Non-isotropic acoustic cable

Abstract

Embodiments of the present invention address aliasing problems by providing a plurality of discrete acoustic sensors along a cable whereby acoustic signals may be measured in situations where the fiber optic cable has not been secured to a structure or area by a series of clamps. Acoustic sampling points are achieved by selectively enhancing the acoustic coupling between the outer layer and the at least one optical fiber arrangement, such that acoustic energy may be transmitted selectively from the outer layer to the at least one optical fiber arrangement. The resulting regions of acoustic coupling along the cable allow the optical fiber to detect acoustic signals. Regions between the outer layer and the at least one optical fiber arrangement that contain material which is acoustically insulating further this enhancement since acoustic waves are unable to travel through such mediums, or at least travel through such mediums at a reduced rate.