These are inherent undulations or waves from reel memory as sketched here. While these waves can be minimized, they can t be completely eliminated. Typical displacements of a few inches to a foot increase pulling tension by factors of 3 to 200. Maximizing distance in fiber optic pulling means minimizing duct undulations. 25 inch duct, but at a cost premium.
Plowed duct is straighter than trenched duct.
In fact, pulling cable into open trenched innerduct is not practical. The amount of undulation simply makes pull lengths too short. Duct bends, including undulations, do not limit blowing processes, especially HASB, as much as they do traditional cable pulling. In HASB, the cable is not pulled into the bend by a large pulling force, but rather pushed through the bend by a lower, local air pushing force. This somewhat offsets the effects of bends.