common path frequency domain optical coherence reflectometry / tomography devices include a portion of optical fiber with predetermined optical properties adapted for producing two eigen modes of the optical radiation propagating therethrough with a predetermined optical path length difference . the two replicas of the optical radiation outgoing from the portion of the optical fiber are then delivered to an associated sample by an optical fiber probe . the tip of the optical fiber serves as a reference reflector and also serves as a combining element that produces a combination optical radiation by combining an optical radiation returning from the associated sample with a reference optical radiation reflected from the reference reflector . the topology of the devices allows for registering a cross - polarized or a parallel - polarized component of the optical radiation reflected or backscattered from the associated sample . having the optical path length difference for the two eigen modes of the optical radiation differ from the reference offset in the devices of the present invention allows for relieving the requirements to the spectral resolution of the fd oct engine and / or data acquisition and processing system , and substantially eliminates depth ambiguity problems .