Over the past decade there has been considerable interest in using fiber-optic sensors for a variety of applications. One area which has attracted substantial attention is the use of these sensors for underwater acoustic arrays. In this paper the fundamental noise performance of these sensors will be discussed. The primary focus will be the noise associated with the transducer itself; however, attention will be paid to the noise associated with the interrogation and multiplexing of these sensors. Transducer noise is usually determined by the thermal noise associated with the structure to which the sensing fiber is attached and the intrinsic thermal noise of the fiber itself. The noise associated with the interrogation of these sensors is usually associated with the characteristics of the optical source. In many systems noise generated by frequency, amplitude, and polarization modulation of the light as it passes through the telemetry cable will also limit the systems noise performance. Consequently, ultimate system noise is a complex trade-off of many parameters and can lead to different solutions for particular applications.