Focal plane wavefront sensing is an appealing technique to cophase multiple aperture telescopes. Phase diversity (PD), operable with any aperture configuration or source extension, generally suffers from high computing load. We introduce, characterize, and experimentally validate the linearized analytical phase diversity (LAPD) algorithm, based on a fast linearized PD algorithm with a capture range comparable to classic PD. We demonstrate that a typical performance of λ  /  75  RMS wavefront error can be reached.