 18220 - Method for laying pipes for fiber optic lines in which narrow trenches (trench) and slots are made in soils and asphalt in a minimally invasive manner using diamond grinding technology. Underground cables are pulled in conduit that is buried underground, usually 1-1. 2 meters (3-4 feet) deep to reduce the likelihood of accidentally being dug up. FO-VC2 JOINT USE - VERICAL MIDSPAN CLEARANCES 48. (FOA) was founded in 1995 to help develop the workforce to build the fiber optic networks to support a rapid expansion in communications and the Internet. This alternative laying technique enables.