A fiber optic filter edge detector of Doppler shifted light comprises: a laser source for emitting pulsed laser light substantially over a first fiber optic path; an optical lens for directing laser light emitted from the first fiber optic path to free-space and for receiving laser light returns from free-space and focusing the laser light returns to the first fiber optic path; an edge filter optical element fiber coupled to the first fiber optic path for receiving the laser light returns, the edge filter optical element operative to transmit a first portion of the laser light returns through a second fiber optic path and to reflect a second portion of the laser light returns through a third fiber optic path; and at least one light detector optically coupled to the second and third fiber optic paths.