A hydrophone or other acoustic vibration sensing apparatus having a disk circumferentially supported for flexure induced by acoustic vibrations and wound on each side with a flat spiral of optical fiber fixedly attached to the disk side so that flexure of the disk due to the vibrations lengthens the spiral on one side and shortens the spiral on the other side. The spirals are connected as two legs of a fiber optic interferometer to provide an output corresponding to the vibrations while canceling errors due to pressure and temperature effects common to the legs. A pair of the disks and associated optical fiber spirals may be mounted on opposite ends of a body with the outer spirals connected as one interferometer leg and the inner spirals as another leg to cancel differences in the lengths of the legs due to acceleration induced flexure of the disks and to provide double the sensitivity to pressure differential of a single disk.