Multiple realities
(covers information from several alternate timelines)
A subspace field pulse was a process used in Geordi La Forge's VISOR.
In 2370, Lieutenant Worf was thrown into a state of quantum flux as a result of an encounter with a quantum fissure, causing him to enter a different quantum reality. The quantum flux in Worf's cellular RNA was intensified by the field pulse in La Forge's VISOR whenever he came in close proximity to La Forge, causing him to shift to a different quantum universe each time. (TNG: "Parallels")