Cable blowing uses compressed air to push a micro cable through a microduct. The cable is fed by a blowing head that combines mechanical pushing with airflow, so it travels through bends and long runs without being pulled.
The result depends on three things: the duct, the cable and the machine. A low-friction inner layer, a cable of the right diameter and stiffness, and correctly set pressure and speed together allow runs well beyond what pulling could achieve.
Blowing also makes later upgrades practical. Additional cables can be installed in spare ducts without reopening the trench, which is why microduct routes are planned with spare capacity from the start.