Fiber-tip sensors have proved to be useful for the investigation of ultrasonic signals since they, in principle, overcome some limitations of common piezoelectric hydrophones. A high damage threshold of the sensor is obtained, measurements are not disturbed by electromagnetic influences, and a high temporal and lateral resolution is possible. An optical hydrophone is presented that comprises a fiber tip coated with a dielectric multilayer system of the Fabry–Perot type. The acoustic pressure measurement using the sensor is based on the elastic deformation of the layer system by an incident ultrasonic wave and the detection of the induced change of the optical reflectance. Measurement results obtained by sensors with different layer numbers providing different sensitivities are shown, and the variation of the sensor characteristics depending on the size and shape of the fiber tip is investigated. The appearance of optical loss modulations caused by the stimulation of flexural waves in the fiber in certain measurement configurations is discussed. Several sensor designs are considered to improve the performance of the system in different fields of application, for instance the characterization of lithotripter shock waves, the investigation of cavitation phenomena, and the detection of ultrasound cw signals.